the Symposium on Wheats for More Tropical Environments - cimmyt

The International Maize and Wheat Improvement Center (CIMMYT) is an internationallyfunded, nonprofit scientific research and training organization. Headquartered in Mexico.CIMMYT is engaged in a worldwide research program for maize, wheat and triticale. wi<strong>the</strong>mphasis on food production in developing countries. CIMMYT is one of 13 nonprofitinternational agricultural research and training centers supported by <strong>the</strong> ConsultativeGroup for International Agricultural Research (CGIAR). The CGIAR is sponsored by <strong>the</strong> Foodand Agriculture Organization (FAO) of <strong>the</strong> United Nations. <strong>the</strong> International Bank forReconstruction and Development (World Bank), and <strong>the</strong> United Nations DevelopmentProgramme (UNDP). The CGIAR consists of 40 donor countries. international and regionalorganizations. and private foundations.CIMMYT receives support through <strong>the</strong> CGIAR from a number of sources. including <strong>the</strong>international aid agencies of Australia. Brazil, Canada. China, Denmark, Federal Republic ofGermany. France. India. Ireland. Italy, Japan, Mexico. <strong>the</strong> Ne<strong>the</strong>rlands. Norway. <strong>the</strong>Philippines, Spain, Switzerland. United Kingdom and <strong>the</strong> USA. and from <strong>the</strong> EuropeanEconomic Commission. Ford Foundation, Inter-American Development Bank. InternationalBank for Reconstruction and Development. International Development Research Centre.OPEC Fund for International Development, Rockefeller Foundation. and <strong>the</strong> United NationsDevelopment Programme. ResPonsibility for this publication rests solely with CIMMYT.Correct Citatton: Wheats for More Tropical Environments, A Proceedings of <strong>the</strong>International <strong>Symposium</strong>. CIMMYT 1985.

Wheats for MoreTropical EnvironmentsA Proceedings of <strong>the</strong> International <strong>Symposium</strong>: September 24-28, 1984 Mexico, D. F.: Sponsored by: The United Nations Development Programme and CIMMYT

3AcknowledgementsThe Tropical Wheat <strong>Symposium</strong> is <strong>the</strong>result of <strong>the</strong> interest and efforts ofmany people. and I greatly appreciate<strong>the</strong>ir help and cooperation. First. Iwould like to acknowledge <strong>the</strong> follOWinggroups and individuals for <strong>the</strong>ir help incontributing to <strong>the</strong> success of <strong>the</strong>symposium: for funding <strong>the</strong>symposium. The United NationsDevelopment Programme (UNDP).especially Mr. William Mashler for hisenthusiasm and support of <strong>the</strong> project;<strong>the</strong> directing staff of CIMMYT for givingme <strong>the</strong> opportunity to carry out such aproject; <strong>the</strong> CIM~T Wheat OutreachStaff for <strong>the</strong>ir active participation andidentification of participants; <strong>the</strong>participants. without whom <strong>the</strong>re couldhave been no symposium; LindaAinsworth and <strong>the</strong> staff of VisitorServices for <strong>the</strong>ir help in coordinating<strong>the</strong> activities of <strong>the</strong> symposium;Griselda Marquez. for her tireless effortsin coordinating all of <strong>the</strong> secretarialwork; Elsa Caballero and <strong>the</strong> TravelOffice for <strong>the</strong>ir effiCient travelarrangements for <strong>the</strong> participants. andRaul Martinez and his staff of <strong>the</strong>Camino Real Hotel for <strong>the</strong> excellentaccomodations and services renderedduring <strong>the</strong> symposium.Special thanks also go to <strong>the</strong> followingpeople for <strong>the</strong>ir help in <strong>the</strong> developmentof <strong>the</strong>se proceedings of <strong>the</strong> symposium:my co-editors Arthur Klatt. for hiscareful review of <strong>the</strong> manuscripts. andElizabeth Cuellar. whose languageexpertise and excellent spirits ensured<strong>the</strong> timely completion of thispublication; Sanjaya Rajaram. for hisreview of selected manuscripts; <strong>the</strong> staffof <strong>the</strong> CIMMYT CommunicationsGroup. especially Tiff Harris for hisadvice. design support andencouragement; Silvia Bistrain. BerthaRegalado. Maricela A. de Ramos andPatricia Martinez for typesetting <strong>the</strong>proceedings. and Miguel Mellado. RafaelDe la Colina and Jose Manuel Fouillouxfor design and layout.Finally. a special note of appreciation tomy wife Ruth and our children. Robinand Rinelle Mae. for <strong>the</strong>ir patience.understanding and love while this workwas going on.Reynaldo L. Villareal<strong>Symposium</strong> Organizer

4Table of Contents1Preface 92Welcome to <strong>the</strong> <strong>Symposium</strong> on Wheats for More Tropical 10Environments, R.D. Havener, Director General, CIMMYT.Mexico3Keynote address: Wheats for More Tropical Environments, 14W.T. Mashler, Senior Director. Division for Global and Inter~regional Projects. United Nations Development Programme4Introduction to <strong>the</strong> <strong>Symposium</strong>, A.R. Klatt. Associate Director. 21Wheat Program. CIMMYT. Mexico5Country Reports 24Selecting and Introducing Wheats for <strong>the</strong> Environments of <strong>the</strong> Tropics. C.E. 24Mann. Wheat Program, CIMMYT. Bangkok. ThailandWheat Breeding in Nor<strong>the</strong>ast Argentina. I.R. Cettour. Chaco. and J.E. Nissi. 34Cordoba. Instituto Nacional de Tecnologia Agropecuaria. ArgentinaWheat Research Efforts in <strong>the</strong> Abapo-Izozog Region of Bolivia. J.E. Abela. 38Corporacion Gestora del Proyecto Abapo-Izozog. Santa Cruz, BoliviaWheat Production in <strong>the</strong> Subtropical Areas of Santa Cruz. Bolivia. C. QUintana. 42Centro de Investigacion Agricola Tropical. Santa Cruz. BoliviaWheat in Costa Rica. C.A. Salas. Estacion Experimental Fabio Baudrit Moreno. 46Universidad de Costa Rica. Alajuela. Costa RicaWheat Research in <strong>the</strong> Coastal Region of Ecuador. J. Tola. Small Grains 51Program. Instituto Nacional de Investigaciones Agropecuarias. Quito.EcuadorSelection and Introduction of Wheat Types for Subtropical Conditions in Mexico. 54J.J. Martinez. Wheat Research Program, Centro de Investigaciones Agricolasdel Noroeste-INIA. Ciudad Obregon. Sonora, MexicoWheat Production Status. Constraints and Research Priorities in Nigeria. 56A.M. Falaki. Institute for Agricultural Research. Ahmadu Bello University.Zaria. NigeriaPage

5Wheat Production in Bangladesh: Its Constraints and Research Priorities. 59A.B.S. Hossain. Bangladesh Agricultural Research Institute. Joydebpur.Dhaka. BangladeshWheat Improvement Programs for <strong>the</strong> Hotter Parts of India. J.P. Tandon. Wheat 63Program. Indian Agricultural Research Institute. New Delhi. IndiaWheat Research and Production in Pakistan. M.A. Bajwa. Ayub Agricultural 68Research Institute. Faisalabad. PakistanProduction Constraints and Research Priorities in <strong>the</strong> Sou<strong>the</strong>rn Winter Wheat 72Region of China. C.F. Zhou. Institute of Food Crops. Jiangsu Academy ofAgricultural Sciences. Nanjing. Jiangsu. ChinaWheat Production Constraints and Research Priorities in Indonesia. 78T. Danakusuma. Sukamandi Food Crops Research Institute. Cikampek.Sukamandi. IndonesiaWheat GrOWing in <strong>the</strong> Philippines. C.R Escafto. Crops Research Department. 81Philippine Council for Agriculture and Resources Research and Development.Los Banos. PhilippinesThailand Winter Cereals Program. P. Chandhanamutta. Rice Research Institute. 83Katsetsart University. Bangkok. ThailandDryland Wheat Production in <strong>the</strong> Subtropics of gueensland. Australia. 86D.R Woodruff. Queensland Wheat Research Institute. Toowoomba.Queensland. Australia6Contributed Papers 89I. BreedingBreeding Wheat for More Tropical Environments at CIMMYT. RL. Villareal. 89S. Rajaram and W. Nelson. Wheat Program. CIMMYT. MexicoWheat Germplasm Development for Heat and Drought Tolerance for Nigeria. 100F.C. Orakwue. Institute for Agricultural Research. Ahmadu Bello University.Zaria. NigeriaBreedtng Wheats for Heat and Drought Tolerance in Central India. 107Y.M. Upadhyaya and K.N. Ruwali. Indian Agricultural Research Institute.Indore. Madhya Pradesh. IndiaIdentifying Wheats Adapted to More Tropical Areas of <strong>the</strong> Sou<strong>the</strong>rn Cone of 111South America. M.M. Kohli. Wheat Program. CIMMYT. Santiago. ChileWheat Breeding in Rio Grande do SuI. Brazil. O. de Sousa Rosa. Centro Nacional 116de Pesquisa de Trigo. Passo Fundo. Rio Grande do Sui. BrazilBreeding and Disease Problems Confronting <strong>the</strong> Successful Cultivation of Wheat 122in <strong>the</strong> Cerrados of Brazil. A.R da Silva. Ministerio de Agricultura. ProvarseasNational. Brasilia. D.F.. Brazil

6Screening Wheats for Quality. A. Amaya. Industrial Quality Laboratory. Wheat 125Program. CIMMYT. MexicoWide Crosses and New Genes for Wheats for <strong>the</strong> Tropics. A. MUjeeb-Kazi. Wheat 127Wide Cross Program. CIMMYT. MexicoWheat in West Africa. G. Varughese. Wheat Program, CIMMYT. Mexico 130Wheat Varietal Development Strategy in Bangladesh, L. Butler, Wheat Program. 132CIMMYT. Joydebpur. Dhaka. BangladeshII. Diseases and Disease Control 135Breeding Wheats for Resistance to Spot Blotch, Y.R. Mehta. Instituto 135Agronomico do Parana, Londrina, Parana. BrazilBreeding Wheats with Resistance to Helmtnthosporium sattvum in Zambia. 145R. Raemaekers. Belgian Development Cooperation, Mount Makulu ResearchStation. Chilanga, ZambiaCIMMYT Methods for Screening Wheat for Helminthosportum sattvum 149Resistance. L.I. Gilchrist. Wheat Program. CIMMYT. MeXicoInsect Pests and Diseases of Wheat in <strong>the</strong> Philippines. D.B. Lapis, Institute for 152Plant Breeding. University of <strong>the</strong> Philippines. Los Baflos. PhilippinesThe Effect of Early Foliar Infection by Helminthosportum sattvum on Some 154Yield Components of Two African Wheats. W.A.J. de Milliano. WheatProgram. CIMMYT. Mexico. and J.C. Zadocs. Department of Phytopathology,Agricultural University. Wagenin~en, Ne<strong>the</strong>rlandsWheat Breeding for Scab Resistance. G.C. Luzzardi. Faculdade de Agronomia 158El1seu Maciel. Universidade Federal de Pelotas. Pelotas. BrazilHead Scab Screening Methods Used at CIMMYT. G.T. Bekele. Wheat Program. 169CIMMYT. MexicoRecent Advances in Research on Wheat Scab in China. Z.Z. Liu. Plant 174Protection Institute. Shanghai Academy of Agricultural Sciences. Shanghai,People's Republic of ChinaReflections on Foot Rots of Wheat in Warmer. Nontraditional Wheat-Growing 182Climates. H.J. Dubin, Wheat Program. CIMMYT. QUito, EcuadorA Review of Major Wheat Diseases in Tropical Environments. J.M. Prescott. 186Wheat Program. CIMMYT. MexicoDistribution and Importance of Root Rot Diseases of Wheat. Barley and Triticale 189in South and Sou<strong>the</strong>ast Asia, E.E. saarI. Wheat Program. CIMMYT. MexicoChemical Control Measures for <strong>the</strong> Major Diseases of Wheat, with Special 196Attention to Spot Blotch, Y.R. Mehta and S. Igarashi. Instituto Agronomico doParana. Londrina. Parana. Brazil

7Chemical Control ofHelmtn.thosportum sativum on Rainfed Wheat in Zambia. 201R Raemaekers, Belgian Development Cooperation. Mount Makulu ResearchStation. Chilanga. ZambiaChemical Control of Wheat Diseases in <strong>the</strong> Philippines. D.B. Lapis, Institute for 204Plant Breeding. University of <strong>the</strong> Philippines. Los Banos, PhilippinesUI. Agronomy 209Physiological Limitations to Producing Wheat in Semitropical and Tropical 209Environments and Possible Selection Criteria. RA. Fischer. Division of PlantIndustry. Commonwealth Scientific and Industrial Research Organization.Canberra. AustraliaSoil Management as an Alternative for Minimizing Environmental Constraints 231for Wheat Production in <strong>the</strong> Semitropical Areas of Brazil. O. Muzilli. InstitutoAgronomico do Parana. Londrtna. Parana. BrazilThe Cerrados: Future Wheat Production Prospects and Limitations. 239M.A. McMahon. Wheat Program. CIMMYT. Santiago. Chile. and W.J. Goedert.Empresa Brasileira de Pesquisa Agropecuaria. Planaltina. D.F.. BrazilAlleviating <strong>the</strong> Constraints of Acid Soils on Rainfed Wheat in Zambia. R Little. 250Zambia-Canada Wheat Research Project. Mt. Makulu Research Station.Chilanga. ZambiaWheat Production Constraints and Management in Bangladesh. M. GuIer, Wheat 257Program. CIMMYT. Joydebpur. Dhaka. BangladeshAgronomic Management Issues for Wheat Production in More Tropical 260Environments ofSou<strong>the</strong>ast Asia, D.A. Saunders. Wheat Program. CIMMYT.Bangkok. ThailandWheat in Rice-Based Cropping Systems in Thailand. K. Rerkasem and 265B. Rerkasem, Multiple Cropping Project. Chiang Mai University. Chiang Mai,ThailandAgronomic Practices and Problems for Wheat FollOWing Cotton and Rice in 273Pakistan. P.R Hobbs. Wheat Program. CIMMYT. Islamabad. PakistanRice-Wheat Cropping Systems in South and Sou<strong>the</strong>ast Asia. V.R Carangal, 277Asian Cropping Systems Network. International Rice Research Institute,Manila. PhilippinesSimple Simulation Models for Agronomic Research. W.A.J. de Milliano. Wheat 286Program. CIMMYT. Mexico. and H. van Keulen. Centre for World FoodStudies. Wageningen. Ne<strong>the</strong>rlandsIV. Seed 291Wheat Seed Production. Storage and Distribution in Bangladesh. S.M. Ahmed. 291Bangladesh Agricultural Research Institute. Joydebpur. Dhaka, Bangladesh

8Production. Storage and Marketing of Wheat Seed in India, S.B. Singh. 297U.P. Seeds and Tarai Development Corporation. Haldi IPatnagar). Nainital,IndiaV.EcODODUC8 303Wheat in <strong>the</strong> Tropics: Economic and Policy Issues, D. Byerlee. Economics 303Program, CIMMYT. Islamabad. PakistanWheat in Chiang Rai. Thailand: A Preliminary Look at Comparative Advantage. 316L.W. Harrington, Economics Program, CIMMYT. and S. Sat-thapom. Ministryof Agriculture and Cooperatives. Bangkok, ThailandThe Local-Use Approach to <strong>the</strong> Introduction of Wheat in a Nonproducing 321Country: Thailand. J.G. Connell, Local Utilization Program. Sou<strong>the</strong>ast AsianRegional Wheat Program-CIMMYT. Bangkok. ThailandProblems and Benefits of Reintroducing Wheat into <strong>the</strong> Philippines, A.V. Rotor, 324National Food Authority, Manila. PhilippinesThe Relative Priority and Economics of Growing Wheat in Nigeria. 327A.O. Ogungbile, Institute for Agricultural Research. Ahmadu BelloUniversity. Zaria. NigeriaSocioeconomic and Agroeconomic Implications of Growing Wheat in Sudan. 332F.M. Ali, Agricultural Research Corporation. Wad Medani, SudanComments. D.L. Winkelmann. Director. Economics Program, CIMMYT. Mexico 3397Closing Remarks, B.C. Curtis. Director. Wheat Program. CIMMYT. 341Me:dco8Appendiz I 346Comments on <strong>the</strong> <strong>Symposium</strong> on Wheats for More Tropical Environments. O. de 346Sousa Rosa. Centro Nacional de Pesquisa de Trigo. Passe Fundo, Rio Grandedo SuI. BrazilAppendiz U 347Wheat Pests and Diseases, W.C. James. Deputy Director General. CIMMYT, Mexico 347Appendiz m 349Participants. <strong>Symposium</strong> on Wheats for More Tropical Environments 349

1 9PrefaceThe international workshop onWheats for More TropicalEnvironments was held in MexicoCity September 24-28. 1984. Thiswas <strong>the</strong> first attempt to bringtoge<strong>the</strong>r wheat scientists from allover <strong>the</strong> world to search for solutionsto <strong>the</strong> problems which face farmersin more tropical areas who seek togrow wheat outside of its traditionalenvironments.As a result of growing urbanpopulations and rising incomes in<strong>the</strong> tropics. bread is becoming astaple food for more and morepeople. For many developingnations. this has led to an increaseddependency on wheat imports and<strong>the</strong> accompanying foreign exchangedrain.In answer to a request by <strong>the</strong> CGIARto look for ways to decrease thisdependency, CIMMYT. with <strong>the</strong>assistance of <strong>the</strong> United NationsDevelopment Programme (UNDP).has begun emphasizing <strong>the</strong>development of wheats adapted to<strong>the</strong> stress conditions of <strong>the</strong> moretropical environments.It is hoped that this workshop willlead to an increased participation incollaborative research efforts on <strong>the</strong>part of wheat scientists from manycountries so that. by workingtoge<strong>the</strong>r. one more battle may bewon in <strong>the</strong> war on hunger.Reynaldo L. VUlarealArthur R. KlattTechnical Editors

2 _Welcome to <strong>the</strong><strong>Symposium</strong> on Wheats forMore Tropical EnvironmentsR.D. Havener. Director General.CIMMYT. MexicoIt is my privilege to welcome you tothis, <strong>the</strong> first symposium whichCIMMYT is holding to focus on <strong>the</strong>problems related to increasing <strong>the</strong>production of wheat in more tropicaland nontraditional productionenvironments. I would like to thankboth Rey Villareal, chairman of <strong>the</strong>symposium, and Art Klatt on behalf ofCIMMYT. Before introducing ourkeynote speaker, let me share a fewthoughts with you to set a frameworkfor what I hope you will be talkingabout dUring <strong>the</strong> balance of thisconference.CIMMYT, whose headquarters is at EISatan. about 45 km from Mexico City,is <strong>the</strong> hub of an international networkof which many of you are partners.CIMMYT itself is a very smallorganization. Within our wheat. maize,economics and support programs. even<strong>the</strong> largest programs, wheat and maize.each have only about 35 scientistsworking on a global basis. Only byacting as <strong>the</strong> hub of an internationalnetwork can we accomplish very much.CIMMYT is a part ofan internationalorganization of agricultural researchcenters supported by <strong>the</strong> ConsultativeGroup on International AgriculturalResearch (CGIAR). The CGIAR iscomposed of a group of approximately40 donors that support <strong>the</strong>se centerslocated across <strong>the</strong> tropical andsubtropical world. Included are CIATand CIP in Latin America, IFPRI inWashington, D.C., USA. and ISNAR, <strong>the</strong>International Service for NationalAgricultural Research in <strong>the</strong>Ne<strong>the</strong>rlands. IBPGR, <strong>the</strong> gene board, islocated at FAa headquarters in Rome.O<strong>the</strong>r crop and livestock centers inAfrica include WARDA, <strong>the</strong> West AfricaRice Development Association, liTA,<strong>the</strong> International Institute of TropicalAgriculture in Nigeria. and ILCA andILRAD, <strong>the</strong> livestock centers in Ethiopiaand Kenya in East Africa. ICARDA, in<strong>the</strong> Middle East. works with drylandfarming systems for <strong>the</strong> semi-aridregions having a Mediterranean-typeclimate, and ICRISAT is in India, whichhas similar climatic zones. but withsummer rainfall patterns and tropicalclimates. Then <strong>the</strong>re is IRRI, <strong>the</strong>International Rice Research Institute in<strong>the</strong> Philippines. These13 centers comprise <strong>the</strong> internationalnetwork supported by <strong>the</strong> CGIAR.The peasant farm family about whichwe will be talking a great deal in <strong>the</strong>next few days is <strong>the</strong> target group for us.<strong>the</strong> international centers; <strong>the</strong>y arehowever. not our client group. You. <strong>the</strong>national agricultural researchprograms, <strong>the</strong> national agriculturaluniversities, those national institutionsworking for <strong>the</strong> welfare of developingcountryfarm families, are in fact ourclient group. <strong>the</strong> ones with whom wework. You, in turn, work with <strong>the</strong>farmers who actually produce <strong>the</strong> cropsaround <strong>the</strong> world.Here at CIMMYT, we work principallyon five experiment stations, Poza Ricaon <strong>the</strong> coast at 60 meters of elevation in<strong>the</strong> hot. humid tropics. Tlaltizpan. amid-elevation station at 1000 melevation, EI Satan at 2250 m elevation,

uToluca, a high-elevation station at2650 m and Ciudad Obregon (CIANO)in <strong>the</strong> Sonora desert at 40 m. CIANO isowned and operated principally by <strong>the</strong>government of Mexico, which hasallocated to CIMMYT 175 hectares ofland in an irrigated valley for acooperative wheat-improvementprogram. Within <strong>the</strong>se stations we cantypify most of <strong>the</strong> agroclimatic zones inwhich wheat and maize are grownaround <strong>the</strong> world.CIMMYT's products are germplasm,research procedures, trained personnel.information and consulting services.We have global testing networks ofwhich you are a part or, at least, now asubpart dealing with <strong>the</strong> tropicalgermplasm of <strong>the</strong> wheat program.International testing is important forgermplasm development, and it isimportant in <strong>the</strong> mechanism ofgermplasm distribution to ourcollaborators around <strong>the</strong> globe. Dealingwith both wheat and maize areapproXimately 125 nationalgovernments in <strong>the</strong> germplasmexchangeprogram.At CIMMYT, we have had in-servicetrainees or visiting scientists fromvirtually every country in <strong>the</strong> worldwhere wheat and maize are importantcrops. In this hemisphere, we haveregional programs in Mexico, CentralAmerica and <strong>the</strong> Caribbean, and <strong>the</strong>Andean Region and Sou<strong>the</strong>rn Cone ofSouth America. We work in West andNorth Mrica, in <strong>the</strong> areas that are nowclassified as East and sou<strong>the</strong>rn Mricaand in <strong>the</strong> ICARDA zone of nor<strong>the</strong>rnMrtca and <strong>the</strong> Middle East. We alsohave programs in South and Sou<strong>the</strong>astAsia. In each of those locations, wehave regional offices and/or regionalstaff posted to serve <strong>the</strong> nationalprograms. They conduct workshops,circulate regional nurseries, exchangeresearch data, expand trainingopportunities, support on-farm researchactivities and, we hope, improveconsulting services.Depending on <strong>the</strong> needs of particularcountries, we now have assigned staffwith special-project funding in Haiti,Peru, Ghana, Bangladesh, Pakistan andTurkey, working in national wheat ormaize improvement programs. Underconsideration are national programswith extra-core special project fundingin Ethiopia and Kenya.How are we doing? When one looks atwheat production on a global basis, <strong>the</strong>answer Is pretty well. Comparing <strong>the</strong>1979-81 period to 1969-71, <strong>the</strong>worldwide annual rate of increase inwheat yield has been 3.4%: <strong>the</strong> annualincrease in total production has been4.8%. Looking at selected individualcountries, <strong>the</strong> growth in wheatproduction and yield has been quitespectacular: here in Mexico <strong>the</strong>re hasbeen a compound growth rateapproaching 5% annually during <strong>the</strong>past 20 years. There have been peaksand valleys, depending on governmentpolicies, availability of water andseasonal variations, but <strong>the</strong> trendcontinues to go up. In 1983-84, it Ispredicted that It will go even higher.In India, an average of 10.5 million tonsof wheat were harvested from 1961 to1965. For 1984, <strong>the</strong> harvest Is reportedto be in <strong>the</strong> neighborhood of 45 m1lliontons. There Is a similar story inPakistan and also in Turkey. In Turkey,<strong>the</strong> increase in production has comeabout as a result of improved farmingpractices and farming systems ra<strong>the</strong>rthan through <strong>the</strong> use of improvedgenetic materials; it has been basedlargely on· better dryland farmingpractices, espec1al1y on <strong>the</strong> Anatolianplateau.

12In Argentina, <strong>the</strong>re have been ups anddowns, principally depending ongovernment pricing policies. but <strong>the</strong>upward trend in production has beenvery strong and <strong>the</strong>re is every reason tobelieve that, in <strong>the</strong> next few years. itwill increase even more rapidly.The real success story in wheat hasbeen in Bangladesh. It has gone from asmall wheat-production area in 1961-65to a production of over one million tonstoday. This has occurred withtechnology that was co-generated byCIMMYT and <strong>the</strong> Government of India.and imported into Bangladesh andapplied to <strong>the</strong> fields of former riceproducers. It is a story of anextraordinary take-off in wheatproduction.There are. however. problem areas in<strong>the</strong> world where wheat production hasnot increased. These areas are mainlyin <strong>the</strong> Middle East and Mrica. where<strong>the</strong>re has been a downward trend in percapita production.CIMMYT wheats are now planted onapproximately 40 million hectares indeveloping countries and ano<strong>the</strong>r 10million in developed countries. Whenwe say CIMMYT. we are referring tothis network of some 2.500 scientistsscattered around <strong>the</strong> world. These 50million hectares may have alreadyexpanded to 60 or even 65 million; at<strong>the</strong> moment we are trying to get newfigures on <strong>the</strong> area under wheat cropsthat bear CIMMYT germplasm. Tenmillion tons of grain may be added to<strong>the</strong> world's food supply annually. justfrom <strong>the</strong> effect of <strong>the</strong>se varieties.Looking briefly at maize. <strong>the</strong>re hasbeen a similar success story in <strong>the</strong>1969-71 to 1979-81 period. There havebeen significant increases in yielddUring <strong>the</strong> decade. The developedcountries had made big increasesdUring <strong>the</strong> 1959-61 to 1969-71 decadebut. with <strong>the</strong> developing countriescatching up. an even more surprisingpercentage increase in total productiontook place this last decade.We reckon that some 3 million hectaresof land are now under improved maizevarieties coming out of <strong>the</strong> CIMMYTnetwork. with some 90 million dollarsin value added each year. But. hereagain, <strong>the</strong>re are regional discrepancies.While Latin America had an increase inproduction of 2.4% annually dUring <strong>the</strong>last decade. Mrica has not kept pacewith <strong>the</strong> rate of population growth. Theincrease in <strong>the</strong> Middle East has beengreater than <strong>the</strong> rate of populationgrowth. and Asia has made some realgains in per capita availability of maize.Much of CIMMYT's effort continues tobe on improving <strong>the</strong> genetic yieldpotential. but even more effort is nowgoing into increasing yielddependability under environmentalstress conditions. That is why you arehere this week. We are trying to close<strong>the</strong> gap between potential yields andthose on farmers' fields. This is <strong>the</strong>reason that <strong>the</strong> emphasis on on-farmresearch and production agronomy hasbecome a much more substantial partof our program in <strong>the</strong> last few years.The biggest problem we face ispopulation growth, with which you arefamiliar. When I was born. <strong>the</strong>population of <strong>the</strong> world was less than 2billion people. If I live my three scoreand seven years. <strong>the</strong> population by <strong>the</strong>end of my life time will exceed 6.5billion. This is what can happen to <strong>the</strong>population of <strong>the</strong> world Within <strong>the</strong>space of one man's life. This Is <strong>the</strong>challenge that faces us in <strong>the</strong> yearsahead. and this is where ouropportunity lies.

13In Bangladesh. many farmers' fieldspreviously produced less than one-halfton of dryland rice per hectare per yearin rotation with <strong>the</strong> main rice crop. In1984. that same land produced in <strong>the</strong>neighborhood of 2.5 tons of wheatunder similar conditions and withsimilar irrigation schedules. This typeof progress gives us hope for being ableto meet <strong>the</strong> needs of <strong>the</strong> populationchallenge.In a recent publication. Derek Byerleereported that. in 1981-82. worldwidewheat imports exceeded 100 milliontons for <strong>the</strong> first time. That is animmense amount of wheat being tradedto feed <strong>the</strong> world's people. Perhapsmore disturbingly. 61 million of those100 million tons were going fromdeveloped countries to developingcountries: much of it was going to <strong>the</strong>recently emerging developing-countrymarket economies to sustain domesticfood supplies. Twenty years ago most of<strong>the</strong> trade was between developedcountries. from <strong>the</strong> United States andCanada to Europe and Russia. Now 27developing countries. many of whomare represented here today. areimporting more than 500.000 tons ofwheat per year to sustain domestic foodsupplies: 17 of those 27 are importingmore than a million tons.CGIAR asked CIMMYT to put moreemphasis on developing wheats formore tropical environments. CIMMYTmanagement. <strong>the</strong>n,as now. agreed thatthis was an important challenge. Itwould. however, be a long-term project.and progress would be slow. It is easierto increase production in goodproduction environments than it is inpoor production environments. and<strong>the</strong>re was still an immense challengefor increasing yields in <strong>the</strong> betterenvironments. Therefore. CIMMYT wasnot sure how much of its resourcesshould be diverted toward <strong>the</strong> moretropical. more difficult productionenvironments. We suggested that. if <strong>the</strong>CGIAR could prOVide extra-core specialproject funding. CIMMYT would bepleased to accept <strong>the</strong> challenge andcoordinate <strong>the</strong> efforts to develop wheatsbetter adapted to more tropicalenvironments.In <strong>the</strong> CGIAR system. <strong>the</strong>re was a goodfriend representing an organization whocame forward qUickly and said. ItAcceptthat challenge. Let us fund it. tt Thatperson is with us today. and he is yournext speaker. Let me present to youWilliam Mashler of <strong>the</strong> United NationsDevelopment Programme.An increasing dependency on staplefoods from abroad is a serious economicand political problem for manydeveloping countries. In recognizingthat problem several years ago. <strong>the</strong>Technical Advisory Committee of <strong>the</strong>

3 _Keynote Address: Wheatsfor More Tropical EnvironmentsW.T.llashler. seDlor Director. Division for Global andIDterregioDal Projects. UDited Nations neYelopment ProgrammeIt is always a great pleasure for me tobe at CIMMYT. as UNDP and CIMMYThave had a long-standing relationship ofa special nature with each o<strong>the</strong>r. WhenBob Havener and Arthur Klatt kindlyinvited me to come to this conferenceon tropical wheat. I readlly accepted <strong>the</strong>invitation. Whlle I have been asked tobe a keynote speaker at this conference.which is strictly devoted to research ontropical wheat. I would also like to giveyou an overview of UNDP's globalagricultural research and relatedactivities. including support to researchon tropical wheat. To begin with. Iwould like to proVide a brief historicalperspective of <strong>the</strong> Global andInterregional Programme which I havedirected since its inception in 1971.The visit of Paul Hoffman. <strong>the</strong> firstAdministrator of UNDP. to <strong>the</strong>International Rice Research Institute in<strong>the</strong> PhUlppines in 1969. and oursubsequent contacts with CIMMYT. ledto <strong>the</strong> genesis of UNDP's Division forGlobal and Interregional Projects(DGIP). The idea was that UNDP. as <strong>the</strong>world's most broadly based partnershipfor technical cooperation. had both <strong>the</strong>opportunity and <strong>the</strong> obUgation toincrease its involvement indevelopment efforts with potentiallyworld-wide impact. In January 1970.UNDP's Governing Councll approvedsupport for "Global One." aninternational effort to develop highproteinvarieties of maize. a food cropimportant in <strong>the</strong> diets of mlllions ofpersons throughout <strong>the</strong> world. Withthis project. UNDP embarked upon anew form of development support: basicscientific research aimed at finding newsolutions for old problems. in this case.improved nutrition. This began ourlong-standing and fruitful cooperationwith CIMMYT. which in effect helpedcreate <strong>the</strong> concept of UNDP's globalresearch. <strong>the</strong> results of which could bespread to a wide spectrum ofdeveloping countries. Some years havepassed since "Global One" began fullscaleoperations and. during this time.UNDP's Global Program has grown intoa worldwide collaborative researcheffort of <strong>the</strong> highest scientific quality. Acomplementary program of interregionalactivities is designed to spreadresearch results and to assistdeveloping countries in o<strong>the</strong>r areasrequiring international cooperation.Today. <strong>the</strong> combined program spansfive areas of critical importance todeveloping countries:• Food and agriculture• Health. including drinking water andsanitation• International economic relations andeconomic cooperation amongdeveloping countries• Energy• Human resourcesMore than 100 developing countries areparticipating in projects currentlyunder implementation in <strong>the</strong>se varioussectors.Two basic convictions underlie all of<strong>the</strong> GloballInterregional Programme'sactivities. The first is that every seriousdevelopment must be accompanied bya constant search for new knowledgeand new approaches which strike notonly at <strong>the</strong> symptoms but at <strong>the</strong> causesof underdevelopment. The second isthat many problems faced bydeveloping countries can be dealt wi<strong>the</strong>ffectively only within a framework of

global cooperation that permits apooling and exchange of knowledge.skills and experience. Over <strong>the</strong> years.<strong>the</strong> Global and InterregionalProgramme has proved to be a highlyuseful vehicle for promoting suchcooperation. both among developingcountries <strong>the</strong>mselves. and betweenUNDP. o<strong>the</strong>r international donors andrecipient countries. The Programme's"multiplier effect" has been substantial.Between 1971 and 1982. for example.US$ 104.2 million of UNDP's global andinterregional funds have helped togenerate. and have been pooled with.an additional US$ 1.816.3 millionmobilized from o<strong>the</strong>r sources in supportof common efforts. This represents anamount nearly 17th times larger than<strong>the</strong> catalytic UNDP contribution.Ano<strong>the</strong>r great strength of <strong>the</strong>Programme has been <strong>the</strong> opportunity ithas prOVided for UNDP to pioneer andinnovate. Respecting always <strong>the</strong>Importance of close consultation withgovernments. United Nations agencies.foundations and o<strong>the</strong>rs capable ofgiving advice in formulating <strong>the</strong>Programme and developing individualprojects. we have been able to embarkupon a number of promising newapproaches to problems which havehistorically plagued mankind. Andthus. with a bit of Imagination. carefulplanning and tight management andmonitoring. <strong>the</strong> program has. in manycases. helped to convert promise intoreality.As in so many worthwhile endeavors.resources are at best low and one is ledto question how hunger can be attackedwith hunger. Yet somehow we havemanaged. and I hope that in <strong>the</strong> yearsahead <strong>the</strong> level of resources at UNDP'sdisposal will permit not only acontinuation of UNDP global andinterregional activities. but <strong>the</strong>irexpansion. Few o<strong>the</strong>r activitiessupported by international systems ofassistance have been more responsiveto <strong>the</strong> call of <strong>the</strong> Preamble of <strong>the</strong>Charter of <strong>the</strong> United Nations to"employ international machinery for<strong>the</strong> promotion of <strong>the</strong> economic andsocial advancement ofall peoples."There are two features of UNDP's globalactivities which set <strong>the</strong>m apart from <strong>the</strong>typical UNDP-supported project. Thefirst Is that <strong>the</strong>y are research-orientedactivities which involve a complex andlong-term process including:• Fundamental research;• Field testing or clinical trials:• Fur<strong>the</strong>r research to adapt results todiverse conditions prevailing indifferent countries and regions of <strong>the</strong>world;• Training of large numbers ofnational scientists and technicians in<strong>the</strong> application of results. and• Streng<strong>the</strong>ning agricultural andhealth services to achieve effectivedelivery.By its nature. this is a process whichrequires sustained long-term support ata minimum level over a 10 to IS-yearperiod in many cases and. frequently.longer. I have stressed this pointrepeatedly over <strong>the</strong> years. and I do soagain today.I also stated earlier that ano<strong>the</strong>r uniquefeature of <strong>the</strong> global activities is that<strong>the</strong>y represent a collaborative effortsupported jointly by UNDP and a largenumber of o<strong>the</strong>r donors. as well asdeveloping countries <strong>the</strong>mselves. Tomobilize <strong>the</strong> needed resources. UNDPhas helped promote and has played akey role with o<strong>the</strong>r organizations. bothwithin and without <strong>the</strong> United Nationssystem. in building up several majorconsortia which now provide hundredsof millions of dollars annually foragricultural and health research. Themost prominent example is <strong>the</strong>Consultative Group on InternationalAgricultural Research (CGIAR). ofwhich UNDP is a co-sponsor. toge<strong>the</strong>rwith FAO and <strong>the</strong> World Bank. In most

16cases. UNDP resources from <strong>the</strong> globalprojects play an important catalytic rolein attracting collateral support fromo<strong>the</strong>r donors. What is remarkable is <strong>the</strong>fact that <strong>the</strong>se supporting organizationsare ones which generally like to seeminimum risk and maximum safety ininvestment. They have learned qUicklyand with unmatched enthusiasm thatrisks taken, as <strong>the</strong>y must be inscienUfic research. can pay handsomedividends. particularly when <strong>the</strong>investments are made in institutions ofexcellence such as <strong>the</strong> IARCs. Equallyremarkable here is ano<strong>the</strong>r fact: <strong>the</strong>actors and personalities who created<strong>the</strong> system are for <strong>the</strong> most part gone,but those who are now representing<strong>the</strong>ir donor organizations are no lesssupportive of <strong>the</strong> system than were<strong>the</strong>ir predecessors. Speaking ofnetworking in <strong>the</strong> area of scienUficresearch, we have scored success alsoin achieving what hopefully will be along-tenn network of donor support.I mentioned that <strong>the</strong> main emphasis in<strong>the</strong> global program is placed onagricultural research. which represents72% of <strong>the</strong> program's resources: healthresearch has claimed 24% of <strong>the</strong>available resources. The program inagriculture consists of:• Development of improved varities ofimportant food crops such as rice.wheat (adapted to tropical climates).maize, sorghum, millet, cassava,sweet potato and potato. combininghigher yields with resistance to pestsand diseases, at selected IARCs:• Enhancement of <strong>the</strong> nutritio.nalquality of maize through increasingits protein content, at CIMMYT:• Multilocation testing of differentstrains of rice to adapt <strong>the</strong>m tovarious agroecological conditions.including drought. cold, adverse soUconditions. pests and diseases as partof a global network of rice testingprograms,atlRRI:• Research on enhancement ofbiological nitrogen fixation by freeliVingbacteria. azolla and blue-greenalgae in association with paddy solls.and also fixation-associated foodlegumes such as cowpeas andsoybeans. at IRRI. UTA and ICARDA:• Improvement of efficiency of soUwateruse by food crops under aridconditions. at ICARDA;• Intensification of research on <strong>the</strong>development of pest managementtechniques through biologicalmethods of control as an alternativeto expensive. toxic andenvironmentally unsafe chemicalpesticides. at ICIPE;• Continuation of basic research todevelop effective and economicallyviable measures to controltrypanosomiasis and o<strong>the</strong>r diseaseswhich seriously limit livestockproduction. at ILRAD;• Research and training in fertllizertechnology and utilization to conductstudies on <strong>the</strong> efficiency of nitrogenand phosphorus fertilizers underdifferent soU conditions. and aprogram to train developing-countrypersonnel in fertilizer production.distribution. marketing andutilization. at IFDC;• Intensification of currentagroeconomic research in East Africaand its extension into Asia throughon-farm trials and farm level surveysto facilitate <strong>the</strong> adoption of improvedtechnology by fanners. at CIMMYT.and• Research on food systems beingconducted by IFPRI in associationwith <strong>the</strong> United Nations ResearchInstitute for Social Development and<strong>the</strong> United Nations University.

17Recognizing <strong>the</strong> importance of closerlinks between our global researchprojects and national programs. wehave made a special effort to expand. to<strong>the</strong> extent possible from availableresources. <strong>the</strong> scope of our projects tostreng<strong>the</strong>n national capabilities throughincreased training opportunities.conferences. workshops and. in certaincases. small grants to selected nationalinstitutions to undertake collaborativeresearch. The International RiceTesting and Improvement Programmeand <strong>the</strong> West African Sorghum andMillet Improvement Programme beingsupported by UNDP are excellentexamples of such collaborativeprograms designed to streng<strong>the</strong>n linkswith national institutions. Expandedtraining of nationals of developingcountries continues to be a vital andintegral part of all of our current andfuture projects. However. it is obviousthat. in view of <strong>the</strong> financial limits ofour Global Programme. a much largereffort has to be made by donor agenciesand developing countries <strong>the</strong>mselves tomobilize adequate resources tostreng<strong>the</strong>n national institutions. so asto ensure sustained agriculturalproduction in developing countries tomeet <strong>the</strong> needs of a growing population.In all of our projects with <strong>the</strong> IARCs. wehave. from <strong>the</strong> beginning. encouragedinter-institutional cooperation inpertinent fields. including close linkageswith related disciplines. For example.ever since we became involved withCIMMYT on research to improve <strong>the</strong>quality of protein in maize. I have beenemphasiZing to crop-oriented IARCs <strong>the</strong>importance of developing closerinteraction between nutritional andcrop sciences. so that an understandingcan be reached on <strong>the</strong> parameters fornutritional improvement of food crops. Iam indeed glad that we played a role inbringing toge<strong>the</strong>r concerned IARCs at<strong>the</strong> recent nutrition workshop at ILCA.supported by UNDP. which was <strong>the</strong>culmination ofan effort which I startedyears ago.Although <strong>the</strong> IARCs were created asindividual entities. it was always <strong>the</strong>intent of <strong>the</strong> founder of <strong>the</strong> CGIARsystem that <strong>the</strong>y interact with eacho<strong>the</strong>r Within a system of centers. As <strong>the</strong>IARCs have grown and matured. wecan now see how <strong>the</strong>y fit into <strong>the</strong>system. respond to each o<strong>the</strong>r's needsas well as to those of nationalprograms. and thus are forgingimportant links and networks whoseeffectiveness will increasingly benefit<strong>the</strong> objectives of our joint aims. Thisissue needs to be pursued Vigilantlyand new opportinities recognized andseized. As an example, I point to <strong>the</strong>study of <strong>the</strong> integration of IARCactivities in sou<strong>the</strong>rn Africa (Sou<strong>the</strong>rnAfrica Development CoordinationConference. SADCC). which wasinitiated at my suggestion at <strong>the</strong> lastmeeting of <strong>the</strong> CGIAR in 1984. O<strong>the</strong>rexamples of intercenter cooperation are<strong>the</strong> recent agreement between CIMMYTand lITA on maize research in Africa.collaborative arrangements betweenICARDA and CIMMYT and jointendeavors between CIAT. CIP and IITA.There are many o<strong>the</strong>rs. including <strong>the</strong>joint rice-wheat integrated productiontrials initiated by IRRI and CIMMYT.Going back to our association withCIMMYT. it is a matter of greatsatisfaction to us that UNDP's sustainedasistance to research at CIMMYT hascontributed to a major breakthrough in<strong>the</strong> development of <strong>the</strong> high-qualityprotein maize. This is indeed aspectacular achievement in research onplant breeding and genetics involVing acrop which constitutes <strong>the</strong> staple diet ofmillions of people in <strong>the</strong> world. A stagehas been reached where efforts shouldbe made to encourage countries toadopt <strong>the</strong> nutritionally rich maize on alarge scale. although it is recognizedthat in several countries an activepromotional campaign is needed tofamiliarize 'farmers and senior

18government officials with <strong>the</strong> potentialbenefits of <strong>the</strong> new maize. We arepleased to extend continued UNDPassistance to research and training inmaize improvement for an additionalperiod of five years, beginning inJanuary 1985. The project recentlyapproved by our Council presents anew image involving three programthrusts, international testing, trainingand nutritional studies. CIMMYT will beable to sustain and expand itsinternational maize testing and totransfer to developing-country farmersimproved maize varieties, combininghigher yield and nutritional quality.Over 50% of <strong>the</strong> funds requested fromUNDP will be spent on trainingdeveloping-country scientists at variouslevels in all aspects of maizeimprovement. The nutritional studiesenVisaged in <strong>the</strong> project will be anessential complementary activity to beimplemented by <strong>the</strong> Instituto deInvestigacion Nutricional (lIN) in Peru,under subcontractual arrangementswith CIMMYT.Now I wish to make a few remarks onour support to research on wheatadapted to tropical environments. Ishall confine myself to some generalobservations, as all <strong>the</strong> technicalaspects will be covered in depth at thisconference. The considerable vision andforethought displayed in our globalprogram is attested to by <strong>the</strong> fact that Ihave been extremely receptive to newideas and have readily responded withfunds, from whatever resources wereavailable, for new research initiativeswhich have <strong>the</strong> potential to producepromising results. Our support toCIMMYT's program to develop wheatvarieties adapted to tropicalenvironments is a striking example.Wheat accounts for more than onequarterof total world grain production,and is a staple food for one-third of <strong>the</strong>world's population. Originating in <strong>the</strong>subtropical and temperate climates of<strong>the</strong> Middle East, over <strong>the</strong> centurieswheat spread into temperate nor<strong>the</strong>rnclimates. There, cultivators andscientists greatly improved its yieldpotential, <strong>the</strong> breadth of its adaptationand its resistance to <strong>the</strong> pests anddiseases most devastating in thoseenvironments. In <strong>the</strong> early 1960s,CIMMYT developed <strong>the</strong> first highyieldingdwarf wheats, whichdramatically increased yieldsthroughout <strong>the</strong> world.Bob Havener and his associatesbelieved that wheat could playa muchmore important role in tropicalcountries. if resistance to a variety offungus diseases and insect pests couldbe overcome. It has considerabletolerance to drought. is a high-yieldingcrop of short duration and prOVideshigh quality food which is readilyaccepted. I agreed to advance somefunds for fur<strong>the</strong>r preparatory work.CIMMYT has already started to crosswheat with related tropical grassspecies to see if <strong>the</strong>ir insect and diseaseresistance can be transferred, as well assome of <strong>the</strong>ir tolerance to tropical soils.Developing countries throughout muchof <strong>the</strong> tropics are also becomingincreasingly dependent upon wheat asa relatively low-cost source of food for<strong>the</strong>ir urban poor and landlesspopulations. Some wheat is homegrown in <strong>the</strong> tropiCS and subtropicsduring <strong>the</strong> drier. cooler seasons, butyields are relatively low, due to <strong>the</strong>generally short grOWing seasons. Thecrop also suffers much damage frominsects and diseases, since littleresearch has been done to developresistance to tropical pests anddiseases. Tropical countries must,<strong>the</strong>refore. import wheat to satisfydomestic demand. using up scarceforeign exchange.

19With UNDP assistance. CIMMYTexpanded this research to:• Identify and assemble availablegermplasm of wheat and relatedspecies possessing agronomiccharacteristics desirable for warmer.subtropical areas;• Intensively screen <strong>the</strong>se materials fordesired traits;• Establish special advancedgeneration nurseries to facilitatescreening. and• Arrange locations for testingadvanced materials.In 1982. UNDP agreed to support a fiveyearproject with a contribution ofUS$ 2.5 million to enable CIMMYT tofur<strong>the</strong>r expand research to develophigh-yielding. disease-resistant.semidwarf wheats that would performwell in <strong>the</strong> warmer. subtropical areas of<strong>the</strong> world. At that time. three-fourths ofali wheat grown in developing countrieswere varieties developed or improved atCIMMYT. In addition to breeding andtesting. <strong>the</strong> project involves trainingand conferences for <strong>the</strong> exchange ofinformation and experience. Personnelfrom developing countries are beingtrained in <strong>the</strong> development of newvarieties. agronomic research anddisease methodology. Regionalworkshops and conferences arebringing CIMMYT and developingcountryscientists toge<strong>the</strong>r to focus onresearch progress and problems. Theproject will also enable CIMMYT toprovide basic research equipmentwhich is lacking in many countries. Itis extremely gratifying to note that <strong>the</strong>results obtained to date areencouraging and it can be hoped that.in <strong>the</strong> not too distant future. severalvarieties adapted to tropicalenvironments will be available forproduction programs.Ano<strong>the</strong>r example of my encouragementand support to new research ideas is<strong>the</strong> program on wide crosses in wheatand maize. I have been fascinated by<strong>the</strong> idea of transferring genes into oramong crops for greater diseaseresistance. tolerance to environmentalstresses. such as drought. salinity,acidity and aluminum toxicity. andhigher protein quality. I am confidentthat an intensification of research inthis area. with support from <strong>the</strong> donorcommunity. will produce useful andapplied results in <strong>the</strong> foreseeable future.I am indeed glad to have been able toprovide modest financial support fromUNDP. since additional assistance willbe forthcoming from o<strong>the</strong>r donors.Understandably. this program maypresent a higher risk than conventionalbreeding programs. as <strong>the</strong>re is noguarantee that it will be successful as asource of genes for <strong>the</strong> germplasmdevelopment and breeding programs.However. in my years of experience indevelopment projects. I have neverhesitated to take a risk or gamble aslong as I am assured of <strong>the</strong> scientificquality of <strong>the</strong> programs and that <strong>the</strong>ywill be implemented by first-classscientists from reputable institutions.Ultimately risk is what science is allabout; if we do not take risks. nothingwill happen.Now I wish to make some concludingremarks about <strong>the</strong> great many effortsbeing made in international agriculturalresearch. The vision which led to <strong>the</strong>establishment of <strong>the</strong> original IARCsand. subsequently. to <strong>the</strong> creation of<strong>the</strong> Consultative Group was asignificant. if not <strong>the</strong> most important.step in <strong>the</strong> direction of filling atremendous void which had impededinternational agricultural development.What started as an intended first stepcannot be regarded as <strong>the</strong> fulfillment of<strong>the</strong> vision; it was merely <strong>the</strong> first step.We here. and o<strong>the</strong>rs elsewhere. who areparties to this most essential endeavor.

20must realize that <strong>the</strong> centers have beencast in a role much greater thanresearch on crops, cropping andfarming systems. They should, in myview, become <strong>the</strong> catalysts anddiagnostic tools in anticipating <strong>the</strong>concomitant needs that must beaddressed in <strong>the</strong> years and generationsahead, so that <strong>the</strong> dynamics generatedat <strong>the</strong> time of <strong>the</strong>ir creation do notfalter or stagnate. With every step, wi<strong>the</strong>very solution found to problems. wi<strong>the</strong>very bit of new knowlegdeacquired.<strong>the</strong>re arise new issues in achanging and growing world. Thecenters are uniquely positioned now toplay this role, and <strong>the</strong>y are able toanticipate in scientific and technicalterms <strong>the</strong> projected needs and demandswhich go beyond <strong>the</strong>ir originalmandates. They are, <strong>the</strong>refore. in aposition to create awareness amongthose in <strong>the</strong> political sphere of <strong>the</strong>irresponsibility to help <strong>the</strong>ir constituentsreap <strong>the</strong> full benefits of properly appliedscientific opportunities.In short, vision, opportunities andresponsible interaction will ultimatelycreate <strong>the</strong> climate for enlighteneddecisions to be made. This will takecourage and persuasion.Food. health, water and energy areessential to sustain life on our planet.They have a fundamental impact on<strong>the</strong> human condition, and willultimately determine whe<strong>the</strong>r humanbeings can function to <strong>the</strong> optimumlevel of <strong>the</strong>ir capacity. This is <strong>the</strong>crucial element in development, andmust be <strong>the</strong> foremost concern, as I amsure it is. of each and everygovernment. Over <strong>the</strong> last 14 years, Inever permitted this importantconsideration to be lost in our supportof what I believe to be <strong>the</strong> cornerstoneof development and <strong>the</strong> right of everyhuman being.We, in <strong>the</strong> donor community who havesupported your work. are truly gratefulto you who are in <strong>the</strong> midst of a greatenterprise that has produced much andholds forth <strong>the</strong> promise of excitingnew ventures for <strong>the</strong> improvement of<strong>the</strong> condition of mankind. When welook around us and see how muchtime, money and effort is spent onso much that is unproductive, wastefuland discouraging. we can only marvelat how much is being achieved with solittle here in <strong>the</strong> interest of so many.Too few in our world know, much lessappreciate, <strong>the</strong> splendid achievementsof <strong>the</strong>se international enterpriseswhich transcend political borders,differences and conflicts. Ininternational research, political chasmshave to be bridged by <strong>the</strong> scientificfraternity. It is initiative andcommitment which are indispensible.It seems to me that individual peopleare more important than institutions,which are <strong>the</strong> servants of people.Selfish objectives must be sublimatedin <strong>the</strong> interests of vast numbers ofpeople liVing in poverty and looking forhope. We can take great pride in ourjoint endeavor. which is an essentialingredient for <strong>the</strong> improvement of <strong>the</strong>quality of <strong>the</strong>ir lives. Indeed, it points<strong>the</strong> way towards eliminating intolerableinequities and laying <strong>the</strong> foundationsfor peace.

4 21Introduction to <strong>the</strong> <strong>Symposium</strong> onWheat for More Tropical EnvironmentsA.R. Klatt, Associate DIrector, Wheat Program, CIMMYT, MexicoIs is my pleasure. on behalf of <strong>the</strong>organizing committee and <strong>the</strong> CIMMYTWheat Program. to welcome you toMexico and to this <strong>Symposium</strong> onWheats for More TropicalEnvironments. We hope your stay inMexico and your participation in thissymposium w1ll prove to be bothinteresting and rewarding.Mr. Mashler has just shared with us hisInsights into <strong>the</strong> problems associatedwith introducing wheat as acommercial crop in more tropical areas.The constraints are obviouslynumerous and complex. and w1llrequire a concerted and coordinatedresearch effort to resolve. I want toemphasize <strong>the</strong> need for a coordinatedapproach to this research endeavor andnote that. while we have a basicunderstanding of <strong>the</strong> directions inwhich this research should move. atthis time we have few answers to <strong>the</strong>numerous perplexing problems beforeus.ReasODs for <strong>the</strong> <strong>Symposium</strong>Many people have asked why asymposium on wheats for more tropicalenvironments is being held now. given<strong>the</strong> limited information and researchresults currently In hand. Research ontropical wheat does constitute a recentinitiative. and It would be premature todraw extensive conclusions from datanow available. Never<strong>the</strong>less. <strong>the</strong>re ismuch to be gained at this time from asymposium such as this. If a trulycoordinated approach to research Is tobe implemented. it Is essential that anexchange of ideas among Involvedscientists occur early in <strong>the</strong> process.This forum has been created in aneffort to encourage and facilitate <strong>the</strong>interaction of wheat researchers whohave worked in <strong>the</strong> target environmentsof <strong>the</strong> world. as well as those who arejust beginning <strong>the</strong>ir research. We areconfident that this interaction will leadto a mutually beneficial sharing of ideasand specific information relative to <strong>the</strong>development of better-adapted wheats.It is also hoped that. as we identify <strong>the</strong>major constraints to <strong>the</strong> cultivation ofwheat In more tropical areas. we cancome to some agreement as to <strong>the</strong>irrelative Importance. By collectivelyassigning priorities to various researchactivities. we should be able to worktoge<strong>the</strong>r in a more coordinated andcooperative manner. thus facilitating<strong>the</strong> resolution of <strong>the</strong> most pressingproblems. The papers presented herew1ll describe <strong>the</strong> research currentlyunderway. much of which is focused onproblem identification and definition. Abetter understanding of <strong>the</strong> scope of<strong>the</strong>se current research activities. in <strong>the</strong>context of our common objectives. willgreatly help us in establishing prioritiesfor future research.Some Key DefinitioDsBefore proceeding any fur<strong>the</strong>r. it isimportant to clarify what is meant by<strong>the</strong> terms "tropical wheat" and..wheats for <strong>the</strong> more tropicalenvironments." The use of <strong>the</strong> term"tropical wheat" does not mean thatwheats for hot. humid. rain forestenvironments are under development.Wheat is a temperate crop. and it maynot even be possible to developgermplasm that will survive in rainforest environments. "Tropical wheat"is merely _an easy way of referring to.•wheats for <strong>the</strong> more tropicalenvironments." That is. we at CIMMYT

22and many of our cooperators around<strong>the</strong> world are attempting to identifywheats that can be grown successfullyin <strong>the</strong> warmer areas of <strong>the</strong> world wherewheat is not a traditional crop.Tropical wheat environments includemost of <strong>the</strong> areas lying between <strong>the</strong>Tropic of Cancer (23 0 north) and <strong>the</strong>Tropic of Capricorn (23 0 south), plusadjacent areas with tropical orsubtropical conditions. Within this areaof <strong>the</strong> world, <strong>the</strong>re appear to be twobasic types of environments in whichwheat can be grown. One ischaracterized by warm temperatures,generally sunny days and low relativehumidity compared to <strong>the</strong> norm for <strong>the</strong>tropics. Under <strong>the</strong>se conditions, diseaseresistance will not be a majorconsideration, but varieties with heattolerance and adapted to a ra<strong>the</strong>r shortgrowing season will be necessary. Theo<strong>the</strong>r major wheat environment istypified by warm temperatures andhigher relative humidity. A number ofwheat diseases, many of which are notcommon to traditional, temperate,wheat-growing areas, will be prevalentunder <strong>the</strong>se conditions. For wheat to besuccessfully grown, better resistance to<strong>the</strong>se diseases must be incorporated.CIMMYT's Interest inTropical WheatsICIMMYT's research mandate calls for<strong>the</strong> rapid and continuous developmentof improved germplasm, primarily foruse in <strong>the</strong> developing world.Approximately one billion people live in<strong>the</strong> tropical countries of <strong>the</strong> developingworld and, while wheat is currently aminor crop in <strong>the</strong> tropics, itsconsumption is increasing rapidly,especially in <strong>the</strong> urban areas. As ofmid-1983, about 85% of <strong>the</strong> wheatconsumed in tropical nations was beingimported, and <strong>the</strong>se countriesaccounted for about 20% of <strong>the</strong> totalworld wheat trade.Rapidly expanding consumption ofwheat in <strong>the</strong> countries of <strong>the</strong> tropics isresulting in an increasing dependanceon imports. In many instances, <strong>the</strong>seimports represent a large drain onforeign exchange. Many governmentsnow believe it would be better toconduct <strong>the</strong> research necessary todevelop wheats for <strong>the</strong>ir specificconditions, in order to be able to growat least a portion of <strong>the</strong>ir wheatrequirements.The development of wheats adapted to<strong>the</strong> short, cool season in <strong>the</strong>se moretropical countries would also allow forcrop intensification. Rice is currently<strong>the</strong> predominant crop, and is generallygrown during <strong>the</strong> summer monsoon. Asecond crop is seldom grown in <strong>the</strong>winter season, except in those areaswhere irrigation is available. With itslower moisture requirements comparedto rice, and with its adaptation to coolertemperatures, wheat has potential as analternate crop for <strong>the</strong> winter season. Inmany instances, a crop of wheat couldbe grown on residual moisture or withlimited irrigation, and recent researchhas indicated that reasonable yields canbe achieved under <strong>the</strong>se conditions. Byintroducing a second crop into <strong>the</strong>cropping cycle, <strong>the</strong> total domesticproduction of food grains could besignificantly increased.General Production ConstraintsThere are many production constraintsthat must be resolved before wheat canbe introduced successfully into <strong>the</strong>seenvironments. ResolVing <strong>the</strong>seproblems would benefit more than <strong>the</strong>tropical countries alone; wheatproduction in many of <strong>the</strong> traditionalwheat-growing areas would also beenhanced. Among <strong>the</strong> areas requiringresearch are <strong>the</strong> follOWing:Heat toleranceGermplasm with better tolerance tohigher temperatures is absolutelynecessary for many areas. Greater heattolerance during <strong>the</strong> juvenile growthstage and also during <strong>the</strong> flowering and

23grain-filling stages are required.Screening efforts are underway toidentify germplasm of this type. Itsdevelopment would benefit tropicalwheat areas, as well as manytraditional wheat-producing areas, suchas Bangladesh, nor<strong>the</strong>ast India,sou<strong>the</strong>rn Pakistan, South China. <strong>the</strong>Cerrados of Brazil and o<strong>the</strong>r subtropicalareas.Better ellsease resistanceAs mentioned earlier, diseases will be aproblem primarily in <strong>the</strong> more humidregions. Leaf rust. stem rust.helminthosporium, fusarium, root rotsand possibly barley yellow dwarf are<strong>the</strong> diseases that will most likely beimportant. Good resistance to leaf rustand stem rust are available in existinggermplasm. Intensive efforts, frequentlyin cooperation with national programsaround <strong>the</strong> world, are now underway toidentify sources of resistance toHelmtnthosportum and Fusariumspecies. A cooperative program hasbeen initiated with China to identifywheats with better resistance tofusarium head scab. and a similarcooperative effort is being pursued withBrazil to identify better resistance toHelmtnthosporium species. Theseefforts, in combination with o<strong>the</strong>rs,should give us wheats with muchimproved levels of resistance within <strong>the</strong>next five years.It is probable that root rots will causesevere losses in certain environmentswithin <strong>the</strong> tropiCS. We know very littleabout <strong>the</strong> array of organisms that causeroot rots; this topic will be fur<strong>the</strong>rdiscussed during <strong>the</strong> symposium.Barley yellow dwarf is a problem inmany environments of <strong>the</strong> world, notjust in <strong>the</strong> tropics. CIMMYT, incooperation with many nationalprograms, has undertaken aninternational effort to developgermplasm with better barley yellowdwarf resistance. Once resistance isidentified, it will only be necessary totransfer it into adapted wheats.Agronomic practicesIn many tropical countries. littleresearch has as yet been conducted on<strong>the</strong> agronomic practices reqUired tosuccessfully grow wheat. In <strong>the</strong> nearfuture, we must elucidate <strong>the</strong> variousagronomic practices that will berequired to successfuly cultivate wheatin <strong>the</strong> diverse environmental conditionsof <strong>the</strong> tropics. Paramount among <strong>the</strong>sepractices will be proper dates ofseeding, weed control, fertilization and.of course, proper soil management.The majority of <strong>the</strong> soils in <strong>the</strong> tropicsare paddy soils with a high clay contentand, generally. a hard pan which helpsto retain moisture during <strong>the</strong> grOWingof <strong>the</strong> rice crop. We know little aboutgrOWing wheat on <strong>the</strong>se soils, but <strong>the</strong>problems associated with <strong>the</strong>cultivation of wheat under <strong>the</strong>secircumstances are many. It is quitelikely that wheat will be first grownunder upland conditions in <strong>the</strong> tropics.since more research information isavailable for <strong>the</strong>se conditions. Thevarious problems related to agronomywill be covered in much more detaildUring <strong>the</strong> symposium.ConclusionsIn closing, let me repeat that <strong>the</strong>purpose of this symposium is not toresolve <strong>the</strong> various constraints tointroducing wheat into <strong>the</strong> tropics.Ra<strong>the</strong>r. our main objective is to bringtoge<strong>the</strong>r wheat researchers from around<strong>the</strong> world in an effort to facilitate <strong>the</strong>exchange of ideas and information. Weare striving for a collective awarenessand common understanding of <strong>the</strong>major problems before us. In strivingfor this common ground. <strong>the</strong> stage willbe set for <strong>the</strong> kind of cooperative globaleffort needed to successfuly developwheats for more tropical environments.

5 _Country ReportsSelecting and Introducing Wheatsfor <strong>the</strong> Environments of <strong>the</strong> TropicsC.E. Mann, Wheat Program, CIMMYT, Bangkok, ThailandAbstractThe estimated wheat area in <strong>the</strong> tropics, i.e., between 23ON and 23°5 latitudes,is 3 to 4 million hectares. The potential existsfor <strong>the</strong> expansion ofthis area as aresult ofresearch. A survey ofclimatic conditions and wheat yield levels from 28experiment stations in 15 countries between 1 and 39° Nand S latitudes showsonly a moderate association between climate and yield. Average minimumtemperaturefor <strong>the</strong> month afterflowering has <strong>the</strong> highest correlation with yield(r= -.51), indicating that o<strong>the</strong>r more controllablefactors, such as cropmanagement and germplasm, have considerable influence on yield. Importantresearch objectivesfor tropical wheat are presented in this paper, and <strong>the</strong>importance ofstrong national programs is stressed.The purpose of this overview of tropicalwheat is to establish a frame ofreference for <strong>the</strong> country reports. Afterdiscussing <strong>the</strong> present wheatproduction situation in <strong>the</strong> tropics and<strong>the</strong> interests of national programs inpursuing wheat research, a tentativelist of production constraints which arecommon to many places in <strong>the</strong> tropicswill be presented. This is done mainlyfrom <strong>the</strong> author's experience; <strong>the</strong>country reports may ei<strong>the</strong>r substantiatethis list or emphasize o<strong>the</strong>r factors,some of which may be generalproblems applicable to <strong>the</strong> tropics, ando<strong>the</strong>rs, problems specific to certaintropical environments.The Wheat Situationin Tropical CountriesThe word "tropics" as used here refersto <strong>the</strong> area between <strong>the</strong> tropiCS ofCancer and Capricorn, that is, between23°N and 23°5 latitude. There are 85countries that have 20,000 or moresquare kilometers of territory within <strong>the</strong>tropics. Of <strong>the</strong>se, some have no interestin wheat production, and some have noarable land in <strong>the</strong>ir tropical zones.Eliminating <strong>the</strong>se. <strong>the</strong>re are still 57countries which have grown wheat in<strong>the</strong> tropics at some time during <strong>the</strong> lastthree years, ei<strong>the</strong>r experimentally orcommercially (Table 1).Among those countries that lie entirelywithin <strong>the</strong> tropics, or which grow <strong>the</strong>majority of <strong>the</strong>ir wheat in <strong>the</strong> tropics,566,000 hectares of wheat were grown;nearly half of this amount was in <strong>the</strong>Sudan. A more meaningful figure isreached by also including thosecountries that, although <strong>the</strong> majority of<strong>the</strong>ir wheat is grown outside <strong>the</strong>tropics, have substantial wheat areaswithin <strong>the</strong>ir tropical zones as well. Thisallows <strong>the</strong> inclusion of <strong>the</strong> vast areas ofpeninsular India and sou<strong>the</strong>rn China,<strong>the</strong> wheat-growing area in nor<strong>the</strong>rnBrazil, and smaller portions of o<strong>the</strong>rcountries, such as <strong>the</strong> lowlands ofBolivia and sou<strong>the</strong>rn Bangladesh. Thisfigure is estimated at between 3 and 4million hectares, with more than half of<strong>the</strong> total in India. Clearly, wheat is nota completely new crop in <strong>the</strong> tropics.Table 1 indicates <strong>the</strong> growing interestin expandJng wheat production intotropical areas; a number of countrieswhich grow no wheat commercially are,never<strong>the</strong>less, beginning to do someresearch on wheat.

Table 1. Countries growing whut in <strong>the</strong> tropics and area of production, 1981Country Area" Country Are.AI(000 h.) (000 h.)AmericaAfrica (con'd)Mexico (861) Tanzania (50)Guatemala (64) Rwanda (4)Honduras 1 Burundi (6)Nicaragua Angola (16)Costa Rica Zambia (3)Dominican Republic Malawi 1Colombia (39) Mozambique 3Venezuela (2) MadagascarGuyana Zimbabwe 41Brazil (1,921) Namibia 1Peru (100) Botswana 3Ecuador (37)Bolivia (77) AsiaParaguay (70) Saudi Arabia 85Yemen, Arab Rep 66Africa Yemen,PDR 10Mauritania Oman 0.3Mali 2 Fed. of Arab Emirates 0.4Niger 2 India (22,104)Chad 3 Sri LankaSudan 240 Bangladesh (591)Ethiopia (523) Burma 88SenegalThailandUpper VoltaVietnamGhana China (29,201)Nigeria 13 TaiwanCameroon 2 PhilippinesSomalia 4 MalaysiaZaire (5) IndonesiaUganda (4)Kenya (120) Australia (12,041).AI Numbers in brackets indicate that <strong>the</strong> majority of <strong>the</strong> wheat area is outside <strong>the</strong> tropicsor above 1500 m altitudeSource: FAO Production Yearbook (4)

26The need for research on wheatproduction in <strong>the</strong> tropics is reinforcedby <strong>the</strong> fact that seven of <strong>the</strong> eightcountries which increased wheatproduction by more than 5% annuallybetween 1961-65 and 1981-82 (2) arelocated completely or partially within<strong>the</strong> tropics: Sudan. Tanzania,Zimbabwe, Yemen, Bangladesh, Braziland Paraguay.It is not possible to give a preciseestimate of <strong>the</strong> extent of <strong>the</strong> tropicalarea in which wheat can be grown,ei<strong>the</strong>r immediately or after a reasonableamount of research in agronomicpractices and variety development.However, three major areas offerpotentially millions of hectares of wheatland, ifresearch can help to solve <strong>the</strong>follOWing management problems:• Cerrado lands-The Cerrados arecharacterized by tree-bush-grassecosystems and occur in Brazilbetween 5 and 20 0 S latitude and 45and 60 0 W longitude. Twelve millionhectares in this area are estimated asbeing suitable for wheat. The soilsare red-yellow and dark red latosols;<strong>the</strong>y are very deep and have a highclay content, low natural fertility andhigh aluminum saturation (3).Similar conditions can be found ono<strong>the</strong>r continents, although not insuch a large single block.• Rice paddies-Millions of hectares ofland throughout Asia lie idle dUring<strong>the</strong> dry season, because <strong>the</strong>re is notenough water for a second rice crop.Although <strong>the</strong>se lands appearpromising, no attempt will be madehere to estimate <strong>the</strong> size of <strong>the</strong> area,since <strong>the</strong>re has been little researchon <strong>the</strong> interactions between suchfactors as water retention capacity,depth of soil above <strong>the</strong> plow pan anddrainage.• Lands that could become available asa result of better plant protectionThis protection againstnontraditional wheat diseases couldcome about ei<strong>the</strong>r through chemicalor genetic means, and wouldimmediately open new areas wherewheat could compete with o<strong>the</strong>rcrops. It would also make irrigationand land-clearing projects morefeasible.Can <strong>the</strong> limits to expanding wheatproduction be described a priori? Itdoes not appear that production islimited by mere geographic location,since triticale grows well at sea level inJaffna in nor<strong>the</strong>rn Sri Lanka and wheatgrows reasonably well at sea level atMojosari. East Java. The correlationbetween latitude and yield of <strong>the</strong> bestfive varieties at each site of <strong>the</strong> 18thISWYN (1). after deleting all tropicalsites above 1500 meters and Harare,Zimbabwe, is only .341; a paraboladoes not give a better fit. The latitude of<strong>the</strong> 55 stations of <strong>the</strong> nursery rangesfrom 12 to 60°, and yield, from 1.3 to8.6 tlha. As nothing can be determinedfrom <strong>the</strong>se figures, o<strong>the</strong>r factors musthave considerable influence.In order to determine whe<strong>the</strong>rmeteorological data can help to definetropical limits for wheat, <strong>the</strong> formpresented here as Figure 1 was sent toabout 40 experiment stations around<strong>the</strong> world where wheat was known tohave been grown. Most of <strong>the</strong>m are in<strong>the</strong> tropics below 1500 meters, andsome are in traditional wheat-growingareas outside <strong>the</strong> tropics. About half of<strong>the</strong>m answered in time to present <strong>the</strong>data here. Some did not have all <strong>the</strong>data requested, and some sent datafrom additional stations in <strong>the</strong>ircountry. Therefore, <strong>the</strong> results includedata for relative humidity and averagemonthly maximum and minimumtemperatures from 28 stations(Table 2).

27Month of sowing and month afterflowering were chosen for calculationsbecause <strong>the</strong>se are critical growth stagesin <strong>the</strong> tropics, representing,respectively, plant establishment, grainruling and possible diseasedevelopment.Linear correlations between yield andwea<strong>the</strong>r data are given in Table 3. Only<strong>the</strong> correlation with average minimumtemperature at month of sowing ishighly significant, and its coefficient ofdetermination is only 26%. This is nothigh enough to use as a basis forestimating yield potential in a certainarea. Calculating <strong>the</strong> multiplecorrelation of <strong>the</strong>se six characters withyield accounts for 47% of <strong>the</strong> yieldvariation: <strong>the</strong> four significantlycorrelated characters account for 43%.This tends to confirm a hypo<strong>the</strong>sisbased on <strong>the</strong> experience of tropicalwheat scientists. that yield levels arenot dependent on maximumtemperatures and are only marginallyinfluenced by minimum temperatures.Caution must be used in generaliZingfrom <strong>the</strong>se findings, and fur<strong>the</strong>r datawUl have to be considered to improveName of station:Town:Latitude:Elevation:monthClimatological Data During Wheat Growing SeasondegreesmProvince:minutesCountry:monthly average maximum temperaturemonthly average minimum temperaturerainfall (mm)relative humidity (0/0)hours of sunshinepotential evaporation(open pan evaporation)normal sowing time of wheat..................•.....................•normal harvesting time of wheat........•••............•...•.•....•.... ,yield level = average yield offive best Iines of advancedyield trial: .....•....................... , " .Figure 1. Form sent to experiment stations for ga<strong>the</strong>ring meteorologicaldata. 1984

28accuracy. However. it can be concludedthat yield is not severely llmited bylatitude or climatic conditions. Withmore data. <strong>the</strong> correlation coefficientcan be expected to be even closer tozero; some of <strong>the</strong> stations close to <strong>the</strong>equator were only in <strong>the</strong>ir second orthird year of growing wheat. and <strong>the</strong>iryields can be expected to rise withmore experience in crop management.Thus. a strong plea is made here foradaptive research in every tropical areawhere wheat is considered a potentialcrop. To fur<strong>the</strong>r illustrate this need. <strong>the</strong>yield of some well-known varieties canbe compared between tropical andtraditional areas (Table 4). The varietiesUres. Pavon and Nacozari are wellabove average in traditional wheatlocations. such as Ciudad Obregon.Mexico. and Faisalabad. Pakistan; <strong>the</strong>yare below or only sUghtly above averagein tropical areas. UP262 performs in <strong>the</strong>opposite manner. and Sonal1ka. andQuimori are erratic in performance.Earliness is ano<strong>the</strong>r unpredictablecharacter as varieties are moved to <strong>the</strong>tropics. While Pavon is five days later inflowering than Nacozari at CiudadObregon. <strong>the</strong>y are equal in maturity atFaisalabad; Pavon is 27 days later thanNacozari at Chiang Mai. Thailand. andnine and eight days later at VillaGuede. Senegal. and Campinas. Brazil.respectively. UP262 is even earlier in<strong>the</strong> tropics than in traditional areas. aTable 2. Location of experiment stations replying to request for meteorologicaldete.1984Country Elevation Latitude Country Elevation Latitudeand station (m) (ON or8) and station (m) ~N or8)ArgentinaIndonesiaLa Dulce 72 38 Kuningan 545 7Brazil Mojosari 30 8Brasilia 1000 16 Margahayu 1250 7Londrina 566 23 Sukarami 928 1BurmaPhil ippinesYezin 97 20 Los Baftos 22 14Lashio 23 SudanTau nggy i 1439 21 Wad Medani 411 14Sagaing Chiang Mai 314 19Monywa702222ThailandMandalay 74 22 USABangladesh Yuma. Arizona 100 33Joydebpur 8 24 Woodland. California 21 39Jessore 8 23 Yemen, PDRIshurdi 7 24 Seiyun 700 16ChinaZambiaNanjing 12 32 Chilanga 1213 16Costa RicaZimbabweSan Josecito 840 10 Harare 1496 18India Chiredzi 429 21Indore 557 22

29. Table 3. Correlation coefficients between yield and climatological parameters, 28 locationsin 15 countries, 1984ParameterYieldAverage minimum temperatureMonth of sowingMonth after floweringAverage maximum temperatureMonth of sowingMonth after floweringAverage relative humidityMonth of sowingMonth after floweringRange800-10,1 00 kg/ha3.7-23.6 0 C8.7-20.8OC12.0-36.1°C14.8-32.4 0 C37-86 0 /038-89 0 /0Correlationcoefficientwith yield-.40*-.51**-.16-.33-.45*-.40**, ** Significant at <strong>the</strong> 5 and 1 % levels, respectivelyTable 4. Relative yields and days t~. flowering of six wheat varieties in traditional and tropicalwheat-growing areasDays to flowering as 0/0Yield as % of location mean of location meanNaco- Sona- Qui- Naco- Sona- Qui-Location Ures Pavon zari UP262 lika mori Ures Pavon zari UP262 Iika moriTraditional areaCd. Obregon, Mexico 120 115 114 90 104 82 107 101 96 90 82 86Faisalabad, Pakistan 108 112 127 92 95 101 105 97 97 93 87 89Tropical areaChiang Mai, Thailand 70 96 96 144 83 180 117 110 83 87 80 81Villa Guede, Senegal 96 101 87 105 87 81 113 98 89 89 81 93Campinas, Brazil 94 108 104 112 117 94 114 98 90 87 80 88Source: The 18th ISWYN, CIMMYT, Mexico

30fact that. toge<strong>the</strong>r with above-averageyield. makes it appropriate for tropicalenvironments (if leaf rust is notpresent). Sonallka has stmllar maturityacross environments. Qulmorl again iserratic in maturity. and probably ino<strong>the</strong>r characters. especlally those ofspikes per square meter. spikelets perspike and lOOO-gratn weight.Unfortunately. this could not bedemonstrated using an orthogonal setof varieties and locations. The need foradaptive research, demonstrated herefor gennplasm. is probably equallyimportant in o<strong>the</strong>r disciplines.Obstacles to <strong>the</strong> SuccessfulIDtroductloD of Wheat IntoTropical AreasAs researchers. <strong>the</strong>re is a need tocategOrize production problems intoproblems of a size that can be handledby research. It is hoped that <strong>the</strong>following breakdown will be helpful forthose presenting country reports.BreediDg and pathologyFollOWing are some problem areas inthis field. toge<strong>the</strong>r with <strong>the</strong> knowledgeof <strong>the</strong> genetic vartabl1lty currentlyavallable. These will be summarized inTable 5.Early heat tolerance-Wheats for <strong>the</strong>tropics must be able to gennlnate in hotsoll. tiller under high temperatures and.subsequently. head nonnally. Manytraditional wheat lines produce onlysmall heads in tropical environments.Genetic vartabl1lty is avallable ingennplasm with good agronomic type.Late heat tolerance-The plant musthave <strong>the</strong> abl1lty to fill <strong>the</strong> graincompletely under high temperatures.This tolerance is enhanced if <strong>the</strong> leavesremain green and active long enough toproduce reqUired asslmllates. Geneticvartabl1lty in good lines is avallable.Tolerance to late drought-Thischaracter is necessary when wheat isgrown on residual moisture. It willenhance grain-filling abl1lty and <strong>the</strong>retention of <strong>the</strong> assimllation area.Again, genetic vartabllity is avallable.For <strong>the</strong>se three characters. limitedknowledge is avallable regarding <strong>the</strong>physiological mechanisms of toleranceand <strong>the</strong>ir genetic control. There is avast area for basic research in <strong>the</strong> threecharacters.Table 6. Breeding characteristics required for tropical environments and an indication ofavailability of genetic variability and suitable screening methodsCharacterEarly heat toleranceLate heat toelranceEarlinessTolerance to late droughtTolerance to acid soils and aluminum toxicityResistance to:Leaf rust (Puccinia recondita)Leaf blotch (Helminthosporium spp.)Seedling blight (Sclerotium rolfsij)ScabWaterlogging. aphids, stemborersGenetic variabilityIVaiiable+++++++++±+?Screening methodsavailable++++++ ±?

31Earliness-Earliness is needed if <strong>the</strong>wheat plant is going to be able to fitinto narrow crop rotations. escapediseases and avoid seasonal environmentalstresses. A broad array ofgenetic variability exists. The mainproblem is to incorporate this characterinto lines which are adapted to tropicalconditions.Tolerance to acid soils and aluminumtoxicity-Considerable research hasbeen conducted for this character. andprogress has been made mainly bycombining Brazilian and Mexicanmaterials.Resistance to leaf rust-Many resistantlines are available. but resistance is notof lasting character. Changes in <strong>the</strong> rustVirulence require <strong>the</strong> continuousattention of pathologists and breedersin order to have resistant lines ready forrelease as current varieties becomesusceptible. As <strong>the</strong> wheat area extendsinto warmer environments. <strong>the</strong>re mustbe a constant awareness of new races ofpathogens.Resistance to helminthosporiumHelminthosporium sativum is by far <strong>the</strong>most common species in this genus.and much less is known about it than isknown about <strong>the</strong> rusts. GeneticVariability for resistance eXists. but nocomplete resistance is known. Genes forresistance from several sources.including species o<strong>the</strong>r than wheat.may have to be combined to achievesufficient resistance for <strong>the</strong> tropics.Currently. <strong>the</strong> most resistant lines arenot necessarily those of highest yieldpotential.Resistance to seedling blight causedby Sclerotium rolfsii-This fungus canbe particularly devastating in poorlydrained fields. Until recently. it wasassumed that <strong>the</strong>re was almost nogenetic resistance to it. and that seedtreatment or agricultural practices were<strong>the</strong> only solutions. However. recentpreliminary research in <strong>the</strong> Philippinesindicates some variability for resistance(D.A. Lapis. personal communication).Resistance tofusarium headscab-This disease is not restricted tohot environments. but can be verydevastating under warmer conditions.Genetic variability exists. andconsiderable research to pyramid genesfor resistance is being conducted inChina. Brazil and Mexico.These last three diseases are typical ofhot. humid conditions. Knowledgeabout <strong>the</strong>ir life cycle. host range andepidemiological behavior is limited. asare <strong>the</strong> techniques for working with<strong>the</strong>m. Artificial inoculation proceduresand storage and artificial multiplicationof spores must be fur<strong>the</strong>r studied beforemass screening of breeding materials ispossible.Resistance to aphids. stem borers andwaterlogging-These characters aremore important in hot climates than intraditional wheat areas. Aphids cancause direct feeding damage. and alsotransmit virus diseases. They havepreferences for certain varieties inexperimental plots. but it is not knownwhe<strong>the</strong>r <strong>the</strong>re is true resistance tofeeding. Little is known aboutresistance to stem borers and toleranceto waterlogging.This short overview reveals <strong>the</strong>existance of genetic Variability for mostcharacters. The breeder must combine<strong>the</strong>se characteristics into germplasmwith acceptable agronomic background.so that <strong>the</strong> farmer is assured ofreasonable yields every year. It is easyto breed for a single character whileneglecting <strong>the</strong> o<strong>the</strong>rs, but such a linewill never reach farmers' fields. Thecountry reports presented here shouldhelp in <strong>the</strong> understanding ofcombinations of characters needed for<strong>the</strong> various environments of <strong>the</strong> tropics.

32Yield-The last character to bementioned here Is yield. Althoughcorrelation with latitude Is not high. itIs certain that yield Is. generallyspeaking. reduced in <strong>the</strong> tropics. Thisfact. however. must be viewed in <strong>the</strong>context of earliness or maturity.Measured in production per day. a 100day crop of 2 t/ha in <strong>the</strong> tropicscorresponds to a ISO-day crop of 3 t/hain temperate zones. In many areas. thisforced maturity Is a major advantage ofwheat as it factlitates <strong>the</strong> grOwing ofasecond crop and sometimes even athird crop. It must also be rememberedthat <strong>the</strong> average yields of major wheatproducers such as Australia andArgentina were 1.2 and 1.5 tlha.respectively. for <strong>the</strong> 1979 to 1981period (4). What is most important forsmall farmers is <strong>the</strong> fact that smallmanagement mistakes. which wouldnormally cause minor yield reductionsin temperate climates. can lead tocomplete crop fallures in <strong>the</strong> tropics.AgroDomyAgronomic knowledge about wheatgrown in temperate environmentsneeds to be rechecked under hotclimate circumstances. The followingagronomic factors probably do notconstitute a complete list of <strong>the</strong>problems which will be encountered in<strong>the</strong> tropics.Weeds-Weed species are oftendifferent in <strong>the</strong> tropics. e.g.• volunteerrice in rice-wheat rotations. Highertemperatures may also cause <strong>the</strong> effectsof herbicides to be different.Ferttlizers-Fertilization Is generallyneeded. because tropical solls are oftenpoor in nutrients. The short growingseason but fast decomposition has to beconsidered in relation to basal versussplit applications.seed bed preparation-Special tnlagepractices may be necessary formoisture conservation. because ofwaterlogging problems or heavy solls.SoWing depth-Fur<strong>the</strong>r investigation isneeded here In relation to standestablishment and subsequent plantdevelopment.These factors are complicated by <strong>the</strong>strong interactions between <strong>the</strong>m andalso by nonagronomic factors. such asvariety and <strong>the</strong> socioeconomicconditions of <strong>the</strong> farmers grOwing <strong>the</strong>wheat.Seed productioDThe production of seed must receivespecial attention. since <strong>the</strong> seedmultiplication rate is slower undertropical conditions. because of reducedtillertng and generally lower yieldlevels. The short growing cycle. on <strong>the</strong>o<strong>the</strong>r hand. permits two crops per year.ifsuitable areas for off-season sowingcan be identified. This necessitatesmoving to high elevations. which areoften intensively cropped withvegetables or o<strong>the</strong>r high-value crops. orshipping seed between countries. whichcan be very expensive and involve agreat deal of logistical support.Seed .torageStorage Is a big problem in <strong>the</strong> tropics.especially under hot and humidconditions. Technical solutions suitablefor storage on-farm. in <strong>the</strong> village andat national levels would greatlyfactlitate <strong>the</strong> introduction of wheat Inmany areas. Grain storage is generallygiven high priority but. at harvest.many farmers do not know whe<strong>the</strong>r<strong>the</strong>y will use <strong>the</strong>ir grain for food or forseed. Therefore. <strong>the</strong> use of chemicalsfor pest control must be conSideredcarefully.NODtechDlcal problem.Previously. problems specific to tropicalconditions have been discussed. but <strong>the</strong>introduction of wheat Into a country

33requires more than technical solutions.The general aspects of introducing anew technology are thoroughlydiscussed in chapters 7 and 8 of Wheatin <strong>the</strong> Third World (5). There is atremendous task of education andinstitutional change which must beaccomplished. Technical personnelmust be trained for experimentstations. and researchers often have tobecome familiar with a crop <strong>the</strong>y havenever worked with before. Problemorientedresearch must be initiated for<strong>the</strong> specific needs of <strong>the</strong> tropics and <strong>the</strong>tropical farmer. Research findings needto be disseminated to farmers andhousewives through extension andagricultural schools.It wUl not always be easy to create aresearch budget for a new crop whosepotential has not yet been proven.Credit and marketing face <strong>the</strong> sameproblem. However. a technology cannever be developed unless <strong>the</strong>re is aresearch budget. The importance of<strong>the</strong>se nontechnical problems should notbe underrated. Lack of leadership. teameffort. training and institutionalstructure can hinder or completely stopevery technical innovation achievedthrough research.SummaryThe combination of strong nationalprograms and international cooperationhas demonstrated that wheat can begrown in <strong>the</strong> tropics. and that what isbeing attempted is not impossible.Efforts are being made to push back <strong>the</strong>limits of possible wheat-growing areas.Results to date have shown thatclimatic limitations are not impossibleto resolve. For <strong>the</strong> research objectivesfor wheat in <strong>the</strong> tropics. and with <strong>the</strong>limited funds available. care must betaken to consider all aspects which canlead to <strong>the</strong> overall goal.To gUide our thinking. let us use <strong>the</strong>symbol of a net hauling in a big harvestof wheat for <strong>the</strong> benefit of all. If onethread is broken or weak. some wheatmay be lost. but <strong>the</strong> o<strong>the</strong>r threads in<strong>the</strong> mesh can compensate for it to someextent. The whole catch may be lost.however. if <strong>the</strong>re are too many holes in<strong>the</strong> net. It is <strong>the</strong> task of everyoneinvolved in tropical wheat to identify<strong>the</strong> weak spots and get <strong>the</strong> holes closed;<strong>the</strong>se may be different for each country.The following country reports shouldpoint out what is currently being donein each of <strong>the</strong> national programs andwhat <strong>the</strong>ir strengths and weaknessesare.References1. CIMMYT. 1982. Results of <strong>the</strong>Eighteenth International SpringWheat Yield Nursery (lSWYN).1981-82. Mexico.2. CIMMYT. 1983 World Wheat Factsand Trends. Report Two: Ananalysis of rapidly rising ThirdWorld consumption and imports ofwheat. Mexico.3. Ootto. S.R.. C.A.B. Medieros.J.M.V. de Andrade and E.J.Iorczeski. 1984. A new wheatagricultural frontier at centralregion of Brazil. In Annual WheatNewsletter. vol. 30. P. 48.4; FAO. 1981. Production Yearbook.vol. 35. Rome. Italy.5. Hanson. H.. N.E. Borlaug and R.G.Anderson. 1982. Wheat in <strong>the</strong>Third World. Westview Press.Boulder. Colorado. USA. Pp. 83118.

34Wheat Breeding in Nor<strong>the</strong>ast ArgentinaI.R. Cettour. Chaco. aDd J.E. Nissi. Cordoba. Instltuto NacloDal deTecDologia Agropecaaria. ArgeDtiDaThe wheat-growing region of nor<strong>the</strong>astArgentina is located in <strong>the</strong> provinces ofChaco and Fonnosa between 25° and28°5 latitudes and 58° and 62°Wlongitudes (Figure 1). The climate issubtropical and has an average annualrainfall of800 mm in <strong>the</strong> west and1,100 mm in <strong>the</strong> east. with <strong>the</strong> greaterproportion falling in <strong>the</strong> spring,summer and early fall. The averagetemperature for January is 27.4°C. andfor July, 15.5°C. Frost causes damageto wheat if it occurs late in <strong>the</strong> year,during <strong>the</strong> heading stage. In <strong>the</strong> spring.<strong>the</strong>re are high temperatures: if <strong>the</strong>seare accompanied by north winds.shriveling of <strong>the</strong> grain can occur.In nor<strong>the</strong>astern Argentina. wheat isgrown under dryland conditions.Without fertilization. Crop growth is aresult of moisture accumulated in <strong>the</strong>soU before sowing, ra<strong>the</strong>r than ofrainfall. Wheat cultivation began toexpand in <strong>the</strong> region after 1962. when<strong>the</strong>re were approximately 5,000hectares: this area had increased to82,000 hectares by 1968. This was duein part to a severe drop in <strong>the</strong> price ofcotton, <strong>the</strong> principal crop of <strong>the</strong> area.This caused a divers1ftcation ofagriculture, and wheat was one of <strong>the</strong>crops that replaced cotton.Mter 1969. <strong>the</strong> area dedicated to wheatfluctuated greatly, as did productionand yield: this was caused by wea<strong>the</strong>rconditions. low prices and competitionAtlanticOcean"Jaure 1. The wheat-P'OwlDg reatoD of Dor<strong>the</strong>a.terD ArgeDtlna

3~from o<strong>the</strong>r crops. During <strong>the</strong> period1979 to 1983, an average of 24,000hectares was planted to wheat inChaco, from which 16,000 hectaresyielded an average of 1,200 kglha(Table 1). Approximately 4,500hectares were under wheat cultivationin <strong>the</strong> province of Formosa during <strong>the</strong>same period, with a yield similar to thatof Chaco.The marked decline in <strong>the</strong> area underwheat cultivation in <strong>the</strong> last few yearshas been due, in great part, tounfavorable wea<strong>the</strong>r conditions, suchas drought in some years, excessivehumidity in o<strong>the</strong>rs and late frosts.Never<strong>the</strong>less, in spite of <strong>the</strong>se adverseconditions, wheat remains <strong>the</strong> onlywinter crop which fits into <strong>the</strong> existingrotation patterns with <strong>the</strong> predominantrow crops of sorghum, cotton,sunflower and soybeans. Wheat is ofeconomic benefit to <strong>the</strong> farmers, as itbrings in income at an opportune timeof <strong>the</strong> year.Wheat production in nor<strong>the</strong>astArgentina is sufficient to meet <strong>the</strong> localdemand of <strong>the</strong> flour milling industry inChaco and nor<strong>the</strong>rn Santa Fe province.It is also possible to export some wheatto neighboring Bolivia, Brazil andParaguay, countries which representimportant markets for Argentineproducts.Wheat Research inNor<strong>the</strong>ast ArgentinaWhen wheat cultivation started in <strong>the</strong>early 1960s, <strong>the</strong> commercial varietiesused came from <strong>the</strong> traditional wheatgrOWingregions in <strong>the</strong> humid pampas.As <strong>the</strong>se varieties were not ideallyadapted to <strong>the</strong> conditions of <strong>the</strong> area,limited yields were obtained withconsiderable risk to <strong>the</strong> farmer.In 1972, because of <strong>the</strong> need to increasewheat production, a research programwas initiated to develop new varietiesfor <strong>the</strong> Chaco region, in coordinationwith <strong>the</strong> National Council for WheatPrograms. The objective of <strong>the</strong> programwas to investigate <strong>the</strong> productionproblems caused by <strong>the</strong> extremeenvironmental variation in <strong>the</strong> area,such as drought, late frosts, hightemperatures, low fertility and diseaseproblems.The specific objectives of <strong>the</strong> programwere:Table 1. Wheat area and production, Chaco • Develop varieties of high yieldprovince, Argentina, 1979 to 1984potential and broad adaptation;• Develop varieties of medium-to-IateArea Area Grainmaturity with good agronomic type;planted harvested yieldSeason (ha) (ha) (kg/ha) • Develop varieties with resistance tosteA rust (Pucctnia graminis tritici),1979-80 14,200 11,000 1,201 leaf rust (Pucctnia recondita tritict),1980-81 44,500 7,900 1,021 septoria leaf blotch (Septoria tritici),1981-82 11,600 11,100 1,562 glume blotch (Septoria nodorum),1982-83 33,500 32,100 929 diseases caused by Helmtnthosportum1983-84 16,600 15,650 1,295spp., scab (Fusartum spp.)and powdery mildew (Erystphegraminis trtttci);5-yearaverage 24,100 16,000 1,200 • Develop varieties with tolerance toshriveling, andSource: Chaco Extension Service andPlanning Office

,36• Produce grain of high industrial andcommercial quality for both nationaland international markets.Genetic variability was introduced as aresult of 200 crosses made each year inMexico and at <strong>the</strong> Marcos JuarezRegional Experiment Station inCordoba, using progenitors with goodadaptation for nor<strong>the</strong>rn Argentina.Individual selection from F2 to F4populations for disease resistance,agronomic characters, grain type andindustrial quality was conducted at <strong>the</strong>Presidencia Roque Saenz Peiia RegionalExperiment Station. Mass selectionswere made beginning with <strong>the</strong> FSpopulations.Shuttle breeding of F3 populations wasalso accomplished through <strong>the</strong> Balcarcesummer nursery at <strong>the</strong> BalcarceRegional Experiment Station, BuenosAires. The goals of this off-seasonnursery were:• Develop lines with better adaption;• Develop lines with resistance to stemrust;• Achieve homozygoscity in feweryears;• Evaluate advanced lines inpreliminary comparative yield trials;• Evaluate lines to be included inregional comparative trials at SaenzPefia and Colonia Benitez, as well asin various parts of <strong>the</strong> pampasregion;• Evaluate advanced internationallines for good agronomic charactersand disease resistance;• Evaluate commercial bread wheatvarieties through comparative yieldtrials at Saenz Pena, at ColoniaBenitez and Las Brenas ExperimentStations in Chaco, and at EI ColoradoExperiment Station in Formosa, and• Identify different biotypes(Virulences) of stem and leaf rust byobserving varietal differences at <strong>the</strong>various testing sites.ConclusionsThe cultivar Chaqueno Inta wasreleased as a result of this program; itspedigree is Son64-P4160E x CT244. Ithas high yield potential, intermediateto-latematurity, good agronomiccharacters, disease resistance and goodbread-making quality. Chaqueno Intaand Marcos Juarez [nta are <strong>the</strong>predominant cultivars grown innor<strong>the</strong>ast Argentina. O<strong>the</strong>r commercialvarieties adapted to <strong>the</strong> region areLeones [nta, Buck Pangare, CargillTrigal 800 and Klein Chamaco. Severaladvanced lines are almost ready forrelease and have shown increased yieldpotential over <strong>the</strong> best check varieties,have better disease resistance and haveacceptable industrial quality (Table 2).Potential areas for wheat cultivation inrotation with o<strong>the</strong>r crops have beendetermined, and an additionalsubtropical area in nor<strong>the</strong>ast Argentinahas been found to hold promise forwheat cultivation within a soybeanwheatrotation. This is <strong>the</strong> area ofTucuman, Salta and Jujuy in Santiagodel Estero province. At present, wheatis grown <strong>the</strong>re on only about 20,000hectares, but high yields have beenobtained under irrigation.

37Table 2. Advanced lines selected for high grain yield and disease resistance, PresidenciaRoque Saenz Pena Experiment Station, Chaco, Argentina, 1981 to 1983Grain Comparison to Disease resistanceAdvanced Yield best control score~/line (kg/ha) (%) Stem rust Leaf rust1981 Preliminary AdvancedComparative TrialsChaqueno Inta (control) 2787 100 50 10LANl SP. 3581 128.48 10 10LAN2 SP. 3393 121.74 10 10LAN3SP. 3243 116.36 5 51982 Preliminary AdvancedComparative TrialsChaqueno Inta (control) 1346 100 60 40LAN1 SP. 1953 145.09 20 10LAN2 SP. 1880 139.67 10 10LAN3 SP. 1706 126.74 10 51983 Production PlotsChaqueno Inta (control) 1760 100 40 30Marcos Juarez Inta (control) 1705 96.87 10 40Las Rosas Inta (LAJ2056) 1785 101.42 10 20LAJ2484 2140 121.56 20 20LANl SP. 2356 133.86 10 101982 Regional ComparativeYield TrialsChaqueno In18 1125 100 70 40LAJ2028 SP. 1495 132.88 20 10LAJ2395SP. 1320 117.33 30 301983 Regional ComparativeYield TrialsChaqueno Inta (control) 1660 100 30 20LAJ2548 SP. 2070 127.69 10 10LAJ2082 SP. 2070 124.69 10 20LAJ2395 1945 117.16 20 10~/ Scoring scale 0 to 100 (0-50 = moderately resistant, 51-100 = moderately susceptible)

38Wheat Research Efforts in <strong>the</strong>Abapo-Izozog Region of BoliviaJ.E. Abela. CorporacloD Gestora del Proyecto Abapo-Izozog. SantaCruz. BoliviaBolivia produces less than 20% of itswheat needs. as shown in Table 1.Mistaken production policies andconsumption incentives havecontributed to <strong>the</strong> increasing differencebetween <strong>the</strong> demand for wheat and itslocal production, and this unfavorabletrend is continuing (Table 2).Ninety percent of Bolivia's wheat isgrown in <strong>the</strong> traditional wheat-growingareas, located mainly in narrowmountain valleys. The great variety ofmicroclimates in <strong>the</strong>se areas fallbetween <strong>the</strong> follOWing values:• Mean temperature, 11 to 19°C• Rainy season, from December to Maywhen wheat is grownThe potential area for wheat productionis about 150,000 hectares. Today,approximately 60,000 hectares arecultivated; yield is less than 1 Uha.Greater use of inputs, such as fertilizer.herbicides, improved seed and a stablewater supply, could raise yield to over3 Uha. The adoption of this technology,however, is far in <strong>the</strong> future because of<strong>the</strong> high costs of irrigation systems andfertilizer.• Elevation, 1,500 to 3,000 meters• Annual precipitation, 350 to 700 mmTable 1, Wheat production and consumption in Bolivia,1976 to 1980VearProduction(000 tons)Consumption(000 tons)Consumptionlocally produced(0/0)1976197719781979198069.848.056.056.270.0256,3283.1376.9309.1371.62717151819Table 2. Annual growth rates in wheat production and consumption, Bolivia,1950-52 to 1978-80Period Production Imports Consumption Population(0/0) (0/0) (0/0) (0/0)1950-52 to 1958-60 7.87 3.64 4.89 1.911960-62 to 1968·70 0.28 3.88 2.721970-72 to 1978-80 2.43 2.87 3.02 2.091950·52 to 1978·80 2.78 4.39 4.11 1.89

39If Bol1via does not radically change itsfood consumption patterns, <strong>the</strong> countrywill have to put a great deal of effortinto <strong>the</strong> cultivation of wheat innontraditional areas, now considered asmarginal for wheat. These areas offermany advantages; land and water isavailable, climatic conditions areadequate for growing wheat andagronomic resources are available. Also.<strong>the</strong> land system lends itself to wheatcultivation.According to precipitacion regimes.<strong>the</strong>se nontraditional areas can bedivided into two regions:• Chaco region:400 to 800 mm of rainfall perannum10 to 150 mm dUring <strong>the</strong> seasonfor irrigated wheat• Nor<strong>the</strong>rn Santa Cruz region:800 to 1.700 mm of rainfall perannum200 to 450 mm dUring <strong>the</strong> seasonfor rainfed wheatIrrigation is projected for <strong>the</strong> Chaco. buthas been delayed due to <strong>the</strong> high initialinvestment necessary. Two big schemescould irrigate 150,000 hectares withsurface water. A ground-waterirrigation system currently is underdevelopment for 15,000 hectares, andan additional 2,ooo-hectare system isalso being considered for <strong>the</strong> ratnfedarea north of Santa Cruz. Irrigationcombined with available technologywould assure an average yield of 2 t1hafor <strong>the</strong> Chaco region. By 1988, it maybe feasible to grow 5000 hectares ofirrigated wheat in <strong>the</strong> Chaco.Planning for <strong>the</strong> nor<strong>the</strong>rn Santa Cruzregion includes <strong>the</strong> promotion of agradual increase in wheat area. It wouldbe grown as a winter crop, mainly onmedium to large-size farms. The fiveyeargoal for this region is 28,000hectares, with a yield of 1 to 2 Uha by1988.Bol1via expects to be prodUcing 80,000tons of wheat by 1990. with apossibtlity of reaching 120,000 tons.These amounts represent, respectively,17 and 26% of <strong>the</strong> estimated wheatdemand for that year (470,000 tons).ConclusionsHopefully, Bolivia can change its foodconsumption patterns to satisfy a largerpart of its carbohydrate needs through<strong>the</strong> use of foods more appropriate to itsenvironmental conditions, i.e., yucca,maize, potato and rice. In <strong>the</strong> longterm, wheat production w1ll principallybe carried out in <strong>the</strong> nontraditionalareas, <strong>the</strong> tropical and subtropicallowlands in <strong>the</strong> east. Therefore,research work on wheat for <strong>the</strong>senontraditional areas is of greatestimportance. Tables 3 to 6 summarizewheat research being conducted at <strong>the</strong>Coronel A. Gomez Experiment Stationin <strong>the</strong> Chaco region.

40Table 3. Wheat Research program, Coronel A. Gomez Experiment Station, Chaco, Bolivia, 1984YieldCrop rotationsuitabilityDiseaseQualityEfficiency andadaptabilityBreeding for:Plant type (1) Earliness (1)Rust resistance (1)Lodging (1)Shattering (1)Clean leaves (2)Rust resistance (1)Test weight (1)Grain texture (1)Grain weight (2)Wateruptake (3)Fertilizeruptake (3)Droughttolerance (3)Trials:Preliminary yield (1) Seeding date (1) Regional yield (2)Advanced yield (1)O<strong>the</strong>r activities:Varietyexchange (1)Seed increase (1)Seed distribution (3)Milling test (3)Baking test (3)(1) = in progress, (2) = beginning, (3) = in planning stageTable 4. Soil management and improvement program, Coronel A. Gomez ExperimentStation, Chaco, Bolivia, 1984FertilityPhysical soil characteristicsCompactionCrustingProductioncostsTrials:Fertilizerrate (1)Regionalfertilitymonitoring (2)Inoculants (2)Sulphurapplication (3)Implementuse (0)Manure and sodburyng (1)Tillage systems (1)Sand and sulphurappl ication (3)Tillagesystem (1)Sowing rate (2)Sowing depth (3)Sand and sulphurapplication (3)Reducedtillage (2)In use:Sad implantation (1)(0) = completed, (1) = in progress, (2) = beginning, (3) :::;: in planning stage

41Table 5. Water efficiency utilization program, Coronel A. Gomez Experiment Station,Chaco, Bolivia, 1984IrrigationTrials:Depth and frequencyof irrigation (1)Tillage system (1)In use:Siphon use (2)Field leveling (2)O<strong>the</strong>r activities:Flow efficiencyWeed control inin channels (3)Channel maintenance (1)Irrigation schedulingand efficiencyGround watersurveillance (0)Meteorologicalobservation (1)Water use survey (0)pF relations survey (3)(0) = completed, (1) = in progress, (2) = beginning, (3) = in planning stageTable 6. Crop management program, Coronel A. Gomez Experiment Station, Chaco,Bolivia, 1984Crop rotation Weed Productionsuitability Insect control control Stand costsTrials:Sowing date (1) Seedbed prepara- Herbicide Sowing rateAlternative tion to avoid use (3) (1)crops (2) insect carry- Bermuda and Tillageover from Johnson system (1)cotton crop (0) grass con- Fungicidecontrol (3) use (2)Sowingdepth (3)In use:Insecticide 2,4-0 use Appropriate Economicuse (1) (1) seed stor- evaluationage (2) in largerfields (1)(0) = completed, (1) = in progress, (2) = beginning, (3) = in planning stage

42Wheat Production in <strong>the</strong>Subtropical Areas of Santa Cruz, BoliviaC. Quintana, Centro de Investigaci6n Agricola Tropical, Santa Cruz,BoliviaBolivia needs 400,000 tons of wheat peryear to meet its total domestic needs.Unfortunately, present wheatproduction is not sufficient to satisfythis need. The subtropical areas of <strong>the</strong>country, such as <strong>the</strong> plains of SantaCruz province, offer a possible solutionin terms of prospects for wheatproduction expansion. This report willfocus mainly on <strong>the</strong>se subtropical areasof Santa Cruz.Wheat ProductionThe wheat area in nor<strong>the</strong>rn Santa Cruzis 10,000 hectares, but estimates forpotential wheat area in <strong>the</strong> region is160,000 hectares. In general, wheatcultivation is under rainfed conditions,with limited area under irrigation. Themain factors limiting production are:• Lack of aVailability of seed ofcommercial varieties• Lack of suitable technology forfarmers• Lack of moisture• Presence of diseases• Marketing, e.g., pricing restraints• Lack of credit for farmers• Agronomic problems such as weedsand low soil fertilityCharacteristics of <strong>the</strong>Subtropical ZoneRainfallFigure 1 shows <strong>the</strong> rainfall patterndUring <strong>the</strong> normal wheat cycle. It alsodemonstrates <strong>the</strong> problems duringplanting (May and June) and harvesting(September), due to excessive amountsof rainfall dUring those periods. Themean precipitation of <strong>the</strong> growing cycleover a 20-year period is 260 mm.Relative humidityData in Figure 2 give <strong>the</strong> 20-yearaverage relative humidity during <strong>the</strong>growing season. It ranges from 53 to73%, which favors diseasedevelopment.TemperatureFigure 3 illustrates <strong>the</strong> temperaturesdUring <strong>the</strong> growing season. based on aMay June July August SeptemberFigure 1. Rainfall during <strong>the</strong> wheat-growing season. nor<strong>the</strong>rn Santa Cruz,Bolivia (2o-year average)

4320-year period. Also indicated are <strong>the</strong>high temperatures during Septemberwhich. combined with <strong>the</strong> highprecip_tation of <strong>the</strong> area. providesfavorable conditions for diseasedevelopment. The average temperaturefor <strong>the</strong> season is 22°C. Table 1 presentsmonthly mean data for rainfall, relativehumidity and temperature.WindWheat is cultivated during <strong>the</strong> winter,when winds create ano<strong>the</strong>r problem forwheat cultivation. North winds aremore frequent and are more humid.frequently causing lodging of <strong>the</strong> crop.especially after heavy rain. Also, <strong>the</strong>ycause shattering of heads duringmaturity. South winds are strong. coldand wet. and can cause sterility ofspikes due to frost.DiseaseThe most prevalent diseasesencountered are spot blotch caused byHelmtnthosportum sattvum. leaf rustcaused by Pueetnta reeondtta, stemrust caused by Pueetnta graminls tritietand blotch caused by Septoria trttiel;root rots are also becoming important.?P-_sog70't:l~..c:: 60(l)~~ 60c:: :("L ,......__-~----"'T""---~~---~---May, IiiJune July August SeptemberFigure 2. Relative moisture during <strong>the</strong> wheat-growing season, nor<strong>the</strong>rnSanta Cruz, Bollvla (2o-year average)oMaximum--'~~ ~~....... ,'"",-.,.'... --...........,. Average-- .._--------- Minimum................ .............. .",................. .iMayiJuneiJulyiAugustG oFigure 3. Temperature range during <strong>the</strong> wheat-growing season, nor<strong>the</strong>rniSeptemberSanta Cruz, Bolivia (2o-year average)

44Commercial varietiesThe most commonly grown varieties in<strong>the</strong> area are QUimori, covering 60% of<strong>the</strong> area, followed by Saguayo (25%)and Jaral66 (15%). However, Quimoriand Jaral 66 are susceptible tohelminthosporium and will need to bereplaced in <strong>the</strong> near future.Wheat Improvement WorkThe Centro de Investigacion AgricolaTropical (CIAT) is encouraging wheatproduction in nor<strong>the</strong>rn Santa Cruz: <strong>the</strong>central experiment station is located inSaavedra. CIAT's wheat programobjectives for varietal improvement are:• Good agronomic type• High yield potential• Resistance to heat and drought• Earliness• Resistance to diseases. e.g.,helminthosporium• Good leaf hygiene• Good quality characteristics, such ashigh hectoliter weightYield trials are conducted 3#ipreliminary trials. advanced trials andregional trials.Agronomy research is carried out in <strong>the</strong>areas of:For plant protection, fungicides arebeing tested as possible controlmeasures for <strong>the</strong> prevalent diseases.Seed multiplication of <strong>the</strong> best varietiesis being given priority.The best advanced lines for adaptation.agronomiC type and disease resistanceare listed in Table 2. These lines arenow in advanced and regional trials tofur<strong>the</strong>r test <strong>the</strong>ir stability ofperformance in Sa{lta Cruz. Hopefully.one or more of <strong>the</strong>se lines will beoutstanding and can become areplacement for presently grownvarieties.Table 1. Mean rainfall, relative humidityand temperature for <strong>the</strong> wheat-growingseason, nor<strong>the</strong>rn Santa Cruz, Bolivia(20-year average)RelativeRainfall humidity Temperature (OC)Month (mm) (010) Min. Max. Avg.May 66June 63July 46August 29SEptember 567371645453171615161926242327302220202725• Fertilizer use• Seeding dates• Transfer of technology to farmersTable 2. Best wheat lines for adaptation, agronomic type and disease resistance,Santa Cruz, Bolivia, 1984Cross and pedigreeKVZ-TRM x PTM-AnahuacCM43903-H-2Y-1 M-4Y -OMKVZ-K4500-l-A-4SWM 176·3M-1Y-4Y·1 Y -1 M-oY-2PTZ-oYKVZ-K4500-l-A-4SWM 176-3M-1 Y -4Y·1 Y -1 M-OY-lPTZ-OYPato-Tobari 66Sapsucker"S"-Pato(R) x BluejayType of trial entry~AV-IAV-IAV·IAV-IAV-I

Table 2. (Con't)Cross and pedigreeNacozari F 76Veery No.5CM33027·F·1SM·500Y·OMBobwhite''S''CM33203-K·9M-9Y-4M-4Y-1 M-lY -oMBobwhite''S''CM33203-H-4M-1Y-QM·161B-QYTanager''S''CM30697-2M-8Y-3M-QYBR74.72-COCCM36889-31 Y-1OM-QYKalyansonalAlondra''S''CM39612.JK4·LV-9M-4MM-oMMButeoCM31070-Y-1Y-2M-2Y-oM-QMMJunco''S''CM33483-C·7M-1Y-QMF3.71-Torim F 73SWM5704-10Y-1M-3Y-3M-3Y-QB-2PTZ-QYAlondra''S''CM116B3-A-1Y-1M-1Y·13M-1Y-1Y·500Y-OMVeery''S''CM33027-F·12M-1Y·1 M-1Y·1 M-QY-60B-QY·1PTZ-QYBobwhite"S"~avon F 76CM61830·13Y-1 M-3Y.2M-4Y-OMGenaro F B1Ures T 81Seri 82Buckbuck''S''~VN''S''CM52359-12M·1Y-2Y-1M-QYTeeter''S''.Junco''S''CM59123-4M-1Y·1M-5Y-3M-QYNAC-Emu''S''/TOB(2)-7C x MN72131CM60402-Q-3Y·1 M-1 Y·1M-2Y-OMBobwhite''S''CM33203-G-SM-6Y-3M-'Y-1M-601PR·QPVeery''S''-Seri 82CM33027-F-15M-500Y-OM-87B-QYNeelkant''S''CM40454-33Y-4M·1 Y-OMPF70354-Alondra''S''CM47090-1M·1HlPR-1T·OTBluebird-Gatlo x C371IT. AEST. x Kalyansona-8luebirdCM34555-B-1 M-4Y·1 M·1 Y-1M-1Y-OMType of trial entryPAV·IPrelPrelPrelPrelPrelPrelPrelPrelIBWSN'84IBSWN'84IBSWN'84IBSWN'84IBSWN'84HSN'84IBWSN'84,HSN'84HSN'84HSN'84HSN'843rd LACOS3rd LACOS3rd LACOS3rd LACOS3rd LACOSJ,/ AV-I = advanced yield trial;Prel = Preliminary yield trial-; IBWSN'84 = 16th InternationalBread Wheat Screening Nursery, CIMMYT, Mexico; HSN'84 = HelminthosporiumScreening Nursery, CIMMYT, Mexico; 3rd LACOS = Lineas Avanzadas del Cono Sur,CIMMYT, Sou<strong>the</strong>rn Cone, South America

46Wheat in Costa RicaC.A. Salas, Estacion Experimental Fabio Baudrit Moreno,Universidad de Costa Rica, AlaJuela, Costa RicaThe economic crisis which at present Isaffecting Costa Rica has producedadverse effects in several areas of vitalimportance, one of which is <strong>the</strong>insufficient production of basic foodproducts in relation to <strong>the</strong> level ofnational consumption. This has madenecessary <strong>the</strong> importing of foodsupplies to assure <strong>the</strong> country of itsbasic food needs. The high cost of <strong>the</strong>prime materials for agriculturalproduction, and <strong>the</strong> lack of adequatecredit at <strong>the</strong> time when it is mostneeded to stimulate agriculturalproduction, have been considered <strong>the</strong>principal reasons for this situation.The wheat situation is still morecritical, since Costa Rica dependsabsolutely on imports for this cereal;this amounts annually to 100,000 tonsat a cost of US$ 22.909,507 (¢1 billion).This corresponds to a per capitaconsumption of 31.7 kg, which provides14.5 and 21.8% of <strong>the</strong> calories andproteins of <strong>the</strong> Costa Rican daily diet,respectively. It is for this reason thatincreased wheat production couldeliminate an important part of <strong>the</strong>foreign exchange drain.Crop Feasibilityseveral wheat production feasibilitystudies have been carried out throughfleld experiments, and results havebeen considered positive. The areasconsidered appropriate for plantingwheat in Costa Rica are located in <strong>the</strong>central valley, mainly Tierra Blanca,Sanatorio Duran, Oreamuno and Cot, aswell as in Cartago province. Theseareas are between 1,600 and 2.800meters elevation, and have a rainfall of600 to 800 mm during <strong>the</strong> wheatgrowingcycle. Geographically, <strong>the</strong>areas are situated around 9°56'Nlatitude and 83°52'W longitude, withmaximum and minimum averagetemperatures of 19.4 and 8.6°C,respectively. Planting occurs during <strong>the</strong>months of October and November, andharvest, in <strong>the</strong> month of March.Yields of 10 t/ha have been obtainedexperimentally, and 7 t/hacommercially. However, moreexperimentation is necessary to offerreal encouragement to <strong>the</strong> wheatfarmer. In addition, adequate sources ofcredit, appropriate farm machinery ando<strong>the</strong>r indispensable conditions areneeded to make wheat growingattractive to <strong>the</strong> farmer. ResolVing <strong>the</strong>seissues could significantly reduceimports of wheat, with <strong>the</strong> consequentreduction of foreign exchangeexpenditure and, at <strong>the</strong> same time,open new opportunities of employment,which are badly needed in Costa Rica tocounteract unemployment and <strong>the</strong>present economic crisis.Recommended Areasfor ExperimentationThe central and nor<strong>the</strong>rn areas ofAlajuela province of Costa Rica arerecommended for experimentation inwheat production. In central Alajuela,altitude fluctuates between 840 and1,800 meters, with rainfall of 600 to800 mm dUring <strong>the</strong> vegetative cycle.Planting time is September, andharvest, December. In <strong>the</strong> nor<strong>the</strong>rn partof <strong>the</strong> province, planting time is inNovember. and harvest, in Februaryand March.Geographically, central Alajuela issituated around 10 0 01'N latitude and84° 16'W longitude and. in <strong>the</strong> north.<strong>the</strong> suitable areas of Fraijanes andZarcero lie around 10° l5'N and84°l4'W. The maximum andminimum average temperatures,

47respectively. for central AlaJuela are28.2 and 17.SoC and. for <strong>the</strong> north.21.2 and 19.9°C.Production trials would also be possiblein <strong>the</strong> lowlands (Guanacaste andPuntarenas provinces). provided wheatvarieties appropriate for <strong>the</strong> tropicswere available: <strong>the</strong>se are zones withhigher temperatures. Never<strong>the</strong>less.limitations exist to <strong>the</strong> possibility ofestablishing wheat production in CostaRica. among <strong>the</strong>m <strong>the</strong> lack of bothgovernment policy decisions andtechnical research.Aspects of GovernmentPolley DecisionSeed ayallabWt,.The National Seed Office. whichsupervises and authorizes seedproduction. relies upon privateenterprise and <strong>the</strong> National ProductionCouncil for multiplying and processingseed. It would seem advisable. in <strong>the</strong>case of wheat. to guarantee <strong>the</strong>availability of certified seed of selectedreleased varieties.MarketingThe public entity which has <strong>the</strong>responsibility of purchasing local grainshould guarantee a market for <strong>the</strong>wheat and a price equivalent to that ofimported wheat. This would prOVide <strong>the</strong>necessary stimulus to farmers to grow<strong>the</strong> new crop.BUlk creditThe Banking Commission whichadvances money to farm~rsshouldestablish a fund for wheat growers. as<strong>the</strong>y have done for <strong>the</strong> o<strong>the</strong>r basicgrains. and assure that <strong>the</strong> necessaryresources are available to finance wheatproduction.Crop iD.urlUlceThe National Insurance Institute.through its crop insurance department.should guarantee protection to <strong>the</strong>wheat farmer against unexpected.unfavorable climatic conditions andoutbreaks of insect pests and plantdiseases which may cause losses.Farm machiDeryThe lack of appropiate farm machineryadapted to <strong>the</strong> topographic conditionsof <strong>the</strong> central valley. such as speciallydesigned planting. mowing andthreshing machines and binders. hasbeen one of <strong>the</strong> major factors inrestricting <strong>the</strong> expansion of wheatproduction. In o<strong>the</strong>r countries. such asItaly. Japan and Taiwan. adequatemachinery exists for <strong>the</strong>se activities. InGuatemala. in localities which aresimilar to those of Costa Rica(Quezaltenango and Chichicastenango).almost half of <strong>the</strong> wheat needed fornational consumption is beingproduced using such farm machinery.In <strong>the</strong> begining of a national wheatproduction program. an official entity.such as <strong>the</strong> National ProductionCouncil. should provide specializedfarm machinery serVice. as has beendone with o<strong>the</strong>r crops on variousoccasions. thus helping to assure <strong>the</strong>farmers' success in growing wheat.Research PrioritiesWheat research has been carried out inthree areas in Costa Rica (Figure 1).Three experiment stations are utilized(Tables 1. 2 and 3).SOU.From a fertility point of view. <strong>the</strong> soils inFraiJanes are <strong>the</strong> most problematical.with extreme acidity. trace amounts ofphosphorus. high phosphorus-fixingcapacity. high aluminum content andvery low presence of calcium.magnesium and potassium (less thanS meqll00 g soil). In order to obtaingood crop responses to phosphorusfertilization. it is usually necessary toapply P20S at 600 to 800 kgIha. anamount which is not economical. Limingis also very important for <strong>the</strong>se soils.

48However, in field experiments withwheat, certain lines and cultivars haveshown a better response to normalfertUization than o<strong>the</strong>rs, probably dueto better adaptability to low-fertility andlow-pH soil conditions. It is importantto select <strong>the</strong>se cultivars, as well as o<strong>the</strong>rcrops such as barley and triticale, forbetter adaptability to Fraijanes soils.Weed controlWeed incidence is high in <strong>the</strong> threeareas where wheat research work hasbeen conducted, Cartago and centraland nor<strong>the</strong>rn Alajuela. In centralAlajuela, gramineous, cyperaceous andbroadleaf weeds prevail and, in Cartagoand nor<strong>the</strong>rn Alajuela, <strong>the</strong> broadleaf .weeds are dominant.Allelopathy and o<strong>the</strong>r factors due toweed competition have been consideredreasons for crop yield reduction, as aresult of Rottboellta exaltata andCyperus rotundus in central Alajuela.Considering solely weed competition.<strong>the</strong> gramineous weeds Eleusine indica.Digitaria spp.• Cynodon dactylon,Ixophorus unisetus and Paspalumpaniculatum have been shown to be<strong>the</strong> most important. Pennisetumclandestinum. Taraxacum offlcinale.Bidens pilosa, Amaranthus hybridus,Melampodium divaricatum andSpergula arvensis are considered to beimportant weeds in Cartago andnor<strong>the</strong>rn Alajuela.At present, <strong>the</strong> alternatives for chemicalcontrol of weeds seem to be Oic1ofopmethyland herbicides that inhibit <strong>the</strong>development of some hormone-inducedhydrolytic enzymes (hormonals).Oic1ofop-methyl is used to control somegramineous species, and <strong>the</strong>hormonals, broadleafand cyperaceousweeds. 2,4-0 or MCPA is used forpostemergence. and Perfluidone, forpre-emergence treatments. Linuron hasalso been used for broadleaf preemergencecontrol.8683l1---~~r------::!~"'~~~--r---1~---r----AtlanticOceanFraixines (1.650m)• I ,.•Fabio Baudrit Moreno r840m)10-----+-4lC'----~iiliI!=l~----=:....:....:~::...-=.==:::.:.;:....:.;.:~~....:...:.~::.:.:..-• Santiago Duran(2.337m) ~~~~~9-----.j-------+------.j--H.----+-....IIIIiI~----PacificOceanFigure 1. Wheat research centers In Costa Rica, 1984

49Table 1. Climatological data, Fraijanes Experiment Station, Alajuela,Costa R ica~JAverage Average Hoursmaximum minimum Relative ofMonth temperature temperature Rainfall humidity sunshine(oC) (oC) (mm) (°/0)January 20.6 12.2 98.6 87.1 8.2February 21.3 12.2 33.9 84.6 8.7March 22.1 12.1 60.1 85.1 7.2April 21.7 12.5 140.2 83.5 6.6May 21.6 13.3 456.0 93.0 4.4June 21.7 13.4 416.0 92.1 3.3July 21.1 13.7 263.9 89.1 3.9August 21.4 13.1 403.9 87.5 4.1September 21.5 13.1 486.9 89.7 3.6October 20.9 13.0 609.1 92.4 3.3November 20.2 13.1 333.8 90.2 4.4December 20.3 13.0 100.2 87.7 6.4!./ Latitude lO o 15'N, elevation 1,650 mNormal wheat planting time, October or November, normal wheat harvestingtime, February or MarchAverage yield of five best advanced lines, 2,857 kg/haTable 2. Climatological data';Jbio Baudrit Moreno Experiment Station, SanJosecito, Alajuela, Costa Ric aAverage Average Hoursmaximum minimum Relative ofMonth temperature temperature Rainfall humidity sunshine(oC) (oC) (mm) (°/0)January 28.7 17.1 7.6 69.2 8.5February 29.6 16.9 12.0 67.9 9.4March 30.4 17.6 13.0 67.4 8.7April 30.3 17.9 66.4 70.5 7.9May 28.7 18.1 272.0 80.3 5.9June 27.2 18.0 309.5 87.2 4.9July 27.5 17.9 212.7 82.5 4.7August 27.5 17.6 285.6 84.2 5.0September 26.9 17.5 336.6 88.0 4.9October 26.7 17.4 312.5 88.4 5.0November 27.0 17.4 138.1 81.9 5.6December 27.9 16.9 34.1 73.9 1.5!./ Latitude 10 0 1'N, elevation 840 mNormal wheat planting time, September to November, normal wheat harvestingtime, December to MarchAverage yield of five best advanced lines, 4,728 kg/ha

50The use of hormonals cannot always berecommended, due to <strong>the</strong> largenumbers of horticultural crops in <strong>the</strong>wheat-production areas. Moreinvestigation is needed to avoidspraying when and where a drift of finespray or vapors may come in contactwith nearby sensitive crops orornamental plants.There is an urgent need to plan for amajor, continuing weed controlprogram, instead of <strong>the</strong> isolated fieldtrials which have been conducted sofar.Disease controlIn central Alajuela, <strong>the</strong> diseases withmost frequent incidence are zonateeyespot (Helminthosporiumgiganteum), H. trttici repentts andcrown rot (Fusarium spp.). In trialscarried out with CIMMYT materialsduring 1978, <strong>the</strong> triticales proved moretolerant to leaf blotch caused byHelminthosporium spp. under naturalinfection than did <strong>the</strong> wheats.In both central and nor<strong>the</strong>rn Alajuda,when grain maturity and high humiditycoincide, head scab (Fusarium spp.)and saprophytic fungi make <strong>the</strong>irappearance and negatively affect yield.In <strong>the</strong> Cartago area (Sanatorio Duran), ahigh natural incidence of leaf rustappeared in a commercial planting ofSiete Cerros. This permitted <strong>the</strong>determination of <strong>the</strong> reaction of severalcultivars of wheat and one triticalewhich had been introduced fromCIMMYT. The introduced cultivars wereCananea (Tel), Bobwhite, Anza,Nacozari 76, Pavon 76 and Veery 1.With <strong>the</strong> exception of Nacozari 76, <strong>the</strong>cultivars showed tolerance, withinfections of not more than 5% ofPucctnia recondtta. The virus diseaseknown as alfalfa yellow dwarf has alsoappeared, but is found in low incidence.It is absolutely necesary to continueworking, with <strong>the</strong> valuable cooperationof CIMMYT, for new sources ofgermplasm with resistance to <strong>the</strong>se ando<strong>the</strong>r diseases.Table 3. Climatological d~anatorio Duran Experiment Station, TierraBlanca, Cartago, Costa Ri aAverage Average Hoursmaximum minimum Relative ofMonth temperature temperature Rainfall humidity sunshine(oC) (oC) (mm) (°/0)January 19.4 8.4 58.1 87.2 3.9February 19.8 8.4 18.3 82.8 4.5March 19.7 8.5 13.9 81.6 4.5April 19.6 8.9 62.1 83.8 4.2May 19.7 8.7 228.0 85.8 3.0June 19.3 8.5 323.8 86.3 2.3July 19.1 8.8 193.3 87.0 2.2August 19.3 9.0 187.8 87.6 2.8September 19.4 8.8 338.2 88.0 2.9October 19.3 8.6 419.8 89.4 2.6November 19.3 8.6 213.7 91.6 2.4December 19.1 8.3 102.8 88.6 2.9!/ Latitude 9 0 56'N, elevation 2,337 mNormal wheat planting time, October, normal wheat harvesting time, MarchAverage yield of five best advanced lines, 7,593 kg/ha

51Wheat Research in <strong>the</strong>Coastal Region of EcuadorJ. Tola, Small Grains Program, InstitutoNacional de Investigaciones Agropecuarias, Quito, EcuadorThe slopes and small plateaus of <strong>the</strong>highlands of Ecuador (2.500 to 3.200meters altitude) are <strong>the</strong> traditionalwheat-growing areas. In 1964. when90.000 hectares of wheat were grown inEcuador. <strong>the</strong> country was stillimporting 50% of its wheat needs. Atthat time. scientists at <strong>the</strong> NationalInstitute of Agricultural Research(lNIAP) decided to investigate <strong>the</strong>possibilities of growing wheat on <strong>the</strong>coast. Two major objectives wereestablished:• To increase <strong>the</strong> wheat-growing areain Ecuador. and• To obtain an additional croppingseason each year for breedingpurposes.In <strong>the</strong> beginning. three testing locationswere selected at INIAP experimentalcenters. They were chosen to represent<strong>the</strong> most common environments of <strong>the</strong>Ecuadorian coastal region (Table 1).From 1964 to 1969. more than 1.000homozygous lines were tested during<strong>the</strong> two tropical seasons. <strong>the</strong> rainyseason and <strong>the</strong> dry season. By 1969. itwas clear that. with <strong>the</strong> germplasmavailable. it was not possible to growwheat under wet conditions. Pooragronomic type and high incidence ofFusarium spp. and Erysiphe graminis.as well as weed and insect damage.were <strong>the</strong> main problems. The bestresults in germplasm adaptation wereobserved at tropical. dry Portoviejo.Some lines were also fairly well adaptedin <strong>the</strong> dry season at <strong>the</strong> intermediatezone of Pichilingue. However. attropical and humid Santo Domingo.even in <strong>the</strong> driest months of <strong>the</strong> year.few plants formed grain and almost allwere killed by Fusarium spp. Problemswere simUar at Pichilingue during <strong>the</strong>rainy season. but yield improved to amean of 1.0 Uha when <strong>the</strong> same lineswere planted during <strong>the</strong> dry season.Some additional dry sites prOVidedenough information to conclude thatwheat plants had improved tillering andgrain development and less diseaseincidence when <strong>the</strong>y were plantedduring <strong>the</strong> drier months (Table 2).Research efforts were concentrated atPortoviejo and several o<strong>the</strong>r locationswith simUar conditions. SegregatingTable 1. A comparison of climatic conditions in three coastallpcations, EcuadorLocationSanto Domingo Pichilingue PortoviejoClimatic

52materials (F2 to FS generations) wereintroduced, and <strong>the</strong> yield potential insome materials was aceptable (Table 3).During this period, research was alsoconducted on planting date, plantdensity, fertilization, weed control andwater requirements. Some of <strong>the</strong> resultsare presented in Tables 4 and 5.Results showed that <strong>the</strong> dry seasonoffered better opportunities for growingwheat. Appropriate seeding rate wasfound to be from 140 to 160 kg/ha, and<strong>the</strong> optimum economic fertilizer dosage,80 and 40 kg/ha of nitrogen andphosphorus, respectively. Acceptableweed control was obtained with amixture of Fluorodifen (1.5 kg a.1.1ha)plus Linuron (0.5 kg a.1.1ha).Among <strong>the</strong> diseases, rusts were not aproblem dUring <strong>the</strong> dry season, exceptthat stem rust was observed in latetillers. For wet locations, Fusarium spp.and Erysiphe spp. were <strong>the</strong> mostimportant diseases, causing spike andgrain damage. In 1976, some spots ofdead plants, in different vegetativestages, were observed; <strong>the</strong> causal agentwas Sclerotium rolfsit. The diseasespread very qUickly from 1977 to 1979,killing SO, 60 and 85%, respectively, of<strong>the</strong> germplasm under evaluation.ConclusionsIn 1979, <strong>the</strong> National Cereal Programdecided to terminate research on wheatfor <strong>the</strong> coastal areas after considering<strong>the</strong> serious limitations for <strong>the</strong> growth ofwheat in that area. The most importantreasons for this were:• The low comparative economicreturn as compared to local crops;• The lack of irrigation systems, whichwould be imperative for growingwheat in dry areas of <strong>the</strong> Ecuadoriancoast;• The relatively low yield potential(4 Uha), compared to <strong>the</strong> potential for<strong>the</strong> highlands (6 Uha);• The cost of wheat production perhectare, which on <strong>the</strong> coast is twicethat of <strong>the</strong> highlands, and• The Sclerotium rolfsit problem, aswell as <strong>the</strong> potential insect, diseaseand weed competition problemsforeseen once farmers start plantingwheat.These problems would require major,costly research programs in breedingand agronomy.Table 2. Comparative wheat yields, wet anddry seasons, Portoviejo, Ecuador, 1964 to1969YearWet season(March-May)Yield (kg/ha)Dry season(June-8ept)1964196519661967196819691100120019501730270rft./230()!./2400380032003400A./ Planting date: April and May

53Table 3. Average yield of best wheat lines, P~rtoviejo, Ecuador, 1974 to 1978Yield (kg/ha)Lines/varieties 1974 1975 191E)!.1 1971!./ 1918~/OCEPAR 73008NP-824Bluebird-Gallo x Carpintero"S"/PAV''S''AlondraChenab 70NP-832RumiiiahieSonora 64!./ Sclerotium rolfsii damageQ./ Different testing site in same region4200394026403980 1020 3153900 980 26037503750385035601000820740620740320180200315310Table 4. Average grain yield for Sonora 64 under different dosages ofnitrogen and phosphorus, Portoviejo, Ecuador, 1973 to 1975Nitrogen Yield Phosphorus Yield(kg/ha) (kg/ha) (kg/ha) (kg/ha)o 2640 0 264020 2770 20 307040 2880 4o!./ 311060 2950 60 29208o!./ 3080 80 2970100 3110 100 3020120 3110 120 3105160 2900 160 2790!./ Economic dosage44104100420041204120380039002900Table 5. A comparison of herbicide application and yield, Portoviejo Experiment Station,Ecuador, 1975 to 1977HerbicideDosage (kg a.iJha)1915 1976 977Yield (kg/ha)Application time 1975 1976 1977!./Fluorodifen 3.0Fluorodifen + Linuron 1.5 +0.5Fluorodifen +Diuron 1.5 +0.52,4-0 (a) 0.75CheekQ./4.0 3.01.5 +0.5 2.0 +0.42.0 +0.40.50Pre-emergencePre-emergencePre-emergencePost-emergenee(tillering)2940281519001750520870 2603844 2651801700430 220!./ Severe Sclerotium rolfsii damageQ/ No herbicide application

54Selection and Introduction of Wheat Typesfor Subtropical Conditions in MexicoJ.J. Martinez, Wheat Research Program, Centro de InvestigacionesAgricolas del Noroeste-INIA, Ciudad Obregon, Sonora, MexfcoWheat is <strong>the</strong> third most importantcomponent. after maize and beans, in<strong>the</strong> Mexican diet. Wheat is cultivatedon about 850,000 hectares, with anaverage yield of 4.3 tons per hectare. In<strong>the</strong> fall-winter cycle of 1981-82. <strong>the</strong>rewas a record production of 4.3 milliontons. This amount was sufficient tosupply national demand; however, dueto Mexico's rising population, it isestimated that annual nationalconsumption will be over 6 million tonsby <strong>the</strong> year 2000.Over half of Mexico's wheat is producedin <strong>the</strong> state ofSonora in <strong>the</strong>northwestern part of <strong>the</strong> country.Sonora has an altitude of less than 100meters above sea level; its climate isdry and <strong>the</strong> principal plant life iscomposed of cactus and thorny shrubs.The winter is mild, lending itself to <strong>the</strong>production of spring wheat. The highestyield is obtained on irrigated lands,with advanced methods of cultivation.The major limiting factors are plantdiseases, principally leaf rust (Pucciniarecondita), which limits <strong>the</strong> commerciallife of a variety to three to five years,The use of improved varieties with highyield and resistance to this pathogen isnecessary for maintaining wheatproduction at a high level in <strong>the</strong> region.Wheat Production inSubtropical MexicoIt is difficult to continue to increaseyield in Mexico at <strong>the</strong> accelerated ratethat was possible in <strong>the</strong> past; <strong>the</strong>genetic potential within <strong>the</strong> wheatspecies has already been largelyrealized. Therefore. to satisfy <strong>the</strong> futuredemand for wheat, it will be necessaryto open up new lands for cultivation.The subtropical areas in Mexico,located between 20° and 24° Nlatitudes, with an altitude of less than500 meters and irrigation and soilsadequate for wheat cultivation, coveran area of apprOXimately 200,000hectares. These areas are locatedprinCipally in <strong>the</strong> San Lorenzo Valley insou<strong>the</strong>rn Sinaloa state and in <strong>the</strong>Huasteca area in <strong>the</strong> state ofTamaulipas on <strong>the</strong> coast of <strong>the</strong> Gulf ofMexico. Winters in <strong>the</strong>se areas are lesssuitable for wheat production, becauseof high temperatures at <strong>the</strong> beginningof <strong>the</strong> planting season. Present varietieshave poor tillering capacity and givepoor yields; never<strong>the</strong>less, it has beenpossible to obtain yields of up to 4 t1ha.During <strong>the</strong> 1983-84 season, a series oftrials was conducted to test <strong>the</strong> effectsof subtropical environments on wheatproduction. They were carried out in<strong>the</strong> Culiacan and San Lorenzo valleysin Sinaloa and in <strong>the</strong> Santiago Ixcuintlaregion of Nayarit. Results showed thatwheat yields decreased considerably(from 7082 kg/ha to 722 kglha) whenlatitude and temperatures were lessfavorable for wheat production (Table1). However, in <strong>the</strong> San Lorenzo Valley,which is considered as subtropical, <strong>the</strong>average yield of commercial varieties in<strong>the</strong> trial was 3148 kg/ha; that ofSantiago Ixcuintla, where <strong>the</strong>temperature regime is marginal forwheat, was only 700 kg/hat Thediseases found to be common under<strong>the</strong>se conditions was leaf rust and leafspot caused by various forms ofhelminthosporium. Since wheatcultivation in <strong>the</strong>se areas is new, yieldcan be substantially improved throughbetter agronomic practices. Plantingdate and sowing density. fertilizermanagement and insect and weedcontrol are some of <strong>the</strong> factors thatneed fur<strong>the</strong>r research.

Selection of Wheats forSubtropical EnvironmentsFor <strong>the</strong> past several years. a cooperativeprogram for <strong>the</strong> genetic improvement ofwheat has been conducted by INIA.Mexico. and CIMMYT at <strong>the</strong> CIANOexperiment station in Ciudad Obregon.Sonora: <strong>the</strong> objective has been <strong>the</strong>development of germplasm tolerant tohigh temperature and drought. Thestrategy utilized has been that of <strong>the</strong>selection of early generations in <strong>the</strong>Yaqui Valley of Sonora. These materialsare sown early in October whentemperatures are high (23°C meantemperature). Irrigation is applied atgermination and again. after 72 days. atflowering. Individual plant selection ispracticed with regard to agronomic typeand disease resistance. Advancedgenerations are evaluated in subtropicalenvironments. in sou<strong>the</strong>rn Sinaloa andcentral Tamaulipas. As a result of <strong>the</strong>setrials. <strong>the</strong> experimental lineBuckbuck"S"-PVN"S" has beendeveloped. In subtropical San LorenzoValley. its yield has been 3630 kg/hat15% above <strong>the</strong> mean of presentcommercial varieties.ConclusionsAs a result of research in MeXico. it ispossible to obtain wheat yields of morethan 4 Uha under subtropicalenvironments. It is necessary to fur<strong>the</strong>rimprove <strong>the</strong> yield potential ofcommercial varieties for <strong>the</strong>se areasthrough breeding. Selection must bemade for high yield and better toleranceto high temperature and diseases. Thetrials must be conducted underappropriate types of environmentalconditions.Wheat yields in <strong>the</strong> subtropics can alsobe improved substantially by improvingagronomic practices. especially suchfactors as planting date and density.fertilization and insect and weedcontrol.Wheat cultivation in San Lorenzo.Sinaloa. and <strong>the</strong> Huasteca inTamaulipas. covering an area of about200,000 hectares in a subtropicalclimate. represents a productionpotential of approximately one milliontons of wheat annually. 19% ofMexico's entire annual production.Table 1. Yields of selected commercial varieties in <strong>the</strong> traditional wheat-growing areas of<strong>the</strong> nonhwest and three subtropical environments of MexicoYield (kg/ha)NorthwestSubtropical environmentsYaqui Valley Culiacan San Lorenzo SantiagoVariety Valley Valley ValleyUres 81 7,300 6,700 3,100 700Sonoita 81 7,200 4,500 1,900 400Seri 82 7,000 6,100 3,900 900Glennson 81 6,900 5,700 2,900 800Genaro 81 6,900 6,000 3,700 600Mean 7,100 5,800 3,100 700

56Wheat Production Status, Constraintsand Research Priorities in NigeriaA.M. Falaki, Institute for Agricultural Research,Ahmadu Bello University, Zaria, NigeriaWith <strong>the</strong> steady rise in income,consumption of wheat in Nigeria hasrecently increased considerably.Surveys show that <strong>the</strong> eating of breadhas spread, even to rural areas. In1982, consumption of wheat wasestimated at an average of 60 gramsper person per day (22 kg/year), withmajor towns averaging 210g/person/day (77 kg/year). In terms of<strong>the</strong> drain on <strong>the</strong> nation's foreignexchange. it has been estimated that, in1982, wheat and wheat flour importsinto Nigeria totaled 1.425 million tons.valued at USS 290 million (Table 1).The bulk of <strong>the</strong> wheat now grown in<strong>the</strong> country is on irrigated land. Thearea under wheat cultivation is about15,000 hectares. yielding on average2.5 to 3 t/ha. At present. <strong>the</strong> totalproduction of wheat is about 40.000tons, which is eqUivalent to about 2.6%Table 1. Wheat and wheat flour imports,Nigeria, 1973 to 1982Year1973197419751976197719781979198019811982Quantity(000 tons)304.0323.4407.5732.4719.7800.6928.01000.02352.01452.0Cost(million US$)42.577.682.5147.3144.6162.3187.2205.4277.1290.0Source: Nigeria Trade Summary (197382), Federal Office of Statistics,Lagos, Nigeriaof <strong>the</strong> country's requirements; Nigeria'scurrent annual wheat needs are inexcess of 1.5 million tons.From <strong>the</strong> consumption and productionstatus. it is obVious that <strong>the</strong>re is a biggap between supply and demand ofwheat in Nigeria. In an effort to arrest<strong>the</strong> dWindling foreign reserve position,to which <strong>the</strong> importation of wheatcontributes. Nigeria has embarked on aprogram of wheat cultivation in areaswhere growth conditions for <strong>the</strong> cropare suitable. As a result. <strong>the</strong>government has decided to put 50% of<strong>the</strong> irrigable land under wheatcultivation in <strong>the</strong> nor<strong>the</strong>rn Guinea andSudan savanna areas of <strong>the</strong> country(estimated at 345,000 hectares whenfully developed).Constraints toWheat ProductionLandLand is <strong>the</strong> most critical constraint onwheat production in Nigeria. Since <strong>the</strong>crop is grown under irrigation. only <strong>the</strong>limited land cleared and developed forirrigation by <strong>the</strong> various governmentmanagedriver basin projects isavailable for wheat cultivation. Unless<strong>the</strong> government accelerates <strong>the</strong>expanSion of <strong>the</strong> irrigation schemes.land will remain a major constraint onwheat production, since local farmersare in no financial position to developland for irrigation.TemperatureWheat is grown almost entirely during<strong>the</strong> harmattan period (November toFebruary), when night temperatures-aresufficiently low for adequate tillering.The main factor which prevents <strong>the</strong>extension of <strong>the</strong> crop southward in

Nigeria is high temperature. South oflatitude looN. between November andFebruary. maximum temperatures areconsistently above 32.5°C andminimum temperatures are mostlyabove 15°C. These temperaturesreduce <strong>the</strong> length of <strong>the</strong> growing seasonand yield potentials.InputsThe inputs necessary for wheatproduction are also lacking or in shortsupply in most instances.Fertilizers-Shortages of adequatesupplies of fertilizer dUring <strong>the</strong> plantingperiod has posed a problem to wheatfarmers. Unfortunately. <strong>the</strong> plantingtime of <strong>the</strong> crop coincides with <strong>the</strong>period when all of <strong>the</strong> importedfertilizers have been exhausted onrainfed crops. Thus. lack of initialsupplies of required nutrients reducesvigor and. subsequently. yield.Labor-The planting season for wheatin Nigeria overlaps <strong>the</strong> period whenlate-harvested. rainfed crops (sorghum.cowpea and cotton) are harvested.Since most operations (except landpreparation) are carried out manually,labor shortages tend to pose someproblems. as labor is needed forharvesting <strong>the</strong> rainfed crops. delaying<strong>the</strong> planting of wheat. Late-plantedwheat is known to yield up to 25% lessthan timely sown crops.Machinery-Most of <strong>the</strong> major landpreparation operations (except plantingand fertilizer application) are carriedout by machines from <strong>the</strong> governmentorganizedtractor hiring units (THU).After harvesting <strong>the</strong> rainfed crops.farmers await <strong>the</strong>ir turn to get <strong>the</strong>irland prepared for wheat. But, forseveral reasons. such as insufficientnumbers of tractors. inadequate spareparts and lack of operators. <strong>the</strong> farmers'fields are more often than not preparedlate. Also. during <strong>the</strong> harvesting of <strong>the</strong>crop. a lot of wheat is lost throughdamage by early rains owing to aninadequate number of threshers.Water managementDuring <strong>the</strong> wheat-growing season. <strong>the</strong>reis practically no rainfall to support <strong>the</strong>crop. An average of about 6 mm ofwater per day is lost throughevapotransporation during <strong>the</strong> cropgrowingseason. This warrants <strong>the</strong> needfor regular irrigation. At present.irrigation is scheduled on <strong>the</strong> basis oftime interval (5 to 10 days). dependingon soil type.This approach has not beensatisfactory. especially when bordercheck and basin methods of irrigationare employed; it results in excessivewater loss. Since water is a scarceresource. irrigation has to be scheduledto maximize wheat production per unitof water applied. An improvement inirrigation management is reqUired if <strong>the</strong>country is to achieve its target of700.000 tons of wheat per annum by1990.Fertilizer useMost of <strong>the</strong> work conducted on fertilizeruse in relation to wheat crops in Nigeriahas been confined to <strong>the</strong> three majornutrients. nitrogen. phosphorus andpotassium, and <strong>the</strong>ir optimum rate.timing and method of application. Theneed for balanced fertilization foroptimum wheat production on <strong>the</strong>savanna soils cannot be underestimated.No information is yetavailable on micronutrients. With <strong>the</strong>passage of time. a deficiency of <strong>the</strong>senutrients may arise. <strong>the</strong>reby limiting<strong>the</strong> production of <strong>the</strong> crop. especiallyunder intensive cultivation.Research PrioritiesThe federal government of Nigeria ispresently committed to increasingwheat production locally. It has.<strong>the</strong>refore. been encouragingcoordinated research projects between<strong>the</strong> Institl,lte for Agricultural Research.Samaru and <strong>the</strong> various River Basin

Authorities involved in wheatproduction. Generally. <strong>the</strong> areas ofresearch given priority include watermanagement and fertilizer use.Water maaagemeatThe successful production of wheat.especially in a semi-arid. tropicalenvironment like nor<strong>the</strong>rn Nigeria. isdependent on a judicious irrigationprogram. based on knowledge of <strong>the</strong>effect of soil moisture stress on <strong>the</strong>crop. When water constitutes <strong>the</strong>limiting resource. research efforts mustbe directed towards:• Finding <strong>the</strong> best scheduling method.quantity and time of irrigation for<strong>the</strong> wheat crop;• Investigating <strong>the</strong> effect of variablewater stress on late-planted wheat.since <strong>the</strong> effect of stress can varyaccording to <strong>the</strong> maturity of <strong>the</strong>variety and time of seeding, and• Discovering <strong>the</strong> effect of fertilizationon water-use efficiency of wheat.Fertilizer useFrom a report submitted by acommittee that reviewed research workon fert1l1zer use in irrigated agriculture,<strong>the</strong> follOWing research areas are beinggiven priority in relation to wheatfertilization:• Potassium requirements of wheatunder different irrigation regimes,and• Micronutrient requirements of wheat.ConclusionsNigeria's current annual wheatrequirements are in excess of 1.5m1llion tons annually. Present localproduction is about 40,000 tons. whichis equivalent to about 2.6% of <strong>the</strong>nation's needs. Increased production isthus a challenge for both <strong>the</strong>government and <strong>the</strong> farmer.The government should accelerate <strong>the</strong>expansion of projected irrigationschemes, and ensure timely landpreparation and provision of inputs tofarmers. Research work in progress onefficient water management, fertilizeruse and o<strong>the</strong>r suitable productiontechnologies should be adquatelyfunded, as <strong>the</strong>se w1ll help increasewheat production per unit area. It isestimated that, with efficient watermanagement and good cropmanagement practices coupled withfarmer experience in wheat cultivation,crop yields could exceed 4 tlha. In thiscase, <strong>the</strong> government wheat productiontarget of 700,000 tons per annum couldbe realized by <strong>the</strong> year 1990.• Interaction of phosphorus with o<strong>the</strong>rmajor nutrients and with irrigationfrequency;• Phosphorus availab1l1ty/fixation inwheat under intensive. irrigatedagriculture;

59Wheat Production in Bangladesh:Its Constraints and Research PrioritiesA.B.S. Hossain, Bangladesh Agricultural Research Institute,Joydebpur,Dhaka,BangladeshWheat production in Bangladesh hasincreased substantially since 1975.both in tenns of production area andyield (Table 1). Wheat is now cultivatedon about 570.000 hectares. with aproduction of one million tons. Before1975. little wheat was grown and <strong>the</strong>varieties were low yielding (0.8 tlha).disease susceptible. tall and latematuring. Total production was onlyabout 0.1 million tons. When <strong>the</strong>perfonnance of semidwarf. highyieldingvarieties was found to besatisfactory. an ambitious wheatprogram was initiated in 1975-76 byimporting seeds of high-yieldingvarieties (HYV) from India to replaceTable 1. Wheat production in Bangladesh,1967-68 to 1982-83Year1967-681968-691969-701970-711971-721972-731973-741974-751975-761976-771977-781978·791979·801980-811981-821982-83Area(ha)77,800117,300119,900126,000127,300120,200123,500126,100150,100160,000188,900264,700433,200591,200534,412567,000Averageyield Production(t/ha) hons).744 57,900.786 92,200.862 103,305.872 109,000.899 113,195.745 89,500.884 109,200.911 114,8701.430 214,7001.596 255,4001.813 342,5001.971 486,2001.869 809,7001.8191,075,2001.776 949,0001.8701,061,000local varieties. Fifty-nine percent of <strong>the</strong>150.000 hectares planted that yearwere planted with HYV. Production wasapproximately doubled. from 114.000tons in 1974·75 to 215.000 tons in1975-76. Within five years. <strong>the</strong> wheatarea increased about five times andproduction. about nine-fold. At present.HYV occupy 98% of <strong>the</strong> area underwheat cultivation.Reasons for SuccessThe introduction of high-yieldingvarieties and <strong>the</strong> adoption oftechnologies for better managementand seed preservation. generatedthrough research in <strong>the</strong> mid-1970s.helped Bangladesh to become a wheat·growing country. Fanners wereinterested in growing HYV when <strong>the</strong>yobserved three to four times more yieldas compared to local varieties; also.wheat could be grown more easHy inresidual soH moisture or under partiallyirrigated conditions. As compared toboro rice cultivation. three to four timesmore land could be irrigated with <strong>the</strong>same amount of irrigation water. Thecost of cultivation was less. along withreduced problems of weed competition.disease and insect pests.Wheat is sown in <strong>the</strong> winter months•from mid-November to mid-December•and is harvested in mid-March. Duringthis period. most of <strong>the</strong> lands hadpreViously been idle. after <strong>the</strong> harvestof transplanted and broadcast amonrice. Fanners are using this opportunityto grow wheat as an additional crop onthis type of land. There is no problemfor growing <strong>the</strong> subsequent crop. juteor aus rice. after <strong>the</strong> harvest of wheat.Source: Bureau of Statistics, Governmentof Bangladesh, Dhaka, Bangladesh

60Although rice is <strong>the</strong> staple food inBangladesh. <strong>the</strong> country has long beenimporting wheat to make up its fooddeficits. Wheat flour is consumedprimarily as chapatis (handmade flatbread). bread in loaves and pastries.The dietary habit of <strong>the</strong> people haschanged considerably. and wheat hasnow become a desirable foodsupplement to rice.The extension service took an activerole in prOViding wide publicity on howto cultivate high-yielding varietiesthrough field demonstrations onvarieties. fertilizer rates and sowingtime. and through organizing blockfarms in irrigated areas. Researchfindings and recommendations werealso communicated to growers throughbooklets, leaflets. field days. radiobroadcasts and o<strong>the</strong>r audiovisualmeans.Seeds were made available throughcontinued imports, and local seedproduction was also streng<strong>the</strong>ned by<strong>the</strong> Bangladesh AgriculturalDevelopment Corporation (BADC) on<strong>the</strong>ir farms and on contract growers'fields. Farmers were advised to preserve<strong>the</strong>ir own seed in sealed kerosenecontainers. biscuit tins. diesel or petroldrums, thick polyethylene bags orear<strong>the</strong>n pitchers. About 80% of <strong>the</strong>total requirement for seed is metthrough farmers' stocks and salesamong <strong>the</strong>mselves.The Department of Food procured grainfrom growers at support price (a littleover <strong>the</strong> market price fixed by <strong>the</strong>government at <strong>the</strong> time of harvesting)so that. during <strong>the</strong> peak sale period. <strong>the</strong>price did not fall too much. Somecredits and loans were also proVidedthrough commercial banks for <strong>the</strong>purchase of inputs. such as fertilizerand irrigation equipment, to boostproduction.Production ConstraintsAccording to <strong>the</strong> Bangladesh SoUSurvey report. about 3.1 millionhectares of land are physically suitablefor wheat cultivation. Currently. <strong>the</strong> netarea available for wheat is about 1.5million hectares, after leaVing land foro<strong>the</strong>r winter crops. It has been observedthat, since 1980-81, <strong>the</strong>re has been nofur<strong>the</strong>r expansion of wheat cultivation,and a number of practical reasons existfor this fact. The potential area for <strong>the</strong>expansion of wheat is <strong>the</strong> land availableafter <strong>the</strong> harvest of transplanted amonrice. Amon rice is harvested inDecember. when soil moisture is <strong>the</strong>main limiting factor for <strong>the</strong> germinationof seeds. Irrigation facilities exist forabout 30% of <strong>the</strong> land and, ifamon riceproduction is affected by flood ordrought, many farmers prefer to growboro rice in <strong>the</strong> irrigated areas.SuffiCient seed of short-durationvarieties cannot be prOVided. AsBangladesh farmers prefer white grain,<strong>the</strong>re is always a heavy demand forwhite-grained varieties, especiallySonalika because of its goodperformance under late-seedingconditions.Threshing is a big problem. Farmers donot yet have effective, low-cost, smallscalethreshing equipment. All wheat isthreshed ei<strong>the</strong>r by trampling withbullocks or by beating with sticks. Theonset of early monsoon rains frequentlydestroys many harvested crops. Somecompetition from o<strong>the</strong>r winter crops,such as mustard and lentils, existsnow. because of <strong>the</strong> high market priceof <strong>the</strong>se crops. Also, <strong>the</strong> wheatprocurement price has not kept pacewith <strong>the</strong> increased price of fertilizer andseed. Due to <strong>the</strong>se problems, farmersare not encouraged to bring more areasunder wheat cultivation.

61Research PrioritiesVarietal developmentResearch on high-yielding varieties ofwheat was initiated a few years before<strong>the</strong> independence of Bangladesh, butsystematic research was initiated onlyin 1971, with <strong>the</strong> scheme entitled <strong>the</strong>Accelerated Wheat Research Program.This program was based on <strong>the</strong>development of germplasm and ofpersonnel; CIMMYT provided help inboth areas. Initially, promising varietiesselected from international nurserieswere recommended for commercialcultivation and, simultaneously,agronomic requirements of <strong>the</strong> varietiesand seed storage practices were madeavailable to <strong>the</strong> growers.Varieties now under cultivation includeSonalika (60 to 70%), followed byINIA 66 (10 to 15%); o<strong>the</strong>rs grown areTanori 71, Jupateco 73 and Pavon 76.The farmers' preference for Sonalika isdue to its short maturity period (100 to105 days), attractive large white grainand wide adaptation under bothirrigated and dryland conditions; it isespecially suitable for late seeding.However, Sonalika is now susceptible toleaf rust and leaf blotch diseases.Balaka, a white-grained variety,recommended in 1979 for late seedingunder dryland and partially irrigatedconditions, is now in cultivation (198384 season). Four new varieties, Ananda,Kanchan, Akbar and Barkat. werereleased in 1983 and are in a seedmultiplicationprogram. They areresistant to leaf rust and moderatelyresistant to o<strong>the</strong>r foliar diseases andhave a 10 to 20% yield advantage overSonalika. It is hoped that <strong>the</strong>se varietieswill soon replace Sonalika.The breeding materials from nationaland international programs are beingevaluated. The superior genotypesselected from international sources areentered into <strong>the</strong> national program. Atpresent, about 400 single and topcrosses are made annually. Individualplant selections are also made underBangladesh conditions from <strong>the</strong>segregating F2 spring x winter andspring x spring crosses, including <strong>the</strong>F2 helminthosporium nursery materialreceived from CIMMYT.Since <strong>the</strong> majority of <strong>the</strong> wheat area israinfed, tolerance to drought andresistance to leaf rust and o<strong>the</strong>r foliardiseases, especially leaf blotch causedby H. sattvum, is of primaryimportance. Emphasis is being placedon <strong>the</strong> follOWing areas:• Evolve short-duration varieties,similar to Sonalika in maturity, withpost-an<strong>the</strong>sis tolerance to heat andsuitable for late plantings after <strong>the</strong>harvest of transplanted amon rice;• Develop varieties with high yieldpotential for optimum seeding dates(mid to late November), suitable fordryland and irrigated situations;• Evolve juvenile heat-tolerantvarieties suitable for late October orearly November planting, especiallyfor improved tillering ability underhigh temperatures;• Develop varieties suitable forsemisaline soils, which are found invast areas and are lying idle in <strong>the</strong>sou<strong>the</strong>astern and southwestern partsof <strong>the</strong> country;• Develop varieties tolerant to <strong>the</strong> lowpH of some areas, and• Develop durum wheat varietieswhich can improve <strong>the</strong> quality offoods. such as sUji, semolina andnoodles, which are now beingprepared from bread wheats.

82Agronomic practicesMuch attention is needed in agronomicresearch. Cultivation techniques for arice-wheat cropping pattern must bestudied in regard to <strong>the</strong> effects oftillage, soU moisture conservation andwater management. For transplantingrice, soU is puddled with a woodencountry plow that creates a strong plowpan in some soUs; this is a barrier topenetration by wheat roots. It causes<strong>the</strong> crop to be more susceptible tomoisture stress or. if irrigated, createswaterlogging and a lack of normal plantdevelopment. Conservation of soUmoisture by appropriate tUlage methodsis also necessary for rainfed areas.Research should be streng<strong>the</strong>ned forrefining fertUizer recommendations.especially for potassium. and studies onmicronutrients. such as sulfur. zinc.Icopper and manganese. should beundertaken. Mixed cropping orintercropping with o<strong>the</strong>r winter crops isa practice followed. and this must beconsidered in all its ramifications.Post-harvest technologyResearch on farm-level seed and grainstorage needs fur<strong>the</strong>r attention. Lowcostthreshing devices must bedeveloped to resolve <strong>the</strong> presentthreshing problem.ConclusionsIn 1981. <strong>the</strong> Canadian InternationalDevelopment Agency (CIDA) providedgrants to streng<strong>the</strong>n <strong>the</strong> existing wheatresearch programs carried out byBangladesh in cooperation withCIMMYT. It is hoped that. as a result ofthis cooperative research program.Bangladesh will be able to close itsrecurring food gap (1.5 to 2 mUllontons) by increased wheat production.

63Wheat Improvement Programsfor <strong>the</strong> Hotter Parts of IndiaJ.P. TandoD. Wheat Program.Indian Agricultural Research Institute. New Delhi. IndiaWheat is <strong>the</strong> most important coolseasonfood grain crop of India. During1983-84. wheat was cultivated on morethan 22 million hectares. producingabout 45 mUlion tons of grain. Thisrepresents a tremendous increase over<strong>the</strong> 6.46 mUlion tons of wheat grainproduced in 1950-51. During thisperiod. <strong>the</strong> productivity per hectare hasincreased from 663 kglha to more than1.800 kglha. The increased productivityis attributable partly to better irrigationfacilities and <strong>the</strong> increased use offertilizer; <strong>the</strong> major factor. however. is<strong>the</strong> popularization of high-yieldingdwarf wheats which have enabledefficient utilization of <strong>the</strong> createdresources. The figures for area.production and productivity over <strong>the</strong>period since Indian Independence aregiven in Table 1.The major wheat-growing states arePunjab. Haryana. Uttar Pradesh.IMadhya Pradesh. Rajasthan. Bihar.GUjarat. Maharashtra and West Bengal.Area production and yield per hectarein various wheat-growing states areshown in Table 2.Among <strong>the</strong> important wheat-growingstates. wheat in Karnataka.Maharashtra and Madhya Pradesh isgrown in a typical hot. tropical climate.In considerable areas of Gujarat. Bihar.West Bengal and Assam. wheat is alsocultivated in a fairly hot climate. Themaximum and minimum temperaturesduring <strong>the</strong> wheat crop season at fourlocations representing typical wheatgrowingareas of <strong>the</strong> country arepresented in Figure 1; averagetemperatures are presented in Figure 2.It is clear from <strong>the</strong>se figure that wheatis grown primarily in <strong>the</strong> coolestenvironments in <strong>the</strong> hills. followed by<strong>the</strong> northwestern parts of <strong>the</strong> country;in <strong>the</strong> east and south it is cultivatedunder much higher temperatures.Ano<strong>the</strong>r aspect which is clear from<strong>the</strong>se figures is that temperatures arehighest at times of planting andTable 1. Wheat area, production and yield, India, 1946-47to 1982-83Area Production VieldVear (000 ha) (000 tons) (kg/ha)1946-47 10,120 6,232 6161951·52 9,471 6,182 6531956-57 13,424 9,403 6951961-62 13,750 12,072 8901966-67 12,832 11,393 8871971-72 19,139 26,410 13801976-77 20,922 29,010 1387 41981-82 22,308 37,8331982-83 23,OOO~.I 42,500~.I1696 /1847!.!./ EstimatedSource: Area and Production of Principal Crops in India

84maturity in most parts of India. In fact,wheat growth duration in various partsof <strong>the</strong> country is determined bytemperature limits.Agronomists and physiologists havefound that, for <strong>the</strong> planting of wheat,average temperatures should be around20 to 22°C. They have also found thatgrain development is adversely effectedif <strong>the</strong> average temperature exceeds25°C. These temperature limitsrepresent <strong>the</strong> limits of crop growthduration. The spring wheats, which arecommonly grown in India, seem to becapable of adjusting <strong>the</strong>ir growthduration to <strong>the</strong>se temperature variations.It is interesting to note that appropriatetemperatures for sowing are reached atmore or less <strong>the</strong> same time throughoutIndia, and <strong>the</strong> recommended dates forplanting are also similar for all partsexcept <strong>the</strong> hills, where <strong>the</strong>y are earlier.Days to flowering offive widely adaptedwheat genotypes in some of <strong>the</strong>representative parts of <strong>the</strong> country aregiven in Table 3, shOWing how <strong>the</strong>number of days is inversely related totemperature.It is obvious from this table that cropduration is reduced to less than half in<strong>the</strong> extremely hot temperatures ascompared to <strong>the</strong> cooler climate of <strong>the</strong>hills. O<strong>the</strong>r unfavorable effects of hightemperature include:• Reduced crop stand;• Rapid entry into <strong>the</strong> reproductivephase, leading to very earlyflowering;• . Reduced tillering due to inadequatevegetative growth;• Reduction in grain size (physiologistshave estimated that <strong>the</strong>re is a 10 to15% reduction for every 5 to 6degree rise in temperature above24°C);• Dessication of <strong>the</strong> leaves;• Changes in disease and pestprevalence patterns, and• ~Low yield.Table 2. Wheat area, production and yield in important wheat-growingstates, India, 1981-82Area Production YieldState (Iakh ha)!.! Uakh tons) (kg/ha)Assam 1.02 1.16 1130Bihar 17.44 25.69 1473Gujarat 7.04 14.07 2000Haryana 15.62 36.82 2357Himachal Pradesh 3.54 4.30 1216Jammu and Kashmir 1.98 2.04 1032Karnataka 3.42 2.30 674Madhya Pradesh 32.93 32.74 994Maharashtra 11.28 9.88 876Punjab 29.17 85.53 2932Rajaithan 17.73 29.42 1660Uttar Pradesh 78.49 128.83 1641West Bengal 2.13 3.0.2 1417Total India 223.08 378.33 1696!of 1 lakh = 100,000

65In India, a series of wheat varieties havebeen developed that have yieldpotential, under tropical conditions,which are comparable to those in o<strong>the</strong>rparts of <strong>the</strong> country. Some of <strong>the</strong>important recommended varieties forareas where wheat is grown underrelatively hotter climates are:• Nor<strong>the</strong>ast-Sonalika, UP262, K7410,HPl102, HP1209, UP1l5, HUW55,HUW206. HUW213• Central regions-Kalyansona, J24,WH147, Lok·l, HD2236, HP2278,Swati, SUjata, Raj 1555(d), A206(d),• Peninsular regions-NI5439,HD2189, Kalyansona, DWR39,HD2278, Melvika(d), N59(d),MACS1967These varieties show normal plantdevelopment when grown underrecommended cultural practices. One of<strong>the</strong> few major deviations from normallyrecommended cultural practices is for<strong>the</strong> peninsular zone, where wheat isgrown under <strong>the</strong> hottest temperaturesin <strong>the</strong> country; <strong>the</strong>re it is recommendedthat <strong>the</strong> seed rate be increased from <strong>the</strong>normal 100 kglha to 125 kg/hat363025201510C) - 50~::se 8.40s~36302lS20m10ISNorthwest (Ambala), ~" ,:" I:...... " -' ..''. '.. ,'l'\"e.. ''. ---_ .........:l...... ...............................Nor<strong>the</strong>ast (Patna)'.. ," , ~,'" "...... ".. " ...•.•.... "", ,' .....e., • __--' .., .... ~.... .............................-. .....Northwestern hills (Bhowali). ~.... _-......... "......-.. _....-...'".........._---............... ..-. ........ .".......................', ,.,.,.,._-_ .. -_ ~~ --Maximum--_. Average········MinimumSouth (Annigeri)Oct Nov Dec Jan Feb Mar Apr Oct. Nov Dec Jan Feb Mar AprFigure 1. Temperature variations during <strong>the</strong> wheat crop season In variousregions of India

66In <strong>the</strong> central and peninsular parts of<strong>the</strong> country. wheat is cultivated underrainfed conditions. In most of India.although <strong>the</strong> monsoon rains end byabout <strong>the</strong> middle of September. wheatcannot be sown until <strong>the</strong> end of Octoberor <strong>the</strong> beginning of November, whentemperatures make seeding possible.During <strong>the</strong> intervening period. <strong>the</strong>re issevere loss in soil moisture. A numberof cultural practices are recommendedto conserve moisture but. in manyfields. moisture levels in <strong>the</strong> upperlayers become so depleted thatachieving good plant stands becomesalmost impossible.None of <strong>the</strong> improved varieties iscapable of being sown earlier thannormal. as such sowing leads to severehigh temperature symptoms. In recentyears. attempts have been made toidentify genotypes which show aminimum of adverse effects from hightemperatures when wheat is seededearly. Some of <strong>the</strong>se are Hindi 62. Raj1771. Raj 1777. HIlOll. HIl012 andVL616. These varieties possess somesort of temperature insensitivity and donot show reduced tillering or decreasedvegetative phase. and <strong>the</strong>y give goodplant establishment and growth. Thesematerials are being used as sources fordeveloping superior strains for earlySOWing. In fact. VL616 has recentlybeen recommended for early sowing in<strong>the</strong> hills; however. high temperaturesare not a serious constraint <strong>the</strong>re. Themain purpose of its release is to escapefrost damage to floral parts. which isacute if ears emerge dUring <strong>the</strong> verycold temperatures of December toFebruary. Most of <strong>the</strong> improvedvarieties show early ear emergencewhen planted prior to <strong>the</strong> end ofOctober. even in <strong>the</strong> hills. In <strong>the</strong>development of VL616. one of <strong>the</strong> genesgoverning vernalization response hasbeen exploited to regulate entry into <strong>the</strong>reproductive phase when severe coldhas passed.High temperatures during grain fillingpose ano<strong>the</strong>r constraint to wheatproduction. although crop duration inmost parts of <strong>the</strong> country is so adjustedthat it matures before extremelyunfavorable temperatures are reached.However. a sudden rise in temperatureprior to normal maturity is a widelyprevalent phenomenon in almost allparts of <strong>the</strong> country. Such erratic rises- 30 Co)o-----------_.....~'=:::::::--... ------- .........-............::..- .. __ Annigeri ............ ....-...... ..._--- .._-------------' .../........ ......~ ...... p ...."...._..................-atna....-..- .._ ..- ..-.- A bal..-.."-..--............ m a .-..--....-. -.. ..-- --..- ..- ..- BhowaIiOct Nov Dec Jan Feb Mar AprFigure 2. Average temperatures during <strong>the</strong> wheat crop season in variousregions of India

67in temperature are capable of causingconsiderable reduction in grain yield.Some differences among genotypeshave been recorded. but this aspectneeds fur<strong>the</strong>r research. especially from<strong>the</strong> point of view of heat·tolerantgenotypes and <strong>the</strong> incorporation of thischaracteristic into improved varieties.Table 3. Days to flower for five wheat cultivars in four locations in IndiaDays to flowerAlmora. Hissar. Pusa. Dharwar.Variety Uttar Pradesh Haryana Bihar Mysore(cool) (cool) (fairly hot) (hot. tropical)Sonalika 114 93 71 46HD2285 121 101 78 47HD2329 119 102 80 ~gWH147 121 102 80 48Raj 1555 121 101 78 47

68Wheat Research and Production in PakistanM.A. Bajwa, Ayub Agricultural Research Institute, Fatsalabad,PakistanWheat is <strong>the</strong> staple food of <strong>the</strong>inhabitants of Pakistan; its strawconstitutes an integral part of <strong>the</strong> dailyration for livestock. Spring-type breadwheat (T. aestivum L.) is <strong>the</strong> mostcommon species grown in <strong>the</strong> tenwheat-production zones of <strong>the</strong> country,while some durums are also cultivatedin a very limited area, mainly in <strong>the</strong>rainfed area. The cultivation of wheat isspread throughout four provinces. Themajority of both wheat-growing areaand production is found in <strong>the</strong> provinceof Punjab (72% of each), with smalleramounts in Sind (14 and 17%,respectively), Northwestern FrontierProvince (11 and 8 %) and Baluchistan(4 and 3%).Bread Wheat ImprovementWork for <strong>the</strong> improvement of wheatwas initiated in <strong>the</strong> country as early as1883, and a number of varieties (T9,T11, 8A, 9D. C518. C591, C250, C217,C228, C271 and C273) were releasedfrom time to time until <strong>the</strong> mid-1950s.The wheat program was, however,revolutionized by <strong>the</strong> release of <strong>the</strong> firstsemidwarf, fertilizer-responsive, diseaseresistantwheat variety Mexipak 65 in1965. This variety almost doubled <strong>the</strong>yield of <strong>the</strong> old tall local wheats. Sincethat date, 30 bread wheat varieties havebeen released for different wheatgrOWingareas of Pakistan.Although remarkable improvement hasbeen made in wheat production, yieldper unit area is still lower than that ofmany developing and developedcountries of <strong>the</strong> world. This paper dealswith improvements made in inputresources, future wheat requirements,<strong>the</strong> various constraints causing <strong>the</strong>yield gap, breeding efforts for stablizingand enhancing production and futureresearch strategies.Improvement in InputResources and VarietiesDuring <strong>the</strong> 1970-71 season, <strong>the</strong> wheatgrOWingarea in Pakistan increasedfrom 6 to 7.1 million hectares. seeddistribution rose from 8.32 to 50.14thousand tons and water availabilityper hectare of land from 24.69 millionacre feet (MAF) to 39.07 MAF,compared to <strong>the</strong> previous season.Between 1971-72 and 1980-81,fertilizer use per hectare of arable landincreased from 31.6 to 74.21 kglha, andcredit distribution from USS 0.43 to25.47 million.The combination of <strong>the</strong> release ofimproved varieties with this increase ininputs has led to an increase in wheatproduction of 192%, from 3.81 milliontons in 1960-61 to 11.15 million tons in1982-83. Yield has increased 107%,from 822 to 1,707 kglha.Population andWheat RequirementsFor 1985, <strong>the</strong> projected population forPakistan is 92.97 million, and wheatproduction. 12.67 million tons; 12.81million tons of wheat would be requiredfor that population. Self-sufficiency inwheat was attained in 1981-82, before<strong>the</strong> expected time, due to bumpercrops. However, this marginal selfsufficiencymay be disturbed by naturalhazards at any time; <strong>the</strong>refore.concerted efforts are needed tomaintain <strong>the</strong> tempo of increasedproduction to meet <strong>the</strong> futurechallenge.Yield GapA substantial yield gap has beenobserved between yield at <strong>the</strong>experiment stations and on farmers'fields in each province. This gap is

69primarily due to a lack of finances on<strong>the</strong> part of <strong>the</strong> majority of farmers forimplementing modern technology forwheat production. Thus, <strong>the</strong>re is greatscope for improving wheat productionand yield in <strong>the</strong> country.CODstraints to ProductionLike many developing countries, wheatproduction is confronted with bothbiophysical constraints (disease,fertilizer, water, seed, varieties, culturalpractices and salinity/sodicity) andsocioeconomic constraints (credit,knowledge, experience, tradition andinstitutions).DiseaseAlthough several diseases attack wheat,<strong>the</strong> most important are stripe and leafrusts, loose and flag smuts, Kamal bunt.powdery mildew, helminthosporium leafspots and foot and root rots. O<strong>the</strong>rdiseases,such as those caused bySeptoria spp., downy mildew, blackpoint and black chaff, are of minorimportance. The major thrust in <strong>the</strong>breeding program at present is todevelop wheat varieties which areresistant or tolerant to <strong>the</strong> principaldiseases. Measures to minimize <strong>the</strong>iradverse effects on production are alsobeing investigated. The reactions ofcommercial wheat varieties to importantdiseases are shown in Table 1.Table 1. Reactions of commercial wheat varieties to six diseases, PakistanDisease reaction.NYellow Leaf Loose Flag Powdery CompleteVariety rust rust smut smut mildew buntBlue Silver S S S S S SBarani 83B/ MR-MS MR-MS S R SIndus 79 MS MS S S SBahawalpur 79 MS-S MS-S S S SLU26 S MS-S S MR RLyallpur 73 S S S S S SPARI73 MS-S S S S S SSandal MR-S S S MR S SSonalika MS-S S S S SPunjab 81 MS-S MR S S SPakistan 81 MR MR S S RFaisalabad 83B/ R R S MR SArz MR-MS MR S S SZamindar 80 MR-MS MS S S SZargoon 75 MR S S S SKhyber 79 MR-MS SJauhar 78 S SSarhad 83~/ R RKohinoor 83 ~/ R R S S S.J./ S = susceptible, MS = moderately susceptible, M R = moderately resistant,R = resistant9./ Candidate for release

70The stripe rust races 66EO. 6E16.66E16 and 38E16 have been found tobe <strong>the</strong> most important while. for leafrust. races 57 and 77 have been mostaggressive and frequent. S.A. Rizvi hasreported that LR19, LR24, LR25, LR28and LR29 genes have shown resistanceagainst a number of virulent isolates ofleaf rust. For controlling leaf rustattack, fungicides such as Indar,Daconil and Balytan have proveneffective.Wheat varieties Chat"S", Bulbul, Chris,Super X, WLl145, WLl146, WL1257and WL1562 have shown resistanceagainst smut inoculum. The fungicidesBaytan, Topsin-M, Vitavax-200 andBenlate have given good control of loosesmut, as has <strong>the</strong> solar energy methodwhich involves soaking wheat seed inwater for four hours and drying it in <strong>the</strong>sun. Diseases such as flag smut,powdery mildew, helminthosporiumleaf spots and foot and root rots, whichearlier were not of much significance,are now becoming important.Insect pestsFortunately, wheat is not attacked byany serious pests; however, infestationwith armyworm, cutworm, stem borer,cornstalk borer and green aphids hasoccurred in localized areas.DroughtAbout 21 % of total wheat area in <strong>the</strong>country is rainfed. The screening ofplant materials and <strong>the</strong> testing of newvarieties for drought tolerance arecarried out in rainfed areas or undersimulated moisture stress. Some of <strong>the</strong>varieties (Blue Silver, Lyp 73 and Pak81), which were developed for irrigatedareas, have also proved very successfulunder rainfed conditions; <strong>the</strong>refore, <strong>the</strong>testing of new varieties under bothirrigated and rainfed conditions isencouraged. The new variety Barani 83is now awaiting release.SaliDlty/sodicityAt present, 2.4 million ha of land inPakistan have been rendered salinesodicand, with <strong>the</strong> continuous use oflow-quality water. this menace isincreasing every year. Wheat yield hasbeen found to be reduced by 19%under moderately saline-sodie soils.Lack of nutrientsYield constraint experiments inirrigated and rainfed areas have shownthat <strong>the</strong> proper application of fertilizeris of utmost importance. Yieldreductions ranging from 51 to 73%have been observed without properfertilizer use. This clearly demonstratesthat wheat yields can be substantiallyincreased if fertilizer use is properlyregulated in <strong>the</strong> country.Planting dateMore than 50% of <strong>the</strong> wheat in Pakistanis planted late, I.e., during <strong>the</strong> month ofDecember. Planting date experimentshave shown that yield is progressivelyreduced with delays in planting. Yieldwas found to be reduced by 28.8 and57.8%, respectively, when sowing wasdelayed from November to Decemberand from November to January.WeedsChenopodium spp., Phalaris minor andConvolvulous spp. have been found tobe <strong>the</strong> major weeds. Wheat yields werefound to be increased by 167.7, 140.7and 136.3%, respectively, over <strong>the</strong>weedy control when weeds werecontrolled by <strong>the</strong> herbicides DicuranMA, Tribunil and Graminon.Durum Wheat ImprovementSystematic durum wheat improvementwork was begun in <strong>the</strong> mid-1970s, andtwo promising durum lines, V79717and V79736, have shown superiority inyield and disease tolerance as comparedto <strong>the</strong> bread wheat checks; <strong>the</strong>y are in<strong>the</strong> final stages of release.

71Triticale ImprovementRegular breeding work for <strong>the</strong>improvement of triticales has beeninitiated. and efforts are under way todevelop new primary and secondarytriticales and to improve spike fertility.grain hardness. color. plumpness andmilling. baking and nutritional quality.Although three triticale lines. T-1-83.V1399 and V80523. have shown goodyield performance. <strong>the</strong>ir commercialexploitation seems doubtful before flouryield (extraction). grain hardness.bread-making quality and grain colorare improved.Summer WheatNursery in KaghanThe second wheat crop (off-season) isgrown dUring <strong>the</strong> summer at highelevations at Kaghan (2134 m) toadvance a generation. increase seed ofelite lines and screen promising linesfor disease resistance. The station isproving very useful for accelerating <strong>the</strong>breeding program.Future Research StrategiesFuture strategies for <strong>the</strong> improvementof wheats and triticale will involve moreemphasis on breeding varieties whichpossess wider adaptation and canwithstand various types of stresses(disease. high temperature. cold andfrost. moisture shortage. salinitysodicityand waterlogging). Efforts willalso be made to develop wheat varietieswith low input requirements.Improvement of grain characteristicsand milling and baking quality oftriticales will also receive greaterattention.

72Production Constraints and Research Prioritiesin <strong>the</strong> Sou<strong>the</strong>rn Winter Wheat Region of ChinaC.F. Zhou. Institute of Food Crops. Jiangsu Academy ofAgricultural Sciences. Nanjing. Jiangsu. ChinaWheat has been cultivated in China formore than 4.000 years. and it is grownin almost all parts of <strong>the</strong> country.According to natural environmentalconditions. cropping systems andvarietal distribution. <strong>the</strong> wheat-growingareas are broadly classified into threemajor production regions. including <strong>the</strong>nor<strong>the</strong>rn winter wheat region. <strong>the</strong>sou<strong>the</strong>rn winter wheat region and <strong>the</strong>spring wheat region (5.6). These aresubdivided into ten different ecologicalregions to better define <strong>the</strong> varietal typeneeded for successful wheat production(Figure 1).Wheat Production in <strong>the</strong>Sou<strong>the</strong>rn Winter Wheat RegionThe sou<strong>the</strong>rn winter wheat region ofChina is situated to <strong>the</strong> south of <strong>the</strong>Huai River and Qinling Mountains. andcovers three ecological regions. <strong>the</strong> midlowerYangtze Valley winter wheatregion. <strong>the</strong> southwest winter wheatregion and <strong>the</strong> South China winterwheat region (regions 3, 4 and 5,Figure 1).1. North Chinawinter wheatregion2. Yellow-Dual 9River winterwheat region3. Mid-lowerYangtze ValleywiDter wheat region.4. Southwest wiDter wheat region5. South ChiDa wiDter wheat region6. Nor<strong>the</strong>ast spring wheat region7. North ChiDa spriDg wheat region8. Northwest spring wheat region9. Qing-zang spring-winter wheat region10. Xinjiang winter-spring wheat regi~nFigure 1. Wheat-growing areas in ChiDa. 1983Source: Chinese Wheat Cultivars and <strong>the</strong>ir Pedigrees, S.B. Jin, ed. 1983.Agriculture Press. Peking, China.

73The climate in this region is warm.with sufficient rainfall. Wheat is moreWidely grown in <strong>the</strong> subtropical zonethan in <strong>the</strong> tropics. In <strong>the</strong> YangtzeRiver Valley. <strong>the</strong> annual averagetemperature is 15 to 19°C. The averagetemperature in January varies from 2to 10°C. with <strong>the</strong> minimumtemperature about -10°C. Annualrainfall is between 800 and 1.500 mm.and <strong>the</strong> frost-free period lasts 220 to280 days. depending on <strong>the</strong> area. InSouth China. <strong>the</strong> annual averagetemperature varies from 16 to 24°C.and <strong>the</strong> average temperature inJanuary. from 6 to 19°C. Annualrainfall. depending on <strong>the</strong> area. rangesfrom 1,000 to 2.400 mm. The frost-freeperiod lasts 240 to 300 days; less frostoccurs in <strong>the</strong> sou<strong>the</strong>rn part of <strong>the</strong>region.The soil pattern in <strong>the</strong> sou<strong>the</strong>rn winterwheat region Is complex. including ricesoils. yellow soils. red soils. purple soils.yellow-drab soils. drab soils and brownsoils. The cropping index is high. withthree types of double-cropping systems.wheat with rice. wheat or barley withupland cotton and wheat with foodgrains o<strong>the</strong>r than wheat or rice. Among<strong>the</strong>se. <strong>the</strong> double cropping system ofwheat-rice is <strong>the</strong> most prevalent.covering more than two-thirds of <strong>the</strong>total wheat area; a triple croppingsystem of wheat-rice-rice is alsopracticed.Under <strong>the</strong>se climatic conditions. softred wheat (Triticum aestivum L.) isWidely cultivated. Wheat varieties arefall sown. but are mainly of springhabit with little or no vernalizationrequirement and photoperiodsensitivity. Some varieties aresemiwinter types, with medium to earlymaturity and a long dormant periodwhich prevents sprouting in <strong>the</strong> headbefore harvest. .Wheat ranks next to rice in importancein cereal production in <strong>the</strong> sou<strong>the</strong>rnwinter wheat region. In recent years,about 9 million hectares of wheat havebeen grown; of this, about 5 millionhectares are in <strong>the</strong> mid-lower YangtzeValley, 3.2 million hectares in <strong>the</strong>southwest winter wheat region and0.8 million hectares in <strong>the</strong> South Chinawinter wheat region. Average wheatyields have increased greatly in <strong>the</strong> past30 years, rising from 0.7 tlha in 1949 to2.7 tlha in 1982. These average yieldshave exceeded that of <strong>the</strong> country as awhole. In <strong>the</strong> last several years, <strong>the</strong>wheat area in <strong>the</strong> region represented33.2% of <strong>the</strong> total wheat area of China.and total production represented 37%of <strong>the</strong> entire country.During <strong>the</strong> last few years, <strong>the</strong> nation'shighest average wheat yield has been inthis region. For example. <strong>the</strong> averageyield in Jiangsu province reached 3,720kglha in 1983 (Table 1). The JiangsuAcademy of Agricultural Sciences ando<strong>the</strong>r institutions attained yield levels ofmore than 7.5 tlha between 1979 and1982: this shows <strong>the</strong> prospects forwheat production in <strong>the</strong> region.Variety ImprovementThe wheat breeding program in <strong>the</strong>sou<strong>the</strong>rn winter wheat region startedmany years ago. In <strong>the</strong> early 19208, <strong>the</strong>Table 1. The development of wheatproduction in Jiangsu province, China,1949 to 1983YearCultivated Production Yieldarea (000 tons) (kg/ha)(000 hat1949 3229 2165 6701959 2227 2472 11101969 2460 3325 13511979 2375 8261 34781980 2324 77891981 2367 7383335131191982 2424 8639 35631983 2704 10061 3720

74famous early-maturing variety JiangdongMen was selected from <strong>the</strong>indigenous variety. Sanyuehuang. In<strong>the</strong> 1930s. <strong>the</strong> former NationalAgricultural Research Bureau (NARB)and some o<strong>the</strong>r institutions launched across-breeding wheat program. Anumber of crossing combinations werefirst made in 1934 in Nanjing. fromwhich emerged <strong>the</strong> first varieties. suchas Liying 3. Liying 4 and Liying 6.Yield levels were still very low in <strong>the</strong>19408. Indigenous varieties weremainly grown. making up more than90% of <strong>the</strong> total wheat-growing area.The indigenous varieties in <strong>the</strong> regionare usually characterized by goodadaptation to <strong>the</strong> local environmentalconditions. and some have goodtolerance to excessive soil moisture andwheat scab. However. <strong>the</strong>y generallyhave poor yield potential and noresistance to rusts. Never<strong>the</strong>less. <strong>the</strong>sevarieties are valuable resources forwheat breeding and genetic studiestoday.The wheat breeding programs in <strong>the</strong>region use indigenous varieties withgood adaptability to local ecologicalconditions. At <strong>the</strong> same time. muchattention is paid to <strong>the</strong> introduction offoreign varieties and <strong>the</strong> direct orindirect utilization of <strong>the</strong>ir characters inorder to attain <strong>the</strong> best varieties for <strong>the</strong>region. According to incompletestatistics. 357 new improved varietieshave been selected and released in <strong>the</strong>region during <strong>the</strong> last 30 years. Thesevarieties have replaced <strong>the</strong> old.indigenous varieties and havecontributed a great deal to wheatproduction in <strong>the</strong> region. Generally.<strong>the</strong>se new varieties have goodadaptability. medium to early maturity.disease resistance and better yield.Wheat rusts in <strong>the</strong> region have beeneffectively controlled for 20 years, through genetic resistance. Somefamous improved varieties that havebeen released are Huadong 6 and 7.Aiganzao. Wumai 1. Ningmai 3 and 6and Yangmai 1.2.3 and 4 (Jiangsuprovince); Zhemail and 2. (Zhejiangprovince); Emai 6 and Jingzhou 1(Hubei province); Wannian 2 (Jiangxiprovince); 5.1 Mai. Chuan Mai 8. Fan 6and 7 and Mianyang 11 (Sichuanprovince); Yun 778 and Yun Mai 32(Yunnan province). and Jinmai 2148.Fumai 7 and Longqi 35 (Fujianprovince).Introduced foreign varieties with goodrust resistance gene(s) and high yieldpotentials have been used extensivelyas parents in variety improvment inthis region. The improved varietieshave been developed by variousbreeding methods (Table 2).Table 2. Improved varieties of wheat developed in <strong>the</strong> mid-lower Yangtze Valley, China,19505 to 197051950-1959 1960-1969 1970-1979 1950-1979Breeding No. 0/0 of No. o/e> of No. a/oaf No. 0/0method total total totalIntroduction 8 27.6 6 15.8 9 9.1 23 13.9Pedigree selection 6 20.7 7 18.4 17 17.2 30 18.1Intervarietal crossing 7 24.1 16 42.1 57 57.6 80 48.2Wide crosses 8 27.6 6 15.8 3 3.0 17 10.2Radiation breeding 0 0 3 7.9 13 13.1 16 9.6Total 29 17.5 38 22.9 99 59.6 166 100.0

75Recently, <strong>the</strong> pedigrees of 125improved varieties from <strong>the</strong> mid-lowerYangtze Valley were analyzed. Twentyeightof <strong>the</strong>m were derived fromindigenous varieties, and 92 fromItalian varieties; about three-fourths of<strong>the</strong> improved varieties were derivedfrom Italian varieties. There were also afew varieties derived from varietiesfrom o<strong>the</strong>r countries; eight were from<strong>the</strong> USA, seven from Chile, three from<strong>the</strong> USSR, three from Australia and twofrom Mexico.Major WheatProduction ConstraintsWheat production in <strong>the</strong> sou<strong>the</strong>rnwinter wheat region has developedrapidly in <strong>the</strong> last ten years, but <strong>the</strong>factor of yield instability still exists. Forinstance, during <strong>the</strong> past 34 years,production increased 18 years in <strong>the</strong>sou<strong>the</strong>rn part of Jiangsu province anddecreased 16 years. This was caused byvarious production constraints in <strong>the</strong>region.First, <strong>the</strong>re is excessive and poorlydistributed rainfall dUring <strong>the</strong> wheatgrowingseason, particularly in <strong>the</strong>spring. It generally considerablyexceeds wheat's physiologicalrequirements. and seriously influencesgrowth and development. For instance,in <strong>the</strong> winter wheat region of <strong>the</strong> midlowerYangtze Valley, averageprecipitation from <strong>the</strong> seedling stage tomaturity us.ually amounts to 430 to 755mm, of which 224 to 626 mm is in <strong>the</strong>spring (March to May), making up 48.5to 82.9% of <strong>the</strong> total rainfall during <strong>the</strong>wheat-growing period. According tometeorological data for <strong>the</strong> sou<strong>the</strong>rnpart of Jiangsu province from 1951 to1980, average rainfall dUring <strong>the</strong> periodof elongation to maturity was 270 to320 mm; <strong>the</strong>re was one rainy day inevery 2 to 2V2 days. In <strong>the</strong> years ofover-abundant rain, <strong>the</strong>re may be up to400 mm during this period. Excessivemoisture is <strong>the</strong> most important reasonfor <strong>the</strong> instability of wheat production,and it also enhances scab infection.Statistics from <strong>the</strong> Suzhou PrefecturalAgricultural Research Institute for <strong>the</strong>last 28 years shows that serious scabepidemics occurred in five of thoseyears; <strong>the</strong> rate of infection reached 50to 100% and caused yield losses of 20to 40%. There were ten years withmedium epidemics, with a rate of scabinfection of 20 to 40% and yield lossesof 10 to 20%; light or zero scab damageoccurred in 13 years. The averagefrequency of scab epidemics was53.3%, with one year of serious ormoderate scab epidemics out of everytwo years. For this reason. varietieswith high tolerance to excessive soilmoisture and good resistance to wheatscab are urgently reqUired for <strong>the</strong>region.The second limiting factor in <strong>the</strong> regionis high temperature dUring <strong>the</strong> lategrowing period of wheat. The averagenumber of days when air temperaturegoes above 30°C is usually 2.2 to 9.1days dUring <strong>the</strong> ripening period.Sometimes, before harvest, <strong>the</strong>re maybe high temperatures with lowhumidity, high evaporation and hot,dry southwest winds. This combinationof factors dries <strong>the</strong> grain so qUickly thatpremature senescence or even greendeath dUring <strong>the</strong> milk stage can occur;this, of course is a major reason for lowgrain weight. Thus. it is necessary todevelop a wheat variety with quickgrain filling, early maturity and a longperiod of seed dormancy in order toresist germination in <strong>the</strong> head causedby <strong>the</strong> excessive precipitation and hightemperatures in <strong>the</strong> late growing stage.High and stable yields of wheat are alsolimited by poor drainage facilities, lowsoil fertility, rough tillage, weeds anddamage by diseases and insect pests.There is also a large amount of redyellowsoils in Jiangxi, Hunan, Yunnanand Guizhou provinces. This type ofsoil is not suited to <strong>the</strong> growth ofwheat, and yield per unit area in <strong>the</strong>seprovinces is very low.

78Practice has showed that <strong>the</strong> followingmeasures would be effective inresolving <strong>the</strong> above problems:• Establish systems for rapid drainage,so that <strong>the</strong> ground-water level islowered and soil moisture contentdecreased. With <strong>the</strong> consequentincrease in soil aeration, injuriesfrom excessive soil moisture wouldbe avoided or alleviated:• Improve tillage practices in order tomake <strong>the</strong> soil more suitable for <strong>the</strong>growth of wheat;• Utilize proper rotation systems ofrice, wheat. rape seeds and greenmanure crops so that soil fertility isincreased, and• Eliminate damage from disease andinsect pests. Scab. rusts (stem, leafand stripe). powdery mildew, sheathblight, armyworm and aphids aremajor problems in <strong>the</strong> region.Bavistin spray at <strong>the</strong> flowering stageis an effective deterrant. Powderymildew and rusts can be controlledwith Bayleton; Validamycin isrecommended for sheath blight.Research PrIorities in <strong>the</strong>Sou<strong>the</strong>rn Winter Wheat RegionWheat production in this region hasbeen greatly increased in <strong>the</strong> last 30years. Without doubt, this has beenclosely related to varietal improvement.research on <strong>the</strong> rice-wheat rotation and<strong>the</strong> improvement of farm capitalinvestment. Research must now resolve<strong>the</strong> problems of instabll1ty while fur<strong>the</strong>rincreasing production and averageyield. The wheat research programswill focus on variety improvement, withspecial attention on disease resistance,early maturity and increased yieldpotential.Disease resistanceDiseases are one of <strong>the</strong> main productionconstraints to increasing wheat yieldsin <strong>the</strong> region. Wheat scab, rusts,powdery mildew and sheath blight areall present, but head scab causes <strong>the</strong>greatest damage. Breeding for scabresistantvarieties has been carried onin Jiangsu province since 1975.Screening for scab-resistantgermplasm-Although no germplasmhas been found with completeimmunity to scab, <strong>the</strong> response ofvarieties to scab are different. Somehave fairly good resistance to scab,while o<strong>the</strong>rs are badly damaged. Forinstance, Wangshuibai is an oldindigenous variety with good scabresistance. Scab-resistant germplasm isbeing used in <strong>the</strong> crossing program. Afew advanced lines have beendeveloped with high resistance to scaband o<strong>the</strong>r diseases, combined withbetter yield potential and earlymaturity.Identiflcatton ofscab-resistantstrains-Artificial inoculation in <strong>the</strong>laboratory or in <strong>the</strong> field by soil-surfaceinfection is being conducted in Nanjing.Multilocation tests are also beingconducted on 30 sites in <strong>the</strong> mid-lowerYangtze Valley and Fujian province toidentify materials with enhanced scabresistance.Early maturityEarly-maturing varieties with high yieldpotential could meet <strong>the</strong> needs of adouble or triple cropping system andescape destructive diseases andpremature senescence caused by hightemperatures and excessive moistureinjury.Increased yield potentialIn <strong>the</strong> better production areas.semidwarf varieties that have largespikes and that are responsive to inputsand resistant to lodging are requiredand must be developed.

77Variety improvement must also becombined with agronomic research.Agronomists in sou<strong>the</strong>rn China havebeen working on <strong>the</strong> populationstructure of high yielding wheat,including yield components andcultivation techniques. Thesetechnologies have led to better yields ofwheat after rice in <strong>the</strong> last ten years,and have played an active role inincreased wheat production. Agronomicresearch must be fur<strong>the</strong>r stressed inorder to increase <strong>the</strong> production,quality and economic benefit of wheatin <strong>the</strong> region.References1. Cereal Crop Division ofJiangsuInstitute of Agricultural Sciences.1976. Problems on breeding ofearliness in wheat. Acta GeneticaSinica, vol. 3. no. 4.2. Guo, S.Z., X.J. Chen and J.L. Zhen.1980. The cultural principle andpractices in high yielding wheat in<strong>the</strong> south of Huai River in Jiangsuprovince. Scientica AgriculturaSinica 1.3. Huang, P.M. 1981. A progress ofcultivated research of wheat in China.Information Research of" Agricultureand Animal Husbandry 22.4. Jin. S.B., ed. 1983. Chinese WheatCultivars and <strong>the</strong>ir Pedigrees.Agriculture Press, Peking, China.5. Jin, S.B., ed. 1961. Wheat Agronomyin China. Agriculture Press, Peking,China.6. Jin, S.B., and D.G. Liu. 1964. TheAnnals of Wheat Cultivars in China.Agriculture Press, Peking. China.7. Zhou, C.F., C.M. Qlan and 5.5. Xia.1982. Pedigree analysis of wheatcultivars and some problems onwheat breeding. Jiangsu AgriculturalScience 9.8. Zhou C.F., 5.5. Xia and C.M. Qian.1984. Breeding Wheat for resistanceto Gibberella zeae Schw. JiangsuAgricultural Science 2.

78Wheat Production Constraintsand Research Priorities in IndonesiaT. Danakusuma, Sukamandi Food Crops Research Institute,Cikampek, Sukamandi, IndonesiaWhile rice production in Indonesia isnearing self-sufficiency. wheat importsare rising dramatically. Wheatconsumption has increased significantlyeach year during <strong>the</strong> last decade; this isclearly reflected in increasing wheatimports. In 1970. wheat flour importswere 557.000 tons. and total wheatgrain imports have continuedincreasing until. by 1981, <strong>the</strong>y reached1.5 million tons (Figure 1).Wheat has been grown in Indonesia fora couple of centuries. especially in <strong>the</strong>relatively isolated highlands. such asPangalengan in West Java. <strong>the</strong> DiengPlateau and Salatiga in Central Javaand Brumo-Tosari in East Java. Thearea has always been nominal.compared to that occupied by o<strong>the</strong>rfood crops. Limited adaptation to highelevation and competition from highlyprofitable crops. such as vegetables and.l15rn c 1.0B'0~ gt. .15/~-----..,. .. ......,,,,,,, indq.strial crops. have kept <strong>the</strong> wheatgrowingarea negligible.It now appears that. by <strong>the</strong> end ofIndonesia's fourth Five Year Plan in1989. domestic wheat production willbe making a contribution towards selfsufficiencyin food carbohydrates within<strong>the</strong> country. Therefore. since early1981. <strong>the</strong> Indonesian government hasgiven more emphasis to increasedwheat production.Wheat research was begun in <strong>the</strong> early1980s. after wheat materials werereceived from India and Pakistan and.subsequently. o<strong>the</strong>rs were receivedfrom Spain. <strong>the</strong> Philippines and.especially. from CIMMYT.Research will concentrate on <strong>the</strong>development of wheat lines that areadapted to <strong>the</strong> various growingconditions in Indonesia. identification of,,'", ,, ,"Grain ./,",70 71 72 73 74 715 78Year", ,,~~~...-'.......- ..-......77 78 79 80Figure 1. Indonesia imports of wheat and flour, 1970 to 1980

79those areas that are suitable forgrowing wheat, wheat husbandry andtime of planting, disease control andpost-harvest technology, including <strong>the</strong>processing of wheat.Production ConstraintsEarlier reports indicated that wheatcould be grown with reasonable yield athigh elevations in <strong>the</strong> tropics. Resultsfrom recent experiments in Indonesiashow that some varieties can be grownsuccessfully in relatively low-elevationtropical environments. In 1982 and1983, in Kuningan, West Java (550meters above sea level), <strong>the</strong> averageyields of <strong>the</strong> five best varieties were2.09 and 1.97 t1ha, respectively, Someof <strong>the</strong>se results are presented inTables 1 and 2.Data were also obtained from a trial inMojosari, East Java (50 meters abovesea level), where <strong>the</strong> average yield of<strong>the</strong> five best varieties was 1.59 t1ha.These results indicate that wheat canbe grown in <strong>the</strong> tropics. even at lowelevations. In fact. most of <strong>the</strong> varietiestested were "physiologically" adaptedto <strong>the</strong> tropics (<strong>the</strong>y produced viableseed). Low yield was <strong>the</strong> result ofagronomic measures which needfur<strong>the</strong>r research. as well as of <strong>the</strong> needfor breeding better-adapted lines.Table 1. Mean grain yields of several varietiesgrown in <strong>the</strong> dry season, Kuningan, Indonesia,1982VarietyHI784 (Swati)R164.!/UPLWlSandalIWP72NI5439Lyal/pur 73OriginIndiaCIMMYTPhilippinesPakistanIndiaIndiaPakistan.!/ CM2699-12M-1Y-5M-2Y-4M-OYGrain yieldh/ha)2.332.142.132.122.112.041.81Constraints against a continuallysuccessful wheat crop are still great.Scab incidence is a continuous threat.especially when <strong>the</strong>re is unusuallyheavy rain during <strong>the</strong> flowering stage.Until now. <strong>the</strong>re has been no singlevariety identified as haVing truetolerance to this disease. Effectivemeasures against root rot caused bySclerotium rolfsii must still beinvestigated.·Fungicides available forseed treatment have not been found tobe effective.In <strong>the</strong> tropics. it is a well-known factthat it is easier to maintain soil fertilityin <strong>the</strong> lowlands (paddy fields) than in<strong>the</strong> uplands. since <strong>the</strong> latter is prone toheavier erosion. The deteriorating soilfertility of <strong>the</strong> uplands has complicatedvarietal evaluation to <strong>the</strong> extent that<strong>the</strong> varieties have been blamed as notbeing adapted to <strong>the</strong> hot. humidtropical environments. In a soil fertilitytrial, <strong>the</strong> use of 20 tons of manure perhectare was found to be optimal foryield. Since this practice would bedifficult on a large scale. alternativemeasures to improve <strong>the</strong> growingenvironment must be considered, suchas proper crop rotations and <strong>the</strong> use ofgreen manure crops. Only in suchimproved environments would <strong>the</strong>evaluation of wheat potential in <strong>the</strong>tropics be meaningful.Determining proper tillage operationsfor upland crops grown in lowlandpaddy fields (normally after <strong>the</strong> secondrice crop) is also difficult. Variousmanagement practices need to betested and evaluated for raising asuccessful wheat crop.Research PrioritiesThe general objective of <strong>the</strong> Indonesianwheat research program is to identifyand develop high-yielding varietiesadapted to. growing conditions inIndonesia. Also necessary is <strong>the</strong>identification of technology that wouldguarantee yields of at least 1.5 t1ha.Research will be conducted under

80various growing conditions. with wheatas a secondary crop after rice and onirrigated as well as rainfed uplands.Initially. research wUl depend heavilyon introductions from traditional wheatgrowingcountries and. especially. fromCIMMYT. Screening wUl have as itspriority. yield capabUity and adaptation.tolerance to important pests anddiseases and good qualitycharacteristics.Special objectives toward whichattention wUl be directed ~e:• The identification and developmentof superior wheat genotypes throughextensive introduction and. later.hybridization or o<strong>the</strong>r techniques forcombining high productivity withgood quality. nutritional value andadequate environmental stresstolerance:• The determination of landpreparation practices forguaranteeing reasonable plantdensity for high yield:• The evaluation of agronomiccharacters and disease tolerance ofselected materials in differentlocations:• The determination of nutritionalvalue and quality characteristics ofselected varieties at <strong>the</strong> cerealslaboratory. Sukamandi Food CropsResearch Institute (SURIF);• The determination of consumeracceptability. according to <strong>the</strong>intended use of <strong>the</strong> wheat;• The evaluation of crop productionpractices for enhancing yield. and• The determination of proper plantingdates of wheat within multiplecropping systems.Table 2. Yield and yield components of wheat varieties grown at Kuningan,Indonesia, 1983.J!Yield 1000llrain No. grains No. spikesVariety It/ha) weight per spike per m2H1784 2.05 a 39.8 c 22 ab 347 abeV1287 2.04 a 37.5 de 21 abed 333 abeLyallpur 73 2.04 ab 39.3 cd 19 abed 340 abeUPLWl 1.92 abe 34.0 ghi 18 abed 378 aLOK1 1.80 abed 36.8 ef 18 abed 337 abeHD2009 1.73 abed 34.9 defgh 24 a 326 abeSonalika 1.72 abed 43.0 ab 16 d 343 abeLU26 1.72 abed 33.7 ghij 20 abed 326 abeSandal 1.69 abed 35.8 efg 21 abed 283 abeLakhish 1.65 abed 39.6 cd 20 abed 328 abeSA75 1.64 abed 31.5 jk 21 abed 346 abeR164 1.60 bed 36.3 ef 18 abed 335 abeUP115 1.59 cd 33.8 ghi 17 bed 320 abeSureno 1.59 cde 32.6 ijk 22 ab 303 abeHW135 1.55 cde 41.0 be 17 bed 274 beB·3 1.54 cde 32.5 ijk 22 ab 355 abeIWP72 1.53 cde 44.9 a 16 cd 295 abeUP262 1.50 cde 41.4 be 16 cd 337 abeChenab 79 1.40 d 31.2 k 21 abed 368 abK342 1.36 de 33.3 hijk 20 abed 263 cBlue Silver 1.15 e 34.8 fghi 16 cd 261 c~I Means followed by <strong>the</strong> same letter or letters are not significantly different at <strong>the</strong> 5010level

Wheat Growing in <strong>the</strong> PhilippinesC.R. Escaiio, Crops Research Department, Philippine Council forAgriculture and Resources Research and Development, Los Baiios,Philippines81Wheat research and production are notnew ventures in Philippine agriculture.Historical records show that wheat wasfirst grown successfully in 1664. andflourished during <strong>the</strong> Spanish regime.However. later it totally disappearedfrom <strong>the</strong> Philippine scene.Several attempts were made to revivewheat production, but <strong>the</strong>se failed,mainly due to <strong>the</strong> lack of suitablevarieties. While progress has been slow,long years of experimentation andexperience have indicated that wheatcan be grown in selected areas of <strong>the</strong>country. Varieties Trigo 1 (UPLWl) andTrigo 2 (UPLW2) have been developedand are adapted to selectedagroclimatic conditions. Specific areasof production and cultural managementreqUirements also have been identifiedand wheat production technology hasbeen packaged: never<strong>the</strong>less, much stillremains to be accomplished.Pilot Wheat Production ProgramThe present joint program of <strong>the</strong>National Science and TechnologyAuthority. <strong>the</strong> Philippine Council forAgriculture and Resources Researchand Development (PCARRD) and <strong>the</strong>National Food Authority (NFA) willinclude wheat in <strong>the</strong>ir packages oftechnology (POT) that will bedemonstrated for <strong>the</strong> rice-basedproduction system. This system isrelevant to many areas of nor<strong>the</strong>rn andcentral Luzon, where irrigation water istoo limited to allow a second rice crop.During <strong>the</strong> coolest part of <strong>the</strong> year,December to February, wheat couldsuccessfully complete its cycle ofgrowth and development.The National Wheat ProductionProgram, which was started in 1982, iscoordinated by PCARRD and hasparticipation from five government andprivate agencies: it covers three regions(Regions 1,2 and 3) of <strong>the</strong> country.During <strong>the</strong> first year, it was conductedin eight locations, with a total area of24.85 hectares. For <strong>the</strong> 1983-84cropping year, a total of 46.89 hectares,involVing 94 farmer-cooperators, wereincluded.With <strong>the</strong> experience gained from <strong>the</strong>preVious cropping season, better yieldswere obtained during <strong>the</strong> 1983-84season. For example, in Ilocos Norteand Ilocos Sur, average wheat yieldswere 1,146 and 1,018 kglha,respectively. Generally, farmercooperatorswho adhered to <strong>the</strong>recommended practices obtained betteryields. The average cost of producing1 kg of wheat grain was estimated atP3.86 (US$ 0.20). In terms of harvestquality, about 85% of <strong>the</strong> harvests wereclassified as seed grade: that seed waspurchased by NFA at P5.201kg(US$ 0.26). Some sites, however, hadpoor yields and even failures, due tovarious production and managementconstraints.Production ConstraintsContinuous assessment of <strong>the</strong>applicability of <strong>the</strong> POT at <strong>the</strong> differentpilot sites identified several needsbefore improved wheat production canbe realized, such as fertilization, pestand weed control, seed quality, creditand crop insurance.The delayed harvesting of <strong>the</strong> rice croppreceding wheat planting, which wasbrought about by a long drought inmost prospective pilot sites, caused <strong>the</strong>withdrawal of some farmer-cooperatorsfrom <strong>the</strong> project.

82Lack of needed pesticides in <strong>the</strong> localmarket resulted in heavy infestation offoot rot and Helminthosporium leafspot. as well as damage from stemborers in some pilot areas. It is alsoeVident that some farmer-cooperatorsneed fur<strong>the</strong>r training in carrying outcertain components of POT.Research PrioritiesPCARRD is committed to <strong>the</strong> effectiveand efficient management ofagricultural research and resources.Since its establishment in 1972.PCARRD has carried out its mandate tounite all research undertakings.manpower. facilities. funds and o<strong>the</strong>rprogram resources into a potent forcefor national development. Thus. it sets<strong>the</strong> long-range research directions for<strong>the</strong> total research system. rationalizes<strong>the</strong> strategies and orchestrates <strong>the</strong>mechanisms for attaining <strong>the</strong>m.Continuous breeding for high-yieldingvarieties. adapted to <strong>the</strong> climate of <strong>the</strong>Philippines. is a vital part of wheatresearch. Yield potentials must beincreased through selection foragronomic characteristics such astolerance to environmental stresses andresistance to helminthosporium leafspot. foot rots. corn earworm and pinkstem borer. New introductions of wheatfrom CIMMYT and <strong>the</strong> InternationalCenter for Agricultural Research in DryAreas (ICARDA) will be screened foradaptability. This must be accompaniedby varietal testing of promisingselections on a regional level.Seed production of <strong>the</strong> most promisingselections and varieties will beVigorously pursued to make <strong>the</strong> seedavailable for applied research trials andfor interested farmers and seedproducers. Varietal characters needed ifwheat is to fit into rice-based croppingsystems have to be preciselydetermined. as well as fur<strong>the</strong>rinformation on production constraintssuch as weeds. diseases and insects.The economics of wheat production incombination with com. mungbean andsoybean must also be considered.The need for more on-farm research isessential. Recommendations forfertilizer use and weed and diseasecontrol that are developed in <strong>the</strong>research stations must be verified onfarmers' fields.Socioeconomic studies will beincorporated into <strong>the</strong> research to assess<strong>the</strong> profitability and acceptability of <strong>the</strong>production program. Information from<strong>the</strong> pilot areas with respect to <strong>the</strong>methods and management proceduresof individual farmers in relation toyields obtained and problemsencountered will provide a data base fordecisions. policy making and fur<strong>the</strong>rresearch directions.Future PlansConcerned people are optimistic thatmost of <strong>the</strong> requirements forcommercial wheat groWing can be metthrough:• Intensive seed production!multiplication. especially of <strong>the</strong> newpromising lines;• Expansion of <strong>the</strong> program, usingseeds produced from previous crops.and• Continuous refinements of <strong>the</strong> POTto suit local conditions.Detailed biophysical and socioeconomiccharacterization and analysis of <strong>the</strong>various pilot sites will be carried out torationalize <strong>the</strong> successes or failuresobtained from this pilot testing. Thetraining of technicians and farmercooperatorsin wheat culture andmanagement will also be a continuingprogram.-Interagency and multidisciplinarycooperation will be fur<strong>the</strong>rstreng<strong>the</strong>ned.

83Thailand Winter Cereals ProgramP. Chandhanamutta, Rice Research Institute, KasetsartUniversity, Bangkok, ThailandThailand is a tropical country. lyingbetween 5 and 21 0 N latitudes; it has atotal area of about 513.000 squarekilometers. Wheat production ispossible in <strong>the</strong> cooler area of nor<strong>the</strong>rnThailand. which lies above 18°N. Thisregion is a mass of mountains. withseveral rivers. and level areas along <strong>the</strong>larger rivers and streams. Total area oflowlands. uplands and highlands are0.9. 3.1 and 6.5 million hectares.respectively. The lowlands are about300 meters above sea level. rising to anaverage elevation in <strong>the</strong> mountains in<strong>the</strong> north of 1.600 meters. Meanminimum and maximum temperaturesfrom November to February (<strong>the</strong> wheatgrOWingseason) in <strong>the</strong> lowland area are13 and 28°C. respectively; meanrainfall during <strong>the</strong> same period is10 mm. Under <strong>the</strong>se conditions. wheathas a crop cycle of 100 to 120 days.Wheat ConsumptionThe current population of Thailand isabout 50 million. Rice is <strong>the</strong> staplecereal food. Per capita consumption ofrice in 1981 was 144 kg: that of wheatwas only 4.7 kg. Long-term prospectsfor growth in wheat consumption aretentatively placed at around 12%annually. Wheat grain and flourimports in 1981 amounted to some230.000 tons; about 85% of <strong>the</strong> importswas in wheat grain which went to fourflour mills in Bangkok. The mills arecurrently running below full capacity.PricingThailand imports most of its wheatfrom <strong>the</strong> United States. The CIFBangkok wheat price is US$ 200 perton or US$ 0.20 per kg. The Thaigovernment charges a tariff and o<strong>the</strong>rtaxes on wheat imports. estimated to beabout 40% of <strong>the</strong> CIF value. This puts<strong>the</strong> cost to <strong>the</strong> millers at approximatelyUS$ 0.28 per kg. Local wheat farmersexpect to get US$ 0.35 per kg as a farmgate price. Therefore. only throughgovernment protection and subsidy canlocal wheat be competitive withimported wheat. However. commercialwhite flour costs about US$ 0.60 per kgor more. It is conceivable that a marketfor a local flour would be an incentiveto farmers to grow wheat.Wheat UseWheat farmers in Thailand produceabout 160 tons of grain annually. andthis small amount is sufficient to makesome local food products. Enzymesfrom wheat sprouts are mixed withcooked glutinous (waxy) rice to makeliquid glucose. which is used in specialcandies. Cracked roasted wheat isfermented with soybean to prepare soysauce and miso. Steamed crackedwheat is used as a medium to cultureoyster mushroom spawn. The fourmodern flour mills produce a variety ofhigh-quality flours and semolina. whichare used to make bread. cakes. pastries.biscuits and noodles. as well as someThai and Chinese foods.Wheat MarketingWith <strong>the</strong> limited local wheatproduction. a direct trade betweenfarmers and food processors is generallypracticed. If <strong>the</strong> volume of trade isexpanded. <strong>the</strong> private merchants thatcurrently market rice and o<strong>the</strong>r fieldcrops would take wheat as a newcommodity. However. this middlemanin <strong>the</strong> rice marketing system is reapinga very high profit. Therefore. wheatmarketing might bypass thismiddleman. It is suggested here thatwheat production should beincorporated into various rural

development projects. Wheatcampaigns at <strong>the</strong> village level wouldencourage fanners to grow and learnhow to prepare wheat for food. A smallmill and bakery could first beestablished. Then. with productionexperience and a larger number offanners involved. <strong>the</strong> point might bereached when <strong>the</strong>re would be enoughlocally produced wheat to supply <strong>the</strong>modern mills in Bangkok.Potential Wheat AreaWheat can be grown in three situations.on 1) <strong>the</strong> rainfed highlands. 2) <strong>the</strong>uplands. ei<strong>the</strong>r rainfed or withirrigation. and 3) <strong>the</strong> lowlands afterrice. ei<strong>the</strong>r rainfed or with irrigation.A thorough survey of potential wheatarea has not yet been made. One recentstudy estimated that about 117.000hectares of lowland rice soU in ChiangRat province are suitable for wheatfanning. The soUs are loamy. somewhatacid. moderately light in texture andmore than 150 centimeters deep. Apreliminary crop water use studysuggests an available soU-watercapacity of 250 mm in an area where<strong>the</strong> 75 mm of rainfall nonnally reqUiredfor reliable rainfed crop production canbe expected in <strong>the</strong> month of October.Research and DevelopmentWheat research commenced in <strong>the</strong>early 19608 as a project of <strong>the</strong> Ministryof Interior. From that program. <strong>the</strong> twocurrently available varieties. INIA 66and Sonora 64. were selected. During<strong>the</strong> 19708. o<strong>the</strong>r organizations becameinvolved and. in 1979. <strong>the</strong> first NationalWheat Workshop was held to exchangedata and to coordinate research. Theworkshop is now an annual event.There are three separate entitiesconducting breeding programs inThailand:• The Department of Agriculture.based at Samoeng. with <strong>the</strong> objectiveof breeding and selecting wheats for<strong>the</strong> cooler medium and higheraltitudes;• Chiang Mal University. selecting for<strong>the</strong> areas with about 300 metersaltitude. and• Kasetsart University. selecting for<strong>the</strong> hot. dry nor<strong>the</strong>ast region ofThaUand.These three programs submit entries to<strong>the</strong> Thailand Observation Nursery and<strong>the</strong> Thailand Yield Nursery. which aregrown at many sites throughout <strong>the</strong>country. The lines under evaluation arelargely selections from various CIMMYTand ICARDA nurseries. although anumber have been derived from locallymade crosses.Progress is being made in <strong>the</strong> selectionof wheats which outperfonn currentvarieties (Table 1). Agronomic trialshave been carried out by <strong>the</strong> threeorganizations over <strong>the</strong> past four years.and agronomic recommendations havebeen tentatively fonnulated.Table 1. Mean yields of <strong>the</strong> five bestperforminglines in <strong>the</strong> Thailand YieldNursery, 1984NameipedigrHUP262QuimoriPi-Frond x Pi-Mazoe/Mexipak,PK2858-7a-3a·3a-OaBuckbuck''S'', CM31678-R-4Y2M-15Y·2M·1 Y -OMBluebird-eN067 x INIA-Soty,CM 1502·8M-3Y·3M·2Y-OMINIA66Sonora 64Mean yield(kg/ha)2266225722512124210219791838

Many farmers are now exploring <strong>the</strong>possibillty of growing wheat, mainly asa result of its promotion as a cereal forhome consumption ("local use") by <strong>the</strong>Department of Agriculture ExtensionService. Agronomic recommendationswill be verified on small-scale plantings.O<strong>the</strong>r areas receiving attention in <strong>the</strong>overall program are plant protection,provisions for seed production andstorage facillties, economic andmarketing issues and <strong>the</strong> training oftechnicians and farmers in wheatproduction techniques.SummaryThailand's increasing consumption ofwheat (12% annually) will bring abouta huge trade deficit in <strong>the</strong> future.Wheat is currently being grown in asmall area in <strong>the</strong> nor<strong>the</strong>rn provinces.but most farmers are unaccustomed towheat production and utilization. Arenewed wheat program with CIMMYTsupport is being launched for farmers,and advances are being made inselection for high-yielding varieties. Dueto <strong>the</strong> lack of a marketing system, <strong>the</strong>crop is initially being introduced forhome consumption through small localmarkets...

86Dryland Wheat Productionin <strong>the</strong> Subtropics of Queensland, AustraliaD.R. Woodruff, Queensland Wheat Research Institute,Toowoomba, Queensland, AustraliaThe subtropical, dryland wheat-growingregions of Queensland, Australia, arecharacterized by a summer-dominantbut extremely variable rainfall (Figure1). This leads to <strong>the</strong> need to store largequantities of water in <strong>the</strong> soil prior toplanting (120 mm available water beingcommon) as a buffer against <strong>the</strong> lowwinter rainfall. Figure 1 also presents<strong>the</strong> mean daily temperature which hasan average range of 16°C. A frost riskextends from June to August, but isquite variable at specific sites,depending upon <strong>the</strong> local topography.As a result of extensive fieldinvestigations, <strong>the</strong> preferred plantingtime in regions of low frost risk has150175changed from June (with floweringafter <strong>the</strong> danger of frost has passed. andan average grain yield of 1.4 Uha). toMarch and April (with floweringoccurring from June to early August).The early pla.I1ting allows for growthand, hence, increasing transpirationpotential to be timed to coincide withdeclining evaporative demand, ra<strong>the</strong>rthan haVing <strong>the</strong>se factors in phase, asoccurs with June plantings. Thisresults in a considerable saving in totalwater use from planting to an<strong>the</strong>sis. Fora given planting date, it is possible tomatch potential water use in <strong>the</strong> preand post-an<strong>the</strong>sis phases, since most of<strong>the</strong> water likely to be available to <strong>the</strong>158 -(.)~Imedian A Mean temperature20 and 80 • Mean evaporation... ... ~ percentiles ,,'"'...'...~, JJ! /'~..., ...~, ..."'... /' ......-_.....03O~~::s25~~12~p.208~10 .....815 ~ tU~~J F M AM J J A 80 NOFigure 1. Long-term climatic conditions, Emerald, AustraliaLatitude 23°30'36"8, longitude 148°09'43"E, altitude 212 mRainfall, mean over 91 yearsEvaporation, mean over 12 years10% probability of OOC screen temperature: first, June 5, last, August 18

87crop is present, and known. at planting.This may mean restricting growthduration and biomass production tolevels where grain yield is belowpotential in years of high growingseasonrainfall; <strong>the</strong> improved reliabilityof grain yield, however, more thancompensates for this loss and gives anexpected long-term average yield ofapproximately 2 Uha.Planting under high temperatures andphotoperiods of around 12.5 hours perday allows a full expression of genotypevariation in phenology, which is oftenmasked in winter planting by <strong>the</strong>effects of low temperature on vegetativedevelopment. Under conditionsconducive to very high growth rates,small differences between genotypes,agronomic practices and diseaseincidence can have disproportionateeffects on grain yield expectancy,especially when using short-seasongenotypes which produce relatively lowbiomass by an<strong>the</strong>sis. Under <strong>the</strong>seconditions, <strong>the</strong> total radiationinterception by <strong>the</strong> crop. especially upto apical spikelet production, isextremely important. However,genotypes differ in radiationinterception, and such differences aredue to variations in phenology and <strong>the</strong>area of <strong>the</strong> first few leaves produced.This is reflected in genotypic variationin tiller and biomass production perunit of time, which appears to be moremarked and durable than under moretemperate conditions. The agronomicmanipulation of radiation receipt byvarying plant population andarrangement does not often interactwith genotype. A planting rate of50 kg/ha is sufficient to maximize grainyield, except when <strong>the</strong> crop grows onlyon seminal roots; <strong>the</strong>n a higherplanting rate can be advantageous.Establishment of <strong>the</strong> crop under hightemperature conditions is critical, notonly for its effect on initial leaf cover, butalso in relation to <strong>the</strong> position of <strong>the</strong>crown node. There is a large genotypeand temperature interaction oncoleoptile length; at constant 35°C <strong>the</strong>reis little genotype variation in coleoptilelength (4 cm), whereas at 20°C it variesfrom 6 to 14 cm (Figure 2). Thesemidwarf genotypes have <strong>the</strong> shortestcoleoptiles. Attempts to break <strong>the</strong>linkage between short coleoptile andNorin 10 genes have as yet beenunsuccessful. Soil type and condition,ra<strong>the</strong>r than genotype, appear to be <strong>the</strong>major factors in determining whe<strong>the</strong>r<strong>the</strong> leaf emerging underground willreach <strong>the</strong> surface and establish a plant.On many soils. it has been foundnecessary to use presswheels over <strong>the</strong>planted row to reduce <strong>the</strong> depth ofMarch plantings in order to gaineffective establishment. Subsequentrainfall tends to wash soil into <strong>the</strong>depressions over <strong>the</strong> seed, thusincreasing <strong>the</strong> depth of <strong>the</strong> crown nodein <strong>the</strong> soil. The deeper <strong>the</strong> crown node,<strong>the</strong> better is nodal root productionfollOWing subsequent rain. Rainfall soonafter planting appears to be necessaryto obtain maximum tiller production,although whe<strong>the</strong>r this is due to nodalroot production or nutrient availabilityand uptake is unknown. Tillerproduction under high temperaturesdoes, however, appear to be extremelyresponsive to nutrient availability.Commercial production underconditions of high temperature duringvegetative growth is currently restrictedto areas of low frost risk, since graindevelopment continues into midWinter.Since no wheat breeding or selection isconducted specifically for this system,<strong>the</strong> cultivars are chosen from <strong>the</strong> poolof generally adapted Queenslandcultivars on <strong>the</strong> basis of <strong>the</strong>ir testedphenological adaptability to <strong>the</strong>environment. Diseases have not yetbecome a problem, due to <strong>the</strong> lowhumidity and good resistance presentin commercial genotypes; however, leafand stem rusts are potentially serious.Current research is assessing <strong>the</strong>Viability of still earlier planting to allow

88completion of grain growth before anysignificant frosts occur. even in areas ofmoderate frost risk. Moving vegetativegrowth and an<strong>the</strong>sis into highertemperature and humidity conditionshas resulted in <strong>the</strong> appearance of headscab (Gibberella zeae). which has beensevere on certain genotypes. and spotblotch (Bipolaris sorokiniana), whichhas occurred on barley. Base rot(Sclerotium rolfsit) is present in allcereals and. toge<strong>the</strong>r with o<strong>the</strong>r rootdiseases. has <strong>the</strong> potential to becomeserious. When an<strong>the</strong>sis has taken placeunder conditions of high temperatureand prolonged high humidity. somedamage to an<strong>the</strong>rs has reduced grainset. Whe<strong>the</strong>r this is a direct effect ofenvironmental factors or is associatedwith microbial growth on <strong>the</strong> an<strong>the</strong>rshas yet to be determined. as has anygenotype variance in this factor.In conclusion. it is believed that. in <strong>the</strong>absence of serious diseases, satisfactorywheat yields can be achieved underdryland, subtropical conditions ingueensland. Agronomic practices arecritical, however, in gaining satisfactoryperformance. Substantial genotypevariations for characters which appearto be of importance in <strong>the</strong>seenvironments do exist, and <strong>the</strong>determination. not only of <strong>the</strong>irimportance but also of <strong>the</strong> selectionenvironment needed to exploit <strong>the</strong>sevariations, is critical to <strong>the</strong> developmentof a viable wheat industry in <strong>the</strong>seregions.e'-l16 o Spicao Gatcher14• Cook• Shortim• Kite Hartog12 6. Banks+ Oxley-10..c:: ....."tl.OLSD:Q.£ p=v 8:= ..... I I.05 .01Po.0Cl) 6-0 ()4215 20 25Temperature (OC)30 40Figure 2. Effect of temperature on <strong>the</strong> coleoptlle length of eight cultlvarsBy permission: B. Radford, unpublished

6 ~89Contributed PapersI. BreedingBreeding Wheat forMore Tropical Environments at CIMMYTR.L. Vlllareal, S. RaJaram aDd W. NelsoD, Wheat Program, CDlMYT,MezicoTropical wheat is defined. as early genotypes with <strong>the</strong> abtltty to give acceptableyields under tropical conditions, and with resistance to helminthosporium andleaf rust and tolerance to high temperatures. Tropical areas include thosebetween 23ON and 23°S latitudes with elevations of less than 1500 metersabove sea level. The goal ofCIMMYT's Tropical Wheat Improvement Program isto breed. wheatsfor <strong>the</strong> nontraditional, tropical wheat-growing areas, includingparts ofThailand, Phtltppines, Sri Lanka. <strong>the</strong> Chaco region ofParaguay, <strong>the</strong>lowlands ofBolivia and <strong>the</strong> Cerrados ofBrazil. Two years of research have beencompleted. in <strong>the</strong> identification ofsuitable linesfor tropical conditions. Adaptedgermplasm has been extensively used in crosses, resulting in a large number ofsegregating populations. Materials comingfrom <strong>the</strong> breeding program. as wellas germplasmfrom countries around <strong>the</strong> world. have been distributed to targetcountries through CIMMYT's international nursery network. In cooperation withCIMMYT pathologists, mass screening techniques have been developedforhelminthosporium resistance.CIMMYT's bread wheat program aimsto produce, in close collaboration withnational wheat research programs,widely adapted, high-yielding varietiescharacterized by semidwarf plantstature, photoperiod insensitivity,acceptable industrial quality, andresistance to such environmentalstresses as drought, heat, cold,aluminum tOXicity, salinity, andprevalent diseases such as stem rust,leaf rust, stripe rust, septoria leafblotch, septoria glume blotch,helminthosporium, scab and barleyyellow dwarf. The program's mainobjective is <strong>the</strong> production of advancedlines suitable for various agroclimaticareas of <strong>the</strong> world where wheat iscurrently <strong>the</strong> major food crop or whereits consumption is rapidly rising.Disease complexes, soil types andclimatic conditions vary considerablyfrom one target area to ano<strong>the</strong>r. Thus,CIMMYT's breeding approach is todevelop a base of Widely adapted, highyielding.disease-resistant wheat linesthat possess <strong>the</strong> specific attributesnecessary to achieve higher yield underspecific target-area conditions. Thebreeding methodologies used for eachenvironment are similar, with slightmodifications. To simplify thispresentation, only <strong>the</strong> development ofwheats for warmer and nontraditionalwheat-growing areas in <strong>the</strong> tropical beltwUl be discussed.Tropical WheatResearch at CIMMYTCIMMYT's interest in exploratory workto fur<strong>the</strong>r extend wheat into <strong>the</strong>lowland tropics was initiated in 1978.The Mexican location of Poza Rica(21 0 N, 60 meters altitude) was used forearly screening work.

90At <strong>the</strong> recommendation of <strong>the</strong>Technical Advisory Committee (TAC) of<strong>the</strong> Consultative Group on InternationalAgricultural Research (CGIAR). andwith special project funding from <strong>the</strong>United Nations DevelopmentProgramme (UNDP). CIMMYT expandedits exploratory research on tropicalwheat in 1981. Preliminaryinvestigations have included:• The continuation of <strong>the</strong> evaluation ofwheat germplasm and relatedspecies possessing desirablecharacteristics for tropical areas;• The development of screeningtechniques. and• The identification and establishmentof working relationships. wherenecessary. with locations for <strong>the</strong>testing of advanced materials.After <strong>the</strong> successful completion of <strong>the</strong>preparatory phase of <strong>the</strong> TropicalWheat Improvement Program.CIMMYT. with special five-year projectfunding from UNDP. has recentlyundertaken a small experimentalresearch and training effort for <strong>the</strong>development of wheats with specifictraits necessary for certain warmerenvironments. The overall objective of<strong>the</strong> research program is to develophigh-yielding. disease-resistant,semidwarf wheats that perform welland at profitable levels dUring <strong>the</strong>cooler season in <strong>the</strong> tropics andsubtropics.The TropicalWheat EnvironmentVariable hydrological, climatic andedaphic factors make a specificdefinition of a tropical wheat-growingsystem difficult. However. a workingdefinition would include all existing andpotential wheat-growing areas between23°N and 23°5 latitudes. and wi<strong>the</strong>levations less than 1500 meters abovesea level. As its first step in <strong>the</strong>program, CIMMYT's aim is to breedwheats adapted to <strong>the</strong> warmer andnontraditional wheat-groWing areas of<strong>the</strong> world. such as parts of Thailand.<strong>the</strong> Philippines, Sri Lanka. <strong>the</strong> Chaco ofParaguay. <strong>the</strong> lowlands of Bolivia and<strong>the</strong> Cerrados of Brazil. Extension too<strong>the</strong>r areas can occur later.Production Constraintsand Breeding ObjectivesIn developing wheat varieties fortropical environments, a number ofproduction constraints must be takeninto consideration. The breedingobjectives pursued are dictated by <strong>the</strong>water regimes and relevantphysiochemical and biological stressesof <strong>the</strong> target areas.Production conditions and constraintsare far too varied between locations tospecify precisely <strong>the</strong> combinations oftraits that would be desirable for anadapted wheat variety. However, someof <strong>the</strong> more important characters thatshould be emphasized are a stable highyield. good agronomic characters.desirable grain quality and resistance toenvironmental stress. diseases. insectsand sprouting.Stable high yieldThis is <strong>the</strong> most importantconsideration in developing wheatvarieties for tropical areas. Varietiesthat prOVide a stable yield give <strong>the</strong>farmer a degree of certainty that he willhave something to harvest. regardlessof <strong>the</strong> environmental stress.Good agronomic characteristicsSeveral agronomic characteristics areimportant for <strong>the</strong> successful productionof wheat under tropical conditions.Early vegetative vigor-Thischaracteristic is of primary importancein helping to overcome weedcompetition. in compensating formissing plants and in helping to ensurethat <strong>the</strong> crop achieves its critical leaf

91area at flowering. Vegetative vigor isrelated to various combinations of rapidseedling emergence and development.early and heavy tillering and early andrapid increase in seedling height.Considerable variation in early vigorexists among CIMMYT wheatgermplasm.Early maturity-This is ano<strong>the</strong>r traitthat is clearly advantageous for wheatin intensive rotation patterns with o<strong>the</strong>rcrops. In a rice-wheat cropping system.rice is nonnally harvested in October orNovember. after which wheat is sown.By <strong>the</strong> time land preparation iscompleted. <strong>the</strong> sowing date for wheat isalready delayed beyond <strong>the</strong> optimumfor medium to late-maturing varieties.Earliness also minimizes risk byshortening <strong>the</strong> crop's exposure toadverse high temperature conditions.Semidwarfstature and lodgingreststance-These are definiteagronomic requirements. especiallyunder moderate to high fertilityconditions. Considerable yield lossoccurs when <strong>the</strong> crop lodges. andharvesting becomes very difficult. Theadvantages of short. sturdy culms havebeen dramatically demonstrated in <strong>the</strong>high-yielding varieties of wheat.Resistance toenvironmental stressesWheat varieties for <strong>the</strong> tropiCS will needresistance to various environmentalstresses.Heat tolerance at <strong>the</strong>Juvenile andlater growth stages-This is acharacteristic that must beincorporated. Unadapted types tend tohave reduced tillering. poor plant Vigorand very early flowering dates. Fertilityand seed weight also decline whenwheats flower or ripen during periods ofhigh temperatures. Therefore. toperform well under tropicalenvironments. a variety must havesome degree of tolerance to warmtemperatures and humid conditions.Drought reststance-This is ano<strong>the</strong>rcharacteristic to be emphasized. Wheatin most target areas will be grownunder rainfed conditions, and <strong>the</strong> cropmust be grown primarily on residualsoil moisture. In addition. winterrainfall cannot be depended upon;drought stress can occur at any point of<strong>the</strong> grOWing cycle. Hence. tolerance todrought becomes critically important.Tolerance to adverse soils-This isdesirable. since wide fluctuations ofmineral concentrations are associatedwith chemical changes that occur intropical soils. due to alternate wettingand drying. Consequently. toxicitiesand deficiencies occur in many crops.Soils under tropical environmentsfrequently have low pH and highaluminum content. resulting inaluminum tOXicity in grOWing plants.Salinity problems may be ano<strong>the</strong>rconstraint to high wheat yields in <strong>the</strong>humid tropiCS. In general. soil salinityis caused by <strong>the</strong> presence or intrusionof sea water. or by surface evaporationof soil water that is initially high in saltcontent.Disease resistanceThis is a very important breedingobjective. It is essential that wheatvarieties for <strong>the</strong> tropical areas beresistant to <strong>the</strong> major prevalentdiseases. One serious disease constraintin most areas is leaf rust. caused byPucctnia recondita. This diseaseconstitutes a major threat to yield.especially when wheat is grown over anextensive area. CIMMYT currentlypossesses germplasm with excellentresistance to leaf rust, and this can betransferred to germplasm that appearspromising for <strong>the</strong> tropiCS.Under production conditions of warmtemperatures and high humidity. leafblotch. caused by severalHelminthosporium spp.. may also be aserious problem. CIMMYT's preliminary

92work on helminthosporium, supportedby a special project research grant fromUNDP, has resulted in <strong>the</strong> identificationofadvanced lines with varying degreesof resistance.Resistance to head scab, caused byFusarium spp., is especially needed in<strong>the</strong> more humid tropical environments,where conditions are ideal for <strong>the</strong>development of <strong>the</strong> disease. CIMMYThas recently intensified its efforts todevelop high-yielding lines with scabresistance. By <strong>the</strong> end of 1983, lineshad been identified that possessed someresistance.O<strong>the</strong>r disease problems confrontingwheat in tropical climates are <strong>the</strong> soilbornediseases, such as foot rot andseedling blight, caused by Sclerotiumrolfstt. Damping-off of seedlings oftenoccurs when temperatures are high and<strong>the</strong> soil saturated with moisture; it isstill not known whe<strong>the</strong>r it will bepossible to identify resistance to thisparticul~disease. Possibly morepromising would be <strong>the</strong> development ofa chemical seed-treatment technique fordisease control. Ano<strong>the</strong>r soil-borneproblem is fusarium, which causesseedling blight. root rot and <strong>the</strong> spikeinfection, scab.Bacterial stripe, caused byXanthomonas translucens, is ano<strong>the</strong>rthreat to wheat cultivars under tropicalenvironments. A severe infection of thisbacteria kills most, if not all, of <strong>the</strong>foliage of <strong>the</strong> wheat crop, causing adrastic reduction in yield. Bacterialstripe is widely distributed, but it onlybecomes important where susceptiblevarieties are grown and <strong>the</strong> growingseason is predominantly wet.Insect resistanceFor tropical wheat varieties, thischaracteristic is also important, sinceinsects such as <strong>the</strong> rice stem borer,corn earworm, corn semilooper,armyworm and aphids can be seriouspests.Desirable gralD qualityGrain color and appearance andacceptable milling and baking qualitiesare important qualities. The wheatproduced in <strong>the</strong> tropical areas will bedestined primarily for local millers;hence grain type and quality will playan important role in farmer decision toadopt a particular variety.Sprouting resistanceThis is an obvious requirement forwheat varieties for tropical areas, as ithinders grain from sprouting in <strong>the</strong>spikes before harvest, which wouldlower <strong>the</strong> quality characteristics of <strong>the</strong>variety. Because of humid productionconditions in <strong>the</strong> tropics, especiallywhen rain is frequent dUring grainripening. sprouting can be a seriousproblem.Breeding andScreening MethodologyCIMMYT's principal breeding approachis <strong>the</strong> development of a base of widelyadapted, high-yielding and diseaseresistantwheat germplasm thatpossesses attributes necessary toachieve higher productivity undervarying conditions. New lines must bedeveloped qUickly if <strong>the</strong>y are to be ofvalue to <strong>the</strong> less-developed countries.Toward this objective, CIMMYT growstwo generations in Mexico each year,resulting in 8,000 to 10,000 simple andtop crosses which combine differenttraits needed to develop lines SUitablefor those areas of <strong>the</strong> world includedunder <strong>the</strong>ir operational mandate(Table I). The germplasm used in <strong>the</strong>crosses is obtained from allover <strong>the</strong>world and is chosen because of usefulgenes. Before crosses are made,candidates for parents are studiedcarefully for <strong>the</strong>ir agronomic, pathologicand quality characteristics. Decisionsare based on experience and rapidassessment of available data, ra<strong>the</strong>rthan on a genetical analysis of eachparent. The number of lines produceddiffers from year to year, but 40 to 50%

93of <strong>the</strong> plants selected from eachgeneration are subsequently discarded,due to unacceptable seedcharacteristics.As a result of many years' experience inwheat breeding, CIMMYT placesemphasis on <strong>the</strong> pedigree and modifiedbulk breeding systems and <strong>the</strong> use ofsimple and top crosses. This methodpermits rapid combination ofgermplasm and increases geneticdiversity; this is especially importantbecause of CIMMYT's mandate to breedfor diverse climates and regions withdifferent problems.To accomplish <strong>the</strong> breeding objectivesof CIMMYT's Tropical WheatImprovement Program, and to facilitateTable 1. World target environments included under CIMMYT's operational mandateAreasIrrigated AreasDryland areas,500 mm rainfallDrylands areas,500 mm rainfallAluminum toxicareasHighlands areas,above 1500 mTropical areas,23 0 N-23 0 S latitudes,excluding highlandsAreas affectedby salinityCountries and regionsGanges plains of India, IndusValley of Pakistan, Bangladesh,Tarai of Nepal, Egypt, Mexico,Zimbabwe, Lybia, SudanMediterranean North Africa,Middle East, China, Sou<strong>the</strong>rnCone countriesCentral India, parts of <strong>the</strong>Middle East, North Africa,Sou<strong>the</strong>rn Cone countriesBrazil, Central AfricanhighlandsHigh plateaus of Mexico andGuatemala, Andean countries,East AfricaCentral America, Caribbean,South and Sou<strong>the</strong>ast Asia,West AfricaCertain dryland areas of <strong>the</strong>Middle East and North Africa,PakistanImportant diseasesStem rust, leaf rust, stripe rustStem rust, leaf rust, striperust, Septaria triticiBunts, loose smutStem rust, leaf rust,Septaria tritici, Septorianodorum, Fusarium spp.,Helminthosporium spp.,Xanthomonas translucensStripe rust, BYDV,Septoria tritici, Septorianodorum, Fusarium spp.,Helminthosporium spp.,Xanthomonas translucensLeaf rust, stem rust,Fusarium spp.,Helminthosporium spp.,Xanthomonas translucensLeaf rust, stem rust

94<strong>the</strong> distribution and adoption ofsuitable germplasm. a number ofactivities are underway or in <strong>the</strong>planning stages.Sbuttle breecllngThe main activity is shuttle breedingbetween two contrasting climates inMexico. one for a winter crop at CiudadObregon (27°20'N latitude. 40 metersaltitude) and <strong>the</strong> o<strong>the</strong>r for a summercrop at Toluca (l9°N latitude. 2640meters). Both are characterized byendemic rust attacks. and enablebreeders to select for day-lengthinsensitive. Widely adapted types withhigh levels of rust resistance. Selectionscan also be made at Toluca forresistance to septoria and fusariumdiseases. This two-cycle approach alsocuts in half <strong>the</strong> time needed to developa new variety.In addition to <strong>the</strong>se testing sites.CIMMYT regularly employs <strong>the</strong>screening environments of EI Batan(l9°N. 2240 meters) for low rainfallconditions. Tlaltizapan (l8°N. 940meters) for heat tolerance. and PozaRica (21 ON. 60 meters) forhelminthosporium diseases. Similarly.tropical Tampico (22°N. 40 meters) isalso used in cooperation with <strong>the</strong>Instituto Nacional de InvestigacionesAgricolas (lNIA). as a supportinglocation for screening work undertropical conditions. The relationship of<strong>the</strong>se experimental locations is -illustrated in Figure 1.CIMMYT employs additional tropicallocations in o<strong>the</strong>r countries to ga<strong>the</strong>rgenetic information for use in <strong>the</strong>crossing program and for generalscreening activities. Maximumutilization of advanced materialscoming from <strong>the</strong> bread wheat programis also considered a major part of <strong>the</strong>overall strategy of <strong>the</strong> Tropical WheatImprovement Program.In <strong>the</strong> future. shuttle breeding between<strong>the</strong> locations of Poza Rica. forhelminthosporium disease and leaf rustscreening during <strong>the</strong> winter. andTlaltizapan. for heat tolerance andplant-type screening during <strong>the</strong>summer. will be used as an alternativebreeding strategy.Figure 1. Location and elevations of experiment stations in Mexico atwblcb CIMMYT conducts researcb for tropical wbeat

Screening for tropical adaptationThe world wheat germplasm collectionis also being screened for materials withdesirable characteristics which will becontinuously introgressed into <strong>the</strong>breeding program for <strong>the</strong> tropics.In carrying out all of <strong>the</strong> abovementionedobjectives, CIMMYT utilizesa multidisciplinary, coordinatedapproach, involVing <strong>the</strong> participation ofscientists trained in various disciplines.Program ResultsEarly maturityCIMMYT's breeding objective for <strong>the</strong>last few years has been to select anddevelop wheats with earlier maturity. Intrying to obtain such lines. <strong>the</strong> earliestmaturingsegregates are selected fromF2 segregating populations. Forcomparison, <strong>the</strong> variety Sonalika fromIndia is used as <strong>the</strong> early check variety.When a low percentage of plants in asegregating population reachphysiological maturity, <strong>the</strong>y areselected and harvested. Then, as F3s.<strong>the</strong>y are handled in a separate nursery,toge<strong>the</strong>r with o<strong>the</strong>r segregating andadvanced early materials. This systemof handling <strong>the</strong> materials is more forpractical reasons. since damage frombirds and o<strong>the</strong>r pests is particularlysevere on early plants left in <strong>the</strong> field.Using this selection method. advancedlines that are as early as Sonalika havebeen obtained. Two hundred sixty earlylines were tested for yield in CiudadObregon in <strong>the</strong> 1983-84 cycle. Table 2presents 14 lines that were as early asSonalika or earlier. but which havebetter yield potential. These materialsare now in <strong>the</strong> First International EarlyScreening Nursery. toge<strong>the</strong>r with o<strong>the</strong>rearly germplasm in <strong>the</strong> program.HelmiDthosporium resistanceEfforts to improve resistance toHelmtnthosportum spp. began in <strong>the</strong>early 19808. Helminthosporiumscreening work is done at Poza Rica. in<strong>the</strong> tropical area of Mexico. and also at<strong>the</strong> Tlaltizapan station. It is hoped thatgermplasm with both helminthosporiumresistance and heat tolerancewill result from selections at <strong>the</strong>selocations. Helminthosporium resistanceis evaluated on <strong>the</strong> basis of <strong>the</strong>follOWing characteristics:• Slow development of <strong>the</strong> disease;• Acceptable agronomiccharacteristics;• "Good finish," <strong>the</strong> ability to haveclean, fertile and bright heads atmaturity. and• Good seed quality.Table 3 presents <strong>the</strong> best varieties andadvanced lines which were foundresistant to helminthosporium in PozaRica in 1983-84. These lines are now in<strong>the</strong> new Crossing Block and ThirdHelminthosporium Screening Nursery.All of <strong>the</strong>se lines showed betterresistance than BH1146. a resistantcheck variety from Brazil.Heat toleranceIn <strong>the</strong> breeding program. testing hasbeen initiated to identify varieties andadvanced lines haVing tolerance to hightemperature. Heat tolerance isevaluated in Ciudad Obregon byplanting advanced lines in midJanuary. so that early growth stagesoccur during a period of rapidly risingtemperatures. The final performance of<strong>the</strong> lines is evaluated in late April. ThefollOWing characteristics are used asselection criteria for heat tolerance:• Longer leaf duration. <strong>the</strong> "staygreen"characteristic• High tillering capacity• Acceptable spike fertility• Relatively high grain weight• High hectoliter test weight• Relatively high yieldMore than 200 advanced lines wereidentified as haVing some heattolerance in 1983. These same lineswere reevaluated in Ciudad Obregon in

98Table 2. Adnnc:ed line. of bread wheat, I.e.rly or earlier in maturity than Sonalika butwith better yield potential, Ciudad Obregon, Mexico, 1983-84CrOSland pedigreeYieldKg/h. °/0 of Day. toSonalik•.!! m.turityChukar"S"/H02172 6498 124 115CM68199·1 OY1 M-1V-1 M-OVVeery"S"/Huacamayo''S''/lWoodpecker''S''/NAC 6374 122 113CM68810·B-1 V·1 M·2V·1M-OYVeeryS"/Huacamayo''S''/lWoodpecker''S''/NAC 6296 120 113CM6881 0-B·1 V -1 M·2V·2M·OVBluebird/CN067/5/FNITH*3/11144.29/ 5487 117 112*2TH/31*4CTFN/4/SR/6/PVN"S"CM46712-1 V-1 M-1V-1V·OMTOB/CN067/ITOB/8156/3/Calidad//Bluebird/ 5770 115 115CN067/4/BB/INIAl5/Alondra''S''CM59177·1M-1Y-1M-4V-1 M-OVBluebird/CN067/5/FNITH*31/1144.29/ 5281 113 112*2TH/31*4CTFN/4/SR/5/PVN"S"CM46712-1 V-1M-1V-2V-OMHI669/41T0rdo''S''/HD832*2/ITOB/31T0rdo''S''/ 5692 110 1142*H0832CM6255O-1 Y-1 M·2Y-1 M-3V-1 M-OVManantiaIIlCN067/PJ/3/NAC/4/Emu''S''·00ugga 5379 107 113CM60960-B-1 Y-4M-1 Y-4M-1 Y -1 M-1 Y -1 M-oVAlondra''S''/ Altar''S'' 5634 107 113CM68045-3Y-1 M-1 V -OMVaco''S'' 4958 106 113CM41195-A-13M-2V-3M-1Y·1M-OYH0669.1 B/Chiroca''S'' 4677 104 113CM62536-5V-1 M·1 Y -3M-1 V-1 M-OYIAS54/AIondra''S'' 5932 103 115CM56805-3Y-1 Y-4M-1 V·1 M-1 y-oMCOC/Bluejay''S''IINAC/Buckbuck''S'' 5307 103 115CM63992·5M-1V-1M-7V-1M·3V-oMRedpoll/Ani''S''I/PVNlVeery''S'' 5363 102 114CM68735-1-4Y -1 M-3V·3M-OVSonalika (early check) 115~/ Percent of Sonalika for <strong>the</strong> respective yield trial

97Table 3. Best advanced lines of bread wheat resistant to Helminthosporium sativum,Poza Rica, Mexico, 1983-84Disease score!} DiseasedCross and pedigree Heading Flowering Milk grainstage (°/0)JUP/4/7C/Pato(B)/3/LR64/INIAIIINIAIBluebird/51ANA 3 4 10CM37760-C-21 Y-2M-l Y-3M-9Y-OMRD2206/Hork"S" 2 3 4 20CM39808-58M-2Y-4M-l Y -1 M-lY-OBLira''S'' 2 3 4 15CM43903-H-4Y-1 M-l Y-3M-2Y-OBLira"S" 2 4 5 16CM43903·H·4Y-1 M-lY-3M-3Y-OBCI14227/TRMIIMadeira''S'' 2 4 4 14CM47943-V-5M-3Y-l M-1Y-OYAlondra"S"/IAS58 3 4 5 16CM53481~Y -1 Y-4M-1Y -1 M-1Y-oMBluejay"S"IITOB/Chanate 2 3 5 12CM55912-1 OY-3Y-1 M·3Y-2JO-OJEVeery"S"/Sunbird''S'' 2 3 4 12CM61981-4Y -1 M~Y-3M-oYH1669/4/Tordo''S''/2*HD832/ITOB/31Tordo"S"!*2HD832 3 4 4 10CM62550-1 Y -1 M-2Y-1 M-lY-OMKea''S''/4/Kalyansona/BluebirdIICJ"S''/3/Alondra''S'' 2 3 4 18CM64617-9M-l Y-l M-l V-OMAUlUP3011IGallo/SX/3/Pewee"S"/4/Maipo"S"/Maya"S"I/Pewee"S" 3 3 5 12CM67245-C·l M-2Y-1 M·3Y-OMAntbird''S''/Yaco"S'' 2 4 6 12CM67618-2Y-3M-3Y-2M-OYBHl146 (resistant check) 2 4 5 20CIAN079 (susceptible check) 5 6 9 58!o/ Scoring scale 0 to 9 (0 = highly resistant, 9 = highly susceptible)

981984, and a high percentage wereconfirmed as being heat tolerant. Since<strong>the</strong> program is in <strong>the</strong> initial stage ofheat-tolerance screening, no crosseshave yet been made for this purpose.However, <strong>the</strong>re are plans to initiatebreeding for heat tolerance within <strong>the</strong>next two years.Drought resistanceDrought resistance is defined here as"<strong>the</strong> ability of one genotype to be moreproductive with a given amount of soilmoisture than o<strong>the</strong>r genotypes." From<strong>the</strong> beginning, CIMMYT's objective inthis area has been to producegermplasm which combinesresponsiveness under both droughtconditions and high-yieldingenvironments. To achieve this goal, abreeding program has beenimplemented in which spring x wintermaterials are subjected alternately toreduced moisture levels and optimumirrigated conditions. The shuttle takesplace between Ciudad Obregon in <strong>the</strong>winter season, and <strong>the</strong> highlandlocations of EI Batan and Huamantla in<strong>the</strong> summer.The performance of 12 advanced linesin Ciudad Obregon (two irrigations) andEI Batan (rainfed conditions) are givenin Table 4. It appears from this tablethat <strong>the</strong>se lines will perform well underboth environmental conditions. Thesematerials are in <strong>the</strong> new DroughtScreening Nursery for internationalyield testing, which will provideadditional data on <strong>the</strong>ir stability.ConclusionsThe CIMMYT Tropical WheatImprovement Program has completedtwo years of research to identifysuitable lines for tropical conditions.The crossing program has continuouslyutilized adapted germplasm as parentallines in crosses, resulting in a largenumber of segregating populations.Materials selected from <strong>the</strong> breedingprogram, as well as germplasm fromcountries around <strong>the</strong> world, have beendistributed to target areas throughCIMMYT's international nurserynetwork. The materials are classified fortraits and entered into <strong>the</strong> follOWingnurseries:• Helminthosporium ScreeningNursery• Drought Screening Nursery• Heat Tolerance Screening Nursery• Early Screening Nursery• Scab Resistant LinesThese nurseries serve as a means toverify resistance and as mechanisms forgermplasm introduction into nationalprograms.In cooperation with CIMMYTpathologists, techniques for massscreening for such major tropicaldiseases as helminthosporium havebeen developed. These techniques arenow being fur<strong>the</strong>r refined.In <strong>the</strong> years to come, CIMMYT willendeavor to recombine genes for highyield, early maturity under hightemperature conditions and resistanceto leaf rust and helminthosporium. Inspite of <strong>the</strong> fact that only about 4 % ofits total wheat budget is directly relatedto tropical wheats, CIMMYT willcontinue to integrate and test all of itsadvanced lines for <strong>the</strong> improvement ofgermplasm for <strong>the</strong> tropical wheat areas.

99Table 4. Highest yielding advanced lines of bread wheat, grown under two irrigation regimes,Ciudad Obregon, 1982-83, and under rainfed conditions, EI Batan, 1983Ciudad ObregonEI BatanYield b/ o of Yield b/ o ofName and pedigree (kg/ha) Ures 81 (kg/ha) Genaro 81Veery"S" 5976 118 5480 119CM33027-F-15M-4Y-4M-3Y-2M-1 Y -OMTyrant"S" 5672 118 5113 111CM4061 0-25Y-3M-3Y-1 M·2Y-OBVeery"S" 5835 115 4707 102CM33027-F-12M-1 Y -12M-1 Y-2M-OYVeery"S" 5806 115 5360 116CM33027-F-15M-500Y-OM-75B-OYFlycatcher"S" 5335 111 5447 118CM43598-11-8Y -1 M-5Y-2M -2Y-OBMaya/Moncho"S"//KVZITRM 5333 110 6133 133CM44083-N-2Y-2M-1 Y-1 M-1 Y -1 M·OYVeery''S'' 5430 107 5533 1?0CM33027-F-15M-500Y-OM-98B-OYPAT1 01Alondra"S"1/PAT72300/3/PVN"s" 5739 104 4280 94CM49922·1M-2Y·1Y·1M-3Y OMT anager"S" 5220 103 5147 112CM30697-2M-8Y-7M-1 Y·1 B-OYVeery''S'' 5198 103 5567 121CM33027-F-15M-500Y-OM-66B-OYBluebird/ON//CN067''S''/NO/3/PVN"s" 5446 101 4973 108CM46718-28M-1 Y -1 M-3Y-OMAZ//CHR/DD.05P/3/F12.71/Bolillo"S" 5437 101 5013 109CM48326-A-3M·1 Y·1 M-2Y·1 Y -OM

100Wheat Germplasm Development forHeat and Drought Tolerance for NigeriaF.e. Orakwue, Institute for Agricultural Research,Ahmadu Bello University, Zaria, NigeriaAbstractHeat and drought constitute two oj <strong>the</strong> major wheat production constraints in<strong>the</strong> dry tropics. In Nigeria. <strong>the</strong>se environmental stresses restrict wheatproduction to some irrigated areas in <strong>the</strong> north between 10 and 13oN latitudes.where temperatures during <strong>the</strong> cool "harmattan" period (November to February)range between 5 and 30°C. In order to overcome <strong>the</strong> limitations caused by hightemperatures and lack oj moisture. <strong>the</strong>re is a need to develop wheat germplasmwith heat and drought tolerance; an intensive screening programJor <strong>the</strong>sestresses is suggested. The potentials ojsome exotic germplasm are emphasized.and some characteristics that might enhance tolerance to heat and droughtstresses are discussed.Heat and drought are common wheatproductionproblems in Nigeria, as wellas in most regions withi!} <strong>the</strong> drytropics. Little attention has been paid tovulnerabilities associated with <strong>the</strong>seenvironmental stresses over <strong>the</strong> years(1); however. some work has been doneon <strong>the</strong> effects of temperature on wheatunder controlled conditions (9,18.11.3.20). Such studies were limited to a fewgenotypes for differential temperaturetolerance. In ano<strong>the</strong>r study. Sisodia.et al. (21) identified ten genotypes ofTriticum spp. that have relatively hightemperature tolerance.As in <strong>the</strong> case of heat stress, <strong>the</strong>re isstill no sound information on a specificdrought-resistance mechanism,although information needed to explain<strong>the</strong> basic physiological principles fordrought tolerance has continued toincrease. Fischer et al. (8) defineddrought tolerance in agriculture as <strong>the</strong>ability of a crop to give an economicyield under low moisture conditionsand to give a maximum yield underoptimum conditions. Attempts havebeen made to classify variousmechanisms by which drought mightbe tolerated. May and Milthorpe (12)called <strong>the</strong>m drought escape anddrought endurance, while Levitt (10)referred to <strong>the</strong>m as drought avoidanceand drought tolerance. Thesedefinitions and terms are also utilizedin this paper. Fischer and Maurer (7)screened for drought tolerance in alarge number of tall and dwarf wheats.In that study, <strong>the</strong>y attempted toseparate effects due to drought escapeand those due to <strong>the</strong> operation ofresistance mechanisms. Theyconcluded that tall wheats were moretolerant to drought.Environmental Limitationsof <strong>the</strong> Nigerian Wheat RegionIn general, high temperature hasrestricted wheat production in Nigeriato certain parts of <strong>the</strong> nor<strong>the</strong>rn states,which lie between 10 and 13°Nlatitudes, mainly in <strong>the</strong> Sudan savanna.Here <strong>the</strong> cold "harmattan" period(November to February) provides <strong>the</strong>required temperatures, ranging from 5to 30°C. Wheat is sown in midNovember, and harvested at <strong>the</strong> end ofFebruary or in early March. Thus, onlycultivars with 70 to 120 day maturitiesare usable. High temperature isdetrimehtal to <strong>the</strong> establishment of anearly-sown wheat crop, and to grainfilling in a late-sown crop. If <strong>the</strong> crop is

101very late, high temperatures at <strong>the</strong> endof February or in early March. while <strong>the</strong>crop is in an<strong>the</strong>sis. can cause sterility of<strong>the</strong> florets. resulting in very low yields.The massive irrigation schemes inNigeria's wheat-growing regions. <strong>the</strong>Chad, <strong>the</strong> Hadehia-Jama'are and <strong>the</strong>Sokoto-Rima river basins in Barno,Kano-Bauchi and Sokoto states.respectively (Figure 1). are <strong>the</strong> mainvehicles to <strong>the</strong> possible attainment ofNigeria's green revolution (16).However, <strong>the</strong>se rivers are fed by scantyrainfall, 300 to 500 mm in Barno state,600 to 900 mm in Kano/Bauchi and400 to 600 mm in Sokoto. It is spreadover a short period. mainly from July toSeptember; thus. water is expensiveand may be limiting, especially in yearsof low rainfall.The effect of drought is usually verysevere on wheat. as it not only cuts offwater needed for normal metabolism.but also decreases <strong>the</strong> supply ofnutrients from <strong>the</strong> soil. Under suchstress situations. farmers face aconsiderable amount of risk. There is,<strong>the</strong>refore, a need to develop wheatgermplasm with a reasonable amountof heat and drought tolerance, in orderto stabilize yield under presentconditions and to effect a moresuccessful extension of wheatproduction into sou<strong>the</strong>rn Nigeria.Germplasm Improvementin NigeriaIn <strong>the</strong> last two decades. over 15,000wheat varieties and lines have beenintroduced and screened in Nigeria by<strong>the</strong> Institute for Agricultural Research,Ahmadu Bello University. Zaria. Theobjective has been to identify cultivarswhich are high yielding under Nigerianconditions and possess acceptablebread-making qualities (14). Wheatintroductions have come mostly fromCIMMYT. <strong>the</strong> International Center forAgriculture Research in <strong>the</strong> Dry Areas(ICARDA) in Syria, <strong>the</strong> Food andAgricultural Organization (FAO) ando<strong>the</strong>r parts of <strong>the</strong> world (14.15).Although INIA 66. Indus 66 andMexipak are grown in some areas of <strong>the</strong>South Chad Scheme. only five varietieshave been recommended by <strong>the</strong>Figure 1. Wheat-growing regions in Nigeria

102Institute for Agricultural Research.These include two tall non-Mexicanwheats. Tousson and Florence Aurore8193. and three Mexican semidwarfs.Sonora 63. (Lee x NI0B}GB55}GB56and Siete Cerros (l4.15.16). AlthoughSiete Cerros is <strong>the</strong> most popular varietyand is cultivated allover <strong>the</strong> wheatgrOWingregion (especially In <strong>the</strong> KanoRiver Project). <strong>the</strong> o<strong>the</strong>r varieties arebeginning to gain acceptance.Performance ofNigerian SelectioDsTable 1 shows <strong>the</strong> performance oftwenty lines and varieties in replicatedtrials grown at four locations in Nigeria.The Nigerian Regional Wheat VarietyYield Trial 1982-83 was grown inKadawa. Samaro. Bakura andGanawuri. with <strong>the</strong> variety Slete Cerrosas <strong>the</strong> check. The lines/varieties whichperformed well were Pavon 76. 7C-On xINIA-B.Man. Kalyansona x V534.Junus x Y50E-Kal3/Pal. (Tf-CN067/Bluebird-CNO)Za. HD832-55 x CNOJAR. Moncho"S". C271 x Sonora 64.Jupateco. and Super X. with meanyields ranging from 3450 kglha to 4350kglha. It is important to note that yieldshad been higher in previous years.particularly in Kadawa where birddamage has come to constitute yetano<strong>the</strong>r production problem in earlysownwheat.Ano<strong>the</strong>r experiment was conducted inBakura in <strong>the</strong> 1982-83 grOWing seasonto investigate <strong>the</strong> most critical growthstages for moisture stress in fivelines/varieties of bread wheat and.Table 1. Yields of entries in <strong>the</strong> Nigerian Regional Wheat Variety Trialover four locations, 1982-83Grlin yield (kg/hi)Yield ISVlrietv/croll KICI_I Slmlru Sikurl Glnlwuri Mien a/a of checkPavon 76 4305 3725 5000 4350 4345 1477C·ON x INIA·B.MAN 2963 3313 6663 3150 4022 136KAL x V534 3325 4438 5375 2280 3854 130(TF x CIANO 67/Bluebird·CIANO)ZA 2888 3750 5688 2775 3775 128Junus x Y50e·KAL3/PAL 3713 3813 5263 2325 3775 128HD832·55 x CIANO.JAR 2563 4063 5350 2850 3706 125Moncho"S" 3238 3250 4000 3975 3615 122C271 x Sonora 64 3000 3475 5213 2550 3559 120Jupateco 2833 3475 3975 3675 3489 118Super X 2950 3250 5425 2175 3450 117NP876·164 Roch/CIANO"S"-Bluebird 2115 3625 4175 3675 3412 115Barouk 2500 3125 5838 2115 3409 115BYC"S" x 3Ka1yansona x Kalyansonl-Bluebird 2813 3688 3888 3000 3347 113Y50e-Kalyansona 2713 4063 3538 2700 3253 110Nacozari 76 3120 3625 3600 2700 3261 110(GB80·5892 x MP·33) 2363 3188 5413 1650 3154 107PJ62-GB55 x NAI60 3370 2875 4363 1725 3083 104Pi62·Frond/Pi62-Mazoe xMexipak 65 3363 2913 3863 1875 3003 102Fury-Siete Cerros 1600 3063 4088 3000 2937 99Siete Cerros (check) 2900 3338 3563 2025 2956 100Me8n 2935 3503 4714 2732S.E. 491 431 412 469Source: Orakwe 8nd Olugbemi (16)

103hence, select for drought tolerance. Theexperiment consisted of 45 treatmentcombinations, five varieties and nineirrigation treatments (Table 2).Due to wide variations betweenreplicates of different treatments, <strong>the</strong>rewas no significant difference between<strong>the</strong> varieties. Interaction betweenirrigation treatments and varieties wasalso not significant. Of all <strong>the</strong> varieties.only HD832-55 x eNO-JAR wasseriously affected when irrigation waswithheld twice consecutively at <strong>the</strong>jointing stage (T7). Missing twoirrigations at <strong>the</strong> flowering stage(T8) affected all of <strong>the</strong> varietiesconsiderably. Varying yield reductionswere observed in all o<strong>the</strong>r treatments,but it appeared that <strong>the</strong> two mostcritical stages for moisture stress are T7and T8, Jointing and an<strong>the</strong>sis.Characteristics AffectingSelection for Heat and DroughtToleranceEarlinessAn understanding of a stress-tolerancemechanism is necessary in order tocorrectly suggest useful characteristicsby which a plant can tolerate stress.Under Nigerian conditions, it appearsthat <strong>the</strong> main mechanism leading togood performance in wheat is escape oravoidance. The variety should grow andmature within <strong>the</strong> cold period, Le., withmaturities of 70 to 120 days. Thus.only early or medium-early lines!varieties will perform well. This is alsotrue for drought tolerance. sinceearliness enhances water economy.YieldIn addition to earliness. superiority inyield under optimal conditions isnecessary for both heat and droughttolerance. According to Blum (4)varieties with superior yield at optimallevels will also yield relatively wellunder sub-optimal levels.AdaptabiUtyWide adaptability is a necessary factor,since it is believed that. when stresstolerance is present in a variety. it maybe expressed as an unidentifiedcomponent of stability in performanceover various environments (4.11.17).Developmental synchronyPlants should tiller uniformly, holdmost of <strong>the</strong>ir leaves intact and matureuniformly.Test weightThe grains of plants should have goodtest weight, which results from goodand uniform grain filling.Spike fertUltyIncreased fertility of <strong>the</strong> spikes assuresthat most florets will be fertile understress conditions, as well as at optimallevels.Table 2. Effects of variety and moisture stress on grain yield of bread wheat, Bakura,Nigeria, 1982·83Grain yield (kg/ha) according to i'rrigation treatment!./Variety T1 T2 T3 T4 T5 T6 T7 T8 T9HD832-55 x CIANO-JAR 2747 1907 1720 1813 2087 1687 833 1587 2220Super X 2627 1893 1960 1667 1887 1987 1433 1147 1820(TF x CIAN067/Bluebird-CIANO)ZA 1840 2033 1860 1887 2527 1960 1733 1187 1867NP876-164 x Roch/CIANO"S"-Bluebird 2380 1960 1960 2020 1860 1600 1793 1453 1720Pi62·Frond/Pi62-Mazoe x Mexipak 65 2293 2427 1867 1487 2427 1860 1667 1333 2120!,/ T1 = control, 19 irrigations; T2 = one irrigation withheld at tillering; T3 = one withheld at jointing; T4 = one withheldat flowering; T5 = one withheld at grain filling; T6 = two irrigations withheld at tillering; T7 = two withheld at jointing;T8 = two withheld at flowering; T9 = two withheld at grain fillingSource: Aremu and Orakwe (2)

104Leaf areaThere should be a small leaf area interms of number and/or size. Althoughit is not easy to generalize. thischaracteristic seems to be essential inorder to reduce evapotranspiration and.hence. enhance drought tolerance (19).TilleringSince <strong>the</strong> number of tillers depends on<strong>the</strong> number of leaves (as tillers areinitiated in leafaxils). it follows that <strong>the</strong>drought-tolerant variety should havereduced tillers (19).Water utilizationThe drought-tolerant line should have<strong>the</strong> ability to efficiently utilize availablewater. Such a variety should maintainits photosyn<strong>the</strong>sis and growth at lowwater availability. The developmentalplasticity of <strong>the</strong> variety should be suchthat it gives an economic yield underwater stress. as well as best yield undergood moisture situations. Thisincreased efficiency in water use couldresult from a restriction on <strong>the</strong> relativeability of <strong>the</strong> plant to extract waterfrom <strong>the</strong> soil during early crop growth.leaving more water to support <strong>the</strong> plantin <strong>the</strong> grain-filling stage. Thischaracteristic might be developedthrough selection of plants with erectleaves and reduced tillering (6).Density toleranceDow (5) showed that maize hybridsresistant to density stress were alsomore drought tolerant. Thus. densitytrials may also help in selection fordrought tolerance. as plants resistant todensity stress should have a relativelygreater ability to withdraw water from<strong>the</strong> soil.Root systemsA good root system is necessary fortolerance to both drought and moisturestress. because it enhances early plantestablishment. as well as efficiency in<strong>the</strong> water-uptake capacity of <strong>the</strong> plant.ConclusionsIn Nigeria. high temperature anddrought constitute problems for wheatproduction. Fortunately, <strong>the</strong>seproblems are not as erratic as are someproblems under rainfed conditions ino<strong>the</strong>r tropical countries. Hightemperatures mainly affect <strong>the</strong> plantduring establishment and tillering andduring <strong>the</strong> grain-filling stage. Hightemperatures are <strong>the</strong> main limitation towheat production in sou<strong>the</strong>rn Nigeria.Drought, on <strong>the</strong> o<strong>the</strong>r hand. is periodic.Drought-tolerant lines/varieties willinvariably enhance water economy.Thus. both heat and drought toleranceare desirable characteristics to beincorporated into Nigerian selections, inorder to stabilize yield and increaseproduction.Performance of adapted wheatgermplasm indicates that yieldsranging from 3 to 4 tlha are possibleunder optimum conditions. Therefore.heat and drought-tolerant lines yielding1.5 to 2.5 tlha under stress conditionsand up to 4 tlha under optimumconditions should be selected. It isdifficult to generalize as to genetic traitswhich enhance heat and droughttolerance, but some of <strong>the</strong>characteristics described above havebeen shown to be relatively effective infield crops. and in wheats in particular.

106References1. Anonymous. 1972. Wheat. InGenetic Vulnerability of MajorCrops. Division of Biology andAgriculture National ResearchCouncil. National Academy ofScience.Washington. D. C..USA. Pp. 151-152.2. Aremu. J.A.• and F.C. Orakwue.1983. Plant Breeding AnnualReport 1982-83. Department ofPlant Science. Ahmadu BelloUniversity. Zaria. Nigeria.3. Asana. RD. 1974. Physiologicalresponses of wheat to early sowingunder non-irrigated cultivation andlate sowing under irrigation. IndianJournal of Genetics 34:109-96.4. Blum. A. 1979. Geneticimprovement of drought resistancein crop plants: A case of sorghum.In Stress Physiology in Crop Plants.H. Mussel and RC. Staples. eds.Wiley Interscience. New York. NewYork, USA. Pp. 429-445.5. Dow. E.W. 1981. Resistance todrought and density stress inCanadian and European maize (Zeamays L.) hybrids. M.Sc. Thesis.University of Guelph. Ontario,Canada.6. Evans. L.T.. I.F. Wardlaw andRA. Fischer. 1975. Wheat. In CropPhysiology: Some Case Histories.L. T. Evans. ed. CambridgeUniversity Press. Cambridge,England. Pp. 101-149.7. Fischer. RA.. and R Maurer. 1978.Drought resistance in wheatcultivars: 1. Grain yield response.Australian Journal AgriculturalResearch 29:897-912.8. Fischer. K. S .• E.C. Johnson andT.O. Edmeades. 1983. Breeding andselection for drought resistance intropical maize. CIMMYT. EI Batan.Mexico.9. Friend. F.D.C. 1966. The effect oflight and temperature on <strong>the</strong>growth of cereals. In The Growth ofCereals and Grasses. F. L. Milthorpeand J.D. Ivins. eds. Butterworths.London. England. Pp. 181-199.10. Levitt. J. 1972. Responses of Plantsto Environmental Stresses.Academic Press. New York. NewYork. USA.11. MacDowall. F.D.H. 1973. Growthkinetics of marqUiS wheat versusmorphogenic dependence.Canadian Journal of Botany51:1259-65.12. May. L. H.. and RL. Milthorpe.1962. Drought resistance of cropplants. Field Crop Abstracts15:171-179.13. Olugbemi, L.B. 1973. Wheatresearch in Negeria. In Proceedingsof <strong>the</strong> Fourth FAOlRockefeUerFoundation Wheat Seminar.Tehran. Iran. May 21-June 5. 1973.Pp.92-96.14. Olugbemi. L.B.. F.C. Orakwue andE.V. Aguda. 1981. Preliminarystudies on <strong>the</strong> effects of varieties.seed rates and levels of nitrogenfertilizers on <strong>the</strong> yield attributes ofwheat (Triticum aesttvum L.) underNigerian conditions. Smari Journalof Agricultural Research 1:95-99.

10615. Orakwue, F.C., L.R Olugbemi andE.V. Eguda. 1982. Irrigated wheat:A boost to food production inNigeria. In Proceedings of <strong>the</strong>Fourth Mro-Asian RegionalConference of ICID I: 14. Pp. 229237.16. Orakwue, F.C., and L.B. Olugbemi.1984. Wheat production: prospectsof self-sufficiency in Nigeria. Apaper presented at <strong>the</strong> Second JointNAFPP Workshop, Zaria, Nigeria.February 19-23, 1984.17. Quisenberry, J.E. 1982. Breedingfor drought resistance and plantwater efficiency. In Breeding Plantsfor Less Favorable EnVironments.M.N. Christensen and C.F. Lewis,eds. John Wiley and Sons, Inc.•New York. New York, USA. Pp. 193212.18. Rawson, H.M. 1970. Spikeletnumber. its control and relation toyield per ear in wheat. AustralianJournal of Biological Sciences23:1-15.19. Richards. RA. 1983. Manipulationof leaf area and its effects on grainyield in droughted wheat.Australian Journal of AgriculturalResearch 34:23-31.20. Sisodia, N.S. 1977. Photoinsensitivityin wheat breeding.Paper presented at <strong>the</strong> NationalSeminar on Genetics and WheatImprovement. PAN, Ludhiana.India. February 22-23, 1977.21. Sisodia, N.S., K.P. Singh andRR Sheopuria. 1979. Variabilityfor high temperature tolerance inwheat. In Proceedings of <strong>the</strong> FifthInternational Wheat Genetic<strong>Symposium</strong>, S. Ramamijam, ed.Indian SoCiety of Genetics andPlant Breeding. New Delhi, India.Pp.216-224.

107Breeding Wheats for Heatand Drought Tolerance in Central IndiaY.M. Upadhyaya and K.N. Ruwali, Indian Agricultural ResearchInstitute, Indore, IndiaAbstractCondtttonsfor wheat cultivation in central India impose severe drought andtemperature stress. High temperatures at sowing time (32 to 35°C) and atmaturity (30 to 35°C) cause defective germination and grain dehydration.respectively; frost at ear-emergence stagefrequently causes 50 to 100% loss inyield. In breedingfor drought tolerance in India. local cultivars have beenutilized; disease resistance. which is also very important. is introduced at <strong>the</strong>same time. The cultivars C306. Sujata. Hy65. NI5439. N59. A9-30-1 andMeghdoot have been developed. and genetic improvement has been madeforcharacters. such as number ofears per plant. grain weight per spike and 1000grain weight. From about 300 cultivars testedfor temperature tolerance. sevenpossess good tolerance and comparefavorably with Hindi 62; <strong>the</strong>se alsoincorporate resistance to rusts and leaf blight. Some of <strong>the</strong> cultivars. such asH11011. H11012. Raj 1771 and Raj 1777. have proved to be promisingfor heattolerance. Afew lines. recently receivedfrom CIMMYT. also appear to bepromising. Encouraging results have been obtainedfrom spring x Winter crossesand will befur<strong>the</strong>r exploited.In Central India. stresses of droughtand temperature affect wheatcultivation, under both rainfed andirrigated conditions (Figure 1). Soilmoisture at seeding depth is directlyrelated to germination, and temperaturealso plays a major role. The relationshipis shown in Table 1.50456o 40';35'"'.330e25Q)S20~ 1510Max. temp.5 L_~==~~~~~~e!:!=~i!::L.r--Sept. Oct. Nov.o Rain once in 5 yearsCJSoWing periodE;ZJFrost-prone periodDec. Jan. Feb. Mar.• Rain twice in 5 yearsDEar-emergence period~MaturityperiodFigure 1. Weatber conditions for tbe wbeat-crop season, Indore, India.1979 to 1984

108While germination increased withincreasing soil moisture in <strong>the</strong> seedingzone. germination was higher in <strong>the</strong>colder months of December andJanuary than it was with highermoisture levels in mid-October.In <strong>the</strong> Bhal tract of Gujarat.temperatures between October andDecember vary between 35 and 39°Cmaximum and 22 and 25°C minimum.At 30.2°C mean average temperaturesin 1979. germination was 56%. Insubsequent years. a decrease in meantemperature gave a linear increase ingermination. By 1983. when <strong>the</strong> meantemperature was 26.5°C. germinationpercentage was 84%.Soil cracking is a regular phenomenonafter January. and causes extensiveroot damage in <strong>the</strong> upper 60 cm. Frostconditions cause spikelet sterility whenear emergence coincides with a suddendrop in temperature. Total crop losseshave occurred with Kalyansona.WH 147 and Raj 911 under irrigatedconditions. Continuous hightemperatures in <strong>the</strong> low elevationregions of Maharashtra and MadhyaPradesh have resulted in <strong>the</strong> floweringof Kalyansona within 45 days. whichreduced yield by 60 to 70%.Breeding for drought and temperaturetolerance has been going on for <strong>the</strong> pastfive decades in central India. Selectionsfrom <strong>the</strong> local durums A206. EK69 andKathia 25. and <strong>the</strong> bread wheat. Ujjain22. have proved to be very Widelyadapted. Hybridization betweendurums and T. dtcoccums produceddrought-resistant wheats. such as Jayand Vijay as early as 1936. Later. <strong>the</strong>durum cultiv.ar. Gaza. and Gabo andseveral Kenya wheats were used in acrossing program with local varietiesand strains resistant to rusts and blight:NP401. NP404. A9-30-1. Meghdoot.Bijaga Yellow and N59 (durums) andHy65. NP832. Narmada 4 and Mukta(bread wheats) were used in <strong>the</strong>program. Three varieties. C306. Sujeta.an improvement over C306. andNI5439 (RFPMl80 x NP7103). proved tobe outstanding for drought andtemperature tolerance throughout <strong>the</strong>central and nor<strong>the</strong>rn parts of <strong>the</strong>country. C306 has a winter wheat.Regent. in its pedigree. An analysis of<strong>the</strong> genetic improvements comparedwith <strong>the</strong> respective local parents ispresented in Table 2.The ability of <strong>the</strong> local cultivars toestablish better plant populations underlow moisture conditions seems to bedue to natural selection over centuries.as is <strong>the</strong>ir ear production and yield perTable 1. Effect of temperature and soil moisture on germinationof wheat, IndiaSowingdateAverage meantemperature (OC)!.Iover 3 weeksSoil moisture(010 at 7-8 emdepth)Germination(°/0)Oct. 15Oct. 29Nov. 20Dec. 3Dec. 31Jan. 1225.024.622.121.417.316.416.918.219.918.116.415.022.749.861.840.140.228.7al M(maximum +minimum)- ean temperature = 2

109unit area. However, looking at some of<strong>the</strong> yield components. <strong>the</strong>re has been'improvement in <strong>the</strong> number of ears perplant in A9·30·1 and Hy65 and in grainnumber per ear and grain weight perear in A9-30-I. Hy65 and C306; testweight has been improved in Meghdoot,Hy65 and C306.Screening and Evaluationfor Temperature ToleranceDuring <strong>the</strong> past six years. more than300 varieties from different breedingstations have been screened at anumber of centers over differentlatitudes (12 to 31 ON) and longitudes(74 to 84°E). Sowing was done fromSeptember 20th until December anddata such as germination, productiveears. grain yield and l000-grain weightwere collected. Maximum temperaturesranging from 30 to 35°C. andminimum temperatures of 10 to 21°Cwere encountered. It was observed that<strong>the</strong> varieties showed very poorgermination before October 20th. and<strong>the</strong>n improved until November 15th;after that date germination againdecreased. The number of days to earemergence was profoundly influencedby latitude and prevailingtemperatures. Heading took 50 to 75days at Dharwar (12°N), 60 to 90 daysat Niphad (20 0 N). 65 to 100 days atIndore (22°N) and 100 to 125 days atGurdaspur (31 ON). With early SOWing,emergence was delayed. Phenologicalstudies revealed that varieties whichflowered very early had better yield inpeninsular India. and those floweringmid-late were best adapted in <strong>the</strong>central region. Late types, with 105 to115 days to ear emergence. weresuperior in <strong>the</strong> north. The prostratecharacteristic combined with thinnarrow leaves during tillering andnarrow. semi-erect leaves on <strong>the</strong> stemswere desirable. This reduced direct soilmoisture evaporation andevapotranspiration losses from <strong>the</strong>plants. An adverse effect of late sowingon kernel development has beenobserved. In early October sowings.Table 2. Genetic improvement shown by improved cultivars compared to local cultivarsunder stress conditions, India, 1974 to 1977§No. of No. of Yield No. of No. of Grain weight! 1000-grainCultivar seedlings/m2 ears/m2 (g/m2) ears/plant grains/ear ear (g) weight (g)Durum wheatsKathia (local) 195 287 227 1.5 20.1 0.79 49.3Malvi (local) 197 272 242 1.4 19.2 0.89 49.1Meghdoot 152 208 184 1.4 17.5 0.88 54.1(100) (91) (99) (110)Arnej (local) 245 266 279 1.1 20.6 1.05 45.6A9-30-1 180 261 320 1.5 32.7 1.23 41.8(136) (159) (117) (92)Bread wheatsPssi (local) 215 304 233 1.4 15.9 0.77 41.2HY65 141 246 217 1.7 20.4 0.86 42.7(121) (128) ( 112) (104)C306 154 209 228 1.4 18.1 1.09 45.0(100) (118) (142) (109)!.f Numbers in brackets = percent of local

110average lOOO-grain weight was 42grams; in late October sowings. it was40 grams and. in early Novembersowings. 34 grams.After considering phenologicalcharacters such as flowering andmaturity. effective tillers. grainproduction per ear. yield ability anddisease resistance. varieties such asHIlOll. HIlOI2. Raj 1771, Raj 1777.Ju H72-4 and VL421 have beenidentified as heat tolerant. HI 1011 andHIlOl2 compared favorably with Hindi62. which was identified in 1973 and iscurrently <strong>the</strong> best cultivar. All newvarieties are resistant to <strong>the</strong> rusts andleaf blight. while Hindi 62 suffersheavily. Although Hindi 62 producesmore ear-bearing tillers. grainproduction per ear and kernel weightare low. The Indore selections 1011.developed from <strong>the</strong> cross E4870CC303M5292)666-5 x Perico. and 1012. from<strong>the</strong> spring x winter cross NIOB-PI4101-65-39/Kal-Bb. show promise. Ingeneral. productivity is lower in moretropical areas like Niphad. Dharwar andHyderabad. intermediate in <strong>the</strong> centralregion and high in <strong>the</strong> nor<strong>the</strong>rn belt.Generally. <strong>the</strong>re is no moisture stress in<strong>the</strong> north.Utilization ofWinter :It Spring CrossesThe prolific root system of winterwheats is being utilized in breeding.Crosses with <strong>the</strong> University ofNebraska's high protein lines haveyielded some promising material. Twolines from <strong>the</strong> cross NP839 x VI027compare favorably with SUjata. Studieson FIS and parents have shown thatMukta. Raj 1777 and NI5439 exhibit a22 to 79% increase in grain productionand a 20 to 58% increase in productivetillers. Among winter wheats. Favorit.Maldova. Roussalka and Sava havegiven better combinations. SUjata andC306 frequently produce necrotichybrids and. <strong>the</strong>refore. cannot beexploited in direct crosses. Recently.some promising lines have beenidentified from <strong>the</strong> CIMMYT 1982-83Drought Screening Nursery. Fourpromising lines are from spring xwinter crosses Klim x D6301-Nai601Kalyansona-BluebirdCentry 19).TJB845-Misc. Hart 599 xMHM/Sapsucker"S" (entry 25) andPMF-LFN x Chiroca"S"Centry 28) and(Pi"S"-MAZOE x CN067/LFN)Chiroca"S"(entry 27). The spring wheatcrosses. Veery"S"Centries 48 and 50).Kalyanson-Bluebird x Moncho"S"Centry66). Neelkant"S"Centry 67). K4500.2Bluejay"S"Centry 70). JUP-Emu"S" xGrajo"S" =Flycatcher"S"Centry 77) andBuckbuck"S",Bluejay"S"(entries 98and 99) have given better stands andhigher yields than <strong>the</strong> check varietiesUres and Sujata under completedryland (conserved moisture)conditions.Future StrategyApart from <strong>the</strong> ability to establish wellunder stress conditions. <strong>the</strong> ability toremain in <strong>the</strong> vegetative phase for alonger duration. even thoughtemperatures are high. is <strong>the</strong> mostdesired character for wheat for centralIndia. These traits have been observedin some of <strong>the</strong> local and improvedcultivars. and must be combined withbetter disease resistance. since newvirulences have appeared. In-depthstudies on crown depth. root Vigor andhigher grain production are envisioned.Plans are being made to improve <strong>the</strong>bread wheats Pissi. a soft white type.Hy65. Hindi 62 and NI5439. and <strong>the</strong>durums A206. Kathia 25. A9-30-1 andMeghdoot. The exploitation of winterwheats seems promising. and selectionsfrom crosses with local improved typesis in progress.

111Identifying Wheats Adapted to More TropicalAreas of <strong>the</strong> Sou<strong>the</strong>rn Cone of South AmericaM.M. Kohli, Wheat Program, CIMMYT, Santiago, ChlleAbstractThe low productivity and high cost ofproductionfor wheat in <strong>the</strong> more tropicalareas of <strong>the</strong> Sou<strong>the</strong>rn Cone region are <strong>the</strong> result ofa combination ofunpredictable climatic conditions and severe disease pressures. Thecombination of heat. drought. frost and high rainfall, as well as abrupt changesin <strong>the</strong> temperature-humidity relationship. determine <strong>the</strong> type oj wheat plantwhich can adapt to <strong>the</strong>se are~. SPeCtftc germplasm which can resistphysiological disorders caused by high evapotranspiration rates needs to becombined with broad-based resistance to a complex ojdiseases. In addition. <strong>the</strong>wheat varieties will be reqUired to adapt to poor soils with high saturation levelsojsome minerals and low available phosphorus.The rapid expanSion of wheatcultivation into more tropical areas of<strong>the</strong> Sou<strong>the</strong>rn Cone region has come inresponse to two important factors. asteady increase in demand, resulting ina serious drain on <strong>the</strong> nationaleconomies due to imports, and <strong>the</strong>farmers' need for a cover crop to followmaize. soybean and cotton. Thesefactors toge<strong>the</strong>r have been responsiblefor <strong>the</strong> seeding of approximately 1.5million hectares of wheat in tropicalareas of Argentina. Brazil andParaguay. There is, however. atremendous potential for fur<strong>the</strong>rincrease in all three countries,especially Brazil.To date, <strong>the</strong> farmers' experience withwheat has been a series of successesand failures. Low-level productivity and<strong>the</strong> high cost of production have beentwo discouraging elements. In addition.unpredictable climatic conditions andsevere disease epidemics are majorlimiting factors for <strong>the</strong> type of wheatgennplasm which might adapt to <strong>the</strong>area.The number of plant characters thatneed to be combined for more tropicalareas are so numerous and so variedfrom those of traditional wheat-growingregions that <strong>the</strong>y cause serious concernamong plant breeders, regarding suchfactors as availability of sufficientgenetic variability, screening methodsand breeding priorities. Similarly,agronomic or crop management factorsneed critical analysis to reduce <strong>the</strong> costof production, while stabilizingproductiVity at a higher level.In order to identify wheat varietieswhich will adapt to <strong>the</strong>se warmer areas,it is important to understand <strong>the</strong>interplay among various climaticconditions that limit wheat productionand <strong>the</strong>ir influence on plant charactersand diseases.Climatic StressesUnstable climatic conditions are acharacteristic of <strong>the</strong> tropical regions of<strong>the</strong> world. and <strong>the</strong>ir unpredictabilityfrom year to year or within <strong>the</strong> sameyear can be considered a major problemfor stable wheat production. Animportant aspect of climatic stresses isthat of abrupt changes in <strong>the</strong>relationship between temperature andrelative humidity over short periods oftime. For <strong>the</strong> purpose of discussion, <strong>the</strong>nor<strong>the</strong>rn Parana region in Brazil isrepresentative of a majority of <strong>the</strong>tropical areas under wheat in <strong>the</strong>Sou<strong>the</strong>rn-Cone. Even at <strong>the</strong> risk oftaking averages of completely differentyears. Figure 1 shows <strong>the</strong> majorclimatic stresses at Londrina. Parana,

112from 1958 to 1980. These. in tum.determine <strong>the</strong> type of wheat plantwhich can adapt to <strong>the</strong>se areas.BeatHigher temperatures (average + 21°C)throughout <strong>the</strong> crop cycle are probablymore important dUring <strong>the</strong> early andlate stages of <strong>the</strong> crop. The effect ofheat in reducing <strong>the</strong> number of tillersproduced or <strong>the</strong> killing of secondaryReI.hum......0.r::~~..... U> Cl.....0 -~:c ...-::l~ ...~..... ~ p.~ e~p. f-4~e~f-4-8c0-"'=5".... r/)..... ...~:9-~ ~1C-....~- 0. §3228242016124o210-40tillers is a principle reason for poorstands. which are hard to overcomethrough higher seeding densities.Similarly. a sudden rise in temperatureafter flowering results in qUick dryingof <strong>the</strong> plants. causing grain shrivelingand low test weight.DroughtThe rainfall pattern of <strong>the</strong> region is soerratic that it is difficult to predict a80..,...--------------------------.n.. .----- .-____ __-'''''~.__-----9--.3836-t ...-o::.=====:::::-----------==-=:--1----. ._____e-- e~_ Absolute max. temp. - •iAverageilllcq·"". /"•'le ---'.-o-kJ'?P. • • • •i IJ_I0iweragelJ]L - I~~P.'---1-"-----', I_ 1]. te~ I - · ·• • II I I".~e I t I ---- I 1.~~ . -. - .~bSO ~'0'" - .---8 . • __. /' --.te~_ /~----------·---------·------7·.~_~t./.• ._Annual total 2.550 hrs- ...............•.---. .........- -'" ---41--------------....;;;.;:....-~-~~~~~~--200C0 1.....e....u~c......15120---./ /., 14 , 12 I 7 , 7 , 7 I 6 I 8 I 8 I 10 I 11 , 14Figure 1. cnmauc chart of LoDdrlna. Brun. 1958 to 1980Climatic classification: Cfa (hot. humid. subtropic). as per W. KoeppenSource: Seventh DISME. MA. SP: Courtesy A.R. Correa

113standard date for sowing. In spite of <strong>the</strong>useful guidelines provided in Figure 1.a drought can occur at any stage of <strong>the</strong>crop and for an undetermined length oftime. Although <strong>the</strong> date of seeding canbe adjusted to good moistureavailability, <strong>the</strong> poor water-retentioncapacity of <strong>the</strong> soil can provoke earlydrought. <strong>the</strong>reby causing reduced plantdensity and non-uniform stand. Theconstant mid-season drought around<strong>the</strong> heading stage is crucial in <strong>the</strong>reduction of potential yield. Germplasmof high yield potential and tolerance todrought at this stage of <strong>the</strong> crop cyclewould help stabilize yields to someextent.FrostOne of <strong>the</strong> most feared limiting factorsfor wheat production in <strong>the</strong> region isfrost injury. especially at <strong>the</strong> headingstage. Some adjustment in <strong>the</strong> date ofseeding can serve as an escapemechanism. but this leads to o<strong>the</strong>rproblems at <strong>the</strong> beginning and <strong>the</strong> endof <strong>the</strong> crop cycle. In fact. farmerscustomarily spread wheat seeding overa long period of time to escape frost; <strong>the</strong>various seedings suffer from drought,frost. late rains and severe diseaseepidemics. To solve this problem, <strong>the</strong>earlier-mentioned heat and droughttolerance must be combined with lateheading. through <strong>the</strong> addition of asingle gene for vernalization. in order toescape <strong>the</strong> major frost frequency period.Hlgb rainfallIt is paradoxical to discuss <strong>the</strong> problemof high rainfall and drought at <strong>the</strong> sametime. yet it seems a rule in <strong>the</strong> moretropical areas. In normal years. highrainfall is generally a problem for latevarieties or late-seeded crops. causingdifficulties in <strong>the</strong> harvest process. suchas deterioration in grain quality and. insome cases. preharvest sProutinb' Inabnormally wet years. <strong>the</strong> intensity ofvarious diseases is so severe that evenchemical control is not sufficient tomaintain average productivity.Considering <strong>the</strong>se climatic factors. amodel wheat variety should have hightillering ability. tolerance to early heat.tolerance to drought in <strong>the</strong> mid-season.late heading to escape frost and a shortripening period to mature before <strong>the</strong>onset of rains. To <strong>the</strong>se can be addedsemidwarf plant stature to resist strongwinds and small fertile spikes to ripenqUickly. Such a wheat variety will <strong>the</strong>nneed ample resistance to <strong>the</strong> variousdiseases and insect pests prevalent in<strong>the</strong> region.Biological StressesDiseasesBy far <strong>the</strong> most common factor limitingwheat production in more tropical areasof <strong>the</strong> Sou<strong>the</strong>rn Cone region is disease.In a recent analysis done for CIMMYT'sEconomics Program. <strong>the</strong> average lossesin yield due to wheat diseases in <strong>the</strong>Parana. Matto Grosso do SuI and SaoPaulo regions of Brazil were 11 % peryear. What is more important is that<strong>the</strong>se losses occurred in spite of <strong>the</strong> factthat over 90% of <strong>the</strong> farmers usedchemical control. Where <strong>the</strong>re was nochemical protection. <strong>the</strong>se lossesranged between 20 and 60% (Table 1)and. in some cases. as high as 100%.A combination of high temperature andhigh humidity favors a large complex ofdiseases in this region; <strong>the</strong> importanceof spot blotch (Helminthosporiumsativum) is highlighted in <strong>the</strong> datapresented in Table 2. During <strong>the</strong> 1981to 1983 period. spot blotch aloneconstituted between 50 and 90% of <strong>the</strong>yield loss caused by <strong>the</strong> total diseasecomplex in <strong>the</strong> western Parana region.This picture was quite different during<strong>the</strong> mid-1970s. when leaf rust was <strong>the</strong>major disease.O<strong>the</strong>r important diseases in <strong>the</strong>complex are stem rust. scab. bacterialblight. glume blotch and powderymildew. However. in <strong>the</strong> past few years.

114it has been observed that common rootrot and take-all are causingundetermined losses each year in <strong>the</strong>wheat-soybean rotation system.There is sufficient genetic variabilityavailable for resistance to most of <strong>the</strong>sediseases. However, a large proportion of<strong>the</strong> variability, especially for <strong>the</strong> foliarblights and spike diseases, needs to beTable 1. Effect of chemical control on <strong>the</strong> reduction of losses dueto <strong>the</strong> disease complex, Parana, Brazil, 1976 to 1983!1Yield (kg/ha)Ch~k Recommended Loss in(no chemical chemical control yieldYear control) (3 applications)1U (010)1976 1347 2170 381977 1880 2410 221980 834 2054 591982 168 1220 371983 1390 2618 47Average 1244 2094 41!./ Average of 14 experiments conducted by Y.R. Mehta,IAPAR, Brazil'Qj 1st and 2nd application for control of leaf rust, spotblotch and scabTable 2. Reduction in wheat yield due to <strong>the</strong> disease complex of western Parana,Brazil, 1981 to 1983Level of I Yield LossVariety controJ!. (kg/ha) (010) Disease1981Cocoraque Tl 2016 0T2 1883 6.59 Spot blotchT3 1769 12.25 Disease complex1982Anahuac Tl 2226 0T2 1423 36.07 Spot blotchT3 1302 41.51 Disease complex1983Anahuac T1 2935 0T2 2361 19.56 Spot blotchT3 2291 21.67 Disease complex!of T1 = total control of all diseases, T2 = total control of all diseases exceptspot blotch, T3 = no controlSource: M.A. Oliviera, OCEPAR, 1984

115transferred into high-yielding andadapted wheat varieties. This willrequire novel breeding approaches.combined with efficient screeningsystems. in order to produce adaptedvarieties. Until this is done. chemicalcontrol will have to safeguard wheatproduction.Insect pestsThere are very few traditional wheatgrowingareas in <strong>the</strong> world which haveproblems with insect pests. In <strong>the</strong> moretropical environments. however. aphidsand stemborers are important. Thelesser cornstalk borer (Elasmopalpuslignosellus Zeller) can wipe outcomplete fields of wheat. if <strong>the</strong> wea<strong>the</strong>rremains warm and dry after seeding. Inaddition. cereal aphids such asMetopolophium dirhodum. Sitobionavenae. Schizaphis graminum andRhopalosiphum pOOi are widespreadon <strong>the</strong> crop. At <strong>the</strong> present time. verylittle information about genetic'variability for resistance to <strong>the</strong>se insectpests is available in wheat. andchemical control has been an effectivealternative. But as <strong>the</strong> area underwheat in tropical environmentsincreases. it will become necessary toscreen wheat germplasm for insectresistance and breed it into <strong>the</strong> newvarieties.Soil and SoilManagement StressesVast areas in this tropical region havehighly leached. acidic soils with highaluminum saturation and low availablephosphorus. and <strong>the</strong>ir subsequentcorrection to deep levels is of utmostpriority. O<strong>the</strong>r areas. with soil salinity.micronutrient deficiency andmanganese or iron toxicity. also causeserious concern. In <strong>the</strong> presentlypracticed system of two crops per year.many management factors. such as soilcompaction and erosion. have alsobecome very important. Most of <strong>the</strong>sefactors will probably be discussed indetail at this workshop by <strong>the</strong>production agronomists.From <strong>the</strong> standpoint of wheat breeding.plant characters such as deep rootingsystems. resistance to aluminum and/oro<strong>the</strong>r mineral toxicities and efficientphosphorus extraction need to beidentified. Some progress has alreadybeen made in <strong>the</strong> development of highyieldingand well-adapted wheats foracid soils with aluminum toxicity. Thisis <strong>the</strong> result of <strong>the</strong> successful mixing ofBrazilian and Mexican wheat genepools. The next phase in this programwill be to screen for adaptation to lowphosphorous soils. as well as for o<strong>the</strong>rdesirable characters such as betterresistance to <strong>the</strong> tropical diseasecomplex.In those tropical regions whereirrigation facilities are in existence orcan be developed. water managementproblems. irrigation systems and <strong>the</strong>irinteraction with <strong>the</strong> spread of diseasesare important. Irrigated wheat providesa more stable production system. withhigher levels of productivity. than <strong>the</strong>rainfed wheat discussed earlier.ConclusionsIn conclusion. <strong>the</strong> problems inidentifying wheats for more tropicalareas are so numerous and diverse.compared with those for <strong>the</strong> traditionalareas, that <strong>the</strong>y require <strong>the</strong>development of a completely differentplant type for proper adaptation. Newgermplasm. which can withstand <strong>the</strong>physiological stresses caused by <strong>the</strong>high evapotranspiration rate in <strong>the</strong>tropics. will have a greater role to playin increasing present levels ofproductiVity. Some of <strong>the</strong>se characters.not easily located in wheat or availablein alien species. will need to betransferred through wide-crosses. Theproblem of developing wheats for moretropical areas is very complex. andopens up vast fields of research that arestill unexplored. Finally. researchconducted on phosphorus liberation bymycorrhiza or nitrogen fixation intropical grasses may be applied toincrease wheat production.

116Wheat Breeding in Rio Grande do SuI, Brazilo. de Sousa Rosa, Centro Nacional de Pesquisa de Trigo, Pas80Fundo, Rio Grande do Sui, BrazilAbstractRio Grande do Sul is <strong>the</strong> sou<strong>the</strong>rnmost state in Brazil, bordering on Uruguayand Argentina. Its soils are acid, deficient in phosphorus and have high levels ofexchangeable aluminum and manganese. The aluminum and manganese levelsof <strong>the</strong> oxisols in <strong>the</strong> most important wheat-growing region of <strong>the</strong> state aresufficient to cause great reduction in plant growth or even death in cultivarswhich are susceptible to crestamento (toxicity caused by aluminum and/ormanganese, etc). Wheat breeding has been carried outfor tolerance tocrestamento. All wheat cultivars recommended tofarmers in Rio Grande do Sulare tolerant to crestamento, <strong>the</strong> most tolerant being BR6, CNTl and IAC-5(Maringa). The breeding program underway in <strong>the</strong> state maintains suchtolerance through plant selection under <strong>the</strong>se soil conditions. These soils arealso characterized by unavailable applied phosphorus. By working withcultivars tolerant to crestamento, it was possible to identify <strong>the</strong> Braziliancultivars Toropi and PG1 as haVing a greater development capacity in soils withlow phosphorus availability. Attempts are now being made to transfer thisincreased phosphorus-use efficiency to o<strong>the</strong>r cultivars with better yieldingcapacity.Rio Grande do SuI is <strong>the</strong> southmoststate of Brazil, bordering on Uruguayand Argentina. It is located between 27and 33°S latitude and 50 and 57°Wlongitudes, and covers an area of282,184 square kilometers.Spring wheat is grown in <strong>the</strong> state.sown at <strong>the</strong> end of fall and beginning ofwinter (May to July); it is harvestedfrom OCtober to December. Rains arewell distributed throughout <strong>the</strong> year,occurring in sufficient amounts to meetcrop requirements. although in someyears <strong>the</strong>re may be an excess. Betteryields are usually obtained in <strong>the</strong> regionin years with less rainfall, especiallydUring heading and ripening of wheat.The wheat-producing areas in <strong>the</strong> stateare located in altitudes ranging between50 and 1200 meters. The largestnumber of hectares sown to wheat inRio Grande do SuI occurred in 1979with 2.184.899 hectares; statewideaverage yields have varied between309 kglha (1972) and 1,224 kglha(1981).The soils in Rio Grande do SuI are acid.deficient in phosphorus. show highlevels of exchangeable aluminum andmanganese. and have varying values ofo<strong>the</strong>r elements in <strong>the</strong> different types ofsoil in <strong>the</strong> main wheat-producingregion. Some soil characteristics. atseven locations in <strong>the</strong> state, are shownin Table 1. In that sampling. <strong>the</strong>content of exchangeable aluminumranged between 0.6 and 3.0 meq/l00 gof soil, while exchangeable manganesevaried between 32.4 and 546.8 ppm.To better explain <strong>the</strong> wheat breedingproblems in <strong>the</strong> state, certain ecologicalinfonnation is given for Passo Fundo,<strong>the</strong> site of <strong>the</strong> National Wheat ResearchCenter of EMBRAPA (Table 2). Thisarea is representative of <strong>the</strong> majorwheat-producing areas of Rio Grande doSuI, as well as of Santa Catarina andsouth central Parana. It is located at28°15'S latitude, 52°24'W longitudeand at an altitude of 684 meters. Frostoccurs every year. being more frequentin June, July and August; sometimes itoccurs in September, and can result insevere injury to <strong>the</strong> crop.

117Table 1. Chemical properties of soils from seven locations in <strong>the</strong> main wheat-growing regionof Rio Grande do Sui. Brazil (sampling depth 0-12 em)Exchangeable Exchangeable Exchangeable Availablealuminum manganese Ca+Mg phosphorusLocation Soil mapping unit pH (meI100g) (ppm) (me/100 g) (ppm)Passo Fundo Passo Fundo 4.6 3.0 78.3 4.3 14.1Julio de Castilhos Passo Fundo 4.9 1.6 93.2 3.4 9.7Cruz Alta P. Fundo-5to. Angelo 5.0 0.7 117.4 9.5 9.1(I ntergrade)Coxilha P. Fundo-Estacao 4.6 1.5 303.8 9.9 2.5(I ntergrade)Lagoa Vermelha Erexim 4.7 2.7 32.4 2.5 1.5Vacaria Vacaria 4.5 1.9 546.8 3.0 1.8Chiapeta Santo Angelo 4.8 0.6 105.3 5.8 1.0Source: Siqueira, O.J.F. de. 1980. Response of soybeans and wheat to limestone application on acid soilsin Rio Grande do Sui, Brazil. PhD Thesis. Iowa State University, Ames, Iowa, USA.Table 2. Climatic parameters for <strong>the</strong> wheat-growing season. PassoFundo. Rio Grande do Sui. Brazil. 1959 to 1979Average RelativeRainfall temperature humidity Hours ofMonth (mm) (OC) (010) sunlightMay 100 14.6 74 183June 138 12.9 77 158July 134 12.8 74 171August 173 13.8 72 169September 197 15.7 72 153October 183 17.4 71 201November 119 19.3 66 230December 164 21.2 66 257Source: Agrometeorological Bulletin 1983. 1984. Centro Nacional dePesquisa de Trigo, Passo Fundo, Brazil. Pp. 2-31.

118The soil in <strong>the</strong> Passo Fundo region isclassified as dark red dystrophic latosol(oxisol). Data relating to somecharacteristics of a soil profile which isbeing used in a trial on lime dosage aregiven in Table 3. As can be seen. <strong>the</strong>pH is very low. and is slightly increasedby lime applications. Aluminum and/ormanganese levels are sufficiently highto cause ei<strong>the</strong>r <strong>the</strong> death or greatreduction in plant growth in cultivarswhich are susceptible to crestamento(toxicity caused by aluminum and/ormanganese). Before creating cultivarsresistant to this physiological disease.<strong>the</strong> area was considered inadequate foragriculture. Lime applicationsneutralize acidity. as well as aluminumand manganese. in <strong>the</strong> top layers. but<strong>the</strong> problem remains in <strong>the</strong> deeperlayers. below 20 cm (Table 3). Cultivarssusceptible to crestamento. whengrown in <strong>the</strong>se soils amended withlime. no longer show very evidentcrestamento symptoms. but are usuallyunable to compete in yield withresistant cultivars.The genetic breeding of wheat in RioGrande do SuI was initiated in 1914.The present breeding objectives are <strong>the</strong>development of germplasm with:• Agronomic characteristics for highyield potential• Short straw and/or high resistance tolodging• Tolerance to crestamento• Resistance to leaf rust (Pucciniarecondtta trttici)• Resistance to stem rust (Pucciniagraminis triticO• Resistance to septoria leaf blotch(Septoria tritici)• Tolerance to glume blotch (Septorianodorum)• Tolerance to helminthosporium(Cochliobolus sattvus)• Resistance to mildew (Erystphegraminis trtttct)• Resistance to scab (Gibberella zeae)• Resistance to wheat mosaic virus• Tolerance to barley yellow dwarfvirus• Resistance to sprouting• Resistance to loose smut (Ustilagotrittci)Table 3. Soil acidity and location in <strong>the</strong> soil profile of aluminum, calcium and magnesium,11 years after <strong>the</strong> application of lime, Passo Fundo, Rio Grande do Sui, Brazil, 1984Amount of lime applieda 12.4 tlha!J 24.8 tlhat:1JSoil depth pH AI Ca+ Me pH AI Ca+ Me pH AI Ca+ Me(em) (me/lOa e) (me/100 e) (me/100 e;0- 1.25 4.5 2.5 3.5 4.8 1.0 6.4 5.2 0.4 7.71.25 - 2.5 4.3 3.2 2.9 4.7 1.4 5.6 5.2 0.6 7.02.50· 5.0 4.2 3.6 2.6 5.0 1.2 7.0 5.0 0.8 6.95.00 - 10.0 4.3 3.6 2.4 4.7 1.6 5.6 5.3 0.5 8.110.00·20.0 4.3 3.9 2.3 4.6 2.2 4.4 5.0 1.1 6.320.00 - 30.0 4.4 4.2 1.9 4.4 3.3 2.9 4.9 2.7 3.630.00 - 40.0 4.4 4.0 2.2 4.5 3.2 2.8 4.6 3.0 3.4!l The amount required to raise soil pH to 6.0 when experiment began in 1973~/ Double <strong>the</strong> amount of !.ISource: Soils group, CNPT, EMBRAPA, Brazil

119• Resistance to shattering• Variability as to cycle, preferablyearly maturity• Tolerance to frost at <strong>the</strong> reproductionstage• Efficiency in phosphorus use• Resistance to greenbug (Schizaphisgramtnum R.)• Good industrial qualityThe information provided in this paperrefers only to breeding in relation to soilproblems.Breeding WheatsApproprIate for <strong>the</strong> ProblemSoils of Rio Grande do SuiTolerance to crestamentoTolerance to crestamento was firstidentified in 1914, among wheatsintroduced by immigrants to Brazil (7).In that year. <strong>the</strong> cultivar Pollisu wasselected for its exceptional growth inacid soils. This cultivar is part of <strong>the</strong>genetic background of nearly allvarieties recommended for Rio Grandedo SuI.In 1948. Araujo (2) determined thatcrestamento was caused by <strong>the</strong>occurrence of exchangeable aluminumand iron in <strong>the</strong> soil, as part of its totalabsorption capacity; this constituteswhat is called noxious acidity. In 1949,crestamento symptoms werereproduced by Oliveira after steriliZing<strong>the</strong> soil by heat, thus eliminating <strong>the</strong>presence of biological agents as possiblecauses of <strong>the</strong> disease.responsible for tolerance, a dominantcharacteristic. Nodari (6), in geneticstudies contrasting <strong>the</strong> tolerance ofseveral cultivars to crestamento underfield conditions, concluded thattolerance is controlled by two dominantgenes.Tolerance to crestamento involvesseveral factors, including tolerance totoxic aluminum and to manganese.When interactions among <strong>the</strong>se factorsoccur, <strong>the</strong> interpretation of resultsobtained in <strong>the</strong> field is difficult. The useof nutrient solutions has permitted <strong>the</strong>separation of cultivar reactions to eachof <strong>the</strong>se toxic factors. Using thismethodology, Lagos et al. (5)determined that <strong>the</strong> tolerance gene toaluminum in <strong>the</strong> cUltivar BH 1146 islocated'in chromosome 40.All wheat cultivars recommended inRio Grande do SuI are tolerant tocrestamento. Among <strong>the</strong>m, BR6, CNT1and IAC5 (Maringa) show <strong>the</strong> bestresistance (8). The wheat-breedingprogram maintains such tolerancethrough plant selection in segregatinggenerations (normally F2 or F3) in soilareas where lime has never beenapplied. In this way, tolerant plants areeasily identified and, in subsequentgenerations, <strong>the</strong>y are screened in soilshaVing better fertility. At <strong>the</strong> end of <strong>the</strong>selection process, tolerance tocrestamento is confirmed by againgrOWing <strong>the</strong> lines in soils withcrestamento.The first information availableconcerning <strong>the</strong> genetics of <strong>the</strong>transmission of tolerance tocrestamento is attributed to Beckman(1954), who indicated a gene as

120Efficiency in phosphorus useThe soils in <strong>the</strong> main wheat-producingregion of Rio Grande do Sul arecharacterized by a low level ofphosphorus aVailability. The interactionof plant response and aluminum andphosphorus absorption is well known.Ben and Rosa (3), working withcultivars tolerant to crestamento.identified <strong>the</strong> cultivars Toropi and PG1(a selection of Polissu) as haVing betterdevelopment in soils with lowphosphorus aVailability. These cultivarshave a better (more efficient) utilizationof phosphorus (natural or applied),indicating <strong>the</strong> possibility ofencountering genetic variability for thischaracter.Koehler (4), working at WashingtonState University, USA, carried outexperiments involVing 1600 springwheat accessions, with <strong>the</strong> objective ofidentifying accessions tolerant tophosphorus stress and learned how toselect for this characteristic. His resultsidentified various cultivars with goodadaptation to soils with low phosphoruslevels.Attempts are being made at <strong>the</strong>National Wheat Research Center totransfer such phosphorus-use efficiencyto o<strong>the</strong>r cultivars with better yieldpotential. The segregating generationsare grown in soils with low phosphorusavailability (around 3 ppm) and withtoxic aluminum. It is expected that, by1985, lines with better phosphorusutilization will be available for finalevaluation.ConclusioDSEcological conditions in Rio Grande doSul vary greatly, as compared to thoseof <strong>the</strong> wheat-producing regions ofArgentina or Mexico. Never<strong>the</strong>less,using <strong>the</strong> technology available atpresent, good farmers in <strong>the</strong> regionhave obtained average yields of 2.068kglha over <strong>the</strong> last five crop years. Theyutilize a production system involVing<strong>the</strong> use of <strong>the</strong> best cultivars. croprotations to control root diseases andfungicide application to complementgenetic resistance.New cultivars developed jointly byEMBRAPA and CIMMYT will be madeavailable to farmers in Rio Grande doSuI in 1985 (new lines of <strong>the</strong> crossIAS631Alondra''S"IIGabotol LagoaVermelha (PF79765, PF79767.PF79780 and PF79782)). It is expectedthat. with this material, <strong>the</strong>se samefarmers will be able to raise <strong>the</strong>ir yieldsto 3 t/ha within <strong>the</strong> next five years.

121References1. Araujo. J.E.G. 1949. 0 aluminiotrocavel. possivel cause docrestamento do trigo. In ReuniaoBrasileira de Ciencia do Solo. 2.Campinas. Brazil. Pp. 329-337.2. Araujo. J.E.G. 1948. A reacao dosolo sua possivel influencia no"Crestamento" do trigo. Agros(Pelotas) 1(2):81-94.3. Ben. J.R.. and 0.5. Rosa. 1983.Comportamento de algumascultivares de trigo em relacao afosforo no solo. PesquisaAgropecuaria Brasiliera (Brasilia)18(9):967-972.4. Koehler. T.J. 1983. Identifyingefficient spring wheat accessions oflow levels of phosphorus on acidsoils.6. Nodari. R.O. 1980. Bases geneticasda heranca do carater tolerancia aocrestamen to em genotipos de trigo(Triticum aestivum L.) M.Sc.Thesis. UFRGS. Porto Alegre.Brazil.7. Osorio. E.A. Variedades emelhoramento. 1982. Trigo noBrasil. In Fundacao Cargill. vol. 1.Campinas. Brazil. Pp. 146-197.8. Souza. C.N.A.. J.C.S. Moreira andL.J. del Duca. 1982. Reacao aocrestamento de cultivares de trigorecomendadas para cultivo noBrasil. In XIII Reuniao Nacional dePesquisa de Trigo. Resumos eComunicados Tecnicos. OCEPAR,Cascavel. PRo Brazil. Pp. 204-207.5. Lagos. M.B.• MJ.B. MoraesFernandes. F.I.F. de Carvalho andC.E. de O. Camargo. 1983.Localizacao de gene(s) de toleranciaao aluminio trocavel (AI + + +) emtrigo cv. BH1146 (Triticumaestivum). Paper presented in <strong>the</strong>XIII Reuniao Nacional de Pesquisade Trigo. Cruz Alta. Rio Grande doSuI. Brazil.

122Breeding and Disease ProblemsConfronting <strong>the</strong> Successful Cultivationof Wheat in <strong>the</strong> Cerrados of BrazilA.R. da SUva, lUnlaterio de Agricultura, Provaraeas Nacional,BrasWa, D.F., BrazUAbetractThere are three systems ofwheat production in <strong>the</strong> Cerrados. rainfed. irrigatedupland and irrigated lowland. Important breeding points and <strong>the</strong> main diseasesare discussedfor each of<strong>the</strong> systems in <strong>the</strong> Cerrados area ofBrazil. as well asinformation on climate and soils in relation to each of <strong>the</strong>m. Wheat yields onfarmers' fields and a comparison with o<strong>the</strong>r poSSible crops are presented.Climate andSOU. of <strong>the</strong> CerradosBrasilia will be considered here asrepresentative of <strong>the</strong> <strong>the</strong> Cerradosregion of central Brazil. It has twoseasons. a rainy season and a dry one.The rainy season lasts from October toApril. and <strong>the</strong> dry season from May toSeptember. During <strong>the</strong> rainy season.<strong>the</strong> average monthly rainfall is 215mm; dUring <strong>the</strong> dry season it is only 14mm. From January to April. <strong>the</strong> totalrainfall is 780 mm. During <strong>the</strong> rainyseason. dry periods (veranicos) arefrequent and can influence <strong>the</strong> wheatcrop in two ways. by reducing plantgrowth and by favoring a serious pest.Elasmopalpus lignosellus Zeller.The temperature in Brasilia Isrepresentative of that of <strong>the</strong> highplateau (1.000 meters); it is lower thanthat of <strong>the</strong> low-altitude Cerradosregions. The average temperature in<strong>the</strong> rainy season is 21.3°C and. in <strong>the</strong>dry season. 19.3°C; if <strong>the</strong> temperatureofSeptember (wheat harvest month) isnot considered. <strong>the</strong> dry season averagedrops to 18.6°C. The relative moistureof <strong>the</strong> air is high during <strong>the</strong> rainyseason and low in <strong>the</strong> dry season. Dewis frequent until 9:00 or 10:00 a.m. inMay and June; <strong>the</strong>re is little dew inJuly. August and September.The Cerrados soils are acid. with highsoluble aluminum content. They arevery low in calcium and magnesium aswell as in phosphorus; <strong>the</strong>re is a strongfixation when phosphorus is applied asfertilizer. There is also a deficiency inmicronutrtents. mainly zinc and boron.Boron application at a rate of 1 kglha isneeded to prevent male ster1l1ty. alimiting factor in wheat production thatis also conditioned by climate. Thephysical properties of <strong>the</strong> soils are goodfor root development of <strong>the</strong> plants. but<strong>the</strong>ir water retention is poor. Soils in<strong>the</strong> paddy fields in <strong>the</strong> lowlands vary agreat deal but. in general. have poordrainage which leads to waterlogging;<strong>the</strong>y are more appropriate for riceproduction and flood 1rr1gation than<strong>the</strong>y are for wheat cultivation.Systems of Wheat ProductionThere are three systems of wheatproduction used by farmers in <strong>the</strong>Cerrados region. as a ratnfed crop.sown in <strong>the</strong> middle of <strong>the</strong> rainy season(February) and harvested in <strong>the</strong> dryseason (With total rainfall of 700 mmdUring <strong>the</strong> crop season). as an irrigatedcrop in <strong>the</strong> uplands and as an 1rr1gatedcrop in <strong>the</strong> paddy fields. In <strong>the</strong> last twosystems. <strong>the</strong> crop season is <strong>the</strong> dryseason. May to September. with 273

123hours of sunlight monthly. Although<strong>the</strong>re are breeding and diseaseproblems common to <strong>the</strong> three systemsof production, <strong>the</strong>re are o<strong>the</strong>rs that aredifferent enough to justify specificapproaches for resolution. according to<strong>the</strong> production system.Breeding and DiseasesRalnfed cultivationImportant factors to consider inbreeding wheat for cultivation underrainfed conditions are:• Good growth patterns and <strong>the</strong> abilityto tiller under warmer conditions• Growth cycle of about 100 days• Tolerance to aluminum toxicity. asroots must reach into <strong>the</strong> subsoil forwater, especially in dry periods• Resistance to drought• Resistance to diseasesThe efficient use of phosphorus and <strong>the</strong>C4 type of photosyn<strong>the</strong>sis are desirablecharacteristics for all of <strong>the</strong> systems ofproduction.Disease incidence is related to rainfall.Abundant rainfall leads to highincidence. especially when it takesplace toward <strong>the</strong> end of <strong>the</strong> cropseason. The main diseases are stem andleaf rusts and Helmtnthosporiumsattvum. which is <strong>the</strong> most importantdisease and is responsible for <strong>the</strong>heaviest losses. All of <strong>the</strong>se diseasesmay be controlled through <strong>the</strong> use offungicides.Until now, <strong>the</strong> best germplasm hasbeen <strong>the</strong> old Brazilian varieties, whichare tall and have tolerance to aluminumtOXicity. In <strong>the</strong> best locations dUring <strong>the</strong>last seven years. <strong>the</strong>y have yielded from900 to 1,700 kglha on farmers' fields;no crop failures have been reported.Wheat has been profitable in <strong>the</strong>locations where early soybeans yieldwell. The two-crop rotation of earlysoybeans followed by wheat. grown in<strong>the</strong> same field dUring <strong>the</strong> rainy season.has given a higher return than landsown only to soybeans or only to maize.In areas where early soybeans do notyield well. wheat alone cannot completewith late soybeans (2.5 t/ha) or maize(4 Uha). since <strong>the</strong>se are crops whichutilize <strong>the</strong> entire rainy season.Irrigated cultivation on <strong>the</strong> uplandsThe lower temperatures. relativehumidity. and rainfall and <strong>the</strong> sufficientsunshine of <strong>the</strong> uplands are favorable tohigher wheat yields and lowerincidence of diseases. Wheat is irrigatedby sprinkler and by corrugation. Anadequate supply of moisture. combinedwith liming of <strong>the</strong> soil, permits <strong>the</strong>successful groWing of <strong>the</strong> MeXican-typecultivars. with yields ranging from 2 to3.5 Uba.The main disease problems are stemand leaf rusts and powdery mildew. Itis possible that root rots and nematodesmay become a problem after severalyears of cropping on <strong>the</strong> same site.Helminthosporium is not an importantdisease.The use of cultivars which give betteryields in warm climates would improvecrop adaptation for <strong>the</strong> lower altitudesand result in higher yields. Highertillering capacity. short. strong stemsand resistance to lodging are importantfeatures of cultivars for use withirrigation. Efficient utilization ofphosphorus is also important. andtolerance to aluminum toxicity wouldimprove yield. making irrigation moreefficient.The wheat-grOWing season in <strong>the</strong>uplands is limited to <strong>the</strong> period from<strong>the</strong> middle of April to September, inorder to avoid <strong>the</strong> rains occurring at <strong>the</strong>end of <strong>the</strong> crop cycle. This proVidesconditions leading to grain of highquality. high test weight and goodmilling quality.

124Outing <strong>the</strong> dry season, it is possible tocultivate o<strong>the</strong>r crops, such as beans,soybeans, maize, potato and peas. Atpresent, farmers are using <strong>the</strong> dryseason for growing wheat, potato, beansand peas. The main problems are <strong>the</strong>high cost of sprinkler irrigation, due tohigh energy prices, and <strong>the</strong> farmers'lack of experience with irrigation andwheat cultivation. Increased corrugatedirrigation would lower costs.Cultivation in <strong>the</strong>lowland. and in paddy field.The lowlands and paddy fields in <strong>the</strong>lower altitudes have warmer climates.Wheat has been cultivated successfullyin areas with an altitude of 500 metersand above. These areas have problemsof irrigation and drainage, because of<strong>the</strong> nature of <strong>the</strong> soil (low hydraulicconductiVity) and <strong>the</strong> poor leveling of<strong>the</strong> fields. Waterlogging frequentlyoccurs and seedbed preparation isdifficult. In addition to <strong>the</strong>characteristics mentioned preViously forbreeding wheat in <strong>the</strong> irrigateduplands, tol~ranceto waterlogging andto higher temperatures will be reqUiredin <strong>the</strong> lowlands. Disease problems aresimilar to those of upland irrigatedwheat, but are more intense.Wheat cropping is carried out in <strong>the</strong>lowlands when <strong>the</strong>re is no risk offlooding, and when o<strong>the</strong>r agriculturalactivities permit. The crops competingwith wheat are <strong>the</strong> same as those of <strong>the</strong>uplands.The water needed by wheat is less thanhalf of that reqUired by flooded rice;thus, wheat is a good alternative when<strong>the</strong>re is limited water in <strong>the</strong> riversdUring <strong>the</strong> dry season. Farmers areobtaining yields in <strong>the</strong>se areas of 2 to3 tlha, with no investment needed o<strong>the</strong>rthan that for drainage improvement.

125Screening Wheats for QualityA. Amaya, Industrial Quality Laboratory, Wheat Program,CIMMYT, MezlcoAbstractScreening tests are simple methods that are used to eliminate undesirablematerialsfrom <strong>the</strong> breeding program; <strong>the</strong>y can be made rapidly, using smallsamples of individual plants in early generations. In <strong>the</strong> case ofquality, <strong>the</strong>sepreliminary screening tests help breeders to select materials with <strong>the</strong> type ofgluten that is deSirablefor <strong>the</strong> preparation ofvarious products. Seed-typeselection is used in segregating materialfor eliminating all lines with poorkernel characteristics. After seed selection, o<strong>the</strong>r preliminary screening tests areperformed, among <strong>the</strong>m, <strong>the</strong> Pelshenke test which is used to separate breadwheats according to gluten strength. The microsedimentation or Zeleny test and<strong>the</strong> sodium dodecyl sulfate (SDS)/lactic acid sedimentation tests are o<strong>the</strong>r rapidmethodsfor estimating gluten strength in bread and durum wheats.Good milling and baking characteristicscan be selected for in <strong>the</strong> developmentof higher-yielding varieties. InCIMMYT's wheat program,improvements are being made indeveloping higher-yielding, broadlyadapted varieties with improved diseaseresistance and improved milling andbaking quality. Everyone working inwheat research, production, utilizationand industrialization should beconcerned with <strong>the</strong> quality reqUired for<strong>the</strong> preparation of local products; itmust be kept in mind that quality is arelative concept, depending on who isconsidering it.For <strong>the</strong> grower, good quality meanshigh yield potential; for <strong>the</strong> mlller,quality means high flour yields, whichpartly depends on high test weight anduniform kernel size and shape. For <strong>the</strong>consumer, wheat quality means a goodend-product. Therefore, for <strong>the</strong>preparation of sandwich bread. wheatwith strong, balanced gluten is needed;for cookies. <strong>the</strong> best quality wheat hasextensible weak gluten. White wheatswith strong or medium-strong glutenare preferred by <strong>the</strong> whole wheatconsuming countries. such as India andPakistan. for <strong>the</strong> preparation ofchapatis.To have all <strong>the</strong>se qualities available. <strong>the</strong>use of preliminary screening tests isvery important. Screening tests shouldbe simple. reprodUcible tests that canbe made rapidly. and in large numbers.on grain samples from individualplants. in order to eliminate undesirablematerials from <strong>the</strong> breeding program;<strong>the</strong>y are not tests which would be usedfor choosing lines to be released as newcommercial varieties. These tests have<strong>the</strong> advantage that <strong>the</strong>y can be carriedout beginning with <strong>the</strong> F3 generation.allOWing many inferior lines to beeliminated early in <strong>the</strong> program. Ingeneral, at CIMMYT. all screening testsare performed after segregatingmaterials have been selected for seedtype.Selection forDesirable Grain TypesEmphasis is given to grain classificationin all wheat breeding programs atCIMMYT; all lines that have poor kernelcharacteristics, and thus are likely toresult in low grain test weight. areeliminated. In grain tests. samples areevaluated for grain size. plumpness.texture and color.

126After seed selection. some of <strong>the</strong>preliminary screening tests areperformed on segregating materials in<strong>the</strong> breeding programs. In <strong>the</strong> case ofbread wheats. <strong>the</strong> segregating materialsare evaluated for gluten strength. ThePelshenke test. which separates wheatswith weak gluten from wheats withstrong gluten. gives an indication of <strong>the</strong>ability of <strong>the</strong> gluten to retain carbondioxide gas which is formed duringfermentation.In this test. a 3-gram sample of grainfrom each plant is ground into wholemeal. mixed with a standard yeastsuspension and formed into a doughball. The ball is immediately placed in abeaker of distilled water at 30°C. and<strong>the</strong> time in minutes until <strong>the</strong> doughball disintegrates is a measure of glutenstrength; this is called <strong>the</strong> Pelshenkevalue. Wheats with strong gluten havePelshenke values of more than 100. minutes; ones with weak gluten havePelshenke values of less than 60minutes. Even though this test hassome weaknesses, it is very useful insome breeding programs.Microsedimentation or <strong>the</strong> Zeleny test isano<strong>the</strong>r method for estimating <strong>the</strong>strength of wheat gluten. Like <strong>the</strong>Pelshenke test. it takes only 3 grams ofwheat from each plant to produce <strong>the</strong>.64 grams of flour needed to perform<strong>the</strong> test. The flour is suspended inwater in a graduated cylinder andtreated with lactic acid. The volume ofsediment. consisting principally ofswollen gluten and occluded starch.which is measured after standing forfive minutes, is <strong>the</strong> sedimentationvalue.The sodium dodecyl sulphate (SDS)tactic acid sedimentation test is ano<strong>the</strong>rrapid method for estimating glutenstrength in both bread and durumwheats. The test is simple and rapid.allOWing for <strong>the</strong> evaluation of severalhundred samples in one day; it alsorequires only 3 grams of wheat. Theground sample is mixed with <strong>the</strong> SDSlacticacid solution in a graduatedcylinder for a short period of time and.after a rest period of ten minutes. <strong>the</strong>volume of <strong>the</strong> sediment is recorded. asin <strong>the</strong> Zeleny test. Wheats with stronggluten have large sedimentation values•while those with weak gluten havesmall values.There are o<strong>the</strong>r tests that can be usedfor <strong>the</strong> screening of segregatingmaterials. but <strong>the</strong> ones mentioned herehave been very important at CIMMYTfor creating <strong>the</strong> quality Variabilityrequired for <strong>the</strong> various countrieswhere genetic materials from <strong>the</strong>CIMMYT wheat program are utilized.

127Wide Crosses and New Genesfor Wheats for <strong>the</strong> TropicsA. Mujeeb-Kazi, Wheat Wide Cross Program, CIMMYT, MezicoAbstractThe benefits breeders have derivedfrom alien species through <strong>the</strong> introgressionofalien genetic material are best exemplified by <strong>the</strong> current CIMMYT IB/IRwheat lines. Several lines have been released by various countries as varietiesbecause of <strong>the</strong>ir wide adaptation, yield stability, aluminum tolerance andresistance to Septoria tritici. O<strong>the</strong>r institutions have made significantimprovements in wheat through alien introgressions, specificallyfor resistanceto <strong>the</strong> pathogens that caUse stem rust. leaf rust, stripe rust, powdery mildewand wheat streak mosaic virus, as well as resistance to greenbug. There havebeen, however, only a limited number ofalien species involved in <strong>the</strong> abovementionedstudies, Aegilops umbellulat.a. Agropyron elongatum, Agropyronintennedium and Secale cereale; considering <strong>the</strong> extent ofalien germplasmavailable, <strong>the</strong> promise offuture success is extremely high. The larger <strong>the</strong>number ofalien genera that are combined with wheat and <strong>the</strong> larger <strong>the</strong>number of resulting hybrids that are advanced, <strong>the</strong> more diversified will be <strong>the</strong>environmental conditions under which wheat production can occur. Thispotential is <strong>the</strong> reasonfor CIMMYT's wide cross program.Conventional plant breeding hasmaintained its predominant role in cropimprovement and has been remarkablyinfluenced by <strong>the</strong> wealth of prevalentgenetic infonnation. This has provided<strong>the</strong> necessary genetic variability for useby plant breeders. and genetic advanceshave adequately demonstrated <strong>the</strong>irconsistent impact. Prevalent breedingprocedures and genetic variability haveso far pennitted routine handling foreach problematic situation that hassurfaced.Complementing research thatcontributed to <strong>the</strong> success ofconventional programs was developedwith great success in <strong>the</strong> 19th centuryin <strong>the</strong> disciplines of mutation breedingand interspecific and intergenerichybridization. The latter two. inessence. have incorporated anundirected. modified genetic system orhave exploited. to a limited extent. <strong>the</strong>unique gene pool of a few closelyrelated or more distant relatives ofcultivated crops. In both cases. newgenes have been identified thato<strong>the</strong>rwise might never have beenavailable through conventional geneticsystems.More recently. <strong>the</strong> exciting areas oftissue culture, multiple shoot fonnationtechnology. an<strong>the</strong>r culture, somaclonalvariation and <strong>the</strong> broadly designatedarea of DNA technology have emerged.It should be recognized. however. that<strong>the</strong>se new methodologies are fanciful;<strong>the</strong>y offer immense promise in <strong>the</strong>orybut. for <strong>the</strong> budgetors of time. <strong>the</strong>y canbe classified as being of high risk andextremely futuristic. They do, however,definitely warrant continued research.In <strong>the</strong> CIMMYT wheat program,agricultural demands have dictated aworking methodology that has taken usfrom a stage of research fantasy to oneof practicality and accountability. Themajority of <strong>the</strong> disease resistance andstress tolerance objectives pursued haveno demonstrable genetic association or

128inheritance and, for a few, no geneticbase of resistance has as yet beenidentified. Specific examples of this are<strong>the</strong> lack of potent kamal buntresistance in Triticum aestivum and T.turgidum, <strong>the</strong> meager knowledge of salttolerance genets and <strong>the</strong> lack of acopper efficiency gene in T. aestivum.To <strong>the</strong>se may be added heat toleranceand drought tolerance; <strong>the</strong> list canundoubtedly be extended. In order toresolve this complex situation, researchefforts need to be so directed.In wheat wide crosses, <strong>the</strong>re is anattempt to resolve some of <strong>the</strong> diseaseresistanceand stress-toleranceproblems. The approach has been toincorporate into wheat (T. aestivumand T. turgidum) <strong>the</strong> genetic resistanceof stress tolerance that abounds in <strong>the</strong>annual or perennial grass species of <strong>the</strong>alien genera Aegtlops, Agropyron,Elymus, Haynaldia, Hordeum andSecale. The major problems limitingalien germplasm utilization lie in <strong>the</strong>difficulty in producing hybrids. Thesedifficulties will always be present andare found at various stages in <strong>the</strong>ontogeny of <strong>the</strong> hybrid. These areashave attracted little attention, andadvances in any or all of <strong>the</strong>m have <strong>the</strong>potential of substantially increasing <strong>the</strong>range of wide hybrids that may beproduced.The phenotype of wide hybrids and<strong>the</strong>ir derived amphiploids mitigateagainst <strong>the</strong>ir commercial use;consequently, additional cytogeneticmanipulations must be made beforepractical application becomes possible.In general, <strong>the</strong>se manipulations aredirected toward introdUcing <strong>the</strong>smallest piece of genetic materialcapable of controlling <strong>the</strong> desiredphenotype without affecting <strong>the</strong> o<strong>the</strong>ressential attributes of <strong>the</strong> recipientspecies. An extensive list of hybridsinvolVing species of <strong>the</strong> Triticeae, andalso many examples of desirable genestransferred from wheat relatives intoTriticum, most of which are now incommercial varieties, has recently beenpublished. Consequently, <strong>the</strong>re can belittle doubt as to <strong>the</strong> practicality of <strong>the</strong>introduction and usefulness of alienvariation.Since <strong>the</strong> introduction of <strong>the</strong> Lr9 locusfrom Triticum, most of <strong>the</strong> examples of<strong>the</strong> introduction of alien variationinvolve loci for disease reaction. Theintroduction of genes affecting proteincontent, from T. dicoccoides into T.aestivum, was recently described.There is a qualitative differencebetween <strong>the</strong> interactions of <strong>the</strong> twotypes of introduced genetic materialthat is of considerable significance. Inall cases involVing disease reactions,both <strong>the</strong> introduced genetic materialand <strong>the</strong> genetic material of <strong>the</strong>pathogen are free to mutate;consequently, <strong>the</strong> durability ofusefulness of <strong>the</strong> alien material islimited by <strong>the</strong> natural variation of <strong>the</strong>pathogen. This type of system can bedescribed as dynamic. In a dynamicsystem, it is to be expected that <strong>the</strong>introduced variation would have adurability no greater than <strong>the</strong> genesavailable by intraspecific manipulation.In this respect. <strong>the</strong>y are no differentthan o<strong>the</strong>r genes manipulated byconventional plant-breedingmethodology. However, in <strong>the</strong> case ofkamal bunt resistance, it would seemthat <strong>the</strong>re is no available source ofresistance in <strong>the</strong> cultivated forms and,<strong>the</strong>refore, <strong>the</strong> loci located in <strong>the</strong> wildrelatives have an increased desirability,even though <strong>the</strong>ir ultimate practicalitywill be limited by <strong>the</strong> constraints of adynamic system (1).

129The introduction of alien geneticmaterial affecting physiological traits of<strong>the</strong> recipient species is free from thisrestriction; this is a static system.Consequently, manipulationsintroducing material of this type have<strong>the</strong> potential of producingbreakthroughs in commercialproduction. It would be anticipated, forexample, that, ifit is possible tointroduce genetic material providingdrought resistance or tolerance, highprotein content, protein quality, salttolerance or various metal tolerances, itwould allow <strong>the</strong> cultivation of wheat inareas where it is currently impossible.As <strong>the</strong> demands for increased worldfood production increase, <strong>the</strong> value ofintroduced variation will also increase.It is not possible to predict <strong>the</strong> futuregenetic demands that may be placed onwheats as new races of pathogensappear or as cultivation is extended intonew areas. Consequently, a stock ofalien genetic material introduced fromwide hybrids may prove to be of greatvalue.It appears that <strong>the</strong> use of wide hybridsand <strong>the</strong> derived genetic material in <strong>the</strong>Triticeae will provide an expandingsource of genetic variation for plantbreeders which, in some cases, mayeven amount to quantum changes inei<strong>the</strong>r <strong>the</strong> production or distribution of<strong>the</strong> crop.Reference1. Mujeeb-Kazi, A., and G. Kimber.The production, cytology andpracticality of wide hybrids in <strong>the</strong>Triticeae. (In preparation.)

130Wheat in West AfricaG. Varughese, Wheat Program, CIMMYT, MexicoAbstractAlthough wheat has been grown in small amounts in West Africafor manycenturies, it is only in <strong>the</strong> last 20 years that it has become an importantfoodsourcefor <strong>the</strong> increasing urban population. Because of this increasing demand.governments in <strong>the</strong> region are becoming interested in <strong>the</strong> possibility ofgrowingwheat, a crop that should be successful, dependent on <strong>the</strong> development ofadapted cultivars and appropriate agronomic practices. Also needed will betrained personnelfor research and extension, and improved transport andmarketing systems.Wheat came to West Mrica manycenturies ago through <strong>the</strong> salt traderoutes. Later on, it was also brought inby Muslim pilgrims. It used to be grownin very small areas in many Mricancountries, more for use in religiousceremonies than for human food. Thissituation, however, has changeddramatically dUring <strong>the</strong> past twentyyears, and today wheat is an importantsource of calories for many of <strong>the</strong> WestAfrican countries. In fact, Sub-SaharanMrica has one of <strong>the</strong> highest growth...ates in wheat consumption in <strong>the</strong>world, mainly utiliZing imported wheat.Most of <strong>the</strong> wheat is consumed in urbanareas and, since <strong>the</strong> urban populationin <strong>the</strong>se regions is continuing toexpand, <strong>the</strong> upward trend in wheatconsumption is also likely to increase.This rapid expansion in <strong>the</strong>consumption of wheat has promptedmany governments in <strong>the</strong> region toconsider <strong>the</strong> possibility of grOWingwheat.The countries In <strong>the</strong> region haVing atleast some potential for growing wheatare Senegal, Mali, Upper Volta, Niger,Nigeria and Chad. The socioeconomicdifficulties related to producing wheat isdifferent for each of <strong>the</strong>se countries.However, agroclimatic patterns andvarietal needs are similar for all of <strong>the</strong>countries of <strong>the</strong> region.Almost all of <strong>the</strong> wheat grown in WestAfrica is irrigated, and is planted aboutmid-November and harvested in earlyMarch. Most of <strong>the</strong> soils are heavy clayswith very low water infiltration.However. <strong>the</strong>re are also a few areaswith sandy soils in <strong>the</strong> region. Wintersin general are mild, with high rates ofevapotranspiration. thus necessitatingfrequent irrigation. Planting date andwater management are <strong>the</strong> two mostcritical factors for a successful crop.At present, Siete Cerros and itsderivatives are <strong>the</strong> best-adapted wheatvarieties for <strong>the</strong> region. Fortunately,disease is not a factor limiting wheatproduction.Country SituationsSenegalWith <strong>the</strong> exception of Mauritania.Senegal has <strong>the</strong> highest per capitawheat consumption in West Africa. In<strong>the</strong> 1975-1977 period, wheatconsumption was 23 kg per capita peryear. The government of Senegal, with<strong>the</strong> help of FAO/UNDP, had an excellentwheat research project in Guede in <strong>the</strong>Senegal River valley from 1976 to1982. Researchers at <strong>the</strong> station haveconsistently obtained yields of 3 to4 tons per hectare. The variety Mexipakhas yielded an average of 3.6 t/ha overfive years, with a maximum of 5 and aminimum of 3 t/ha. In farmers' fields.on commercial-sized plots. yields have

131averaged about 2.5 tonslha. However,wheat in Senegal is still anexperimental crop. It is possible that, in<strong>the</strong> future, Senegal can grow wheat in<strong>the</strong> Senegal River basin.Mall .Fanners in <strong>the</strong> Niger delta have grownwheat in small plots for hundreds ofyears. Recently, with <strong>the</strong> introductionof small irrigation projects along <strong>the</strong>Niger river near Dire and Timbuktu.<strong>the</strong> wheat area has expanded. There arethree aid projects in operation in <strong>the</strong>region. one each by Belgium. Franceand <strong>the</strong> USA. and all are involved invarious aspects of wheat culture. Thelocal varieties grown are Hindi Tossonand Alkama Tireye.NigerWheat cultivation in Niger is ancient.The main wheat area is in <strong>the</strong> Agadezregion. Close to 1000 hectares of wheatare grown in this region. all of which islocally consumed. At present. attemptsare being made to grow wheat in <strong>the</strong>area of <strong>the</strong> Konni Irrigation Project.Local varieties <strong>the</strong>re are Bahause.Hayatang. Tawat and a recentreselectlon. Dambata. The varietiesbeing planted experimentally at Konniare Florence Aurora and Danbata.NigeriaAmong <strong>the</strong> West African countries.Nigeria has <strong>the</strong> greatest productionpotential and <strong>the</strong> largest wheat area. Itis grown in three different states, Bono,Kano and Sokoto. in <strong>the</strong> large-scaleirrigation projects. Mexipak andINIA 66 are <strong>the</strong> two most Widely grownvarieties. At present, more than 10,000hectares are devoted to wheat. but <strong>the</strong>country has <strong>the</strong> potential for expandingthis amount to 100.000 hectares in <strong>the</strong>future.ChadWheat used to be a regular crop aroundLake Chad. The area was beingexpanded in <strong>the</strong> mid-1970s. but <strong>the</strong>re islittle information presently availablebecause of <strong>the</strong> civil war in <strong>the</strong> country.CODclusioDSWheat can be grown successfully inmany West African countries. The needfor an intensification of croppingpatterns. <strong>the</strong> lack of trained personnelto conduct production agronomyresearch and extension and <strong>the</strong> lack oftransport and adequate marketingsystems are <strong>the</strong> major problems facingwheat production in West Africa.

132Wheat Varietal DevelopmentStrategy in BangladeshL. Butler, Wheat Program, CIMMYT, Joydebpur, Dhaka, BangladeshAbstractAgainst a background of variable planting dates. water availability. andfarmerpreferencefor <strong>the</strong> variety Sonalika, white-seeded varieties need to be developedwithflexibility in terms ofyield response to a number ofcropping situations.This challenge is being met by a national varietal improvement program.wherein material is advanced only If it demonstrates <strong>the</strong> ability to yield as wellas Sonalika when planted late in <strong>the</strong> season and/or under dryland conditions;its yield must be consistently better when planted early and/or under irrigatedconditions.A bird's-eye view of <strong>the</strong> BangladeshWheat-growing areas would reveal amosaic of differing crop stages andstands, largely defined by date ofplanting and water availability. In onearea. farmers may plant <strong>the</strong>ir crop latein December: in ano<strong>the</strong>r, in midNovember. Irrigated and dryland cropsmay stand side-by-side. Fur<strong>the</strong>r. <strong>the</strong>patterns can shift annually. due tochanging facilities and <strong>the</strong> vagaries ofwea<strong>the</strong>r. A farmer who plants his cropexclusively on dryland one year may.as a result of buying a shallow tubewell. irrigate a mixed pattern of riceand wheat <strong>the</strong> next. Due to excessiveflooding dUring <strong>the</strong> monsoon season, afarmer is sometimes forced, against hisusual practice of planting rice as earlyas possible, to plant late, <strong>the</strong>rebycausing him to harvest late and.subsequently. to plant his wheat croplate as well.The availability of time and water for<strong>the</strong> growth of wheat in Bangladesh ismuch less than that of more productiveareas. such as <strong>the</strong> Punjab in India andPakistan and <strong>the</strong> Yaqui Valley inMexico. There are about 120 days in<strong>the</strong> crop cycle at best. and about 70%of <strong>the</strong> crop is planted undernonirrigated conditions.The average national yield is about2 tIha; even under <strong>the</strong> most favorablecircumstances. yields have notexceeded 4.5 to 5 Uha in farmers' fields.Generally. mid-November planting ismost favorable for production. On <strong>the</strong>average. yields are reduced about 1%for each day that planting is delayedafter <strong>the</strong> end of November.In order that no losses are incurredthrough shriveling. grains must ffil by<strong>the</strong> first week of March at <strong>the</strong> latest:after that time. temperature andrelative humidity rise rapidly. However.about 75% of <strong>the</strong> wheat area is plantedin December. with about 60% aroundmid-December, effectively leaving only90 to 100 days for <strong>the</strong> production of acrop. This situation has placed apremium on <strong>the</strong> development of shortdurationvarieties.Sonalika. <strong>the</strong> predominant commercialvariety, matures in about 95 days ifplanted in mid-December and produceslarge. white seed and consistent (goodas-ean-be-expected)yields in a varietyof cropping situations. However.Sonalika is fully susceptible to leaf rust(Puccinia recondita) and must bereplaced or, at <strong>the</strong> very least. <strong>the</strong> area itoccupies diluted with resistant varieties.Resistance to leaf rust is not a greatselling point, however. since epidemicsusually start very late and damage isgenerally insignificant: new varieties

133must also demonstrate a yieldadvantage. Fur<strong>the</strong>r. farmer preferencefor Sonalika is so pervasive that it isnearly considered synonYmous withwheat.Against this backdrop of variable datesof planting. water availability andvarietal preference. white-seededvarieties must be developed which canbe planted late and/or on drylands.while also responding favorably to earlyplanting and/or irrigated conditions. Inall probability. <strong>the</strong> perfect. miraclevariety will not be found that <strong>the</strong>separameters suggest is needed;obViously. some compromises will benecessary.The development of a number ofdifferent varieties. each with itscharacteristics favorable to a givensituation. is always suggested.However. 75% of <strong>the</strong> annual wheatseed requirement is stored by farmersand. suprisingly. a good percentage ofsuch seed survives <strong>the</strong> humid monsoonseason with a high level of germination.They cannot store seed safely for morethan six months. nor are <strong>the</strong>y willing tostore a number of varieties. selected for<strong>the</strong> different kinds of situations <strong>the</strong>ymay have on <strong>the</strong>ir own land (and whichmay change annually). Fur<strong>the</strong>r. <strong>the</strong>national seed production program.although producing good quality seed.is not sufficiently sophisticated toefficiently grow and distribute anumber of different varieties insufficient quantities that demandrequires. The present program. instead.is directed toward <strong>the</strong> selection of <strong>the</strong>maximum amount of flexibility ingermplasm. in terms of its droughttolerance/favorable response toincreased water availability. andtolerance to late planting/favorableresponse to earlier planting.Material is available with maturitiesand drought resistance comparable toSonalika. but with no particular yieldadvantage. Yields. of course. generallydecline with decreasing time-tomaturity.The probability of selecting avariety with similar duration anddesirable characteristics of Sonalika.and with a consistent yield advantage.is quite low. Ra<strong>the</strong>r than to exclusivelyselect for varieties that are similar toSonalika. selection is also made forvarieties which. under both irrigatedand water-stress conditions. are ofsomewhat longer duration thanSonalika (but no more than a weeklonger). They must also be tolerant toheat-forced maturation while stillmaintaining a reasonable yield andseed quality and. if planted at a morefavorable date. yield consistently better.All pre-trial material. irrigated ordryland. is selected at a favorable dateof planting (November 15 to 30) and alate date (December 15 to 30). at leastonce before being allowed to progress to<strong>the</strong> national screening nursery. <strong>the</strong>Bangladesh Screening Nursery (BSN).Individual plants from international andlocally generated segregating materialare alternately selected at favorable andlate dates of planting up to <strong>the</strong> F6generation (e.g.• plants are selected at afavorable date in <strong>the</strong> F2. F4 and F6generations. and at a late date in <strong>the</strong> F3and F5 generations). Lines may be cutin bulk if selected for <strong>the</strong> BSN startingwith F6; <strong>the</strong> F7 and F8 generations arealso planted at a favorable date.However. all F2 material is first selectedunder irrigated conditions; seeds ofselected plants are divided and <strong>the</strong>populations are <strong>the</strong>reafter tested atalternate dates. simultaneously underboth irrigated and water-stressconditions.Lines selected for <strong>the</strong> BSN are plantedat seven locations; three of <strong>the</strong> sets areplanted under water-stress conditions.Lines of good appearance. with leaf rustresistance. absence of physiogenic leafand spike problems. and yielding wellformed.clean seeds in a majority of

134locations. are selected for yield trials.Although <strong>the</strong> apparent ability of anygiven line to perform well under onlyirrigated or dryland conditions wouldnot necessarily exclude it from fur<strong>the</strong>rconsideration. it would have to beselected at ei<strong>the</strong>r all <strong>the</strong> irrigated or all<strong>the</strong> dryland sites.Lines selected from <strong>the</strong> BSN are testedfor three years in experiment stationtrials which are planted at bothfavorable and late dates of planting. andunder both irrigated and drylandconditions. Selection criteria. inaddition to those mentioned above.require that a line must perform as wellas Sonalika at a late date of planting.and better if planted at a favorable dateunder irrigated and/or drylandconditions. Lines advanced through <strong>the</strong>third year of trials are grown <strong>the</strong> fourthyear in large unreplicated plots on bothfanners' fields and experiment stations.This stage is critical; for a line to bereleased by <strong>the</strong> National Seed Board. itsgood performance must be observed in<strong>the</strong> field by a committee selected by <strong>the</strong>Board.This strategy may appear complicated;however. as a result of <strong>the</strong> stringentselection criteria, <strong>the</strong> number of linesadvanced annually are diminishedconsiderably. <strong>the</strong>reby redUcing <strong>the</strong>amount of material that must behandled in trials. For example. in <strong>the</strong>third-year trials of 1984-85. only tenlines including checks will be entered.In any case. it is felt that this strategy ispracticable. since it shows thatgermplasm with <strong>the</strong> required fleXibilityis available.Recently released varieties. on <strong>the</strong>average. yield 10% more than Sonalikaif planted at a favorable date, and aswell as Sonalika when planted late. Allhave maturities of three to seven dayslater than Sonalika. and all perform aswell and often better under water-stressconditions than Sonalika. Thesevarieties. in fact. were developedwithout employing <strong>the</strong> above strategy;it appears. however. that <strong>the</strong> presentprogram will streamline <strong>the</strong> selectionprocess and make possible <strong>the</strong> earlyidentification of appropriate material.

135II. Diseases and Disease ControlBreeding Wheats for Resistanceto Helminthosporium Spot BlotchY.R. Mehta. ID.tltuto Agricola de Parana. LondriDa. Parana. BrazilAbstractSpot blotch caused by Cochliobolus sativus (Bipolaris soroldniana. Syn.Helminthosporium sat!vum) is one of <strong>the</strong> most important diseases in a number ofcountries. such as BraziL Paraguay. Bolivia. India. Bangladesh and Thailand. Inrecent years. breedingfor resistance to this disease has been gainingimportance. This paper discusses some of <strong>the</strong> principal aspects involved inbreeding. including genetic variability in <strong>the</strong> pathogen populations. screeningthisfor resistance (inoculum. inoculation andfteld trials). identtjlcation ofsources of resistance in alien species and transfer of resistance to advancedlines or varieties. lriformatton on some of<strong>the</strong> resistant lines presently availablein wheat against B. soroldniana is also provided.Spot blotch of wheat. commonly knownas helminthosporium. is caused by <strong>the</strong>fungus Cochltobolus sativus Ito etKurtb Bipolarts soroldntana Sacc. exSoroldn. (Syn. Helmtnthosporiumsativum P.K. and B). B. sorokinianacan attack all plant parts. It isconsidered important in a number ofcountries since <strong>the</strong> resulting losses inyield are appreciable. Severe epidemicsof spot blotch are frequently registeredin some tropical countries. Spot blotchepidemics in India and neighboringBangladesh and Thailand have recentlybeen reported (7). Spot blotch is alsoconsidered one of <strong>the</strong> most importantdiseases in Mrica (14). In <strong>the</strong> USA. on<strong>the</strong> o<strong>the</strong>r hand. it is considered ofsecondary importance. although itsgeneralized occurrence was registeredin Minnesota in 1979 and 1980 (18).In Latin America. <strong>the</strong> importance ofspot blotch is restricted to Brazil.Paraguay and <strong>the</strong> Santa Cruz area ofBolivia (5). During <strong>the</strong> years 1979 to1982. severe epidemics of <strong>the</strong> diseaseoccurred in Paraguay. causing heavyyield losses. In Brazil. spot blotch is ofgreat importance. The disease occursevery year in all of <strong>the</strong> wheat-growingareas of <strong>the</strong> country. and severeepidemics were registered in <strong>the</strong> statesof Parana. Sao Paulo. Mato Grosso doSul and BrasUia. D.F. during <strong>the</strong> years1976. 1979. 1980. 1982 and 1983(9. 10). Under favorable conditions for<strong>the</strong> disease. <strong>the</strong> losses in yield can bebetween 30 and 80%: in some fields<strong>the</strong>y can reach 100%. Because of itsimportance. chemical control measuresfor spot blotch are being applied inorder to obtain stabUity in cropproduction. Ano<strong>the</strong>r way to control <strong>the</strong>disease is through varietal resistance.Genetic VariabilityAs a rule. in breeding for diseaseresistance. it is necessary to have amplegenetic variabUity within <strong>the</strong> hostpopulations. as well as within <strong>the</strong>pathogen populations. To exploitexisting genetic variabUity in <strong>the</strong> hostplant. it is important to determine <strong>the</strong>genetic Variability of <strong>the</strong> pathogenpopulations. For this purpose. <strong>the</strong>different virulence strains of <strong>the</strong>pathogen must be identified.

136Attempts to identify <strong>the</strong> races ofB. sorokiniana were made as early as1922 (3). Based on morphological andpathological characters, Christensen (3)identified at least 37 races of thisfungus. Clark and Dickson (4), whileworking on B. sorokintana on barley,reported that <strong>the</strong> isolates differedsignificantly in pathogenicity. Wood(19) strongly believed in <strong>the</strong> existenceof physiological races within B.sorokiniana and reported that isolatesof this fungus differed strikingly in <strong>the</strong>irparasitic capabilities, regardless of <strong>the</strong>plant or geographical source. It is wellknown that B. soroktntana is anextremely variable fungus: progeniesfrom a single conidium may differ inpathogenicity. Constant mutation andsaltation are o<strong>the</strong>r problems whichmake race identification stUl moredifficult.To distinguish between races or strains,it is necessary to establish a differentialset of cultivars. Recently, Mehta (11)established a preliminary set of 13differential cultivars and identified atotal of 32 races. These races, whentested on adult plants. differedstrikingly from each o<strong>the</strong>r as to sporeproduction and lesion size (12). Todetermine Variability in <strong>the</strong> pathogenpopulation, a large number ofmonoconidial isolates had to beobtained from different locations. fromdifferent wheat varieties or from relatedplant species over a period of two tothree years.Mehta (11) reported that <strong>the</strong> reactionpattern of <strong>the</strong> races on <strong>the</strong> variouscultivars was altered in most cases after<strong>the</strong> isolates had been stored eight to tenmonths. It is well known that <strong>the</strong>isolates change or even lose <strong>the</strong>irpathogenic capability after a period oftime. This is why <strong>the</strong> term "race" forB. sorokiniana has been questioned.Once <strong>the</strong> standard differential set ofcultivars is established, <strong>the</strong> strains withdifferent virulences (races) can beidentified at any time by using freshmonoconidial isolates. Such isolatescan, in turn, be used for <strong>the</strong>identification of broad-spectrumresistance. Recent work in <strong>the</strong> IAPARlaboratory shows that <strong>the</strong> monoconidla1isolates can be maintained in conidialform on sterilized mter paper discs(11) with fewer problems of mutationand loss of virulence for up to threeyears. Fur<strong>the</strong>r work is necessary with<strong>the</strong> preliminary set of differentialcultivars: it needs to be standardized sothat it can be used by scientists indifferent countries.ScreenlDg for ResistanceScreening for resistance is an importantstep in breeding for disease reistance.Screening techniques must be reliable.so that <strong>the</strong> resistant material thusselected can be incorporated into <strong>the</strong>crossing blocks with confidence.Screening for resistance is generallydone in a greenhouse or in a walk-incold chamber, but always undercontrolled conditions: all plantmaterials must be tested understandard and uniform conditions. Anychange in <strong>the</strong> quality of inoculum,inoculation technique, incubationperiod and environmental conditionsmay alter <strong>the</strong> reaction pattern.Inoculum preparationFor screening purposes, a goodinoculum must include a mixture ofseveral Virulence isolates and anappropriate and constant amount ofviable conidia in <strong>the</strong> suspension.Inoculum of different virulence isolatescan be multiplied separately onautoclaved sorghum seeds inErlenmeyer flasks at room temperature(20 to 25°C). Over a period of threeweeks, abundant spore increase can beobtained on <strong>the</strong> sorghum seeds. Fiftygrams of such seeds are placed in a

137beaker with 200 ml sterilized distilledwater and shaken thoroughly. Theconidial suspension is filtered through acheese cloth; it can be diluted byadding more water or streng<strong>the</strong>ned byadding more seed. so as to arrive at aconcentration of 33.000 to 43.000conidia per ml of water.It is not necessary to count conidia in ahemocytometer. To determineconcentration. <strong>the</strong> count can be madeunder a microscope with a magnificationof 150 (15 ocular x 10 objective). Ifan average of 8 to 12 conidia areobserved per microscopic field. <strong>the</strong>n aconcentration of 33.000 to 43.000conidia/ml is assured. This method isnot time consuming and gives uniformresults. The conidial suspension of all<strong>the</strong> isolates at proper concentration ismixed toge<strong>the</strong>r and. for every 200 ml ofconidial suspension. a drop of stickerSandovit. manufactured by Sandoz. isadded. The resulting mixture is usedfor inoculation. Normally. germinationtests for conidia are not necessary. butexperience has shown that. if <strong>the</strong> flasksare incubated for over three weeks. alarge amount of conidia lose <strong>the</strong>irViability. This procedure is also used toinoculate <strong>the</strong> segregating populationsand advanced lines in <strong>the</strong> field; <strong>the</strong> lessdiseased plants with smaller leasionsare selected.At research stations where laboratoryfacilities are not yet available. <strong>the</strong>inoculum for segregating populationsmay be prepared in a simpler way.Conidial dust may be collected from <strong>the</strong>combine soon after harvest. especiallyfrom fields heavily infected byB. sorokiniana. Such dust normallycontains about 70 to 80% conidia. Thisdust is dried in a desiccator for 72hours. kept in glass bottles and storedin <strong>the</strong> regrigerator. Experience showsthat conidial dust can be stored in aviable form for over two years. To getgenetic variability in <strong>the</strong> pathogenpopulations. it is necessary to collectconidial dust from several varieties andseveral locations. At time of inoculation.<strong>the</strong> dust from different locations andvarieties is mixed in equal proportions.and <strong>the</strong> segregating populations andadvanced lines are sprayed.InoculationIn <strong>the</strong> greenhouse. it is preferable thatplant material be tested for resistanceat two growth stages. at <strong>the</strong> seedlingstage and also at <strong>the</strong> adult plant stage.To confirm <strong>the</strong> reaction pattern. <strong>the</strong>test should be repeated for each growthstage; it has been shown that seedlingreaction does not necessarilycorrespond with adult plant reaction.Although adult plant resistance isalways preferred. tests on seedlingshelp to determine lines that showresistant reactions at both growthstages. Such lines are of great interestin programs breeding for resistance.For seedling tests. plants can be grownin soil in plastic trays (55 x 30 x12 cm). One row with 10 to 12 plants ofeach variety is planted; a total of twelvevarieties can be grown per tray. Twentydays after sowing. <strong>the</strong> seedlings areinoculated uniformly. using a smallatomizer and a pressure pump. Theinoculated plants are incubated in <strong>the</strong>dark for sixteen hours at 20° ± 1°Cand at near 100% humidity. Later. <strong>the</strong>yare incubated for seven days at 20°C ina walk-in cold chamber with fluorescentlamps for alternate cycles of twelvehours light and twelve hours darkness.Readings on infection are taken sevendays after inoculation. using anappropriate scale for reaction score (II).The adult plant test can be performedby grOWing <strong>the</strong> plants in ear<strong>the</strong>n pots25 cm tall and 20 cm in diameter.Normally. five plants are grown per pot;a total of ten plants per variety are usedto determine variety reaction. Only <strong>the</strong>flag leaves are inoculated soon afteremergence. They are washed withdistilled water. gently rubbed between<strong>the</strong> fingers and <strong>the</strong>n. while being held

138upright, are given a qUick spraying,from <strong>the</strong> top to <strong>the</strong> bottom of <strong>the</strong> leafand <strong>the</strong>n from <strong>the</strong> bottom to <strong>the</strong> top.The rest of <strong>the</strong> procedure is <strong>the</strong> same asthat for <strong>the</strong> seedling test.Field trialsAlthough greenhouse tests are reliable,it is often necessary to conduct fieldtrials to confirm varietal reaction undernatural conditions. In institutionswhere controlled environmentalconditions are not present, screeningtests can be perfonned in <strong>the</strong> field withartificial inoculations. All of <strong>the</strong>resistant lines selected in <strong>the</strong>greenhouse are tested under fieldconditions over a period ofat least twoyears. It is important that tests beperfonned at three to four hot-spotlocations each year. It is worthwhile toinclude resistant and susceptible checksin <strong>the</strong> nursery, and it should besurrounded by a susceptible spreader.Inoculum is prepared in <strong>the</strong> same wayas for greenhouse tests, and <strong>the</strong>conidial suspension sprayed on <strong>the</strong>spreader as many times as necessary toobtain a severe epidemic.Disease ratings should be taken at leasttwice, once at <strong>the</strong> heading stage andonce at <strong>the</strong> soft dough stage. However,if time pennits, weekly readings arevery useful. From <strong>the</strong> disease progresscurve, <strong>the</strong> rate of infection can becalculated; <strong>the</strong> lower <strong>the</strong> rate ofinfection, <strong>the</strong> higher <strong>the</strong> degree ofresistance (12). Agronomically desirablelines with low infection ratings are usedas sources of resistance in <strong>the</strong> breedingprogram.Through this process, some lines havebeen selected (Table 1). However, <strong>the</strong>yneed to be tested fur<strong>the</strong>r at o<strong>the</strong>rresearch stations before being used forgeneral breeding purposes. Table 2indicates some lines resistant toB. soroktntana, based on screeningsmade in Zambia, Brazil and Bangladeshin 1980-81 (13). In India, Adlakha et al.(1) tested 625 wheat lines and reported16 lines resistant to B. soroktntana;HD1927 was considered to be <strong>the</strong> best.They believe that sources of resistanceare readily available in wheat.Table 1. Resistant lines to spot blotch (8. sorokiniana) based on field screenings, Londrina,Brazil, 1982-83Resistance reaction~/Variety/cross Londrina Palotina S. MiguelPamir"S"CM20834-A-7Y-501 Y-502Y-DB 8 MR, 30 MS 30 MS 10 MS, 20 MRPF7339=Sonora 64-SKe xL R64A/1 AS49HorizonVeery"S"CM33027-F-12M-1Y-3M-1Y-OM12S,45MS 8MR,20MR 25MS,5MR1 MS,40MS 5MR,20MS 5MR,20MRTMR, 20 MS 8 MS 20 MS, 15 MS

139Table 1. (Cont'd)Resistance reaction..!lVarietyIcross Londrina Palotina S. MiguelOCEPAR·9-Perdiz TMS, 25 MS 25MSCNT1=PF11.1000Q.62-BHl146 TMR, TMR 3 MS, 5 MR/MS 5 MR, 5 MRFrontana 15 MS 30MS 20MRBHl146=Fronteira-Mentana x P.G.1 9S, 40 MS 21 MS 8 MS, 20 MRJacui=S8-Toropi 5MS 30MS 5MRLD7815 20MS 20MS 10MRLD7821 10MS 15 MRLD8115=AlondraIlCNT7/PF7035413/PAT24/Bluebird/KalyansonaII 19170-2L-25L-8L·OL 10MR 25MRLD81151=IAC17/Alondra"S"I 18314-0F-27L-l0L-7L-OL 10 MS 15 MRPAT7219 10 MS 10MRPAT7392 20MS 10 MR 10 MRBR8=IAS20-Tp x PF70100 20MR 10MRKinglet''S''CM33089-W·3M-7Y-3M·OY 20MS 15 MSLD8032=PAT72195-Musala x TRM113746-1 Ld-12Ld-4Ld-QLd 35MS 20MSLD8038=JUP-Moncho19312·1 Ld-8Ld-7Ld-OLd 30MS 30MSLD8077=IAS55-Alondra"S"I 18310-0F-30Ld-15Ld-OLd 25MS 20MSPEL73015 15MS 30MS 5MR.E.I MR = moderately resistant, TMR = trace to moderately resistant,MS = moderately susceptible, S = susceptible

140Table 2. Results of screening for resistance to Bipo/aris sorokiniana, Mexico, Brazil,Bangladesh and Zambia, 1981·82Cross and pedigreeResistance foundto be presentKavkaz-HD2009, SWM2984-1M·1Y-1M-2Y-OM·OMCRT·Alondra"S", II 14055-0M·7LD-5LD-l LD-OYCRT-Alondra''S'', 1/ 14055·0M-7LD-5LD·2LD-OYCRT-Alondra"S", II 14055-0M-7LD·l LD·OYCRT-Alondra''S", II 14055-0M-19LD-25LD·l LD-OYTOB"S"/CN067.JAR x Kavkaz, CM20707-A·1Y-8M-1Y-OY-2PTZ-OYTOB"S"/CN067-JAR x Kavkaz, CM20707-A-1Y·8M-1Y-OY-4PTZ-OY(TOB"S"·NPO x Correcaminos-I NIA/CNO-N066)SJ''S''Tanager"S", CM30697·16Y·7M·1Y·OMPewee"S", CM31630·H·3Y-1 M-6y-oMKalyansona-Bluebird x CJ''S''/Alondra''S'', CM324214M-1Y-2M-2Y·OMBanaquit"S", CM32556·3M-501Y-519M-oyHarrier''S'', CM33435·P-1M·1Y-OMCBC148/5/INIA/3/LR64*2/SN64//CC/4/CC/INIA"S"/6/VLD''S''CM33683·A4M·l Y·1 M-OYTOW"S", CM34709·B·3M-l Y-l M-1Y-OMBJYIS"-Grajo"S"(LR64·SN64 x TZPP·AN64/BBxTOB-CNO)CM34742-E·2M-9Y-OMFury-M073, CM36732·16Y·15M-4Y-OMOLN-TRM, CM36820-10Y·1M-1Y·OMBonanza-JUP73, CM36872-27Y-3M-2Y-OMBR74.72-COC75, CM36889·31Y-l0M-OYGOV·AZ67 x Musala"S", CM41257-1-8M-3Y-OMERA-MN69.146 x Pavon 76, CM52349-1MM-OMMBHl146L2000.731MN72135PF69129PF71131PF7339xxxxxxxxxSource: Rajaram eta/, (13)

141Identification ofSources of ResistanceSources of resistance to B. sorokinianain species o<strong>the</strong>r than Triticumaestivum are of special interest in <strong>the</strong>breeding program. The use of aliengene pools for disease resistance haslong been known (8). Breeding forspecific resistance againstPhytophthora infestans in potatostarted as early as 1949. when a genepool for resistance was discovered inSolanum demtssum (16). In recentyears. <strong>the</strong>re have been several reportson <strong>the</strong> use of gene pools for resistanceto rusts. septoria and mildew in wheatfrom some closely related species (2.17).CIMMYT has been making some effortto incorporate alien resistance genesalready in <strong>the</strong> wheat background (6).Recently. <strong>the</strong>y have obtained somesegregating lines resistant toB. sorokiniana from wheatcombinations with Aegtlops elongatumand Elymus giganteus (M. Kazi.personal communication).Never<strong>the</strong>less. information on <strong>the</strong>sources of resistance to B. sorokinianain species o<strong>the</strong>r than T. aestivum isst111 very scant. and attempts should bemade to identify sources of resistance inas many alien species as possible. Suchinformation would help for geneticallycombining different sources ofresistance. Also. relatively littleinformation is available about <strong>the</strong>underlying genetic mechanism ofresistance. Adlakha et al. (1) reportedthat resistance in wheat toB. sorokiniana was conditioned by oneor two dominant factors; similarconclusions were reached by Srivastavaet al. (15). Fur<strong>the</strong>r work may benecessary to understand more about<strong>the</strong> inheritance of resistance.Transfer of Resistanceto Advanced Lines or VarietiesUntil recently. very little emphasis hasbeen given to breeding for resistance toB. sorokiniana. During <strong>the</strong> past tenyears. much improvement has beenmade in wheat production. especially in<strong>the</strong> Latin American region. through <strong>the</strong>introduction of Mexican varieties withhigh yield potential and improveddisease resistance. mainly to <strong>the</strong> rusts.Some of <strong>the</strong> varieties have failed tocreate an impact in some areas due to<strong>the</strong>ir susceptibility to B. sorokinianaand <strong>the</strong> local complexes of diseases.There are only a few examples of fieldresistance to B. sorokiniana withineXisting commercially grown varieties.Among <strong>the</strong>m are <strong>the</strong> Mexican varietiesAlondra and Cocoraque. which haveshown reasonably good performanceagainst spot blotch in farmers' fields.Alondra. a semidwarf wheat with a bigspike. has become an importantprogenitor in numerous crosses withBrazilian wheats. Among <strong>the</strong> Brazilianvarieties. BH1146. CNT1 and PAT7219have <strong>the</strong> best resistance. Thus. due to<strong>the</strong> fact that a majority of commercialvarieties are susceptible or highlysusceptible to B. sorokiniana. breedingfor resistance to B. sorokiniana hasrapidly gained importance in recentyears.Once <strong>the</strong> sources of resistance inT. aestivum or alien species areconfirmed. <strong>the</strong> problem of incorporatingsuch resistance in agronomicallydesirable varieties arises. By and large.<strong>the</strong> pedigree selection method isfollowed by most breeders andpathologists. After passing throughseveral field and greenhouse screeningtests. resistant lines are tested for yield.included in <strong>the</strong> crossing block, andselections for resistance and agronomic

142characters made in segregatingpopulations. Heavy inoculum pressureis a prerequisite to testing and. during<strong>the</strong> process of subsequent selections.<strong>the</strong>re is <strong>the</strong> danger that resistance willbe lost. Never<strong>the</strong>less. if a particularsource possesses a very high degree ofresistance. it will be able to endurethrough <strong>the</strong> pedigree method. In Brazil.a high degree of resistance has not yetbeen found in T. aestivum. It ispossible that. in most cases. resistanceis polygenic and is governed by minorgenes.Quite frequently. a bulk or modifiedbulk system is used when desirablecharacters are obscured by unfavorableenvironmental conditions or o<strong>the</strong>rstresses. The backcross method alsomight be used with success to transferresistance to B. sorokintana. Thismethod works best when resistance isgoverned by one or only a few majorgenes. The CIMMYT germplasmdevelopment program has used thismethod to incorporate diseaseresistance into acceptable plant types(M.M. Kohli. personal communication).In case resistance to B. sorokintana isgoverned by a large number of minorgenes with low expression and lowheritability. <strong>the</strong> best approach would beto use <strong>the</strong> recurrent selection method.The aVailability of some effectivegametocides makes <strong>the</strong> method feasibleand would help to establish a largenumber of genetic pools which couldsubsequently be combined. Thesegenetic pools or recurrent selectionpopulations could serve as a bridge fortransferring resistance without losingimportant characters such as yield andadaptation.There is an urgent need to identifyresistant sources in alien speCies.Transfer of resistance from such speciesto T. aesttvum is a ra<strong>the</strong>r complicatedand difficult task. Difficulties in makinginterspecific crosses is due mainly todifferences in levels of ploidy (8).However. problems such as lack ofchromosome pairing and crOSSing-over.failure of crosses after fertilization.difficulties in rearing hybrid plants and<strong>the</strong> lack of Vigor and fertility of hybridplants can be overcome by <strong>the</strong> use ofvarious techniques and chemicals suchas colchicine and gibberellin.Information on"<strong>the</strong>se points is given byKnott and Dvorak (8).In general. <strong>the</strong> most important objectiveof breeding programs is to enhanceyield stability through effectiveresistance to a complex of diseases.However. uniform screening proceduresand techniques have not yet been fullyimplemented. InVariably. diseasescreeninghot spots are lacking. andartificial inoculation techniques varyamong national programs. Althoughplant pathologists have beguninoculating selected materials toidentify progenitors. segregatingpopulations and advanced lines are stillbeing selected under variable andnatural disease pressure. Only uniformartificial inoculation can guarantee <strong>the</strong>successful screening of germplasm forresistance to B. sorokiniana. A networkof hot-spot locations for this diseaseneeds to be established within eachcountry in order to permit uniformscreening and. consequently. providereliable information on resistance.

143References1. Adlakha, K, RD. Wilcoxson andS.P. Raychaudhuri. 1984.Resistance of wheat to leaf spotcaused by Bipolaris sorokiniana.Plant Disease 68(4):320-321.2. Auster, M.Y., E. Levi and Z. Eyal.1983. Assessment of interactionsbetween cultivated and wild wheatsand Septoria tritict. Phytopathology73:1077-1083.3. Christensen, J.J. 1925. Physiologicspecialization and mutation inHelminthosportum sativum.Phytopathology 15:785-795.4. Clark, RV., and J.G. Dickson.1958. The influence of temperatureon disease development in barleyinfected by Helminthosportumsativum. Phytopathology 48:305310.5. Dubin. H.J. 1984. Regional and incountryactivities: Andean region.In Report on Wheat Improvement1981. CIMMYT, Mexico.6. Dubin, H.J., and S. Rajararn. 1982.CIMMYT's international approachto breeding disease-resistant wheat.Plant Disease 66(10):967-971.7. Joshi, L.M., KK. Srivastava,D.V. Singh. L.B. Goel and S.Nagar~an. 1978. AnnotatedCompendium of Wheat Diseases inIndia. Indian Council onAgricultural Research, New Delhi,India.8. Knott, D.R. and J. Dv01ak. 1976.Alien germplasm as a source ofresistance to disease. AnnualReview of Phytopathology 14:211235.9. Luz, W.C., G.C. Luzzardi andJ.C. Santiago. 1976. Pesquisa defontes de resistencia a helminthosporiose(Helminthosporiumsativum P.KB.) do trigo. Paperpresented at <strong>the</strong> Eighth AnnualWheat Research Meeting,EMBRAPA. Ponta Grossa, Parana,Brazil.10. Mehta, Y.R 1978. Doencas do trigoe seu controle. Ed. AgronomicaCeres, Sao Paulo e SummaPhytopathologica. Sao Paulo, Brazil.11. Mehta, Y.R. 1981. Identification ofraces of Helminthsoporiumsativum of wheat in Brazil.Pesquisa Agropecuaria Brasiliera(Brasilia) 16(3):331-336.12. Mehta, Y.R 1981. Conidialproduction, sporulation period andextension of lesion ofHelminthosporiumsativum on flag leaves ofwheat. Pesquisa AgropecuariaBrasiliera (Brasilia) 16(1):77-99.13. Rajararn, S., P. Brajcich andL. Butler. 1984. Bread wheatimprovement. In Report on WheatImprovement 1981. CIMMYT,Mexico.14. Saari. E.E. 1979. Wheat in <strong>the</strong>developing countries from <strong>the</strong>Atlantic to <strong>the</strong> Pacific. InProceedings of <strong>the</strong> Symposia of <strong>the</strong>Ninth International Congress onPlant Protection, vol. II,T. Kommendahl, ed. Washington,D. C., USA.15. Srivastava, a.p., J.K. Luthra andP.N. Narula. 1971. Inheritance ofseedling resistance to leaf blight ofwheat. Indian Journal of GeneticPlant Breeding 31:209-211.

14416. Thurston, H.D. 1971. Relationshipof general resistance: Late blight ofpotato. Phytopathology 61:620-626.17. Tomerlin, J.R. M.A. EI-Morshidy.J.G. Moseman, P.S. Baenziger andG. Kimber. 1984. Resistance toErystphe gramtnts f. sp. trtttct,Pucctnta recondtta f. sp. trttict andSeptoria nodorum in wild Triticumspecies. Plant Disease 68(1):10-16.18. Vargo, RH., E.L. Stromnerg andJ.S. Baumer. 1981. The incidenceof leaf-spotting fungi associatedwith hard red spring wheat inMinnesota. In Proceedings of <strong>the</strong>Tan Spot of Wheat and RelatedDisease Workshop, RM. Hosford,ed. North Dakota State University,Fargo, North Dakota, USA.19. Wood, L.S. 1962. Relation ofvariation ih Helmtnthosporiumsattvum to seedling blight of smallgrains. Phytopathology 52:493-497.

Breeding Wheats with Resistanceto Helminthosporium sativum in ZambiaR. Raemaekers, Belgian Development Cooperation, Mount MakuluResearch Station, Chilanga, ZambiaAbstractThe Mexican wheat cultivars developed in <strong>the</strong> 1970s are unsuitableforproduction during <strong>the</strong> rainy season in Zambia, due to <strong>the</strong>ir susceptibility tofoliar diseases and head blight caused by H. sativum. Several sources ofresistance have now been detected in new germplasmfrom CIMMYT and inBrazilian wheats. Crosses are being made in Zambia to increase <strong>the</strong> level ofresistance and adaptation. Selected lines yield up to 3 Uha in tests, and <strong>the</strong>firstvariety has been released. The prospectfor rainfed wheat production withresistant cultivars is good.145Zambia has 6 million inhabitants, and alarge percentage of <strong>the</strong>m live in citiesand towns; <strong>the</strong> annual requirement forwheat is 180,000 tons. Approximately10% of this amount is produced locallyas irrigated wheat during <strong>the</strong> winter.Although a yield of 6 Uha is possibleand <strong>the</strong> wheat price is US$ 320/ton, <strong>the</strong>irrigated wheat area is not increasing.The participation of small-scale farmersin irrigated wheat production is difficultto envisage, but <strong>the</strong>y could participatein rainfed wheat production. wherelittle or no mechanization is reqUired.Rainfed wheat research and productionstarted in <strong>the</strong> mid-1970s; however.more emphasis was placed onproduction than on research. Thecultivars Jupateco and Sonora 64 wereused for commercial production. butwith very low, uneconomic yields,ranging from 0 to 800 kg/hat The majorreason for this failure was determinedto be <strong>the</strong> susceptibility of <strong>the</strong> wheatcultivars to diseases caused byHelminthosporium sativum.Natural epidemics of diseases caused byH. sativum start from <strong>the</strong> tilleringstage, and usually develop qUickly afterflowering; very susceptible lines may betotally necrotic by flowering. All abovegroundplant parts are attacked. Theoptimal conditions for development ofH. sativum are present in Zambiaduring <strong>the</strong> rainy season. Most locationsin <strong>the</strong> country can <strong>the</strong>refore beconsidered as hot spots for this disease.In crop loss assessment tests, it wasdemonstrated that total crop loss couldoccur if susceptible cultivars were used.In <strong>the</strong> same tests. it was alsodemonstrated that yields of more than3 Uha could be obtained with gooddisease control.Wheat cultivars with resistance toH. sativum had to be found, but nosuitable variety for Zambian conditionswas known to exist anywhere.Screening began with <strong>the</strong> support ofCIMMYT; <strong>the</strong> search for "<strong>the</strong> needle in<strong>the</strong> haystack" had started. Throughcontacts with Passo Fundo, <strong>the</strong> firstBrazilian lines arrived in Zambia in1979. Parts of <strong>the</strong> World Collectionwere also screened, and nurseries fromICARDA were tested.Very few sources of resistance werefound at first, when only advancedgeneration nurseries were tested.However, better materials weresubsequently found in <strong>the</strong> CIMMYT F2spring x winter populations and in <strong>the</strong>F2 nurseries for aluminum tolerance. Itis possible that an association existsbetween tolerance to aluminum toxicity

146and resistance to H. sativum. This mayexplain <strong>the</strong> resistance to H. sativumfound in <strong>the</strong> Brazilian lines.After several seasons of field tests withmany lines from abroad and localcrosses. all introductions are nowcompared with susceptible andresistant check varieties. and certainselection criteria are followed.Selections are made. based on foliarinfection. head blight, node infection.black point, maturity period. plan<strong>the</strong>ight. lodging tendency andagronomic characteristics. A single.best growth stage at which resistancecan be identified has not yet beendetermined. Observations in two orthree growth stages are still necessarybecause of fluctuations in diseasepressure. The critical period forinfection is <strong>the</strong> time between earlydough and maturity. Observationsduring flowering provide a goodindicator. but selections made beforeflowering are unreliable.Low percentages of flag leaf necrosisand head blight during <strong>the</strong> soft doughstage are good measurements ofresistance. It may be possible to expressnecrosis by spot type and lesionnumber. Entire spikelets of susceptiblelines are qUickly destroyed byH. sativum: restricted lesiondevelopment and few lesions on <strong>the</strong>spikes are required. Node infectionexpresses itself in stem-breaking atmaturity; 100% stem-break is oftenrecorded on susceptible cultivars likeJupateco.Grain infection varies considerably.even among resistant lines. Latematuringlines may escape infectionand are often wrongly selected asresistant. Therefore. it is necessary torelate infection level to growth stageand to make comparisons to checkcultivars. H. sativum may severelyattack lodged plants. probably due to<strong>the</strong> creation of a favorable microclimatefor disease development after lodging.Dwarf plants do not compete well withweeds. and <strong>the</strong>y risk exposure torelatively high disease pressure.The flag leaf size is ano<strong>the</strong>r criterionthat needs fur<strong>the</strong>r investigation. Largeflag leaves permit more inoculumproduction than smaller ones. andindirectly contribute to higher diseasepressure. Smaller leaves. in general.contribute to a microclimate which isless conducive to disease development.Good tillering provides an effectiveweed-control mechanism. and may alsobe an expression of tolerance toaluminum toxicity and heat.In yield tests in Zambia. H. sativumseverity is scored during flowering andin <strong>the</strong> soft dough stage on a 0 to 9scale. During flowering. <strong>the</strong> height atwhich <strong>the</strong> infection is found on <strong>the</strong>plant is recorded; during <strong>the</strong> soft doughstage. <strong>the</strong> flag leaf and <strong>the</strong> spike arescored; <strong>the</strong> infection is already high upon <strong>the</strong> plant by that time. A severityindex for black point will be included in<strong>the</strong> scoring system.The occurrence of o<strong>the</strong>r diseases. suchas X. campestris and Fusarium spp..complicates <strong>the</strong> scoring of H. sativum.Scoring at flowering is often madedifficult by <strong>the</strong> presence of lesions allover <strong>the</strong> foliage. Fluctuations in diseasepressure by sudden changes in wea<strong>the</strong>r

147conditions. whereby infectionpercentages change qUickly. complicate<strong>the</strong> comparison between varieties whichare in different growth stages. Underhigh disease pressure. <strong>the</strong> epidemicdevelops very quickly. and correctdeterminations of growth stages atscoring are necessary.The standardization of scoring methodsof H. sattvum would be beneficial for<strong>the</strong> development of resistant varieties.Presently. <strong>the</strong> situation is such thatinterpretation of information onH. sattvum from different countries isdifficult. Cultivars labeled resistant inone country may be very susceptible ino<strong>the</strong>r countries. and vice versa.The wheat germplasm with resistanceto H. sativum which is now being usedin Zambia originates from CIMMYTsegregating nurseries. from Brazil andfrom local Zambia crosses. In <strong>the</strong> springx winter wheat nurseries. some lineswere selected in <strong>the</strong> following crosses:Predg-NAC. Predg-Kavco. KVZ-Tanori.KVZ-HD2009/TOB-CNO x TOB-Era andKVZ/3/CC-INIAlICNOIEI Gaucho-Sonora64. Unfortunately. <strong>the</strong>se lines are notadaptated to acid soil conditions. In <strong>the</strong>spring x spring wheat nurseries (F2helminthosporium. F2 aluminumtolerance) several promising selectionshave been made. especially in <strong>the</strong>crosses with Brazilian wheats. Some of<strong>the</strong>se lines have good adaptation to acidsoil conditions as well. Lines from <strong>the</strong>following crosses are in various yieldtests: PEL73280-Atr(Tzpp x IRN46CN067/Protor).IAS64-Aldan"S",PF7339-Hahn"S." PF7339-Veery"S".IAS58-Chat"S", Hork x CNO-SieteCerros/IAS63. Kalyansona-Bluebird x Alondra"S"/Jacui andPF7339/Cndr-ANA x Cndr-Mustafa.Most of <strong>the</strong> older Brazilian wheats arelate maturing and very susceptible torust diseases under Zambianconditions. Some of <strong>the</strong> selectionswhich are presently in yield tests arePF7748,PF72640,B790I.B7903,88005. BR6 and Mascarenhas; <strong>the</strong>selines are also well-adapted to varioussoil conditions. From <strong>the</strong> localhybridization program. <strong>the</strong> best lineswhich are now in F7 originate from <strong>the</strong>following crosses: PF7748 x PEL73280Atr(Tzpp x IRN46-CN067/Protor),K4500 x Kalyansona-Alondra"S"1PF7748, PF72640 x PEL73280Atr(Tzpp x IRN46-CN067/Protor).Predg-NAC x PF7748, PF72640 xIAS64-Aldan"S". IAS64-Aldan"S" xPF7748 and PF7748/Predg-NAC xK4500.With an accelerated generationadvancementprogram. it is nowpossible in Zambia to develop andscreen relatively large numbers ofentries in a short period of time.Crosses are made in July and August,immediately after <strong>the</strong> rainy season. FIseed can be harvested as early as onemonth after pollination. due tofavorable environmental conditions.The FI is <strong>the</strong>n seeded duringSeptember and October, and F2 seedharvested in December. The F2 isseeded in early January in <strong>the</strong> rainyseason at one or more locations. Theselections are harvested in April andMay and reseeded under irrigation inMay and June. F4 seed is ready inOctober. in time for <strong>the</strong> rainy seasontests. Large populations from each. cross were space planted in <strong>the</strong>beginning, but it may be more efficient

148to make a large number of crosses andprescreen <strong>the</strong>m in a nursery as a bulk.after which intensive selection can beconducted in space-planted populationsof <strong>the</strong> best crosses.The wheat program has recentlyreleased <strong>the</strong> first rainfed wheat cultivar.Whydah. Its origin is <strong>the</strong> Brazilianselection PF7748 (ND811IAS591IIAS58).This variety requires four months fromseeding to harvest. It is tall. t1llersstrongly and has small spikes. Besidesbeing resistant to H. sativum. it is alsoresistant to Fusarium. X. campestrts.P. recondtta and P. gramtnts; it alsohas good tolerance to aluminumtoxicity. It is now used as <strong>the</strong> resistantcheck in <strong>the</strong> yield tests. along with <strong>the</strong>susceptible cultivar Jupateco. Itconstantly yields around 2 t1ha in yieldtests under various soil conditions anddifferent times of seeding. provided <strong>the</strong>rainy season lasts long enough. Thefirst commercial production took placedUring <strong>the</strong> 1983-84 season. with anaverage yield of 2.5 t1ha. The sameyields were also obtained with PF72640and Banu. but <strong>the</strong>se were not released.At present. several entries in <strong>the</strong> yieldtests have equal or better yields thanWhydah. Among <strong>the</strong>m are severalBrazilian lines and selections from <strong>the</strong>CIMMYT and Zambian crossesmentioned earlier. Some lines yield3 t1ha. However. official release not onlyrequires resistance to H. sativum. butalso to several o<strong>the</strong>r diseases. as well astolerance to aluminum toxicity. Thiscombination is not always present.Commercial rainfed wheat productionis now possible in Zambia. The farmingcommunity is becoming interested inthis new crop. Sufficient land forproduction is available. and 3 tlha andmore may be realized in <strong>the</strong> nearfuture.

149CIMMYT Methods for Screening Wheatfor Helminthosporium sativum ResistanceL.I. Gilchrist, Wheat Program, CIMMYT, MexicoAbstractHelminthosporium sativum is one of<strong>the</strong> most aggressive and virulent pathogensfound when breeding wheat in tropical climates. To screen for genetic resistanceat CIMMYT. seedlings at <strong>the</strong> two-leafstage are sprayed with inoculum in <strong>the</strong>greenhouse. and <strong>the</strong>n placed in a mist chamber; evaluationfor resistance ismade between <strong>the</strong>fifth and seventh day after inoculation. Selection underfieldconditions is accomplished in Poza Rica, where optimum environmentalconditionsfor <strong>the</strong> development ofH. sativum prevail. Usuallyfour to six readingsare taken offoliar damage, depending on <strong>the</strong> maturation of <strong>the</strong> lines beingtested. Grain damage is evaluatedfor severity. based on <strong>the</strong> percent ofinfectionofeach grain.Among <strong>the</strong> pathogens that moststrongly affect wheat yields in tropicalareas is Helminthosporium sattvum,which causes seedling blight, spotblotch and black point. One of <strong>the</strong>control methods that is beinginvestigated currently is <strong>the</strong> screeningof genetic material for desirableresistance levels. This paper presents<strong>the</strong> methodology used for selectinggenetic material from CIMMYT's breadwheat and wide cross programs undergreenhouse and field conditions.Handling Fungusin <strong>the</strong> LaboratoryPathogen isolationThe isolates are obtained from leaves ofdifferent wheat varieties and lines. In1984, various samples were taken atPoza Rica. The diseased leaves were cutinto small pieces, disinfected with 5 %calcium hypochlorite for 60 secondsand transferred to Petri dishes withpotato dextrose agar (PDA).Maintaining <strong>the</strong> isolatesThe isolates are maintained onsterilized wheat grain. To prepare <strong>the</strong>sterile grain media. <strong>the</strong> grains are firstsoaked in distilled water for 24 hours.Then <strong>the</strong> excess water is drained off,and <strong>the</strong> grain is sterilized in anautoclave at 120°C for two hours. Theisolates are kept in this media underrefrigeration (4°C) until reqUired.~oculuDlincreaseWhen an increase in <strong>the</strong> inoculum isdesired, <strong>the</strong> infected grains aretransferred to Petri dishes with PDAand kept in a growth chamber at 22 to24°C. After seven or eight days, <strong>the</strong>inoculum is ready for use.~oculuDlpreparationA spore suspension is prepared bywashing <strong>the</strong> PDA plates with distilledwater and filtering <strong>the</strong> spore suspensionthrough gauze. The spore concentrationis <strong>the</strong>n standarized to 60.000 sporesper/ml, using a hemocytometer.Inoculations underGreenhouse ConditionsPreparation of test DlaterialTen to twelve seeds of <strong>the</strong> materials tobe tested are placed in envelopes madefrom glassine bags lined with absorbentpaper towels. They are <strong>the</strong>n arranged intwo rows in 22 x 30 em trays withstrings to separate and support <strong>the</strong> 60envelopes. Each tray is <strong>the</strong>n filled withdistilled water, supplying <strong>the</strong> humidityneeded for germination and plantdevelopment.

150InoculationInoculation is done at <strong>the</strong> two-leafgrowth stage (about eight to ten daysafter germination). using a handsprayer. Each tray receivesapproximately 100 ml of inoculum.Inoculated plants are <strong>the</strong>n kept in amist chamber. with two hours ofcontinuous misting. and <strong>the</strong>n 15minutes of misting every two hours<strong>the</strong>reafter for 24 hours. Later. <strong>the</strong>seedlings are transferred into achamber and kept at 22° to 24°C and75 to 80% relative humidity for fivedays.Evaluation and selection of materialInoculated materials are evaluated afterfive to seven days. according to <strong>the</strong>follOWing I-to-5 scale:1 = a few small black lesions onleaves2 = more black lesions. some withsmall chlorotic halos3 = lesions surrounded by chlorotichalos. many of which startconverging; some drying effectsat leaf tips4 = broad lesions with amplenecrotic zones; drying over alarge part of <strong>the</strong> leaf5 = large lesions; drying of <strong>the</strong>whole leaf25 1 5 10 15 20 25 1 5 10Figure 1. Disease development on four late-maturing wheat varieties. fromfiowering to milk stage, January 25 to March 10, Poza Rica. Mexico,1983-848--"-...,.'.....•............":;;"'''.............. ,-'........

151Selection under Field ConditionsDUring <strong>the</strong> 1983-1984 cycle. conditionswere optimum fOT <strong>the</strong> d velopment ofH. sativum in Poza Rica. Relati ehumidity was recorded as between 90and 106% for more than 95 % of <strong>the</strong>gro ing cycle. This high relativehumidity resulted from dail earlymorning and afternoon fogs. with lessthan nve hours of direct sunlight perdaj r~corded during most of <strong>the</strong> cycle.The optimum average temperatur for<strong>the</strong> development of <strong>the</strong> fungus (18 to24 Q C) was also recorded duringapproximately 75% of <strong>the</strong> gro\ ingcycle. These conditions allowed goodselection pressure fOT <strong>the</strong> program.Four foliar evaluations were made for<strong>the</strong> early-maturing lines and six for tbelate-maturing materials. A 1 to 9 scalewas used for scoring. allowing <strong>the</strong>noting of more ariations in levels ofdisease presence.Figure 1 shows <strong>the</strong> d velopment of <strong>the</strong>disease on four late-maturing m.aterials.The advanoed lines Cook-Vec.ry"S" xDovc"S"-Veery"S" (PC236) and AIFong4-Yaco"S" x Tanager"S"·Pewee"S"(PC252) gave susceptibleresponses, while <strong>the</strong> lines F371-TRM(HTL2) and Yaco"S"-Phoebe"S"fCalidad-CHKW x Veery"S" Calidad-CHKW ~ Veery"S" (PC230) showed510\'\,1 development of <strong>the</strong> fung andhigh disease tolerance.Figure 2 shows <strong>the</strong> development of <strong>the</strong>disease on fOUT e..-u-ly-maturingmaterials. To-rim 73 and Cleopatrasho ed a susceptible response. LineAntbird"S"- aco"S" (PCI95j exhibitedslow development at <strong>the</strong> start. butreached a high level! of infection by <strong>the</strong>end of <strong>the</strong> c cleo Line Lir,a"S" (PC 1056)displayed good resislance. exhibiting alow level of infection during <strong>the</strong> entirecycle.In addition to field evaluation, 50 spikesof each selected line ere harvested atmaturity and <strong>the</strong> percentage of diseasedgrain and <strong>the</strong> severity of <strong>the</strong> damagewas evaluated. aCGording to a I-to-5scale (Figure 3). The best lines selectedat CThlMYT with tbis methodology arepresented in <strong>the</strong> paper by VilJarealet al. (<strong>the</strong>se proceedings).Reference1. CIMMYT. IntruclHms for <strong>the</strong>anagement and Reporting ofResults for Wheat ProgramInternational Yield and ScreeningNurseties. C1MMYT. Mexico. (Nodate.)Figure 3. One~to-fivescale used at CIMMYT for scoring severity of diseasedamage on wheat grains

152Insect Pests and Diseasesof Wheat in <strong>the</strong> PhilippinesD.B. Lapis, Institute for Plant Breeding, University of <strong>the</strong>Philippines, Los Baiios, PhilippinesAbstractFor <strong>the</strong> Philippines, producing wheat would be an ideal approachfor reducingwheat importation andfor savingforeign exchange. Insect pests and diseasesare two of <strong>the</strong> constraints to its production and to crop acceptability by <strong>the</strong>farmer. Based on observations in areas where wheat is being targetedforcommercial production, helminthosporium seems to be <strong>the</strong> most limitingfactorto producing wheat with desirable yield on a commercial scale;foot rots areobserved only occasionally and sporadically. Work on wheat pests has onlybegun in <strong>the</strong> Philippines; principal research efforts will be in breedingforresistant cultivars to control <strong>the</strong> pests and diseases ofprimary economicimportance.Although wheat was under cultivationin <strong>the</strong> Philippines as early as 1664,commercial production is still in itsinfancy. with only about 69 hectares ofcommercial production in <strong>the</strong> 1983cropping season. However, a great dealof wheat is consumed in <strong>the</strong>Philippines. In 1983, wheat importationamounted to about US$ 20 million.second only to petroleum. and thusconstituted a tremendous foreignexchange drain.Even though producing wheat would bean ideal approach for reducing wheatimportation and saving foreignexchange, <strong>the</strong>re are at presentconstraints which make wheat growingeconomically unfeasible. The crop does,however. offer promise for futureproduction. Insect pests and diseasesare two of <strong>the</strong> production constraintswhich limit its acceptance by <strong>the</strong>farmer.Wheat DiseasesThe two diseases of major importancein <strong>the</strong> Philippines are helminthosporiumleaf spot and foot rots. Leafspot is caused by Helminthosporiumsativum, and <strong>the</strong>re are several o<strong>the</strong>rreported helminthosporium species.Foot rots are caused by Sclerotiumrolfstt, Rhizoctonia solani, Fusariumroseum, Phythium spp., Phytophthoraspp. and H. sativum.Several species of Helminthosporiumare suspected of causing leaf spot, leafstripe and net blotch. which arepresently attacking wheat. It is obviousthat <strong>the</strong>y are caused by differentspecies, because of <strong>the</strong> observeddifferences in <strong>the</strong> characteristics of <strong>the</strong>lesions present on <strong>the</strong> diseased plants.The different root rot pathogens infectplants, ei<strong>the</strong>r alone or in combination.Based on observations made at <strong>the</strong>different areas where wheat is beingtargeted for commercial production. <strong>the</strong>disease caused by <strong>the</strong> Helminthosporiumspp. is believed to be <strong>the</strong> mostlimiting factor in <strong>the</strong> effort to producewheat with desirable yield on acommercial scale. Wheat in those areasis planted in November and December.so that <strong>the</strong> early vegetative stagecoincides with <strong>the</strong> cooler months(December and January). Previousobservations in <strong>the</strong> field have shownthat leaf spot is always present onwheat. but usually <strong>the</strong> disease becomessevere only at <strong>the</strong> later growth stages,between late January and late

153February. Environmental conditions areoften favorable for quicker and moresevere helminthosporium infectionwhen temperatures of 25 to 28°C andrelative humidity of 70 to 84% occurfrom January to March, coinciding with<strong>the</strong> critical stage of plant growth.Fur<strong>the</strong>r complicating <strong>the</strong> managementof <strong>the</strong> disease is <strong>the</strong> year-roundpresence of host plants ofhelminthosporium, including variousgrasses and broadleaf weeds, such asCommeltna diffusa, Chloris barbate,Dactyloctenium aegyptium, Eleusineindica, Cyperus difformis,C. fimbricatus, Imperata cyltndrica,Cynodon dactylon, Paspalumconjugatum, Leptochloa chinensis,Rottboellia exaltata, Brachiariadistachya, B. mutica and Echinochloacolona.Foot rots, although only occasionallyand sporadically observed in <strong>the</strong>different areas, are also considered ofimportance. The areas targeted forwheat are <strong>the</strong> rainfed areas, withinsufficient irrigation for a second ricecrop. Sclerotium and Rhizoctonia arecommon soil-borne pathogens, and <strong>the</strong>sclerotial bodies left in <strong>the</strong> field afterrice harvest serve as an inoculumsource for <strong>the</strong> wheat. The situation isfur<strong>the</strong>r aggravated by pre-sowingirrigation and <strong>the</strong> existence of hightemperatures and high relativehumidity, favoring germination of andinfection by <strong>the</strong>se soil-borne pathogens.O<strong>the</strong>r foot rot pathogens, such asspecies of Pythium and Phytopthora,are observed only occasionally; H.sativum is more common. It isprobably seed-borne, as indicated by<strong>the</strong> fact that 20 to 25% of <strong>the</strong> seedstaken from fields severely infected withhelminthosporium leaf spot show <strong>the</strong>presence of black point. This is fur<strong>the</strong>rsupported by a preliminary study inwhich seeds, previously disinfectedwith 1: 1000 mercuric bichloridesolution, soaked for five minutes in aspore suspension of H. sativum andplanted in sterile soil, gave only 30%germination; uninoculated seeds had92% germination. Those seedlings thatsurvived showed symptoms ofhelminthosporium five days afteremergence.To date, <strong>the</strong> only studies conducted onwheat diseases in <strong>the</strong> Philippines havebeen on <strong>the</strong> etiology of helminthosporiumleaf spot (1966), which wasidentified as Helminthosporiumsativum Pammel King and Bakke, andon head blight, which was identified asFusarium roseum (Cke) Snyder andHansen.Insect PestsThe principal insect pests on wheat in<strong>the</strong> Philippines are:• Seedling maggot - An<strong>the</strong>rigona spp.• Semilooper - Chrysodeixis chalcites• Pink stemborer - Sesamia inferens• Corn earworm . Helicoverpaarmigera• Aphids· Rhopalosiphum maidisCurrent observations indicate that <strong>the</strong>first four pests appear in succeSSionduring <strong>the</strong> cropping season.At present, no details on geneticresistance to <strong>the</strong> different wheat pestscan be given since work only started onJuly 1, 1984. The main research effortsin <strong>the</strong> Philippines will continue to be asearch for resistant cultivars, in order tocontrol those pests and diseases ofprimary economic importance.

154The Effect of Early Foliar Infectionby Helminthosporium sativum on SomeYield Components of Two African WheatsW.A.J. de Milliano, Wheat Program, CIMMYT, Mexico, andJ.C. Zadoks, Department of Phytopathology, State AgriculturalUniversity, Wageningen, Ne<strong>the</strong>rlandsAbstractEarlyfoliar infection by helminthosporium reduced <strong>the</strong> kernel dry weight perear oftwo African genotypes, in particular <strong>the</strong> number of kernels per ear.Reduction in kernels per ear was high at moderately high air temperature andhumidity, but moderate at high air temperatures and moderately highhumidity; under those conditions, yield was low anyway. Research is proposedfor studying yield loss due to earlyfoliar infection in <strong>the</strong>field. For areas withhigh air temperature and humidity, breedingfor tolerance to high temperaturesseems to demand a higher research priority than breedingfor helminthosporiumresistance. Genotypic variation apparently permits selectionfor incompleteresistance to helminthosporium.Foliar infection by helminthosporium(Helminthosporium sattvum Pammel,King and Bakke) of wheat (Triticumaestlvum L.) occurs in hot humid areas,for example, in parts of Africa and Asia(10), but also in cool humid areas (3.4).During <strong>the</strong> hot rainy season in Zambia,foliar infection of wheat can becomevery severe (6,7); in <strong>the</strong> cool, dryseason, however, severity remains low(1). The economic importance ofhelminthosporium is unknown formany areas (5,8,9,11). Crop-loss studieshave been performed in <strong>the</strong> field(Raemaekers, <strong>the</strong>se proceedings), where<strong>the</strong> effect of helminthosporium on yieldis confounded with o<strong>the</strong>r factors, suchas temperature, soil and interplotinterference. To study <strong>the</strong> effect ofhelminthosporium on yieldcomponents, trials were performedunder controlled conditions withartificial inoculation. Conditions in <strong>the</strong>growth chamber corresponded as muchas possible to field conditions in Zambiaand to o<strong>the</strong>r countries in <strong>the</strong> tropicalbelt.Materials and MethodsTwo trials were performed in a walk-ingrowth chamber at <strong>the</strong> Department ofPhytopathology of <strong>the</strong> StateAgricultural University, Wageningen,Ne<strong>the</strong>rlands. Trial 1, performed in1982, had high air temperature andmoderately high humidity (Table 1); inTrial 2, performed in 1983, both airtemperature and humidity weremoderately high (Table 2). A 12-hourday was used in 1982 and a 13-hourday in 1983; light intensity in bothtrials was moderate.In 1982, inoculations with helminthosporiumwere made before midflowering(mid-flowering = decimalcode (DC) 64) (13). In 1983, <strong>the</strong>y weremade before heading (heading = DC 50).The cultivars used were Tokwe andMIL04-21, short-cycle, early-maturingwheat genotypes. Tokwe is a dwarfcultivar for irrigated conditions (2,12),which is susceptible to helminthosporiumin <strong>the</strong> field. MIL04-21 is amedium-tall line from <strong>the</strong> HorizontalResistance Breeding Program (1); it hasmoderate susceptibility tohelminthosporium in <strong>the</strong> field andrelatively good yield in <strong>the</strong> warm rainyseason at Mazabuka, Zambia (15°45'Slatitude, 27°56'E longitude, 985 maltitude).

156Each trla1 had two replications with twoblocks for inoculation and twogenotypes randomized within <strong>the</strong>blocks for inoculation. The block forinoculation contained at least eight potswith two plants each. The 1982 trialwas harvested 104 days after <strong>the</strong> startof germination. and <strong>the</strong> 1983 trial after101, lOB. 115 and 122 days fromgermination. Kernels were dried atBOoC for 42 hours. and number ofkernels and dry weight of kernels perear were determined.ResultsIn Trial 1. kernel dry weight per ear of<strong>the</strong> first tiller was relatively low(Table 3). Foliar infection significantlyinfluenced kernel dry weight per ear.but genotypes differed in response. InTokwe. infection was lowest. with nodifference between inoculated anduninoculated plants. MlL04-21 had aloss of about 38%. due to a loss innumber of kernels and some loss inkernel dry weight.In T~ 2. kernel dry weight per ear of<strong>the</strong> first tiller was good in uninoculatedplants (Table 3). Foliar infectionsign1flcantly influenced kernel dryweight per ear. Tokwe. with <strong>the</strong> lowestvalue for untreated plants. had <strong>the</strong>highest loss in kernel dry weight perear. In both genotypes. loss in kernelTable 1. Climatic conditions used in growth chember trials to study <strong>the</strong> effect ofhelminthosporium on yield, Ne<strong>the</strong>rlands, 1982 and 1983ConditionTrial 1, 1982Light Darkneu(12 hr) (12 hr)Trial 2, 1983Light Darkness(13hr) (11hr)Air temperature (OC)at 70cmRelative humidity (0/0)Light intensity at planting(lux)2763(80)!t 124,5002080(96)!tl Figures in brackets = set value of growth chamber24(80)24,00018(90)Table 2. Regime followed for inoculating wheat with Helminthosporium sativumto study effect on yield, Ne<strong>the</strong>rlands, 1982 and 1983Inoculation regimeMeanSporeDays after development densityTrial germination stage (DC) (spores/m!)Trial 1 (1982)Inoculation 1 48 42 6xl()4Inoculation 2 51 45 1 x 105Inoculation 3 64 59 5 x lOSTrial 2 (1983)Inoculation 1 35 28 1 x 106Inoculation 2 40 36 1 x lOSInoculation 3 52 50 1 x lOS

156dry weight per ear was caused mainlyby a severe reduction in <strong>the</strong> number ofkernels per ear.ConclusionsEarly foliar infection byhelminthosporium reduced <strong>the</strong> kerneldry weight per ear of both Africangenotypes. Foliar infection betweendevelopment stages 30 and 50 DC of<strong>the</strong> plant inhibited kernel production.but did not appear to influence dryweight per kernel. Foliar infectionbetween development stages 40 and 65DC of <strong>the</strong> plant. however. could affectboth number of kernels per ear and dryweight per kernel. The results suggestthat <strong>the</strong> development stage at which<strong>the</strong> infection occurs is of importance for<strong>the</strong> number of kernels produced. Thedegree of inhibition was high.particularly at <strong>the</strong> moderately high airtemperature and humidity. Underirrigated conditions. as in Zambia.helminthosporium occurs on <strong>the</strong> leavesbefore an<strong>the</strong>sis; <strong>the</strong> experimentssuggest that helminthosporium may<strong>the</strong>n cause significant yield loss. Theamount of yield loss found in <strong>the</strong>seexperiments justifies yield loss studieswith fungicide applications beforean<strong>the</strong>sis. and screening for geneticvariation in resistance to earlyinfection.At high air temperatures andmoderately high humidity. <strong>the</strong> effect oftemperature on kernel dry weight perear was larger than was <strong>the</strong> effect ofhelminthosporium. This indicates that.in areas with high air temperature andhumidity, breeding for tolerance to hightemperature should have priority overbreeding for resistance tohelminthosporium.In both trials. kernel dry weight per eardiffered between genotypes; it washighest for MIL04-21. which wasselected under warm. rainy-seasonconditions in Zambia. Under thoseenvironmental conditions, MIL04-21had a higher yield than Tokwe. Geneticvariation appears to allow selection forincomplete resistance to helminthosporiumbut. Without good tolerance tohigh temperature. this resistance mayhave little practical value.AcknowledgementsThe authors wish to thank CIMMYT forproViding <strong>the</strong> opportunity forpresenting this paper. <strong>the</strong> Departmentof Phytopathology of <strong>the</strong> StateAgricultural University. Wageningen.Ne<strong>the</strong>rlands. for proViding <strong>the</strong> facilitiesto perform <strong>the</strong> trials. M. Kelfkens andM. Krot for carrying out <strong>the</strong> 1982 and1983 trials. respectively. and W.Hoogkamer for prOViding technicalassistance.Table 3. The effect of foliar infection by Helminthosporium sativum on yield componentsof first tillers for two African wheat genotypes grown in a growth chamber. Ne<strong>the</strong>rlands.1982 and 1983YieldcomponentTria/1,1982(genotype and effect)Effect ofEffect ofTokwe inoculatign!.' Mll04·21 inoculatio.,!.'Trial 2. 1983(genotype and effect)Effect ofEffect ofTokwe inoculation!' Ml104·21 inoculatio.,!.'Kernel dry weightper ear (g)No inoculation 0.14Inoculated 0.14 0Number of kernels HNo inoculation 5Inoculated 6Kernel dry weight (my)No inoculation 29Inoculated 25 .14!' Effect of inoculation =1.00-(+/-10.53 0.68 1.280.33 .38 0.25 .63 0.80 .3719 21 4315 .21 8 .62 28 .3528 35 3024 .14 35 0 30 0

157References1. De Milliano. W.A.J. 1983.Improvement of wheat in Zambiausing incomplete resistance againstrusts. PhD Thesis. StateAgricultural University.Wageningen. Ne<strong>the</strong>rlands.2. Edwards. LB. 1968. Release of newwheat varieties with high bakingqualities. Rhodesian AgriculturalJournal 65:55-57.3. Jorgensen. J. 1974. Occurrenceand importance of seed-borneinoculum of Cochliobolus sativuson barley seed in Denmark. ActaAgriculturae Scandinavica 24:4954.4. Mehta. Y.R 1978. Doencas do trigoe seu controle. Ed. AgronomicaCeres. Sao Paulo e SummaPhytopathologica 20:112-118.5. Peregrine. W.T.H.. and M.A.Siddiqi. 1972. A revised andannotated list of plant diseases inMalawi. Phytopathological Paper16. Commonwealth MycologicalInstitute. Kew. England.6. Raemaekers. RN. 1978. Diseasesituation on rainfed wheat 1977-78in Zambia. In Wheat DiseaseWorkshop. Zambia. ZAM-CANWheat Development Project,Lusaka. Zambia. Pp. 22-26.8. Rieuf. P. 1971. Parasites etsaprofytes des plantes au Maroc.Cahiers Recherche Agronomique30:469-570.9. Riley. E.A. 1960. A revised list ofplant diseases in Tanganyikaterritory. Mycological Paper 75.Commonwealth MycologicalInstitute. Kew. England.10. Saari, E.E.. and RD. Wilcoxson.1974. Plant disease situation ofhigh-yielding dwarf wheats in Asiaand Africa. Annual Review ofPhytopathology 12:49-68.11. Thorold. M.A. 1935. Diseases ofcereal crops in Kenya colony.Department of Agriculture Bulletin2. Colony and Protectorate ofKenya. Nairobi. Kenya.12. Waterhouse. RG.F. 1976. Adescription of old and new wheatvarieties. Department ofAgriculture. NIRS. Mazabuka.Zambia.13. Zadoks. J.C.. T.T. Chang and C.F.Konzak. 1974. A decimal code forgrowth stages of cereals. EucarpiaBulletin 7.7. Raemaekers. RN. 1981. Plantpathology report: Rainfed wheat1980-81. In Annual Report 198081. Plant Protection Section. MountMakulu Research Station. Chilanga.Zambia.

158Wheat Breeding for Scab ResistanceG.C. Luzzardi, Faculdade de Agronomia Eliseu Maciel,Universidade Federal de Pelotas, Pelotas, BrazilAbstractScab or head. blight of wheat caused by Gibberella zeae (Fusarium graminearum)is an important yield-limitingfoctor in tropicaUsubtropical regions; <strong>the</strong> maindamage occurs as shriveling ofgrain andflower abortion. Immunity has notbeen reported. but some Asian cultivars have shown stable and transmissibleresistance. Selections in segregating material should be done at locations with ahigh natural disease incidence and/or by using measures to increase diseasespread. such as artiflcial inoculum production and inoculations. Changes inseeding date. sprinkler irrigation. rotation with corn or <strong>the</strong> use ofsusceptibleborders should be utilized to enhance <strong>the</strong> epidemic. The most reliable methodsof disease assessment must be used to determine <strong>the</strong> percentage ofshriveledkernels and offlower abortion. In this paper are presented aspects of inoculumproduction. inoculation methods. environmental conditions whichfocilitatetesting. identiflcation of resistance and breedingfor scab resistance.Scab or head blight. caused byGibberella zeae (Schw.) Petch. withFusarium graminearum Schw. as ananamorph. is an important factorlimiting wheat yields. especially inareas having mild winters and warm.humid springs. These conditionsfrequently occur during <strong>the</strong> winterwheat season in <strong>the</strong> Sou<strong>the</strong>rn Cone ofSouth America. sou<strong>the</strong>rn Africa.Australia. eastern and western Europeand North America (5.6,10.13,30,33.34.71.73).The main damage occurs as kernelshriveling and floret abortion due toinfections of <strong>the</strong> an<strong>the</strong>rs and ovaries,but F. graminearum is capable ofattacking <strong>the</strong> whole wheat plant(10,13.24.30.34.48.67). F. graminearumsurvives from one season toano<strong>the</strong>r as mycelia. conidia and/orascospores in <strong>the</strong> soil. on crop debrisand on seeds. Infections in o<strong>the</strong>r hosts.such as barley. com. oats. rice. rye.sorghum and grasses. e.g.• species ofAlopecurus. Agropyron. Bromus.Digitaria. Echinochloa. Lolium andPoa. may also be important inoculumsources (3.5.7.10.13.24.30.34.48).The variability within F. graminearumis high. at least in culturalcharacteristics (11.48.55.70). andimmunity to head scab has not beenreported in wheat. However. lines withhigh levels of resistance have beenfound. especially among material fromChina. Japan and sou<strong>the</strong>rn Brazil(23.30.34.50.58). Unfortunately. <strong>the</strong>sesources usually have poor agronomictype.The nature of resistance to scab is notcompletely understood. Schroeder andChristensen (56.57) observed twodifferent types. resistance to initialinfection and resistance to spreadwithin <strong>the</strong> spike. The resistance toinitial infection might be related to <strong>the</strong>opening of <strong>the</strong> floret for a shorter time(Nakagawa. personal communication).and to not trapping an<strong>the</strong>rs when <strong>the</strong>glumes close (48.51,60.61,62.63.64.66).as well as to o<strong>the</strong>r factors. Theresistance to disease spread within <strong>the</strong>spike is probably of a biochemicalnature. and Nakagawa has tried tocorrelate it with sugar and phosphoruslevel (38.39.40.41.42).Although differences in <strong>the</strong> level ofresistance have been observed in bothBrazil and Japan (such as in

159Shinchunaga and descendants). severalmaterials have shown good resistanceover all localities during <strong>the</strong> fewdecades that <strong>the</strong>y have been tested (29).This fact has encouraged breeders andpathologists to attempt <strong>the</strong> difficult taskof breeding for resistance to a diseasecaused by a pathogen with a highvariability. high rate of multiplication.various means of dispersion andsurvival in <strong>the</strong> absence of <strong>the</strong> host.Breeding programs for scab resistanceare in progress now in China. Japanand Brazil. In order to select forresistance to scab. methodologies toassure <strong>the</strong> occurrence of <strong>the</strong> diseaseand to evaluate resistance are essential.Artificial InoculationInoculum productionSeveral culture media can be used toisolate and increase inoculum ofF. graminearum (7.72). Pieces of cornstalk with nodes. autoclaved with asmall amount of water (25). constitutean inexpensive media that produceshigh amounts of conidia and/orascospores. and allows several harvestsof inoculum; this method is now in usein Brazil. Cultures grown at 25°Cunder continuous flourescent light givegood production of conidia. Ascosporesare produced by some isolates keptunder natural conditions.Inoculation methodsSprays of a suspension of mycelia.conidia and/or ascospores are similarlyeffective in inducing disease whenenvironmental conditions are favorable(48.66.67.68.69). The concentration ofspores in successful inoculationsreported varies from 4 x ~03 to 8 x 106conidia/ml (1.14.55.56.72). In <strong>the</strong> testsconducted in Brazil. a spore suspensionwith 106 conidia/ml is applied. underboth field and greenhouse conditions.with a conventional sprayer.spread within <strong>the</strong> spike. As <strong>the</strong> mostdamaging infections occur betweenan<strong>the</strong>sis and <strong>the</strong> milk stage. I.e.. <strong>the</strong>period of highest susceptibility (1.2.8.10.11.12.34.54). <strong>the</strong> inoculation shouldbe made at flowering or a little later. InBrazil. mixtures of fifty or more isolatesfrom different localities are normallyused. in order to assure a pathogenicpopulation representative of <strong>the</strong> onethat occurs naturally in <strong>the</strong> field.Environmental conditionsIn greenhouses with temperaturesaround 25°C and relative humidityover 85% dUring <strong>the</strong> inoculation period(flowering to milk stage). <strong>the</strong>development of scab is very good. InPelotas. a marginal region for wheatproduction in Brazil. <strong>the</strong> warm. Windy.humid spring wea<strong>the</strong>r provides naturalconditions for a high incidence of <strong>the</strong>disease in <strong>the</strong> field almost every year.as can be seen in Table 1.Table 1. Natural occurrence of scab in wheatplots under field conditions, Pelotas,Brazil, 1979CultivarAburaInayamaNobeoka BozuNyu BayPekin 8ToropiPEL73007PEL73022PEL73157PEL73175FB5163JaralSuper XPV·lndusScabbed grains(0/0)19.652.073.986.3910.188.1823.2020.405.5116.2093.3381.8191.1795.28Injections of spore suspensions (300 to400 conidia per drop) in a central floretare very useful for testing resistance to

160In localities where scab occurs onlysporadically. several arrangements canbe made in order to increase <strong>the</strong>possibility of <strong>the</strong> uniform occurrence of<strong>the</strong> disease. These include changes inseeding date to make flowering coincidewith <strong>the</strong> period of higher humidity. <strong>the</strong>use of sprinkler irrigation. crop rotationwith corn. leaving corn stubble withinand around plots. <strong>the</strong> use of highlysusceptible borders (triticale. durumwheat. rye and some wheat varieties).and leaving inoculated or naturallyinfected wheat or corn straw along <strong>the</strong>edges of <strong>the</strong> plots (3.4.24.43.46.47.65.74.75).Identification of resistant plantsSince <strong>the</strong> main damage caused by scabis kernel shriveling and floret abortion.<strong>the</strong> most reliable method for diseaseassessment must involve <strong>the</strong>se twoparameters. Individual threshing ofspikes (or a known number of spikes)and counting shriveled and healthygrains is necessary. The number ofplump kernels per head. grown underconditions of high scab incidence,Table 2. Modified Japanese scale for scabresistance, according to percent ofscabbed grainScale Scabbed grains Resistance level(010)o12345oLess than 89-1112-2021-50More than 50Completely resistantResistantModerately resistantModerately susceptibleSusceptibleHighly susceptiblecompared with <strong>the</strong> normal number ofplump kernels per head under healthyconditions is <strong>the</strong> best indication of <strong>the</strong>degree of resistance or susceptibility ofa cultivar. With segregating materials.since a healthy check is not possible. anestimate of <strong>the</strong> number of kernels perhead. based on spike size. is necessary(Table 2).The percentage of damaged grainsalone. overlooking flower abortion. hasbeen used in several programs (7.8.9.14.16.28.37.72). and has proven usefulin most routine screening work. Visualgrading of kernels for plumpness andshriveling is also used. Wheneverresistance scoring through kernelobservation is employed. threshingshould be done by hand or with athresher without forced ventilation.since shriveled grains tend to beeliminated in normal threshing.Observation of symptoms in heads canalso be made in preliminary selections(37). always watching out for thosecases where glume symptoms are notcorrelated with grain infections (28).The score for a plant should be <strong>the</strong>score of <strong>the</strong> most infected head(Table 3).Table 3. Modified Japanese scale for scabresistance, according to head symptomsScaleNecrotic areaof head (0/0)o 01 1-52 5·253 25-504 50-755 More than 75Resistance levelCompletely resistantResistantModerately resistantModerately susceptibleSusceptibleHighly susceptible

161Wheat Breedingfor Scab ResistanceThe main sources of resistance to scabused in <strong>the</strong> Brazilian breedingprograms are descendants of Asiancultivars. such as Nobeoka Bozu.Pekin 8. Nyu Bay. Minami Kyushu 69.Abura. Inayama. Tokai 66 and o<strong>the</strong>rs(7,9.14.15.16.17.18.19.20.21.22,32.35.36.44.45.52.53). Local cultivars.especially Toropi and Encruzilhada. arealso being used because. even though<strong>the</strong>y are moderately susceptible ingreenhouse tests. <strong>the</strong>y show someresistance under field conditions(26.27.28.31.59).Crosses followed by genealogicalselection have been used in attempts tocombine resistance to scab with o<strong>the</strong>rtraits of local interest. such as yield.quality and resistance to o<strong>the</strong>r diseases.The EMBRAPA National WheatResearch Center at Passo Fundo has aspecial program for transferringresistance to scab. via back crosses, toseveral cultivars of good agronomictype (49).Selection for scab resistance shouldstart with a preliminary selection of F2plants or. if entries are to be testedunder heavy inoculum in <strong>the</strong> field orgreenhouse. in <strong>the</strong> F3 and/or F4generations. According to Nakagawa(personal communication). selection in<strong>the</strong> F4 and F5 generations are moreeffective. In localities where scab doesnot occur every year. testing should berepeated over several generations untilreliable data can be obtained.Table 4 presents <strong>the</strong> percentage ofscabbed (shriveled) kernels ofsusceptible and resistant cultivars andTable 4. Percentage of scabbed kernels of various resistant and susceptible cultivars andcrosses after greenhouse inoculations, Pelotas, BrazilCu Itivar or crossGenerationScabbed kernels (°/0)Cultivars.!!f Selected plantsNyu BayNyu Bay x Lagoa VermeinaLagoa VermelhaIAS54IAS54 x Nobeoka BozuNobeoka BozuToropi x Nobeoka BozuToropiIAS20 x ToropiIAS20~I 5-year average9.353.770.210.832.050.315.786.8, 5.0,4.7,8.0,7.3,12.5,11.1,8.7,16.8, 7.9, 9.1, 15.4,8.8,10.86.6,7.1,7.4,10.1,8.6,4.5,9.0,8.322.6

182<strong>the</strong>ir descendents after tests in <strong>the</strong>greenhouse. with relative humidity keptover 90% by automatic mist. Theplants were given two inoculations perweek. from flowering to maturation. ofa spore suspension comprising over 70isolates (29).Table 5 presents <strong>the</strong> number ofresistant plants selected under severegreenhouse tests. These were derivedfrom F3 and F4 populations. fromcrosses involving more than oneresistance source (53).Table 6. Number of reliltant plants from segregating populationlsubjected to greenhousescab inoculationl, Pelotal, BrazilCrollNumber of plantsPopulation SelectedToropi-Nobeoka Bozu x Abura-Siete CerrosIAS52-Toropi x Avanzado Ecuador L 17-Nobeoka Bozu(lAS 49-Minami Kyushu 69 x IAS49·IAS20) xlAS 54-Nobeoka BozuAbura·Mazoe (Gabo) x IAS54·Nobeoka BozuNobeoka Bozu·IAS54 Sel21 x PF7225Lagoa Vermelha·Nobeoka BOlU x PF6968IAS20·Toropi x Nyu Bay-Nadadores 63Pekin 8 x IAS50-5heridan/1 AS2o-PE L8685-62 xIAS20-Tokai 66Several o<strong>the</strong>r crosses1142682862961762241161288234087109355

163References1. Andersen. A.L. 1948. Thedevelopment of Gibberella zeaehead blight of wheat.Phytopathology 38(8):595.611.2. Atanasoff. D. 1920. Fusarium blight(scab) of wheat and o<strong>the</strong>r cereals.Journal of Agricultural Research20(1):1-2.3. Bruehl. G.W. 1967. Fungal spike orkernel blights: Fusarium headblight or scab. In Wheat and WheatImprovement. K.S. Quisenberry. edtAmerican Society of Agronomy.Madison. Wisconsin. USA. Pp. 388390.4. Caetano. Vanderlei R.. VesleiCaetano. G.C. Luzzardi. C.R.Pierobom and F.I. Ferreira. 1976.Factores fitosanitartos a considerarno melhoramento do trigo. no suIdo Brasil. In VIII Reuniao AnualConjunta de Pesquisa de Trigo.CNPTrigo. vol. 4. Pp. 209-260.5. Carranza. J.M. 1961. Podredumbrey tiz6n de los cereales en laArgentina. producida porGibberella zeae (Fusariumgraminearum). Revista de laFacultad de Agronomia (La Plata.Argentina) 37:33-73.6. CIMMYT. 1983. Common Diseasesof Small Grain Cereals: A Guide toIdentification. F.J. Zillinsky.CIMMYT. Mexico.7. Chauvie. S.B.. and E.P. Morales.1981. Comportamiento de distintoscultivares de trigo frente aFusarium graminearum Schw..agente causal del ..golpe blanco."Thesis. Facultad de Agronomia.Universidad de la Republica.Ministerio de Educacion y Cultura.Montevideo. Uruguay.8. Christensen. J.J.. E.C. Stakmanand F.R. Immer. 1929.Susceptibility of wheat varietiesand hybrids to fusarial head blightin Minnesota. MinnesotaAgricultural Experiment StationTechnical Bulletin 59. St. Paul.Minnesota. USA.9. Dias. J.C.A.. G.C. Luzzardi,E.A. Osorio. P.G. Souza. C.R.Pierobom and J.C.S. Moreira. 1975.Graduacao de cultivares de trigo asdoencas septoria das glumas egiberela. In VII Reuniao AnualConjunta de Pesquisa de Trigo.Passo Fundo. Brazil. (Mimeograph.)10. Dickson. J.G. 1956. Diseases ofField Crops. 2nd edt McGraw Hill.New York. Toronto. London.11. Eide. C.J. 1953. The pathogenicityand genetics of Gibberellasaubinettl (Mont.) Sacco Universityof Minnesota AgriculturalExperiment Station Bulletin 106.St. Paul. Minnesota. USA.12. Eugenio. C.P.• C.M. Christensenand C.J. Mirocha. 1970. Factorsaffecting production of <strong>the</strong>mycotoxin F-2 by Fusariumroseum. Phytopathology 60:10551057.13. Fernandez Valiela. M. 1978.Introducion a la Fitopatologia. 3rdedt Coleccion Cientifica INTA.vol. 3. Buenos Aires. Argentina.14. Fulco. W. da S. 1971. Pesquisa defontes de resistencia a Gibberellazeae (Schw.) Petch. AgronomiaSulriograndense (Brazil) 7(1):31-34.

18415. FUlco. W. da S. 1980. Resistenciade linhagem de trigo emexpelimentacao no Rio Grande doSuI a Gtbberella zeae (Schw.)Petch. Helmtnthosportum sattvumP.K.B. e a Erystphe gramtnts trtttctD.C. no ano de 1979. In XI ReuniaoNacional de Pesquisa de Trigo.Porto Alegre. Brazil.16. Gocho, H.• T. Kawaide. K. Nishio. S.Watanabe and M. Nakagawa. 1971.Evaluation for <strong>the</strong> varietalresistance of wheat to fusarial headblight (Gtbberella zeae (Schw.)Petch) tested at different locationsand seasons. Tokai-KinkiAgricultural Experiment StationBulletin 21 (1). Japan.17. Gocho. H.• and T. Hirai. 1977.Feasibility of selection for resistanceto Gtbberella zeae (Schw.) Petch inearly generation of wheat breedingprogram. Tokai-Kinki AgriculturalExperiment Station Bulletin 27(2).Japan.18. Gocho, H.. T. Hirai and T. Kashio.1978. Relation between scabresistance and each of twenty-twoagronomical. morphological andphysiological characteristics inwheat. Tokai-Kinki AgriculturalExperiment Station Bulletin 28(2).Japan.19. Gocho. H.. T. Hirai and T. Kahio.1979. Heterosis of scab resistancein wheat. Tokai-Kinki AgriculturalExperiment Station Bulletin 29(1).Japan.20. Gocho. H.. H. Namitome. T. Hirai.A. Eguchi. H. Saito and T. Kashio.1980. Effectiveness of selection ofearliness and scab resistance to <strong>the</strong>population derived from gammairradiated wheat varietyGogatsukomugt. Tokai-KinkiAgricultural Experiment StationBulletin 30(2). Japan.21. Gocho. H.• T. Hirai and T. Kashio.1981. Feasibility of individualselection for resistance toGtbberella zeae (Schw.) Petch inlater generations of wheat breedingprogram. Kyushu AgriculturalResearch Station Bulletin 43(7).Japan.22. Gocho. H.. T. Hirai and T. Kashio.1982. Result of selection of scabresistance to lines derived fromgamma irradiated wheat varietyNobeoka Bozu Komugi. Tokat-KinkiAgricultural Experiment StationBulletin 32(1). Japan.23. Hanson. E.F.• E.R. Ausmus andE.C. Stakman. 1950. Varietalresistance of spring wheats tofusaria! head blight.Phytopathology 40:902-914.24. Ishii, H. 1961. Studies on <strong>the</strong>epidemiology of scab disease ofwheat and barley caused byGibberella zeae (Schw.) Petch.Tokushima AgriculturalExperiment Station Special Report3. Tokushima. Japan.25. Luzzardi. G.C.. M.V.S. Wetzel andC.R. Pierobom. 1972. Meio decultura para multiplicacao deGtbberella zeae (Schw.) PetchFusartum gramtnearum Schw..agente da giberela do trigo. Revistada Sociedade Brasileira deFitopatologia 5: 182-183. (Abstract.)

16526. Luzzardi. G.C.. C.R. Pierobom.E.A. Osorio. J.C.S. Moreira andM.V.S. Wetzel. 1973. Resistencia decultivares de trigo a Gtbberellazeae (Schw.) Petch = Fusartumgramtnearum Schw. Fitopatologia(ALF) 8:13. (Abstract.)27. Luzzardi, G.C.• C.R. Pierobom.E.A. Osorio, J.C.S. Moreira. M.V.S.Wetzel and J.C.A. Dias. 1974.Resistencia de cultivares de trigo agiberela. VI Reuniao AnualConjunta de Pesquisa de Trigo.Porto Alegre, Brazil. (Mimeograph.)28. Luzzardi. G.C., C.R. Pierobom.E.A. Osorio, J.C.S. Moreira. M.V.S.Wetzel and J.C.A. Dias. 1974.Melhoramento de trtgo pararesistencia a giberela. Anais da IReuniao Latinoamericana de Trigo.Porto Alegre. Brazil. Pp. 117-121.29. Luzzardi. G.C.• C.R. Pierobom.E.A. Osorio, J.C.S. Moreira. M.V.S.Wetzel and J.C.A. Dias. 1974.Comparacao entre progenies ecultivares de trigo, para resistenciaa giberela. mantidas em condicoesde estufa e sob constantesinoculacoes artificiais. VI ReuniaoAnual Conjunta de Pesquisa deTrigo. Porto Alegre. Brazil.(Mimeograph.)30. Luzzardi. G.C.. and C.R. Pierobom.1975. Molestias do trtgo na regiaosuI do Brasil. EMBRAPA Circular42. Representacao Estadual. RioGrande do SuI. Brazil.31. Luzzardi. G.C., C.R. Pierobom,E.A. Osorio. J.C.S. Moreira, M.V.S.Wetzel and J.C.A. Dias. 1975.Wheat breeding for resistance toGtbberella zeae (Schw.) Petch.Annual Wheat Newsletter (KansasState University and CanadaDepartment of Agriculture)21(1):53.32. Luzzardi, G.C., C.R. Pierobom.E.A. Osorio and J .C.S. Moreira.1976. Reacao de cultivares de trigoa giberela. em casa de vegetacao.nos anos de 1971 a 1975. VIIIReuniao Anual Conjunta dePesquisa de Trigo, Ponta Grossa.Brazil. (Mimeograph.)33. Macinnes. J .• and R. Fogelman.1923. Wheat scab in Minnesota.University of MinnesotaAgricultural Experiment StationTechnical Bulletin 18. St. Paul.Minnesota. USA.34. Mehta. Y. 1978. Doencas do trigo eseu controle. Ed. Agronomica CeresLtda. e Summa Phytopathologica.Sao Paulo. Brazil.35. Nakagawa. M. 1951. Studies on earscab resistance on wheat. TokaiKinki National Experiment StationBulletin 1. Japan.36. Nakagawa. M. 1956. Studies on <strong>the</strong>resistance of wheat varieties toGtbberella saubtnett: I. Geneticalfactors affecting susceptibility toGtbberella saubtnettt of wheatvarieties. Division of Plant Breedingand Cultivation. Tokai-KinkiNational Agricultural ExperimentStation Bulletin 3. Japan.37. Nakagawa. M. 1956. Studies on <strong>the</strong>resistance of wheat varieties toGtbberella saubtnettl: II. Relationof <strong>the</strong> variety-testing and <strong>the</strong> seedreaction to fusarial head blight(Gtbberella saubtnettt) in wheatvarieties. Division of Plant Breedingand Cultivation. Tokai-KinkiNational Agruicultural ExperimentStation Bulletin 3. Japan.

16638. Nakagawa. M. 1957. Studies on <strong>the</strong>resistance of wheat varieties toGibberella saubinetti: III. Alcoholfermentation by Fusartumfungus.Division of Plant Breeding andCultivation. Tokai-Kinki NationalAgricultural Experiment StationBulletin 4. Japan.39. Nakagawa. M. 1957. Studies on <strong>the</strong>resistance of wheat varieties toGibberella saubtnetti: IV. Therelation of <strong>the</strong> susceptibility to earscab and <strong>the</strong> potassium chlorate(KC 1°3) reaction and <strong>the</strong> amount offructose contents. Division of PlantBreeding and Cultivation. TokaiKinki National AgriculturalExperiment Station Bulletin 4.Japan.40. Nakagawa. M. 1957. Studies on <strong>the</strong>resistance of wheat varieties toGibberella saubinetti: V. Relationof <strong>the</strong> susceptibility to ear scab and<strong>the</strong> decolorization velocity of <strong>the</strong>methylene blue and amount ofglucose on wheat. Division of PlantBreeding and Cultivation. TokaiKinki National AgriculturalExperiment Station Bulletin 4.Japan.41. Nakagawa. M. 1957. Studies on <strong>the</strong>resistance of wheat varieties toGibberella saubinetti: VI. Relationof <strong>the</strong> susceptibility to ear scab andphosphorus content. Division ofPlant Breeding and Cultivation.Tokai-Kinki National AgriculturalExperiment Station Bulletin 4.Japan.42. Nakagawa. M. 1957. Studies on <strong>the</strong>resistance of wheat varieties toGibberella saubinetti: VII.Relations among <strong>the</strong> geneticalfactors. susceptible substances andcorresponding enzymes as to earscab on wheat plant. Division ofPlant Breeding and Cultivation.Tokai-Kinki National AgriculturalExperiment Station Bulletin 4.Japan.43. Nakagawa. M. 1960. Studies on <strong>the</strong>resistance of wheat varieties toGibberella saubinetti regarding<strong>the</strong>ir genetical characters andenvironmental factors. FirstAgronomy Division. Tokai-KinkiNational Agricultural ExperimentStation Bulletin 7. Japan.44. Nakagawa. M.• H. Gocho. K. Nishioand S. Watanabe. 1966. Nature andinheritance of ear scab resistance inwheat. Heritability estimates andheritable relationships of ear-scabresistance and some agronomiccharacters in F2 of <strong>the</strong> crossSchinchunaga x Nori 12. TokaiKinki National AgriculturalExperiment Station Bulletin 15.Japan.45. Nakagawa. M .• Y. Saga.Watanabe. H. Gocho. K. Nishio andH. Kurata. 1959. Practicalutilization of genetical studies on<strong>the</strong> resistance to Gibberellasaubinetti on wheat. FirstAgronomy Division, Tokai-KinkiNational Agricultural ExperimentStation Bulletin 6. Japan.46. Nakagawa. M .• S. Watanabe.H. Gocho and K. Nishio. 1956.Studies on <strong>the</strong> occurrence forecastof Gibberella zeae on wheatvarieties caused by climatic factors.Tokai-Kinki National AgriculturalExperiment Station Bulletin 15.Japan.47. Nakagawa. M .• S. Watanabe. H.Gocho and K. Nishio. 1966. Studieson <strong>the</strong> occurrence forecast ofGibberella zeae on wheat varietiescaused by climatic factors. TokaiKinki National AgriculturalExperiment Station Bulletin 15:5567.

18748. Nisikado. Y. 1958. Studies on <strong>the</strong>wheat scab. caused by Gtbberellazeae (Schw.) Petch. and its control.Ohara Institute of AgricultureBiology. Okayama University.Japan.49. Osorio. E.A. 1976. Importancia davariedade na cultura do trigo.Agroquimica 3:4-9.50. Osorio. E.A.. G.C. Luzzardi andJ.C.S. Moreira. 1973. Breeding forresistance to Septorta nodorumBerk. and Gtbberella zeae (Schw.)Petch in Brazil. Annual WheatNewsletter (Kansas State Universityand Canada Department ofAgriculture) 19:28-29.51. Pearce. RB.• RN. Strange and H.Smith. 1976. Glycinebetaine andcholine in wheat: distribution andrelation to infection by Fusariumgramtnearum. Phytochemistry15(6):953-954.52. Pierobom. C.R 1978. Avaliacao deresistencia de cultivares de trigo agiberela. In X Reuniao AnualConjunta de Pesquisa de Trigo.CNPTrigo. vol. 2. Pp. 120-125.53. Pierobom. C.R. G.C. Luzzardi.J.C.S. Moreira. E. Minella andW.C. Luz. 1976. Selecao delinhagens de trigo resistentes agiberela em casa de vegetacao. InVIII Reuniao Anual Conjunta dePesquisa de Trigo. CNPTrigo. vol.4. Pp. 48-50.54. Pugh. G.H.• H.Y. Jahon andJ.G. Dickson. 1933. Factorsaffecting infection to wheat headsby Gtbberella saubtnettt. Journalof Agricultural Research 46(9): 771797.56. Schroeder. H.W. 1955. Factorsaffecting resistance of wheat to scabcaused by Gibberella zeae (Schw.)Petch. PhD Thesis. University ofMinnesota. St. Paul, Minnesota.USA.57. Schroeder. H.W.. andJ.J. Christensen. 1963. Factorsaffecting resistance of wheat to scabcaused by Gibberella zeae.Phytopathology 53:831-838.58. Silva. A.R 1966. Melhoramento dasvariedades de trigo destinadas asdiferentes regioes do Brasil. SIAEstudios Tecnicos 33.59. Sousa. C.N.A. de. and J.A. delDuca. 1982. General breedingprogram. Annual Wheat Newsletter(Kansas State University andCanada Department of Agriculture)28:41-42.60. Strange. RN.. and H. Smith. 1971.A fungal growth stimulant inan<strong>the</strong>rs which predisposes wheat toattack by Fusarium graminearum.Physiological Plant Pathology1:141-150.61. Strange. RN.• H. Smith andJ.R Majer. 1972. Choline. one oftwo fungal growth stimulants inan<strong>the</strong>rs responsible for <strong>the</strong>susceptibility of wheat to Fusariumgraminearum. Nature (London)238:103-104.62. Strange. RN.• J.R Majer andH. Smith. 1974. The isolation andidentification of choline and betaineas two major components inan<strong>the</strong>rs and wheat germ thatstimulate Fusarium graminearumin vitro. Physiological PlantPathology 4(2):277-290.55. Purss. G.S. 1971. Pathogenicspecialization in Fusartumgraminearum. Australian Journalof Agricultural Research 22(4):553561.

16863. Strange. RN.. A. Deramo andH. Smith. 1978. Virulenceenhancement of Fusariumgraminearum by choline andbetaine and of Botrytis cinerea byo<strong>the</strong>r constituents of wheat germ.Transactions of <strong>the</strong> BritishMycological Society 70:201·207.64. Strange. RN.. and H. Smith. 1978.Specifity of choline and betaine asstimulants of Fusariumgraminearum. Transactions of <strong>the</strong>British Mycological Society 70:187192.65. Sutton. J.C. 1982. Epidemiology ofwheat head blight and maize earrot caused by Fusariumgraminearum. Canadian Journal ofPlant Pathology 4: 195-205.66. Takegami. S. 1957. Studies on <strong>the</strong>resistance of wheat varieties toGibberella zeae (SChw.) Petch.(head blight) and its mechanism: I.Varietal difference of <strong>the</strong> position offlorets in <strong>the</strong> wheat spikeletattacked by head blight incipientlyand <strong>the</strong> relationships betweenexistence of an<strong>the</strong>r corpses inflorets and <strong>the</strong> infection by headblights. Science Reports ofAgriculture (Okayama University)10:33-42.67. Takegami. S .• and R Sasai. 1966.Studies on resistance of wheatvarieties to scab (G. zeae (Schw.)Petch.): II. Inoculation into leafblade of <strong>the</strong> water-cultured plantspulled out from <strong>the</strong> field.Proceedings of <strong>the</strong> Crop SCienceSociety of Japan 34(3):252-255.68. Takegami. S .• and R Sasai. 1967.Studies on resistance of wheatvarieties to scab (Gibberella zeae)(Schw.) Petch.): VI. Scab infectionof wheat heads by <strong>the</strong> improvedmethod of inoculation by ei<strong>the</strong>rconidiospore or hyphae of <strong>the</strong> scabcultures on potato agar medium.Proceedings of <strong>the</strong> Crop ScienceSociety of Japan 39:1-6.69. Takegami. S .. and R Sasai. 1969.Studies on resistance of wheatvarieties to scab (G. zeae (Schw.)Petch): II. Infection with hyphae by<strong>the</strong> improved method of inoculationon <strong>the</strong> ligule or <strong>the</strong> inside of <strong>the</strong> leafsheath under <strong>the</strong> ligule or <strong>the</strong>inside of <strong>the</strong> leaf under <strong>the</strong> ligule.Proceedings of <strong>the</strong> Crop ScienceSociety ofJapan 38(3):384-387.70. Tammen. J. 1958. Pathogenicity ofFusarium roseum to carnation andto wheat. Phytopathology 48:423426.71. Tochetto. A. 1959. Septoriose, oidioe fusariose do trigo. Boletim doCampo RJ. XV: 16-21.72. Watanabe. S.. M. Nakagawa.H. Gocho and K. Nishio. 1968.Studies on <strong>the</strong> breeding of wheatvarieties to scab disease: II.Introduction and selection of <strong>the</strong>high resistant wheat varieties toscab disease. Tokai-KinkiAgricultural Experiment StationBulletin 18(2). Japan.73. Wiese. M.V. 1977. Compendium ofWheat Diseases. The AmericanPhytopathological Society, St. Paul,Minnesota. USA.74. Zheng. Y.M.. and Z.F. Lin. 1982.Field evaluation of scab resistantspring wheat materials. FUjianAgricultural SCience andTechnology 1:8-11. RPP 62(1): 147.(Abstract.)75. Zhu. H.• and Z.X. Guo. 1981.Studies on causal factors of wheatscab and breeding for resistantcultivars. FUjian AgriculturalScience and Technology 6:5-7. RPP61(9):4862. (Abstract.)

Head Scab Screening Methods Used at CIMMYTG.T. Bekele, Wheat Program, CIMMYT, MexicoAbstractOne of<strong>the</strong> most important methodsfor selecting adaptable and resistant wheatplants under adequate planting conditions is <strong>the</strong> disease-screening technique.CIMMYT techniques have been developed and improved in order to reduceunnecessary effort on <strong>the</strong> part ofcooperators andfarmers around <strong>the</strong> worldwhen seed is sent to <strong>the</strong>m. From a wide array ofgermplasm. selections weremadefor scab resistancefrom 220 lines screenedfrom 1980 to 1982 in Tolucaand El Batan. 21 highly resistant linesfrom China and 5 highly susceptible onesselectedfrom 1978 to 1980. Fusarium-infected wheat spikes were collectedforpure spore isolation andfresh inoculum preparation. Two inoculation methods.using cotton or using a spray. have consistently proved effective. The cottonmethod. in which a tuft ofcotton permeated withfusarium spores is placedbetween <strong>the</strong> glumes of <strong>the</strong> spike. is <strong>the</strong> most precise. but both methods areextremely effective and give well-defined results.169Disease screening is one of <strong>the</strong> majortools of plant breeders in selectingdesirable plants with better and Wideradaptation. There are a number ofdifferent disease-screeningmethodologies in operation for handlingdifferent diseases. However. as diseasesthat were once unimportant becomemore important (3). new screeningtechniques need to be developed orexisting ones improved.The question is not only one ofscreening against diseases, but also ofreducing <strong>the</strong> number of breeders'materials. For ensuring better andWider adaptation. <strong>the</strong> selected materialshave to be tested against diseases overa much wider area and under differentconditions. Preliminary testing inbreeders' plots is necessary to reduce<strong>the</strong> amount of germplasm before it issent out to cooperators for testing in hotspots.Although a naturally occurringepidemic is one of <strong>the</strong> tools ofscreening. it frequently fails to occur ina continuous pattern due to changes inclimatic conditions that favor ei<strong>the</strong>r <strong>the</strong>host or <strong>the</strong> pathogen. In this case. <strong>the</strong>flow of disease information received by<strong>the</strong> breeder can lack continuity. Inorder to assure disease developmentannually. conditions must be availableand methods continually created toassure that screening processesfunction properly. Thus. <strong>the</strong> host istested in <strong>the</strong> presence of <strong>the</strong> pathogen.Materials and MethodsOn May 31, 1983.962 advanced breadwheat lines were planted in Toluca in<strong>the</strong> State of Mexico. These same entrieswere planted on June 22. 1983. inPatzcuaro. Michoacan. While <strong>the</strong> bulkof <strong>the</strong> material was from <strong>the</strong> CrossingBlock and <strong>the</strong> 17th International BreadWheat Screening Nursery. <strong>the</strong> groupalso contained 220 lines that wereidentified as scab resistant in tests inToluca and EI Batan from 1980 to1982. Also. 21 highly resistant linesfrom China and five highly susceptiblelines were included in <strong>the</strong> plantings ascontrols.Both at Toluca and at Patzcuaro.plantings were made in two one-meterrows. Five grams of seed were plantedin each plot to assure enough heads forinoculating by two different inoculationmethods. Although <strong>the</strong> wea<strong>the</strong>r patternis similar at <strong>the</strong> two places. soils andpathogens differ greatly. In Patzcuaro.<strong>the</strong> soil has a low pH (J.K. Ransom.personal communication). and <strong>the</strong>re is

1'70an extremely high incidence of naturalscab infection. However. by takingadvantage of both natural andartificially inoculated fusarium. bothlocations are excellent sites for scabscreening (1).Fusarium i_IatioDaDd culture preparationFusarium-infected wheat spikes. forpure spore isolation and fresh inoculumpreparation. were collected from Tolucaand Pat.zcuaro. Spore isolation andpuriflcation were made on corn mealagar (CMA) (2) in <strong>the</strong> laboratory at EIBatan. For indiVidual-spike and massinoculation (spikes in one-meter singlerows). a large volume of fusariumisolates were multiplied on CMA andmungbean extract (W.Y. Zhong andW.S. Jun. personal communication).PreparatioD offUNJ'ium .pore inoculumTo prepare <strong>the</strong> fusarium inoculum.cultures grown on CMA are placed in adisinfected food blender. and blended forone minute to make a thin puree. TheCMA-culture puree is <strong>the</strong>n passedthrough several layers ofsterilized cheesecloth to obtain a clear filtrate. Whenmungbean extract is used as <strong>the</strong> culturemedium. <strong>the</strong> culture is blended for only afew seconds and filtered as above. In bothcases. <strong>the</strong> concentrated clear filtrate is<strong>the</strong>n diluted with sterilized distllled wateruntil a desired spore count per cc ofwater is attained. Thirty to fifty thousandspores per cc ofwater are suitable forCIMMYT conditions.lDoculatioD meth0d8Two different inoculation methods weredeveloped and modified at CIMMYT forcontrolled scab screening. Thesemethods are suitable both in <strong>the</strong>greenhouse and in <strong>the</strong> field underMexican conditions. They are:• The cotton method-With thismethod. a tiny tuft of cotton (cottonswab for laboratory and hospital use)is penneated with <strong>the</strong> distilled watercontaining fusarium spores insuspension. One-fourth of <strong>the</strong> cottonswab. <strong>the</strong> size ofan outer wheatglume. is pushed between <strong>the</strong>glumes and placed in contact with<strong>the</strong> an<strong>the</strong>r in a wheat floret. Sharppointedtweezers of <strong>the</strong> kindgenerally used for emasculationpurposes are used for separating <strong>the</strong>cotton tufts and for inoculating. Aglassine bag is <strong>the</strong>n placed over <strong>the</strong>inoculated wheat head to preventdamage by wind. dust or excesshumidity (rain or dew). This cottonmethod is <strong>the</strong> most precise forcontrolled scab study in <strong>the</strong>greenhouse and in <strong>the</strong> field.The method is comparable to that ofinoculation by injection with asyringe. However. unlike <strong>the</strong>injection method. <strong>the</strong> cotton methodplaces <strong>the</strong> inoculum at a specifiedinoculation point without injuringplant tissue. With <strong>the</strong> syringemethod. <strong>the</strong> water suspension candrip. contaminating o<strong>the</strong>r parts of<strong>the</strong> spike. Also <strong>the</strong>re is <strong>the</strong> possibllityof applying less inoculum withsyringe applications because. when<strong>the</strong> needle is pushed through <strong>the</strong>spike. a portion of <strong>the</strong> inoculum maybe discharged into <strong>the</strong> air. Theneedle also injures <strong>the</strong> wheat tissue.• The spray method-With thismethod. fusarium spores suspendedin water are sprayed on wheat heads.using various types and sizes of handgarden sprayers with various nozzleattachments. Also. a back-packmotor-driven sprayer can be used.For CIMMYT's advanced wheat linescreening study. a small handatomizer (commonly used as agarden pesticide sprayer). with ameter long. hard-walled plastic tube.is used. Inoculum is placed in oneliterplastic containers. and <strong>the</strong> tubefrom <strong>the</strong> spray nozzle is immersed in<strong>the</strong> container.

171Wheat spikes are spray-inoculatedfrom a distance of 10 to 15 cm until<strong>the</strong>y are soaked with sporesuspension.Crop stage for inoculationfor maximum disease developmentFor maximum scab development.wheat heads are inoculated at floweringor at an<strong>the</strong>r protrusion stage. Young.plump and yellow an<strong>the</strong>rs (not whiteand dry) are good indicators of <strong>the</strong> rightstage for inoculation as are floweringwheat heads with one to threeprotruded an<strong>the</strong>rs at <strong>the</strong> mid-point of<strong>the</strong> spike(s). In this study. a cultivarwas considered ready for inoculationwhen 5 to 10% of <strong>the</strong> extruded an<strong>the</strong>rsappeared in a plot of wheat plants. It iscritical that this growth stage is used atall times. Any inoculation at pre orpost-flowering (especially at postfloweringwhen extruded an<strong>the</strong>rs arewhite and dry) results in poor scabdevelopment.Inoculating <strong>the</strong>wheat plant in <strong>the</strong> fieldWheat plants in plots of two rows onemeter long were inoculated withfusarium spore suspension by both <strong>the</strong>cotton and <strong>the</strong> spray methods atToluca; only <strong>the</strong> spray method wasused in Patzcuaro. In Toluca. ten spikesin one row of each plot were inoculatedwith <strong>the</strong> cotton method. and eachinoculated spike covered with a glassinebag. The remaining single row inToluca and one row in <strong>the</strong> plots inPatzcuaro were spray inoculated.Spray-inoculated wheat spikes were notcovered with bags. Mter inoculation.plants were checked periodically fordisease development.Disease development and scoringScab disease developed differently onearly and late-maturing cultivars. bothat Toluca and Patzcuaro. In spite ofdifferences in inoculation time. diseasedevelopment occurred between 35 and45 days after inoculation. Diseasedeveloped more rapidly in earlymaturinglines than in later ones.Therefore. disease scoring was done42 days after inoculation. using ao to 5 scale.Disease development was excellent withboth inoculation methods. With <strong>the</strong>cotton method. spikes remained cleanand bright (straw color). since <strong>the</strong>ywere protected by <strong>the</strong> glassine bags.The movement of fUsarium infectionwas well-defined: it started at <strong>the</strong> pointof inoculation and progressed ei<strong>the</strong>r upor down <strong>the</strong> spike from where <strong>the</strong>cotton was placed. Since <strong>the</strong>re was nodripping of <strong>the</strong> liquid inoculum. <strong>the</strong>disease remained localized and <strong>the</strong>nspread to o<strong>the</strong>r spikes in a continuouspattern. without skipping spikelets.This type of disease development wasnot obtained in previous studies when<strong>the</strong> syringe injection-inoculationtechnique was used (unpublished data).With <strong>the</strong> spray method. head scabdevelopment was also excellent at bothToluca and Patzcuaro. Differencesbetween susceptible and resistant linesand between inoculated anduninoculated portions of <strong>the</strong> plots werewell defined. Susceptible lines showedbright pinkish-orange sporodochia filledwith fUsarium conidiospores. Infectedspikes (rachis. glumes and seeds) ofsusceptible lines were permeated withfusarium mycelium and filled withspores. In most cases. seed formationwas aborted or replaced bysporodochia. Symptom developmentwas good with both techniques.However. with <strong>the</strong> spray method. <strong>the</strong>rewere a large number of infection pointsin each spray-inoculated spike anddisease development was much greater.spreading over <strong>the</strong> full length of <strong>the</strong>infected spikes.Both inoculation methods were foundvaluable in identifying 198 highly scabresistantlines from <strong>the</strong> 962 lines tested.All of <strong>the</strong>se 198 selected lines showedresistance both in Toluca and in

172Patzcuaro. Among those selected lines,certain sister lines appeared repeatedlyin <strong>the</strong> list, including several sister linesofVeery and combinations with Veery(VEE"S"), Bobwhite (BOW"S"), Alondra(ALD"S"), Dove, Kavkaz (KVZ) andPasso Fundo (PF) lines (Table 1).Table 1. Some advanced wheat lines with low scab infection, identified in tests at Tolucaand Patzcuaro, Mexico, 1983Lin•• and crosse.Veery"S"CM33027·D-1M-2Y-1M·1Y-1M-oyJUP·Alondra"S"CM36867-18Y·17M·3Y-oM·1PTZ-oyVeery 8CM33027-F-12M·1Y·1M-1Y·1M-OYT -1Siskin''S''·Canario''S'' x Alondra''S''CM62319-3Y·1M·1Y-2M-2Y·1M·OYVeery 9CM33027·F-12M·1Y·12M-1Y-2M·OY2Tanager''S''/TI-TOB x Alondra''S''CM643404M-1Y·1M·2Y-1M·OY2Veery''S''-Cuclcoo''S''CM58882-oy-oM-oY-1M·5Y·1M-oyT -1Veery''S''fKalyansona-Bluebird x TQFN"S" T· 1CM67412-17Y·2M·5Y-2M-oYSiskin"S"-Veery''S'' T· 2CM58831-3M-2Y-2M·2Y·1M-oYTucan"S"·Moncho''S'' x Veery''S''CM62001 ~Y-lM·2Y-2M-l Y-lM·OYTPF7339PF71131PF70354-Alondra''S''CM47090-14M·1Y·l F·703Y-l0F·706Y-2Y-C1YPF70354-Alondra''S''CM47090-13M·1Y·l F·701Y-l F-704Y6Y-OY1-2~edpoll·Anj''S''x PVN-Veery''S''C~68735·'-4Y-1 M-3Y-1 M-OY1 - 2PF70364-Alondra''S''CM47090·1M·11OPR-1T-OTCook-Veery''S'' x Dove''S''-Veery''S''CM69279-e-2Y-1 M·lY·1 M·OYT·2PF70354-Moncho''S''CM67934·1Y-1M·1Y-3M-oYT ·1Bobwhite''S''CM3203·K-9M-9Y-4M-4Y-1 M-lY-OM1 - 2PF7619-Dove''S'' x CEP7670B25813·A·1M-4Y·1M·1Y-1M·OYBobwhite''S''CM3303-K-9M-33Y-1M-500Y-oM-1J·1JKavkaz.siete CerrosSWN4064-8Y-4M-3Y·1M-1Y-3M-oyTBobwhite''S'' x YR·Trifon''S''CM64684-2Y-2M-l Y-1 M-oyT-1Kavkaz.sapsucker x Moncho''S''-TSICM68651-e·1Y-1M-1Y-1M-oYT -1YR·Trifon''S'' x Bobwhite''S''CM68336-1Y·1M-1Y·2M-oYTanager''S''-Bobwhite''S''CM68381-8Y-1M-2Y-2M-oYTeeter''S''-Bobwhite''S''CM58857·2M·1Y-1M-3Y·1M-oyAlondra''S''.pVN''S''CM49901-14Y-2Y-1M·1y-oMAlondra''S".pVN''S''CM49901·14Y-2Y~M-4Y-oMAlondra''S''-eOCCM50351-9M·2Y·1Y-4M-1Y-oMT·l1 - 2T·1Moncho''S''-KavkazSWN-3720.6Y-3M-1Y-2M-1Y-OMDove''S"-Buckbuck''S''CM58808-8M·5Y-1M-1Y·1M-oyDove''S''-Buclcbuck''S''CM58808-27Y·2M·7Y-4M-oyDove''S''-INIA21B-1Y·1M·OYDove''S''-INIA55B·2Y·3M-oyT -11·2T -122T-1!.f Scoring scale 0 to 5 (0 = immune, 5 "" completelysusceptible, T = trace)

173Reference.1. Bekele. G.T. 1984. Screeningwheats for scab resistance. AnnualWheat Newsletter 30:77.3. Kenaga. C.B. 1970. Minor diseasebecomes major. In Principles ofPhytopathology. Balt Publishers.Lafayette. Indiana. USA.2. Cook. R.J. 1980. Fusarium foot rotof wheat and its control in <strong>the</strong>Pacific Northwest. Plant Disease64:1061-1066.

174Recent Advances inResearch on Wheat Scab in Chinaz.z. Llu, Plant Protection institute, ShaDghal Academy ofAgricultural ScleDcles, Shanghai, People'. RepubUc of ChiDaA_tractWheat scab (head. blight) caused by Gibberella zeae (Schw.) Petch is one of <strong>the</strong>most serious wheat diseases in South China. especially in <strong>the</strong> middle and lowerreaches of <strong>the</strong> Yangtze River. where <strong>the</strong>re is a hfghfrequency of incidencecausing considerable loss in yield. Scab is estimated to occur on 6.7 millionhectares in China and. in years ofsevere epidemics. losses rangefrom 10 to40~. Comprehensive research has been carried out on causal organisms.resistance of wheat varieties and testsfor resistance. including inoculationmethods. epidemiology and integrated control measures.Wheat scab (head blight). caused byGibberella zeae (SChw.) Petch. occursin almost all of <strong>the</strong> humid and semihumidregions of <strong>the</strong> tropics. <strong>the</strong>subtropics and in certain temperatezones of <strong>the</strong> world. It is one of <strong>the</strong> mostserious wheat diseases in South China.especially in <strong>the</strong> middle and lowerreaches of <strong>the</strong> Yangtse River. where <strong>the</strong>disease has a high incidence andfrequently causes severe losses. During<strong>the</strong> 28 years from 1957 to 1984. <strong>the</strong>rewere four years of severe epidemics and15 years of moderate epidemics in thisregion: <strong>the</strong> average frequency ofepidemics was about 68%. In years ofsevere epidemics. <strong>the</strong> rate of infectedspikes reached more than 50%. andyield loss ranged from 10 to 40%.: inyears with moderate spread. <strong>the</strong> ratesof infected spikes and yield loss were 20to 50% and 5 to 15%. respectively. It isestimated that wheat scab occurs in anarea that covers more than 6.7 mUlionhectares in China (7.8). Besides <strong>the</strong>direct losses caused by <strong>the</strong> disease. <strong>the</strong>pathogen also produces mycotoxins.which can cause mycotoxicoses inhumans and domestic animals (19.20).Therefore. <strong>the</strong>re is a great need to studyand control wheat scab.In 1974. a cooperative research teaminvolving scientists from 12 provincesand cities was organized by <strong>the</strong> ChineseMinistry of Agriculture. Comprehensiveresearch has been carried out on causalorganisms. resistance of wheat varietiesto scab. epidemiology and integratedcontrol measures: signiftcant advanceshave been achieved.Scab-Producing OrganismsFusarium .pp.In 1955. Yu Da-Fu (25) reported that<strong>the</strong> wheat scab-causing species ofFusarium along <strong>the</strong> Yangtse River wereF. graminearum. F. montliforme.F. culmorum and F. avenaceum. From1976 to 1980. <strong>the</strong> cooperative researchteam (1.22.28) collected 2.450 samplesof diseased wheat heads from 21provinces and cities. Eighteen speciesand varieties ofFusarium wereisolated. identlfted and classifted as tohigh. moderate or low levels ofvirulence on wheats.The species and varieties with highvirulence were:• F. graminearum Schwabe• F. camptoceras Wr. and Rg.• F. equtseti (Corda) Sacc. var.compactum (Wr. Joffe)• F. sulphureum SChlecht.• F. culmorum (W.G. Smith) Sacc.

1'71SThe species and varieties withmoderate virulence were:• F. avenaceum (Cda. ex F.) Sacc. var.gramfnum (Cda.) Sacc.• F. avenaceum (Cda. ex F.) Sacc. var.herbarum (Cda.) Sacc.• F. trtctnctum (Corda) Sacc.• F. acumtnatum Ell. et Ev.• F. ntvale (Fr.) Ces.The species and varieties with lowvirulence were:• F. equtsett (Corda) Sacc. var.longtpes (Wr. and Rg.) Joffe• F. sporotrtchtofdes Sherb. var.chlamydosporum (Wr. and Rg.) Joffe• F. sporotrtchtotdes Sherb.• F. equtsett (Corda) Sacc.• F. concolor Rg.• F. montliforme Sheld.• F. semttectum Berk. and Rav.• F. oxysporum Schlecht.Among <strong>the</strong>se. <strong>the</strong> predominant speciesin China was determined to beF. gramtnearum (Gtbberella zeae).which represented 94.5% of <strong>the</strong> totalsamples.Chen Hong-Kui and Ling Xun-yt (3)reported that F. fusarl.otdes.F. latertttum and F. oxysporum var.reclolens belonged to <strong>the</strong> low virulencegroup: <strong>the</strong>y caused decay and sterilityof floral organs. but could not induce<strong>the</strong> typical symptoms of head blight.Therefore. it is generally agreed that<strong>the</strong>se types of species could not beregarded as scab-eausing pathogens forwheat. and only ten Fusartum specieswith high and moderate virulencewould be considered as causalorganisms.VarlatloD8 of Gtbberella zeae(Fusartum gramtnearum)Gtbberella zeae is one of <strong>the</strong> specieswith great variation. not only incultural characters. but also tnvirulence. Xu Yong-gao (personalcommunication) studied four isolates ofG. zeae. collected from Mexico. SriLanka. Indonesia and China. andpointed out that <strong>the</strong>re were remarkabledifferences among <strong>the</strong>m. As comparedwith <strong>the</strong> Chinese isolate. <strong>the</strong> growthrate of <strong>the</strong> isolate from Sri Lanka wasslower. aerial mycelia were sparse. <strong>the</strong>red pigment on <strong>the</strong> substrate was verydark and no macroconidta wereproduced on potato dextrose agar(PDA). The Mexican isolate was capableof productng macroconidia on PDA. but<strong>the</strong> formation of peri<strong>the</strong>cia on wet sandwas slower and <strong>the</strong> ascospores slightlylonger. The Indonesian isolate was ,similar to <strong>the</strong> Chinese isolate. with <strong>the</strong>exception of growth rate.The work by Li Qtng-Xi and WangZhang-mtng (10) tndicated thatdifferences in both culturalcharacteristics and virulence werefound in most of 17 wild and culturedisolates of G. zeae. collected fromdifferent parts ofJiangsu province. Afew of <strong>the</strong>se isolates varied significantlyafter being transferred three times. i.e.•<strong>the</strong> growth rate was reduced. <strong>the</strong>formation of conidia and septa ei<strong>the</strong>rslowed. decreased or stoppedaltoge<strong>the</strong>r. peri<strong>the</strong>cium production wassparce or absent and vtrulence wasweakened.Based on <strong>the</strong> results of testing 43isolates collected from 27 provinces andcities on 20 wheat varieties. XuSu-zhen and Lu Jin-tu (personalcommunication) showed that <strong>the</strong>isolates of G. zeae could also be dividedinto three types. high. moderate andlow vtrulence. Xu Yong-gao and FangZhong-da (23) and o<strong>the</strong>r workersobtained <strong>the</strong> same results. Chen Hongzaoand Li Ke-ehang (4) tested <strong>the</strong>virulence of <strong>the</strong> three types byinoculating 11 wheat varieties. andconcluded that <strong>the</strong>re was a specificrelationship between isolate and wheatvariety. Li Qing-xi and Wang Zhangming(9) pointed out that isolates of

176F. gramtnearum from Jiangsu differedsignificantly in virulence. as didresistance of wheat varieties toF. gramtnearum. but interactionbetween <strong>the</strong> virulence of <strong>the</strong> pathogenand <strong>the</strong> resistance of <strong>the</strong> wheat varietywas not present. Wang Yu-chung (14)confirmed that isolates of F.graminearum from Jiangsu differedsignificantly from one ano<strong>the</strong>r invirulence. but that <strong>the</strong>re was nosignificant difference in averagevirulence among isolates from differentcounties. Xu Yong-gao and FangZhang-da (23) fur<strong>the</strong>r suggested thatsingle ascospores isolated from a .culture differed as to virulence. as didthose from an ascus. OWing to <strong>the</strong> factthat <strong>the</strong> variation of G. zeae is verycomplicated. it has been difficult toclassify <strong>the</strong> isolates of G. zeae in Chinainto different physiological races.Based on <strong>the</strong> comparative study ofvirulence of <strong>the</strong> four isolates collectedfrom Mexico. Sri Lanka. Indonesia andChina on 7 Chinese and 28 Mexicanwheat varieties. Xu Yong-gao (personalcommunication) concluded that <strong>the</strong>Chinese isolate of G. zeae was morevirulent than <strong>the</strong> Mexican isolate onboth Chinese and Mexican varieties.Resistance of WheatVarieties to ScabTypes of resistanceIn <strong>the</strong> early 1960s. Schroeder andChristensen (11) and Takegami (12)reported that <strong>the</strong> resistance of wheatvarieties could be divided into twotypes. based on whe<strong>the</strong>r <strong>the</strong> resistancewas to initial infection or to <strong>the</strong> spreadof <strong>the</strong> infection. Many Chinesepathologists have confirmed scabresistance to be to hyphal spreadingwithin wheat. but <strong>the</strong>re has not beenagreement as to resistance to initialinfection (15.23.27). Through fieldobservations over many years. manyChinese workers have indicated that<strong>the</strong> difference in <strong>the</strong> rate of diseasespread within <strong>the</strong> spike when infectedat <strong>the</strong> same flowering stage indicates<strong>the</strong> difference in resistance to initialinfection. Twenty wheat varieties weretested for resistance to initial infectionat <strong>the</strong> heading stage by keeping singlespikelets moist for two days byspraying with a spore suspension. XuYong-gao (personal communication)found that <strong>the</strong> variety Zhen-mai 7495showed a lower level of diseased heads(23 to 40%); <strong>the</strong> rest of <strong>the</strong> varietiesreached 100%. It was suggested thatZhen-mai 7495 might be resistant toinitial infection under certainconditions. but that it did not exhibitany resistance to initial infection in <strong>the</strong>flowering stage or after being keptmoist for four days. Resistance to initialinfection seemed to be affected byenvironment.Testing for resistanceThe follOWing methods are generallyused for testing resistance to wheatscab in China:• Scattering diseased wheat grains on<strong>the</strong> soil surface-This method ofindUcing epidemics in <strong>the</strong> field issimilar to natural conditions (19).The fields are kept moist by sprinkerirrigation.• Dripping spore suspension into <strong>the</strong>floret-With a syringe. <strong>the</strong> fusariumspore suspension is dripped into asingle floret in <strong>the</strong> middle of <strong>the</strong>spike (15.17,23). This method isprecise and reliable. because <strong>the</strong>inocula can be appliedquantitatively.• Cutting <strong>the</strong> glume with scissorsdipped in spore suspension-Withthis method. developed by Wang-Yuchungand Yang Xin-ning (15). <strong>the</strong>inocula is introduced into one of <strong>the</strong>spikelets in <strong>the</strong> middle of a spike bycutting <strong>the</strong> glumes with scissors thathave been dipped in <strong>the</strong> spore

177suspension. This method has provedto be reliable in testing for resistanceagainst hyphal spread.• Spraying spore suspension on <strong>the</strong>flowering spikes-This method isused in testing for resistance ei<strong>the</strong>rto initial infection or to hyphalspread.It is very important that suitablemoisture and temperature bemaintained for all of <strong>the</strong> above methodsof inoculation.Resistance assessmentThe method for asseSSing resistanceusing <strong>the</strong> rate of hyphal spread wasdeveloped by Takegami (12) and hasbeen refined by a number of Chineseworkers (4.9.13.23). The follOWing scaleof 1 to 5 would seem to be reasonable:1 = disease restricted to infectedspikelet; does not spread tospike axis2 = disease spreads from infectedspikelet to axis; does not invadeparts near spikelet3 = disease spreads along axis;invades nearby spikelets4 = disease spreads to <strong>the</strong> headabove <strong>the</strong> infected spikelet;upper part of head wilts5 = disease spreads throughout <strong>the</strong>head; entire head wiltsThese ratings do not represent <strong>the</strong>degree of resistance of a variety; <strong>the</strong>yonly reflect <strong>the</strong> course of diseasedevelopment. The resistance of varietiescan be assessed by <strong>the</strong> follOWingreaction index:• Resistant (R) (1 to 2 on <strong>the</strong>scale)• Moderately resistant (MR) (2.1to 3 on <strong>the</strong> scale)• Moderately susceptible (MS)(3.1 to 4 on <strong>the</strong> scale)• Susceptible (S) (4.1 to 5 on <strong>the</strong>scale)The reactions of resistant (R) andsusceptible (S) varieties are relativelystable and independent of <strong>the</strong> severityof <strong>the</strong> epidemic; however. <strong>the</strong> reactionindex of MR and MS varieties varieswith <strong>the</strong> epidemic conditions.Testing of varietal resistanceto scabFrom 1974 to 1982. over 30.000 wheatvarieties and materials were tested in<strong>the</strong> field by <strong>the</strong> cooperative researchteam led by <strong>the</strong> Shanghai Academy ofAgricultural Sciences. The testedmaterials included 32.618 commonwheats (varieties and lines). 1557materials of rare species belonging to21 races and 26 species of three relatedgenera. The follOWing conclusions weredrawn:• All of <strong>the</strong> materials tested were moreor less affected by <strong>the</strong> disease. butdiffered greatly in degree.• Among common wheats. <strong>the</strong>re was agroup of varieties with high andstable resistance. which alwaysshowed a lower percentage ofinfected spikelets and scabby headsand less disease spread along <strong>the</strong>axis. This was true for differentyears. different localities and underdifferent epidemic conditions. TheChinese varieties. Su-mai 3. Wangshui-baiand Nanjing 7840 all belongto this group of resistant varieties.• Sources of resistance to wheat scabare distributed over various regionsof <strong>the</strong> world where scab is endemic.The middle and lower reaches of <strong>the</strong>Yangtse River. which is one of <strong>the</strong>epidemic regions. has abundantsources of resistance to scab.• Resistant and moderately resistantvarieties were not found among <strong>the</strong>rare species of Triticum tested;however. some species of <strong>the</strong> genus.Secale. showed moderate resistanceto scab.

178Inheritance of resistance to scabSchroeder and Christensen (11)reported that <strong>the</strong> resistance of wheat tohead scab was a quantitative charactercontrolled by polygenes. In recentyears. Chinese workers have alsoshown that resistance of wheat tocolonization by G. zeae is controlled bypolygenes (27). The resistance of Fistends to resemble <strong>the</strong> resistant parent.and exhibits obvious heterosis.Backcrossing with resistant parentstends to increase resistance. XiaSui-shing. Zhou Chau-fei and Quia Cunming(personel communication) studied<strong>the</strong> inheritance of scab resistance inSu-mai 3 and Wang-shui-bai andobtained similar results. Yu Yu-jin (26)studied <strong>the</strong> inheritance of resistance ofSu-mai 3 by monosomic analysis;results indicated that at least five pairsof genes which determine resistance tohyphal spread were located onchromosomes lB. 2A. 5A. 6D and 7D.Chen Chu-huo (2). using a 4 x 4 halfdiallelscheme with two resistant andtwo susceptible parents to study <strong>the</strong>inheritance of resistance in wheat.suggested that Su-mai 3 and WangzhouHong-he-shang (Red Monk) might havemore dominant genes for controllingresistance: <strong>the</strong>y demonstrated highgeneral combining abll1ty for redUcing<strong>the</strong> rate of diseased spikelets in <strong>the</strong>irprogenies. It appears that <strong>the</strong>inheritance of resistance to scab ismainly governed by additive genes. butnon-additive genes also have asignificant effect. The genes controllingresistance were partially dominant. Itwas found in diallel crosses that <strong>the</strong>rewas a significant positive correlationbetween resistance and plant height orspike length. and a significant negativecorrelation between resistance andspikelet density in F2 populations.Various workers have suggested that<strong>the</strong> heritabll1ty of resistance of wheat toscab is low.Sources of resistance to scabThe studies of <strong>the</strong> cooperative researchteam have demonstrated that sources ofscab resistance come mainly fromcommon wheats. Some Chinesevarieties with high and stable resistancehave been <strong>the</strong> best available sources ofresistance among <strong>the</strong> world collection;<strong>the</strong> resistance in exotic varieties has notexceeded <strong>the</strong> resistance of <strong>the</strong>sevarieties. Su-mai 3 has been introducedinto many countries of <strong>the</strong> world. and<strong>the</strong>re has been no report that itsresistance is equal to or better thanlocal varieties in those countries.Nanjing 7840. a new source ofresistance. is derived from crosses of(Aurora x Anhui 11) F2 x Su-mai 3. andmany resistant varieties or lines withgood agronomic characters have beenderived from it (29).Crosses between moderately resistantand susceptible varieties may yieldhybrids with higher resistance than<strong>the</strong>ir parents. The well-known resistantvariety Su-mai 3 was bred through <strong>the</strong>hybridization of <strong>the</strong> moderatelysusceptible varieties. Funo and Taiwanwheat. The crossing of <strong>the</strong> moderatelyresistant varieties. Jingzhou 1 and Sumai2. also produced progenies withhigh and stable resistance.Some materials of <strong>the</strong> genus Secale areano<strong>the</strong>r source of resistance. Jingzhou1 was derived from <strong>the</strong> hybrid of Nanda2419 and Jingzhou rye. Jingzhou 66(MS-MR) was derived from <strong>the</strong>combination (Funo x durum) (Nanda2419 x rye). Jingzhou 1 has beenadopted as a common parent in <strong>the</strong>breeding programs for resistance toscab in South China.EpidemiologyOccurrence of scabcUsease in <strong>the</strong> fieldA rice-wheat cropping system is foundin most of <strong>the</strong> regions of <strong>the</strong> middle andlower reaches of <strong>the</strong> Yangtse River. Theinitial inocula of scab usually comesfrom <strong>the</strong> peri<strong>the</strong>cia on rice stubble.

179How <strong>the</strong> pathogen oversummers andoverwinters after <strong>the</strong> wheat harvest andhow <strong>the</strong> peri<strong>the</strong>cia reproduce areimportant factors for forecasting scabepidemics. Xu Run-cheng and HuangZhen-xing (21) suggested that G. zeaecan only survive for a short time underflooding; <strong>the</strong>refore. <strong>the</strong> organism cannotoversummer on <strong>the</strong> soil surface inpaddies after rice has been harvested.although it can survive on <strong>the</strong> plantbase. leaf sheaths and rice grains and<strong>the</strong>n be transferred to <strong>the</strong> soil (5). LiangXun-yi and Wang Qing-sheng (personalcommunication) have confirmed that<strong>the</strong> pathogen can oversummer on rice.on dry soil surfaces. on <strong>the</strong> shady sideof piles of wheat straw and on <strong>the</strong>remains of wheat stems and grainsscattered over <strong>the</strong> threshing ground. aswell as on rice straw and wi<strong>the</strong>red rapestems in fields.Research of <strong>the</strong> Hunan AgriculturalCollege suggests that <strong>the</strong> pathogenaffects not only wheat and barley. butalso such crops as corn. sorghum andcotton. It may also infect weeds, suchas Cynodon dactylon (L.) and Pers. andproduces peri<strong>the</strong>cia on <strong>the</strong> debris.The Shanghai Academy of AgriculturalSciences (1975 to 1977) and <strong>the</strong>Suzhou Institute of AgriculturalSciences (1977 and 1980) made a seriesof observations on <strong>the</strong> dissemination ofmature ascospores. The resultsindicated that aerial ascospores couldbe trapped throughout <strong>the</strong> year. Thisindicates that infected rice stubble.grains and wheat debris remaining infields and aerial ascospores which havefallen on <strong>the</strong> soil are all sources ofinoculum. causing peri<strong>the</strong>cia formationon rice stubble early in <strong>the</strong> spring. Thepathogen overwinters as mycelia onrice stubble.Ye Hua-zhi (24) studied <strong>the</strong> biology ofG. zeae and showed that <strong>the</strong>temperature for peri<strong>the</strong>cial formationranged from 5 to 35°C and. forascospore production. 13 to 33°C. withan optimum of 25 to 28°C. Thedischarge of ascospores is controlled bymoisture and precipitation. Thenumber of ascospores released isgreater at night (8 p.m. to 8 a.m.) thanby day (8 a.m. to 8 p.m.), and is greateron rainy days. The peak for sporedischarge is from 10 p.m. to 8 a.m.and. more specifically. from midnight to6 a.m. Germination of ascosporesoccurs at 4 to 35°C. with an optimumof 25 to 28°C. Germination percentagemay reach more than 90% within 4 to8 hours at a temperature of 25 to 30°C.The ascospore can germinate withoutfree water. but germination is markedlyinhibited when relative humidity is low;it doesn't occur below 81%.ForecastingVarious ma<strong>the</strong>matical models havebeen established in China forforecasting scab epidemics overdifferent'areas. The best is <strong>the</strong> oneproposed by <strong>the</strong> workers in HubeiProvince (6). Mter haVing qualitativelyanalyzed <strong>the</strong> key factors causingepidemics. and haVing quantitativelydefined <strong>the</strong> relationship between <strong>the</strong>degree of epidemic and <strong>the</strong> keymeteorological factors in GuangjiCounty over a period of 21 years. <strong>the</strong>cooperative group suggested thatepidemics depend on <strong>the</strong> interaction of<strong>the</strong> pathogen and <strong>the</strong> host with fourmeteorological factors. rainfall (R), daysof rain (Rd). relative humidity (Rh). andsunlight hours (S). The statistical modelfor calculating <strong>the</strong> incidence of diseasewas established as:Y:;:[sin (47.72 IgQ-33.64»). whereQ :;: RRdRhISThis indicates that <strong>the</strong> outbreak ofepidemics varies according to climaticand atmospheric conditions, but <strong>the</strong>semeteorological factors can be utilized toforecast epidemics for a province or fora certain area.From 1975 to 1981, short-termforecasting of scab epidemics was doneby <strong>the</strong> Shanghai Academy of

180Agricultural Sciences. through <strong>the</strong>statistical analysis of <strong>the</strong> relationshipamong meteorological factors. <strong>the</strong>number of ascospores present on whea<strong>the</strong>ads at <strong>the</strong> mUk stage and <strong>the</strong>preliminary incidence of <strong>the</strong> disease.Satisfactory results were obtained withthis program.Integrated coDtrol of scabA reasonable strategy for <strong>the</strong> integratedcontrol of scab should involve <strong>the</strong>utilization of resistant varieties. propercultural practices and <strong>the</strong> application ofchemicals in <strong>the</strong> critical growth stage.[n <strong>the</strong> early 1950s. many resistantvarieties. such as Wan-nan 2. E-mail 6.Hua-zhong 2133. Xiang-mai 1.Zhen-mai 7495. Jingzhou 1 andJingzhou 66 were bred and released. Inrecent years. still more resistantvarieties with good agronomiccharacters. such as Yangmai 4.Nanjing 8017 and Nanjing 8026. havebeen released.[n <strong>the</strong> beginning of <strong>the</strong> 19708. manyworkers reported that Benzimidazole(BMZ) was an efficient systemicchemical for controlling wheat scab.Since 1978. a series of rapid andefficient techniques have beendeveloped. such as those of <strong>the</strong> JiangsuAcademy of Agricultural Sciences(15.16). to improve <strong>the</strong> effects of BMZ.These include <strong>the</strong> use of a BMZsuspensoid.soluble agent. which is amicronized powder. instead of wettablepowder. Also. a new type of atomizerhas been produced to change <strong>the</strong>application of <strong>the</strong> chemical from highvolume to low. and <strong>the</strong> spray from fineto atomized. This increases chemicalcoverage and enhances adhesion to <strong>the</strong>wheat heads to prevent its beingwashed off by rain.This combination of new resistantvarieties and new methods of applyingfungicide has brought <strong>the</strong> level ofintegrated control to a new high.References1. All-ehina Cooperation of Researchon Wheat Scab. Studies onFusarium species infection onspikes of wheat in China. 1984.Journal ofShanghai Teachers'College (Natural Science Section) 3.2. Chen. C.H. 1983. Acta AgriculturaeUniversitatis Zhejiangensis9(2):115-126.3. Chen. H.K.. and Ling Xun-yt. 1982.Acta Phytopathologica Sinica12(3):1-12.4. Chen. H.Z.. and K.C. Li. 1982.Biology Communications(38-50):40-52.5. Huang. Z.X.• and R.C. Xu. 1983.Journal of Jiangsu AgriculturalScience 7:30-31.6. Hubei Provincial Cooperative Groupfor Long-Range Forecast ofGibberella zeae in Wheat. 1983.Statistical model of Gtbberella zeaeepidemic in wheat and methods oflong-range forecast in HubeiProvince. Scientia AgriculturaSinica 1:71-77.7. Jin. S.B. 1983. Chinese wheatcultivars and <strong>the</strong>ir pedigrees.Agricultural Press. Peking. China.8. Li. K.C. 1982. Wheat scab and itscontrol. 2nd ed. Science andTechnology Press. Shanghai. China.9. Li. g.X.• and Z.M. Wang. 1982.Acta Phytophylacica Sinica9(3): 163-168.10. Lt. g.X.• and Z.M. Wang. 1983.Acta Phytophylacica Sinica10(1):25-32.11. Schroeder. H.W.. andJ.J. Christensen. 1963.Phytopathology 53:831-838.

18112. Takegami, S. 1961. Proceedings of<strong>the</strong> Crop Science Society of Japan29:245-248. (In Japanese.)13. Wang, Y.C., X.N. Yang andC.P. Hsiao. 1981. Journal ofJiangsu Agricultural Science1(3):38-41.14. Wang, Y.C. 1982. Journal ofJiangsu Agricultural Science10:46-47.15. Wang, Y.C., and X.N. Yang. 1982.Scientia Agricultura Sinica 5:67-77.16. Wheat Scab Research Group,Jiangsu Province. 1984. Journalof Jiangsu Agricultural Science3:25-28.17. Xia, Y.O., C.P. Hsiao and C.X. Gao.1955. Acta Phytopathologica Sinica1(1): 19-29.18. Xu, F.N. 1982. Journal of NanjingAgricultural College 1: 105-107.19. Xu, F.N. 1983. Journal of NanjingAgricultural College 1:72-90.20. Xu, R.C., and Z.X. Huang. 1982.Journal of Jiangsu AgriculturalScience 4:26-29.21. Xu, R.C., and Z.X. Huang. 1983.Journal of Jiangsu AgriculturalScience 4:24-28.22. Xu, Y.G., and Z.S. Yang. 1980.Journal of Nanjing AgriculturalCollege 1(1):119-126.23. Xu, Y.G., and Z.O. Fang. 1982.Acta Phytopathologica Sinica12(4):53-57.24. Ye, H.Z. 1980. Acta PhytophylacicaSinica 79(1):35-42.25. Yu, O.F. 1955. Acta PhytopathologicaSinica. 1(1): 1-18.26. Yu, Y.J. 1982. Journal of HuazhongAgricultural College 2:70-72.27. Zhang, L.Q., and X.P. Pan. 1982.Journal of Hunan AgriculturalCollege 3(2):21-29.28. Zhen, Y.M., Z.F. Lin and Z.O. Zhu.1983. Acta Phytopathologica Sinica13(2):53·59.29. Zhou, C.F., S.S. Xia and C.M. Qian.1984. Journal of JiangsuAgricultural Science 2: 15-18.

182Reflections on Foot Rots of Wheat inWarmer, Nontraditional Wheat-Growing ClimatesH.J. Dubio, Wheat Program, CIMMYT, Quito, EcuadorAbstractInJormation is presented on Sclerotium rolfsii. Rhizoctonia solani, andHelminthosporium sativumJoot rots in warmer areas. It is noted that <strong>the</strong>Jacultative nature oj mostJoot rot pathogens mayJacilitate <strong>the</strong>ir movingJromrotation crops to wheat in tropical areas. Effective control may require <strong>the</strong>integration oj breedingJor resistance or tolerance. appropriate agronomicpractices and chemical or biological control.The introduction of wheat as a possiblecommercial crop in warmer or tropicalclimates has been increasing in recentyears (8). The difficulty of achievingeconomic yields should not beunderestimated; <strong>the</strong>re are a myriad ofproblems inherent in transposing atemperate climate crop to tropicalareas. One of <strong>the</strong> principal problemswill be <strong>the</strong> unique diseases encounteredin <strong>the</strong>se nontraditional areas and howto control <strong>the</strong>m.Foot rot is one of <strong>the</strong> diseases of wheatthat may have to be confronted andcontrolled in subtropical or tropicalareas. Wheat scientists must be awareof <strong>the</strong> type of pathogens <strong>the</strong>y aredealing with. and that <strong>the</strong> ecological orhost-pathogen relationships in <strong>the</strong>hotter. humid areas may be quitedifferent from those preVailing intemperate climates. An exhaustivereview of <strong>the</strong> literature of foot rots ofwheat in <strong>the</strong> tropics is not presented;indeed, very little publishedinformation exists. What little is citedshall serve only as examples.Fungal pathogens constitute <strong>the</strong> focusof this paper, with some mention alsomade of nematode diseases. since <strong>the</strong>ymay be of some importance. However.it should be noted that bacteria, virusesand related organisms could becomeproblems also. The fungal organismscausing foot rots are. without exception,facultative parasites that spend most of<strong>the</strong>ir life cycles as saprophytes in <strong>the</strong>soil or on plant debris. Plant parasiticnematodes generally are obligateparasites that feed and reproduce onlyon <strong>the</strong>ir liVing hosts. Never<strong>the</strong>less.although <strong>the</strong>y are obligate parasites. inmany cases <strong>the</strong>y do not appear to havedeveloped high levels of pathogenicspecificity, and so often <strong>the</strong> samespecies can attack many diverse typesof plant hosts (10).As noted. fungal facultative parasitesprimarily exist as saprophytes andbecome parasitic when <strong>the</strong> appropriateconditions are met. These parasiteshave a minimum of pathogenicspecialization and probably haveevolved to a level of speciescompatibility. ra<strong>the</strong>r than cultivarspecificity or compatibility (5). Since<strong>the</strong>y are not as fastidious as <strong>the</strong> fungalobligate parasites, <strong>the</strong>y may, if given<strong>the</strong> opportunity. become parasitic on anontraditional crop when it isintroduced into an area. It can beexpected that cropping patterns andhusbandry practices may have animportant impact on foot rots of wheat.Diseases of rice and soybeans. forexample. might be important on wheat.and vice versa. This would also holdtrue for <strong>the</strong> facultative. foliarpathogens. This must be kept in mindwhen considering present foot rotproblems. diseases of potentialimportance in <strong>the</strong> future and suggestedcontrol strategies.

183Documented Foot RotDlseaBes in Warmer ClimatesBased on personal observations.discussions with colleagues andsearches of <strong>the</strong> literature. <strong>the</strong>re is littledoubt that <strong>the</strong> main wheat foot rotpathogen in tropical areas at present is&lerotium rolfsU sacc.: reports fromsou<strong>the</strong>rn India. as well as from BrazU.have been published (6.7). S. rolfsU hasbeen observed on wheat in Ecuador.Peru and Bolivia. and it has been notedin many countries of Sou<strong>the</strong>ast Asia(E.E. Saari. personal communication).Sclerotium rolfsH is an omniverous.soU-inhabiting organism withworldwide distribution. attacking morethan 500 species in over 100 plantfamUtes (2). It survives as sclerotia in<strong>the</strong> soU for long periods of time and.although <strong>the</strong> organism has been <strong>the</strong>object of a great deal of research. fewcontrol measures exist o<strong>the</strong>r thanra<strong>the</strong>r costly chemical treatments (2).Due to its polyphagous nature andlongevity in <strong>the</strong> soU. this organism wUlbe dttncult to control without chemicalmeans.Rhtzoctonia solani Kuhn is ano<strong>the</strong>rWidespread soU pathogen that has beenobserved on wheat in <strong>the</strong> semitropicalareas of BrazU (7). As wheat is testedand grown in warmer areas. and aspathologists begin making moreintensive observations. R. solani willsurely become more obvious. Betterprogress has been made in breeding forresistance to R. solani than to S. rolfsUbut. overall. resistance breeding has notbeen very successful. One reason maybe that R. solani is made up ofgenetically distinct groups and. thus.R. solani is not a single species butconsists of diverse populations that maybe recognized through anastomosisgrouping (1). As more pathologists andbreeders take this into consideration.progress may be made in breeding fordisease resistance.Helminthosportum sativum P.K. and B.causes a severe foot rot problem inmany areas of BrazU (7). Up to now.major efforts in more tropical areashave dealt with <strong>the</strong> follar diseasecaused by H. sativum. but closerexamination of roots and crowns mayindicate <strong>the</strong> presence of <strong>the</strong> foot rotphase of this organism as well.The above examples point to some of<strong>the</strong> foot rot organisms that pathologistsand breeders will have to deal with indifferent areas. The foot rots are causedby some of <strong>the</strong> most dttncult pathogensto control in temperate climates. Due tosuboptimal growth conditions for <strong>the</strong>host. coupled with optimal conditionsfor <strong>the</strong> pathogens in tropical areas. <strong>the</strong>achievement of economic controlmeasures may be dttncult to obtain.Diseases of PossibleImportance in <strong>the</strong> FutureBased on <strong>the</strong> nature of <strong>the</strong> foot rotorganism. pathogens that attackrotation crops may become problems inwheat. Two examples may be sufficientto Ulustrate this point. Recently.R. oryzae-sativa.e sawada hasincreased in severity and incidence onrice in California: <strong>the</strong>re is an apparentcorrelation between this and <strong>the</strong>increased use of semidwarf cultivars (4).Three factors might indicate <strong>the</strong>possible importance of an R. oryzaesativae-typeorganism in tropical areas.First. wheat-rice rotations will beimportant: second. <strong>the</strong> organism Isadapted to warm climates and. third. itattacks many hosts. Thus it not onlymight attack wheat. but could becomeincreasingly important on rice.A second example is related to a wheatsoybeanrotation in Indiana whereGaeumannomyces graminis (Sacc.)Arx and Ollv.• normally infecting wheatand grasses. was isolated from

184immature, field-grown pods of sixsoybean cultivars. The soybean isolateswere able to produce typical take-allsymptoms on wheat roots and stems.This could have a significant effect ontake-all disease in that area (9).In regard to nematodes, examples ofpossible pathogens might be <strong>the</strong> rootknot nematodes, Melotdogyne spp., and<strong>the</strong> cyst nematodes, Heterodera spp.,both of which occur on cereals,including rice. in warmer climates(3, 10). Once again, <strong>the</strong> introduction ofwheat into an area may provide anappropriate host for <strong>the</strong>se or o<strong>the</strong>rnematodes.These are only a few examples of <strong>the</strong>possible disease syndromes that couldoccur. However. many gr.oups of soilfungi might become relatively moreimportant in warmer climates as. forexample. <strong>the</strong> fusaria and <strong>the</strong> watermolds.Possible Avenues of ControlAs better understanding of <strong>the</strong>epidemiology and genetics of foot rotorganisms is achieved, resistance andtolerance will become more useful toolsfor breeders. When dealing with moretropical conditions, obtaining adequateresistance or tolerance becomes evenmore elusive due to <strong>the</strong> predispositionof <strong>the</strong> host in those climates. It isprobable that, for a long time to come.an integration of resistance ortolerance, appropriate husbandrypractices and chemical or biologicalcontrol will be critical to procuringadequate. economical control measuresof foot rot organisms. Breeders andpathologists should be aware that, insome warmer areas, it may beimpossible to obtain high levels ofdisease control. due to <strong>the</strong> nature of <strong>the</strong>environment and <strong>the</strong> condition of <strong>the</strong>host.However, <strong>the</strong>re is no need forpessimism ei<strong>the</strong>r; a possible scenariofor attaining adequate control ofS. rolfstt can be used as an example. Todate, some progress has been made insou<strong>the</strong>rn India with chemical seedtreatments, such as Carboxin, PCNBand Guatazine, for controlling S. rolfsttthrough <strong>the</strong> seedling stage (6). Theseseed treatments have a dual advantagesince <strong>the</strong>y also control loose smut andcommon bunt. The next step might beto find some level of resistance ortolerance in wheat that would increase<strong>the</strong> level of control. Mechanicalresistance has been found inLycoperstcon pimptnellifolium where.after six weeks, phellem developmentprevents penetration of S. rolfsii (2).Perhaps analogous types of resistancecould be found in wheat or relatedgenera. Finally, a multipronged attackmight include planting rotation cropsthat reduce sclerotial formation, orPCNB might be applied to <strong>the</strong> soil toreduce inoculum potential. The point tokeep in mind is that no single controlmeasure may be adequate. To have <strong>the</strong>best chance of success. pathology andbreeding will have to be fullyintegrated.Although <strong>the</strong> literature is meagerrelating to foot rots. some examples offoot rot organisms have been presentedthat are problems at this time, as wellas o<strong>the</strong>rs that could become problems,with <strong>the</strong> hope of making breeders andpathologists aware of <strong>the</strong> greatercomplexity of controlling facultativeparasites in tropical areas as comparedto temperate zones. Controlmethodologies may also have to bemore complex. and levels of controlmay never approach immunity.

185References1. Anderson. N.A. 1982. The geneticsand pathology ofRhtzoctontasolant. Annals of <strong>the</strong> Review ofPhytopathology 20:329-347.2. Aycock. R 1966. Stem rot ando<strong>the</strong>r diseases caused bySClerottum rolfstt. North CarolinaAgricultural Experiment Station.Raleigh. North Carolina. USA.3. Cheaney. RL.• and P.R; Jennings.1975. Field problems of rice inLatin America. Centro Internacionalde Agricultura Tropical. SeriesGE-15. Cali. Colombia.4. Gunnel. P.S.• and RK. Webster.1984. Aggregate sheath spot of ricein California. Plant Disease 68:529531.7. Mehta. Y.R.. and N.RX. deNazareno. 1983. Doencas do trigono Estado do Parana. FundacaoInstituto Agronomico do ParanaDocumento 8. Londrina. Brazil.8. Rajaram. S.. P. Brajcich andL. Butler. 1984. Wheats for tropicalareas. In CIMMYT Report on WheatImprovement 1981. CIMMYT.Mexico. Pp. 11-13.9. Roy. K.W.• T.S. Abney. D.M. Huberand R Keeler. 1982. Isolation ofGaeumannomyces gramtnts var.gramtnts from soybeans in <strong>the</strong>Midwest. Plant Disease 66:822-825.10. Sou<strong>the</strong>y. J.F. 1965. PlantNematology. Ministry ofAgriculture. Fisheries and FoodTechnical Bulletin 7. Her Majesty'sStationery Office. London. England.5. Heath. M.C. 1981. A generalizedconcept of host-parasite specificity.Phytopathology 71:1121-1123.6. Kulkarni. S. 1980. Chemical controlof foot rot of wheat in Karnataka.Pesticides 14(5):29-30.

186A Review of Major Wheat Diseasesin Tropical EnvironmentsJ.M. Prescott, Wheat Program, CIMMYT, MexicoAbstractThe mqjor wheat diseases in tropical environments are not always <strong>the</strong> same asthose of temperate environments. In <strong>the</strong> warm and humid tropics. <strong>the</strong> majordiseases are leaf rust (puccinia recondita). leaf spots (Helminthosporium sativum.H. tritici-repentis. H. giganteum and Fusarium nivale), root rot and seedlingblights (H. sativum. Fusarium spp.• Rhizoctonia spp.• Sclerotium rolfsH andPhytium spp.), head scab (Fusarium spp.) and loose smut (Ustilago spp.). Lesscommon diseases are downy mildew (Scleropthora macrospora). bacterialdiseases (Xanthomonas campestris) and barley yellow dwarf (BYD). Karnal bunt(Neovossia indica) has not been reported.Traditionally. wheat cultivation hasbeen confined to <strong>the</strong> more temperateclimatic areas of <strong>the</strong> world. and <strong>the</strong>diseases which attack <strong>the</strong> crop in <strong>the</strong>setraditional wheat areas are well knownand fairly well documented. Recently.interest has grown in producing wheatin <strong>the</strong> warmer and more humid tropicalareas. where it is grown during <strong>the</strong>cooler part of <strong>the</strong> year and often inrotation with rice or maize. While it isrecognized that yields equal to those in<strong>the</strong> more traditional areas cannot beattained. wheat appears to be a viablealternative crop for some countries in<strong>the</strong> tropics. These countries are foundin Sou<strong>the</strong>ast Asia. Western Africa.Sou<strong>the</strong>rn Africa. Central America andparts of South America. However. whenwheat is promoted in <strong>the</strong>se regions. anumber of problems appear that canlimit <strong>the</strong> introduction and/or productionof wheat.Diseases are often a major constraint.particularly in <strong>the</strong> warm and humidareas. When speaking of <strong>the</strong> tropics.one often visualizes warm and wetconditions; <strong>the</strong>re are. however. alsoareas of <strong>the</strong> tropics where <strong>the</strong>environment can be classified as warmand dry. In <strong>the</strong>se areas. such as Sudanand Nigeria. diseases are not a problem.However. with expanding areas underwheat. it is expected that diseases willbecome more of a problem in <strong>the</strong>future.In <strong>the</strong> warm and humid areas of <strong>the</strong>tropics, diseases playa major role indetermining whe<strong>the</strong>r wheat can besuccessfully grown. The major diseasesin those areas are leaf rust. leaf spots.root rots and head scab.Leaf rust. caused by Pucciniarecondtta. is by far <strong>the</strong> most importantof <strong>the</strong> rust diseases in <strong>the</strong> tropics. Stemrust is seldom seen. and stripe rust onlyin <strong>the</strong> highlands and cooler areas. InSou<strong>the</strong>ast Asia. leaf rust is found inmost countries, but usually attackingonly <strong>the</strong> older cultivars. indicating that<strong>the</strong> races of <strong>the</strong> pathogen are primitiveand that adequate resistance isavailable. However. as <strong>the</strong> area underwheat cultivation expands. it is possibleand probable that races with additionalvirulence will begin to appear. Theepidemiology of <strong>the</strong> rusts in <strong>the</strong> tropicsis not well understood but. if <strong>the</strong>ybehave as <strong>the</strong>y do in <strong>the</strong> moretemperate regions. arrival of morevirulent inoculum can be expected.When <strong>the</strong> virulence of <strong>the</strong> leaf rustpopulations in India and Bangladeshare examined. it is found that only afew of <strong>the</strong> major genes are effective

187against leaf rust by <strong>the</strong>mselves,indicating a potential danger toSou<strong>the</strong>ast Asia. as <strong>the</strong> subcontinent is<strong>the</strong> build-up area.The major leaf spot of wheat in <strong>the</strong>warm and humid tropics is caused byHelminthosporium sattvum and iscurrently found in almost all of <strong>the</strong>areas of <strong>the</strong> tropics where wheat isbeing grown or introduced. Thisorganism can attack many members of<strong>the</strong> Gramineaejamtly. The role ofinoculum build-up on collateral hostsneeds to be investigated fur<strong>the</strong>r.Resistance is available. but it is not asclear-cut as in <strong>the</strong> rusts. Several of <strong>the</strong>papers being presented here will dealwith this subject. Resistance to thisdisease will be necessary, possiblysupplemented by fungicides. beforesuccessful wheat cultivation can beattained in many tropical areas. Severalo<strong>the</strong>r fungi. such as H. trttict-repentts.H. giganteum and Fusarium nivale arealso found to be causing leaf spots inwheat. Many of <strong>the</strong>se pathogens areseed-borne or survive and multiply oncrop debris in <strong>the</strong> soil.Root rots and seedling blights causedby H. sativum. several Fusarium spp.,Rhtzoctonia spp.. Sclerotium rolfstt andPhythium spp. are more often found in<strong>the</strong> tropical environments than in <strong>the</strong>more traditional wheat areas. Moreinvestigation into seed treatmentfungicides. along with substantialimprovement in resistance screeningresearch. is needed. Again. severalpapers in <strong>the</strong> follOWing sessions willdeal with this topic. However. <strong>the</strong>remust be an awareness of this group ofdiseases and <strong>the</strong>ir potential in <strong>the</strong>warm and humid areas of <strong>the</strong> tropics.Head scab is caused by several speciesof <strong>the</strong> fungal genus. Fusarium. It isconsidered severe in sou<strong>the</strong>rn China,parts of Brazil. Zambia and mostcountries of <strong>the</strong> warm and humidtropics. Losses can be total in very badyears, rendering <strong>the</strong> grain producedunsafe for consumption. No highlyresistant cultivars are in commercialproduction. but a number of cultivarshave moderate resistance. Majorcooperative research programs areunderway between Brazil. China andCIMMYT.Loose smut may pose a threat to futureadvances of wheat if proper seed-testingtreatment and production proceduresare not followed.Kamal bunt is presently not found in<strong>the</strong> warm and humid tropics. but isconfined to <strong>the</strong> Indian subcontinent andto Mexico. More research is necessary toascertain whe<strong>the</strong>r <strong>the</strong> organismNevossia indica could survive under<strong>the</strong> warm and humid conditions of <strong>the</strong>tropics. India and Pakistan. as well asCIMMYT. have major researchprograms searching for resistance. aswell as determining effective chemicalcontrol measures.Downy mildew can be a localizedproblem whenever managementpractices allow water to stand in wheatfields; it should be watched.Bacterial diseases such as those causedby Xanthomonas campestrts can be aproblem when wheat is grown underwarm. wet and humid conditions.However. <strong>the</strong> use of clean seed andgood management practices canminimize losses.Barley yellow dwarf virus (BYDV) has<strong>the</strong> potential to cause serious problemsin <strong>the</strong> tropics. Barley yellow dwarf is anaphid-transmitted disease found inmost wheat-growing countries.Resistance in wheat and chemicalcontrol of <strong>the</strong> vector are <strong>the</strong> principalmeans of control.

188In summary. <strong>the</strong> better-known diseasesof wheat in <strong>the</strong> more traditional areas ofwheat cultivation are not always <strong>the</strong>most important diseases in tropicalenvironments. Disease research hasbeen centered in <strong>the</strong> traditional wheatareas; consequently. very little isknown about wheat diseases in <strong>the</strong>warm and humid tropics and muchmore research is necessary.

-188Distribution and Importance ofRoot Rot Diseases of Wheat, Barley andTriticale in South and Sou<strong>the</strong>ast AsiaE.E. Saari. Wheat Program. CIMMYT. MezlcoAbstractWheat and barley are cultivated under a wide range ofenvironments in SouthAsia. and <strong>the</strong> climates varyfrom temperate to tropical. In Sou<strong>the</strong>ast Asia.wheat. barley and triticale are experimental crops. There are a number ofrotations involved. as cropping intensities are generally greater than one crop inboth South and Sou<strong>the</strong>ast Asia. The influence ofenvtronment and croppingsystem has a pronounced effect on soil-borne cUseases. with a number ofcommon pre-emergence and post-emergence diseases reported; afew uniquesoil-borne diseases arefound in <strong>the</strong> more tropical environments. Most of <strong>the</strong>research on soil-borne diseases has been descriptive; <strong>the</strong>re is relatively littleiriformation on ei<strong>the</strong>r losses or control.Wheat and barley are traditional cropsin <strong>the</strong> South Asian countries ofPakistan. India and Nepal. The climaticconditions in <strong>the</strong>se countries varywidely. depending upon latitude andaltitude. The majority of <strong>the</strong> acreage.however. is cultivated on <strong>the</strong> plains ofnor<strong>the</strong>rn India and Pakistan. and on<strong>the</strong> plains of Nepal bordering on India.There is a small area cultivated in <strong>the</strong>mountainous areas of all threecountries. and some acreage in centraland sou<strong>the</strong>rn India which can beclassified as subtropical to tropical.The cultivation of wheat has beenexpanding into new areas in <strong>the</strong> past15 years (9). The most notable increasein acreage has been in Bangladesh.sou<strong>the</strong>rn and eastern India and. morerecently. Burma. There has been anincreasing awareness and interest in<strong>the</strong> possibUities of wheat cultivation in<strong>the</strong> countries of Sou<strong>the</strong>ast Asia as well.Wheat as a possible crop in <strong>the</strong>senontraditional areas has developedmainly as a result of <strong>the</strong> closing gap in<strong>the</strong> production of <strong>the</strong> basic food crop.rice. The growing level of wheatconsumption and imports. with itsimplications for foreign exchange. isalso contributing to <strong>the</strong> question ofwheat cultivation. There is interest in<strong>the</strong> possible cultivation of wheat forcrop diversification and intensificationduring <strong>the</strong> dry season in <strong>the</strong>se areas.The climate ofSouth and Sou<strong>the</strong>astAsia is typified by a monsoon season.The duration of <strong>the</strong> rainy season varies.depending upon several factors. but it ischaracterized by high rainfall. humidityand warm temperatures. Rice is <strong>the</strong>main crop in <strong>the</strong> lowlands or whereverwater can be contained for a floodedpaddy. In well-drained soils. numerousupland crops are available. Themonsoon season is generally followedby a drier. cooler season. The dryperiod is defined as those months withless than 100 mm of precipitation. Theaverage temperatures are <strong>the</strong> coolestduring this period of <strong>the</strong> year. andrelative humidity is lower. In <strong>the</strong>nor<strong>the</strong>rn hemisphere. December andJanuary are generally <strong>the</strong> coolest anddriest months.Historically. few crops have beencultivated during this period. unlessirrigation is available. In areas withlimited irrigation. vegetable crops oro<strong>the</strong>r high cash-value crops aregenerally grown. Where irrigation is

190readily available. a number of crops arepossible. If temperatures are mild. anadditional rice crop may be grown or.in cooler regions. an irrigated wheatcrop can be sown. The rainfed areas arenot cultivated in many instances.although <strong>the</strong> soil moisture situation isoften saturated or at field capacity after<strong>the</strong> rainy season crop is harvested.There are some farmers who broadcasta short-cycle crop. such as mungbean.to utilize residual moisture.The cropping patterns. climate andagronomic practices involved have aprofound effect on soils and <strong>the</strong>irmicrobiology. This combination offactors also has a strong influence ondisease-causing organisms. Organicmatter decomposes rapidly dUring <strong>the</strong>monsoon period. so crop debrisproduced in <strong>the</strong> dry season does notserve as a source of inoculum for <strong>the</strong>follOWing wheat. barley or triticale crop.Paddy rice cultivation creates ananaerobic situation. and <strong>the</strong> floodedcondition is detrimental to <strong>the</strong> survivalof most plant pathogens. Thecultivation of ano<strong>the</strong>r crop species in<strong>the</strong> monsoon season constitutes arotation. which generally reducesinoculum of disease-causing organisms.unless that organism has <strong>the</strong> capacityto cause disease in both crop species.The disease surveillance programsconducted in Pakistan. India. Nepal andBangladesh have recorded most of <strong>the</strong>known diseases of wheat. barley andtriticale (5.10.13.18.25.28). The soilbornediseases have been considered asminor in relative importance comparedto <strong>the</strong> o<strong>the</strong>r commonly occurringdiseases. There are occasional fieldswhich are seriously affected. but overalleconomic losses have not beenestablished except for some notableexceptions.At <strong>the</strong> higher elevations. and in remoteareas where chemical seed treatment isnot feasible. <strong>the</strong> soil-borne bunts(Tilletia spp.) can be serious diseases ofwheat. Flag smut (Urocystts agropyrt)is soil-borne and endemic in <strong>the</strong>nor<strong>the</strong>rn plains of Pakistan and India.and <strong>the</strong> cultivation of susceptiblevarieties has brought about an increasein <strong>the</strong> frequency of this disease (10).Kamal bunt (Neovossia i.ndi.ca) hasbecome much more prevalent in <strong>the</strong>past few years in <strong>the</strong>se areas (12). Thedramatic increase in this diseaseprobably reflects a combination offactors. Most of <strong>the</strong> new varietiesreleased during <strong>the</strong> past decade areconsidered highly susceptible. Thespread of <strong>the</strong> wheat-rice rotation mayalso be a factor that has contributed to<strong>the</strong> current increase in diseaseprevalence. There are also severalnematodes reported. but Heteroderaavenae (Globodera spp.). <strong>the</strong> oat cystnematode. is <strong>the</strong> most serious.In <strong>the</strong> tropical and subtropicalenvironments of Sou<strong>the</strong>ast Asia. wheat.barley and triticale are not growncommercially. The introduction of <strong>the</strong>sethree species into <strong>the</strong> cropping systemhas been primarily experimental. Thehigher mean temperature and relativehumidity changes <strong>the</strong> relativeimportance of some of <strong>the</strong> diseases. ascompared to <strong>the</strong> semi-temperate areasof South Asia (3.4.8.24).FoHar Diseasesin More Tropical EnvironmentsLeaf rust of wheat (Pucci.nia recondita)has been observed. but only on oldervarieties known to have little or noresistance. Consequently. it appearsthat primitive race forms must becoming from some grasses and that.with <strong>the</strong> expansion of wheatcultivation. new virulences undoubtlywill arise which can attack <strong>the</strong>cultivated varieties. No leaf rust onbarley or triticale has been observed.

191Surprisingly. little or no stem rust (P.graminfs) has been recorded. although<strong>the</strong> environment must be consideredideal for <strong>the</strong> disease (4.24).Helminthosporium leaf blight(Helminthosporium sativum). alsoknown as Bipolarfs sorokiniana andDrechslera sorokiniana. with <strong>the</strong>perfect stage Cochliobolus sativus. is aserious and sometime limiting factor towheat and barley cultivation in tropicalenvironments. Severe leaf blight. spikeand seed infections are common(4.8.14.17).Soil-borne DiseasesIn Sou<strong>the</strong>ast Asia. <strong>the</strong> soil-bornediseases of upland crops can be dividedinto pre and post-emergence diseases.damping off and root and stem rots(19). A survey by <strong>the</strong> International RiceResearch Institute in <strong>the</strong> Philippines ofdisease problems of upland crops sownafter wetland rice indicates thatspecialized pathogens are suppressedby flooding. rotation and certain tillageoperations. The unspecializedpathogens with a wide host range. suchas Sclerotium rolfsii. Pythium spp. andRhizoctonia solani (19.28). areprOVided an advantage and becomeimportant pathogens in <strong>the</strong> system.Observations from experimental plots ofwheat. barley and triticale in farmers'fields suggests that <strong>the</strong> main dampingoff and root or stem rot-causingorganisms are Sclerotium rolfstt.Helminthosporium sativum andFusarium spp. (3.4.14.24. personalobservation).S. rolfsii predominates in <strong>the</strong> heaviersoils of <strong>the</strong> paddy rice-wheat. barley ortriticale rotation (9.27). Warmtemperatures and high moistureconditions are associated with <strong>the</strong>establishment of <strong>the</strong> disease. Infectionoccurs at all stages of plant growth. orat least <strong>the</strong> death of plants can occur atany stage of development (27). Droughtstress often results in premature deathand numerous "white heads" in <strong>the</strong>field. These probably reflect incipientinfections which are manifested by <strong>the</strong>drought stress. The post-damping-offstage is easily recognizable. and occurscommonly in <strong>the</strong> rice-based rotation.The establishment of a proper plantpopulation is often affected. Informationon pre-emergence damping off in wheatis not readily available.Roots and crowns of infected plants areusually covered with a fluffy whitemycelium and. if <strong>the</strong> surface of <strong>the</strong> soilis damp. mycelium will radiate outfrom <strong>the</strong> stem on <strong>the</strong> surface of <strong>the</strong> soil.Sclerotial bodies form readily on <strong>the</strong>surface of <strong>the</strong> plant tissue and even on<strong>the</strong> soil surface. Young sclerotia arewhite in color and darken to brownblackwith age. The fungus survivesei<strong>the</strong>r on alternative host species or assclerotial bodies in <strong>the</strong> soil.There are numerous species ofhelminthosporium in Asia. and severalare reported to be pathogens of wheat(20). The species Helminthosporiumsativum appears to be <strong>the</strong> predominantpathogen in South and Sou<strong>the</strong>ast Asiaon wheat. barley and triticale. Onnumerous isolations from leaf samplesfrom <strong>the</strong> tropical and subtropical areasofSou<strong>the</strong>ast Asia. H. sativum has beenidentified in more than 90% of <strong>the</strong>samples; many grass species are alsohosts for H. sativum (8.17. E.E. Saari.unpublished data).Helminthosporium leaf blight is aserious disease of wheat. barley and. toa lesser extent. triticale (3.4.8.14). Thedisease can be sufficiently severe inareas with high relative humidity that itbecomes a limiting factor to <strong>the</strong>cultivation of wheat and barley;temperature also seems to play animportant role in <strong>the</strong> case of wheat (21).

192At higher altitudes or latitudes. whereminimum temperatures are cooler.wheat becomes less susceptible thanbarley.The amount of spike or kernel infectionby H. sativum in <strong>the</strong> tropics can besignificant. If severe leaf infection ispresent and some rain occurs afterheading. <strong>the</strong> percentage of graininfection may exceed 50% (personalobservation). This high level of kernelinfection has major implications onseedling blight or damping off if <strong>the</strong>grain is used for seed. Both pre andpost-emergence damping offwill be at ahigh level. and root infections. whichcan lead to dryland foot rot. will also bepresent. In lighter soil areas and uplandcropping sites. H. sativum can bereadily identified from <strong>the</strong> roots ofunhealthy plants and dead plants thathave white heads. Helmtnthosporiumas <strong>the</strong> cause of damping off and rootrots in wheat and barley has beenestablished. but <strong>the</strong> extent of lossescaused by H. sattvum as compared too<strong>the</strong>r root diseases is not known.The Fusarium spp. are known to causeseedling blights and root rots of smallgrain cereals wherever wheat or barleyis cultivated. and it has also beenidentified as a root rot of wheat andbarley in <strong>the</strong> nontraditional areas ofSou<strong>the</strong>ast Asia (3.4). Fusarium is foundmore commonly in <strong>the</strong> upland rotations.particularly with maize. The rotation ofmaize with wheat and barley is knownto favor Fusarium graminearum(Gtbberella zeae). In areas with highhumidity or rain at heading time. <strong>the</strong>presence of head scab disease is often aserious problem. The situation inSou<strong>the</strong>ast Asia is different in tha<strong>the</strong>ading occurs at <strong>the</strong> driest period.which often approaches droughtconditions; consequently. scab has notbeen of importance except at highaltitudes where rain occurs (E.E. Saari.unpublished data).There are three species of Fusariumreported. F. graminearum.F. culmorum and F. moniliformi (3.4);in one report. F. moniliformi was <strong>the</strong>fungus most frequently isolated fromroot samples (3). O<strong>the</strong>r fungi have beenreported. but <strong>the</strong>ir pathogeniccapacities have not been established.The role of nematodes and <strong>the</strong>irpossible synergistic effects on root rotshave not been examined. The riceflooded conditions are known to bedetrimental to plant pathogenicnematodes. but <strong>the</strong> upland situation isdifferent. The addition of one crop sownimmediately after <strong>the</strong> harvest ofano<strong>the</strong>r proVides a bridge in some casesand a possible break crop for o<strong>the</strong>rs.Two reports involVing nematodes fromThailand identified root knot(Melotdogyne spp.) and stubby root(Paratrichodorus spp.) nematodes atlevels high enough to cause damage tocereal crops (4.D. Saunders. unpublished data).Disease Control PossibilitiesResistant varietiesThe development of resistant varietieswould be <strong>the</strong> ideal solution for control;however. <strong>the</strong> resistance to root rotscaused by S. rolfstt, H. sativum andFusarium spp. in wheat. barley andtriticale is not clear (4.14). Observationsby <strong>the</strong> author and o<strong>the</strong>rs suggest thatresistance to S. rolfsit probably does notexist. at least in a readily usable form.Differences in relative susceptibilitydoes occur between bread wheat andbarley (4); barley seems far moresusceptible. according to preliminaryobservations. Triticale has not beentested to <strong>the</strong> same degree. so <strong>the</strong>relative differences have not beenestablished.There are reported differences inresistance to H. sattvum in <strong>the</strong> foHarphase of <strong>the</strong> disease (1,4.14). Wheatappears to be more tolerant than barleyand even resistant at cooler

193temperatures. but this difference Isvastly reduced in <strong>the</strong> humid tropics.Differences in resistance in <strong>the</strong> breadwheats are perceivable. but are smallunder such conditions (4.14). Thepossible use and value of this differenceneeds fur<strong>the</strong>r evaluation. It Is possiblethat <strong>the</strong> resistance in barley toH. saltvum may also disappear in <strong>the</strong>humid tropics. but this subject has notreceived sufficient attention. Triticaleseems to have a greater degree ofresistance. but it has not been tested asextensively as <strong>the</strong> bread wheats. Thedurum wheats appear not to be welladapted. and so have received littleattention in <strong>the</strong> tropical environments.These differences recorded in resistanceto <strong>the</strong> foliar phase of <strong>the</strong> disease mayormay not apply to <strong>the</strong> seedling blightand root rot phase. No comparativework has been done on this subject in<strong>the</strong>se environments. but <strong>the</strong>re is someevidence that tolerance and degrees ofresistance to <strong>the</strong> root-attacking phase isoperative from temperate environments(26).The inoculum potential ofH. sattvumin tropical environments is severe. andit is found in abundance on numerousgrass species (4.8.14.17). The role ofinoculum potential in overcomingresistance in temperate climates hasbeen described (26) and. obviously. alsowill be an important factor in tropicalenvironments.Information on <strong>the</strong> possible resistanceto fusarium root rots Is limited (26). and<strong>the</strong>re is none currently ava1lable fortropical environments. The prospectsfor resistant or tolerant varietiesappears to be limited.Agronomic practicesThere are no established culturalpractices that can be recommendedwith confidence at this time for limitingseedling blights or root rots in tropicalenvironments. A number of possibi11tiesexist. but <strong>the</strong>y require carefulevaluation. For example. S. rolfstt isfavored in saturated soU-moistureconditions. Even small differences indrainage and root aeration appear tohave major effects on <strong>the</strong> growth andhealth of wheat and barley. There is aquestion of whe<strong>the</strong>r sowing on ridgesmight be beneficial to reducing rootrots. It has been observed that Wide-rowspacing has an effect on <strong>the</strong>development of <strong>the</strong> follar phase ofH. sattvum. but it is not known if thishas a carry-over effect on <strong>the</strong> root rotphase. The implications of weedcontrol. soU tlllage. ridging. sowingdepth. date of sowing. irrigationpractices. rotation and no-tlllage havenot been critically evaluated. althoughfield observations suggest <strong>the</strong>y may beextremely important in certain rootdisease situations (6.7.11.23).Chemical controlLimited information Is ava1labl~ on <strong>the</strong>effectiveness of chemical treatments onroot rots and seedling blights in moretropical environments. An initialevaluation on fungicide treatment madein 1984 at Central Luzon stateUniversity in <strong>the</strong> Philippines was oflimited success. Seed treatmentreduced infections by 53% over <strong>the</strong>control plots. but <strong>the</strong> level of infectionwas stlll high in <strong>the</strong> treated plots (27).The use of systemic fungicides or oneswith a greater fungal specificity mayprovide better control (2.22).A seed treatment combined with one.or possibly two. foliar applications. toprovide control of soU and seed-bornepathogens and to reduce <strong>the</strong> foliardisease-infection phase. appears to havemerit (4.16). Its combination withagronomiC practices to reducepredisposition of wheat and barley toroot diseases could fur<strong>the</strong>r enhance <strong>the</strong>effectiveness of chemical seed and foliartreatments.

194The development of resistant varietiesis a possibility for <strong>the</strong> future. Even asmall degree of resistance combinedwith proper agronomic practices andcritical chemical treatments could havemajor effects on reducing seedlingblights and root rots. The combinedeffort could also have an effect on <strong>the</strong>o<strong>the</strong>r disease phases which have beenmentioned here.References ,1. Adlakha, K.L., RD. Wilcoxson andS.P. Raychaudhuri. 1984.Resistance of wheat to leaf spotcaused by Btpolarts sOToktntana.Plant Disease 68:320-321.2. Anonymous. 1984. AnnualProgress Report Phase II, 1983-84.Department of Plant Pathology,Faculty of Agriculture, KasetsartUniversity-Australian CooperativeAgricultural Research Project.Bangkok, Thailand. pp. 115-123.3. Chuaiprasit, C. 1981. Diseases ofbread wheat, durum wheat, barley,oats and triticale in Thailand (inThai). In Proceedings of <strong>the</strong>Highland Cereal Crops Workshop.Nor<strong>the</strong>rn Agricultural DevelopmentCenter, Chiang Mai. Thailand. Pp.237-239.4. Chantarosnit. A., andH. Luangsodsai. 1981. A review offive years research on diseases ofwheat and barley. In Proceedings of<strong>the</strong> Highland Cereal CropsWorkshop. Nor<strong>the</strong>rn AgriculturalDevelopment Center, Chiang Mai,Thailand. Pp. 233-236.5. CIMMYT. 1983. Common Diseasesof Small Grain Cereals: A Guide toIdentification. F.J. Zillinsky.CIMMYT. Mexico.6. Cox, RW., F.C. CollinS andJ.P. Junes. 1976. Soybean seedlingdiseases associated with doublecropping. Arkansas Farm Research25:5.7. Doupnik, B. Jr., and M.G. Boosalis.1980. Ecofallow-a reduced tillagesystem-and plant diseases. PlantDisease 64:31-35.8. Exconde, O.R. F.D. Fuentes andE.S. Gicale. 1966. Etiology ofHelmtnthosportum leaf spot in <strong>the</strong>Philippines. Ph1l1ppine Agriculturist69:711-729.9. Hanson. H.. N.E. Borlaug andR.G. Anderson. 1982. Wheat in <strong>the</strong>Third World. Westview Press Inc..Boulder. Colorado. USA.10. Hassan. S.F. 1984. Wheat diseasesand <strong>the</strong>ir relevance to improvementand production in Pakistan. InProceedings of <strong>the</strong> FourthFAOlRockefeller Foundation WheatSeminar, Tehran, Iran. FAO. Rome.Italy. Pp. 284-286.11. Huber. D.M. 1981. Incidence oftake-all of wheat in Indiana. PlantDisease 65:734-737.12. Joshi, L.M.• D.V. Singh.K.D. Srivastava and R.D.Wilcoxson. 1983. Kamal bunt: aminor disease that is now a threatto wheat. Botanical Review 49:309·330.13. Karki. C.B. 1982. Tan spot ando<strong>the</strong>r foliar diseases of wheat inNepal. In Tan Spot of Wheat andRelated Diseases Workshop. NorthDakota State University. Fargo,North Dakota. USA. Pp. 76-81.

19~14. Lapis. D.B. and M.C. Kamatoy.1984. Varietal reactions of wheat todiseases. Annual Report: WheatVarietal Improvement Program.Department of Plant Pathology.University of <strong>the</strong> PhlUppines. LosBanos. PhlUppines.15. Lapis. D.B.. and M.C. Kamatoy.1984. Field evaluation of fungicidesagainst helminthosporlum leaf spoton wheat. Annual Report: WheatVarietal Improvement Program.Department of Plant Pathology.University of <strong>the</strong> PhlUppines. LosBanos. PhlUppines.16. Lapis. D.B.• and M.C. Kamatoy.1984. Nursery evaluation offungicides against helminthosporlumleaf spot of wheat. AnnualReport: Wheat VarietalImprovement Program. Departmentof Plant Pathology. University of <strong>the</strong>PhUlppines. Los Banos. PhlUppines.17. Lapis. D.B.. and T.E. Umall. 1984.Additional host range of Helmtnt~sportum sattvum in <strong>the</strong>PhlUppines. Annual Report: WheatVarietal Improvement Program.Department of Plant Pathology.University of <strong>the</strong> PhlUpplnes. LosBanos. PhlUppines.18. Mathre. D.E. 1982. Compendium ofBarley Diseases. AmericanPhytopathological Society andMontana State University. St. Paul.Minnesota. USA.19. Mew. T.W.• and F.A. Elazegui.1982. Disease problems In uplandcrops grown before and afterwetland rice. In Cropping SystemsResearch in Asia. IRRI. Los Banos.PhlUpplnes. pp. 100-113.21. Nema. K.G.• and L.M. Joshi. 1973.Spotblotch disease of wheat Inrelation to host-age. temperaturesand moisture. IndianPhytopathology 26:41-48.22. Reddy. H.R. B.G.P. Kulkarni andRK. Hedge. 1976. Studies onchemical control of foot rot onwheat in Karnataka. MysoreJournal of Agricultural Science10:428-431.23. Roy K.W.• T.S. Abney. T.S. Huberand R Keeler. 1982. Isolation ofGaeumannomyces gramtnts var.gramtnts from soybeans In <strong>the</strong>Midwest. Plant Disease 66:822-825.24. SaarI. E.E. 1983. Major diseases ofwheat In <strong>the</strong> rice-wheat rotation.Mimeographed paper. InternationalRice Research Conference. IRRI.Los Baflos. PhlUppines.25. SaarI. E.E.• and RD. WUcoxson.1974. Plant disease situation ofhigh-yielding dwarf wheats in Asiaand Mrlca. Annual Review ofPhytopathology 12:49-68.26. Scardaci. S.C. 1982. Common rootrot of cereals In California. PlantDisease 66:31-34.27. Tiburclo. E. 1984. Occurrence offoot rot and <strong>the</strong> effect of fungicideseed treatments on &lerottumrolfstt. Unpublished data. CentralLuzon State University. NuevaEclja. PhlUpplnes.28. Wiese. M.V. 1977. Compendium ofWheat Diseases. The AmericanPhytopathological Society. St. Paul.Minnesota. USA.20. Misra. A.P. 1973. Helmtnthosportumspecies occurring oncereals and o<strong>the</strong>r gramlneae. TheCatholic Press. Ranchi. India.

196Chemical Control Measuresfor <strong>the</strong> Major Diseases of Wheat, withSpecial Attention to Spot BlotchY.R. Mehta and S. Igarashi, Instituto Agronomico de Parana,Londrina, Parana, BrazilAbstractSpot blotch. rusts, and scab are some of <strong>the</strong> most important diseases in manytropical countries. Frequently, more than one disease appears at <strong>the</strong> same time.Success in chemical control of a disease complex depends on <strong>the</strong> use ofanappropriate spraying schedule which takes into consideration 1) appropriatefungicide and dosagefor <strong>the</strong> diseases and <strong>the</strong> variety in question. 2) time offirstspraying. 3) number ofsprayings and 4) <strong>the</strong> interval between sprayings. For adisease complex. Maneb or Mancozeb should always be used in afungicidalmixture. Spot blotch is well controlled by three tofour applications ofManeb orMancozeb or three applications ofPropiconazole.Although yields by some farmers intropical areas, and more particularly inLatin American countries, exceed 3,000kg per hectare, <strong>the</strong> average yieldsduring <strong>the</strong> past ten years have variedbetween 1,000 and 1.200 kg/ha. Theprimary causes of such low yields areprobably adverse climatic conditionsand severe disease epidemics.One of <strong>the</strong> major problems for wheatproduction in most tropical countries is<strong>the</strong> severe disease complex. Such adisease complex may include majordiseases like leaf rust (Pucciniarecondita Rob. ex Desm.) spot blotch(Bipolaris sorokiniana Sacco ex.Sorokin, syn. Helminthosporiumsativum P. K. and 8.). and head blightor scab (Fusarium graminearum)Schwabe (Gibberella zeae (Schw.)Petch. These diseases can be controlledby <strong>the</strong> use of resistant varieties;never<strong>the</strong>less. until resistant varietiesare available. chemical control shouldreceive due priority.At present, <strong>the</strong>re are more than 20different fungicides available for <strong>the</strong>major wheat diseases. and new ones arecontantly being introduced into <strong>the</strong>market. When considering fungicideuse. economic aspects must be takeninto consideration. The success ofchemical control depends mainly on anappropriate spraying schedule. andconsideration must be given to1) appropriate fungicide and dosage for<strong>the</strong> disease ana <strong>the</strong> variety in question.2) time of first spraying. 3) number ofsprayings and 4) <strong>the</strong> interval betweensprayings.An appropriate spraying schedule hasbeen established for Brazil andParaguay. and it is being used withgood success; <strong>the</strong> schedule needs to befur<strong>the</strong>r established on a regional basis.However. considering <strong>the</strong> commondisease complex problem among LatinAmerican countries, <strong>the</strong> existingspraying schedule can be used in o<strong>the</strong>rcountries with some modifications, ifnecessary.Fungicides and DosageFungicides are normally selected andrecommendf'd as a result of yielddifferences between treated plots andcheck plots. During <strong>the</strong> past severalyears. more than 30 fungicides withdifferent active ingredients have beentested on <strong>the</strong> most popular varieties inBrazil. ei<strong>the</strong>r alone or in combination.

197According to a new criterionestablished for <strong>the</strong> selection andrecommendation of fungicides for foliardiseases. a fungicide that does notmaintain <strong>the</strong> infection level at less than50% at growth stage DC (decimal code)83 (2) is not selected or recommendedfor <strong>the</strong> disease in question. Allfungicides selected. using this criterion.have led to statistically higher yields ascompared to check plots.The degree of efficiency of a particularfungicide depends on <strong>the</strong> cultivar.Contact fungicides are less expensivebut are also less efficient than systemicfungicides and. for this reason. <strong>the</strong>yshould be used for less susceptible orslow-rusting cultivars. Systemicfungicides. on <strong>the</strong> o<strong>the</strong>r hand. shouldbe used on fully susceptible cultivars. toobtain reasonably good disease controland guarantee economic returns.Among <strong>the</strong> systemic fungicides. <strong>the</strong>most efficient ones for leaf rust areTriadimefon and Propiconazole; <strong>the</strong>yalso give some protection against stemrust (Table 1). For spot blotch. <strong>the</strong>re areonly a few fungicides which offerreasonably good control. i.e.. Maneb.Mancozeb and Propiconazole. Theefficiency of Propiconazole (1.0 It/ha)against spot blotch has also been seenin some experiments.The efficiency of Maneb and Mancozebas protection against several fungaldiseases has long been known.Experimental data from <strong>the</strong> past severalyears indicate that three to fourapplications with one of <strong>the</strong>sefungicides give good control of spotblotch. A fungicidal trial against spotblotch was conducted in 1983. toconfirm once again <strong>the</strong> efficiency ofsome Dithiocarbamates and some newsystemic fungicides. Propiconazole at areduced rate (0.5 It/ha) was stilleffective. but not superior to Maneb orMancozeb. However. it is gaining inimportance. since it also offers goodcontrol for o<strong>the</strong>r diseases. such aspowdery mildew. septoria and leaf rust.Therefore. it has been concluded thatpropiconazole should only be usedwhen more than one foliar disease ispresent. When only spot blotch ispresent. Maneb or Mancozeb alonegive good results.Scab is ano<strong>the</strong>r important disease inLatin America. Existing varieties aresusceptible. and chemical controlmeasures have not been efficient. It isbelieved that fungicides of <strong>the</strong>Benzimidazol group are <strong>the</strong> only oneseffective against scab. Detailed studieson <strong>the</strong> chemical control of this diseasewere carried out. but showed no clearevidence of any efficiency differencebetween Methyl Thiofanate.Thiabendazol and Benomil; <strong>the</strong>tentative conclusion is that none of<strong>the</strong>se fungicides are highly efficientagainst scab. Sensitivity monitoring of<strong>the</strong> fungal populations for resistantstrains needs to be carried out.Time of first sprayingThe timing of <strong>the</strong> first spray applicationis of primordial importance in <strong>the</strong>spraying schedule. Under normalconditions. <strong>the</strong> disease epidemic starts45 to 55 days after sowing. at leastunder Brazilian and Paraguayanconditions. The first spraying should bedone soon after <strong>the</strong> first appearance ofdisease symptoms. It is recommendedthat. for early-matUring cultivars (suchas Anahuac and Cocoraque). <strong>the</strong> firstspraying should take place 45 to 55days after sowing and. for m'edium orlate maturing ones (such as Alondra4546 and PAT7219). 50 to 55 daysafter SOWing. If <strong>the</strong> disease epidemiconly starts 80 days after SOWing. <strong>the</strong>n<strong>the</strong> first spraying should be done <strong>the</strong>nand not before. If an interval of 15 daysbetween sprayings is maintained.initiating <strong>the</strong> spraying at 45 to 55 daysafter sowing will protect <strong>the</strong> crop up to<strong>the</strong> soft dough stage. After that. it is notnecessary to control leaf diseases. sinceyield losses will be almost negligible.

198Table 1. Fungicide. and spraying schedule for control of <strong>the</strong> major wheat diseases, BrazilFungicideApplication no. 1(45-55 days after sowing)One of <strong>the</strong> following:ChlorothalonilManeb or MancozebPropiconazolePropinebPyracarbolide +ManebTriadimefonTriforineTriphenyltin acetateApplication no. 2(15 days later)Any of <strong>the</strong> above fungicides and dosagesApplication no. 3(15 days after <strong>the</strong> second)One of <strong>the</strong> above fungicidesplus one of <strong>the</strong> followingfungicides to control scab:BenomylCarbendazinThiabendazinThiophanate-methyl..AI C = contact, S = systemicMode ofICtion.!lCCSCS+CSSCSSSSDosage(kg or It/ha)2.52.50.52.51.5 +2.50.51.52.00.50.50.50.5Note: Powdery mildew is not of general occurrence and is not considered important.However, under conditions favorable for <strong>the</strong> disease, one of <strong>the</strong> following fungicidesshould be added in <strong>the</strong> second application: Ethirimol (1.0 It/ha), Pyrazophos(1.0 It/ha), Oxythioquinox (0.51t/ha) or Tridemorph (0.51t/ha). Use of <strong>the</strong>sefungicides is not necessary if Propiconazole or Triadimefon is used in <strong>the</strong> secondapplication.

199Loss in yield is directly proportional to<strong>the</strong> time when <strong>the</strong> epidemic starts.Yield losses of <strong>the</strong> cultivar Jupatecowere assessed by controlling <strong>the</strong> start of<strong>the</strong> epidemic, using appropriatefungicides. Whert <strong>the</strong> epidemic startedas early as 30 days after sowing, loss inyield was 70%; when <strong>the</strong> epidemicstarted 51, 58, 64 and 72 days aftersowing, losses were 54, 44, 40 and 4%,respectively (Figure 1).The timing of <strong>the</strong> first spraying is soimportant because, after <strong>the</strong> epidemichas become established, chemicalcontrol of <strong>the</strong> disease is uneconomical.Starting fungicidal spraying soon after<strong>the</strong> start of an epidemic ei<strong>the</strong>r paralyzesit for 30 to 40 days or substantiallyreduces <strong>the</strong> rate of infection, dependingon <strong>the</strong> type of fungicide used. Theobjective is not to obtain 100% controlof <strong>the</strong> disease, but to maintain its levelbelow 50% up to <strong>the</strong> soft dough stage.For this reason, systemic fungicidesshould be used for susceptible cultivarsto delay <strong>the</strong> start of <strong>the</strong> epidemic, andprotectant fungicides for lesssusceptible cultivars (slow-rustingcultivars) to reduce <strong>the</strong> rate of infection.Number of sprayingsNormally three sprayings arerecommended but, with spot blotch,<strong>the</strong>re may be a need for four. Theexperience in Brazil indicates that, if<strong>the</strong> disease epidemic starts 45 to 55days from sowing, at least threesprayings are necessary to obtaineconomic returns. Never<strong>the</strong>less, withprolonged dry periods (40 to 50 days)after tillering, two spraytngs may beenough. Spot blotch is a very fastgrowingdisease, especially underwarm, wet conditions, and it can attack<strong>the</strong> spikes as well as <strong>the</strong> leaves. Undersuch conditions, <strong>the</strong> disease can only becontrolled with at least three to foursprayings with Maneb or Mancozeb orthree sprayings with Propiconazole.Three or four applications not onlyreduce <strong>the</strong> rate of infection of <strong>the</strong>disease on <strong>the</strong> leaves, but protect <strong>the</strong>spikes from becoming infected. Sincewea<strong>the</strong>r conditions are very changeablein Latin America, <strong>the</strong> exact number ofsprayings cannot be predetermined.100Y= 20,415 + 2,885x-O,043x2-~§ eo'0-1IJ>=80 12 =0,984020•32 51 58 64 72Days Mter SowingJl'igure 1. Loss in yield in relation to <strong>the</strong> start of <strong>the</strong> leaf ru.t epidemic on<strong>the</strong> caltlvar Japateco, Brun, 1978

200Interval between spraying.The fourth important aspect of <strong>the</strong>spraying schedule is <strong>the</strong> intervalbetween fungicidal applications.Experience indicates that <strong>the</strong> intervalshould be about 15 days. regardless of<strong>the</strong> kind of fungicide used. With specialreference to spot blotch. whenprotectant fungicides like Maneb orMancozeb are used. and when wea<strong>the</strong>rconditions are very favorable to <strong>the</strong>disease. <strong>the</strong> interval should be reducedto 10 to 12 days.Maneb or Mancozeb are broad-spectrumfungicides and. as a rule. should beused for complex disease situations.Besides being very economical. <strong>the</strong>iruse minimizes <strong>the</strong> danger of creatingresistant strains of <strong>the</strong> pathogen.Although <strong>the</strong> establishment ofanappropriate spraying schedule is ofutmost importance before any controlmeasure is employed. no hard and fastrules can be laid out. On-<strong>the</strong>-spotmodifications are quite often necessary.and <strong>the</strong> wheat variety. wea<strong>the</strong>rconditions and <strong>the</strong> intensity of <strong>the</strong>disease must be considered.References1. Mehta. Y.R.. S. Igarashi andN.R.X. Nazareno. 1978. Urn novocriterio para avaliar fungicidascontra doenccas foliares do trigo.Summa Phytopathologica 4:55-66.2. Zadoks. J.C.. T.T. Chang andC.F. Konzak. 1974. A decimal codefor <strong>the</strong> growth stages of cereal.Eucarpia Bulletin 7.

Chemical Control ofHelminthosportum sativumon Runfed Wheat In ZambiaR. Raemaeker8, Belgian De'9'elopment Cooperation, Mount MakuluResearch Station, Cbllauga, ZambiaAbstractStgniftcant ratnfed wheat yield losses due to diseases caused byHelminthosporium sativum were measured during three seasons infield testswith Mexican wheat varieties in Zambia. It was demonstrated that high rainfedwheat yields could be obtatned with chemical disease control. Trtadimefon andFenttnacetate-maneb controlledfoltar infections and head blight better thano<strong>the</strong>r chemicals infield experiments. Trtadimenol effectively controlled seedltnginfections caused by H. sativum and o<strong>the</strong>r pathogens.201Zambia annually requires 180.000 tonsof wheat to meet an ever-rising demandfor bread; most of this is imported.Approximately 10% of <strong>the</strong> annualrequirement is produced locally. asirrigated wheat dUring <strong>the</strong> winter.Although <strong>the</strong> yields are high. <strong>the</strong> areaunder irrigation is not increasing.Therefore. production of ratnfed wheatis now being encouraged in Zambia.There is plenty of suitable landthroughout <strong>the</strong> country and. withadapted cultlvars and <strong>the</strong> participationof large and small-scale farmers. localproduction could increase significantlyin a short period of time.However. diseases. especially thosecaused by Helminthosporium sativum(syn. Drechslera soroldniana: Bipolartssoroktniana) are a major problem onratnfed wheat in Zambia. Throughout<strong>the</strong> country. <strong>the</strong> climatologicalconditions during <strong>the</strong> rainy season areoptimal for <strong>the</strong> development of <strong>the</strong>fungus. Grasses are considered as <strong>the</strong>main source of inoculum. and naturalepidemics occur each year. Infectionsstart from tilIering onwards. and maydevelop very qUickly after flowering.depending on wea<strong>the</strong>r conditions. Allabove-ground plant parts and grain canbecome infected. The combination ofspot blotch on <strong>the</strong> leaves. head blight.stem infection and black point mayresult in severe crop losses.During preVious years. several testswere carried out in Zambia todetermine crop losses caused by H.sattvum and to assess <strong>the</strong> effectivenessofvarious chemicals to control foliarinfections. head blight and seedlinginfection (damping-om. Ten crop lossassessment tests were done over threeseasons. with two dates of seeding peryear. Mexican wheat cultivars wereused. which are susceptible to foliardiseases and head blight. caused byH. sattvum; resistant wheat cultivarswere not available at that time. Sincedifferent wea<strong>the</strong>r conditions occurredeach season. <strong>the</strong> condftlons for <strong>the</strong>development ofH. sattvum and <strong>the</strong>disease pressures on <strong>the</strong> crop varied.Moderate and high crop losses wererecorded.In order to measure crop losses. threedifferent disease levels were alwaysmaintained in <strong>the</strong> tests. Although itwas not possible to have disease-freeplots. near total disease control wasobtained with fungicides. such asvarious Dithiocarbamates.ChlorothalonU. Captafol andTriadimefon. Sometimes two to threeapplications per week were necessaty.The natural epidemic was allowed todevelop in <strong>the</strong> unsprayed plots. and athird disease level with moderate

202infection was obtained with lessfrequentfungicide applications. Spotblotch and head blight were scoredweekly. The average crop loss. ascalculated from all tests for <strong>the</strong> differentseasons. was 45% of <strong>the</strong> yield of <strong>the</strong>healthy plots; <strong>the</strong> maximum crop losswas 85% of <strong>the</strong> yield of healthy plots.For all practical considerations. thiswas a total crop loss. Severe foliarnecrosis and head blight was recordedin plots which were exposed to <strong>the</strong>natural epidemic. Yields of more than3 tlha were obtained in disease-freeplots. with a maximum yield of 3.6 tlharecorded. Such yields are an indicationof <strong>the</strong> potential for rainfed wheatproduction in Zambia if H. sattvum iscontrolled. ei<strong>the</strong>r genetically and/or byfungicide applications.Rainfed wheat production with frequentfungicide use is certainly out of <strong>the</strong>question. due to economicconsiderations. If <strong>the</strong> input of afungicide is going to be considered. itwould have to be a highly effectivechemical with very good persistence ata maximum of one or two applications.Fungicide tests were carried out with<strong>the</strong> Mexican wheat cultivars. Anorientation trial with <strong>the</strong> variety Sonora64 showed that plots which receivedtwo applications of various standardcontact fungicides did not have yieldsdifferent from those of <strong>the</strong> unsprayedplots. The objectives were changed and.instead of concentrating on <strong>the</strong> numberof applications. <strong>the</strong> emphasis wasplaced on finding an effective formula.Nine chemicals were evaluated on <strong>the</strong>variety Mexipak dUring <strong>the</strong> 1978season. Two spray intervals were used.with spraying starting from <strong>the</strong> firstsigns of visible infection, which was onemonth after seeding. Eight sprayings atweekly intervals were applied,compared to three sprayings atintervals of three weeks. Above-averagerainfall was recorded dUring <strong>the</strong> postfloweringperiod, prOViding <strong>the</strong> rightconditions for <strong>the</strong> development of <strong>the</strong>H. sattvum epidemic in <strong>the</strong> plots and,consequently, for proper screening of<strong>the</strong> chemicals. The fungicides whichwere tested were Captafol. Tridemorphmaneb.Triadimefon. Fentinacetatemaneb.Mancozeb. Metiram. Maneb.Benomyl and Methylthiophanate. Theunsprayed control plots yielded only0.2 tlha under high disease pressureconditions. Fentinacetate-maneb andTriadimefon were <strong>the</strong> most effectivechemicals in slOWing down <strong>the</strong>epidemic. Plots which were sprayedwith <strong>the</strong>se chemicals at intervals ofonce every three weeks yielded 0.8 tlha.Plots sprayed with Fentin at weeklyintervals yielded 1.7 tlha versus 1.0tlha for plots sprayed with Triadimefon;a significant reduction of foliar infectionand head blight was recorded for both.Head blight and node infection (stembreak) were better controlled byFentinacetate-maneb than byTriadimefon.These two chemicals were comparedduring <strong>the</strong> next season with three newproducts, RH2161, EL228 and ImazalU,and also with a tank mix ofFentinacetate-maneb with Tridemorphmaneb.Four sprayings with eachchemical were applied at intervals oftwo weeks, from flag leaf appearanceonwards. The high disease pressure of<strong>the</strong> previous season did not occur, and<strong>the</strong> hand-harvested control plots yielded1.9 tlha. Plots sprayed withTriadimefon. Fentinacetate-maneb and<strong>the</strong> tank mix yielded 3.4 tlha. 2.8 tlhaand 3.2 tlha, respectively; <strong>the</strong>se yieldswere not significantly different fromeach o<strong>the</strong>r. Plots which were sprayedwith RH2161 also yielded significantlybetter than <strong>the</strong> control plots. but <strong>the</strong>yields were lower than those of <strong>the</strong>Triadimefon plots; perhaps a higherdosage of RH2161 could have bridgedthis gap. EL228 and Imazalll did notcontrol <strong>the</strong> disease sufficiently. andplots which were sprayed with <strong>the</strong>sechemicals did not have yields differentfrom those of <strong>the</strong> unsprayed controlplots. The efficacy of Triadimefon andFentinacetate-maneb for <strong>the</strong> control of

203H. sattvum on foliage and heads ofwheat was confirmed. Black pointoccurrence was recorded in this test; itwas highest in <strong>the</strong> plots with <strong>the</strong>highest yield.The next test was initiated to compareone and two applications of <strong>the</strong> tankmix Trtadimefon-captafol with that ofFentlnacetate-maneb and with <strong>the</strong> newproduct. Propiconazole. The improvedvariety Kavkaz x Kalyansona-Bluebird.with a better resistance to H. sattvumthan Mexipak. was by <strong>the</strong>n available.Captafol was added to Trtadimefon toimprove <strong>the</strong> control of head blight. Dueto insufficient rainfall after heading. <strong>the</strong>epidemic did not develop well and <strong>the</strong>plants suffered from drought stress.The plots which were sprayed withTriadimefon-captafol yielded 1.8 t/ha.but this yield was not significantlydifferent from <strong>the</strong> yield of <strong>the</strong>unsprayed control plots.Damping-off is also a problem in rainfedwheat in Zambia. especially whenperiods of prolonged drought stressoccur soon after emergence. A complexof H. sattvum. Rhtzoctonta solant.Rhtzoctonta spp. and Fusarium spp.are usually found on <strong>the</strong> roots. crownsand coleoptUes of infected plants.Laboratory experiments were carriedout to test seed treatment formulationsfor <strong>the</strong> control of <strong>the</strong>se soil-bornediseases. The variety Jupateco wasused in <strong>the</strong>se tests. since no varietalresistance to damping-off was thoughtto exist. selected seeds were treatedwith dry formulations of <strong>the</strong> follOWingchemicals: Thiram-malathion (standardseed treatment in Zambia). Thirammalathion-carbendazim.Carboxinthiram-ltndane.Triadimenol.Funnecyc1ox-captan. Funnecyc1ox.Imazalil-bird repellent. Carbendazimand Chlorathalonll. The seeds weregerminated in water agar in wide testtubes. Each test tube had one seed. andfive seeds made up one "plot." Sevendays after seeding. a plug of agar withmycelium was deposited near <strong>the</strong>germinated seed. Three fungi weretested separately. H. sattvum. R. solantand F. gramtnearum. The coleoptlleinfection was scored ten days afterinoculation. The only chemical seedtreatment which controlled all threediseases effectively was Triadimenol. Itwas also <strong>the</strong> only chemical whichcontrolled H. sattvum. R. solant wasalso controlled by Carboxin andFunnecyc1ox; F. gramtnearum wascontrolled equally well by Carbendazimand Trtadimenol. Rainfed wheat seed inZambia is already being treated withTrtadimenol. although <strong>the</strong>se resultshave not yet been confirmed in fieldtests.These test results show that <strong>the</strong>re areeffective systemic and contactfungicides for <strong>the</strong> control of foliarinfections and head blight caused byH. sattvum on wheat. The input of<strong>the</strong>se chemicals in wheat productioncan be considered if <strong>the</strong> environmentalconditions are conducive to moderatedisease pressure only. Under suchconditions. susceptible cultivars can beprotected. However. under conditionsdUring which severe epidemics ofH. sattvum can be expected. <strong>the</strong> risk ofgrowing susceptible cultivars cannot beneutralized by relying on chemicaldisease control.In Zambia. <strong>the</strong> development of resistantcultivars which wUl yield well underdifferent wea<strong>the</strong>r conditions anddifferent disease pressures of H.sattvum wUl be <strong>the</strong> ultimate researchgoal. For rainfed wheat to become anacceptable crop to large and small-scalefarmers in a developing country. itshould not require <strong>the</strong> input ofchemicals to control foliar diseases andhead blight. seed treatment of rainfedwheat. on <strong>the</strong> o<strong>the</strong>r hand. Isrecommended to prevent seedlingdiseases caused by soil-bornepathogens. Systemic chemicals such asTriadimenol may also control early airborneinfections.

204Chemical Control ofWheat Diseases in <strong>the</strong> PhilippinesD.B. Lapis, Institute for Plant Breeding, University of <strong>the</strong>Philippines, Los BaAos, PhilippinesAbstractCommercial production of wheat has only been attempted in <strong>the</strong> Philippines in<strong>the</strong> 1980s. This has been triggered by <strong>the</strong> release of two varieties, Trigo 1 andTrigo 2. These cultivars have agronomic adaptation to <strong>the</strong> environmentalconditions of <strong>the</strong> country, but lack resistance to <strong>the</strong> major diseases. As <strong>the</strong>development of resistant cultivars takes time, chemicals have been evaluatedfordisease control when applied asfoliar sprays,forfrequency and rates ofapplicationfor leafspot control, as well asfor seed treatmentsfor protectingagainst and eradicating soil and seed-borne pathogens. Foliar sprays testedunder nursery conditions have shown that Tilt 250 EC is <strong>the</strong> most effectivechemicalfor controlling helminthosporium leaf spot. Some chemicals have alsoshown promise as protectants and eradicants ofseed-borne diseases; Homai.Vitavax-thiram, Vitavax-captan and Arasan are effective against Sclerotiumrolfsii. Rhizoctonia solani and FUsarium moniliforme. as well asfor seed-bornefungi.Although <strong>the</strong> Philippines has a longhistory of wheat cultivation, datingback as early as 1664, recentcommercial production has only beenattempted in <strong>the</strong> 19808. This attemptwas triggered by <strong>the</strong> release by <strong>the</strong>Philippine Seed Board of two wheatvarieties. UPLWI and UPLW2 (Trigo 1and Trigo 2). with good adaptation to<strong>the</strong> environmental conditions of <strong>the</strong>country. Unluckily. <strong>the</strong> two wheatvarieties lack resistance to majordiseases present in <strong>the</strong> Philippines.Faced with this situation. and realizingthat <strong>the</strong> development of resistantcultivars would be <strong>the</strong> most logical andeconomical approach to disease control,a breeding program has been begun.Since <strong>the</strong> development of resistantcultivars takes time. as an emergencymeasure chemicals were evaluated fordisease control in 1984. They weretested for use as foliar sprays and forfrequency and rates of application forleaf spot control. as well as for seedtreatments for protecting against anderadicating soil and seed-bornepathogens.Foliar sprays of chemicals undernursery conditions. using <strong>the</strong> microplottechnique. showed that <strong>the</strong> fungicidesCaltan F. Manzate D. Manzate 200.Orthocide 50 WP and Vinicur. at <strong>the</strong>irrecommended rates. and Tilt 250 EC. at0.4 and 0.6 ltlha formulated product(FP). were effective both as protectantsand as eradicants. compared with <strong>the</strong>control. Among <strong>the</strong>se chemicals. itappeared that Tilt 250 EC at <strong>the</strong> rate of0.6 ltlha FP was <strong>the</strong> most effectivechemical for controlling helminthosporiumleaf spot, with 24 and 14 meanlesion counts. as a protectant and aneradicant. respectively (Table 1). Thiswas fur<strong>the</strong>r corroborated with fieldexperiments; Tilt 250 EC at 0.6 It/ha FPgave 65% control and a yield of 1.5 tlhaversus <strong>the</strong> yield of <strong>the</strong> control at 0.9tlha (Table 2).

205Table 1. Mean number of lesions of helminthosporium leaf spot on wheat variety UPLW2with protectant and eradicant methods of spray applications under nursery conditions,Los Banos, Philippines, 1984FungicideTilt 250 ECOrthocide 50 WPCaltan FManzate 0Manzate 200Tilt 250 ECVinicurControlApplicationrate(FP/ha)!l0.6 It1.0 kg1.0 kg2.0 kg2.0 kg0.4 It1.0 ItLesion count,according.toapplication methodRlProtectantEradicant24 (25) 14 (56)26 (19) 20 (37)27 (16) 25 (21)27 (16) 17 (47)28 (12) 19(41)29 ( 9) 21 (34)30 ( 6) 20 (37)32 ( 0) 32 ( 0).!I FP = formulated product~/ Figures in brackets = percent controlTable 2. Yield and percent control of helminthosporium leaf spot of wheat varietyUPLW2 sprayed under field conditions, Los Banos, Philippines, 1984Applicationalate Yield PercentFungicide (FP/ha~ h/ha) controlTilt 250 EO 0.6 It 1.5 65Manzate 0 2.0 kg 1.3 56Manzate 200 2.0 kg 1.4 54Caltan F 2.0 It 1.5 53Orthocide 50 WP 1.0 kg 1.2 43Vinicur 1.0 kg 1.4 13Control 0.9 0.!/ FP = formulated product

206Results from this field experiment alsoindicate that <strong>the</strong> weight of seeds withblack point per 50 grams of seed wasless with Tilt 250 EC. which gave 3.63grams of seeds with black point. ascompared with 16.44 grams for <strong>the</strong>control (Table 3).The preliminary experiment on <strong>the</strong>effect of rate and frequency of chemicalapplications showed a smaller numberof lesions after spraying with DithaneM-45. as compared with Fungitoxsprayedplants and <strong>the</strong> control.Fur<strong>the</strong>rmore. <strong>the</strong>re was no difference indisease development with one or twospray applications. or at any rate ofapplication; an interaction between rateand frequency was only observed whenDithane M-45 was applied three times.Fungitox seemed to have no effect onhelminthosporium leaf spotdevelopment (Table 4).Homai and Vitavax-thiram. when usedas slurry at 2 glkg of seed, and Vitavaxcaptanand Arasan at 4 glkg. all seempromIsing for protecting seeds againstSclerotium rolfsii. Rhizoctonia solaniand Fusarium moniliforme. ascompared wIth <strong>the</strong> control (Table 5).Tests on <strong>the</strong> eradication of <strong>the</strong> morecommon seed-borne fungI. such asF. moniliforme. Curvularia spp.,Aspergillus spp., Helminthosporiumspp.• Penicillium spp.. Rhizophus spp.and Alternaria spp., using <strong>the</strong> samechemicals. rates and method ofapplication as above. showed that all of<strong>the</strong> chemicals tested were effective ineradIcating <strong>the</strong>se seed-borne pathogenson wheat seeds (Table 6).Table 3. Presence of black point on seeds of wheat variety UPLW2according to fungicide treatR'ent, Los Ballos, Philippines, 1984FungicideTilt 250 ECVinicurOrthocide 50 WPCaltan FManzate 200Manzate DControlAPplicatio~ate(FP/ha}!!0.6 It1.0 It1.5 kg2.0 It2.0 kg2.0 kgSeeds withblack point(g/50g seed)3.64.55.36.16.111.516.4~/ FP = formulated product

20'7Table 4. Effect on lelf spot infection of two fungicidelepplied at different rates andfrequenclel on when Vlrietv UPLW2, LOI WOI, Phillppln.., 1984Applicetion rite Number of Lelion PercentFungicide (FP/hl~' applle.tionl count controlDithane M-45 0.5 kg 1 23.3 62.62 22.0 63.13 8.9 85.71.0 kg 1 22.0 64.72 13.4 78.53 3.7 94.11.5 kg 1 23.9 I 61.62 14.7 76.53 3.0 95.2Fungitox 0.5 kg 1 76.9 -23.52 57.2 8.13 53.5 14.01.0 kg 1 62.7 - 0.62 55.8 10.43 71.9 -15.51.5 kg 1 101.3 -62.62 84.5 -35.63 67.2 - 8.0Control 62.3 0~I FP = formulated product

208Table 6. Protective effect of fungicides against three soil-borne pathogens, Los Banos"Philippines, 1984FungicidePercent germination oftreated seedsS. rolfsii R. solani F. moniliformeHomai 43.3 44.9 45.1Vitavax-thiram 44.4 43.9 44.5Vitavax-eaptan 41.4 43.3 44.1Arasan 76 42.8 40.9 43.6Control 36.9 38.7 38.9Table 6. Eradicative effect of fungicides on ..ed-bornepathogens on ..eds of wheat variety UPLW2, Los Banos,Philippines, 1984FungicideHomaiVitavax-eaptanVitavax-thiramArasan 75ControlPathogen-free ..ed~(%)46.829.214.29.00.0~/ Pathogens commonly encountered on untreated seedsare species of Fusarium, Curvalaria, Helminthosporium,Alternaria, Penicillium and Rhizophus

209III. AgronomyPhysiological Limitations to Producing Wheatin Semitropical and Tropical Environments andPossible Selection CriteriaR.A. Fischer, Division of Plant Industry, Commonwealth Scientificand Industrial Research Organization, Canberra, AustraliaAbstract''Tropica.l'' wheat environments are characterized by short winter photoPeriods(11 and 12.5 hours) with high temperatures, <strong>the</strong> mean temperaturefor <strong>the</strong>coolest month varyingfrom warm (l5°C) to hot (20°C) to very hot (25°C).Diurnal temperature range, solar radiation, vapor-pressure deficit and watersupply (irrigated or rainfed) vary considerably between regions:frosts and hotwinds constitute meteorological hazards in some locations. In suchenvironments, wheat may establish poorly because of high soil temperatures.More seriously, development is accelerated (approximately in proportion totemperature), while growth rate is stable or may decline, so that leaf size,tillering, spike size and yield potential suffer, even under irrigation. Excessiverespiration and possible direct effects of high temperature on sinkformationmayfur<strong>the</strong>r reduce potential, while kernelfilling is curtailed by hasteneddevelopment and/or carbohydrate shortage. There is little physiologicalexperience with wheat at high temPeratures, but some o<strong>the</strong>r plant genera showremarkable <strong>the</strong>rmal adaptation. It is possible to leng<strong>the</strong>n <strong>the</strong> seeding-tofloweringinterval in wheat with daylength and cold-sensitivity genes, <strong>the</strong>rebyincreasing biomass production. Selecting in such materialfor harvest index(currently very low) would seem a rational physiological approachforimprovement of yield potential. In order to avoid high temperatures at criticalstages, and to maximize water-use efficiency, it is desirable to have seeding dateand cultivar maturity class such thatflowering is around <strong>the</strong> coolest point of <strong>the</strong>year and, if <strong>the</strong> crop is rainfed, subsoil moisture reserves arefully explotted.Crop research comprises <strong>the</strong>complementary activities of adaptingenvironments to plants, and adaptingplants to environments. At first glance,<strong>the</strong>re is not much that agronomists cando about <strong>the</strong> <strong>the</strong>rmal regimes of <strong>the</strong>tropics, but genotypic adaptation tosuch conditions may offer possibilitiesto plant breeding. Genotypic adaptationto superoptimal temperatures is also ofinterest to physiologists; ecophysiologistsalready recognize manyadaptations to hot regimes in o<strong>the</strong>rplants (37). The tropics being a newenvironment for wheat. it might permiteasier prediction of advances than <strong>the</strong>well-trodden field of geneticimprovement in more temperate areas.In this paper. important features ofwheat climates in <strong>the</strong> tropics and ofyield determination in wheat will besummarized, before passing to specificphysiological problems of tropicalwheat and possible genotypicadaptations. Possible selection criteriaand interactions with agronomy wUlalso be discussed. Disease and weedfreeconditions and adequate fertilitywill be assumed. The indulgence isasked of researchers in <strong>the</strong> tropics for<strong>the</strong> author's haVing ventured fromtemperate agriculture into a field inwhich he has had little researchexperience.

210Climatic CODsideratloDsTable 1 is a summary of wheat climatesin <strong>the</strong> region within 23 degrees northand south of <strong>the</strong> equator and below1500 meters in altitude; Dhaka (24°Nlatitude) is included because of <strong>the</strong>importance of wheat in Bangladesh. Itis assumed that wheat is grown in <strong>the</strong>winter and that <strong>the</strong> temperature inJanuary (or July in <strong>the</strong> sou<strong>the</strong>rnhemisphere), almost always <strong>the</strong> coolestmonth. is <strong>the</strong> simplest and mostrelevant climatic feature. Thus.January mean temperatures above22.5°C are considered very hot. thosebetween 22.5 and 17.5°C hot. andthose between 17.5 and 12.5°C warm.giving three regimes with meantemperatures of about 25. 20 and 15°C.respectively. These are fur<strong>the</strong>r divided.according to January atmospherichumidity. into humid (With estimatedaverage leaf-to-air vapor pressure deficit(VPD) being below about 10 mb) anddry (VPD above 10 mb); dew is unlikelyto form in <strong>the</strong> latter case. A fourth highlatitudewarm regime (25 to 30°C), isincluded because several majortraditional low-latitude. wheat-grOWingregions are represented and arerelevant to this conference.The range between mean maximumand mean minimum temperatures isgiven in Table 1. for it may be directlyrelevant to crop growth and can beused to calculate mean minimumtemperatures, which is relevant tovernalization. and which some studiessuggest may be more closely correlatedto crop performance than meantemperature (25. C.E. Mann. personalcommunication). The temperaturerange tends to be least at humid coastallocations. Information on solar radiationis, unfortunately. not always availableor accurate; January radiationdecreases with distance from <strong>the</strong>equator. with cloudiness (In humidlocations) and with dust haze (e.g.•nor<strong>the</strong>rn Nigeria). Seasonal changes intemperature. radiation and vaporpressuredeficit for October to April(April to October in <strong>the</strong> sou<strong>the</strong>rnhemisphere) are shown forrepresentative locations in Figure 1.Winter rainfall totals in Table 1 are aninadequate deSCription of water supplyto <strong>the</strong> crop. In few places is <strong>the</strong>resufficient rainfall dUring <strong>the</strong> cropseason for viable cropping (e.g..possibly in IndoneSia. sou<strong>the</strong>rn China.Paraguay and sou<strong>the</strong>rn Brazil). Moregenerally. crops rely on soil waterstored from <strong>the</strong> summer wet season indeep retentive soils (e.g.. central India.Bangladesh. Thailand and Queensland.Australia). and/or on irrlgatlon.Irrigation is essential in places likeSudan and Nigeria and. for reasons ofsoil type. in central Brazil. Thus. watersupplyregimes dominated by irrlgatlon.stored soil water or. less commonly.rain on <strong>the</strong> crop need to bedistinguished.This brief discussion of climate has nottaken into consideration severalmeteorological factors of lesserimportance to tropical wheat. Theseinclude sun angles and mid-dayradiation intensity, potential or panevaporation rates. <strong>the</strong> sharpness of <strong>the</strong>post.January air-temperature rise and<strong>the</strong> incidence of frost and severe dryWinds. Frost occurs only in <strong>the</strong> warmregime; this can be quite significant insou<strong>the</strong>rn Brazil and Queensland. Severeatmospheric drought is apparentlysignificant at locations bordering <strong>the</strong>Sahara.

Table 1. Actual and pouible wheat1lrowing locations in and near <strong>the</strong> tropics, and principal features of <strong>the</strong>ir temperature andhumidity regimes in <strong>the</strong> month of January (July in <strong>the</strong> sou<strong>the</strong>rn hemisphere)Mell'l daily January wea<strong>the</strong>rTotal rainMean Temp. Solar Dec.- Locations withThermal and Location Latitude Altitude tamp. range VPD radiation Feb. Annual approx. similarhumidity regime (ml (OCI (OCI (mb) (MJ/m2/dl (mm) (mml wheat climatesVery hot, humid Los Bal'los, Philippines 14 0 N 40 24 5 6 15 230 2040 Jakarta, IndonesiaPhitsanulok, Thailand 17 0 N 50 25 14 8 - 32 1354Very hot, dry Khartoum, Sudan 16°N 380 24 16 22 20 0 164Kununurra, Australia 170S 30 23 11 19 21 5 145Hot, humid Chiang Mai, Thailand 18°N 313 21 16 6 - 28 1246 Mandalay, BurmaDhaka, Bangladesh 24~ 8 19 14 6 15 51 1928 PQza Rica, MexicoFormosa, Brazil 160S 911 19 14 8 - 17 1595 Villa Guede, SenegalSanta Cruz, BoliviaAsunci60, ParaguayHot, dry Kano, Nigeria 12 0 N 410 22 17 20 21 1 813 Hyderabad, India (1)Indore, India 23 0 N 555 18 11 12 18 16 816 Taiz, Yemen Rep.Tlaltizapan, MexicoWarm,humid Lima, Peru 120S 11 15 4 1 21 5 10 Lusaka, ZambiaEmerald, Australia 230S 179 15 16 5 - 108 591 Londrina, BrazilHarare, Zimbabwe 180S 1410 14 15 1 18 9 868 Matamoros, MexicoCanton, China 23 0 N 18 14 9 4 - 126 1720Warm, humid Riyadh, Saudi Arabia 25 0 N 594 15 14 6 - 42 105 New Delhi, India(25-30 0 lat.l Ciudad Obregon, Mexico 21 0 N 40 15 16 3 13 40 261 Kufra, LibyaPasso Fundo, Brazil 280S 750 13 - - - 445 - Cairo, Egyptl!~

212Yield Determination in WheatTable 2 outlines an approach tounderstanding yield determination inwheat. This emphasizes crop and spikegrowth (dry matter accumulation interms of glm2) in a critical period(spike-growth period) leading up toan<strong>the</strong>sis as <strong>the</strong> key to determination ofgrainslm2; little importance is given totraditional numerical components ofgrain number (17).35G 30Cl>.--~~ ...l:: ::so «l 258 t~Q.,~~ 20o Khartown []Indore• Los Bafios • DakhadelANOA Harare1530~-8 25gl:: 20~~ 154030:c §~ 2010... ..0.............,,0"'",....c--__ ---0-__ ,--"a"/:I_--'--- {J-- - ---- -0' ... ::""...:::::-........... -1:-- . --- '. t::-·- __ ~...:s=vcc... ~ ::.- -.-.-:-.::::::::': _" ~- _' _. _ ... .~.""" •'--'-. -A--'--"Oct Nov Dec. JanMonthFeb Mar AprFigure 1. Long-term mean monthly temperature, daily radiation andestimated leaf-to-air vapor pressure deficit (VPD) for key tropical locations(VPD was estimated assuming <strong>the</strong> leaf was at <strong>the</strong> mean daily temperature).Months for Harare, Zimbabwe, should read April to October.

213Table 2. Wheat yield determination and <strong>the</strong> influence of environment and genotype in <strong>the</strong>absence of nutrient limitationComponents and subcomponents1. Developmental periods (final stage)Vegetative (floral initiation)Spikelet and floret initiation(penultimate leaf emergence)Spike growth (an<strong>the</strong>sis)Grain filling (loss of green)2. Crop growth to give leaf areaindex at onset of spi~e growthEstablished plants/mDurationRelative growth rate3. Spike growth to give g/m 2 at an<strong>the</strong>sisLeaf area index, prevailingdurationNet photosyn<strong>the</strong>tic ratePartitioning to spike4. Processes around an<strong>the</strong>sis to give grains/m 2at onset of grain fillSpike weight at an<strong>the</strong>sisFlorets/spike weightGrains per floret (grain set)~5. Individual grain weight determinationCell number, durationFilling durationRate of filling:Reserves, kernel numberLeaf area index prevail ingNet photosyn<strong>the</strong>tic rate6. Grain yield (if no water shortage)Grain numberIndividual grain weight7. Grain protein 0/0Grain nitrogen 0/0Controlling factort!lMajorT,V,P,GT,P,GTTT,GT, R,WPrevious period, WTRGPrevious periodG"T,RTPrevious periodPrevious period, W, TRQ during spike growthT during grain fillingTMinorP,GT,WGTGT,DW,RT,G,DT,DW,G,E,I T =temperature, V = vernalizing cold, P = photoperiod, R =solar radiation, W = watershortage, D = vapor-pressure deficit, Q = photo<strong>the</strong>rmal quotient, G = genotype

214Briefly. plant development (<strong>the</strong> firstcomponent in Table 2) proceedsthrough four phases or periods.delineated by <strong>the</strong> successive discretestages of noral initiation, penultimateleaf emergence on <strong>the</strong> main shoot(approximate gUide to <strong>the</strong> onset of spikegrowth). an<strong>the</strong>sis and loss of green in<strong>the</strong> spike. Control of <strong>the</strong> duration ofeach period by <strong>the</strong> listed environmentalfactors and by genotype is reasonablywell understood. These stages are bestconsidered as representing switches in<strong>the</strong> allocation of assimilate or drymatter between different organs. First.<strong>the</strong> crop grows leaves and roots and. in<strong>the</strong> second period, stems as well. In <strong>the</strong>third period, commencing some 20 to30 days before an<strong>the</strong>sis, spikes andstems become <strong>the</strong> major sinks forassimilate; in <strong>the</strong> final period. grainsare <strong>the</strong> dominant sink.The second component in Table 2refers to <strong>the</strong> build-up of <strong>the</strong> leaf area inperiods one and two. Leaf area at <strong>the</strong>end of period two plays a major role indetermining spike growth (component3), a role best summarized in <strong>the</strong>percentage of solar radiationintercepted by leaves dUring <strong>the</strong> spikegrowth period which, along withphotosyn<strong>the</strong>tic rate and periodduration, determine total crop growthin <strong>the</strong> period. Approximately 25 to 50%(depending on cultivar) of this total dryweight at an<strong>the</strong>sis is considered pivotalin this analysis, because a giveninvestment in spike tissue (rachis,awns, floral parts, etc.) is necessary tobuild a competent floret (approximately10 mg. depending on <strong>the</strong> cultivar)., Therefore. spike dry weight determinespotential grain number; some environmentaland possibly genotypic factorsaround an<strong>the</strong>sis (component 4) can, intum, affect actual grain number byreducing grain set (grain per floret) toless than <strong>the</strong> <strong>the</strong>oretical maximum ofone.Understanding individual grain-weightdetermination follows more broadlyaccepted lines [component 5);conditions soon after an<strong>the</strong>sis maydetermine potential grain weight, butoften limitations on <strong>the</strong> duration and/orrate of grain filling affect <strong>the</strong> realizationof this potential, with final grain weightfalling below potential, especially if<strong>the</strong>re are many grains to be filled.In situations without water limitation,for a given an<strong>the</strong>sis date, a simple yieldindex can be derived which integrates<strong>the</strong> major environmental effects listedin Table 2. This relies on <strong>the</strong> fact thatgrain number is reasonably wellpredicted by <strong>the</strong> photo<strong>the</strong>rmal quotientover <strong>the</strong> 20 to 30 days precedingan<strong>the</strong>sis (17,27). Photo<strong>the</strong>rmal quotient(Q) is defined as mean solar radiationdivided by mean temperature less4.5°C (units of MJ/m2/d/degree). Itspecifically integrates <strong>the</strong> positive andlinear effect of radiation on crop growthrate and of mean temperature (less basetemperature) on developmental rate(reciprocal of duration). Hence, asdefined, it is an index of total cropgrowth in <strong>the</strong> approximate spikegrowthperiod. It can be improved bycorrecting for incomplete radiationinterception (<strong>the</strong>reby reducing Q) insituations where leaf-area index isinsufficient in this period for full lightinterception (e.g., ~3).The relationship of grain number tocorrected Q (and to total dry weight atan<strong>the</strong>sis) for a set of representativecultivars and a range of sowing datesand sites in central Mexico (20°Nlatitude) is shown in Figure 2; PozaRica and Tlaltizapan have hot andhumid and hot and dry tropicalregimes, respectively. A similarrelationship was derived from a widerange of sowing dates and years at <strong>the</strong>CIANO station in Ciudad Obregon innorthwest MexiCO (R.A. Fischer,

216unpublished). A role of thumb derivedfrom this work suggests <strong>the</strong> followingsimple relationship for good growingconditions and semidwarf cultivars:Grain number/m2 = 11.000 xcorrected Q (Equation 1)At <strong>the</strong> same time. in many studies (i.e..39). individual grain weight appears tobear a consistent negative linearrelationship to grain-fi1l1ng temperature.This relationship could not be derivedin central Mexico because of diseaseattack during grain filling at severalC'iIi~~2016100AAA•Be6 @>00.6 1.0 1.6Corrected Photo<strong>the</strong>rmal Quotient(Mj/m2/degree)2.0OPoza Rica.. TlaltlzaPaneEl Batan• Toluca•AAA600 '7150 1000 12CK)TWA (gIm2)I'tpre 2. The r.latioa....p of.......,..2 to a) corrected photo<strong>the</strong>rmalquotient ID <strong>the</strong> 30 4&,.. before &a<strong>the</strong>". (Me teu) &ad b) total drJ' welptat ath..... Kuala are <strong>the</strong> a••ace of 10 to 19 '.Dotype. Mwa at foar"tea ill ceDtralll.zlco (aboat 20-1f lat). Pou Rica (80 ID). TIa1tlApaa (940ID). &1 BataD (2249 ID) ad Toluca (2840 ID).8oarce: IIldJDore et ale (27)

216sites. but field work at CIANO (15) andelsewhere suggests <strong>the</strong> followingrelationship, as shown forrepresentative cultivars (Figure 3):Grain weight (mg) = 64-1.6 x T(Equation 2)Here T is <strong>the</strong> mean temperature duringgrain filling (30 to 40 days followingan<strong>the</strong>sis).Equations 1 and 2 can be multiplied togive <strong>the</strong> aforementioned simple index ofgrain yield:Yield (g/m2) = corrected Q x(700-17 x T) (Equation 3)This equation contains <strong>the</strong> two majornegative influences of increasedtemperature on grain yield. namely thatof temperature on duration of <strong>the</strong> spikegrowth period and on grain weight.Increased radiation, through Q. has apositive effect on yield.It is possible to use Equation 3 toestimate grain yield as a function ofan<strong>the</strong>sis date for <strong>the</strong> locations inFigure 1 (Table 3). Q was calculated for<strong>the</strong> month prior to an<strong>the</strong>sis. assumingfull light interception, and T for <strong>the</strong>month after. Q tends to peak inFebruary (August in <strong>the</strong> sou<strong>the</strong>rnhemisphere). but <strong>the</strong> steepness withwhich T rises before and. especially.after January also influences an<strong>the</strong>sisdate for maximum yield (Figure 5). Thisis seen to be January at all tropicallocations except Los Banos. Philippines.where temperature changes less40......t::'c./)....Il)~l::~ ....d3020DOPoza Rica...TlaltizapanDEI Batan"'Toluca0o... ...... ...... ....... ...... ... .............ooo16 18 20 22Mean filling temperature (0C)24 26Figure 3. The relationship of individual grain dr.y weight to mean grainfiningtemperature for <strong>the</strong> sowings of Figure 2, and <strong>the</strong> linear relationshipderived from disease-free sowings at CIANO, Ciudad Obregon, Mexico.Source: R.A. Fischer, unpublished

217seasonally and cloudiness persists into<strong>the</strong> early winter (Figure 1). Thegenerally lower yield of hotter and morehumid (cloudy) locations is evident inTable 3.Finally. although yield is reducedbecause high temperatures hastendevelopment. it should be rememberedthat. where radiation is high, crops canbe quite efficient in terms of yield perday from sowing to harvest. Bestgenotypes achieved 50 kg/hald atTlaltizapan in central Mexico (27) and40 kg/hald at Kununurra innorthwestern Australia (6).A yield index for water-limitedenvironments might be derived alongsimilar lines to those above.emphasizing <strong>the</strong> effect of water ongrain number in <strong>the</strong> critical periodaround an<strong>the</strong>sis. as has been done byWoodruff (47). However, a moregeneral. simple index. discussedelsewhere (16,28), relies on <strong>the</strong>inevitable link between photosyn<strong>the</strong>sisand transpiration:Yield (g/m2) = transpiration xWUE x HI (Equation 4)Transpiration (mm) refers to total croptranspiration. WUE to water-useeffiCiency (g/m2/mm); HI is harvestindex. or <strong>the</strong> ratio of grain to total drymatter produced. The major effect ofwater limitation is <strong>the</strong> reduction of cropTable 3. Eswated grain yield (dry weight) for well-watered wheat crops as estimated byequation 3- using monthly long-term radiation and temperature averages for key locationsGrain yield (g/m 2 ) according to an<strong>the</strong>sis date~./Location Nov.' Dec.' Jan. , Feb. , Mar.' Apr.' May'Los Banos, Philippines 159 163 156 183 226 216 215(very hot, humid)Khartoum, Sudan 168 234 273 277 249 179(very hot, dry)Dhaka, Bangladesh 220 324 361 374 298 218 185(hot, humid)Indore, India 362 469 492 461 387 238(hot, dry)Harare, Zimbabwe..£1 685 813 892 sl1 834 QI 726 531 490(warm, humid)CIANO, Cd. Obregon, 324 394 472 526 575 542 438Mexico (warm, humid,25-30 0 lat.)~j Yield (g/m 2 ) = corrected Q x (700-17 x T)E. IMaximum yields are underlined~ Read May 1 to November 1!11 Ignores possible frost damage

218transpiration which. in any case. mightbe only 50 to 70% of evapotranspiration(soll evaporation + crop transpiration)dUring <strong>the</strong> crop cycle. There may be areduction in harvest index if <strong>the</strong>temporal distribution of croptranspiration is unbalanced: forexample. post an<strong>the</strong>sis transpirationfalling below 30% of total transpiration.A strength of this approach is that WUEis closely governed by one factor.namely <strong>the</strong> preVailing leaf-to-air vaporpressure deficit (VPD in Table I andFigure-I). The follOWing relationshiphas been suggested for wheat (34):WUE (glm2/mm) = 50NPD(mb)(Equation 5)The importance of VPD where watersupply is limited is now evident: at highVPD. crop transpiration acquires lessC02 (dry matter) than at low VPD. Theo<strong>the</strong>r major effects of high temperature.represented in Equation 3. must alsooperate under water limitation unless<strong>the</strong> latter is severe. Their incorporationinto Equation 4 is not simple. but isbest considered in terms of effects ontotal transpiration: this may decreaserelative to water supply under hotterconditions (crop duration is reduced)and relative to evapotranspiration (soilevaporation increases due to generallylower ground cover). Because mostwater-limited wheat in <strong>the</strong> tropics isgrown on stored soll water. thissituation will be discussed. Thisdiscussion will be brief. as possibly <strong>the</strong>only unique aspect of stored soil watersin <strong>the</strong> tropics is <strong>the</strong> probable existenceof increasing soil water with depth in<strong>the</strong> profile. due to <strong>the</strong> large water inputduring <strong>the</strong> wet summer season.Queensland. Australia is an exceptionin this regard (Woodruff. <strong>the</strong>seproceedings). Many aspects of <strong>the</strong>difficult task of selection for adaptationto water limitation are discussedelsewhere (16.20).Specific Limitationsin <strong>the</strong> TropicsThe preceding general discussion. and<strong>the</strong> simple derived relationships. haveindicated major mechanisms by whichtropical conditions (highertemperatures. sometimes higher VPDsor lower radiation) can reduce wheatyield: <strong>the</strong>y prOVide an invaluableframework for fur<strong>the</strong>r discussion.However. <strong>the</strong> general approach has notbeen Widely tested or researched underhot conditions. Fur<strong>the</strong>rmore. a numberof minor mechanisms have been passedover which conjecture or experience.and sometimes solid research. suggestcould also be specifically relevant to <strong>the</strong>tropics. The ensuing discussion willdeal with both of <strong>the</strong>se issues. as itproceeds stepWise through <strong>the</strong>components of Table 2 and searches forpossible genotypic adaptations totropical environments.Acceleration of developmentby high temperaturesNotWithstanding some doubts about <strong>the</strong>actual temperature of <strong>the</strong> grOWing pointrelative to air temperature (it could behotter when close to <strong>the</strong> soil surface orcooler when higher and cooled bytranspiration). <strong>the</strong> acceleration ofdevelopment as air temperature rises iscentral to yield reduction. Themechanisms are not understood. butare obViously a very fundamentalresponse of plants. Quantitatively. <strong>the</strong>responses (within upper and lowerlimits) fit <strong>the</strong> simple day degreerelationship:(T-Tb) x duration = constant(Equation 6)T is temperature. Tb is basetemperature (for zero rate ofdevelopment) and duration is <strong>the</strong> lengthin days: <strong>the</strong> constant is <strong>the</strong> length. inday degrees. of <strong>the</strong> particulardevelopment period underconsideration. In wheat. Tb appears torise from around 2°C for early

219developmental periods. to around goCfor grain filling (3.36). The relationshipImplies that duration declines lessrelatively and absolutely astemperature rises (e.g.. ifTb = 5. <strong>the</strong>acceleration from 15 to 20°C will be33%. that from 20 to 25°C. only 25%).Although data for wheat attemperatures above 20°C Is scarce. Itdoes show this tendency for duration tobe reduced less at temperatures above20 to 25°C and sometimes but notalways (35.39). to approach a minimumvalue (3.26); this fact Is not predictedby Equation 5 and is worthy of fur<strong>the</strong>rInvestigation.Although Tb and. hence. <strong>the</strong> sensitivityof duration to temperature. variesbetween species for given developmentalphases (2). <strong>the</strong>re Is no evidence ofgenotypic variation within wheat. In anycase. it Is not so much <strong>the</strong> accelerationof development with higher temperaturewhich Is critical. but ra<strong>the</strong>r <strong>the</strong> actualduration reached under hot conditions.Three mechanisms exist by whichlonger duration under hot conditionscan come about. The most striking oneIs vemaUzation sensitivity. wherebydevelopment in <strong>the</strong> first and. to a limitedextent. <strong>the</strong> second. but not laterdevelopmental periods (Table 2). Isslowed when <strong>the</strong> sensitive genotypeexperiences no vernalizing cold (26.40);<strong>the</strong> universal effect of highertemperature apparently Is overridden(Figure 4). Vernalization in this contextappears to operate with minimumtemperatures below about 13°C.increasing in intensity down to aminimum of 2 to 8°C (23). In so-calledspring wheats. a small number of genesprobably control vemaUzationresponsiveness; however. <strong>the</strong>re appearsto be a continuous gradient inresponsiveness. Pitic 62. Cajeme 71.Gabo. Odzi. Soltane. Oxley and C306 arecultivars with moderate responsiveness.The second mechanism leading to longduration in all periods before an<strong>the</strong>sis.even under hot tropical conditions. Isseen WIth genotypes such as Manitouand Era. which are highly sensitive tophotoperiod (Figure 4). With moderatelysensitive ones (e.g.• Kloka and Anza).<strong>the</strong>re is a smaller but still signtflcanteffect. Sensitivity to photoperiod Isunder simple genetic control.FInally. It can be suggested thatsignificant variation In pre-an<strong>the</strong>slsduration exists under hot conditions.even in cultivars Insensitive tovernalization and minimally sensitive tophotoperiod (this might be conSidered asgenotypic variation in <strong>the</strong> day degreeconstant of Equation 6). A comparison ofSiete Cerros and Hira. both insensitivecultivars. shows that Siete Cerros has aconsistently longer sowmg-to-an<strong>the</strong>slsduration (61 days versus 51 days. +20%) at sowmgs at hot sites in centralMexico (25). O<strong>the</strong>r workers have alsopointed to <strong>the</strong> relative lateness ofSieteCerros or Kalyansona. which appears tobe associated with <strong>the</strong>ir tendency toproduce an extra leaf on <strong>the</strong> main stem(25. H.M. Rawson. personalcommunication).WhUe difTerences in vernalization andphotoperiod sensitivity do not operatein <strong>the</strong> grain-filling period (Figure 4).small genotypic differences (20%) Induration under hot conditions do occurand should be likened again todifferences in <strong>the</strong> constant value inEquation 6. Also. larger differences(35%) reported for o<strong>the</strong>r cultivars undercooler conditions should persist in arelative sense under hot ones (35).Accelerated leaf senescence Is ano<strong>the</strong>raspect of <strong>the</strong> high temperature-rapiddevelopment syndrome. This Is not wellunderstood. and may not be a totallynegative effect; for example. leavesmust senesce if all of <strong>the</strong>ir nitrogen is tobe mobUtzed into growing grains. Evenso. ifa phenomenon such as <strong>the</strong>genetically controlled delayed leafsenescence in soybeans (29) were to befound in wheat. It might be especiallyuseful under hot gram-mUngconditions.

22070 0~ A: ~>. ··A ~ 50~'0 :"A... 60 /1 8ll)f/JA-.'//0....ll)... / f/J \.!I:: ll)A .......•• ..••·•[]-...................·······A··· ..•....a ..." .c: 0p" D·..... .'/ ... 'A~.......... .;...50 a 40 0,ca... _/ ,.....~l::: ,0 ... ,• ll)ll)"'" 40... ... ......0 • =~ 300 ,ell) 0., - \"" • E....• .~''QI)dca30 d- ..... o •........-~ -0rJ)20 2010 20 15 20Mean minimum temperature (OC)Temperature (0C)ll)Eo-

221Growth at high temperaturesEarly stages-Plant population is <strong>the</strong>starting point of crop growth. Theeffects of initial density on crop growthrate qUickly diminish with time undergood growing conditions. such as highradiation and water aVailability (13).because of compensatory mechanisms.Midmore's study (25) showed reducedtotal dry matter at an<strong>the</strong>sis (55 daysafter sowing) under hot. low radiationconditions of Poza Rica. Mexico. only ifinitial plant density fell below 100/m2.Such a population may not be easy toachieve in <strong>the</strong> tropics. because ofrapidly receding soil moisture and highsoil temperatures. Maximum soiltemperatures in <strong>the</strong> top few centimeterswill exceed maximum air temperatureby 10 to 15°C if <strong>the</strong> soil surface is bareand dry and radiation intensity high.Maximum soil temperatures could.under <strong>the</strong>se conditions. exceed 45 to50°C at many locations. with probablyserious effects on seedling emergence.Agronomic management (mulching.deep furrow planting) offers <strong>the</strong> bestsolution to this problem. but <strong>the</strong>recould also be useful genotypicvariability.Even when seedlings emergesatisfactorily. brief exposure to extremesoil temperatures may have long-termdeleterious effects on growth potential.for example. direct inhibition of crownroot or tiller initiation (H.M. Rawson.personal communication). Suchpossibilities have been inadequatelyresearched and. again. agronomicsolutions would seem most relevant.Never<strong>the</strong>less. resistance tometabolically disruptive effects ofextreme temperatures (temperaturelesions) is a trait for which most speciesstudied show considerable and oftensimply inherited genetic variation (24).Photosyn<strong>the</strong>sis and respiration-Leaftemperature over <strong>the</strong> range of 20 to35°C has remarkably little effect«10%) on <strong>the</strong> gross rate ofphotosyn<strong>the</strong>sis by wheat leaves (39);this has also been demonstrated forwheat leaves grown at differenttemperatures (5.12). The point at whichphotosyn<strong>the</strong>sis of acclimated wheatleaves is seriously disrupted by hightemperature is probably above 40°C.Remembering that leaf temperature isusually several degrees below airtemperature if water supply isadequate. it is <strong>the</strong>refore unlikely thattropical temperatures per se inhibitwheat photosyn<strong>the</strong>sis. With waterstress. photosyn<strong>the</strong>sis may well beinhibited. but <strong>the</strong> major cause will be<strong>the</strong> lack of water and not temperature;<strong>the</strong> key question is whe<strong>the</strong>r water-useefficiency ra<strong>the</strong>r than photosyn<strong>the</strong>ticrate changes (which is unlikely).Recent research suggests that. quiteindependently of leaf water status ortemperature. stomatal conductance inmany species is linearly and negativelyrelated to VPD. In <strong>the</strong> case of wheat atleast. leaf photosyn<strong>the</strong>sis appearsunaffected with VPD up to 25 mbconductance (30). Considerably higherVPD levels would be reached at middayin dry tropical locations; <strong>the</strong> effect onphotosyn<strong>the</strong>sis is not known.In contrast to gross photosyn<strong>the</strong>sis.respiration increases markedly as 'temperature rises. Theory suggests that<strong>the</strong> growth component of respiration(respiratory cost of syn<strong>the</strong>siZing newplant constituents) is unaffected.whereas <strong>the</strong> maintenance componentresponds to temperature. Dailymaintenance respiration is convenientlyexpressed as a fraction (m) of totalbiomass. While measurementsinvolVing short-term temperaturechanges suggest that m has a Q10 ofaround 2 (i.e.• it doubles for each 10°Crise). <strong>the</strong> responsiveness of wheat m tolonger-term changes is probably less(39). Also. m probably declines steadilyfrom <strong>the</strong> early vegetative stage tomaturity. as <strong>the</strong> proportion of structuraland dead biomass increases (21).Unfortunately. <strong>the</strong>re is no reliablemeasure of m at an<strong>the</strong>sis under hot

222conditions. but <strong>the</strong>ory suggests about0.02 glgld at 25°C. This means that 2%of <strong>the</strong> crop biomass is respired inmaintenance dailY' or. with 500 glm2biomass. 10 glm2/d is lost. In thiscontext. it is intriguing that genotypicvariation in maintenance respirationhas been found in ryegrass andexploited in a selection program. toproduce a low-respiring. high growthratecultivar (46). A project to look forsuch variation in wheat. specificallyunder hot conditions. has beencommenced by H.M. Rawson inAustralia.Leafarea productton-The investmentof photosynthate into new leaves or <strong>the</strong>leaf-area ratio (cm2 per g plant dryweight) is a key factor determiningearly crop growth rate. especially whenleaf-area index is low and new leaves donot shade existing ones. Onecomponent of this. <strong>the</strong> leaf-weight ratioor proportion of dry weight in leavesrelative to total dry weight. does notappear to be greatly affected by meantemperatures from 10 to 25 or 30°Cand may even increase. o<strong>the</strong>r thingsremaining equal. The secondcomponent of this investment. namelyleaf area per unit leaf weight. actuallyincreases with higher temperatures upto 25°C. and is greater with lowerradiation (12.18.27). It appears.<strong>the</strong>refore. that green leaf·areaproduction as a proportion of daily drymatter gain is. if anything. improved bygrowth under tropical conditions. and isunlikely to limit performance. Oneproviso is that temperatures not behigh enough to inhibit chlorophyllproduction. a phenomenon seen incertain genotypes (18) and readilyselected against. Also a more completeand longer-term analysis of leaf-areadynamics must include <strong>the</strong> accelerationof leaf senescence under hot conditionsas mentioned earlier.Overall crop growth-Relative growthrate (daily dry matter increase per unittotal dry weight) integrates effects ofenvironment on photosyn<strong>the</strong>sis.respiration and leaf area ratio. It is auseful index of early crop growth rate.before mutual shading and ontogeneticchanges begin to dominate relativegrowth rate. Evans and Bush (10).working under field radiation levels in<strong>the</strong> Canberra. Australia. phytotron.recently found early relative growthrate of wheat to peak at 20 to 25°C.with only small declines down to 12°Cand up to 33°C. This represents quiteremarkable <strong>the</strong>rmal stability. Limitedresults (18) suggest that early growth ata given mean temperature is somewhatgreater with a narrower diurnaltemperature range. a response whichwould favor <strong>the</strong> humid tropicallocations. Genotypic differences in <strong>the</strong>various components of relative growthrate may exist. but <strong>the</strong>y would seem oflimited relevance to performance in <strong>the</strong>tropics. since relative growth rate doesnot suffer markedly under suchconditions. and because of <strong>the</strong>possibility of compensating forlimitations in early growth byincreasing plant population.Crop growth rate. once leaf-area indexis high enough for substantial mutualshading (i.e.• ::-1.0). is best consideredin terms of total radiation interceptedby green leaves. Under a wide range ofconditions. notWithstanding possibleeffects on photosyn<strong>the</strong>tic efficiency andon maintenance respiration. <strong>the</strong> ratio ofdry matter accumulation to radiationinput is relatively constant for wheat ataround 3 glMJ of photosyn<strong>the</strong>ticallyactive radiation absorbed by greenleaves (17.39).This implies growth at 1.2 glMJincident total solar radiation with fullground cover (100% interception). e.g..if daily solar radiation is 20 MJ/m2/d.light-limited growth rate should be 24glm2/d. This relationship has not beentested at temperatures above 20°C or athigh radiation intensities typical of <strong>the</strong>tropics; however. unless maintenancerespiration estimates are seriously inerror. it should apply reasonably well.

CertainlY crop growth rates in excess of20 glm'Z/d have been recorded at hottropical sites, such as Tlaltlzapan,Mexico (27), and <strong>the</strong> low veldt ofZimbabwe (8). Peak rates were lower atPoza Rica, Mexico (10 glm2/d), probablydue to <strong>the</strong> lower radiation and leaf areaindices (27). There, and at Tlaltlzapan.greater leaf area indices and dry matterat an<strong>the</strong>sis were achieved with latervernalization and photoperiod-sensitivegenotypes. Although <strong>the</strong>ir crop growthrates were somewhat lower than earliergenotypes, lateness seems to be a clearway of increasing total growth atan<strong>the</strong>sis (45) and growth rate during<strong>the</strong> pre-an<strong>the</strong>sis spike-growth periodunder hot conditions where leaf areaindices in earlier types fail to reach fulllight interception.Red1lcttoD lD gralD DamberIt was proposed in <strong>the</strong> generaldiscussion of yield determination thatgrain number is reduced under hotconditions, essentially because cropgrowth and, hence, spike growth during<strong>the</strong> spike-growth period is limited by<strong>the</strong> shortened duration of <strong>the</strong> period.Possibly leaf-area indices are alsoinsufficient to intercept all radiation,essentially a consequence of reductionsin duration of earlier periods. Thisappeared to be <strong>the</strong> case in a study ofcrop heating at CIANO, CiudadObregon, Mexico (14); grain numberreductions were closely related toreductions in spike dry weight at highertemperatures and in tropical locations.Additional mechanisms by which grainnumber is reduced at highertemperatures and in tropical locationsare alluded to in Table 2.Partittoning ofdry weight to <strong>the</strong>spike-At Tlaltlzapan and, especially, atPoza Rica in Midmore's study in Mexico(27), late cultivars sensitive tovernalization or photoperiod producedfew gratnslm2 relative to dry weight atan<strong>the</strong>sis; <strong>the</strong>se were precisely <strong>the</strong>cultivars which produced most growthat an<strong>the</strong>sis. The problem was due tolow investment in spike tissue and ahigh percentage at an<strong>the</strong>sis of greentillers which failed to bear spikes (often<strong>the</strong> spike died in <strong>the</strong> bootl, and withsmall, abnormal spikes for daylengthsensitivecultivars (26,27). In earlier,relatively insensitive cultivars, <strong>the</strong>proportion of dry weight invested inspikes was unaffected at ei<strong>the</strong>r tropicalsite, as was <strong>the</strong> case at hightemperatures in a controlledenvironment (31). If <strong>the</strong> connection,under hot conditions, between latenessand high total dry matter at an<strong>the</strong>sis.on <strong>the</strong> one hand, and poor partitioningto (and fertility of) spikes, on <strong>the</strong> o<strong>the</strong>r.could be broken, grain numbers wouldbe increased substantially.Grain set-Grain number per unit ofspike weight (Table 2) is largelyinfluenced by grain set. There areseveral controlled environment studiesindicating that high temperaturereduces grain set, i.e., increases <strong>the</strong>proportion of large and superficiallynormal florets which are sterile and donot bear grain (23,32,43). Curiously,early high temperature may increasegrain set (1). In Gabo wheat. usuallygrown at 20°C, grain set was reduced60 and 30%, respectively, on exposureto a continuous temperature of 30°C, or30°C by day and 20°C at night. forthree days at meiosis (about flag-leafemergence) (32). Plant water status wasunaffected; but abnormalities in bothovary and pollen development wererecorded (33). Ano<strong>the</strong>r study, while notfinding an effect from a 3O/25°Ctemperature regime with Gabo, foundeffects with o<strong>the</strong>r cultivars (42). O<strong>the</strong>rcontrolled environment studies haveshown that final grain set is weaklysensitive to elevated temperatures atand soon after an<strong>the</strong>sis (35,41), but isinsensitive after seven to ten days haveelapsed (39). Evidence accumulated in<strong>the</strong> Division of Plant Industrylaboratory and elsewhere (9) shows thatcontinuous high humidity ( 70%)around meiosis can also reduce grainset in certain cultivars. Themechanisms involved are not known.

224Unfortunately. <strong>the</strong> significance of <strong>the</strong>secontrolled-environment findings to fieldconditions. where little attention hasbeen paid to grain set per se. is notclear. Soil water deficit-induced malesterility can be very striking in <strong>the</strong>greenhouse. but is less evident.although important. in <strong>the</strong> field; <strong>the</strong>same may apply to high temperatureand humidity-induced sterility. In anycase. <strong>the</strong> subject needs attention and<strong>the</strong> approach outlined here ofmeasuring spike (or chaff) weight andgrains per unit weight (or grain set) isrecommended. Should grain setproblems be evident in tropicalconditions. genotypic variation in thisresponse is likely. and careful visualselection against <strong>the</strong> problem isfeasible.Reduced lDdJridual grain weightOver <strong>the</strong> range of 12 to 26°C. increasedtemperature during grain filling reducesgrain weight from 4 to 8% per degree(10.12.39,41.42.43.44); underlyingcausal mechanisms were alluded to inTable 2. Potential grain weight(unlimited assimilate) appears to bereduced by higher temperatures (arange of 15 to 21°C). according to fieldstudies at CIANO (15). Potential kernelweight may be determined by <strong>the</strong>number of endosperm cells formed in<strong>the</strong> early cell-division stage (17.39.41);however. increasing temperature to24°C did not affect final cell number inone study (41). Actual grain weight isusually below potential. because ei<strong>the</strong>rfilling duration and/or filling rate areinadequate. The depressing effect ofhigher temperature on duration hasbeen discussed. It should be noted that<strong>the</strong> termination of grain filling andonset of spike senescence may occurindependently of leaf senescence. asdemonstrated by spike warming (7)and. <strong>the</strong>refore. is under differentcontrolling mechanisms. The rate ofgrain filling becomes greater withhigher temperature. but is unable tofully compensate for <strong>the</strong> reduction induration of filling and. in any case. doesnot increase much above 20°C (35.39).The supply of assimilate for grain fillingcomprises pre-an<strong>the</strong>sis reserves pluscurrent net assimilation (17). Underhotter conditions. increased respirationmay contribute to reduced supply. butit cannot fully explain grain weightreductions (10.35). Increased leafsenescence is probably more importantand can precede grain maturity.whereas. under cooler conditions. itoften follows it. It has been suggested(39) that hastened leaf senescencearises because <strong>the</strong> protein (nitrogen)demand of grains increases morerapidly with temperature than <strong>the</strong>ircarbohydrate demands; this is satisfiedby a correspondingly faster withdrawalof nitrogen from <strong>the</strong> leaves. Theincrease in grain-nitrogen percentagewith higher temperatures is wellestablished (10.36). Finally.photosyn<strong>the</strong>tic rate is unlikely to beaffected by higher temperatures. asalready discussed. but would bereduced by low radiation during grainfilling in parts of <strong>the</strong> humid tropics.It would seem that higher temperatureshifts <strong>the</strong> balance towards grain weightlimitation through reduced assimilatesupply (15.39); thus. leaf-areamaintenance (e.g.. avoiding prematureleaf firing) is probably more critical.This makes more difficult <strong>the</strong> study orscreening of genotypes for resistance toreduced grain weight under controlledenvironmentconditions. and <strong>the</strong> fewstudies available have not foundconvincing genotypic differences in thistemperature response. or that of <strong>the</strong>components involved. It is conceivable(39) that genotypes with inherently lowgrain-nitrogen percentages would showlower <strong>the</strong>rmal sensitivity. It is alsopossible that waxy genotypes would bebetter. since <strong>the</strong>ir leaf and. especially.spike temperatures are lower. (R.A.Richards. personal communication). Itis worth noting that grain weight in

225rice, ano<strong>the</strong>r C3 crop plant. is littleaffected by grain-filling temperature.dropping less than 1% per degree over<strong>the</strong> range 18° to 33°C (10).Selection soley for high individualkernel weight. at high or any o<strong>the</strong>rtemperature, is unlikely to advanceyield, as many studies showcompensatory declines in o<strong>the</strong>r yieldcomponents. It may be worthwhileasking whe<strong>the</strong>r. for a given grainweight. long duration and slow fillingmay be a better high temperaturestrategy than short duration and rapidfilling.Although correlated positively inone wheat study (35), work with o<strong>the</strong>rcrops suggests some independentgenetic variation in <strong>the</strong>se twocomponents.Damage from hot spells during grainfilling, when associated with hot drywinds. can lead to grain shriveling; thisis mentioned as a problem in parts of<strong>the</strong> dry tropiCS. This problem has beeninvestigated (37) and found to berelated to air temperature (>40°Cappears critical) and associated withreduced plant water status and elevatedplant temperature. It is greatlyaggravated by soil drought. followedimmediately by green-area loss. and isgenerally unrelated to <strong>the</strong> exact stage ofgrain filling. Genotypic adaptations toreduce damage have been claimed (4).Selection for Adaptationto <strong>the</strong> TropicsWith regard to yield selection, <strong>the</strong>rewould seem to be agreement that. onceobvious disorders and unadapted heightand maturity types have beeneliminated from breeding populations.early-generation visual selection foryield potential is ineffective; yieldprogress comes from empirical, buteffective, yield testing. Spring wheatsfor temperate regions reached this pointsome time ago and progress hasslowed, stimulating interest in lessempirical and perhaps more efficientstrategies. In fact, certain physiologicalcriteria are now being used regularly insome successful breeding programs(e.g.. harvest-index selection in <strong>the</strong>University of Sidney, Australia,program). Drought-resistance criteria(e.g.. osmotic adaptation. rootingcharacteristics) are of special interest(16,20) because testing for yield underdry conditions is very inefficient.Where <strong>the</strong>n do we stand in regard towheat in <strong>the</strong> tropics, and what is <strong>the</strong>practical relevance of this lengthy and,at times, uncertain discussion ofphysiology under such conditions? It isprobable that <strong>the</strong>re are still hightemperaturedisorders which can beeliminated by early-generation visualselection, e.g., floret sterility,chlorophyll inadequacies, prematureleaf firing and grain shriveling, asdistinct from small-sized grains. Yieldtesting in appropriate tropicalenvironments is also likely to be a moreefficient tool for progress than it now isunder temperate conditions. Canphysiological considerations improve on<strong>the</strong>se traditional and empiricalstrategies?Probably <strong>the</strong> most important issue inany new environment is that ofdeciding when <strong>the</strong> wheat crop shouldreach an<strong>the</strong>sis, given <strong>the</strong> rulingclimatic constraints. Next follows <strong>the</strong>question of how many days beforeoptimal an<strong>the</strong>sis date <strong>the</strong> crop shouldbe sown (I.e., <strong>the</strong> best maturity class)and how agronomic management canguarantee this sowing date, assumingthat <strong>the</strong>re are no timing constraintsfrom diseases or from preceding orfollowing crops in multiple-croppingsituations. Table 3 suggests Januaryan<strong>the</strong>sis for maximum yield of wellwateredwheat at most tropicallocations; planting date studies tend toconfirm this (6,19,22,38), although <strong>the</strong>yalso tend to show a sharper optimumthan <strong>the</strong>se predictions suggest (Figure5). The reason for this is probably that<strong>the</strong> prediCtion assumes full light

226interception for <strong>the</strong> month beforean<strong>the</strong>sis. Herein lies <strong>the</strong> answer to <strong>the</strong>question about maturity class; <strong>the</strong>cultivar needs to have "enough time(hence. sowing be early enough) toreach adequate light interception (i.e.,LAI > 3.0) no later than one monthbefore <strong>the</strong> optimum an<strong>the</strong>sis date. Sixtydays sowing-to-an<strong>the</strong>sis is just adequateif radiation is high and managementgood; a longer time may be neededo<strong>the</strong>rwise.The excellent work of De et al. (11).although at New Delhi just outside <strong>the</strong>tropics. illustrates this point. Sown onOctober 15. October 30 and November15. Kayansona (with o<strong>the</strong>r improvedcultivars) was earlier than <strong>the</strong> oldercultlvar C306 by 31. 24 and 4 days.respectively. Its yield was 46. 98 and30u=o 0-:-:g:a0. .... -S"t:l~25B~.§§ §~ ......Q) Q)::s::S 20l:)000~ 4000~~ 3000'>'c';l(; 2000---.----Photo<strong>the</strong>nnalQuotient;, ... - - - - --- ...,,;-................. ."",.,.;,. ....... .........Temperature.-......~._._.. __.-. Radiation.........._./,-,--" 1966" ". __ !.~ ", (Beech and",' '" Nonnan)- ---':'}'''-~-..._- " , ,~;;o " ,, ,, ,~ ,~:\" ~" " ':\ ~U1.2 0"aNe.§Q)~1.0 ..c:: ......0 .......... o = Q)..c::::::0.80.. g0>1000Jun 1 July 1 Aug 1 Sep 1Date of an<strong>the</strong>sisOctlFigure 5. Long-term climatic averages. predicted grain yield from <strong>the</strong>seaverages and Equation 3. and actual yields for <strong>the</strong> best cultlvars andmanagement in two seasons at KUDUDurra. northwestern Australia (16°8lat.).Source: Beech and Norman (6)

227105% that of C306 for <strong>the</strong> threesowings. respectively; <strong>the</strong> yield of C306was unaffected by sowing date. Clearly.Kalysansona developed too rapidly toan<strong>the</strong>sis with <strong>the</strong> October 15 sowing.and a cultivar like C306. with a smallvernalization response. was betteradapted to <strong>the</strong> early date.Early sowing. as described in this NewDelhi study. is often desirable for wheatsown on receding monsoon moisture.although improved agronomicmanagement (better tillage. deep-furrowdrills) can permit later seeding. Undersuch non-irrigated conditions. one oftwo key issues is <strong>the</strong> importance ofhaVing maximum crop growth coincidewith <strong>the</strong> period of lowest VPD.December to February (Figure 1). inorder to maximize WUE. Fortunately.this does not disagree with optimuman<strong>the</strong>sis date considerations whenwater is not limiting. The o<strong>the</strong>r issuewith growth on ample stored water is<strong>the</strong> importance of maximizing wateravailable for crop transpiration(Equation 4) by haVing deep rooting.Deep rooting is probably related tohaVing a long sowing-to-an<strong>the</strong>sisduration. and may be ano<strong>the</strong>r reasonwhy C306 performs well in <strong>the</strong> earlysowing when WUE may be prejudiced.Certainly. in a dry season. its yieldadvantage over Kayansona wasespecially evident (11). The juggling ofsowing date and cultivar-maturity classis both complex and profitable indryland Queensland. Australia(Woodruff. <strong>the</strong>se proceedings). Inconclusion. it should be emphasizedthat <strong>the</strong>re are genetic mechanisms forextending <strong>the</strong> duration up to an<strong>the</strong>sis.even under hot conditions. Yieldpotential will be approximatelyproportional to duration up to somelimit (i.e.• 60 to 100 days. depending on<strong>the</strong> crop growth environment). prOVidedthat <strong>the</strong> longer duration is accompaniedby earlier planting and that poorpartitioning to <strong>the</strong> spike and abnormalspike growth can be avoided. Also.water supply must be adequate tosupport <strong>the</strong> extra growth. Breeding for<strong>the</strong> new tropical environments shouldbe more efficient when optimuman<strong>the</strong>sis dates and durations are betterdefined.Of <strong>the</strong> o<strong>the</strong>r possible adaptations to hotconditions. none has reached <strong>the</strong> statusof recommended selection criteria;however. <strong>the</strong>re are many possibilitiesworthy of investigation in pilot breedingprojects. They are. along with someo<strong>the</strong>r relevant physiological questions:• Vernalization sensitivity versusphotoperiod sensitivity to extendduration;• Spikes cooled by increased waxiness;• Long sowing-to-an<strong>the</strong>sis period. fordeep rooting and full exploitation ofstored water;• Genetic variability in maintenancerespiration;• Long filling duration versus rapidfilling. and low grain-nitrogencontent to stabilize grain weight;• Grain set. as affected bytemperature. humidity and o<strong>the</strong>reffects;• The role of <strong>the</strong> Norio 10 dwarfinggenes in <strong>the</strong> tropics. where stature isreduced in any case. and• The likely magnitude of heterosis in<strong>the</strong> tropics.To this list of worthwhile researchtopics should be added <strong>the</strong> analysis andinterpretation of international yieldtrials in <strong>the</strong> tropiCS. something whichcould contribute significantly to <strong>the</strong>understanding of genetic adaptation.prOVided enough trials were conductedin a standard manner and with goodagronomic management.

228Whe<strong>the</strong>r or not <strong>the</strong>se specificsuggestions on issues are followed.<strong>the</strong>re is no doubt that researchers. bothwithin and outside <strong>the</strong> internationalnetwork. will continue to lookinquisitively at <strong>the</strong> physiology of wheatin <strong>the</strong> tropics. This is good. since solittle is known. However, efforts foradvancing general understandingwould be more useful if a minimum setof information were collected andreported in future field experiments. At<strong>the</strong> least. this should include sowingdate, established plant population.an<strong>the</strong>sis date. yield. harvest index andindividual grain weight. PreVailingtemperatures are essential information.and reliable radiation data areimportant. If <strong>the</strong> crop is rainfed andwater limited. data on soil moisture atsowing and maturity. rainfall and panevaporation are essential. Everyoneshould agree on <strong>the</strong>se data. A seriousconsideration is urged of measurementsof ground cover or light interception.total and spike dry matter at an<strong>the</strong>sisand counting of florets and grains todetermine grain set. Growth and yieldsampling should be on an area basis.ra<strong>the</strong>r than per plant. and edge effectsmust be avoided. Finally. those temptedor obliged to work in controlledenvironments should continuallyexamine results for <strong>the</strong>ir relevance tofield research programs.AcknowledgementsThe author wishes to thank Ms. Y.S.Stockman for help with <strong>the</strong> preparationof this paper. and L.T. Evans. M.G.Bush. H.M. Rawson and I.F. Wardlawfor <strong>the</strong> provision of unpublished data.References1. Amores-Vergara. E.. andP.M. Cartwright. 1984. AustralianJournal of Agricultural Research35:139-148.2. Angus. J.F.. RB. Cunningham.M.W. Moncur and D.H. MacKenzie.1980/1981. Field Crops Research3:365-378.3. Angus. J.F.. D.H. MacKenzie.R Morton and C.A. Schafer. 1981.Field Crops Research 4:269-283.4. Azzi, G. 1956. Agricultural Ecology.Constable. London. England.5. Bagga. A.K.. and H.M. Rawson.1977. Australian Journal of PlantPhysiology 4:877-887.6. Beech. D.F.. and M.J.T. Norman.1968. Australian Journal ofExploratory Agricultural AnimalHusbandry 8:349-357.7. Bhullar. S.S.. and C.F. Jenner.1983. Australian Journal of PlantPhysiology 10:549-560.8. Cackett. K.E.• and P.C. Wall. 1971.Rhodesian Journal of AgriculturalResearch 9:107-120.9. Campbell. C.A.. D.S. McBean andD.G. Green. 1969. CanadianJournal of Plant Science 49:29-37.10. Chowdhury. S.I.. and I.F. Wardlaw.1978. Australian Journal ofAgricultural Research 29:205-223.11. De. R. G. Saran. B.B. Turkhede.RB. Lal. RK. Singh and G. Girl.1983. Journal of AgriculturalScience (Cambridge) 101:727-733.12. Evans. L.T.• and M.G. Bush. 1984.(Unpublished manuscript.)

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23036. Sofield, I., I.F. Wardlaw, L.T. Evansand S.Y. Zee. 1977. AustralianJournal of Plant Physiology 5:799810.37. Turner, N.C., and P.J. Kramer, eds.1980. Adaptation of Plants to Waterand High Temperature Stress. JohnWiley and Sons. New York, USA.38. Verma, U.K., B.N. Verma,S.P. Singh and S. Pandit. 1978.Annals of <strong>the</strong> Arid Zone 17:353356.39. Vos, J. 1981. Effects of temperatureand nitrogen supply on post-floralgrowth of wheat: Measurementsand simulations. AgriculturalResearch Reports 911. Pudoc,Wageningen, Ne<strong>the</strong>rlands.40. Wall, P.C.• and P.M. Cartwright.1974. Annals of Applied Biology76:299-309.41. Wardlaw,I.F. 1970. AustralianJournal of Biological Science23:765-774.42. Wardlaw, I.F., and LA. Dawson.1984. (Unpublished manuscript.)43. Warrington, I.J., R.L. Dunstone andL.M. Green. 1977. AustralianJournal of Agricultural Research28:11-27.44. Wiegand. C.L., and J.A. Cuellar.1981. Crop Science 21:95-101.45. Weigand, C.L., A.H. Gerbermannand J.A. Cuellar. 1981. AgronomyJournal 73:29-37.46. Wilson, D., and W.G. Jones. 1982.Annals of Botany 49:313-320.47. Woodruff, D.R., and J. Tonks.1983. Australian Journal ofAgricultural Research 34:1-12.

Soil Management as an Alternativefor Minimizing Environmental Constraintsfor Wheat Production in <strong>the</strong> Semitropical Areasof Brazilo. Muzilll, Instituto Agronomico do Parana, Londrina, Parana,BrazilAbstractIn <strong>the</strong> semitropical areas ofBrazil. <strong>the</strong> increase and stabilization ofwheatproduction are restricted by such environmental factors as irregular rainfall.frost. soil acidity. low fertility and disease. associated with improper soilmanagement. Some progress has been obtained by Brazilian research efforts forfinding alternatives to minimize <strong>the</strong>se enVironmental constraints. Alternativesinclude cropping practices and <strong>the</strong> use of varieties tolerant to soil acidity,combined with soil tillage methods and appropriate use offertilizers.231Under Brazilian semitropical conditions(Figure I), <strong>the</strong> increase and stabilizationof wheat production is mainly affectedby climatic conditions and diseases.O<strong>the</strong>r factors are improper soilmanagement. which promotes erosionand obstructs root development. andnatural soil constraints such as acidityand low fertility.The breeding programs in Brazil haveachieved great genetic progress inobtaining varieties better adapted to itsenvironmental conditions. Some of <strong>the</strong>major accomplishments are soil-aciditytolerance. disease resistance. heattolerance (better adaptation to <strong>the</strong>Tropic ofCapricorn (23°S)Parana StateFigure 1. The Brazilian semitropical area (Inset of South America showingBrazil)

232relatively warm autumn-winter season)and nonsensitlvity to photoperiod. Thistechnical progress has allowed <strong>the</strong>expansion of <strong>the</strong> wheat productionboundaries toward more tropicalconditions, such as <strong>the</strong> Cerrados regionin central Brazil (2). Because of this,environmental constraints can nolonger be considered an impediment towheat production in semitropical areas.Never<strong>the</strong>less, a challenge remains foragricultural scientists in <strong>the</strong>development of alternative croppingpractices more appropriate to tropicaland semitropical conditions. Suchalternatives and <strong>the</strong>ir association withadvances in plant breeding can help toincrease and stabilize wheat productionunder <strong>the</strong>se conditions.The aim of this paper is to report someof <strong>the</strong> progress. obtained throughBrazilian agricultural research efforts,in finding alternatives to minimizeenvironmental constraints for wheatproduction in <strong>the</strong> semitropical areas,particularly those obtained by <strong>the</strong>Agronomy Institute of Parana (lAPAR)for <strong>the</strong> preVailing conditions of <strong>the</strong>nor<strong>the</strong>rn part of <strong>the</strong> state of Parana.Alternatives toMinimize Climatic ConstraintsAmong climatic factors. irregularrainfall dUring <strong>the</strong> season is <strong>the</strong> mostimportant constraint affecting wheatproduction in <strong>the</strong> Brazilian semitropicalarea (Table 1). Sporadic frostoccurrence (once or twice in each fiveyearperiod) is also a constraint when itcoincides with wheat heading.However, frost occurrence cannot bepredicted and farmers accept that risk.In nor<strong>the</strong>rn Parana, rainfall affectswheat production, mainly throughunreliable distribution ra<strong>the</strong>r than byamount during <strong>the</strong> cropping period.According to data shown in Table 2,despite low rainfall in 1968, wheatyields were reasonable (900 kglha) incomparison to <strong>the</strong> state average (1000kglha). On <strong>the</strong> o<strong>the</strong>r hand, <strong>the</strong> excess ofrainfall during <strong>the</strong> heading-maturingstages in 1972 led to very low yields(245 kglha) and also affected grainquality. In 1974, rainfall distributionwas adequate to supply crop needsduring <strong>the</strong> growing period, resulting inbetter yield levels (1547 kglha) (3).Yield instability due to such climaticconditions may be minimized withincertain limits by adopting <strong>the</strong> staggersowing practice. This consists ofplanting varieties of different maturitiesat different times. within <strong>the</strong>recommended wheat-sowing calendar.Associated with this practice, <strong>the</strong>adoption of soil tillage methods forimproving water storage in <strong>the</strong> arablelayer is desirable as an alternative tominimize <strong>the</strong> negative effects of <strong>the</strong>lack of rainfall dUring <strong>the</strong> winterseason. Figure 2 shows <strong>the</strong> increasingTable 1. Occurrence of climatic factors affecting wheat production, nor<strong>the</strong>rn Parana state,Brazil, 1974 to 1978Occurrence~Climaticfactor 1974 1975 1976 1977 1978 AverageFrost 0 xxx 0 0 0 xExcessive rainfall 0 0 xx 0 0 xLack of rainfall x xx 0 xxx xxx xx.!/ 0 = did not occur; x = light occurrence; xx = medium occurrence; xxx = heavy occurrenceSource: Y.R. Mehta (personal communication)

233water content in <strong>the</strong> surface arablelayer of an oxisol soil (red latosol) when<strong>the</strong> zero tillage system is adopted (7).This practice in <strong>the</strong> soybean-wheatrotation leaves <strong>the</strong> soil surface coveredby <strong>the</strong> crop residues. This cover ormulch reduces water evaporation andstabilizes <strong>the</strong> temperature in <strong>the</strong> arablelayer. By reducing soil disturbancethrough no-tillage. <strong>the</strong> soil structure isimproved. soil compaction is minimizedand roots can penetrate more deeply.resulting in better growth. As aconsequence of more uniform andVigorous growth. <strong>the</strong> wheat crop canbetter tolerate inadequate rainfall. andgrain yields can be increased (Table 3).However. <strong>the</strong>re were negative effects offrost in <strong>the</strong> 1979 season under notillage;damage was more pronounceddue to <strong>the</strong> lower temperature caused by<strong>the</strong> mulching effect on <strong>the</strong> soil surface.Table 2. Rainfall during <strong>the</strong> various wheat growth stages as related to grain yields undernor<strong>the</strong>rn Parana semitropical conditions, Brazil, 1968 to 1978Rainfall (mm)AverageGrowth stage 1968 1972 1974 1968-78Sowing-shooting (M arch/ApriI) 93 157 197 60Shooting-heading (May/June) 68 156 313 108Heading-maturity (July/August) 88 415 80 167Total rainfall 249 728 590 875Wheat yields (kg/ha) (899) (245) (1547)Source: Godoy and Bernardes (3)Table 3. Comparison of wheat yields under inadequate and normal rainfallconditions related to tillage systems, nor<strong>the</strong>rn Parana, Brazil, 1977 to 1980Rainfall/yearWheat yields (kg/ha)according to tillage systemConventional No-tillageInadequate19771978Normal197919804-year average (1977-1980).,g/ Frost damageSource: Vieira (7)60950718541867120996720361281.,g/17991521

234Alternatives toMinimize Soil ConstraintsSoli conservationand water retentionSoil tillage practices utilized in <strong>the</strong>soybean-wheat rotation are leading tosevere soil erosion in <strong>the</strong> Braziliansemitropical area. Burning wheat strawafter harvest. followed by landpreparation using heavy disc harrows.are common practices. Theseoperations result in an intensivedisturbance of <strong>the</strong> arable surface layer(0 to 10 cm). destroy organic maUer.decrease water infiltration and build upa compacted layer (hard-pan) between<strong>the</strong> 10 and 15-cm depth. causing strongrun-off and inadequate conditions forroot penetration and development. Soilerosion losses can be reduced 70 to90% by adopting a more appropriateconventional tillage method (plowingplus two light harrowings) or a notillagesystem (Figure 3). No--tillageenhances surface mulching by leaVingcrop residues and helps to increasewater retention and water aVailabilityfor <strong>the</strong> wheat crop (Figure 2).30~253$20oe15~34--No-tillage ----- Conventional tillage ,--------.... ....-,/',....,-.. -.,. ..---', ..." ... - ....---\ I, I,------_.'--------...._--. ,-,'"26 --.'".--------.-...-.10 20 30Days after planting-""Figure 2. Soli-water availability under conventional and zero tillagesystems in an o.1l:lsol soli. nor<strong>the</strong>rn Parana. Brazil"5-5It) 0.• il)0'0~--jeo.(.):;::l0 0~CI)6-60_Traditional (burning + 1 heavy harrOWing+ 2-5 light harrowings)Conventional (1 plOWing + 2 light harrowings)__......1 No-tillage15Tillage systemsFigure 3. Soil losses by erosion as related to tillage systems in an o.1l:isol(red latosol) soli, nor<strong>the</strong>rn Parana, Brazil

23~Tolerance to soil aciditySoil acidity is one of <strong>the</strong> majorconstraints for agricultural productionin tropical and subtropical soils inBrazil, and effects of excess aluminumon <strong>the</strong> wheat crop are well known.Advances in plant breedin,g, initiated byIwar Beckmann in sou<strong>the</strong>rn Brazil in1920, have led to <strong>the</strong> development ofaluminum-tolerant varieties which givereasonable yields under acid soilconditions, even when lime is notapplied; sensitive varieties give loweryields even when lime is applied(Figure 4). To arrive at appropriaterecommendations for farmers, <strong>the</strong>1.61.2variety tolerance level to soil aciditymust be considered, since soils arevariable in acidity levels and varietiesgive different performance on acid soils,even with liming. Under fieldconditions, a study was carried out inorder to characterize limit-values for %of soil-aluminum saturation:(% Al = Al x 100)AI+Ca+Mg+KThis formula can be used as aparameter to quantify <strong>the</strong> tolerance ofwheat varieties to soil acidity. Table 4_NoLime-;s''%'' ,.~ Liming for Al =0,--_I Liming for pH =6.00.4IAC-5 (Maringa)VarietySonora 64-RFigure 4. Effects of liming on yield of two wheat varieties in an OZl801 (redlatosol) soil, nor<strong>the</strong>rn Parana, BrazilTable 4. Criteria used to classify aluminum tolerance of wheat varieties, Parana, BrazilTolerance levelof varietyHighly susceptibleSusceptibleMedium tolerantTolerantHighly tolerantCritical value of soil-AI saturation(80 cm profile depth)Less than 5 0/0less than 20 0/0less than 35 0/0Less than 45 0/0More than 45 0/0

236shows <strong>the</strong> classification of wheatvarieties according to <strong>the</strong>ir aluminumresistance (4). Since 1979. <strong>the</strong>recommendation of varieties for <strong>the</strong>acid soils of Parana have been based onthis criteria.Nitrogen fertlUzationWith Brazilian wheat varieties. <strong>the</strong> useof high nitrogen levels frequentlypromotes negative effects. such aslodging. increased disease susceptibilityand delayed maturity due to anextension of <strong>the</strong> vegetative growthperiod. Usually <strong>the</strong> Brazilian varietiesdo not respond to levels higher than30 kg N/ha and. under Braziliancropping conditions. even <strong>the</strong> Mexicanvarieties do not respond to levels higherthan 60 kg N/ha (Figure 5). The low Nresponse may be due to <strong>the</strong> benefits of<strong>the</strong> soybean-wheat double croppingsystem. Soybeans supply that nutrientto <strong>the</strong> soil. not only through symbioticN fixation. but also because remainingcrop residues (6 to 8 Uha) increase <strong>the</strong>N aVailability in <strong>the</strong> arable layer after<strong>the</strong> organic material is decomposed.Therefore. a large part of <strong>the</strong> N neededby <strong>the</strong> follOWing wheat crop is supplied(5). Varietal response to nitrogen differsfrom one region to ano<strong>the</strong>r and fromone year to ano<strong>the</strong>r in <strong>the</strong> same region.This variation is mainly due to climaticfactors. particularly rainfall occurrence.Phosphorus fertilizationTropical soils are, in general, poor inavailable phosphorus, and <strong>the</strong> majorityof annual crops show a strong reactionto phosphorus application. The relevanteffects of phosphorus, in areas wherewheat has recently been cultivated,have induced <strong>the</strong> use of relatively highamounts of this nutrient. TheWidespread adoption of this practice in<strong>the</strong> soybean-wheat rotation haspromoted a gradual increase in soilphosphorusaVailability after severalyears, and an equilibrium is beingachieved between crop needs and Pavailability in <strong>the</strong> soil. As aconsequence, <strong>the</strong> response tophosphorus application has tended todecrease, a fact supported byexperimental data (Figure 6). Once thiscondition is achieved, it is possible toreduce <strong>the</strong> amount of phosphorus100 L_----:=~==-=~."...,ci:':='.......... -.----,~....... ..=..!:a.-._::::~:-:::===:::::::_-----," ,.................. -----..---.----..-',--"-... --.. ..... .......""-" --- ...-.................... 80~'t:l~ 60Il).e:;g 40~20........ "",,-,- - ... _----- IAC-5/Maringa-'-'-' CIANO------- INIA25 50(kg/hal75 100Figure 5. Responses of three wheat varieties to nitrogen fertilization,nor<strong>the</strong>rn Parana, Brazll

237applied without increasing <strong>the</strong> risk ofyield reductions (Figure 7). Thus.production costs can be lowered (5).Adverse environmental factorsassociated with improper soilmanagement and diseases areconstraints affecting wheat productionin <strong>the</strong> Brazilian semitropical areas.Considering <strong>the</strong> high cost of productionand <strong>the</strong> high value of land in <strong>the</strong>seareas. appropriate technologies must begenerated and adopted. especially interms of land use and soil management.in order to minimize environmentalconstraints. increase wheat productionand lower production costs.Agricultural scientists are challenged todevelop efficient alternative soilmanagement and cropping practices.appropriate to <strong>the</strong> environment and tofarmers' conditions. Also. <strong>the</strong> ExtensionService must devote more effort toadvising farmers about <strong>the</strong> relevance of<strong>the</strong>se practices as options for reducingrisks and increasing benefits. thusmaking possible <strong>the</strong> success of wheatproduction in <strong>the</strong> semitropical areas.2.0--------------- ...-------- --- --_....--------.----_...-.--- Areas under recent cultivation- Areas under continuous cultivation(after 4 years soybean-wheat)40 120 180Figure 6. Wheat response to phosphorus application in areas under recentwheat cultivation and after four years of soybean-wheat rotation. Parana.Brazil2.0in <strong>the</strong> soil:2 ppm-0- 5 ppm-0-15 ppm-6-30 ppm0--------0~-------O-------O-6------__650 .100 150Figure 7. Wheat response to phosphorus application in an ozlsol (redlatosol) soil as related to P availability in <strong>the</strong> soil. Parana. Brazil

238References 4. Muzllli. 0 .. D. Santos. J.B. Palhano.J. Manetti. A.F. Lantmann. A.1. Gaudencio. C.A.. and O.A. Muzilli. Garcia and A. Cataneo. 1978.1980. Tolerancia a acidez do solo Tolerancia de cultivares de soja ecomo parametro para ade trigo a acidez do solo. Revistarecomendacao de variedades de Brasileira de Ciencia Solo 2:34-40.trigo no Parana. Informe PesquisaIAPAR 25. Londrina. Brazil. 5. Muzllli. 0 .. and M.A. Hoepfner.1981. Adubacao mineral do trigo no2. Gaudencio. C.A.. and O.A. Muzllli. .Estado do Parana. In Cultura do1981. Importancia do trigo e da Trigo no Estado do Parana. IAPARcontribuicao do melhoramentoCircular 22. Londrina. Brazil. Pp.genetico brasileiro para adaptacao 39-48.da cultura no Parana. In Cultura doTrigo no Estado do Parana. IAPAR 6. Vieira. L.G. 1981. DesenvolvtmentoCircular 22. Londrina. Brazil. Pp. e produtividade das culturas:69·70. Cultura do trigo. In Plantio Diretono Estado do Parana. IAPAR3. Godoy. H.. and L.R.M. Bemardes. Circular 23. Londrina. Brazil.1981. Clima. In Cultura do Trigo no P.196.Estado do Parana. lAPAR Circular22. Londrina. Brazil. pp. 10-13. 7. Vieira. M.J. 1981. Propiedadesflsicas do solo. In Plantio Direto noEstado do Parana. lAPAR Circular23. Londrina. Brazil. P. 23.

The Cerrados: Future WheatProduction Prospects and LimitationsM.A. McMahon, Wheat Program, CIMMYT, Santiago, Chile, and W.J.Goedert, Empresa Brasileira de Pesquisa Agropecuaria, Planaltina,D.F., BrazilAbstractOver <strong>the</strong> past twenty years, a lot of interest has been shown in developing <strong>the</strong>agricultural potential ofwhat is known as <strong>the</strong> Campos Cerrados. The CamposCerrados is a semitropical savannah composed ofa woodland-shrub-grasslandcomplex which is thought to be an edaphic climax. This means that <strong>the</strong> soil is<strong>the</strong> majorfactor in <strong>the</strong> development of <strong>the</strong> vegetation. The soil is based on a veryold geological surface and has been highly wea<strong>the</strong>red and leached, leaving veryfew nutrients and a subsequent breakdown ofclays; <strong>the</strong> underlying rock ismostly shale. Similar areas arefound in Africa.239The increased interest in <strong>the</strong> Cerradosis due to <strong>the</strong> follOWing factors:• It covers a very large area suitablefor crop production; of an estimated50 million hectares. only 3% is atpresent under cultivation (Figure 1);• It has suitable temperatures for mostcrops, and sufficient summer rainfall(Figure 2);• It has a well-developed and stilldeveloping infrastructure (I.e.,transport), and• Its Virgin land prices are still low (5).---t-----1r------+-~~l.OiiiiO:=___-+----OO-------i,------ti------.l."...--+---- 24 0Figure 1. Distribution of Cerrados (shaded area) in Brazil (inset of SouthAmerica showing Brazil)Source: Goedert (5)

240Soil Fertility ProblemsThe soils most suited for cropping in<strong>the</strong> Cerrados are <strong>the</strong> red-yellow latosolsand <strong>the</strong> dark red latosols. A surveycarried out by Lopes and Cox (8) showsthat <strong>the</strong>se soils are extremely low infertility in every aspect except organicmatter (Table 1). Virgin soils normallyhave a reasonable level of organicmatter. but this is decreased bycropping. and nitrogen needs to beadded to obtain high yields ofnonleguminolls crops. The two mainsoil problems are 1) low pH with itsaccompanying high exchangeablealuminum saturation and 2) low soilphosphorus levels. These two problemsmust be resolved. and <strong>the</strong>ir solutionwill be costly.Low pHThe problem of low pH and highexchangeable aluminum saturation canbe solved by liming. Two formulas arenormally used for making limingrecommendations:CaC03(tlha) :: 2 x meq exch AVl00 gorCaC03(tlha) :: (2 x meq exch AJI100 g) +12 - meq exch (Ca + Mg)/I00g]As a result of <strong>the</strong>se formulas.recommendations usually range from 2to 4 tons of lime per ha; this results ingood crop response.The lime is usually incorporated to adepth of 30 em. which corrects <strong>the</strong>problem only to this level; in o<strong>the</strong>rwords. with <strong>the</strong> application of lime.<strong>the</strong>re is an effective rooting depth ofonly 30 em. Under Cerrados conditions.e 400e-I:~.= 300oooooDTOPp• PETooo oo30- 20 C,)of~200>v't:l~~ 100I:~jv 0.e10 ~J F M A M J J A s°MonthNDFigure 2. CUmatic conditions ofBrasiUa, D.F., Brazil (average monthlytemperature (T) 21°C, annual rainfall (PP) 1570 mm and annual potentialevapotranspiration (PET) 1280mm)Source: EMBRAPA-CPAC(2)

241<strong>the</strong>re is utilizable water storage for onlyfive to six days (ET = 5-6 mm/day).Therefore. it would be very desirable toincrease rooting depth by moving <strong>the</strong>calcium down <strong>the</strong> profile. This problemhas been <strong>the</strong> subject of research for anumber of years. and very promisingresults have been achieved. As shownin Figure 3. wheat root growthresponds very dramatically to smallconcentrations of calcium; <strong>the</strong>refore.300.5 1.0 1.5 4.4 0.5 1.0....- ....._ ......._-""-.....,'/-J~---===..Ca (Meq/lOOg)1.150.51.01.58090RQ)o 120150180210• °• 800 C03.2000 C03Ca(kg/ha)Ca (kglha)• 800804.2000 804Ca (kg/ha).2000 CI• InitialvalueFigure 3. Wheat root growth as a funcium application in samples takenfrom <strong>the</strong> subsoil layer of a red-yellow latosol. Brazil (vertical linesrepresent 1 SD)Source: EMBRAPA-CPAC(4)Table 1. Fertility status of a range of soils from <strong>the</strong> Cerrados area of BrazilSufficient levelParameter Range Median (SL) Percent of SLpH 4.3D-6.7 5.0 5.0 48% belowExtractable phosphorus 0.10-16.5 ppm 0.4 ppm 10ppm 92% belowExtractable potassium 0.02-0.6 meq/l00 ml 0.08 meq/l00 ml 0.15 meq/l00 ml 85% belowExchangeable calcium 0.04-6.81 meq/l00 ml 0.25 meq/l00 ml 1.5 meq/l00 ml 96% belowExtractable zinc 0.2Q-2.2IlQ1ml 0.61lQ1ml 0.81lQ1ml 81% belowExtractable copper 0-9.7 IlQIml 0.651JQ/ml 1.0 IlQIml 70% belowAluminum saturation 1.10-84.9% 59% 20% 91% aboveOrganic matter 0.7D-6.0 0 /0 2.2% 60% between1.5 and 3.0%Cation exchange capacity 0.35-8.1 meq/1oo g 1.1 meq/100g - '-(CEC)Soorce: Lopes et al. (8)

242<strong>the</strong> movement of small amounts ofcalcium down <strong>the</strong> profile shouldincrease effective rooting depth. Thework of Ritchey et al. (10) presentsvarious ways of solving this problem.As can be seen from Figure 4. <strong>the</strong> rateand amount of movement of calciumdown <strong>the</strong> profile is an electricallyneutral phenomenon. Every Ca+ + ionmust be accompanied by twomonovalent anions. such as CI-. on onedivalent anion. such as SO--4. Theaccompanying anion. <strong>the</strong>refore. plays avery important role.Calcium carbonate (CaC03) isneutralized by hydrogen ions at <strong>the</strong> soilsurface; <strong>the</strong>refore. <strong>the</strong>re is no anion toaccompany <strong>the</strong> calcium down <strong>the</strong>profile. This results in very littlecalcium movement from this level.CaCl2 is very soluble in water and.since it is monovalent. it reacts verylittle with <strong>the</strong> soil colloids. This sourceof calcium shows <strong>the</strong> fastest movementdown <strong>the</strong> profile and. possibly. even outof <strong>the</strong> rooting zone. CaS04 or gypsumis less soluble and <strong>the</strong> SO--4 ion reactsmore strongly with <strong>the</strong> soil. leading to amore desirable distribution of calciumthroughout <strong>the</strong> profile.The practical way of achieving gooddistribution of calcium in <strong>the</strong> soil is toapply one of <strong>the</strong> following:• CaS04 (gypsum)• Single superphosphate (SSP), whichcontains calcium sulfate. Thereaction for producing SSP is:CalOF2 (P04)6 + 7 H2S04 + 3 H2(fluorapatite) (sulfuric acid)3 Ca(H2P04)2°H2) + 7 CaS04 + 2 HF(monocalcium (calcium (hydrophosphate)sulfate) fluorlcacid)The effect of varying rates of SSP oncalcium and magnesium movementdown <strong>the</strong> profile are shown inFigure 5.E~..c: .....s::.!!'Ql).....&10 •:;0.1 0.2Calcium (Meq/l00g)0.4Figure 4. The effect of various anions on <strong>the</strong> distributions of calcium in adark red latosol after leaching. with <strong>the</strong> equivalent of 1200 mm of rainfall.BrazilSource: Ritchey et al. (10)

243• Ammonium sulfate [(NH4)2S04] as anitrogenous fertilizerLow phosphorus levelsPhosphorus is highly and universallydeficient in <strong>the</strong> Cerrados area.Therefore. correction of this deficiencyis imperative for <strong>the</strong> production of cropsin <strong>the</strong>se soils. Crop responses tophosphorus fertilization. as shown inFigure 6. include quite high yields. but<strong>the</strong> amount of phosphorus necessary isalso high, with economic levels being in<strong>the</strong> range of 250 to 500 kg P205/ha.Much work has been carried out ondifferent management strategies for <strong>the</strong>use of phosphorus, such as broadcastversus banded applications and a largesingle application versus smallerrepeated applications. This work issummarized in Table 2.,-These results show that. in <strong>the</strong> longterm, yields are determined by <strong>the</strong> totalamount of P205 applied; differentmethods of application give similarresults. However, it was observed thatbroadcast applications outyieldedbanded applications for <strong>the</strong> first crop;<strong>the</strong> opposite was found after <strong>the</strong> thirdcrop. An initial broadcast applicationseems to give better root developmentand. <strong>the</strong>refore, better water extraction.Low levels of o<strong>the</strong>r nutrientsInsufficient zinc and potassium veryoften limit yields on <strong>the</strong>se soils and<strong>the</strong>ir deficiencies need to be corrected.Nitrogen and sulphur usually becomedeficient after several years of cropping.1Ca + Mg (Meq/lOOg)2 3 430-S45.£.c: ..... 600-Q.)(:)7590105120Figure 5. Effect of varying rates of phosphorus (kg/ha) as SSP on <strong>the</strong>distribution of calcium + magnesium in <strong>the</strong> soil profile of a dark redlatosol. BrazilSource: Ritchey et al. (10)

2448--olII....--------.. Maize6~ ..c::~'0 4-v.-Soybean>-2Wheat200 400 600 800 1000 1200 1400 1600Kg P20S/ha. BroadcastFigure 6. Crop responses to phosphate fertilizer, Brasilia, D.F., BrazilSource: Lobato (7)Table 2. The influence of rate and placement of phosphorus fertilizer on <strong>the</strong> yield of tenconsecutive crops of maize on a dark red latosol, Brasilia, D.F., BrazilPhosphorus application Maize yield Maize yield(kg P20slha (10th crop) hotalof 10 crops)0/0 of best 0/0 of bestBroadcast Banded Total T/ha treatment T/ha treatment160 0 160 0.35 6 17.06 28320 0 320 0.55 10 27.85 45640 0 640 1.47 27 42.67 691280 0 1280 3.98 74 60.83 991960 0 1960 5.38 100 61.64 1000 80(4)!.! 320 0.88 16 30.09 490 160(4) 640 1.90 35 44.05 710 320(4) 1280 4.09 76 61.51 100320 80(4) 640 1.35 25 43.89 7180 80(10) 880 4.81 89 49.77 81!.! Numbers in brackets = number of applicationsSource: Lobato (7)

245Physical Soil ProblemsThe soils under <strong>the</strong> Cerrados aregenerally deep and drain well; <strong>the</strong>y areeasily worked over a wide range ofmoisture conditions. The moisturerelease curves of a dark red latosol anda red-yellow latosol are shown in Figure7. As can be seen from this figure, <strong>the</strong>water retention characteristics aresimilar to those of sandy soils. There isvery little available water above one bartension. The total amount of availablewater is only 33.9 mm in <strong>the</strong> top 30 cmof a dark red latosol, and 42.3 mm in<strong>the</strong> top 30 cm of a red-yellow latosol. Ifevapotranspiration is 5 to 6 mm perday, drought stress occurs very rapidlyif rooting is limited. Therefore, in <strong>the</strong>sesoils, it is of utmost importance toincrease effective rooting depth. Asmentioned earlier, this can be donemechanically, by deep incorporation oflime (although, due to high energyreqUirements, this seldom exceeds 30cm), chemically, by applying sulphatesalts, or genetically, by selectingmaterials resistant to aluminum.Breeding resistant materials alone isnot sufficient, as <strong>the</strong>re is probably no30 •••.-....;0>-~....20Dark Red Latosol•I=:~....I=:0'-lM~....~~ 10••Red-YellowLatosol1 2 4 5 6Tension Bars7I i9 10 15Figure 7. Moisture tension curves for a dark red latosol (DRL) and a redyellowlatosol (RYL)Percent avallable water (0.1-15 bar) DRL =- 11.3. RYL = 14.1Available water (mm) (0-30 em) DRL • 33.9, RYL = 42.3Source: North Carolina State University (9)

246germplasm resistant to <strong>the</strong> levels ofaluminum found in <strong>the</strong>se soils. The useof a combination of <strong>the</strong> above methodswill increase effective rooting depth.which is now <strong>the</strong> greatest limitation towater use.Future WheatProduction in <strong>the</strong> CerradosWhile research has been carried out onwheat in <strong>the</strong> Cerrados for <strong>the</strong> past tenyears. it has not been with <strong>the</strong> sameintensity as on o<strong>the</strong>r crops. This isespecially true in terms of agronomicmanagement; <strong>the</strong> data that exist foro<strong>the</strong>r crops are nonexistant for wheat.This is due to <strong>the</strong> fact that o<strong>the</strong>r crops,such as maize and soybeans, are moreimportant to <strong>the</strong> region economically.and have greater agronomicpossibilities because <strong>the</strong>y are sownduring <strong>the</strong> rainy summer season.However. a breeding program based atCPAC. Brasilia. has released a numberof wheat varieties in <strong>the</strong> past few yearswhich have performed well underCerrados conditions. At <strong>the</strong> moment.both summer and winter wheat isgrown.Summer wheatThe summer wheat crop is found above800 m altitude; it is sown in February.after early-crop soybeans. Because oflow yields, this crop has little possibilityof continUing. The principal limitingfactor for this rainy-season wheat cropis disease. mainly helminthosporium.Winter wheatThe wheat crop sown in May. at <strong>the</strong>beginning of <strong>the</strong> dry season. andharvested in September has <strong>the</strong>greatest economic potential. It is grownunder irrigation. and is recommendedfor altitudes above 600 m. Until 1978.this crop was recommended only forareas above 800 m; below that level,spikes showed increasing sterility.However, this problem has been solvedthrough applications of boron.Varieties exist that can be cultivatedunder <strong>the</strong>se conditions, based onexperimental data generated by CPAC.EPAMIG. ENGOPA and o<strong>the</strong>r researchinstitutions in <strong>the</strong> area. These varietiesare recommended by <strong>the</strong> CommisaoNorte Brasileira de Pesquisa de Trigo.In 1982. varieties were recommendedfor cultivation under irrigation (1) for<strong>the</strong> area (13°30' to 24°8 and 42 to54°W). according to two classifications:• For recently cleared soils. above 600m. which still contain someexchangeable aluminum.recommended varieties were IAC5(Maringa) and CNT7• For areas above 600 m. with soilswith good fertility and noexchangeable aluminum.recommended varieties were Alondra4546, Moncho"S", Anahuac, Nambu,Confianca and Jupateco F73The yielding ability of some of <strong>the</strong>sevarieties can be judged from <strong>the</strong> data inTable 3.Diseases and PestsThe main wheat diseases are leaf rust(Puccinia recondita) and stem rust(Puccinia graminis); some powderymildew (Erysiphe graminis) has alsobeen recorded. Genetic resistance to<strong>the</strong>se diseases is easily incorporatedand, with a good wheat breedingTable 3. Wheat yields of four varieties from<strong>the</strong> 1978 CIMMYT International SpringWheat Yield Nursery (ISWYN), CPAC,Planaltina, D.F., BrazilVarietyAlondra S-46Jupateco 73ConfiancaMoncho"9"Source: EMBRAPA-CPAC (3)Yield (kg/ha)3455343527852510

247program. <strong>the</strong>se diseases will not be abarrier to wheat production in <strong>the</strong>future. The severity of <strong>the</strong> rusts willincrease with increasing area underwheat production. The life span ofanyvariety under <strong>the</strong>se conditions probablywill be four to five years, which fur<strong>the</strong>remphasizes <strong>the</strong> need for a dynamicresearch program. There is no diseasedata for sprinkler-irrigated conditions;<strong>the</strong> general observations of <strong>the</strong>scientists involved are that sprinklerconditions will not change <strong>the</strong> diseasespectrum. Since <strong>the</strong> complete croppingsequence made possible by sprinklerirrigation has not been tested. diseasespeculiar to such a sequence, if <strong>the</strong>yeXist. are not yet known.Insect problems have not beenobserved. and weeds. although aproblem with summer crops, do notconstitute a problem in <strong>the</strong> winterseason.Economic ConsiderationsThe main barriers to increased wheatproduction in <strong>the</strong> Cerrados area ofBrazil will be economic ra<strong>the</strong>r thanagronomic. This is especially true ifirrigation is incorporated into <strong>the</strong>system. The cost of reclaiming onehectare of land. as of June. 1984. isshown in Table 4. As can be seen fromthis table. <strong>the</strong> irrigation cost per hectareis US$ 750 or 61 % of total cost.Without irrigation, <strong>the</strong> cost ofreclamation is only US$ 477.50, andthis would also permit <strong>the</strong> grOWing ofsummer crops, such as soybeans, riceand maize.Table 4. Average cost to reclaim one hectare of Cerrados land, with and withoutirrigation, BraZil, June 1984Cost Percent of total costReclamation needs (US$) Dryland IrrigationFertilizerLime 60 13 5Phosphorus 125 26 10Potassium 50 10 4Micronutrients 35 8 4Subtotal 270 57 23Land preparationClearing 67.5 14 5Liming 17.5 4 1Terracing 15.0 3 1O<strong>the</strong>r 7.5 1 1Subtotal 107.5 22 8Price of virgin Cerrado 100 23 8Total cost, dryland 477.5 100Cost of irrigation system 750 61Total cost with irrigation 1227.5 100Source: Goedert et al. (6)

248The o<strong>the</strong>r economic consideration isthat <strong>the</strong> large initial investment has alow initial return, caused by low yieldsin <strong>the</strong> beginning: this concept is showngraphically in Figure 8. The break-evenpoint is considered to be four to fiveyears, and very few farmers can carrysuch costs for that long. These factorsmay be <strong>the</strong> greatest barriers to wheatproduction in <strong>the</strong> Brazilian Cerrados.Returns....cDeficitProfitI.....CostsTimeFigUre 8. Hypo<strong>the</strong>tical evolution of costs and retarDS on a reclaimedCerrados soilSource: Goedert et al. (6)

249References1. Commisao Norte Brasileira dePesquisa de Trigo. 1982. Brazil.2. EMBRAPA-CPAC. 1976. Relatoriotecnico anual do Centro dePesquisa Agropecuaria dosCerrados 1976. Brazil.3. EMBRAPA-CPAC. 1978. Relatoriotecnico anual do Centro dePesquisa Agropecuarta dosCerrados 1978. Brazil.4. EMBRAPA-CPAC. 1982. Relatoriotecnico anual do Centro dePesquisa Agropecuaria dosCerrados 1982. Brazil.5. Goedert, W.J. 1983. Management of<strong>the</strong> Cerrado soils of Brazil: Areview. Journal of Soil Science34:405-428.'7. Lobato,E. 1980. Adubacaofosfatada em solos solo vegetacaode cerrado. EMBRAPAlCPAC.Planaltina, D.F.• Brazil.8. Lopes. A.S., and F.R. Cox. 1977.Cerrado vegetation in Brazil: anedaphic gradient. AgronomyJournal 69:828-831.9. North Carolina State University.1974. Agronomic-economicresearch on tropical soils. AnnualReport for 1974. Raleigh. NorthCarolina. USA.10. Ritchey. K.D.• D.M.G. Saeza.E. Lobato and O. Correa. 1980.Calcium leaching to increaserooting depth in a Braziliansavannah oxisol. AgronomyJournal 42:40-44.6. Godert. W.J.• D.D.G. Solari andE. Lobato. 1984. Estrategia de uso emanejo do solo. In Solos DosCerrados: Tecnologia e Estrategiasde Manejo. W.J. Goedert, ed.EMBRAPA/Editorial Nobel, SaoPaulo. Brazil.

250Alleviating <strong>the</strong> Constraintsof Acid Soils on Rainfed Wheat in ZambiaR. Little, Zambia-Canada Wheat Research Project, Mount MakuluResearch Station, Chilanga, ZambiaAbstractRainjed wheat cultivation in Zambia is still in <strong>the</strong> early stages ofdevelopment.The major problems ofproduction are diseases and acid sOils. However, acombination ofdisease-resistant and aluminum-tolerant varieties, with limingand optimum seeding date, are now giving yields ofover 2 tlha in trial plots andin afew commerclalftelds. Areas where aluminum toxicity is not a problem arebeing identifled, and <strong>the</strong> size of <strong>the</strong> land area availablefor wheat production isbeing quantifled.Very little rainfed wheat is grown inZambia at present. Attempts to growwheat between 1975 and 1982 werelargely unsuccessful, with yields below1 tfha. due mainly to high diseasepressure (particularly Helminthosporlumsativum). aluminum toxicityand <strong>the</strong> lack of varieties with adequateresistance and tolerance (10). Thesituation is improving with <strong>the</strong> recentintroduction of PF7748 from Brazil. <strong>the</strong>use of lime on acid soils and <strong>the</strong>identification of soils with loweraluminum content.SoilsThe areas of Zambia with reliablerainfall and reasonable rainfalldistribution are mainly in <strong>the</strong> north of<strong>the</strong> country. with an annualprecipitation of more than 1,000 mm.Most of <strong>the</strong> soils in this area are reddishbrown in color. highly leached andchemically poor, with a pH (CaCI2) ofabout 4.0. CEC of 6 to 13 mellOO g clayand BSP of usually less than 25%;aluminum satUration may exceed 60%in <strong>the</strong> subsoil. The soil texture is asandy clay loam. <strong>the</strong> clay fraction beingmainly kaolinite (1,3.4.6). The soils areclassified as typic haplustox or xanthic.orthic or rhodic ferralsols (1.3). Theirhigh aluminum content makes <strong>the</strong>mparticularly problematic for wheatproduction.There are smaller areas of soil developedfrom basic parent materials which arered in color; <strong>the</strong> precise location and sizeof <strong>the</strong>se is not accurately known. Theyhave a higher CEC. approximately 12.20me/100 g clay. a BSP of 25 to 50%. anaverage pH of about 5.0 (2) and analuminum content that is variable, butoften quite low. The iron content in <strong>the</strong>B horizon is very high (average 19%),which probably accounts for <strong>the</strong> goodmicro-aggregation of <strong>the</strong>se soils (4); <strong>the</strong>yare classified as ferralic or cambicarenosols (3).Aluminum toxicitySymptoms of aluminum tOXicity arecommonly expressed as a swelling andthickening and/or darkening of <strong>the</strong> roottips and lateral growth of <strong>the</strong> roots.resulting in shallow rooting. This. intum, usually results in short. weakplants that are very susceptible todrought. since <strong>the</strong> shallow rooting allowslimited access to nutrients and moisturebelow. The pH of <strong>the</strong> soil at <strong>the</strong> ZambiaCanada Wheat Project farm at Katito.Mbala. is about 4.0. with approXimately20 ppm aluminum (extracted in 0.20 MCaCI2). which is highly toxic to wheat.The relationships between pH andaluminum and between aluminum andwheat yield were studied on a field thathad been limed at 2 tfha and plantedwith <strong>the</strong> nontolerant wheat varietyJupateco 73. The distribution of<strong>the</strong> lime

251was ra<strong>the</strong>r poor and <strong>the</strong> crop vigorranged from very poor to good. Soilsamples were taken from nine areaswith differing crop vigor and analyzedfor pH and aluminum. Figure 1 shows avery close correlation between pH andaluminum (r = -0.83). Wheat yieldswere assessed from <strong>the</strong> same nine areasby taking samples of three 0.25 m 2 plotsin each area. Considering <strong>the</strong> small plotsize. <strong>the</strong>re is a very close correlationbetween yield and aluminum content(r = -0.78) (Figure 2).ADeviating <strong>the</strong> effectsof aluminum tozicityLiming-Rates of lime ranging from 0 to8 t/ha, in single and split applications to<strong>the</strong> top 15 cm of soil, have beeninvestigated at Mbala since 1979. Until1983, <strong>the</strong> nontolerant variety Jupateco73 was used, since tolerant varietieswere not available in Zambia(7,8,9,10,11,12). Virtually zero yield wasobtained without lime. Four years oftrials showed increased wheat yields6 •• ••4 •5 15Al + + + (ppm)25Figure 1. Relationship between soli pH and aluminum presence. Zambia3• • •'Ca'2§"d• •- £ •>-1 • ••5 15Al + + +at 0-15 cm (ppm)25Figure 2. Relationship between wheat yield and presence of aluminum ato to US cm soli depth. Zambia

262from <strong>the</strong> application of 1 to 8 tlha oflime (Table I); however, only 2 tlha canbe considered economic, and that onlymarginally so.A long-term trial investigated <strong>the</strong> effecton yield of single and split applicationsof lime over several years. Thetreatments included single applicationsof 2 and 4 tlha in 1979. In Table 2 <strong>the</strong>yield of <strong>the</strong> 2 tlha treatment in 1981 iscompared with <strong>the</strong> 1 tlha treatment in1979, plus 0.5 tlha in 1980 and 1981.Similarly, <strong>the</strong> yield in 1983 of <strong>the</strong> 4 tlhaTable 1. Effect of lime application atdifferent rates on wheat yield, Zambia,1979 to 1982Lime h/ha)o12468!./ Mean 1979 to 1982Yield (kg/ha)!.12785868689319811051treatment is compared with that of 2tlha in 1979, plus 0.5 tlha in each of1980, 1981, 1982 and 1983. Therewere no significant differences in yield.Heavy applications of lime (6 and 8tlha) to <strong>the</strong> top 15 cm of soil havecaused a downward movement ofcalcium through <strong>the</strong> soil profile overtime; <strong>the</strong> lower rates had <strong>the</strong> samereaction, as evidenced by <strong>the</strong> amount ofsoluble aluminum present (Table 3).However, this precipitation of <strong>the</strong>aluminum in <strong>the</strong> lower layers has notresulted in any fur<strong>the</strong>r increase inyield.Trials investigating deeperincorporation of lime have been carriedout for three seasons since 1982(10,11,12). Depths of 0 to 15,0 to 30and 0 to 45 cm have been investigated,with 3 tlha of lime being applied foreach 15 cm of soil. Wheat yields haveincreased with increasing depth ofincorporation, but <strong>the</strong>re has been nobenefit of incorporation to 45 cm ascompared with 30 cm (Table 4). Thepracticality and economics ofincorporation to <strong>the</strong>se depths on acommercial scale are, of course,questionable.Table 2. Comparison of single and split applications of lime on yields ofwheat, Zambia, 1981 and 1983LimeYieldTreatment h/ha) h/ha)1981Single application 2 738Split application!.1 1 +(0.5 x 2) 6851983Single application 4 950Split application!2.1 2 +(0.5 x 4) 969all ton in 1979 and.5 tin 1980 and 1981~/ 1 ton in 1979 and .5 t in 1980, 1981, 1982 and 1983

253Tolerant vartettes-The yield ofvarieties with a wide range ofaluminum tolerance was alsodetennined in <strong>the</strong> trial with deep limeapplications; Table 4 includes yielddata for <strong>the</strong> aluminum-tolerant PF7748.It also responded to deeper liming up to30 cm. but its yields were increased bya factor of less than two; yields ofJupateco 73 were increased by a factorof seven. In <strong>the</strong>se trials. <strong>the</strong> increase inyield as a result of <strong>the</strong> use of <strong>the</strong>_tolerant variety in <strong>the</strong> absence of limewas approximately 800 kglha; whenlime was used. <strong>the</strong> difference was onlyabout 260 kg/ha.Table 3. Presence of aluminum four yearsafter application of lime to <strong>the</strong> top 15 cmof soil, Zambia, 1983Limeapplicationh/ha)o12468Aluminum (ppm)at soil depth15-30 cm 30-45 cm20139105118151919171Considerable effort is being placed on<strong>the</strong> selection of aluminum-tolerantvarieties in Zambia. So far. screeninghas been done in <strong>the</strong> field on unlimedland at Mbala. Lines are entered in anursery consisting of plots of2 x 2 meter rows spaced 20 cm apart ina randomized block design in threereplications. Three rows of each of twocontrol varieties. one tolerant (PF7748)and one nontolerant (Jupateco 73). areseeded along <strong>the</strong> paths between <strong>the</strong>replications at right angles to <strong>the</strong>direction of <strong>the</strong> nursery rows. The samecontrol varietie~ are also included in <strong>the</strong>nursery. Individual plots are scored foraluminum tolerance on a 1 to 9 scale.based on plant Vigor at <strong>the</strong> soft doughstage. relative to <strong>the</strong> controls seeded in<strong>the</strong> pathways (PF7748 set at 3 on <strong>the</strong>scale and Jupateco at 8). This enablesadjustments in scoring which take intoaccount <strong>the</strong> variability in pH andaluminum that occurs in <strong>the</strong> field. Thesame check varieties entered in <strong>the</strong>nursery itself give an added check.Table 4. Effect of depth of incorporation of lime on yields of two wheat cultivars,Zambia, 1983 and 1984!'Limeapplicationh/ha)Jupateco 73Yield % of 0(kg/ha) applicationPF 7748Yield % of 0(kg/ha) applicationMeanYield % of 0(kg/ha) applicationo3 t in top 15 em6 t in top 30 em9 tin top 45 em2221269158015661005727127051014152918551767100151183174618139917181667100226278270,E./ Mean of 1983 and 1984

264In 1983-84, <strong>the</strong> yields of entries in <strong>the</strong>aluminum tolerance nursery weredetermined. Figure 3 shows <strong>the</strong>.correlation between <strong>the</strong> meanaluminum tolerance score and <strong>the</strong>mean yield over <strong>the</strong> three replications(r = -0.88" e).These same entries were also includedin yield trials at Mbala on limed land (atotal of 3.5 Uha of lime applied to <strong>the</strong>top 15 cm over four years), and yieldsfrom <strong>the</strong>se trials (mean of fourreplications from net plot sizes of0.6 x 6 m) have also been correlatedwith <strong>the</strong> aluminum-tolerance scores(Figure 4). The correlation coefficient isagain very large, negative and highlysignificant (r = -0.88* e). This indicatesthat subsoil acidity is playing asignificant role in <strong>the</strong> determination ofyield on limed soils. Liming increasesyield but those varieties haVing pooraluminum tolerance are affected bysubsoil acidity. Therefore, <strong>the</strong> value ofaluminum-tolerant varieties is againevident.Early planting-Aluminum tOXicitycauses sensitive, shallow rooted plantsto be highly susceptible to drought,since <strong>the</strong>y require frequentprecipitation to obtain sufficientmoisture from <strong>the</strong> surface layers of <strong>the</strong>soil. If <strong>the</strong> rains finish early, <strong>the</strong> cropcan suffer qUickly and severely fromdrought; early planting allows <strong>the</strong>grain-filling stages of <strong>the</strong> crop to occurbefore <strong>the</strong> rains normally finish.However, this benefit may be off-set byincreased disease pressure, due to <strong>the</strong>enhancement of disease developmentby <strong>the</strong> wetter conditions. Currently, <strong>the</strong>optimum planting date is a compromisefor minimizing disease pressure anddrought stress. Varieties with morealuminum tolerance and diseaseresistance will extend this period andreduce risks.1000Ci..c::•Y = -159 x + 1556~-'tlCIJ 500 •- >-• ••3 4 5 6 7 8High Al + + + tolerance LowFigure 3. Relationship of wheat yields on unllmed soU and aluminumtolerancerating of <strong>the</strong> cultivar, Zambia, 1983-84

255Alternative locations-An evaluation ofmore suitable areas, those with lessacid soils, is being undertaken forgrowing rainfed wheat in Zambia.Twenty sites from Magoye in <strong>the</strong> southand Mbala and Nakonde in <strong>the</strong> northhave been planted at two seeding datesand with <strong>the</strong> best available varieties.The preliminary results indicatepromising areas near Nakonde andMpika and also between Serenje andMpika. These areas are now being,fur<strong>the</strong>r surveyed to determine <strong>the</strong>extent of <strong>the</strong> potential areas.ConclusionsYields of about 2.5 tlha are nowbeing obtained in rainfed wheat trials inZambia. These have been achieved bycombining <strong>the</strong> use of varieties tolerantto aluminum and resistant to diseaseswith liming (at about 2 tlha on acidsoils) or growing on soils with a pH(CaCI2) of about 5.0, where aluminumtoxicity is very much reduced orabsent. Currently recommendedfertilizer rates are approximately 20 kgNlha (basal), 100 kg Nlha (top dressing).54 kglha phosphorus, 36 kg/hapotassium, 30 kglha sulphur and 0.3kglha boron.AcknowledgementsThe use of data of colleagues of <strong>the</strong>Zambia-Canada Wheat ResearchProject, B. Aulakh, J. Brandle,L. Hodgins, G. Musa and D. Penney. isgreatfully acknowledged. The authoralso thanks J.R. Boyer. M. Hangala,S.K. Hartley, M.M. Mwanamwenge andM. Ngwele for <strong>the</strong>ir technical assistance,as well as Mrs. S. Wateridge for typingand J. Little for preparation of <strong>the</strong>figures.2000••• •Y = -315 x +3152•" i 3Highi4 5Al + + + tolerancei6i7i8LowFigure 4. RelatioDship of wheat yields on limed soil and aluminumtolerancerating of <strong>the</strong> cultlvar. Zambia. 1983-84

258References1. Brammer, H. 1973. Soils of Zambia.Soil Survey Report 11. Mt. MakuluResearch Station, Chilanga,Zambia.2. Kalima, C. 1980. Detailed soilsurvey of Mpika dairy settlementscheme. Soil Survey Unit, MpikaDistrict, Nor<strong>the</strong>rn Province. Mt.Makulu Research Station, Kasama,Chilanga, Zambia.3. Kalbna,C. 1983. Thecharacterization, distribution andextent of major soils of <strong>the</strong> highrainfall areas of Zambia. InProceedings of <strong>the</strong> Seminar on SoilProductivity in <strong>the</strong> High RainfallAreas of Zambia. Lusaka, February8-10, 1983. Occasional Paper 6.H. Svads, ed. InternationalDevelopment Programs,Agricultural University of Norway,As, Norway.4. Mansfield, J.E., J.G. Bennett,R.B. King, D.M. Lang and R.M.Lawton. 1975. Land resources ofNor<strong>the</strong>rn and Luapula provinces ofZambia: A reconnaissanceassessment. Study 19, vols. 3,4and 5. Land Resources Division,Overseas DevelopmentAdministration, London, England.5. Penney, D.C., L.W. Hodgins andB.S. Aulakh. 1981. Miscellaneousreport of <strong>the</strong> Zambia-Canada WheatProject. Chilanga, Zambia.6. Vikan, J.G. 1983. Preliminaryexploratory map of <strong>the</strong> Nor<strong>the</strong>rnand Luapula provinces:Contribution to <strong>the</strong> study of <strong>the</strong>soils of <strong>the</strong> high rainfall area. SoilSurvey Unit, Mt Makulu ResearchStation, Kasama, Chilanga. Zambia.7. Zambia-Canada Wheat ProjectAnnual Report 1979. Chilanga,Zambia.8. Zambia-Canada Wheat ProjectAnnual Report 1980. Chilanga,Zambia.9. Zambia-Canada Wheat ProjectAnnual Report 1981. Chilanga,Zambia.10. Zambia-Canada Wheat ProjectAnnual Report 1982. Chilanga,Zambia.11. Zambia-Canada Wheat ProjectAnnual Report 1983. Chilanga.Zambia.12. Zambia-Canada Wheat ProjectAnnual Report 1984. Chilanga,Zambia. (In press.)

257Wheat Production Constraintsand Management in BangladeshM. GuIer, Wheat Program, CIMMYT, Joydebpur, Dhaka, BangladeshAbstractThe average temperature is quite similar in all of<strong>the</strong> wheat-growing areas ofBangladesh. The amount and distribution of <strong>the</strong> monsoon rains and <strong>the</strong>differences in soil texture and elevation affect <strong>the</strong> flood situation. which in turnaffects <strong>the</strong> selection ofcropping systems by <strong>the</strong>farmers; <strong>the</strong> cropping systemhas a great effect on wheat yields. The main management problems of wheatfarmers are <strong>the</strong>jitting ofwheat into <strong>the</strong> system, land preparation. time ofseeding andfertilization.A study of <strong>the</strong> climatic conditions of <strong>the</strong>different wheat-growing areas ofBangladesh would reveal no greatdifferences in average dailytemperature, but significant differencesin <strong>the</strong> amount of average annualrainfall and its distribution. Table 1shows total annual rainfall and that of<strong>the</strong> wheat-growing season.Although <strong>the</strong> annual rainfall is veryhigh in all locations, ranging fromabout 1600 mm in <strong>the</strong> west to 2300mm in <strong>the</strong> east. only a small portion ofthis amount falls during <strong>the</strong> wheatseason. However, <strong>the</strong> amount and <strong>the</strong>distribution of rainfall in <strong>the</strong> monsoonseason in different locations affects <strong>the</strong>time of planting and harvesting of <strong>the</strong>preceding rice crop; this. in turn, affects<strong>the</strong> seeding time of wheat.Ano<strong>the</strong>r important ecological factor forwheat growth is soil texture. InBangladesh, wheat is grown in almostall soils except <strong>the</strong> very heavy-texturedsoils. Textural differences in soils causedifferences in soil moisture, which inturn affects <strong>the</strong> timing and intensity oftillage operations. as well as <strong>the</strong> wheatyield level.Ten percent of <strong>the</strong> wheat-growing areaof Bangladesh is classified as upland.with rice being grown without wetlandpreparation or transplanting and withcomplete dependence on rainfall formoisture (2). In <strong>the</strong>se areas. <strong>the</strong>favorable wheat-seeding date rangesbetween mid-November and earlyDecember; because of <strong>the</strong> croppingsystem chosen by <strong>the</strong> farmers, whichTable 1. Rainfall in six locations, BangladeshLocationAverage rainfall (mm)Annual Wheat season(Nov-March)Dinajpur (northwest)Bogra (west)Ishurdi (west)Jessore (southwest)Jamalpur (north)Comilla (east)Source: Manalo (1)177817561585165222412298537675104115151

258enables an earlier harvest of <strong>the</strong>preceding rice crop and earlier dryirig of<strong>the</strong> soil. it is possible to seed wheat at afavorable date. The remaining 90% of<strong>the</strong> wheat-growing areas are broadlyclassified as lowland. There are largevariations in <strong>the</strong>se lowland areas.depending on <strong>the</strong> amount anddistribution of rainfall and <strong>the</strong> textureof <strong>the</strong> soil.In Bangladesh. three crops a year arepossible. depending on <strong>the</strong> abovementionedconditions and irrigationfacilities. The most popular rotationsystems including wheat are wheat-ricericeand wheat-fallow-rice.Different cropping systems areemployed in different areas ofBangladesh. according to <strong>the</strong>occurrence of flood or drought during<strong>the</strong> monsoon season and because ofdifferences in elevation, soil texture anddistribution of rainfall. All of <strong>the</strong>sefactors have profound effects on wheatproduction in terms of managementpractices. The main managementproblems may be classified as:• The addition of wheat to <strong>the</strong>preVailing cropping system as <strong>the</strong>second or third crop;• Land preparation methods;• Selection of varieties;• Optimum seeding rate and method.and• Rate of fertilization and method ofapplication.Research Approachesin BangladeshFertilizationSince wheat is a relatively new crop in<strong>the</strong> country. many farmers still havereservations concerning its value. Abelief shared by many farmers is thatwheat reduces <strong>the</strong> yield of <strong>the</strong> follOWingrice crop. This problem is being studiedin a series of fertility experiments.conducted in ten locations on farmers'fields. It was assumed that <strong>the</strong> nutrientuptake of wheat resulted in lower yieldsof <strong>the</strong> follOWing rice crop because ofinsufficient application of necessarynutrients to wheat. A split-plot designwas used in <strong>the</strong>se experiments. inwhich applications of nitrogen.phosphorus. potassium and sulphur towheat were main plots. and <strong>the</strong>application of <strong>the</strong> same nutrients to <strong>the</strong>follOWing rice crop were subplots. Theexperiments will be evaluated after <strong>the</strong>harvest of <strong>the</strong> rice crop.TillageSince 75% of <strong>the</strong> wheat in Bangladeshis still grown under non-irrigatedconditions. most of <strong>the</strong> crop isdependent upon residual moisture in<strong>the</strong> soil. In order to determine whichland preparation method will make <strong>the</strong>best use of residual moisture in <strong>the</strong>earliest and most economical manner.on-station and on-farm experimentscomparing minimum tillage withtraditional practices are beingconducted. Results thus far indicatethat. in light and medium-texturedsoils. <strong>the</strong>re is no significant yielddifference between minimum tillage(seeds sown in rows opened by acountry plow and covered with <strong>the</strong> foot)and traditional tillage (plOWing four tofive times with a bullock-drawn countryplow and smoothing <strong>the</strong> soil surfaceafter each plOWing); in heavier texturedsoils. higher wheat yields have beenobtained from minimum tillage.Planting dateThe time of seeding depends upon <strong>the</strong>harvest of <strong>the</strong> preceding crop and/or <strong>the</strong>water status of <strong>the</strong> soil. The time ofseeding is one of <strong>the</strong> most importantfactors affecting yield. An experimentwas conducted in two locations toevaluate <strong>the</strong> performance of severalwheat varieties at different dates ofseeding. For each variety. a linearregression of individual variety yield on<strong>the</strong> mean yield of all varieties wascomputed. The mean yields of allvarieties at different dates proVided a

259numerical grading which showed <strong>the</strong>yield potential for each date. Then, <strong>the</strong>individual variety yields were plottedagainst <strong>the</strong> mean of all variety yields.according to <strong>the</strong> regression equationsobtained. Although <strong>the</strong> yield differencesamong <strong>the</strong> varieties were within a rangeof 0.5 tlha when <strong>the</strong> mean of all varietieswas 4.5 tlha at <strong>the</strong> optimum date ofseeding. this range was close to 1 t/ha atlater dates of seeding when <strong>the</strong> meanyield was approximately 2 t/ha. Theseresults demonstrated <strong>the</strong> greatimportance of selecting appropriatevarieties for later seeding dates(Figure 1). Most of <strong>the</strong> newly releasedvarieties performed better than Sonalika.which currently occupies more than75% of <strong>the</strong> wheat area. The varietiesKanchan. Akbar and Barkat yieldedbetter than <strong>the</strong> mean of all varieties atoptimum dates of seeding. while Barkat.Balaka and Akbar performed betterwhen sown at later dates.O<strong>the</strong>r research areasResearch on seeding rate, nutrient rateand seeding and fertilizer applicationmethods has been conducted withcompetence and success throughout<strong>the</strong> country since 1974. Somerecommendations for farmers areavailable as a result of this research.References1. Manalo, RE. Agro-climatic Surveyof Bangladesh. BRRI and IRRI,Dhaka. Bangladesh.2. Zaman. S.M.H. 1983. Currentstatus and prospects for rainfedfoodgrain production inBangladesh. Paper prepared forFAO's Expert Group Consultation.November 28-December 2. 1983,Bangkok. Thailand.Variety mean yield (Uha)5.5Variety mean yield (Uha)Barkat....... 1.5................ Balaka.... AkbarKanchanArandaAkbarBarkatOverall mean 5.0+-__f-top.o::::;..__~",,":-~_~ +- -+ 1.0 Overall meanSonalikaBalakaArandaPavon4.5KanchanSonalika0.5Pavon5Nov 15432Dec 1 Dec 15 Jan 1 Jan 15Mean yields of all varieties (t/ha)1Figure 1. Yields of seven wheat varieties according to planting date.Bangladesh

260Agronomic Management Issues forWheat Production in More TropicalEnvironments of Sou<strong>the</strong>ast AsiaD.A. Saunders, Wheat Program, CIMMYT, Bangkok, ThailandAbstractWheat is not intended as a competitor to established crops in Sou<strong>the</strong>ast Asia;ra<strong>the</strong>r, due to its relative water efficiency, it is expected to produce crops wherenone are presently grown. Where some irrigation is available. managementmust be directed towards avoidance of waterlogging. particularly duringestablishment. Under rainfed conditions. <strong>the</strong> correct timing ofsowing and <strong>the</strong>conservation ofsoil moisture are keyfactors. Strategies can involve reducedcultivation depth. reduced or zero tillage and straw mulching. Weed populationsare high in both irrigated and rainfed areas. necessitating excessive labor inputsfor control by hand weeding: chemicals to control major weed species have beenidentified. Response to nitrogenfertilizer is normally obtained. but responses tophosphorus have not been consistent.Wheat has been cultivated on restrictedareas. mainly at high altitudes. inSou<strong>the</strong>ast Asia for many years; it isnow proposed that it might be grown atlower elevations where a larger landpotential exists. This interest has beenstimulated by <strong>the</strong> increasingconsumption of wheat products(approximately 12% per annum)throughout <strong>the</strong> region.There are basically two situationswhere wheat may be fitted into existingfarming systems without competingwith o<strong>the</strong>r well-adapted crops. The firstis in areas where dry-season irrigationis not aVailable, and <strong>the</strong> crop would begrown on residual moisture plus anyrainfall during <strong>the</strong> crop cycle. Thisencompasses rainfed paddy. after rice,and upland areas. usually follOWingmaize. The o<strong>the</strong>r situation is in lowlandsoils. follOWing rice. where <strong>the</strong> quantityor availability of irrigation water cannotsustain ano<strong>the</strong>r rice crop. Presentmanagement aims to maximize <strong>the</strong>yield of relatively unadapted varietieswithin <strong>the</strong> climatic and croppingsystemsrestraints.Soil and Water ManagementPreliminary estimates of crop-water usesuggest that a successful rainfed cropmay be grown on about 350 mm ofwater in nor<strong>the</strong>rn Thailand. and that <strong>the</strong>greatest chance of success is where <strong>the</strong>upper 1.5 meters of soU has an availablewater content (AWe) of approximately250 mm (14). This recommendationwould be affected by <strong>the</strong> expectation ofrainfall dUring <strong>the</strong> crop cycle and <strong>the</strong>influence of a shallow water table (22).The objective in <strong>the</strong> rainfed situation isto commence <strong>the</strong> crop in a full soilprofile. while avoiding periods ofprolonged waterlogging. On upland soilsthis presents few difficulties; <strong>the</strong> farmerhas sufficient time to prepare <strong>the</strong>seedbed (due to early harvest of <strong>the</strong> priorcrop in <strong>the</strong> rotation) and merely seedsinto a full profile when <strong>the</strong> probability ofcontinuous, heavy rainfall hasdecreased.On rainfed paddy. wheat seeding wouldoften be delayed beyond <strong>the</strong> optimaltime (in relation to rainfall probabilities).due to <strong>the</strong> utilization of long growingseason rice varieties (8); cropestablishment systems should be

261directed towards minimum loss of soilmoisture. In <strong>the</strong>se heavy soils, <strong>the</strong>practice of ra<strong>the</strong>r deep tillage createslarge clods which are difficult and timeconsumingto break down and,<strong>the</strong>refore, during this time, soil moistureis lost (16). The more intensive <strong>the</strong>tillage, <strong>the</strong> greater <strong>the</strong> moisture loss (21).There should be a reduction of tillagedepth, preferably not deeper than 5 cm,to reduce moisture loss from <strong>the</strong> lowersoil layers (22). In many areas wherehand tractors are becoming widespread(e.g., Philippines, Sumatra, Indonesiaand nor<strong>the</strong>rn Thailand), this would bepossible through <strong>the</strong> use of rototillers forcreating a fine mulch of soil and strawresidue.Alternatively, rice straw can be utilizedas mulch. Impressive yield increases .have been reported in <strong>the</strong> Philippines fora number of upland crops follOWing rice,soybeans and mungbean (11), maize (21)and wheat (S.P. Liboon. personalcommunication). Among <strong>the</strong> benefits ofmulching are reduced evaporation andincreased infiltration (10), lower soiltemperature (4) and improved fertilizeravailability (21). Of course, <strong>the</strong>aVailability of straw, <strong>the</strong> economics of<strong>the</strong> operation and <strong>the</strong> effects on plantdiseases must be considered.Ano<strong>the</strong>r strategy could be to use zero orminimum tillage methods, afterburning <strong>the</strong> rice stubble or in <strong>the</strong>standing straw; <strong>the</strong> latter reducesmoisture loss (21). Direct seeding byvarious methods, and seeding follOWingconventional tillage have resulted incomparable yields in <strong>the</strong> Philippines(S.P. Libbon. personal communication).In <strong>the</strong> extreme. wheat has been relaycropped in rice in Taiwan (6). However,weed populations are usually greaterwith reduced tillage systems (13,20),and ratoon growth of rice could causeproblems. Surface-applied fertilizers,particularly phosphorus, may also bepoorly utilized (9), and some diseaseproblems such as Sclerotium rolfsiimay be increased (12).In lowland situations where limitedirrigation is possible. water willnormally be available, at least for cropestablishment. The most consistentmanagement problem on paddy land isthat of <strong>the</strong> waterlogging of <strong>the</strong> crop,particularly in <strong>the</strong> establishment phase,ei<strong>the</strong>r through too much water beingapplied or through insufficient drainageafter irrigation. It is recommended thatpre-irrigation follOWing seedbedpreparation be practiced. and <strong>the</strong> seedsown into drained soil. Whereinundation from rainfall or uncontrolledwater is a possibility, a bed or ridge andfurrow system of culture should befollowed. Small differences in microreliefhave resulted in large effects oncrop survival and development.Alternatively. drainage canals at regularintervals could be prOVided (20).Present indications are that wellcontrolledirrigations at any cropgrowth stage between early tilleringand milk stage increase yield. Thelargest effect from a single irrigation isat <strong>the</strong> early booting stage of cropdevelopment (S.P. Liboon and B.Rerkasem, personal communication).Weed ControlThe predominant grass weeds in wheatare various species of Digitaria,Eragrostis, Eleusine and Echinochloa;broadleaf weeds include Amaranthusspp., Trian<strong>the</strong>ma portulacastrum andPortulaca oleracea. Volunteer rice canalso create a serious problem.The low yields of wheat currentlyattained under rainfed conditionsprecludes intensive weed control.Where some supplementary irrigation isavailable, <strong>the</strong> increased yield potentialshould encourage more thorough weedcontrol. Data suggest that <strong>the</strong> criticalperiod dUring which weeds must becontrolled is <strong>the</strong> first five weeks aftersowing (5).

262In pilot sowings in <strong>the</strong> Philippines. <strong>the</strong>average labor expenditure for handweeding has been about 25 man daysper hectare (12). although somefarmers' fields have required doublethis amount. Mechanical aids toweeding (rotary hand weeders. hingedhand hoes. bullock-drawn shallowplows and harrow weeders) are beingpromoted. However. a cheaper andmore satisfactory solution in <strong>the</strong> futuremight be chemical weed control.Some commercially aVailable herbicides(e.g.. Butachlor. Alachlor. Oxadiazonand Isoproturon) have been testedexperimentally with acceptable results(5.18.19). However. in practice. <strong>the</strong>rehave been phytotoxicity problems with<strong>the</strong>ir use. related to <strong>the</strong> level of soilmoisture following application and toseeding depth. Recently. a wider rangeof chemicals have been tested inThailand and in <strong>the</strong> Philippines. Theseexperiments have consistentlydemonstrated that a Diclofop-methyland Chlorsulfuron mixture adequatelycontrols weeds. including volunteerrice.Fertilizer TechnologyYield responses to nitrogen have beenobtained from applications of up to 40kg of nitrogen per ha in rainfed upland(14) and lowland conditions (S.P. Liboon.personal communication). and 80 to 120kglha with irrigation (15. S.P. Liboon.personal communication). In noexperiment has split nitrogenapplication demonstrated a clear yieldadvantage over totally basal application(5. S.P. Liboon and O. Werasopon.personal communication). Phosphoruslevels measured in many soils in <strong>the</strong>region are low (often less than 5 ppm.using <strong>the</strong> Bray II method). It issurprising. <strong>the</strong>n. that virtually noresponse to phospa<strong>the</strong> fertilizers hasbeen obtained, even at rates up to300 kg of P205 per hatThere have been no responses topotassium. and little experimentation ono<strong>the</strong>r elements. However. <strong>the</strong> generallylow yields obtained with adequatemo~ture. nitrogen. phosphorus andpotassium. <strong>the</strong> response to organicmanure in nor<strong>the</strong>rn Thailand (17) and astudy of micronutrient deficiencesltoxicities in Asian paddy soils (7)indicate this to be a potentiallyproductive area of study.References1. Abon. C. 1984. Wheat pilot projectin Nueva Ecija. Report of <strong>the</strong>Research and Development Center.CLSU. Munoz. Nueva Ecija.Philippines.2. Anonymous. 1983. The nationalcoordinated wheat pilot project.Progress Report. PCARRD.Philippines.3. Anukularmphai. A.. M.Shabiruzzaman and M. EnayetUllah. 1980. Rainfall andevaporation analyses of Thailand.Division of Agricultural and FoodEngineering. The Asian Institute ofTechnology. Bangkok. Thailand.4. Benoit. G.R.. and D. Kirkham.1963. The effect of soil surfaceconditions on evaporation of soilwater. Soil Science Society ofAmerica Journal 27:495-498..5. Campos. F.• R. Tabien. R. Camachoand C. Aganon. 1982. Syn<strong>the</strong>sis ofresearch results on wheat at CLSU.Report of <strong>the</strong> Wheat Research andDevelopment Program. CLSU.Munoz. Nueva Ecija. Philippines.

'.2636. Cheng, C.P. 1977. Wheatproduction in Taiwan under amultiple cropping system. ASPACExtension Bulletin 94. Taiwan.7. Domingo, L.E., and K. Kyuma.1984. Geographical distribution ofpotential problem areas withmicronutrient anomalies in tropicalAsian paddy soils. Journal ofSou<strong>the</strong>ast Asian Studies 21:361373.8. Gypmantasiri. P., A.Wiboonpongse, B. Rerkasem, I.Craig, K. Rerkasem, L. Ganjanapan,M. Titayawan, M. Seetisarn, P.Thani, R Jaisaard, SomchaiOngprasert, T. Radanachaless andG. Conway. 1980. Aninterdisciplinary perspective ofcropping systems in <strong>the</strong> Chiang MaiValley: Key questions for research.Faculty of Agriculture, Chiang MaiUniversity, Chiang Mai, Thailand.9. Kang, B.T., and A.D. Messan. 1983.Fertilizer management for no-tillagecrop production. In No-tillage CropProduction in <strong>the</strong> Tropics. IPPC,Oregon State University, Corvallis,Oregon, USA. Pp. 111-118.10. Lal, R 1975. Role of mulchingtechniques in tropical soil andwater management. lITA TechnicalBulletin 1. Ibadan, Nigeria.11. Lantican, RM. 1977. Field cropsbreeding for multiple croppingpattern. In Proceedings of <strong>the</strong><strong>Symposium</strong> on Cropping SystemsResearch and Development for <strong>the</strong>Asian Rice Farmer. IRRI, LosBanos, Philippines. Pp. 349-357.12. Mew, T.W., and F.A. Elazegui.1982. Disease problems in uplandcrops grown before and afterwetland rice. Report of Workshopon Cropping Systems Research inAsia. IRRI, Los Banos. Philippines.Pp.99-116.13. Moody, K. 1977. Weed control inmultiple cropping. In Proceedingsof <strong>the</strong> <strong>Symposium</strong> on CroppingSystems and Development for <strong>the</strong>Asian Rice Farmer. IRRI, LosBanos, Philippines. Pp. 281-299.14. Norman. B.W. 1982. Rainfed wheatproduction in Chiang Rai.Proceedings of <strong>the</strong> Third AnnualWheat Workshop. Thailand. Pp.282-310.15. Pagaduan-Aganon, C. 1984.Fertilizer trial in wheat at CLSU.Research and Development CenterTechnical Report 1. CLSU, Munoz.Nueva Ecija. Philippines.16. Sanchez, P.A. 1976. Properties andmanagement of soil in <strong>the</strong> tropics.In Soil Management in MultipleCropping Systems. John Wiiey andSons, New York. USA. Chapter 12.17. Srtkaew, P.. and B. Rerkasem(unpublished). Cited in Rerkasem.K.. and B. Rerkasem. 1984. Organicmanures in intensive croppingsystems. In Organic Matter andRice. IRRI. Los Banos. Philippines.Pp.517-532.

26418. Suwanketnikom. R.. O.Tantawiroon. S. Srisawat andT. Baibang. 1982. Pre-emergenceherbicides application in wheat. InProceedings of <strong>the</strong> Third AnnualWheat Workshop. Thailand. Pp.310-320.19. Suwanketnikom. R.. O.Tantawiroon. S. Srisawat andT. Baibang. 1982. Post-emergenceherbicides application in wheat. InProceedings of <strong>the</strong> Third AnnualWheat Workshop. Thailand. Pp.321-327.20. Syarifuddin. A.K. 1982. TUlagepractices and methods of seedingupland crops after wetland rice.Report of <strong>the</strong> Workshop onCropping Systems Research inAsia. IRRI. Los Banos. Philippines.Pp.33-42.21. Syarifuddin. A.K.. andH.G. Zandstra. 1978. GrOWingrainfed corn and soybeans afterpuddled flooded rice: I. SOil physicalconditions and management. IRRISaturday Seminar. November 4.1978. Los Banos. Philippines.22. Zandstra. H.G. 1982. Effect of soilmoisture and texture on <strong>the</strong> growthof upland crops after wetland rice.Report of <strong>the</strong> Workshop onCropping Systems Research inAsia. IRRI. Los Banos. Philippines.Pp.43-54.

Wheat in Rice...BasedCropping Systems in ThailandK. Rerkasem and B. Rerkasem. Multiple Cropping Project. ChiangMai University. Chiang Mai. ThailandAbstract265Rice-based multiple cropping in Thailand is currently restricted by <strong>the</strong> lowtemperatures of<strong>the</strong> season after rice harvest; this limits <strong>the</strong> growing of tropicaland subtropical crop species, such as rice or soybeans. The shortage ofirrigationwater after December is also a restriction. A rice-wheat system, with wheat'sadaptability to a cool season and its relative tolerance to water stress, offers amore efficient use oflimited resources. The requirementfor early rice harvestcan easily be met by choosingfrom a wide range ofearly rice varieties,traditional ones as well as <strong>the</strong> new IRRI types. In terms ofmanagement, landpreparation may be a major problem as well as micro-nutrient deflciences.Seasonal and spatial distribution ofirrigation water must be considered indetermining <strong>the</strong> potential area of rice-wheat cropping in nor<strong>the</strong>rn Thailand.The Potential of Wheat inRice-Based Cropping SystemsIn nor<strong>the</strong>rn Thailand, where wheatappears to have some potential, <strong>the</strong>reare about 0.5 million hectares ofirrigated rice land; this is <strong>the</strong> possiblearea for a rice-wheat cropping system.A typical regime of rainfall andtemperature for nor<strong>the</strong>rn Thailand isshown in Figure 1. The rains end quitesuddenly in October, so that any dryseasoncropping after rice must rely onirrigation. The period from November toFebruary has sufficiently lowtemperature for temperate crops suchas wheat to be grown, but <strong>the</strong> low nighttemperatures may limit tropical crops.The planting of soybeans, <strong>the</strong> majorcrop grown after rice, must wait until<strong>the</strong> end of December, because of lownight temperatures; <strong>the</strong>re is an evenlonger delay for dry-season rice.Because of this, <strong>the</strong> current growingseason for a rice-based cropping systemmust extend to April or even later.Wheat, on <strong>the</strong> o<strong>the</strong>r hand, has beensuccessfully planted in October andNovember, with an averageexperimental yield of 3.6 Uha and abest yield of 5 tJha with INIA 66. Thelower evaporative demand fromNovember to February also can lead tomuch better water-use efficiency. O<strong>the</strong>rcrops which currently utilize <strong>the</strong> coolseason are garlic. vegetables andtobacco. Their total area is relativelylimited, due to restricted demand. Ricewheatoffers an improvement in landand water-use efficiency. with itsshorter growing season and betteradaptation to cool wea<strong>the</strong>r (Figure 2).However, <strong>the</strong>re are several agronomicconsiderations that may haveimplications on large-scale adoption of<strong>the</strong> rice-wheat system in nor<strong>the</strong>rnThailand.Management Problemsof Wheat after RicePlanting dateThe growing season for wheat innor<strong>the</strong>rn Thailand is relatively short(Figure 1). It is essential that <strong>the</strong> cropbe planted as early as possible. beforetemperatures begin to rise again.Results from planting-date studies varyconsiderably from year to year. possiblydue to slight variations in <strong>the</strong> length of<strong>the</strong> cool season. The latest date that <strong>the</strong>currently available varieties. such asINIA 66 and CMU26. can be plantedwithout drastic yield reduction rangesfrom <strong>the</strong> end of November to midDecember (2).

288300RainfallPotentialEvapotransporation"",-'---..._------- ,'",.'"25I::·cuI.,20.... 160en~ 10Cl5U 0--25Q)I.,.... ='~ I.,Q)~ 15 SQ)E-

267Rice varietiesAs mentioned above, early planting ofwheat is essential; it follows that <strong>the</strong>preceding rice crop must be harvestedearly. The range of maturity that existsin rice germplasm now available innor<strong>the</strong>rn Thailand is considerable (1).There are traditional, photosensitivevarieties which seem to respond tophotoperiod changes while <strong>the</strong> days arestill much longer than reqUired toinduce flowering in full-season varieties.These early varieties, which can beginto be harvested in early October, havelong been used in rice-based croppingsystems which require early riceharvest, such as rice-shallot, rice-garlicand rice-tobacco. New IRRI-type RDvarieties which are not sensitive tophotoperiod, e.g., RDl, RD7 and RDIO,offer more alternatives for earliness inrice. Although all of <strong>the</strong>se early ricesare somewhat inferior to full-seasonvarieties, experience from <strong>the</strong> villageprogram of <strong>the</strong> Multiple CroppingProject has shown that farmers arewilling to sustain this loss in <strong>the</strong> ricecrop if it can later be compensated forby <strong>the</strong> following crop.SoliRice-based multiple cropping involVingupland crops is somewhat ofananomaly. During <strong>the</strong> rice season, <strong>the</strong>main objective in soil management is tokeep <strong>the</strong> water in <strong>the</strong> field. This isachieved with puddling, whicheffectively destroys any structure that<strong>the</strong> soil may have; <strong>the</strong> original structuremay be regenerated only in certain soiltypes. For o<strong>the</strong>r soils, management oftillage, water and organic manure iscrucial in <strong>the</strong> modification of soilstructure, especially during <strong>the</strong> earlyestablishment of <strong>the</strong> crop.Unfortunately, <strong>the</strong> majority of rice soilsin nor<strong>the</strong>rn Thailand belong to thisgroup, and <strong>the</strong> management of tillageand water are extremely critical towheat yield. Organic manure is nowextensively used for high-value crops,but will not be <strong>the</strong> solution for wheat.Satisfactory germination andestablishment have been achieved bysowing into moist soil and floodirrigating in subsequent applications. Asuccessful practice is that of sowingPresent SystemsA./R _ic _e,.,7 A./ S_O_y_b_e_an /,/ R_ic_e/JA./ Ri_c_e /Proposed Rice-WheatWheat/Rice7/7Jul Aug Sepi i i I i I iOct Nov Dec Jan Feb Mar Apr May JunMonthFigure 2. The growing season of a rice-wheat cropping system comparedwith <strong>the</strong> ezisting rice-soybean and rice-rice systems. nor<strong>the</strong>rn Thailand

268directly into <strong>the</strong> rice stubble, as iscommonly done with soybeans.Preliminary studies have shown that<strong>the</strong> growth of wheat in rice stubble isbetter than in tilled soll (Table 1). Themethod of sowing wheat into stubbledeserves fur<strong>the</strong>r attention. Thepopulation density of wheat needs to be16 to 20 hills per square meter, higherthan <strong>the</strong> original spacing of <strong>the</strong> old ricecrowns.Yield decUneIn <strong>the</strong> last twenty years, <strong>the</strong>re has beena remarkably rapid expansion ofmultiple cropping in nor<strong>the</strong>rn Thailand.Table 1. A comparison of wheat yields from stubble-sown and conventional tillage, ThailandConventional tillageStubble-sown(plantslm2)Density effects (50 plantslm2) 150 45 112Yield h/ha)Grain 1.84 2.18 0.30 1.00Straw 1.83 2.20 0.70 0.80Total dry matter 3.67 4.38 1.00 1.80Yield (g!plant)Grain 3.68 1.45 0.67 0.89Straw 3.66 1.47 1.56 0.71Total dry matter 7.34 2.92 2.22 1.60Source: Jongkaewwatana, S., and K; Rerkasem. 1982. A study of yield~ensityrelationshipon wheat in a rice-wheat system (in Thai). In Proceedings of <strong>the</strong> Third NationalWinter Grain Workshop, Nor<strong>the</strong>rn Agricultural Development Centre, Bangkok,Thailand.Table 2. Responses to boron application on upland crops grown in rice-based systems,Chiang Mai, ThailandBorax application(kg/ha) .Grain yield(g/m2)Sunflower~/Mungbean Jl!0 74.68 169.46.7 298.476.7 +Zn 277.3110 428.90 311.4Sunflower Soybeans Peanut Wheat0 188.49 197.98 144.66 219.2910 314.88 207.48 157.37 219.1220 295.38 207.45 130.90 215.8140 311.11 160.26 141.86 189.56~/ Grown in sunflower-mungbeal1-rice system9,/ Dry matter yield

269A problem of declining yields has beenidentified in a long-term study of wheatwithin intensive rice-based croppingsystems; similar symptoms have beenobserved in farmers' fields inintensively multiple-cropped areas inChiang Mai (1.3). Micro-nutrientdepletion is one likely cause. Wheat hasresponded markedly to a mixture ofboron. copper. zinc and magnesium.but <strong>the</strong> response to animal manure iseven stronger (5). Respons6s to boronhave been observed in sunflower.mungbean and blackgram. but not inwheat, soybeans or peanuts (Table 2).This soil deficiency problem may be amajor factor limiting yield potential ofwheat in this environment.Water stressAs <strong>the</strong> dry season progresses. watershortage becomes <strong>the</strong> most criticalproblem faced by farmers. FromNovember 1983 to March 1984. anexperiment was carried out at <strong>the</strong>Multiple Cropping Project at Chiang Maito evaluate <strong>the</strong> effects of water stress onwheat yield (Table 3). Wheat appears tobe tolerant to water stress in thisenvironment. Receiving only threeirrigations in <strong>the</strong> first four weeks. <strong>the</strong>crop still yielded 75% of <strong>the</strong> maximumyield obtained with full irrigation.Omitting one irrigation at boot reducedyield slightly; <strong>the</strong>re was a more markedreduction when an irrigation wasmissed at an<strong>the</strong>sis. Yield wasunaffected by <strong>the</strong> omission of oneirrigation at crown root initiation.tillering or grain filling.Wheat in <strong>the</strong> AgriculturalSystem of Nortliern ThailandIn addition to agronomic feasibility. <strong>the</strong>main questions related to <strong>the</strong>introduction of <strong>the</strong> rice-wheat systemTable 3. Effects of water stress on grain yield of <strong>the</strong> wheat cultivarINIA66, Chiang Mai, Thailand, 1983-84TreatmentFull irrigationR/One irrigation omitted at:Crown root initiationTilleringBootAn<strong>the</strong>sisGrain fillingTwo irrigations omitted atan<strong>the</strong>sis and grain fillingThree irrigations omitted atboot, an<strong>the</strong>sis and grain fillingGrain yieldP(kg/ha)3226 a3329 a3301 a3041 ab2815 b3230 a2805 b2398c.,!/ Numbers followed by same letter not significantly different atP=0.5E./ Full irrigation consisted of six irrigations of approximately 50 mmeach at days from sowing -7 (pre-sowing), 9 (crown root initiation),28 (tillering), 48 (boot), 63 (an<strong>the</strong>sis) and 77 (grain filling)

270are where and how much will beplanted; how it will be used is a subjectto be covered by o<strong>the</strong>r delegates at thismeeting. The feasibility of <strong>the</strong> ricewheatsystem in nor<strong>the</strong>rn Thailand isclosely related to availability ofirrigation water and its seasonal andspatial distribution.Seasonal distributionof irrigation waterWith <strong>the</strong> rains ending in October. <strong>the</strong>level of water in <strong>the</strong> rivers and streamsthat is available for irrigation is stillquite high until early January. Anexample from Mae Taeng. <strong>the</strong> largestirrigation project in <strong>the</strong> Chiang MaiValley. is shown in Figure 3. Thisproject covers an area of 24.000 ha ofirrigated wetland rice. Currently. <strong>the</strong>reis enough water for only 10.000hectares of dry-season cropping. mainlysoybeans; <strong>the</strong> area planted to cropsafter rice under dry-season cropping islimited. mainly by <strong>the</strong> amount of wateravailable after <strong>the</strong> end of January. Witha system incorporating a shortergrowing season. such as rice-Wheat.this area could be greatly expanded.Spatial distributionof irrigation waterIrrigated rice agriculture in nor<strong>the</strong>rnThailand is characterized by itsVariability over relatively small areas.This is particularly true with respect to<strong>the</strong> aVailability of irrigation water in <strong>the</strong>dry season. For example. a close studyof a village south of Chiang Mai showedtha.t. in an area covering 130 hectaresof rice land. four distinct croppingsystems could be identified as a resultof four levels of water aVailability(Figure 4). This example comes from avillage with an extremely good. waterJan .Feb Mar Apr Mav Jun Jul Aug Sep Oct Nov DecMonthFigure 3. Water avallable at <strong>the</strong> wier. Mae Taeng Irrigation Project. ChiangMal. Thailand (average 1975 to 1982)Source: Royallrrlgatlon Department. Thailand

271_.z.:::-~:J.."•._,:.\--_.r+++v+\~+++++-1\+++++\f""'+ + + + + ...~++++ +-\l + ++ + +-t:~ +"oJ..-~-+ + +!.L+++'+'.!-f/+ c-, ,Rice-Soybean-RiceRice-Soybean-Rice(rice planted one month later than above)Rice-SoybeanRice-RiceHouses-•RiverIrrigation waterRoadUnderground wellFigure 4. Distribution of dee-based cropping systems as related to spatialvariation in availability of irrigation water, San Pong. Chiang Mal.ThailandSource: Anan Ganjanapan

272supply; in most cases. <strong>the</strong> range islikely to be at <strong>the</strong> scarce end of <strong>the</strong>scale. with underground water notalways available. The most commoncropping systems. <strong>the</strong>refore. would be adouble-crop system. with a shortage ofwater at <strong>the</strong> end of <strong>the</strong> season; thiswould mean that <strong>the</strong>re could be only asingle rice crop. A shorter durationcropping system. such as rice-wheat.should have a good chance of fitting inwhere available water is too limited forrice-soybeans. In certain areas. <strong>the</strong> ricewheatsystem might be limited by slowdrainage after <strong>the</strong> rice season.Fur<strong>the</strong>r projections for <strong>the</strong> Chiang MaiValley and <strong>the</strong> rest of nor<strong>the</strong>rnThailand will require more data. but<strong>the</strong> characteristics of <strong>the</strong> Mae Taengproject should apply. An improvementin water-use efficiency through <strong>the</strong>introduction of wheat. or any o<strong>the</strong>r cropwith similar adaptability. into <strong>the</strong> ricebasedcropping systems of nor<strong>the</strong>rnThailand seems highly promising.References1. Gypmantasiri. P.. A. Wiboonpongse.B. Rerkasem. I. Craig. K.Rerkasem. L. Ganjanapan. M.Titayawan. M. Seetisarn. P. Thani.R. Jaisaard. S. Ongprasert. T.Radanachaless and G. Conway.1980. An interdisciplinaryperspective of cropping systems in<strong>the</strong> Chiang Mai Valley: Keyquestions for research. MultipleCropping Project. Chiang MaiUniversity. Chiang Mai. Thailand.2. Julsrigaival. S.. and D. Tiyawalee.1982. A study of appropriateplanting date in wheat (in Thai). InProceedings of <strong>the</strong> Third NationalWinter Grain Workshop. Nor<strong>the</strong>rnAgricultural Development Centre.Bangkok. Thailand. Pp. 257-262.3. Rerkasem. B.. and P. Gypmantasiri.1981. Some aspects of keyprocesses in <strong>the</strong> nitrogen cycle ofrice-based multiple croppingsystems. In Nitrogen Cycling inSouth-East Monsoonal Ecosystems.R. Wetselaar. J.R. Simpson and T.RosswaiI. eds. Australian Acdemyof Science. Canberra. Australia. Pp.96-100.4. Rerkasem. B.• and K. Rerkasem.Utilization of indigenous geneticresources by farmers in nor<strong>the</strong>rnThailand. In Impact of Developmentof Human Activity Systems inSou<strong>the</strong>ast Asia. Sou<strong>the</strong>ast AsianUniversity Agroecology Networkand East-West Environment andPolicy Institute. (In press.)5. Rerkasem. K.. and B. Rerkasem.1984. Organic manure in intensivecropping systems. In OrganicMatter and Rice. IRRI. Los Baiios.Philippines. Pp. 517-531.

273Agronomic Practices and Problems forWheat Following Cotton and Rice in PakistanP.R. Hobbs, Wheat Program, CIMMYT, Islamabad, PakistanAbstractThree million hectares ofwheatfollow cotton or rice in Pakistan. To date, littleresearch has been done on <strong>the</strong> agronomyfor wheatfollowing <strong>the</strong>se two majorcash crops on a cropping-pattern basis. Both of <strong>the</strong>se crops delay wheat plantingsignificantly, and results suggest that, from 3 million hectares, 120,000 tons ofwheat are lost for every one-day delay in planting past November 10. Currentrecommendationsfor land preparation, fertilizer use, weed control and varietiesare based on wheatfollowing fallow. Scientists must begin working in teams,ra<strong>the</strong>r than according to commodities or disciplines, to develop more usefulrecommendationsfor cotton-wheat and rice-wheat cropping patterns.Cotton and rice in Pakistan are grownon 2.25 million and 1.8 millionhectares. respectively. in <strong>the</strong> kharif(summer) season. FollOWing harvest, itis estimated that 70% of <strong>the</strong> cotton and80% of <strong>the</strong> rice is followed by wheat.This is equivalent to 3 million hectaresof wheat or 30% of <strong>the</strong> wheat area inPakistan.Unfortunately. most of <strong>the</strong> agronomicresearch on wheat has been done withwheat as <strong>the</strong> sole crop (i.e.. followingfallow), and very little information isavailable on what happens to wheat in<strong>the</strong> double cropping patterns thatinclude cotton and rice. Thiscommentary will. <strong>the</strong>refore. identifyissues for research in <strong>the</strong>se importantcropping patterns ra<strong>the</strong>r than givespecific agronomic recommendations.Planting DateSeeding of wheat is delayed by bothcotton and rice harvest in Pakistan. Theexact timing in cotton-wheat areas isinfluenced by <strong>the</strong> cotton variety(maturity). farmer decision as towhe<strong>the</strong>r to have an extra cotton pickingand <strong>the</strong> ga<strong>the</strong>ring of <strong>the</strong> cotton sticks.which can be a valuable bonus for <strong>the</strong>farmers.In rice. variety is also an importantfactor in <strong>the</strong> delay of wheat planting.Only two rice varieties are cOJ.l1monlygrown in Pakistan. mainly because 40to 50% of <strong>the</strong> rice is exported; <strong>the</strong>refore,<strong>the</strong> government restricts <strong>the</strong>release of varieties. The two varietiesare IR6. a high-yielding. nonphotosensitivetype. and Basmati. atraditional, high-quality photosensitivetype. With IR6. fields are harvested bylate October to mid-November. andwheat can be planted in November;with Basmati. harvest is often delayedto <strong>the</strong> end of November or even intoDecember. In addition. farmers cut. dryand thresh <strong>the</strong> rice in <strong>the</strong> same fieldsbefore turning to land preparation forwheat. This extra 10 to 20-day delayoften pushes wheat planting into lateDecember or even January.Figure 1 shows <strong>the</strong> effect of wheatplanting date on <strong>the</strong> yield of threewheat varieties. The optimal date forwheat planting is November 10 and. onaverage. 40 kg/ha (120.000 tons for 3million hectares) of grain is lost forevery one-day delay in planting afterthis date. Earlier plantings have loweryields because of frost damage duringflowering. ObViously. delayed plantingbecause of cotton and rice substantiallyreduces yield potential. especially withwheat planted after Basmati rice. Thissituation can be improved by usingearlier-maturing cotton and ricevarieties. speeding up turn-around timeand using wheat varieties that yieldbetter when planted late.

274Interestingly. Blue Silver (or Sonalikal.which is considered as short-maturingand is recommended for Decemberplanting. does not do as well asPakistan 81 (Veery 5) or Punjab 81when planted late. Although its yielddeclines less with late planting. itspotential yield is much lower than thatof <strong>the</strong> o<strong>the</strong>r two varieties; this reducesits yield to below that of Punjab 81 andPakistan 81. even in late-planted fields.More screening is needed of wheatgermplasm to follow rice or cotton withlate planting. especially to identifyvarieties like Punjab 81 for <strong>the</strong>sesituations.Land and Seedbed PreparationIn cotton-wheat areas. seedbedpreparation is relatively easy. follOWing<strong>the</strong> removal of <strong>the</strong> cotton sticks; <strong>the</strong> soilis relatively friable and can be preparedfor wheat qUickly. Because of <strong>the</strong> use ofshallow-tillage implements over manycenturies in Pakistan. <strong>the</strong>re might besome benefits from deep tillage in <strong>the</strong>seareas; some experiments should beinitiated to test this hypo<strong>the</strong>sis.In <strong>the</strong> rice areas. <strong>the</strong> situation isdifferent. About one-half of <strong>the</strong> rice inPakistan is grown on puddled clay andclay-loam soils. Therefore. <strong>the</strong> farmer isfaced with a hard. structureless mass ofsoil to be prepared for wheat. This takestime and. where soils are heavy intexture. final seedbed preparation maybe very poor. Luckily. <strong>the</strong> o<strong>the</strong>r half of<strong>the</strong> rice soils in Pakistan are mediumtextured.Associated with <strong>the</strong>se unfavorable soilsfor wheat are <strong>the</strong> plow paris. developedby puddling and needed to restrict5000---Pak 81 Y = 4445 - 43.7 x------ Blue Silver Y = 3789 - 36.6 x.............. Punjab 81 Y = 4603 - 39.5 xAverage Y = 4206 - 39.7 x" ' .... ........ ...........-- ........ -.........-""" " ' -.........-4000C?.c]0 - 't:l 3000'ii>=...............'......'.'.'.'. '.'.....0....." .'..". '..... ...... .2000Oct 31 Nov 10 Nov 20 Nov 30 Dec 10 Dec 20 Dec 30 Jan 10Seeding datesFigure 1. Effect of planting date on yield of late (Pakistan 81). medium(Punjab 81) and early (Blue Silver) wheat varieties. PakistanSource: AARI. Faisalabad. Pakistan. 1982 to 1984

275water percolation in rice. For wheat.<strong>the</strong>se pans may limit rooting andsubsequent moisture and nutrientaVailability. They also increasewaterlogging in wheat and increase <strong>the</strong>problem of seedbed preparation. If <strong>the</strong>plow pan is broken. wheat yields mayincrease. but more water will be neededfor rice and <strong>the</strong> soils may not be able tophysically support <strong>the</strong> animals ortillage implements needed to puddle <strong>the</strong>soil for rice. As with cotton. <strong>the</strong>re is also<strong>the</strong> problem of crop residues facing <strong>the</strong>farmer when he prepares <strong>the</strong> land forwheat.Little information is available on <strong>the</strong>seissues. More studies are needed toidentify <strong>the</strong> best implements for landpreparation. They must be evaluated asto cost. time needed and ability tohandle residues. It would also beinteresting to study <strong>the</strong> effect of deeptillage on total annual productivity.Seeding Rates and MethodsMost farmers broadcast wheat.following cotton and rice. at <strong>the</strong> rate of100 kg of seed per hectare. Morestudies are needed on using higher seedrates and comparing broadcastingversus machine drilling when wheat isplanted late. Poor plant stands arecommon in <strong>the</strong> rice-wheat areas. largelybecause of poor land preparation; ahigher seed'rate may compensate forthis problem. Studies should also beinitiated on no-till planting of wheatinto rice as a means to reduce turnaroundtime.Fertilizer UseAs with <strong>the</strong> previous agronomicpractices. fertilizer studies in Pakistanhave been on wheat following fallow.but rarely following cotton or rice.Response surfaces for nitrogen andphosphorus must be determined forcotton-wheat and rice-wheat croppingpatterns for different soils over time.There are also reports of response topotash and micronutrients in wheatfollowing rice. but more studies areneeded in this area on a croppingpatternbasis.Weed ControlWeeds are greatly influenced by <strong>the</strong>previous crop and <strong>the</strong> cropping pattern.Common weeds in <strong>the</strong> cotton-wheatpattern include Chenopodium album.Chenopodium murale and Convolvulusarvensis. In rice-wheat. Phalaris minorand Avenafatua. along withChenopodium album. are <strong>the</strong> majorweeds causing economic losses inwheat.Herbicides could be used to control<strong>the</strong>se weeds. Any of <strong>the</strong> phenoxyaceticacid family will control <strong>the</strong> broadleafweeds. although Convolvulus arvensiswould regrow after a time; <strong>the</strong> use ofDicamba + MCPP (Banvil-P) does abetter job on this weed. The substitutedureas, Tribunil. Dicuran. Dosanex orIsoproturon can be used for <strong>the</strong>Phalaris or Avena. although Suffix.Mataven or Difenzoquat may be betterfor Avena. These grassy-weedherbicides are more costly than <strong>the</strong>broadleaf herbicides.In Pakistan. herbicide use is in itsinfancy and few scientists. much lessfarmers. have expertise in applying<strong>the</strong>m properly. O<strong>the</strong>r methods areneeded. Many farmers rotate land whenweeds become a problem. Berseem(Trifolium alexandrinum) is used inplace of wheat as a winter fodder whenweeds are a problem; however. this isnot a viable option except in areaswhere berseem is a cash crop. Twothirdsof <strong>the</strong> farmers' fields in a recentstudy had been planted to wheatcontinuously for three or more years.

276Pre-irrigation is ano<strong>the</strong>r way ofreducing weed populations; <strong>the</strong> weedsare plowed under just before planting.The major problem here is <strong>the</strong> delay inplanting associated with irrigation. andso this is obviously not a solution withBasmati rice. Many farmers irrigate<strong>the</strong>ir rice fields before harvest togerminate weeds and not delay landpreparation for wheat. The major wheatvariety in <strong>the</strong> Punjab is Yecora, a tripledwarf. which accentuates <strong>the</strong> problemcaused by weeds. especially Phalarisand Avena. More research is needed onquantifying losses caused by weeds andeconomically evaluating alternativestrategies.A team approach is needed to bring <strong>the</strong>present commodity and disciplineorientedscientists toge<strong>the</strong>r to work onproblems on a cropping-pattern basis.At present. Pakistani sc;ientists tend towork in isolation and do not look at <strong>the</strong>problems and issues associated withwheat grown in a multiple croppingpattern.

277Rice-Wheat Cropping Systemsin South and Sou<strong>the</strong>ast AsiaV.R. Carangal, International Rice Research Institute, Manila,PhilippinesAbstractRice-wheat rotation is practiced in South Asia in India, Pakistan, Nepal, Bhutan,Bangladesh, Burma and China. In Sou<strong>the</strong>ast Asia, wheat is not yet acommercial crop, but national programs are intensifying <strong>the</strong>ir research becauseof increasing demand and heavy importation. IRRI and CIMMYT arecollaborating with 13 countries involved in <strong>the</strong> Asian Rice Farming SystemsNetwork to identify suitable varietal combinationsfor rice-wheat croppingsystems and to evaluate performance of rice-wheat systems in different riceenvironments in Asia. In South Asia, rice-wheat is <strong>the</strong> most predominantcropping pattern; in some countries, it is rice-wheat-upland crop. Most croppingpatternevaluations indicate that three-crop systems give higher production andnet returns than do two crops. The Philippines, Indonesia, Thailand. Burma andSri Lanka are especially interested in increasing wheat production. Varietytrials in nor<strong>the</strong>rn Thailand and high elevation areas have given yields of up to3.5 t/ha. Thefirst International Rice-Wheat Integrated Trials in <strong>the</strong> Philippines,Burma and Thailand showed low yield levels; agronomic management studiesat IRRI reported only up to 2.5 t/ha. There is a need to develop better varietiesfor <strong>the</strong> tropics and better agronomic management in ricefields.Rice and wheat are <strong>the</strong> most importantcereal crops in <strong>the</strong> world. About 90% of<strong>the</strong> world's rice is grown in Asia, withIndia and China accounting for about60%. Rice is grown in temperate,subtropical and tropical countries,under both rainfed conditions (upland,lowland and deepwater) and irrigation(including partial irrigation). Wheat ismainly cultivated in <strong>the</strong> subtropical aridtemperate countries in Asia, usuallywith irrigation under lowlandconditions. In some rainfed lowland anddeepwater areas, wheat is also grown,especially in areas with good moisturelasting into <strong>the</strong> dry season.Rice-wheat rotation is practiced intemperate and subtropical Asia. In <strong>the</strong>last 15 years, <strong>the</strong> rice-wheat rotationhas rapidly expanded to nontraditionalrice-wheat areas, mainly due to <strong>the</strong>development of photo-insensitive, earlymaturing,nonlodging. high-yielding,disease and pest-reSistant varieties ofrice and wheat, but also to <strong>the</strong>development of better agronomicpractices and <strong>the</strong> expanSion ofirrigation. In irrigated areas, rice-wheat,rice-rice-wheat, rice-wheat-upland cropand rice-upland crop-wheat are <strong>the</strong>common cropping patterns. Rice-wheatrotations are mainly practiced in Indiaand Pakistan, and have recentlybecome important rotations in Nepal.Bhutan and Bangladesh.In tropical countries where wheat is nota commercial crop, attention is nowbeing given by national programs to <strong>the</strong>production of wheat because of heavyimportation for local consumption.Research is now in progress in <strong>the</strong>Philippines, Indonesia, Thailand,Burma and Sri Lanka to developappropriate wheat productiontechnology. With <strong>the</strong> development ofearly-matUring rice varieties (100 to120 days), wheat can now be grownunder irrigation and partial irrigationon light to medium-textured soilsdUring <strong>the</strong> dry season, usually <strong>the</strong>cooler months of <strong>the</strong> year. It can also be

278grown in rainfed upland or lowland riceareas where <strong>the</strong>re is enough rainfallduring <strong>the</strong> cooler season.Rice-Wheat Cropping SystemsMajor collaborative research in <strong>the</strong>Asian Rice Farming Systems Networkis in rice-wheat cropping; IRRI andCIMMYT are collaborating with 13countries in Asia. Nepal. Bangladesh.Thailand. Philippines. Sri Lanka.Bhutan. Pakistan. Malaysia. Indonesia.China. Taiwan. Burma and Korea. Theobjectives of <strong>the</strong> collaboration are to:• Identify rice-wheat cropping systemstechnology that is suitable for smallscalefarmers;• Identify better combinations of riceand wheat varieties;• Encourage rice and wheat scientiststo work toge<strong>the</strong>r and identifycomponent technologies that willincrease <strong>the</strong> production of rice-wheatsystems, and• Promote collaborative research in <strong>the</strong>network on o<strong>the</strong>r problems commonto <strong>the</strong> region.The fIrst two projects in thiscollaboration are cropping-patterntesting in six countries. Nepal. China.Taiwan. Bangladesh. Korea and SriLanka. and <strong>the</strong> International RiceWheat Integrated Trials (lRWIT) in all13 countries.Cropping-pattern trials are conductedon farmers' fields to compare rice-wheatsystems with o<strong>the</strong>r cropping systems.IRWIT. on <strong>the</strong> o<strong>the</strong>r hand, is a varietalevaluation trial of rice (from IRRI) andwheat (from CIMMYT) at <strong>the</strong> time <strong>the</strong>crop is grown within <strong>the</strong> system. IRRIproVides six varieties of rice, and <strong>the</strong>national programs are requested toinclude six varieties from <strong>the</strong>ir breedingprograms. For <strong>the</strong> wheat trials. CIMMYTprOVides fIve entries and nationalprograms five entries. There are two setsof trials for each crop for rice. a set ofearly-maturing rice for temperate andsubtropical countries and a set of earlyand medium-maturing rice varieties fortropical countries. For wheat. <strong>the</strong>re is aset of early-maturing wheat varieties foroptimum planting time (November 15 ±10 days) and a set of early-maturingvarieties for late planting(December 15 ±. 10 days).Rice-Wheat in South AsiaNepalRice-wheat rotation takes place onapprOXimately 480,000 hectares. and<strong>the</strong>re is potential for doubling <strong>the</strong> area.especially in <strong>the</strong> Tarai. Wheat is rotatedwith rice in both irrigated and rainfedareas. In <strong>the</strong> hills. rice-wheat and ricewheat-comare <strong>the</strong> common croppingpatterns while, in <strong>the</strong> Tarai rice-wheatand rice-rice-wheat are common. Insome areas. mixed cropping of wheatand mustard after rice is practiced.There are seven cropping systems sitesin Nepal. Of <strong>the</strong>se. three are involved in<strong>the</strong> network collaboration on croppingpatterntesting. Pumdi Bhumdi in <strong>the</strong>hills. Ratna Nagar in <strong>the</strong> inner Taraiand Bhairawa Tubewel) in <strong>the</strong> Tarai. InRatna Nagar. several cropping patternshave been tested on both irrigated andrainfed lowlands. Rice-wheat-mungbeanand rice-wheat-maize have given higherproduction and net returns ascompared to <strong>the</strong> farmers' practice ofrice-wheat (Table 1). The wheatvarieties Lumbini and UP262 haveyielded 65 to 91% more than <strong>the</strong>farmers' RR21; rice yield from varietiesLaxmi and Malaka Janaki was up to63% higher than <strong>the</strong> farmers' Masulivariety. On rainfed lowlands. ricemaize.with improved management.and rice-wheat patterns showed higherproduction and net returns ascompared with <strong>the</strong> local farmers' ricemaizepractice.In <strong>the</strong> Bhairawa Tubewell. 17 croppingpatterns were tested. Rice-maize-maizeshowed higher production and netreturns than did rice-wheat-rice(Table 2). The farmers' practice of ricerice-wheatis comparable to <strong>the</strong>

279Table 1. Yield and economic returns of different cropping patterns tested at RatnaNagar, Nepal, 1982-83Yield (t/he)Net returnsCropping pettern Crop 1 Crop 2 Crop 3 (USS/hel.ll'Irrigated, lowland(F) Rice (Masulil-wheat (RR21)-fallow 3.18 2.10 232(FAI Rice (Laxmil-wheat (Lumbini)-mungbean(Pusa Baisakhil 5.19 4.01 0.54 860Rice (Bindeshwari-wheat (Lumbini-maize (Arun) 4.27 3.80 2.48 951Rice (Malika)-mustard (Iocal)-maize(Rampur Comp) 3.78.21 0.53 3.64 580Rice (Janaki-wheat (UP262)-dhaincha (local) 4.25 3.48 GM.QI 562Rice (Janaki)-wheat (UP262)-fallow 3.19 3.48 523Rainfed, lowland(F) Rice (Masuli-fallow-maize (Rampur Comp) 2.82 2.40 306(FA) Rice (Masuli)-fallow-maize (Rampur Comp) 3.25.21 4.15 503Rice (Janak i)-mustard (Iocal)-fallow 4.93 0.52 354Rice (Janak i)-wheat (UP262)-fallow 4.25 2.28 400Rice (Masulj)/lentil-fallow 2.85.21 -.21Rice (Masuli)-fallow-dhaincha (local) 2.72 GM£! (-16)Rice (Masulj)-fallow-fallow 2.93 87F = farmers' cropping pattern, FA =alternative cropping patterns.P US$ 1 = 16.30 Rs.21 Most plants suffered from severe lodging.QI Green manure crop (plowed under)Source: Cropping systems staff, 1984Table 2. Yield and economic returns of different cropping patterns tested at BhairawaTubewell, Nepal, 1982-83Cropping petternYield (t/ha) Net returnsCrop 1 Crop 2 Crop 3 (US$/he).lI'(F)(FA)Rice (Masulj}-wheat (jmproved)-rice (local and improved)Rice (Janaki)-mustard (Iocal)-maize (Rampur Camp)Rice (Laxmi)-maize (Rampur VI-maize (Arun)Rice (Bindeshwari)-maize (Rampur Y)-mungbean (PS·7)Rice (Malika)-wheat (UP262)-mungbean (PS·7)Rice (Janaki)-wheat (Lumbini)-dhaincha (local)Rice (Janaki)-wheat (Lumbini)-fallowRice (Masuli)-wheat (Lumbinj}-rice (Malika)1.79 3.04 4.20 10794.78 0.82 3.07 10304.79 6.41 2.31 14194.10 4.35 0.95 10093.55 3.15 0.89 8794.93 3.22 GM.21 9714.08 3.22 8941.76 2.94 4.86 1096F = farmers' cropping pattern, FA = alternative cropping pattern,!I US$ 1 = 16.30 RsIII Green manure crop (plowed under)Source: Cropping systems staff, 1984

280improved rice-rice-wheat because. in<strong>the</strong> past three years. <strong>the</strong> use ofimproved varieties and betteragronomic practices has steadilyincreased. The o<strong>the</strong>r improved patternshave lower production and net returns.There are two land categories in PumdiBhumdi. The rainfed lowlands have ahigh production potential where <strong>the</strong>cropping pattern is rice-wheat-maize.and a medium production potentialwhere <strong>the</strong> cropping pattern is ricemaize.Several years of testing haveresulted in <strong>the</strong> identification of a varietyof rice adapted to <strong>the</strong> hills. K39 is anearly-maturing variety with satisfactorygrain type. high grain yield. acceptablestraw characteristics; it is less damagedby hail. It fits into both <strong>the</strong> areas ofhigh and medium production-potential.Its yield ranges from 4.0 to 4.4 tlha in<strong>the</strong> rice-wheat-maize pattern and from3.6 to 4.4 tlha in <strong>the</strong> rice-wheat patternin <strong>the</strong> areas of high productionpotential. The maize variety Arun hasnow been adopted by farmers in bothhigh and medium production potentialareas. with yields up to 3.57 tlha. Yieldlevels of wheat (RR21) are low (1.9 t1ha)in both patterns. Hence. better varietiesof wheat are needed to fur<strong>the</strong>r increaseproduction and income.The rice-wheat-maize pattern undergood agronomic management wastested in 1982-83 in <strong>the</strong> highproduction potential areas. The annualproduction was 12.8% higher than <strong>the</strong>farmers' rice-wheat-maize pattern. but<strong>the</strong> net returns did not differ. Theresults of several tests led to farmeradoption of improved agronomicpractices and high-yielding varieties. In<strong>the</strong> medium production potential areas.four cropping patterns were tested. ricewheat.rice-maize. rice-broad beansmaizeand rice-oats. The highest netreturn was obtained from <strong>the</strong> rice-maizepattern (US$ 899); it was 25% higherthan <strong>the</strong> rice-wheat pattern.BangladeshWheat is a nontraditional crop inBangladesh. In <strong>the</strong> 1970s. a ten-foldincrease in wheat production wasachieved. It increased from a total of89.000 tons in 1973 to 1.1 million tonsin 1981. ApproXimately 500.000hectares are now under rice-wheatcropping systems. There is <strong>the</strong> potentialto expand to about 2 million hectares. ifbetter varieties are identified andirrigation prOVided. Wheat is generallygrown after transplanted Aman rice inrainfed and irrigated rice areas. Themost common cropping patternsinvolving wheat are rice-wheat and ricerice-wheat.On-farm cropping systems research inBangladesh is conducted on 16 sites byseven institutions under <strong>the</strong>coordination of <strong>the</strong> BangladeshAgricultural Research Council. Inseveral sites. <strong>the</strong> rice-wheat system isone of <strong>the</strong> patterns being studied. As inNepal. <strong>the</strong> farmers' existing croppingpattern is compared with alternative orimproved cropping patterns. ResultsinvolVing wheat from three sites arepresented in Table 3.The farmers in Hathanzari traditionallygrow only two rice crops. and leave <strong>the</strong>field fallow for 180 days after harvest.The team has introduced wheat as athird crop. coupled with an improvedvariety of rice. The total yield of <strong>the</strong> tworice crops under improved managementwas 7.5 tlha. 32% better than <strong>the</strong>farmers' practice (6). The net returns ofrice-rice-wheat was 59% better than <strong>the</strong>farmers' rice-rice cropping pattern(Table 3).In <strong>the</strong> rainfed areas of Trishal Thana.<strong>the</strong> Bangladesh Agricultural Universitytested rice-rice-wheat and jute-ricewheat.The predominant or existingcropping patterns are rice-rice and juterice.using local varieties; wheat wasintroduced as a new crop. The yields ofimproved rice and jute were muchhigher than <strong>the</strong> local varieties. and <strong>the</strong>wheat crop was excellent. Net return

281was higher with <strong>the</strong> introduction ofwheat in both <strong>the</strong> rice-rice pattern(318-510% better) and in jute-rice(383% better).The predominant cropping pattern inThakurgaen is local rice-wheat. In someareas, rice-rice-wheat is grown. TheWater Development Board tested severalcropping patterns, using improvedvarieties and medium levels of fertilizerin <strong>the</strong> Aman season. The yields and netreturns of alternative cropping patternswere higher than <strong>the</strong> farmers' rice-ricewheatrotation (Table 3). Inclusion ofmungbean and millet proved to be goodalternatives in imprOVing <strong>the</strong> existingsystem; <strong>the</strong> highest net returns wereobserved in <strong>the</strong> rice-wheat pattern. Theuse of Jupateco, Balaka and, especially,Pavon increased production and netreturns.IndiaUnder irrigated conditions, <strong>the</strong> ricewheatcropping system is an importantpractice in <strong>the</strong> states of Punjab,Haryana, Uttar Pradesh. Bihar. WestBengal. Orissa. parts of Madhya Pradeshand Rajasthan. The area has expandedin <strong>the</strong> last 20 years with <strong>the</strong>development of photo-insensitive. highyieldingand early-maturing varieties ofboth rice and wheat and <strong>the</strong>development of irrigation systems.Recently. <strong>the</strong> area has also expanded torainfed rice areas. especially when <strong>the</strong>reis available moisture. The three-cropsystems are becoming popular inirrigated areas in nor<strong>the</strong>astern India.Cropping patterns such as rice-wheat·rice and rice-wheat-mungbean are fastbecoming popular among farmers.Table 3. Yield and economic returns of cropping patterns tested at three sites in Bangladesh,1982-83Yield (t/ha) Net returnsLocation and cropping pattern Crop 1 Crop 2 Crop 3 (US$/ha).!1Hathazari (partially irrigated, highland)(F) Rice (Purbachj)-rice (Nizershail) 3.16 2.46 552(FA) Rice (Purbachj)-rice (BRll)-wheat (Sonalika) 3.70 3.75 1.62 879Trishal Thana (rainfed, lowland)(F) Rice (Aus L)-rice (T. amon L)-fallow 1.31 1.87 273(FA) Rice (BR10)-rice (BR11)-wheat (INIA66) 3.86 4.84 3.57 1142(FA) Rice (B R10) -rice (B R11) -wheat (I NIA66) 4.91 5.40 4.17 1665(F) Jute (L)-rice (T. amon L)-fallow 1.34 1.87 243(FA) Jute (I)-rice (T. amon HYV)-wheat 2.43 5.38 3.99 975Thakurgaon (irrigated, highland)(F) Rice (Sanj)-rice (Kalam)-wheat (Sonalika) 1.91 1.57 1.30 576(FA) Rice (Dharial)-rice (BR 11 )-wheat (Jupateco) 1.68 4.19 2.33 1181(FA) Mungbean-rice (BR10)-wheat (Balaka) 0.70 3.73 2.65 1066(FA) Millet-rice (Pajam)-wheat (Pavon) 1.12 4.13 3.43 1171(FA) Fallow-rice (BR4)-wheat (Pavon) 4.53 3.73 1200F = farmers' cropping pattern, FA = alternative cropping pattern.!/ US$ 1 = 25 TKSource: Rahman and Manzano (6)

282Data on <strong>the</strong> production potential of threecropsystems involving wheat, reportedfrom various centers of <strong>the</strong> All-IndiaCoordinated Agronomic ResearchProjects (AICARP), showed high totalproduction and net incomes (5). Themost promising sequence with rice andwheat in each state is shown in Table 4.At Kalyani, <strong>the</strong> rice-wheat-maize patterngave a total yield of 10.3 tlha, with a netincome ofUSS 812. Rice-wheat-cowpea +maize in Pantnagar showed a net incomeof USS 959. Highest yield and net incomewere reported on rice-potato + wheat +wheat-mungbean (USS 1,861) fromFaizabad in Uttar Pradesh. Rice-wheatmungbeanwas <strong>the</strong> best at KaIjat in <strong>the</strong>Konkan region. Most of <strong>the</strong> latest dataindicate that <strong>the</strong> rice-wheat-pulse(mungbean) crop pattern appears to be<strong>the</strong> most promising in terms ofproduction, income and nutrition. Riceand wheat provide carbohydrates andpulses provide protein.Sri LankaWheat is not grown commercially in SriLanka. However, <strong>the</strong>re is potential togrow wheat after rice, especially in <strong>the</strong>high-elevation areas. In 1980, <strong>the</strong>Director of Agriculture introducedwheat (Trigo 1 from <strong>the</strong> Philippines) inBandarawela. Performance was verypromising.The cropping-systems team inBandarawela tested wheat in a threecropsystem. The dominant croppingpatterns in lowland rice areas were ricepotatoand rice-vegetables. The researchteam was able to identify an earlymaturingvariety of rice which has nowbeen adopted by farmers; with this newvariety, <strong>the</strong> three-crop system has beenstabilized. In <strong>the</strong>ir multilocation testing,wheat is one of <strong>the</strong> crops in <strong>the</strong> patterns.The fIrst crop is rice in February,followed in June by potato, beans,cabbage, carrots, garlic or tomato; <strong>the</strong>third crop in November is wheat.soybeans, carrots or radish. Wheat hasTable 4. Yield and economic returns of three crop patterns involving rice and Wheat, India,1979·80 to 1981-82Yield h/ha)Net returnsLocation and cropping pattern Crop 1 Crop 2 Crop 3 (US$/ha),§Pantnagar(F) Rice-wheat-eowpea +ma ize 3.82 4.29 29.30 959KalyaniRice-wheat-maize 4.07 3.48 2.75 812FaizabadRice-potato =i-wheat-green gram 4.39 12.73 0.63 1861VaranasiRice-wheat-green gram 4.75 3,43 1.06 937KarjatRice~wheat-green gram 3.42 2.01 0.54 553F = farmers' cropping pattern~/ US$ 1 = 11.30 Indian rupeesSource: Pillai (5)

283to compete with o<strong>the</strong>r high-incomecrops. and present yield levels are quitelow.In a yield trial of five wheat varieties(Sonalika. INIA66. 213. Zambezi andTrigo 1) in Bandarawela during <strong>the</strong>1982-83 Maha season. <strong>the</strong> highest yieldwas from Trigo 1. and that was only1.07 tfha (4). Better varieties of wheatare needed in order to compete witho<strong>the</strong>r crops that can be grown during<strong>the</strong> season.PakistanThe common cropping patterns in <strong>the</strong>Punjab are rice-wheat and rice-cloverand. in Sind. rice-wheat and rice-peas;approximately 700.000 hectares in <strong>the</strong>two provinces are grown to rice-wheat.The most popular variety of rice is IR6which matures in 135 to 140 days. andso fits into <strong>the</strong> rice-wheat system verywell. It is transplanted in June andharvested in October. IR6 is grown on77% of <strong>the</strong> rice area in Sind and 24% of<strong>the</strong> area in <strong>the</strong> Punjab. The o<strong>the</strong>rpopular variety of rice is Basmati(scented rice). which is generallytransplanted in July and harvested inDecember. Wheat planted after Basmatihas lower yields than wheat plantedafter IR6. However. farmers plantBasmati because of its high price (twice<strong>the</strong> price of IR6). About 80% of <strong>the</strong> ricefarmers planted Basmati in <strong>the</strong> Punjabin 1983 and 24% in Sind. KS282, a newvariety. was recently released in <strong>the</strong>Punjab. It is high yielding, earlymaturing and has resistance to bacterialleaf blight; it can be planted in June andharvested in mid-September. With <strong>the</strong>early harvest. new cropping patternswere tested in Kala Shah Kaku.including rice-wheat. rice-clover. ricemustard-mungbeanand rice-mustardsunflower(3). Yield of rice in <strong>the</strong> trialwas 3.7 tlha; wheat yielded 3.2 tlha.Total net return of rice-clover was 29%better than <strong>the</strong> rice-wheat rotation. ricemustard-mungbeanwas 33% better andrice-mustard-sunflower. 19% better(Table 5). These are alternative croppingpatterns that can be used instead of ricewheatin some areas.Wheat is grown under both irrigated andnon-irrigated conditions in Sind. Wheatyields under irrigation are generallyhigher than those Without irrigation. In<strong>the</strong> last few years. chickpea is beingreplaced by wheat. because of <strong>the</strong>adoption of IR6 which matures laterthan local varieties. Chickpea is plantedlater and its yield is lower. Severalcropping patterns were tested at <strong>the</strong>Dokri Rice Research Institute (1). with<strong>the</strong> winter crops not irrigated and notfertilized. Wheat yield was only 0.95Table 5. Yield and economic returns of four cropping patterns tested at <strong>the</strong> Rice ResearchInstitute, Kala Shan Kaku, Punjab, PakistanYield (t/ha)Net returnsCropping pattern Crop 1 Crop 2 Crop 3 (US$/ha)Rice-wheat 3.7 3.2 345Rice-elover 3.7 82.1 444Rice-mustard-mungbean 3.7 1.1 0.6 459Rice-mustard-sunflower 3.7 1.1 1.0 409Source: Majid Chaudhary (3)

284Uha. Highest net income was obtained in<strong>the</strong> rice-chickpea rotation (usa 893).22% better than rice-wheat (Table 6).Rice-Wheat in Sou<strong>the</strong>ast AsiaWheat is not commercially grown inmost Sou<strong>the</strong>ast Asian countries. exceptin Burma. However. <strong>the</strong> consumption ofwheat in <strong>the</strong>se countries is increasing ata rapid rate. The Philippines. forexample. imported about 1.2 milliontons in 1983; likewise. Indonesia. SriLanka and Thailand are heavy importersof wheat. There is now great interest ingrOwing wheat because of this increasein demand and imports. Research is inprogress in Thailand. Philippines.Indonesia. Burma and Sri Lanka. Thereis potential to grow wheat. especiallyafter rice. in areas with irrigation andUght-to-medium textured soils. Rice isgenerally planted in June or July.during <strong>the</strong> rainy season. and wheat inNovember or December. during <strong>the</strong> dryseason when <strong>the</strong>re are coolertemperatures. In high elevation areas in<strong>the</strong> tropics. wheat can be grown afterrice. Nor<strong>the</strong>rn Thailand and Burma cangrow wheat after rice on a commercialscale.There have stlll not been rice-wheatcropping-pattern trials in Sou<strong>the</strong>astAsia: most of <strong>the</strong> work is on varietalevaluation and agronomic management.Variety trials of wheat in nor<strong>the</strong>rnThailand and high elevation areas inIndonesia (Margahayu) have shownyields of up to 3.5 Uha. However. inmost trials. yields are generally low andunstable. There are years when yieldsare high. and years when <strong>the</strong>y are low.The First International Rice-WheatIntegrated Trial. which started in <strong>the</strong>Philippines. Burma and Thailand in late1982. gave very low yield levels. Thehighest wheat yields at IRRI.Philippines. came from Trigo 1 (localcheck) with 1.55 Uha: at Yezin. Burma.Abasolo 81 yielded 1.81 Uha. At Dagan.Philippines. Ures 81 had a yield of 0.43Uha and. in nor<strong>the</strong>rn Thailand.CIAN079 yielded 0.94 Uha. Yield levelsin 1983 were far better. At IRRI.Philippines. wheat yields ranged from0.58 to 1.96 Uha. The highest yield wasfrom C214-1. a variety developed by <strong>the</strong>Institute of Plant Breeding at <strong>the</strong>University of <strong>the</strong> Philippines in LosBailos.Agronomic management studies at IRRIshow low yield levels for wheat:however. <strong>the</strong>y can be considered highTable 6. Yield and net returns of various cropping patterns tested at <strong>the</strong> Rice ResearchInstitute, Dokri, PakistanCropping patternYield It/ha)Crop 1 Crop 2Net returns(US$/ha)Rice-wheatRice-barleyRice-ehickpeaRice-lentilRice-ehickling vetchRice-mustardRice-safflowerRice-IinseedRice4.584.335.084.914.994.164.414.385.240.954.260.660.620.580.290.676.76618610893756647500644626555Source: Bhatti (1)

for tropical environments. Highestaverage yields in some experimentswere only about 2.5 t/ha. Planting dateand fertilizer-level experiments withwheat after lowland rice was conductedby <strong>the</strong> IRRI Multiple CroppingDepartment in Cagayan and at <strong>the</strong> IRRIFarm at Los Baflos. Among fourvarieties (UPLWI. C220-5. C169-6 andINIA66) used in different planting-dateexperiments in Cagayan. C 169-6showed <strong>the</strong> highest average yield (2.0t/ha). Five planting-date trials wereconducted at IRRI. using five varieties.UPLWI. INIA66. C220-5. ANZA andC169-6. There <strong>the</strong> highest average yieldwas from C220-5 (2.5 t/ha) followed byC169-6 (2.4 tlha). In <strong>the</strong> fertilizerexperiment at Cagayan. 2.58 t/ha wasobtained with a nitrogen application of120 kglha on <strong>the</strong> variety UPLW 1(Trigo 1).Better varieties and managementtechniques are needed for wheat tocompete with o<strong>the</strong>r crops that can begrown after rice. Hopefully. thissymposium will help us arrive at bettertechnologies for Sou<strong>the</strong>ast Asia.References3. Majid Chaudhary. A. Croppingpattern testing. Punjab. Pakistan.1983. International Rice ResearchConference. IRRI. Los Baflos.Philippines. (Unpublished.)4. Sikurajapathy. M. Croppingsystems program. Sri Lanka.Report of <strong>the</strong> Fifteenth Asian RiceFarming Systems Working GroupMeeting. Rice Farming SystemsProgram. IRRI. Los Baflos.Philippines. (In press.)5. Pillai. K. Gopalakrishna. 1983.Cropping systems research in Indiarice-based cropping systems. InReport of <strong>the</strong> Fourteenth CroppingSystems Working Group Meeting.Rice Farming Systems Program.IRRI. Los Baflos. Philippines. Pp.384-407.6. Rahman. M.M.• and A.H. Manzano.Cropping pattern testing inBangladesh. Report of <strong>the</strong> FifteenthAsian Rice Farming SystemsWorking Group Meeting. RiceFarming Systems Program. IRRI.Los Baflos. Philippines. (In press.)1. Bhatti. I.M. Cropping patterntesting. Sind. Pakistan. 1983.International Rice ResearchConference. IRRI. Los Baflos.Philippines. (Unpublished.)2. Cropping Systems Staff. Progressreport on cropping pattern testingin Nepal for 1983. Report of <strong>the</strong>Fifteenth Asian Rice FarmingSystems Working Group Meeting.Rice Farming Systems Program.IRRI. Los Baflos. Philippines. (Inpress.)

286Simple Simulation Modelsfor Agronomic ResearchW.A.J. de Milliano, Wheat Program, CIMMYT, Mezico, and H. vanKewen, Centre for World Food Studies, Wageningen, Ne<strong>the</strong>rlandsAbstractAn increasing number ofcountrtes in <strong>the</strong> tropical belt have reacted to increasedwheat consumption by establishing local wheat research and productionprograms. By means ofsimple simulation models based on climatic variables.potential wheat yields (root. shoot and grain yields) can be calculatedfortropical environments. These models may be helpfuLfor extrapolation ofresultsto o<strong>the</strong>r geographical areas. where less detailed or no expertmention has beencarried out. orfor generalization over longer time pertods. Such models can helpidentify suitable areasfor wheat research. and determine optimum sowingdates. days to reach spec#fl.c developmental stages and datesfor supplementaryirrtgation. They may also help assess whe<strong>the</strong>r long or short-maturation cultivarsshould be used in a spec#fl.c area.Wheat has one of its centers of origin in<strong>the</strong> tropical belt in Ethiopia. Here. it isfully integrated into <strong>the</strong> diet and into<strong>the</strong> farming systems. and long-termdata on wheat performance areavailable (4). In several o<strong>the</strong>r countriesin <strong>the</strong> tropical belt. wheat wasintroduced by European and Arabtraders and settlers after <strong>the</strong> year 1500.Before <strong>the</strong> 19708. wheat was mainlygrown in <strong>the</strong> tropics as a cash crop forexport or to feed expatriates (1.3.6.7.13.15.23). In <strong>the</strong> 1970s. local wheatconsumption increased (5). world wheatprices were subject to large pricefluctuations (14) and wheat productionfor local consumption became more andmore important. e.g.. in Zambia andThailand (6.8). In tropical countries.wheat production still needs to beintegrated into <strong>the</strong> farming systems.and long-term data are scarce or notreadily available. Possibtlities andconstraints need to be investigatedbefore large-scale wheat production isundertaken (6.9); if not. costly errorsmay be made. giving negative stimulito local wheat production. Following areexamples of simple simulation modelsthat may be of assistance In localagricultural research.Simulation Modelsand calculation MethodsAt present. modeling can be used forthree sets of conditions or productionlevels (12):• Production Level I-Growth islimited by genotype and interactionwith wea<strong>the</strong>r (temperature. radiation.etc.)• Production Level 2-Growth islimited by water shortage and bywea<strong>the</strong>r conditions part of <strong>the</strong> time• Production Level 3-Growth Islimited by nitrogen shortage. watershortage and wea<strong>the</strong>r part of <strong>the</strong>timeSimulation of conditions wherebygrowth may also be limited by nitrogen.phosphorus. o<strong>the</strong>r minerals. water andwea<strong>the</strong>r conditions is not yetsufficiently advanced for practical use.Models have been made that use day-todayinput or mean daily data averagedover a five (17) or ten-day period (18.19.20.21). While in many areas day-todaywea<strong>the</strong>r data are not available. .monthly data are available. In modelsfor both short-eyc1e spring or summerwheat (21) and 10ng-eyc1e winter wheat(17). monthly data and long-term data

287can be used. The computer is a usefultool to reduce <strong>the</strong> time needed forcalculations, but simulations can alsobe performed with a desk calculator(18,20).At Production Levell. irradiation andtemperature are two factors ofimportance for dry-matter production ofa wheat crop during development fromemergence to maturity. Biotic andabiotic factors o<strong>the</strong>r than globalradiation and temperatures areassumed to be nonlimiting. Simplesimulation models and calculationmethods can define <strong>the</strong> phenologicalstate of <strong>the</strong> crop, making use of heatsums expressed in degree days. Thisnot only applies to Production Levell,but can also be applied to levels 2 and 3(17,18,19,20,21). Rate of plantdevelopment is governed by geneticproperties and environmentalconditions. Genetype accounts for <strong>the</strong>distinction in short, medium and longmaturationtypes (Table 1), whileenvironmental factors cause variationsin growth duration for one genotypebetween locations and seasons.Presently, <strong>the</strong> effects of day length aredifficult to describe quantitatively. Theheat sum for <strong>the</strong> period from an<strong>the</strong>sisto maturity appears to be constant forwheat genotypes (22).Potential yields (root, shoot and grain)can be calculated for crops sown atdifferent dates, in different years and atdifferent locations, as was demonstratedwith a model developed for Zambia (21).Thus, simple simulation models canhelp, among o<strong>the</strong>r things, to eliminateareas unsuitable for production, toidentify potentially suitable areas forresearch and production and to plan forSOWing-date experiments at one or morelocations. The influence of <strong>the</strong> durationof <strong>the</strong> vegetative period (to an<strong>the</strong>sis of<strong>the</strong> plant) on calculated yields for wheatsown at a given location at differentdates can be evaluated (21). This mayhelp in deciding whe<strong>the</strong>r to use short,medium or long-maturation cultivars.Using <strong>the</strong> heat sum, <strong>the</strong> maturation ofvarious phenological development stagesof wheat, as well of rice, maize andTable 1. Heat sum in degree days (oCd) above a base temperature of OOC forwheat and riceGenotypeDegree days (oCd)Emergence An<strong>the</strong>sisto an<strong>the</strong>sis to maturity TotalWheatShort maturation~./Emergence January 1Emergence July 1Medium maturatioF~/Long maturatio#82095011001175-13509009009009001720185020002075-2250Ric~./Short maturationMedium maturation~a503400Sources:!.f Van Keulen and De Milliano (21)~/ Van Keulen and Seligman (22)£. VanKeulen (18)

288sorghum. can be calculated. This maybe useful for agronomists and breederswhen planning visits to experiments atvarious locations.Van Keulen (12.19.20) developed acalculation method for estimating cropyields at Production Level 2 where. attimes during <strong>the</strong> growing season. watermay be a limiting factor. The degree ofwater shortage for <strong>the</strong> crop. duringdifferent periods. can be calculated.This gives an indication of whatamount of irrigation water is necessaryto achieve potential production andwhen to apply supplemental irrigation.Existing simulation models forProduction Level 3 are still in apreliminary stage. for use only byspecialized scientists (12.22).DiscussiuDOne of <strong>the</strong> problems in interpreting <strong>the</strong>results of long-term yield trials is <strong>the</strong>assessment of <strong>the</strong> relative influence ofgenotype characteristics. environmentalfactors and management practices on<strong>the</strong> final results in a particularsituation. This difficulty limits <strong>the</strong>possibilities for extrapolation of resultsto o<strong>the</strong>r areas. where less-detailedexperiments have been carried out orfor generalization over longer timeperiods. The use of models. in which<strong>the</strong> influence of such factors isdescribed quantitatively. may behelpful in analyZing experimentalresults and applying <strong>the</strong>m for <strong>the</strong>purpose of prediction. At present.simple models at Production Levels 1and 2 may be useful to agronomists.breeders and planners.Table 1 shows that <strong>the</strong> total heat sumfor <strong>the</strong> development of wheat fromemergence to maturity is considerablylower than for rice. One interestingchallenge to breeders could be toincrease this total heat sum: this mightfacilitate <strong>the</strong> introduction of wheat intowarmer areas. Preventive breeding mayalso be an important element of overallcrop improvement. in order to prevent<strong>the</strong> increase of minor pests andpathogens already present in <strong>the</strong>ecosystem and to preclude futureproblems (2).In <strong>the</strong> model by Van Keulen and deMilliano (21). actual grain numbers arenot simulated: ra<strong>the</strong>r. a function isintroduced in <strong>the</strong> model representingthis sink-effect. When <strong>the</strong> maximumtemperature is above 25°C in <strong>the</strong> tendayan<strong>the</strong>sis period. only a fraction ofavailable carbohydrates is translocatedto <strong>the</strong> grain. This fraction declines withincreasing temperatures. reaching 0 at35°C. This model worked well forZambia. but not for Niger. In Niamey.Niger. maximum air temperatureduring an<strong>the</strong>sis is between 35 and40°C. In reality. a grain yield of 2.4 Uhacan be achieved. which is more thantwice <strong>the</strong> amount calculated by <strong>the</strong>model (1.1 Uha). even if <strong>the</strong> influence ofmaximum air temperature on seed setis removed. EVidently. <strong>the</strong> model needsfur<strong>the</strong>r improvement for widerapplication. especially for areas wheremaximum air temperatures during <strong>the</strong>growing season exceed 30°C.How existing cultivars behave underhigh temperatures is still a subject ofstudy (10.11.24). Vernalization andphotoperiod sensitivity can delay <strong>the</strong>rate of plant development untilan<strong>the</strong>sis. but <strong>the</strong> delay may not bematched with an increase in number ofgrains per spikelet or per spike (10).Genotypes which are relativelyinsensitive to vernalization andphotoperiod and. hence. early. appearto be best at many locations. especiallyat hotter. lower elevations (11). Most of<strong>the</strong> models mentioned here apply togenotypes (bread and durum wheats)which are relatively insensitive tovernalization and photoperiod andfollow <strong>the</strong> universal heat sum well. Careshould be taken with <strong>the</strong> application ofdata and experience collected inwestern high-input systems to o<strong>the</strong>ragricultural systems (6.17). Therefore.local research should precedeproduction.

289The computer has become a valuableassistant to <strong>the</strong> agronomist (16), and isa useful tool for performing simulations.The thinking, data interpretation andsyn<strong>the</strong>sis, however, still need to bedone by man. Where money is alimiting factor, time is usually not aslimiting. In <strong>the</strong>se areas, <strong>the</strong> calculationmethods mentioned can be performedwith a desk calculator.The use of simulation models foragrometeorological purposes indeveloping countries was recognized by<strong>the</strong> World Meteorological Organization.In 1983, <strong>the</strong>y organized a workshop inWageningen, Ne<strong>the</strong>rlands, to trainstudents from various tropical countries(20). The Centre for World Food Studiesalso developed simulation models fordifferent countries, such as Bangladesh,Thailand and Indonesia. Some of <strong>the</strong>models are available in a simple formfor use by individuals and researchcenters.AcknowledgementsThe authors wish to thank CIMMYT forinviting <strong>the</strong>m to present this paper, andR Villareal and S. Waddington forcritical review of <strong>the</strong> article.References1. Azzi, G. 1927. Le climat du ble dansIe monde: les bases ecologiques de laculture mondiale du ble. FAO.Rome, Italy.2. Buddenhagen, I.W., and O.M.B. DePonti. 1983. Crop improvement tominimize future losses to diseasesand pests in <strong>the</strong> tropiCS. FAO PlantProtection Bulletin 31:11-30.4. Ciccarone, A. 1947. II problemadelle ruggini dei grani in Etiopia.Tre anni di osservazioni (1938,1939, 1940). Instituto Agronomicoper l'Africa Italiana, Florence, Italy.5. CIMMYT. 1983. World Wheat Factsand Trends Report 2. CIMMYT,Mexico.6. De MUUano, W.A.J. 1983.Improvement of wheat in Zambiausing incomplete resistance againstrusts. PhD Thesis. State AgriculturalUniversity, Wageningen,Ne<strong>the</strong>rlands.7. Fuggles-Couchman, N.R 1951.Wheat production in Tanganyika.World Crops 3:183-187.8 . Harrington, L.W., S. Sat-thapornand C. Chavewong. 1984. GroWingwheat in Thailand: An overview ofeconomic issues. 1984 AnnualWheat Workshop, Chiang Mai,Thailand, January 21-22, 1984.9. Hurd, E.A. 1981. Status of researchand production, Zambia. InProceedings of <strong>the</strong> Wheat Workshop,J.A. Toogood, ed. Mount MakuluResearch Station, ChUanga, Zambia.10. Midmore, D.J., P.M. Cartwright andRA. Fischer. 1982. Wheat intropical environments: I. Phasicdevelopment and spike size. FieldCrops Research 5: 185·200.11. Midmore, D.J., P.M. CartWright andRA. Fischer. 1~84. Wheat intropical environments. II. Cropgrowth and grain yield. Field CropsResearch 8:207.227. I3. Ca<strong>the</strong>rinet, M., and M. Miche. 1967.Le ble dans les pays d'Mriquecontinentale tropicale d'expressionFrancaise. L'Agronomie tropicale22:933-979.

29012. Penning de Vries, F.W.T.• and H.H.van Laar, eds. 1982. Simulation ofplant growth and crop production.Simulation Monograph. Pudoc,Wageningen. Ne<strong>the</strong>rlands III (ISBN90 220 0809 6).13. Pinto. F.F., and E.A. Hurd. 1970.Seventy years with wheat in Kenya.East African Agriculture andForestry Journal 36 (special issue).14. Priester. L.. and J. Stoof. 1983.Handel in honger. Vrij NederlandBijvoegsel 35:1·23.15. Ribeiro, F.G.C. 1949. Do trigo noimperio. Dissertacao EstudosColonais Economica Colonial.Lisbon. Portugal.16. Scott. N.H.• and W.A. Kronstad.1980. The computer: Anagronomist's assistant. InProceedings of <strong>the</strong> ThirdInternational Wheat Conference,Madrid. Spain. pp. 215-219.17. Terjung, W.H.• H.Y. Ji. J.T. Hayes.P.A. O'Rourke and P.E. Todhunter.1984. Actual and potential yield forrainfed and irrigated wheat inChina. Agricultural and ForestMeteorology 31:1·23.18. Van Keulen. H. 1976. A calculationmethod for potential rice production.Central Research Institute forAgriculture Contribution 21. Bogor,IndoneSia.19. Van Keuleri. H. 1980. Modelinggrain production of wheat underconditions of limiting water supply:A case study. In Proceedings of <strong>the</strong>Third International WheatConference. Madrid. Spain. Pp. 414419.20. Van Keulen. H. 1983. A calculationmethod for estimating crop yieldsunder conditions where at timesduring <strong>the</strong> growing season watermay be a limiting factor. WMOCourse. International AgriculturalCentre. Wageningen. Ne<strong>the</strong>rlands.21. Van Keulen. H.• and W.A.J. DeMilliano. 1984. Potential wheatyields in Zambia: a simulationapproach. Agricultural Systems14:171-192.22. Van Keulen. H., and N.G. Seligman.1984. Simulation of water use.nitrogen nutrition and growth of aspring wheat crop. SimulationMonograph. Pudoc. Wageningen.Ne<strong>the</strong>rlands. (In press.)23. Viana. P.A.F. 1937.0 trigo. culturade futuro. MocambiqueDocumentario TrimestralI2:77-93.24. Wall. P.C., and P.M. Cartwright.1974. Effects of photoperiod,temperature and vernalization on<strong>the</strong> phenology and spikelet numbersof spring wheat. Annals of AppliedBiology 76:299-309.

291IV. SeedWheat Seed Production,Storage and Distribution in BangladeshS.M. Ahmed, Bangladesh Agricultural Research Institute,Joydebpur, Dhaka, BangladeshAbstractThe initial expansion of high-yielding varieties of wheat in Bangladesh wasfacilitated by importing seed. However. researchers realized that it would beimpOSSible to increase and sustain wheat production without an efficient seedproduction. preservation and distribution system within <strong>the</strong> country. Importedseed would not be a dependable source due to possible unavailability offoreignexchangefor its purchase. <strong>the</strong> possibility of<strong>the</strong>re being inadequate quantities ofseed ofappropriate varieties availablefor purchase, and possible delays intransport and distribution which would hinder timely planting in <strong>the</strong> country. Inview of<strong>the</strong>se problems. <strong>the</strong> development oflow-cost technologyfor seed storageunderfarmers' conditions. as well as <strong>the</strong> establishment of national seedproduction agencies, was imperative. The production, storage and distribution ofwheat seed are here discussed asfactors which have contributed to <strong>the</strong>dramatic expansion of<strong>the</strong> area under wheat in Bangladesh.In Bangladesh, <strong>the</strong> initial expansion ofhigh-yielding varieties of wheat wasfacilitated by <strong>the</strong> importation of seed.Environmental conditions, such as <strong>the</strong>short growing season. high humidityand possible premature monsoon rains.were <strong>the</strong>n thought to precludesuccessful seed production in <strong>the</strong>country. However, research personnelrealized that it would be impossible toincrease or sustain <strong>the</strong> wheatproduction area without an efficientseed production, preservation anddistribution system within <strong>the</strong> country.The reasons for this were:• Foreign exchange might not beavailable for seed imports every year;• Adequate quantities of seed ofappropriate varieties might not beavailable for purchase, and• Delays in arrival of seed and itsinternal distribution could hinder <strong>the</strong>timely planting essential for goodyields;In view of <strong>the</strong>se problems, <strong>the</strong>development of low-cost technology forseed storage under farmers' conditions.as well as <strong>the</strong> establishment of anational seed production agency. wasimperative. Surveys conducted in 1976(1) and 1977 (8) indicated that about80% of <strong>the</strong> seed required annually wasstored by farmers. Had <strong>the</strong>y not storedwheat seed. <strong>the</strong> dramatic expansion of<strong>the</strong> area under wheat would not havebeen possible.In spite of <strong>the</strong> spectacular success ofon-farm storage, some seed is alwayslost due to spoilage caused by earlyrains. insect and rat damage. flooding.loss of Viability due to <strong>the</strong> failure orinability of <strong>the</strong> farmer to dry his seedstock. or consumption of <strong>the</strong> seedbecause of <strong>the</strong> failure of <strong>the</strong> rice crop.Also. <strong>the</strong> demand for wheat seedincreases or decreases depending onwea<strong>the</strong>r conditions. For example. since60 to 70% of <strong>the</strong> wheat crop is rainfed,favorable rains just prior to <strong>the</strong> wheatseason make more land available forplanting, and <strong>the</strong> demand for seed willbe high. Thus. a strong national(private or public) seed production effort

292is needed to arrange for adequate seedstock during years of high demandand/or seed loss. In addition to <strong>the</strong>seproblems of on-farm storage. privateseed stocks invariably become mixedover time. A good national seedprogram can ensure an annual injectionof seed of pure varieties into <strong>the</strong>agricultural system.Seed ProductionWheat. of course. is most suited totemperate regions. where temperaturesare relatively lower and <strong>the</strong> growingseason longer. In Bangladesh. amaximum of 115 days on average areavailable for <strong>the</strong> production of wheatunder conditions that can lead tofavorable yield. The earliest possibletime for seeding presently availablevarieties is late October or earlyNovember; however. high air and soiltemperatures at that time result in poorstands. low tillering and prematureheading. Seeding in December.although more favorable in terms oftemperature. results in decreased yieldand in smaller and occasionallyshriveled grains due to <strong>the</strong> fur<strong>the</strong>rshortening of <strong>the</strong> growing season. Midto late November is <strong>the</strong> period mostfavorable for planting wheat. a timerange that is quite limited.Temperatures may fluctuatedramatically during <strong>the</strong> growingseason. and <strong>the</strong>se fluctuations affectvegetative growth and flowering ofwheat plants. However. Bangladesh isfortunate in that relatively cool andfavorable temperatures prevail from lateNovember to late February. In moretropical countries. temperatures remainhigh or show little variation betweenday and night. In those countries.production of good quality wheat seedis. of course. even more difficult.In Bangladesh. <strong>the</strong> risk of pre-monsoonrains is always high. These rains delayharvesting and affect viability of <strong>the</strong>seed in <strong>the</strong> field. Even if <strong>the</strong> crop isharvested in time. rain may delaythreshing. resulting in <strong>the</strong> deteriorationof grain quality and predisposing <strong>the</strong>seed to fungal pathogens. Fur<strong>the</strong>r.during <strong>the</strong> months of March and April.<strong>the</strong>re are occasional hailstorms; <strong>the</strong>yare usually localized. but may damage<strong>the</strong> crop severely. Relative humidityalso rises rapidly during <strong>the</strong> peakharvesting month of March. Unless seedis dried properly. moisture content willbe excessive and will result in apredisposition to fungi. insect damageand decreased viability due to higherrespiration rates.Despite <strong>the</strong>se problems. it would seemthat successful seed programs can beconducted in any country where awheat crop is economically grown.problems are adequately identified. careis taken to produce seed on <strong>the</strong> mostfavorable sites and inputs are availableto ensure successful preservation.Production of quality seedRainfall and temperature data ofdifferent zones of <strong>the</strong> country overseveral years must be examined beforebeing able to select sites for wheat seedproduction. It is essential to chooserelatively dry areas with irrigationfacilities and with crop rotation patternsthat permit <strong>the</strong> maximum amount oftime favorable for wheat growth. Poorlydrained soils and very sandy soils withpoor water-holding capacity should beavoided.Mid-November is <strong>the</strong> best time forplanting wheat in Bangladesh. Themean temperature goes down to about23°C dUring this time. facilitating goodstand establishment and tillering of <strong>the</strong>crop. Wheat planted in mid-Novemberand harvested in ei<strong>the</strong>r late February orearly March usually escapes hightemperatures at <strong>the</strong> grain filling stageand rainfall at maturity. Crops plantedlater will produce increasingly higherproportions of small and shriveledgrains.

293On average, no more that 100 mm ofrain falls during <strong>the</strong> wheat season. Toensure good yields, <strong>the</strong> crop should beirrigated at crown root initiation,heading and grain ruling (subject to <strong>the</strong>moisture status of <strong>the</strong> soU). A 34% yieldreduction has been observed if <strong>the</strong> cropis not irrigated at least twice (4).Fertilizer application in adequatequantities is also essential, with <strong>the</strong>amounts adjusted to site requirements.Classes of seedIn order to maintain varietal purity andquality, four classes of seed areproduced at different stages of seedproduction (2):••Breeder seedPre-foundation seed• Foundation seed• Certified seedThe standards for breeder, foundationand certified wheat seed fixed by <strong>the</strong>National Seed Broad, are given inTable 1.Breeder seed-Breeder seed is <strong>the</strong>purest seed produced by <strong>the</strong> sponsoringplant breeder or institution for <strong>the</strong>initial increase of foundation seed; it isproduced on a very small scale. InBangladesh, <strong>the</strong> production of adequatequantities of certified seed from breederseed takes nearly four years.Pre-foundatton seed-A promising lineis multiplied and purified prior to itsfonnal release as a variety. This is donein order to be able to supply a relativelylarge amount of seed to <strong>the</strong> NationalSeed Producing Agency at <strong>the</strong> time ofits release. By this method, <strong>the</strong> amountof time between <strong>the</strong> fonnal release of avariety and its general release to <strong>the</strong>public is minimized.Foundatton seed-Breeder seed and/orpre-foundation seed received from <strong>the</strong>research program is used for <strong>the</strong>production of foundation seed and isgrown on seed multiplication fanns.The program for <strong>the</strong> multiplication offoundation seed is fonnulated on <strong>the</strong>basis of distribution targets for certifiedseed as fixed for a given year. The seedcorporation must ensure <strong>the</strong>production, processing, preservation,packing and distribution of foundationseed to certified seed growers. InBangladesh, foundation seed isproduced on 16 seed multiplicationfanns which occupy a total area ofsome 900 hectares and produce about1500 tons of seed annually.Certtjled seed-Foundation seedproduced in <strong>the</strong> seed multiplication.lanns is planted by contract growers forproduction of certified seed. Thecontract grower areas are selectedaccording to <strong>the</strong> follOWing criteria:• Availability of irrigation water• Accessibility of roads• SUitability of <strong>the</strong> soil• Topography of <strong>the</strong> land• Proximity to seed processing centersTable 1. Standards for breeder, foundltion and certified wheat .ed as fixed by <strong>the</strong> NationalSeed Board, BangladeshMaximum foreign matter permitted (°/0) MaximumClass of Minimum Minimum moistureseed germination pure .ed Ine" O<strong>the</strong>r wheat O<strong>the</strong>r crop Weed content(°/0) (°/0) matter varieties .eds .eds (°/0)Breeder 90.0 94.5 0.7 0.3 0.5 8 seeds/kg 12.0Foundation 80.0 96.0 2.0 1.0 0.5 0.5 12.0Certified 80.0 92.0 2.5 2.5 0.5 0.5 12.0

294In addition to seed, inputs such asfertilizer, pumps, pesticides and creditsare provided to <strong>the</strong> grower. The fieldstaff of <strong>the</strong> Seed Producing Agencysupervise and gUide all operations, fromsowing to threshing.A seed production zone must be locatedin close proximity to a seed processingcenter. In each zone, <strong>the</strong>re may bethree to five seed units which comprise120 to 240 hectares of land each. Ineach seed unit, <strong>the</strong>re are four to eightblocks comprising 30 to 60 hectareseach (3). The Seed Certification Agencycertifies <strong>the</strong> seed plots after inspectionand issues certificates. They also certify<strong>the</strong> seed lots after final processing andstorage.The seed growers deliver <strong>the</strong>ir certifiedcrops to <strong>the</strong> seed processing/purchasingcenter immediately after harvest. TheSeed Producing Agency accepts onlycertified seed of approved standardsand makes payment to <strong>the</strong> growers at<strong>the</strong> rate fixed in consultation with <strong>the</strong>local Price Fixing Committee. Contractgrowers receive a premium price 20%higher than <strong>the</strong> Governmentprocurement price (7). About 9,000hectares are brought under certifiedseed production in Bangladesh everyyear; total production is about 14,000tons.Seed production at <strong>the</strong> farmer levelMost farmers cannot buy wheat seedevery year, and those who successfullystore <strong>the</strong>ir own seed have <strong>the</strong>advantage of being able to plantwhenever <strong>the</strong>y wish. A farmer inE mgladesh keeps as seed a portion of<strong>the</strong> grain after threshing and cleaning;as a result, over a period of years, <strong>the</strong>quality of <strong>the</strong> seed goes down due tomixtures with o<strong>the</strong>r varieties of wheator o<strong>the</strong>r crop seeds. This can beavoided if farmers are trained byextension personnel to clean (rogue) aportion of <strong>the</strong> wheat field for seedproduction. Good quality wheat seedcan <strong>the</strong>n be obtained if <strong>the</strong> farmer isable to harvest <strong>the</strong> crop during sunnyperiods, facilitating <strong>the</strong> proper drying of<strong>the</strong> plants and <strong>the</strong> seed.StorageThe storability of wheat seed in aspecific environment is largelydetermined by its prestorage history.Untimely harvesting and threshing,inadequate drying and carelesshandling increase quality losses fromfield exposure, high moisture contentand mechanical damage (6). Excessiveseed moisture is <strong>the</strong> greatest singlefactor causing losses in Viability andVigor; delayed harvesting and inefficientdrying may contribute considerably to<strong>the</strong> low quality of seed.On-farm storageLow-cost technology for storing wheatseed, developed through research in <strong>the</strong>mid-1970s, has been adopted by mostwheat farmers in Bangladesh. Afterthreshing and cleaning, <strong>the</strong> seeds aredried in <strong>the</strong> sun for at least six or sevenconsecutive days. This natural dryinglowers <strong>the</strong> moisture content of <strong>the</strong> seedto about 10%. It is <strong>the</strong>n allowed to coolovernight and is stored in containers,such as tins, metallic drums, ear<strong>the</strong>npots or polyethylene bags. A total of 25different forms of on-farm seed storagehave been reported in Bangladesh (5).The container most preferred by wheatfarmers for on-farm seed storage is a200-liter petroleum or insecticide drum.The seed stored in <strong>the</strong>se drums isusually found to have germinationabove 80% (5). However, since <strong>the</strong> priceof such drums is high (US$ 10 to 12),most farmers cannot afford to buy<strong>the</strong>m. Moreover, <strong>the</strong> capacity of <strong>the</strong>sedrums is 186 kg and <strong>the</strong> majority of <strong>the</strong>farmers require containers with acapacity of less than 70 kg.

295Storage in 20-liter biscuit or kerosenetins is very effective. They have <strong>the</strong>advantage of smaller capacity (18 kg)and lower price (US$ 1). Unlike o<strong>the</strong>rcontainers. seed can be placed in tincontainers immediately after sun drying(i.e.• without overnight cooling). Since<strong>the</strong> tin is thin and is a good heatconductor. <strong>the</strong> heat is quicklydispersed.The insertion of a double plastic baginside fertilizer or gunny sacks alsomakes <strong>the</strong>m useful for seed storage;germination of over 80% may bemaintained in <strong>the</strong>se bags. Their storagecapacity (about 37 to 74 kg) meets <strong>the</strong>requirements of <strong>the</strong> average farmer.and <strong>the</strong>y are very cheap and generallyaVailable. However. for protectionagainst rats. <strong>the</strong> bags should be keptwithin ear<strong>the</strong>n containers or onsuspended platforms (5).Wheat seed is also kept in bamboo andmud storehouses (kuti); <strong>the</strong>se are usedfor rice storage but do not adequatelyprevent dampness. Ear<strong>the</strong>n pots arealso occasionally used. but do notprevent dampness ei<strong>the</strong>r due to <strong>the</strong>irporosity. Such containers should becoated with tar and sealed for mosteffective use. If containers are relativelyairtight. <strong>the</strong>re is no need to redry <strong>the</strong>seed during <strong>the</strong> storage period;o<strong>the</strong>rwise. seed should be dried five tosix times.A survey conducted in 1982 indicatedthat about 12% of <strong>the</strong> seed samplescollected had been treated withinsecticides. Some farmers use naturalinsecticides such as nim. biskatali andtobacco leaves as insect repellants.Fur<strong>the</strong>r research is needed to determine<strong>the</strong> efficacy of natural insecticides incontrolling insects in stored seed.Seed corporation storageTaking into account <strong>the</strong> adverseenvironmental conditions for any typeof seed storage in <strong>the</strong> tropiCS. only acombination of recommended practices,well-maintained storage facilities andcareful seed packaging will guaranteethat, once harvested. high quality seedwill reach <strong>the</strong> farmer without loss ofViability. The seed processing centershould be proVided with moisture-proofseed storage. with <strong>the</strong> capacity to store<strong>the</strong> total quantity of seed produced. InBangladesh. seed is stored in gunnysacks for ease of handling but. since <strong>the</strong>duration of storage is usually sixmonths. <strong>the</strong> bagged seed is periodicallydried by forced-air drying; germinationis checked frequently.Control of pests and diseasesPests which have to be controlled instorage include rodents and insects.Specific measures should beundertaken in buildings used forstorage to prevent <strong>the</strong> entry of rats;insects are more difficult to control.Insects live in cracks and crevices ofbuildings. in old bags and may alsocome from <strong>the</strong> field with <strong>the</strong> seed.Floors and walls can be sprayed withappropriate long-term residualinsecticides for control. In Bangladesh.insecticides are not used for treatingseed. since leftover or unused seed maybe used by <strong>the</strong> farmer for consumption.Hence. fumigation by Phostoxin is doneas a regular practice.Seed DistributionDistribution by<strong>the</strong> seed corporationThe price of seed is fixed by <strong>the</strong>Bangladesh Government prior todistribution. The seed is bagged. sent todistribution points and. finally. sold togrowers. An excessively high price ofseed will discourage <strong>the</strong> farmers fromplanting wheat. while an excessivelylow price will encourage <strong>the</strong> misuse ofcostly seed for consumption and alsodiscourage on-farm preservation.,InBangladesh. <strong>the</strong> price of wheat seedsupplied by <strong>the</strong> seed corporation is

296fixed at 15 to 20% more than <strong>the</strong> grainprice (7). In order to enable <strong>the</strong> farmersto buy at least a small quantity ofquality seed. such locally produced seedis made available in distinctive 10 to 20kg bags. This practice also reduces <strong>the</strong>chances of unscrupulous private seedtraders selling poor quality seed.District-wide requirements for wheatseed are set by <strong>the</strong> extensiondepartment every year well ahead of<strong>the</strong> wheat season and on <strong>the</strong> basis of<strong>the</strong> target fixed for that year. Thedistribution program is set up by <strong>the</strong>seed corporation. in consultation withresearch and extension personnel. Witha view to making seed easily availableto growers. it is sent from <strong>the</strong> seedprocessing centers to district salescenters just before <strong>the</strong> sowing period.The seed is sold from <strong>the</strong> sales centersdirectly to <strong>the</strong> growers. For qUick andeasy distribution. <strong>the</strong> sales centers arelocated close to main roads or railroads.On-farm seed distributionThe farmer who stores an excessquantity of seed often sells it toneighboring farmers or in <strong>the</strong> localmarket. About 5 to 10% of wheat seedis distributed in this way inBangladesh.A large number of on-farmdemonstrations are conducted with newvarieties by research in collaborationwith <strong>the</strong> extension department.Cooperating farmers are encouraged tokeep seed from <strong>the</strong> variety he findspromising for use <strong>the</strong> next year. He isalso encouraged to sell a portion of thatseed to o<strong>the</strong>r farmers. On-farmdemonstrations are one of <strong>the</strong> mosteffiCient methods for <strong>the</strong> introductionand distribution of new varieties to <strong>the</strong>farmer.References1. Ahmed. S.M. 1976. Survey of wheatseeds stored by <strong>the</strong> farmers forsowing in 1976-77. BangladeshAgricultural Research InstituteReport. Joydebpur. Bangladesh.(Unpublished.)2. Bangladesh AgriculturalDevelopment Corporation. Manualof Seed Multiplication Farms. P. 14.3. Bangladesh AgricultureDevelopment Corporation. Manualof Seed Production throughContract Growers. P. 19.4. Bangladesh Agricultural ResearchCouncil. 1982. CoordinatedIrrigation and Water ManagementAnnual Reports 1980-81 and 198182. Joydebpur. Bangladesh.5. Clements. D.J.• A. Ahmed andM.M. Hoque. 1984. On-farm wheatseed storage in Bangladesh. Surveyreport. Agriculture Sector Team.Canadian InternationalDevelopment Agency.6. Doerfler. T. 1976. Seed ProductionGuide for <strong>the</strong> Tropics. Published by<strong>the</strong> German Agricultural Team inSri Lanka. Colombo. Sri Lanka. Pp.125-126.7. Hashem. A. Seed Industry inBangladesh. Published by <strong>the</strong>Bangladesh AgriculturalDevelopment Corporation. P. 10.8. Razzaque. A.• A.B.S. Hossain,A. Ahmed and M. Hoque. 1977.Wheat seeds and <strong>the</strong>ir storageunder farmers' condition inBangladesh. Paper presented for <strong>the</strong>Seminar and Workshop.Bangladesh Association for <strong>the</strong>Advancement of Science,Chittagong University. Bangladesh.

Production, Storageand Marketing of Wheat Seed in IndiaS.B. Singh, U.P. Seeds and Tarai Development Corporation, Baldi(Patnagar), Nainital, IndiaAbstractBoth <strong>the</strong> production and productivity ofwheat has increased in India to anappreciable extent since <strong>the</strong> introduction of<strong>the</strong> semidwarf varieties from MeXico,and concerted efforts have been made in <strong>the</strong> multiplication ofquality seed.Production has gone up from 12.25 million tons in 1965-66 to 42.5 million tonsin 1983-84; productivity has increasedfrom 913 to 1863 kg/ha. Certified seedproduction has increasedfrom approximately 50,000 tons in 1974-75 to 230,000tons in 1983-84. Marketing ofseed is arranged through public and private-sectoragencies. To curb <strong>the</strong> sale ofspurious seed, seed law is enforced through <strong>the</strong>1966 Seeds Act. Heavy dependence on afew varieties and <strong>the</strong> spread of karnalbunt (Neovossia indica) pose a serious threat to wheat cultivation in <strong>the</strong> country.Breeder seed multiplication needs to be streng<strong>the</strong>ned, and a buffer stock ofseedmaintainedfor stability in production.297In increasing crop production and yield,seed plays a vital role. It is not justano<strong>the</strong>r agricultural input, but ra<strong>the</strong>r adynamic instrument used to achievespecific agricultural productionobjectives. There cannot be a morepotent tool for peace, progress andprosperity than seeds for developingcountries, such as India, Pakistan,Nepal, Burma, Bangladesh andIndonesia, where agriculture is <strong>the</strong>backbone of <strong>the</strong> national economies.The discovery of dwarf plant types in<strong>the</strong> world's popular food-grain crops,e.g., wheat and rice, and <strong>the</strong> spread ofseed of adapted andhigh-yieldingvarieties may be conSidered much moresignificant and revolutionary than <strong>the</strong>discovery of atomic power.The 1960s was a turning-point in <strong>the</strong>history of agriculture on <strong>the</strong> Indiansubcontinent, with <strong>the</strong> introduction of<strong>the</strong> semidwarf wheat varieties, such asSonora 63, Sonora 64, Lerma Rojo 64and Mayo 64, along with a largenumber of segregating materials fromCIMMYT, Mexico (1963-64). About <strong>the</strong>same time, <strong>the</strong> rice varieties Taichungand Nitan were introduced from Taiwan(1964) and IR8 from IRRI in <strong>the</strong>Philippines (1965). The introduction of<strong>the</strong>se varieties, and <strong>the</strong>ir fur<strong>the</strong>rdevelopment through multidisciplinarycrop improvement projects, broughtnew hope for increasing foodproduction in India and paved <strong>the</strong> wayfor <strong>the</strong> reconstruction of native varietiesto cater to <strong>the</strong> needs of varyingecological conditions.The Seed IndustryFarmer acceptance of <strong>the</strong> introducedvarieties in all parts of <strong>the</strong> country led<strong>the</strong> Government of India to extend itssupport to supplying good quality seed,as well as fertilizers and pesticides.Wheat production has increased from12.25 million tons in 1965-66 to 42.5million tons in 1983-84, withproductivity going up from 913 kg/hato 1863 kg/ha.In <strong>the</strong> early 1960s, <strong>the</strong> seed industry in<strong>the</strong> country was poorly developed. Theprivate sector produced small quantitiesof flower and vegetable seeds, and <strong>the</strong>public sector attempted to disseminateimproved seed from small governmentownedfarms, but with little success. Inorder to meet <strong>the</strong> grOWing demand forquality seed, <strong>the</strong> government

298established <strong>the</strong> National SeedCorporation (NSC) in 1963. and passed<strong>the</strong> Seeds Act in 1966. The NSC wascharged with promoting <strong>the</strong>development of a seed industry. fromproduction through processing. storageand marketing. and to establish asystem for quality control. However.large quantities of quality seed couldnot be produced in <strong>the</strong> absence of anorganized seed industry at <strong>the</strong> statelevel. In 1966. a team. consisting ofexperts from <strong>the</strong> World Bank and FAO.visited India and identified Pantnagaras <strong>the</strong> best location for launching <strong>the</strong>seed project. with <strong>the</strong> close coordinationof <strong>the</strong> G.B. Pant University ofAgriculture and Technology. Thus. <strong>the</strong>Tara! Development Corporation (TDC)was established in 1969. with <strong>the</strong>asistance of <strong>the</strong> World Bank. and wasan important landmark in <strong>the</strong>production of seed in India. The TDCundertook large-scale production ofcereals seed. particularly wheat seed.which constituted more than 75% of<strong>the</strong> total seed production of <strong>the</strong>corporation. From 7.013 tons ofcertified quality wheat seed produced in1969-70, production had increased to37.500 tons by 1983-84: this will befur<strong>the</strong>r increased to 75.000 tons by1988-89.National seed programBased on <strong>the</strong> success of <strong>the</strong> TDC. <strong>the</strong>Government of India decided toreorganize and expand <strong>the</strong> seedindustry in <strong>the</strong> country. taking <strong>the</strong> TDCas a mo<strong>the</strong>r-project. In February. 1975.a working group w~ established toprepare proposals for a National SeedProgram. Under this program. a StateSeed Corporation (SSC) was establishedin various states. At present. nine statesare participating in <strong>the</strong> program andhave established SSCs. similar to TDC.which are responsible for seedproduction. processing. quality controland marketing.Wheat Seed ProductionWith <strong>the</strong> growing consciousness amongfarmers of <strong>the</strong> advantage of usingcertified seed of good quality. demand in<strong>the</strong> country has increased many times.From <strong>the</strong> total production of about50.000 tons of seed in 1974. i.e.. before<strong>the</strong> beginning of <strong>the</strong> National SeedProgram. present availability of wheatseed in <strong>the</strong> country is 230.000 tons.This amount is sufficient to cover about10% of <strong>the</strong> area under wheat cultivation.The government is very anxious toincrease seed production to be able tocover at least 20% of <strong>the</strong> wheat area by1988-89. Thus. <strong>the</strong> country has set atarget of doubling wheat seed production(to 500.000 tons) through private andpublic-sector agencies over a period offive years. The important varieties underproduction in <strong>the</strong> country are:Sonallka(1I53-388 x An)Yt54 xNI0B)LR). UP262(S308 x Bajio 66).HD2285(249-HD21601HD2186).WL711(S308 x Chris)Kalyansona).HD2009(Lerma Rojo 64A x Nai 60).UP368(LR64 x Sonora 64).HD2204(HD2092/HDI962-E4870-K65).HUW37(Kalyansona x 5331) x HDI982).HPII02(8156(B) x NAD 63). WH147(E4870 x C303)(5339 x VI8). Raj 911(V0229) and DWLS023 (Cr"S"-Ld"S" xGrOOS"). At present. Sonalika (RR21) is<strong>the</strong> most popular variety in Indiabecause of its high yield. wideadaptability. rust resistance andSUitability for late sowing in fieldsfollowing paddy crops. It currentlycovers an area of apprOXimately 10million hectares.For <strong>the</strong> maintenance of genetic purityand consistency of seed production. <strong>the</strong>country is producing three categories ofseed. breeder. foundation and certifiedseed.Breeder seedThe breeder who developes a variety isgenerally responsible for <strong>the</strong>maintenance and production of <strong>the</strong> pureseed of that variety. About 2.000 plants.

299true to type. are selected and threshedindividually. Progeny rows are grownand progenies containing off-types areremoved before harvest; <strong>the</strong> seed of <strong>the</strong>remaining progenies are mixed to formbreeder seed. Breeder seed is monitoredby a committee composed ofrepresentatives of <strong>the</strong> Indian Council ofAgricultural Research, <strong>the</strong> NSC. <strong>the</strong>State Seed Certification Agency (SSCA)and <strong>the</strong> breeder.Foundation seedFoundation seed production of allIndian varieties is arranged by <strong>the</strong> NSC;<strong>the</strong> SSC undertakes <strong>the</strong> production ofvarieties on <strong>the</strong> state level. Because ofincreased demand for certified seed ofcertain varieties. it has becomenecessary to undertake a second stageof foundation seed production. which isknown as Foundation Seed Stage II.Certification and "grow-out testing" ofall foundation seed lots are carried outby <strong>the</strong> SSCA. The grow-out test servesas both a postcontrol test for <strong>the</strong>foundation seed and a precontrol testfor certified seed.Certified seedCertified seed production is carried outby public as well as by private agenCies.The certification is optional, and iscarried out by an independentcertification agency. The only varietieswhich come under review forcertification are those which have beenreleased by ei<strong>the</strong>r <strong>the</strong> State or CentralSubcommittee on Release of Varietiesand duly certified by <strong>the</strong> Central SeedCertification Board.The public sector companies thatarrange for seed production throughregistered seed growers are shareholdersin <strong>the</strong> corporation and. thus.directly linked with <strong>the</strong> development of<strong>the</strong> corporation. However. productionwith contract growers is also arrangedto help achieve target quantities.In order to have better quality control,certification work is carried out by <strong>the</strong>staff of U.P. Seeds and TaraiDevelopment Corporation (UPSTDC) aswell as <strong>the</strong> SSCA. This system proVidesan opportunity for more inspections ofseed plots; it also proVides counterchecks. The seed producers are advisedto harvest <strong>the</strong>ir seed crops when <strong>the</strong>yhave appropriate moisture content,preferably 13%. to avoid mechanicaldamage. For <strong>the</strong> convenience of <strong>the</strong>seed producers. and to have effectivequality control. a representative sampleof raw (unprocessed) seed is drawnfrom <strong>the</strong> farmer's field and tested; onlythat seed which meets <strong>the</strong> prescribedstandards is accepted at <strong>the</strong> plant.After arriving at <strong>the</strong> plant, <strong>the</strong> seed isagain tested to confirm that <strong>the</strong> lotsmeet <strong>the</strong> prescribed standards. Thoselots meeting <strong>the</strong> standards are <strong>the</strong>nprocessed. i.e.. cleaned, graded. treated.packaged and labeled. Generally.drying is not reqUired as seed isreceived during <strong>the</strong> dry period andmoisture content in <strong>the</strong> grain at intaketime varies between 9 and 10%. Thecorporation has well-equippedprocessing plants with a total capacityof 65.000 tons; this is being expandedto 80.000 tons. Similarly, o<strong>the</strong>r seedcorporations in <strong>the</strong> country haveprocessing facilities in accordance with<strong>the</strong>ir production program.The UPSTDC has its own qualitycontrol system and does not rely totallyon <strong>the</strong> SSCA. Certain standards whichare not prescribed in <strong>the</strong> IndianMinimum Seed Certification Standardshave been incorporated into its seedproduction program. For instance, nostandard has been prescribed for loosesmut (Ustilago nuda tritici). but <strong>the</strong>corporation is testing for infection by atechnique called <strong>the</strong> mycelium test inevery lot of wheat seed it receives. LotshaVing more than 0.5% infected seedare subjected to special treatment witha systemic fungicide. Carboxin orCarbendazim. Similarly. lots haVinghigh amounts of rod kernel or spottedkernel are not accepted. This procedure

300is unique and is not presently followedby any o<strong>the</strong>r corporation in <strong>the</strong>country. although <strong>the</strong>re is an awarenessthat such a system should be adoptedby o<strong>the</strong>rs.The grow-out test of about 20% of <strong>the</strong>certified seed lots is carried out toascertain <strong>the</strong> quality of seed marketedby <strong>the</strong> corporation. To pin-pointmistakes in production. processing andmarketing. <strong>the</strong> identity of seed ofdifferent farmers is maintained byallocating separate seed lots.StorageThe moisture content of seed is a veryimportant factor. influencing itslongevity in storage. Wheat seed isharvested during <strong>the</strong> dry part of <strong>the</strong>year (April and May). when moisturecontent is low. However. mechanicaldrying becomes necessary when seedsget wet due to rains at <strong>the</strong> maturitystage. Wheat seed is stored over <strong>the</strong>monsoon. when relative humidity ishigh. until <strong>the</strong> planting season inNovember and December. During thisperiod. seed is likely to take upmoisture. and it deteriorates if notproperly stored. Because of this fact.<strong>the</strong> corporation has chosencomparatively drier places for storage.and also uses polyethylene-lined bagsfor mOisture-proof packaging.Pests are a real threat to proper seedstorage in India. The rice weevil(Sitophilus oryzae). <strong>the</strong> lesser grainborer (Rhizopertha domtntca). <strong>the</strong>Khapra beetle (Trogoderma granarium)and <strong>the</strong> rust flour beetle (Triboltumcastaneum) infest wheat seed duringstorage. To eliminate pests. fumigationwith aluminum phosphide is carriedout once a month and spraying withpesticides once every two weeks. Whilefumigating <strong>the</strong> seed stock. precaution istaken that moisture content in <strong>the</strong> seedis below 14%. as fumigation at a highermoisture content damages <strong>the</strong> seed.Wheat seed is also invaded bypathogens during storage, <strong>the</strong> mostcommon being Aspergillus. To avoiddamage by fungi. <strong>the</strong> seed is treatedwith fungicides.To avoid moisture penetration through<strong>the</strong> floor. seed bags are stored onwooden pallets after laying a vaporbarrier. Proper ventilation andinsulation are prOVided to lower heat in<strong>the</strong> warehouses. When seed is stored inmetal bins. frequent aeration by meansof a blower is carried out to remove anyheat generated inside <strong>the</strong> seed columns.The government is currently puttinggreater emphasis on creating properstorage facilities to avoid damage toseed during storage. Under thisprogram. bulk seed storage warehouseswill be constructed withoutrefrigeration or dehumidifyingequipment: for storage of breeder andfoundation seed. such equipment isbeing planned.MarketingThe demand for wheat seed in <strong>the</strong>country is growing extremely rapidly.This increase in demand is by nomeans accidental or temporary. Since<strong>the</strong> new varieties of wheat are shorterin duration and relatively insensitive today length. many areas where wheatcultivation was Virtually unknown.West Bengal. Assam. Tripura andMeghalaya in <strong>the</strong> east and Kamatakaand Maharashtra in <strong>the</strong> south. havebecome important wheat-growing areas.The cultivation of wheat in Bangladeshhas also assumed importance.Assessment of demandUntil recently. data on seed demandhas been inadequate. Sometimesdemand has exceeded supply andsometimes seed of certain varieties hasgone unsold. Under <strong>the</strong> National SeedProgram.- <strong>the</strong> government is nowholding seed conferences well before<strong>the</strong> beginning of each new plantingseason. and <strong>the</strong> seed demand andsupply for <strong>the</strong> different states is

301discussed and ascertained; <strong>the</strong> strategyfor seed production for <strong>the</strong> next threeyears is also formulated. In addition toseed conferences, a standing committeeconsisting of <strong>the</strong> chief executives of <strong>the</strong>state and central governments and <strong>the</strong>seed corporations has been constituted,and will monitor <strong>the</strong> performance of <strong>the</strong>different organizations and providegUidelines for future programs.Marketing organizationThe corporation undertakes <strong>the</strong>marketing of seed through publiccooperatives and private-sectoragencies. Through <strong>the</strong> distributorldealer network. <strong>the</strong> corporation has 38distributors and 1,400 dealersfunctioning throughout <strong>the</strong> country.Movement of seed andmaintenance of buffer warehousesThe corporation has always attemptedto move as much wheat seed aspossible to buffer warehouses in <strong>the</strong>different marketing areas before <strong>the</strong>rains. The bulk of <strong>the</strong> movement is byrailroad and <strong>the</strong> balance by roadtransport. By maintaining bufferwarehouses in <strong>the</strong> different marketingareas. <strong>the</strong> corporation is able to reducetransportation costs by transportingearly; <strong>the</strong>re is also <strong>the</strong> benefit of seedreaching end-use areas in time. Propercare is taken dUring <strong>the</strong> movement ofseed. so that it does not take upmoisture and is not attacked by pests.PricingPrices are normally fixed on <strong>the</strong> basis ofcost of production plus a reasonableprofit margin. Normally. <strong>the</strong> cost ofcertified seed is 100% higher than <strong>the</strong>market grain price; <strong>the</strong> producersreceive about 30% of this amount.Seed legislationand seed law enforcementThe Seeds Act, enacted in 1966, dealswith regulations regarding <strong>the</strong> sale ofseed and <strong>the</strong> establishment of suitablelaw enforcement machinery. such as<strong>the</strong> appointment of seed inspectors. <strong>the</strong>certification of central and state seedlaboratories, <strong>the</strong> hiring of seed analysts,<strong>the</strong> appointment of appellate authoritiesand <strong>the</strong> setting of penalties foroffenders. In December 1983, <strong>the</strong>government, through an ordinance.included seeds in <strong>the</strong> EssentialCommodities Act: since <strong>the</strong>n. licencingof all seed agents has becomenecessary. The Act also prOVidesheavier penalties for traders indulgingin <strong>the</strong> sale of spurious seed.Problems in SeedProduction, Storage andMarketingHeavy dependanceon a few varietiesAt present, Sonalika is <strong>the</strong> mostpopular variety in India and covers 70to 90% of <strong>the</strong> wheat area in <strong>the</strong>nor<strong>the</strong>rn and eastern states. Largecoverage under one variety is not ahappy situation. particularly since thisvariety has started shOWingsusceptibility to yellow and brown rusts(stripe and leaf rusts).In order to avert heavy losses due todiseases and pests. diversification withsuitable new varieties is necessary. Theproduction of varieties such as HD2285.HPll02 and HUW37, which couldreplace Sonalika. should be carried outon a comparatively larger scale. Thereis also a need for developing newvarieties with wide adaptabilit:r andsuitability for late SOWing, as well ashigh yield potential.Spread of karnal bunt (Neovossiaindica)The occurrence of kamal bunt(Neovossia indica) disease is no longererratic. For three years, <strong>the</strong> presence of<strong>the</strong> disease has caused <strong>the</strong> rejection ofo<strong>the</strong>rwise good-quality seed producedby seed industries in India.Unfortunately. <strong>the</strong>re are no controlmeasures. and almost all of <strong>the</strong>varieties under seed production areaffected in varying degrees. The

302varieties with high yield potential, suchas HD2009, WL711, UP262 andUP2003, are worst hit. Research needsto be undertaken for <strong>the</strong> developmentof varieties with both good yieldpotential and resistance to karnal bunt,and for <strong>the</strong> identification of fungicidesfor controlling it. The fungicide must beeconomical for application to seed lotsand, hopefully, also for farmer use.Pre-harvest rainThe occurrence of pre-monsoon rains at<strong>the</strong> maturity stage of <strong>the</strong> seed crop in1982 and 1983 rendered largequantities of seed unfit for storage andplanting. The repeated drenching of <strong>the</strong>standing crop resulted in <strong>the</strong> sproutingof kernels on <strong>the</strong> spike. Even <strong>the</strong> seedsaved from <strong>the</strong>se crops lost germinationduring storage because of moisturegain. Therefore, <strong>the</strong>re is a need forinitiating research programs fordeveloping varieties suitable for earlyplanting, to ei<strong>the</strong>r escape pre-monsoonrains or withstand <strong>the</strong>m.Lack of availabilityof breeder seedIf <strong>the</strong> seed program is to succeed, quickmultiplication of newly developedvarieties needs be undertaken before<strong>the</strong>ir identity is lost. It has been noticedthat, because of <strong>the</strong> lack of availabilityof breeder seed, promising varietiesevolved by breeders get lost, evenbefore coming into <strong>the</strong> channel of seedproduction. It is emphasized that <strong>the</strong>breeder must assume responsibility formultiplication of breeder seed of newlydeveloped varieties and proVide it to <strong>the</strong>institutions or agencies responsible for<strong>the</strong> multiplication of foundation andcertified seed. This weak link in <strong>the</strong>seed multiplication program at <strong>the</strong>initial stage has caused great setbacksin <strong>the</strong> cause of <strong>the</strong> Green Revolution.Seed loss throughnatural calamitiesFor stability in production,maintenance of a buffer stock of seed isnecessary to meet <strong>the</strong> challenge of seedloss through natural calamities. such asfloods and droughts. To achieve this, afinancially backed buffer-stockingprogram with adequate storage andrevalidation facilities needs to bedeveloped at <strong>the</strong> national level.

303V. EconomicsWheat in <strong>the</strong> Tropics:Economic and Policy IssuesD. Byerlee, Economics Program, CIMMYT, Islamabad, PakistanAbstractInterest in wheat production in <strong>the</strong> warmer tropics stemsfrom rapidlyincreasing wheat consumption and imports in many tropical countries. Onebillion people in <strong>the</strong> tropical belt (23 ON to 23°5) now consume over 22 milliontons of wheat, 83% of which is imported. In many tropical countries. wheat(usually bread) has become <strong>the</strong> staplefood. especially of urban consumers.Wheat consumption has increased because ofconsumers' rising incomes andinterest in conveniencefoods and a diversified diet. More importantly.governments have encouraged rapid increases in wheat consumption throughfavorable pricing policiesfor bread. including subsidies in many countries.Exporting countries have also promoted wheat consumption through exportpromotion andfood aid. Large-scale investments in capital-intensive milling andbaking industries have entrenched interest in continuing wheat imports.Governments concerned about rising wheat imports should consider policyalternatives as part ofan integratedfood policy analysis that includes consumerprice policiesfor bread and competing staples. cereal import andfood-atdpolicies. removal of incentives to <strong>the</strong> milling industry. promotion of nonwheatfood staples. including compositeflours. and increased domestic agriculturalproduction. Domestic wheat production is only one alternativefor increasingagricultural production. The comparative advantageframework enables anassessment of <strong>the</strong> real returns to <strong>the</strong> country of resources used in wheatproduction versus alternatives. These returns are likely to be highest wherewheat enables an increase in cropping intensity. using available land. labor.water and mechanical services to a fuller capacity. The place of wheat in <strong>the</strong>farming system also needs to be carefully evaluated. with particular attention to<strong>the</strong> needfor timely planting. which is criticalfor successful wheat production in<strong>the</strong> warmer tropics. These economic issues should be addressed at an earlystage in any proposed wheat consumption/production program.Most people in <strong>the</strong> industrializedcountries begin <strong>the</strong>ir day with a cup oftea or coffee. whose major ingredientsoriginated on a small farm or plantationin one of <strong>the</strong> tropical countries. such asBrazil. Ivory Coast or Sri Lanka. At <strong>the</strong>same time. <strong>the</strong> people of <strong>the</strong>se tropicalcountries. especially those in urbanareas. are likely to begin <strong>the</strong>ir day withbread for breakfast. bread made fromwheat grown on <strong>the</strong> fanns of one of <strong>the</strong>industrialized countries. At first sight.this may appear to be a reasonableexchange. but closer examination raisesa number of disturbing questions.Unlike tea or coffee. bread has becomea basic food staple to many people in<strong>the</strong> tropics. proViding a significantproportion of <strong>the</strong>ir calories. not only forbreakfast but also for lunch and.sometimes. dinner as well. Wheatimports by many tropical countries aregrOWing very rapidly. and nowconstitute a significant proportion offoreign exchange expenditures. Whilepeople in <strong>the</strong> tropical countries may notbe "addicted" to bread in <strong>the</strong> same wayas are <strong>the</strong> coffee and tea drinkers. <strong>the</strong>yare increasingly dependent on bread for

304<strong>the</strong>ir daily food supply. The extent ofwheat imports and <strong>the</strong>ir rapid increaseunderlie <strong>the</strong> current interest inproducing wheat for <strong>the</strong> more tropicalenvironments.In this paper. a number of questionswill be addressed. What are <strong>the</strong> majortrends in wheat consumption in <strong>the</strong>tropical belt? How dependent aretropical countries on imported wheat?What are <strong>the</strong> major factors promoting<strong>the</strong>se trends? How can we judge if <strong>the</strong>setrends are in <strong>the</strong> economic interests of<strong>the</strong> country? What policy alternativesare available to governments whoseobjective is to reduce wheat imports?Finally. some of <strong>the</strong> major economicissues will be outlined which must beaddressed in deciding on a domesticwheat production program.Overview of Trends in WheatConsumption and Importsin <strong>the</strong> Tropical BeltIn this paper. <strong>the</strong> conventionaldefinition of <strong>the</strong> tropiCS will be used.Le .• <strong>the</strong> area lying between <strong>the</strong> Tropicof Cancer (23°N) and <strong>the</strong> Tropic ofCapricorn (23°S). To a remarkableextent. <strong>the</strong>se latitudes define <strong>the</strong> areasof <strong>the</strong> world where wheat is notcurrently grown commercially ataltitudes below 1.000 meters (Sudan is<strong>the</strong> only exception). A number ofcountries are dissected by <strong>the</strong>selatitudinal delineations. Countries havebeen excluded from <strong>the</strong> analysis thathave large wheat-producing areas aboveor below <strong>the</strong>se lines (Le.. India. SaudiArabia and China). O<strong>the</strong>r countrieswhich are largely tropical. such asSudan and Burma. have been included.Brazil is a more difficult case; most ofits wheat is now grown south of 23°Slatitude. but future expanSion will takeplace only in <strong>the</strong> more tropical zones.Hence. Brazil has been arbitrarilyincluded as a tropical country. With<strong>the</strong>se definitions <strong>the</strong> tropical beltconsists of <strong>the</strong> follOWing countries:• Africa-all Sub-Saharan Africa exceptLesotho and South Africa• Asia-<strong>the</strong> two Yemens. Sri Lanka andSou<strong>the</strong>ast Asia, from Burma to <strong>the</strong>Pacific countries• Latin America-Guatemala to Braziland Paraguay. including <strong>the</strong>Caribbean countriesThis group of tropical countries has apopulation of about one billion people.roughly equally diVided between Africa.Asia and Latin America. In <strong>the</strong> period1980 to 1982. <strong>the</strong>y produced 4.3 milliontons of wheat annually. most of it inBrazil and Ethiopia. This was only about2% of total wheat production in <strong>the</strong>Third World and less than 1% of worldwheat production. At <strong>the</strong> same time.<strong>the</strong>se countries imported about 20million tons of wheat. about one-third ofall wheat imported by developingcountries. That is. imports suppliedabout 83% of total wheat consumptionin <strong>the</strong> tropical belt (Table 1).From 1980 to 1982. <strong>the</strong>re were 40tropical countries that consumed over100.000 tons of wheat each. Only six of<strong>the</strong>se countries (Ethiopia. Kenya. Sudan.Zimbabwe. Yemen Democratic Republicand Brazil) produced over 100.000 tonsof wheat. mostly in highland areas(Table 1). OutSide of this group. almostall were entirely dependent on importedwheat. By <strong>the</strong> early 19808. nine of <strong>the</strong>secountries were importing close to onemillion tons or more of wheat annually(Nigeria. Indonesia. Sri Lanka.Philippines. Vietnam. Cuba. Venezuela.Peru and Brazil).Per capita consumption of wheat in <strong>the</strong>tropics varies substantially from lessthan 5 kg per year in Thailand to over100 kg per year in Cuba. Per capitaconsumption is much higher in LatinAmerican tropical countries (50 kg/year)

305than in Asia and Africa (about 16kg/year) (Table 2). In <strong>the</strong> Latin Americantropics. wheat now accounts for overone-quarter of staple food caloriescompared to less than 10% for <strong>the</strong> Asianand African group; however.consumption is expanding much morerapidly in <strong>the</strong> latter group. Severalcountries have had an annual growth inper capita consumption of over 10%annually. e.g.. Nigeria. Indonesia andVietnam.For <strong>the</strong> developing world as a whole.wheat consumption has expandedextremely rapidly over <strong>the</strong> last twodecades as wheat and. to some extent.rice have subsituted for coarse grainsand roots and tubers (Table 2). Thissubstitution nas been greatest in <strong>the</strong>Table 1. Summary of annual wheat production and imports in tropical countries, 1~80 to 1982Countries Countriesconsuming producing Perc:entofPopulation over over Production Imports consumptiqllRegion (millions) 100,000 t 100,000 t (million 1) (million 1) importedAfrica 360 15 4 .54 4.3 74Asia 403 11 1 .19 5.7 100Latin America 255 14 1 2.63 10.0 80Total 1018 40 6 4.36 20.0 83Source: FAD data tapesTable 2. Summary of trends in wheat consumption in <strong>the</strong> Third World, 1980-1982Growth of perPer capita Staple food,!/ capita wheatconsumption calories from consumption!!/Region (kg/yr) wheat (0/0) (0/01 year)Tropical Africa 19 6 4.2Tropical Asia 14 6 4.2Tropical Latin America 50 25 1.6Average, tropical countries 25 15 2.8Large mixed cereal economies:India, China, Mexico 65 28 3.2Countries where wheat is <strong>the</strong>staple food 123 71 2.81./ Staple foods include coarse grains, roots and tubers'!l./ 1961 ~5 to 1980-82

306mixed cereal economies of China, Indiaand Mexico and in <strong>the</strong> tropical beltcountries. In <strong>the</strong> first group. however.increased wheat consumption haslargely been met by increasedproduction while. in <strong>the</strong> tropical belt.about 90% of <strong>the</strong> increase inconsumption has been imported. From1970-72 to 1980-82. wheat imports by<strong>the</strong> tropical countries doubled.Factors Influencing WheatConsumption in <strong>the</strong> Tropics:A Cross-Country RegressionAnalysisFigure 1 is a schematic representationof <strong>the</strong> complex of factors influencingwheat consumption in <strong>the</strong> tropics. On<strong>the</strong> right side are <strong>the</strong> factors whichinfluence demand through <strong>the</strong>ir effectson incomes and food preferences. On<strong>the</strong> left side are factors related to supplythat influence <strong>the</strong> quantity and price ofimported wheat relative to local foodstaples. A number of governmentpolicies. such as consumer subsidies,food aid and exchange rates, as wellinvestments in <strong>the</strong> marketing, transportand processing infrastructure. influence<strong>the</strong> demand for and <strong>the</strong> supply ofwheat, particularly through <strong>the</strong>ir effectson consumer prices.Many of <strong>the</strong>se factors are confIrmed bycross-country regression analyses of percapita wheat consumption in 39countries, as shown in Table 3. Thestrongest determinant of per capitawheat consumption in this group ofcountries is per capita income. which isalso closely correlated withurbanization (r =: .83) (<strong>the</strong> highcorrelation between per capita incomeand urbanization does not allow <strong>the</strong>inclusion of both variables in <strong>the</strong>regression analysis). Increasing incomehas a strong effect on wheatconsumption, with an estimated incomeelasticity of 0.6 (I.e.• a 1% increase inincome leads to a 0.6% increase inDomestic FoodSupply and Marketing----------t'-------.....WheatExportingCountriesLocal WheatProcessing-~Industry ~World WheatSupply .......and PricesGrain Transportand Storage ~InfrastructureForeign.......... Exchange-""RatesI.......... Food Aid--.. WheatIImpo,:Consumer Price ofCompeting Food StaplesConsumerIncomesMarketConsumer ....PromotionPreferences and+ DevelopmentUrbanizationConsumer Price tfor Wheat ConsumerProducts ....._- Subsidies.---~-----Domestic Wheat Production and MarketingFigure 1. Major influences on wheat consumption and Imports in <strong>the</strong>Third World

307wheat consumption). However, <strong>the</strong>negative coefficient on <strong>the</strong> quadraticterm for per capita income indicatesthat consumption stabilizes at about 45kg per capita at a per capita income ofabout US$ 3000. i.e.. about <strong>the</strong> incomelevel of Singapore and Venezuela.Wheat consumption is also negativelyrelated to <strong>the</strong> consumer price of bread.A 10% increase in bread prices leads toa decrease in wheat consumption of6%. Food aid also seems to influenceconsumption. As expected. thosecountries which import wheat as foodaid tend to consume more wheat thano<strong>the</strong>r countries at a similar level ofincome. More interesting is <strong>the</strong> positiveeffect of wheat imported as food aid in<strong>the</strong> past. An early objective of food aidwas to develop markets for surpluswheat stocks of <strong>the</strong> major exporters.particularly <strong>the</strong> USA. Finally. wheatconsumption is negatively related todomestic production of cereals which.in this group of countries. does notinclude wheat: however. this effect isnot very strong. An increase in localcereal production of 1% leads to areduction of wheat imports of only0.27%. FollOWing is a more detailedexamination of each of <strong>the</strong>se factorsinfluencing wheat consumption.Incomes and urbanizationWheat consumption in tropicalcountries has initially been establishedin urban areas (3.12.14.15.21). In mostcountries, <strong>the</strong> consumption of wheat inurban areas is at least double that ofrural areas. Figure 2 demonstrates that,as per capita national wheatconsumption increases. <strong>the</strong> differencebetween rural and urban consumptiontends to decline. Likewise wheat,usually as bread. is initially consumedby middle to high-income groups but.with increasing levels of consumption,it becomes more important to lowerincomegroups. In most tropicalcountries. wheat consumption hasincreased with rising incomes fasterthan any o<strong>the</strong>r food staple. Wheat and.to some extent. rice substitute forcoarse grains and roots and tubers,whose consumption often declines withrising incomes (see <strong>the</strong> example ofBrazil in Figure 3).Table 3. Estimated cross-country regression equation for wheat consumption intropical countries, 1979 to 1981WHEATCON = 25.22 +.027 GNP - .462 x 10- 5 GNP2 - .178 PRBREAD -(,0053) * * (,118 x 10-5)** (.052)**.058 DCP +.861 FA +.091 CUMFA(,020)** (.414)* (,036)**WHEATCON = Wheat consumption per capita (kg/person, 1979-81 average)GNP = Gross national product per capita (1980 US$)OCP = Domestic cereal production per capita (kg/person, 1979-81 average)FA = Wheat imports as food aid per capita (kg/person, 1979-81 average)CUMFA = Historically cumulative food-aid wheat imports (kg/person, 1955-75)PRBREAD = Price of bread, 1979-81 (US cents/kg)n = 39, R2 = 0.81Standard error of estimates are given in brackets*, ** Significant at <strong>the</strong> 5 0 /0 and 10/0 levels, respectively

308765Ratio of wheat 4consumptionin urban areasto rural areas 3e21w ~ 30 40National per capita wheat consumption (kg/year)Figures 2. Relationship between <strong>the</strong> ratio of urban to rural per capitawbeat cQQsumption and national per capita wheat consumption int:ropical countries40U)35Cl)-I-.0 30ca c;25~ 0 20 .........0.....I:Cl)c;I-.Cl)ll.15105\\,Cassava.,".......-.- .........- ......-.............. ~...............................••...._..-.-...... ...........···Wheat Products----~ •••••• ......_-~-__ Maize..... -...._----------.._~-~--1000 2000 3000 4000 5000Per Capita Income (cruzeiros)Figure 3. Rice. cassava. wheat and maize as contributors to apparent percapita energy consumption according to income class. nor<strong>the</strong>ast Brazil.1975-76Source: T.T. Poleman. 1981. Quantifying <strong>the</strong> nutrition situation indeveloping countries. Food Research Institute Studies 1:1-58.

309These changing consumption patternsreflect <strong>the</strong> preference for bread as aconvenience food in urban areas. Lesstime and cooking fuel is also requiredfor <strong>the</strong> consumption of wheat-basedfoods (10,12,17).On <strong>the</strong> supply side, urbanization alsofavors wheat consumption based onimports. With plentiful supplies ofwheat in world markets, laggingdomestic production of staple foods andpoor infrastructure for transporting andmarketing domestic food supplies inurban areas, <strong>the</strong>re has been a naturaltendency to import wheat to feed urbanconsumers, especially in countrieswhere large cities are located on <strong>the</strong>coast.Bread pricesFood pricing policy in many tropicalcountries favors low bread pricesrelative to competing staples. Aboutone-quarter of <strong>the</strong> tropical countries forwhich we have price data subsidizedbread prices in <strong>the</strong> 1970s. Sri Lanka,Sudan, Ivory Coast, Ecuador and Brazilare all countries where bread susbsidieshave led to rapid increases in wheatconsumption (3,12). Many o<strong>the</strong>rcountries have imported wheat dutyfreeand at a significantly overvaluedexchange rate. If bread prices areconverted at <strong>the</strong> black marketexchange rate, nearly half of <strong>the</strong>tropical countries, expecially in Africaand Latin America, had declining realbread prices in <strong>the</strong> 1970s (3). In Africa,this largely reflects exchange ratepolicy while, in Latin America, acombination of overvalued exchangerates and increasing bread subsidies ina number of countries have led todeclining real prices.The result of <strong>the</strong>se policies is that, inmany countries, wheat flour and breadare cheap relative to locally producedfood staples, such as rice, maize andcassava. In several countries, e.g.,Nigeria, Ivory Coast, Sudan, Brazil andEcuador, wheat flour based on importedwheat was cheaper than locallyproduced coarse grains, such as maizeor sorghum. Food pricing policy in<strong>the</strong>se countries may explain half ormore of <strong>the</strong> growth of wheatconsumption. There are. of course,important exceptions. Sou<strong>the</strong>ast Asiancountries such as Thailand, Burma and<strong>the</strong> Philippines maintain high breadprices. A number of countries, such asColombia, Senegal and Sri Lanka, havephased out bread subsidies and percapita wheat consumption has fallen.Food aidAlthough food aid has declined inimportance relative to commercial foodimports, it has been and remainsimportant to a number of tropicalcountries. Over 80% of food aid isprovided as wheat, and this proportionis only slightly lower for <strong>the</strong> tropicalcountries. Food aid has encouragedwheat consumption in <strong>the</strong>se countriesby reducing <strong>the</strong> price of wheatproducts, establishing a milling andbaking industry and developingconsumer tastes and preferences forwheat (9,19). The development ofmarkets for commercial wheat is stillan important objective of food aid andour cross-country regression analysisindicates that it has been relativelysuccessful. Sudan, Sri Lanka, Somaliaand Mauritania are examples of tropicalcountries that receive substantialamounts of food aid and have relativelyhigh per capita consumption of wheat.Government PolicyAlternatives with Respect toWheat in <strong>the</strong> TropicsInterest in wheat production in <strong>the</strong>tropical countries reflects a desire topromote greater self-sufficiency in food.Many governments have seen <strong>the</strong> rapid

310increase in foreign exchangeexpenditures for wheat imports as anarea where foreign exchange can besaved and. at <strong>the</strong> same time. domesticagricultural production be promoted.Food security is also sometimes animportant objective. as governmentsseek to reduce exposure to fluctuationsin world market prices. However,except for 1974-75. world market pricesfor wheat have been relatively stableover a long period.The reasons for increasing wheatconsumption are complex and need tobe analyzed within <strong>the</strong> specific foodpolicy environment in each country.Wheat consumption is bound to increasein most countries. As consumer incomesincrease. <strong>the</strong>re is a natural tendency todiversify diets. However. in many cases.<strong>the</strong> policies of governments, food-aiddonors and exporting countries havereinforced and greatly accelerated thistrend. This comes about as a result offood-pricing policies that favor bread andby an implicit policy of supplying urbanconsumers from food imports (in mostcases, wheat). At <strong>the</strong> same time, policieshave encouraged investments inmarketing. storage and processing forimported wheat. These investments actlike a "wheat trap" because, onceestablished. it is very difficult to reverse<strong>the</strong> trend toward importing wheat (2.5).The milling and baking industry hasgrown extremely rapidly over <strong>the</strong> lastdecade in tropical countries that do notproduce wheat (for example, between1975 and 1980 wheat flour productionincreased at an annual rate of 23.4% inBrazil. 7.6% in Indonesia. 11.1 % inKenya. 11.7% in Cuba, 14.4% inGuatemala and 7.2% in <strong>the</strong> Philippines)(5). This is a highly wheat-specificindustry that cannot be converted into<strong>the</strong> processing of locally producedstaples. even if <strong>the</strong>y are in surplussupply. It is ironical that, in <strong>the</strong> last fewyears. <strong>the</strong> largest flour mills in <strong>the</strong> worldhave been established in <strong>the</strong> nonwheatproducingcountries of Indonesia, SriLanka and Nigeria. Investment andtrade policies (such as high tariffs onwheat flour imports) have encouragedrapid expansion of flour milling in manytropical countries (5).With this background, and given anobjective of reducing wheat imports, anumber of policy alternatives areavailable for tropical countries.Food pricing pollcyUndoubtedly <strong>the</strong> quickest way to reducewheat imports is to raise consumerprices for wheat products. There isample evidence that wheat consumptionis quite sensitive to prices. Removal ofconsumer subsidies and, in some cases.imposing a tariff on wheat imports tocompensate for overvalued exchangerates are <strong>the</strong> major instruments foradjusting bread prices. The objectiveshould be to restore incentives toconsume domestically produced foodstaples. It has been shown elsewherethat, based on world prices, <strong>the</strong> ratio of<strong>the</strong> price of wheat flour to rice andmaize should be about 0.7 to 1.0 and1.6, respectively (3). At <strong>the</strong>se prices.bread will be considerably moreexpensive than rice and maize.The political sensitivity of bread pricesis recognized. However, it should alsobe recognized that <strong>the</strong> longer such adecision is delayed. <strong>the</strong> more difficult itis to correct <strong>the</strong> imbalance. Thailand isa country which has maintained highbread prices and, as a result. per capitaconsumption is low (4 kg/year); <strong>the</strong>re itis still relatively easy to regulate breadprices. In <strong>the</strong> Sudan and Ecuador,bread subsidies have promoted percapita bread consumption of over 80kg/year in <strong>the</strong> capital cities. It wouldnow be very difficult to manipulatebread prices in <strong>the</strong>se countries. sincebread is such an important food stapleto a politically powerful section of <strong>the</strong>population.

311Finally. it should be clarified that. inmany tropical countries. low breadprices have produced few benefits to<strong>the</strong> poor. Ra<strong>the</strong>r. <strong>the</strong> middle and upperincome groups. which are <strong>the</strong> mainbread consumers. have captured <strong>the</strong>benefit of <strong>the</strong>se policies. while <strong>the</strong>farmer. especially <strong>the</strong> small farmer whoproduces local staples such as maize.has been <strong>the</strong> main loser (5.14.16).Policies toward <strong>the</strong>wheat processing sectorAn integrated wheat strategy shouldcarefully rationalize investments inwheat processing. especially large-scalecapital and foreign exchange-intensivemilling and baking plants. Littlejustification is found for <strong>the</strong>establishment of a milling industry.given <strong>the</strong> need to efficiently use scarcecapital and promote employment.Removal of tariff protection on flourimports should effectively arrest <strong>the</strong>growth of this industry. until such timeas local wheat production might beestablished. Importing wheat as flourmaintains much greater flexibility infuture food-policy decisions and alsoreduces <strong>the</strong> power of one of <strong>the</strong>strongest voices. that of <strong>the</strong> millers. infood-import policy. Finally. mosttropical countries produce white flour.milled at an extraction rate of 70 to75%. Legally mandated higherextraction rates (e.g.. in Sudan). whichproduce off-white flour and breads.would allow saVings in wheat imports.Import policy and food aidWe have noted that cereal imports by<strong>the</strong> tropical countries have emphasizedwheat and. to a lesser extent. rice.Maize imports have largely beendestined for feeding livestock. Yet maizeis usually <strong>the</strong> cheapest cereal in worldmarkets. and is a staple food of mosttropical countries. especially for <strong>the</strong>poor. With consumer prices that reflectimport prices. maize has considerablepotential as a food import. Somedifficulties arise because most countriesconsume white maize. while yellowmaize dominates world markets. Yet.with <strong>the</strong> favorable price incentives andexport promotion seen for wheat. <strong>the</strong>reshould be no reason why maize cannotplay an important role in world foodtrade. Donor agencies could help bytargeting food aid to countries inaccordance with <strong>the</strong>ir staple food. Fortropical countries. thiS would meanmore emphasis on food aid in rice andcoarse grains.Promotion of conveniencefoods based on local food staplesBread-making technology has largelybeen imported from <strong>the</strong> industrializedcountries. At <strong>the</strong> same time, untilrecently. little research has beenconducted on <strong>the</strong> preparation of localfoods to meet <strong>the</strong> preferences andconvenience needs of urban consumers.There has been considerable researchon composite flours which mix wheatflour with maize. millet or cassava flourfor bread making (11,17). This appearsto be technically feasible. but <strong>the</strong>greatest obstacle in most countries isthat pricing policy favors wheat flourand prOVides no incentives to usemixtures.Meanwhile. private and public agenciesof wheat-exporting countries haveconducted Vigorous and apparentlysuccessful market-promotion programsfor wheat products. Government policyshould convert <strong>the</strong>se efforts into <strong>the</strong>national interest. perhaps by requiringthat <strong>the</strong>se export interest groupsconduct research and promotion thatbalances wheat with local food staples.Increasing domesticagricultural productionIn an integrated wheat strategy.increased agricultural production mustreceive high priority. Producing wheatdomestically is only one option.Alternatives include 1) promotion of

312export crops which will generateforeign exchange for importing foodand 2) promoting <strong>the</strong> production ofo<strong>the</strong>r food staples to substitute forwheat imports.The comparative advantage frameworkis a useful way of assessing <strong>the</strong>economics of each of <strong>the</strong>se alternatives.As an example. it can be assumed thatone hectare of wheat yields 2 tons ofgrain. If imported wheat costs $200/t in<strong>the</strong> capital city. and it costs $20/t totransport domestically produced wheatto <strong>the</strong> capital. <strong>the</strong>n <strong>the</strong> value of onehectare of domestic wheat would beequal to 2 x (200-20) = $360/ha. Localwheat production will require importedfertilizer and o<strong>the</strong>r inputs; if <strong>the</strong>se cost$100/ha. <strong>the</strong> net gain would be$260/ha. However. <strong>the</strong>se same domesticresources of labor and land might beinvested in export crops such as cotton.If one hectare of cotton yields 0.8 tonsof lint per hectare at an export price of$1.000/t. and requires $200/ha ofimported inputs. net gains would be$600/ha. sufficient to import over 3tons of wheat. In this case. cottonwould have <strong>the</strong> comparative advantage.However. if wheat yields 4 Uha (for <strong>the</strong>same inputs). wheat would have <strong>the</strong>comparative advantage. All of <strong>the</strong>secalculations employ <strong>the</strong> world priceeqUivalent of <strong>the</strong> commodity ra<strong>the</strong>rthan <strong>the</strong> domestic price. since <strong>the</strong> worldprice reflects <strong>the</strong> real cost to <strong>the</strong>country.The value of <strong>the</strong> comparative advantageanalysis is that it demands a look at <strong>the</strong>alternatives. The above example showsthat. in focusing on wheat alone. itmight be concluded that <strong>the</strong>re is a netgain from wheat production. However.with <strong>the</strong> country's welfare ra<strong>the</strong>r thanwheat production as <strong>the</strong> objective. <strong>the</strong>alternative uses of <strong>the</strong> scarce domesticresources available and <strong>the</strong>ircontribution to national income mustbe taken into account.EcononUcIssuesinEstablishing a DomesticWheat IndustryThe economics of domestic wheatproduction must be examined at twolevels. <strong>the</strong> comparative advantage orprofitability to <strong>the</strong> country. and <strong>the</strong>profitability to <strong>the</strong> farmer. At <strong>the</strong> sametime. <strong>the</strong>re will be a number ofmarketing and milling issues to beresolved in establishing a new industry.Some of <strong>the</strong>se issues will be mentionedonly briefly. since <strong>the</strong>y will bediscussed in more detail in <strong>the</strong> papersthat follow.Economic profitabilityFour issues will be dealt with thatdetermine economic profitability to <strong>the</strong>country. First. <strong>the</strong> foreign exchangesaVings generated by domestic wheatproduction will be critically dependenton <strong>the</strong> technology employed. Highlymechanized wheat production schemeswhich have been tried in severalAfrican countries. with even harvestingbeing mechanized. are expensive froma foreign-exchange point of view andare unlikely to be effiCient in a lowwageeconomy (6.13.17). One-third ormore of <strong>the</strong> foreign exchange saved isspent on imported inputs andmachinery. Investment in large-scaleirrigation schemes is also extremelycostly (over US$ 10.000/ha) andforeign-exchange intensive. It isunlikely that it will pay to developlarge-scale irrigation schemes in <strong>the</strong>tropiCS. specifically for wheatproduction (1.2.20). Even small-scaleirrigation schemes for wheat have failedto generate satisfactory returns (8).Second. areas with high yield potentialand irrigation or adequate moisture willalso usually have high-value alternativecrops such as rice. cotton or o<strong>the</strong>r cashcrops that are adapted to tropical areas.While it seems logical to emphasizeareas where wheat gives <strong>the</strong> highestyields. it may well be that wheat'sgreatest comparative advantage will be

313in areas where wheat yields arerelatively low, but where <strong>the</strong>re are fewalternatives. (The rapid expansion ofwheat in Bangladesh on residualmoisture after rice illustrates thispoint). A similar issue arises in thosetropical countries with limited highlandareas suitable for wheat, but where<strong>the</strong>re are a number of alternative landuses with high returns (4).Third, <strong>the</strong> greatest potential for wheatin <strong>the</strong> tropics is likely to be as a secondor third crop after a main crop, such asrice or cotton. An early variety of wheatthat fills a gap in <strong>the</strong> cropping calendarand enables increased croppingintensity may also allow more efficientuse of farmers' labor, land and waterresources.Fourth, <strong>the</strong> economic profitability ofwheat in many countries is criticallydependent on transportation costs from<strong>the</strong> producing region to <strong>the</strong>consumption center. For example, in1979, it was estimated that transportcosts for wheat from <strong>the</strong> north ofNigeria to Lagos were about usa 65/tonat <strong>the</strong> real exchange rate. Assuming aelF price of wheat of about $200/t, <strong>the</strong>cost of imported wheat in <strong>the</strong> northwould have been about $265/ton(200+65), while <strong>the</strong> real·value ofdomestically produced wheat at Lagoswould be about $135/ton (200-65), oronly half of its value in <strong>the</strong> north. Given<strong>the</strong>se wide margins, it may have beenprofitable to produce wheat for localconsumption in <strong>the</strong> north, but quiteunprofitable to substitute it for wheatimports in Lagos. In some countries,this issue is fur<strong>the</strong>r complicated by <strong>the</strong>location of flour mills on <strong>the</strong> coast forimported wheat. If wheat is to beproduced in <strong>the</strong> interior for localconsumption, <strong>the</strong>re may be a need toestablish small-scale wheat mills in <strong>the</strong>prodUcing area (6).Farmer compatibUityThe key issues in <strong>the</strong> acceptance ofwheat production by farmers areprofitability, risk and compatibility with<strong>the</strong>ir current farming systems. The lasttwo are related: one of <strong>the</strong> most criticaldeterminants of wheat yields in <strong>the</strong>tropics will be timely planting. Hence, itis essential to examine <strong>the</strong> currentfarming system and <strong>the</strong> extent to which<strong>the</strong> farming calender and availableresources will allow planting during <strong>the</strong>optimal period. Expected yields underfarmers' conditions must be carefullyevaluated through extensive fieldtesting Within <strong>the</strong> cropping system andresources available to farmers. Severalwheat development projects have beenwildly optimistic about expected farmeryields. Even where wheat fits well into<strong>the</strong> cropping system, <strong>the</strong>re is always alearning curve for <strong>the</strong> adoption of a newcrop.Profitability depends on both <strong>the</strong> inputand output prices facing farmers. It isnot difficult to make wheat productionprofitable. The phenomenal expanSionof wheat production from a very smallbase in Saudi Arabia reflects highsubsidies on water, machinery andfertilizer, and <strong>the</strong> highest producerprice in <strong>the</strong> world, over usa 1,000/ton.The issue is to find that combination ofprice incentives which promotes anefficient industry. The basic gUidelinesfor setting a domestic wheat price willbe <strong>the</strong> price of imported wheat(adjusted for exchange rateovervaluation) and <strong>the</strong> price ofcompeting agricultural products.Once a domestic producer price hasbeen set, a mechanism will be neededto ensure that this price is actuallyreceived by farmers. In most countries,wheat millers enjoy a degree ofmonopoly power. They also prefer <strong>the</strong>status quo of using only importedwheat, whose supply and quality ispredictable and which can be handledin volume. In <strong>the</strong> initial stages, <strong>the</strong>government food procurement agencywill probably have to act as a wheatbuyer, since it will be in a much betterposition to negotiate with <strong>the</strong> millers.

314ConclusionsWheat consumption will undoubtedlycontinue to expand in tropicalcountries. However, if governmentspursue policies that remove incentivesto consume wheat, this expansion willbe relatively slow and will reflect anatural tendency by consumers todiversify diets as <strong>the</strong>ir incomesincrease.Governments that wish to reducedependence on imported wheat shouldconsider domestic production of wheatas only one among a set of policyalternatives. A decision to producewheat domestically should be taken in<strong>the</strong> context of <strong>the</strong> wider food policyenvironment, and after a carefulassessment of <strong>the</strong> comparativeadvantage of wheat. It is impossible tomake general statements about <strong>the</strong>economics of wheat production in <strong>the</strong>tropics. However, it appears that <strong>the</strong>best prospects for efficient wheatproduction in <strong>the</strong> warmer tropics arewhere wheat will enable two or eventhree crops a year, where moisturelimits production of o<strong>the</strong>r crops orwhere small-scale irrigation is available,and where wheat can be producedusing <strong>the</strong> labor and machinery alreadyutilized by farmers in <strong>the</strong> production ofo<strong>the</strong>r crops.These economic issues should beanalyzed at an early stage, before <strong>the</strong>commitment of a large amount ofresources to a domestic wheat researchand production program.AcknowledgementsThe author wishes to thank EdithHesse de Polanco for valuableassistance, in data analysis for thispaper.References1. Agricultural Extension andResearch Liaison Service. 1978.Report on wheat production andmarketing in Nigeria. AhmaduBello University, Nigeria.2. Andrae, G., and B. Beckman. 1983.The wheat trap: Bread andunderdevelopment in Nigeria.University of Stockholm, Sweden.(Unpublished report.)3. Byerlee, D. 1983. The increasingrole of wheat consumption andimports in <strong>the</strong> developing world.Economics Paper 83/5. CIMMYT,Mexico.4. Byerlee, D. Comparative advantageand policy incentives for wheat inEcuador. Economics paper.CIMMYT, Mexico. (In press.)5. Byerlee, D. 1984. The politicaleconomy of Third World foodimports: The case of wheat.CIMMYT, Mexico. (Unpublishedpaper.)6. Byerlee, D., and G. Varughese.1981. The potential for commercialwheat production in Senegal: Someissues. Report submitted to <strong>the</strong>Senegal Institute of AgriculturalResearch (lSRA).7. Carbonell, W.J., and H. Rothman.1977. An implicit food policy:Wheat consumption changes inVenezuela. Food Policy 2(4):305317.8. De Rafols, W. 1982. Action Ble-DireProject: Economic analysis update.USAID, Mali. (Draft paper.)9. Dudley, L., and R.J. Sandilands.1975. The side effects of foreignaid: The case of PL480 wheat inColombia. Economic Developmentand Cultural Change 23(2):325-336

31510. FAO. 1982. The bread economy.Rome. Italy. (Unpublished paper.)11. FAO. 1982. Action program oncomposite flours. Draft proposal.Rome. Italy.12. Franklin. D.• M.P. Demousin andM.W. Harrell. 1982. Consumptioneffects of agricultural policies:Bread prices in <strong>the</strong> Sudan. SigmaOne Corporation, Raleigh. NorthCarolina. USA.13. Freeman. L. 1982. CIDA. wheatand rural development in Tanzania.Canadian Journal of AfricanStudies 16(3):479-504.14. Gray. W. 1982. Food consumptionparameters for Brazil and <strong>the</strong>irapplication to food policy. ResearchReport 32. IFPRI, Washington.D.C.. USA.15. Kilby. P. 1963-64. Patterns of breadconsumption in Nigeria. FoodResearch Institute Studies 4:3-18.18. Salih. S.S. 1983. The impacts ofgovernment agricultural policies ondomestic wheat production in <strong>the</strong>Sudan. Unpublished PhD Thesis.Duke University, Raleigh. NorthCarolina. USA.19. Valderrama. M. 1982. Effecto de lasexportaciones norteamericanas detrigo en Bolivia. Peru. Ecuador yColombia. Estudios RuralesLatinoamericanos 2(2): 173-198.20. Wallace. T. 1981. The Kano RiverProject, Nigeria: The impact ofanirrigation scheme on productivityand welfare. In Rural Developmentin Tropical Africa. J. Heyer. P.Roberts and G. Williams. eds.St. Martin's Press. New York, USA.. Pp. 281-305.21. Youngs. A.J. 1972. Wheat flour andbread consumption in West Africa:A review with special reference toGhana. Tropical Science114(3):235-244.16. Magiera. S.L. 1981. The role ofwheat in <strong>the</strong> Indonesian foodsector. Foreign AgriculturalEconomics Report 170. USDA.Washington. D.C.• USA.17. Mwangi, W.M. 1982. Subsaharan .Africa wheat imports: Significance.extent. causes and futureimplications. Draft report. FAO.Rome. Italy.

316Wheat in Chiang Rai, Thailand:A Preliminary Look at Comparative AdvantageL.W. Harrington, Economics Program, CIMMYT, and S. Sat-thaporn,Ministry of Agriculture and Cooperatives, Bangkok, ThailandAbstractA preliminary assessment is made of<strong>the</strong> comparative advantage ofwheatversus alternativesfor two production domains in <strong>the</strong> Chiang Rai province ofThailand, <strong>the</strong> rainfed uplands and <strong>the</strong> bunded lowlands without dry-seasonwater. The assessment is preliminary, because wheat technology is not yet wellspecified. Using technology and cost assumptions thatfavor wheat, resultsindicate that wheat does not have a comparative advantage on rainfed uplands;for saving or earningforeign exchange, more resources are usedfor wheatproduction thanfor that ofmaize or mungbean. However, wheat may have acomparative advantage in certain lowland areas, if agronomic problems andcropping-systems conflicts can be resolved.Thailand. like many o<strong>the</strong>r developing.countries in more tropical environments.is importing and consuming large andincreasing quantities of wheat.Currently. wheat imports total about200.000 tons per year. with a currentvalue of about USS 40 million: <strong>the</strong>y aresaid to be increasing on <strong>the</strong> order of10% per year (3). As a consequence.Thai researchers. in cooperation withCIMMYT, have undertaken <strong>the</strong> task ofdeveloping technology for local wheatproduction. The purpose of this paper isto add an economic dimension to <strong>the</strong>irwork by offering a preliminaryassessment of <strong>the</strong> comparativeadvantage of wheat for one province innor<strong>the</strong>rn Thailand. It is restricted to <strong>the</strong>production of wheat for importsubstitution: production for homeconsumption is not addressed.Wheat Production DomainsAny study of comparative advantage isconducted for specified production andconsumption locations. This study setsconsumption and production locations atBangkok and Chiang Rat province.respectively. Chiang Rat was chosenbecause of its relatively favorableagroclimatic and economiccircumstances. including such factors asa relatively long cool season. relativelyabundant dry-season rainfall (1) andrelatively large areas of idle land in <strong>the</strong>cool. dry season. This province is farfrom homogeneous and. as part of <strong>the</strong>study. several wheat-productiondomains were identified. Each of <strong>the</strong>m isreasonably homogeneous with respect topossibilities for wheat production: <strong>the</strong>yinclude rainfed uplands. lowlands withinadequate dry-season water and o<strong>the</strong>rdomains.Ralnfed uplandsThis domain is comprised of croplandbelow 600 meters altitude that is notbunded or irrigated. Maize. <strong>the</strong> majorrainy-season crop. is harvested by earlyto mid-September. leaVing more than amonth before <strong>the</strong> wheat-planting season.In much of this domain. wheat can begrown after maize, but would competewith o<strong>the</strong>r second crops (mungbean.peanuts and a second maize crop) forland and o<strong>the</strong>r resources. This domain ischaracterized by relatively light-texturedsoils and covers some 56.000 hectares.approximately 17% of Chiang Ratcropland.

317Lowlands withinadequate dry-season waterThis domain is comprised of bundedcropland, planted to flooded rice in <strong>the</strong>rainy season. but left idle in <strong>the</strong> dryseason because of insufficient or poorlymanaged dry-season water. Water forrainy-season flooded rice is mainly fromrainfall, with some also coming fromtraditional irrigation systems. Watercontrol (<strong>the</strong> ability to flood and drain atwill) is poor. because water movesdirectly from field to field, ra<strong>the</strong>r thanthrough subcanals. Wheat would haveto be grown, for <strong>the</strong> most part, withresidual moisture. Irrigation water. evenfor stand establishment, wouldcommonly not be available. Wheatwould not compete for land with o<strong>the</strong>rsecond crops, as none are generallygrown. However, <strong>the</strong> wheat-plantingseason conflicts with <strong>the</strong> rice-harvestperiod (late November to mid-January).This domain is characterized by heavyclay soils and covers approximately200,000 hectares or about 60% ofChiang Rai cropland.O<strong>the</strong>r domainsTwo o<strong>the</strong>r domains have been identified,but are assigned a lower priority. One issimilar to <strong>the</strong> lowland domain describedabove, but is fully irrigated in <strong>the</strong> dryseason. permitting farmers to plant asecond crop of flooded rice. The o<strong>the</strong>rdomain is also lowland. with relativelylight-textured soils on river floodplains.Farmers use this land with pumpirrigation in <strong>the</strong> cool season for highvaluecrops, such as tobacco and garlic.Wheat Production TechnologyWheat production technology for moretropical environments is not yet wellspecified. Numerous issues in cropimprovement and management remainunresolved (7). Consequently, <strong>the</strong>present assessment of <strong>the</strong> comparativeadvantage of wheat is preliminary. as is<strong>the</strong> specification of wheat productiontechnology itself.For <strong>the</strong> purposes of this study, "bestbet"wheat production practices wereidentified in cooperation with technicalscientists. Rainfed upland wheatproduction practices were specified as:• Land preparation by four-wheeltractor (two passes);• Manual planting in rows with a seedrate of 125 kg/ha of INIA66;• Fertilizer dosage of 30 kg/ha nitrogenand 38 kglha phosphorus, appliedbasally, and• Manual weeding and harvesting, andmechanized threshing.These practices result in a yield ofabout 1.000 kg of wheat per hectare.Lowland wheat production practicesand yields were specified as similar tothose described above, except that landpreparation is by rotortiller. A sharplyreduced labor input was also specifiedfor weeding; wheat after flooded ricefaces fewer weed problems than doeswheat after maize.If anything, <strong>the</strong> specified practices tendto consistently underestimate wheatproduction costs. For example,adequate land preparation for rainfedupland wheat after maize will likelyrequire more than two tractor passes;similarly, pre-irrigation and strawmulching may be needed for acceptablelowland wheat yields. These associatedcosts are ignored. More important, <strong>the</strong>specified lowland wheat technologyassumes that <strong>the</strong> conflict between riceharvest and wheat planting seasons canbe resolved at no fur<strong>the</strong>r costs to <strong>the</strong>farmer.Policies Affecting<strong>the</strong> Profitability of WheatProductionThailand's economic and agriculturalpolicies increasingly tend to favor freetrade (3). Most agricultural inputs are

318imported with negligible tariffs or taxes.Similarly. export taxes on suchproducts as maize and mungbean arevery low. Reserve requirements andpremiums which serve as taxes on riceexports have historically been quitehigh and. by depressing <strong>the</strong> price of <strong>the</strong>food staple. have kept wage ratesartificially low (5). Currently. however.rice export taxes are low and <strong>the</strong> effecton wages seems neglible (16).Fur<strong>the</strong>rmore. price distortions. due toan over or undervalued currency. areVirtually nonexistent.The major policy effect on <strong>the</strong>profitability of local wheat production isa tariff of US$ 43.60 per ton on wheatimports (3. United Flour Mills. personalcommunication). This serves to makewheat in Thailand artificially expensive.Currently. wheat imports costapproximately US$ 249/ton (CIFBangkok flour mill). or US$ 206/tonwithout <strong>the</strong> tariff. Adjusting for internaltransport charges. this converts to afarm-level market price (tariff included)of US$ 227/ton or B5.2/kg or a realprice (tariff excluded) of US$ 190/ton orB4.4/kg (US$ 1 = 823).It should be noted that <strong>the</strong> real expenseincurred in importing wheat is bestestimated by <strong>the</strong> tariff-free price. Thetariff itself does not represent a cost to<strong>the</strong> Thai economy. but ra<strong>the</strong>r a transferfrom one sector (millers and wheatconsumers) to ano<strong>the</strong>r. <strong>the</strong> government.Proceeds from <strong>the</strong> tariff are available foreducation. irrigation infrastructure.national defense. etc.It is also worth noting that privatesectorsources suggest that a reasonablewheat price might be closer toUS$ 165/ton. lower than <strong>the</strong> real price.This will be referred to as <strong>the</strong> privatesector-suggested price.Private and Social Profitabilityof Wheat ProductionThe private and social profitability ofwheat production was calculated forboth rainfed upland and lowlandenvironments. Full specification oftechnical coefficients. farm-level marketprices. real prices (adjusted tocompensate for policy-induced pricedistortions) and enterprise budgets maybe seen in a longer version of this paper(4). Estimates of net private and socialprofitability of wheat and alternatives.by domain. may be seen in Table 1.Also to be found are estimates of breakevenyields (yields needed to repayproduction costs). using farm-levelmarket prices. real. undistorted pricesand private sector-suggested prices. Itshould be noted that <strong>the</strong>re is atendency to underestimate costs andoverestimate wheat profits; some wheatproduction costs are underestimated asnoted earlier. and only internaltransport charges (not full marketingmargins) are used to calculate farmlevelwheat prices. Full marketingmargins are used for maize andmungbean.The preliminary assessment of <strong>the</strong>comparative advantage of wheatindicates that. even under favorableassumptions as to costs and yields. itwould seem that wheat cannot competewith maize or mungbean on rainfedupland areas in Chiang Rai. unless <strong>the</strong>wheat import tariff is maintained.When real prices are used. wheatappears to demonstrate stronglynegative social profits.On lowlands. however. wheat appearsto be highly profitable. regardless ofwhe<strong>the</strong>r market or real prices are used.Fur<strong>the</strong>r research will be needed.particularly for <strong>the</strong> lowland areas. tobetter specify wheat productiontechnology before a more detailedanalysis of costs and returns can bemade. Particular attention needs to begiven to resolVing <strong>the</strong> conflict betweenwheat planting and rice harvest dates.

319Table 1. Private and social profitability of wheat and two alternatives by domain, ThailandVariableNet private profits~./Yield (kg/ha)Price ($Iton)Total revenue ($/ha)Tradeable costs ($/ha)!2..1Nontradeable costs ($/h~)£.1Returns to land ($/ha)~/Net social protifs~jPrice ($Iton)Total revenue ($/ha)Tradeable costs ($/ha) ~INontradeab~losts ($/ha)£.lLand ($/ha)-!-Net social profitability ($/ha)9'/Lowlands(inadequatedry-seasonRainfed uplandswater)Wheat Maize Mungbean Wheat1000 1500 450 1000227 111 326 227227 167 147 22766 21 11 52111 104 86 9650 42 50 79190 117 333 190190 176 150 19064 20 10 51110 103 86 9550 50 50 0-34 3 4 44Breakeven yieldsb./At farm-level market price,with tariff (kg/ha)At farm-level real price,without tariff (kg/ha)At mill-suggested price (kg/ha)10301179135815771479450438652768885Research cost ratio-V1.270.980.970.68a I Based on unadjusted farm-Ievel--market prices~I Costs of inputs that are imported or exported and represent a foreign exchange costc I Domestic resources, without a foreign exchange costdI Calculated as a residuali./ Based on real prices adjusted for policy-induced price distortions, e.g., wheat tariffil Estimated from <strong>the</strong> residual, calculated under net private profits for <strong>the</strong> bestalternative use of landgj A positive number indicates comparative advantage for that crop0.1 The minimum yield required to repay costsiI A ratio of less than 1 indicates comparative advantage

320•References1. Asian Institute of Technology.1983. Rainfall-erosivity study of <strong>the</strong>nor<strong>the</strong>rn region of Thailand.Bangkok. Thailand.2. Far East Economic Review. Variousissues.3. Foreign Agricultural Service. 1984.Thailand: Annual AgriculturalSituation and Policy Report.Bangkok. Thailand.4. Harrington. L.• and S. Sat-thaporn.Wheat in Chiang Rai. Thailand: Apreliminary look at comparativeadvantage. Draft. working paper.5. International Bank forReconstruction and Development.1980. Thailand: Case study ofagricultural input and outputpricing. Staff Working Paper 385.6. Office of Agricultural Economics.Ministry of Agriculture andCooperatives. Bangkok. Thailand.7. Saunders. D.A. Agronomicmanagement issues for wheatproduction in more tropicalenvironments of Sou<strong>the</strong>ast Asia.(These proceedings.)

The Local-Use Approach to <strong>the</strong> Introductionof Wheat in a Nonproducing Country: ThailandJ.G. Connell, Local Utilization Program, Sou<strong>the</strong>ast Asia RegionalWheat Program, CIMMYT, Bangkok, ThailandAbstractWheat in <strong>the</strong> more tropical countries has a previously unrecognized potentialforincreasing basicfood production in <strong>the</strong> off-season. In nor<strong>the</strong>rn Thailand, <strong>the</strong>acceptance ofwheat prepared in ways to suit traditional cooking methods andpreferred tastes has been good; somefarmers have already begun plantingwheatfor home consumption. Home-scale bakeries are being established,creating a local marketfor wheat. This local-use approach to <strong>the</strong> introduction ofwheat is providing localfarmers with valuable experience, and wheatproduction can later be expandedfrom this beginning.321One of <strong>the</strong> major problems ofintrodUcing wheat into nonproducingcountries is that of finding a market forthat wheat as production commences.The large. mechanized flour mills arenot keen to accept <strong>the</strong> small lots ofwheat of differing quality that isinitially produced by <strong>the</strong> farmers. Thefarmers, on <strong>the</strong> o<strong>the</strong>r hand, want to seea market before <strong>the</strong>y begin plantingwheat. In Thailand. this problem mayhave been by-passed through a localuseapproach. which encouragesfarmers to begin planting wheat for<strong>the</strong>ir own consumption. In <strong>the</strong> 1983-84season. nearly 1,000 kg of wheat seedwas planted for ~ome consumption.In <strong>the</strong> more tropical countries wherewheat is being introduced, rice is <strong>the</strong>staple food. and <strong>the</strong> possibility thatwheat might be accepted into <strong>the</strong>traditional diet is often not considered.However. wheat has an importantpotential to increase basic foodproduction and improve nutrition in<strong>the</strong>se areas, since 1) rainfed wheat canbe an additional food crop during <strong>the</strong>cool, dry season when nothing waspreviously grown and 2) <strong>the</strong> nutritionalvalue of wheat is high. with nearlydouble <strong>the</strong> protein content of rice, aswell as much higher amounts ofvitamins Band E. Also. many areas.such as nor<strong>the</strong>rn Thailand. that aresuitable for grOWing wheat are ricedeficientareas. These factors formed<strong>the</strong> initial stimulus for <strong>the</strong> local-useapproach.Including Wheatin <strong>the</strong> Local DietThe local utilization of wheat is alreadysomething of a reality in Thailand. Oneof <strong>the</strong> keys to <strong>the</strong> acceptance of wheatby <strong>the</strong> local people has been <strong>the</strong>development and adaptation of foodsthat fit into <strong>the</strong> typical Thai diet,confonning with <strong>the</strong> traditional ways ofpreparing food as well as with <strong>the</strong>preferred tastes. Wheat is utilized inthree fonns in <strong>the</strong> preparation of <strong>the</strong>mainly Chinese-type foods:• As whole wheat. boiled and added torice and curries. fried with vegetablesand used for desserts;• As cracked wheat in boiled porridgewith vegetables and pork. in chilipaste eaten with rice, in taboolehsalad with chilies and in desserts withcoconut milk. and• As whole-meal flour. in flat, yeast,baked or steamed breads. in noodlesand as gluten for meat substitutes.

322There are two levels of utilization ofwheat. The preparations made fromwhole and cracked wheat appeal to <strong>the</strong>housewife for everyday use because <strong>the</strong>yare quick and simple to prepare. Also.small vendors use flour regularly to earna living. selling noodles. breads. etc. in<strong>the</strong> market places. These vendorsconstitute <strong>the</strong> local market for wheat.This use of wheat in <strong>the</strong> whole orcracked form frees wheat productionfrom <strong>the</strong> usual constraints imposed on itby flour quality.When local wheat is used as flour. it iseasy for <strong>the</strong> upcountry noodlemaker orbaker to adjust his technique to suit <strong>the</strong>type of flour on hand. or to blend in aquantity of commercial white flour.(This approach can also be followed withtriticale. whose utilization has beensomewhat restricted up to now due to itsflour quality.) These few factors indicate<strong>the</strong> great flexibility that wheat has as abasic foodstuff. a flexibility that shouldenable it to be accepted in one form orano<strong>the</strong>r in traditional diets.Planting Wheat for Local UseThe second key to <strong>the</strong> acceptance ofwheat in Thailand was a series of villagedemonstrations to show <strong>the</strong> local peoplewhat sort of foods <strong>the</strong>y could preparefrom wheat if <strong>the</strong>y chose to plant it.These demonstrations were held within<strong>the</strong> framework of various ruraldevelopment programs of <strong>the</strong>Department of Agricultural Extension.schools and nongovernmentorganizations. As a result of <strong>the</strong>sedemonstrations. local people requestednearly 1.000 kg of seed wheat forplanting for home consumption in <strong>the</strong>1983-84 season. There were 27 sites ofrainfed and irrigated wheat. planted inplot sizes that varied from 1/5 to 1 hatThe yields were generally low (0.6 Uhaor less). due to well-identified reasons. ofwhich inexperience was one of <strong>the</strong>principal ones. For <strong>the</strong> coming season.in spite of <strong>the</strong> low yields of <strong>the</strong> fIrstattempt. requests for seed haveincreased.Mter <strong>the</strong> 1984 harvest. <strong>the</strong> homeeconomics officials from <strong>the</strong> Departmentof Agricultural Extension held WheatDays in <strong>the</strong>ir areas. As a result. anadditional 680 farmers expressedinterest in planting wheat (1110 ha each)for <strong>the</strong>ir own consumption; <strong>the</strong>department at this time has <strong>the</strong> abilityto provide only 240 farmers with seed.In <strong>the</strong> nongovernment sectors. four of<strong>the</strong> internationally fun"ed projectsworking with <strong>the</strong> development of <strong>the</strong>minority hill tribes and with opium cropreplacement will also include in <strong>the</strong>irprograms <strong>the</strong> use of wheat for homeconsumption. The scope of <strong>the</strong> programfor <strong>the</strong> future is for wheat to be includedin many o<strong>the</strong>r rural development.vocational and nonformal educationprograms.The Local Market for WheatMter just one year's experience. <strong>the</strong>re isno doubt that wheat is acceptable to <strong>the</strong>local palate; in fact. <strong>the</strong>re is even ademand for whole wheat seed and wholemeal flour by those who are not plantingit. Bread, noodles and <strong>the</strong> ubiquitousinstant noodles are common wheatproducts already in use in Thailand. Toenable <strong>the</strong>se wheat products to be madein a typical Thai or hill-tribe village,some original methods have beendeveloped and ancient ones revived. Asa result. anyone will be able to buywheat from a local farmer and becomeself-employed. baking bread or makingnoodles for sale in <strong>the</strong> market place.One of <strong>the</strong> big advantages of local wheatwould be its price; 7 to lOB per kg(USS .35-.50) for whole meal flour,depending on <strong>the</strong> source. as comparedto at least 14B per kg (USS 0.70) forcommercial white flour. Someexperience has already been gained bysmall bakeries that grind <strong>the</strong>ir own flourfrom locally grown wheat. A charcoal-

323fired oven has been used at oneupcountry site for two years. Ano<strong>the</strong>rbaker. who started 18 months ago inChiang Mai city, now expects topurchase some 5 tons of wheat from <strong>the</strong>coming season's crop. There have beeno<strong>the</strong>r off-shoots of this work which,though small, indicate <strong>the</strong> manner inwhich wheat can become integrated into<strong>the</strong> local economy. One man. forexample, has begun producing small tinovens for home baking to earnadditional income in his spare time.Thus, as well as <strong>the</strong> contribution it canmake to food production, wheat is likelyto increase job opportunities in ruralareas. Just how great will be <strong>the</strong>potential effect of wheat on <strong>the</strong> localeconomy, while very real. is difficult toestimate at this stage.The development of <strong>the</strong>se local marketswill allow time for an increase in <strong>the</strong>number of farmers with experience inwheat planting and production. Once<strong>the</strong> number of competent wheat farmershas reached a significant number (2000to 5(00), <strong>the</strong> wheat-growing areas canbe qUickly increased to supply <strong>the</strong> flourmills with a set quota. This is mostimportant, as it will give researchers <strong>the</strong>opportunity to study <strong>the</strong> problems ofproduction. storage. handling andquality, before being committed tosupplying <strong>the</strong> large flour mills inBangkok.For this reason, <strong>the</strong>re are plans withChiang Mai University and <strong>the</strong>Department of Agricultural Extension tolook at local markets at three sitesduring <strong>the</strong> coming year. One of <strong>the</strong>m isChiang Mai. <strong>the</strong> largest city in <strong>the</strong> north(population 100.(00) which already hasan annual demand for at least 10 to15 tons of whole meal flour; twoupcountry sites will also be included in<strong>the</strong> production areas. These localmarkets will also serve an extensionfunction. "as people begin to encounterwheat and realize that it has been grownin <strong>the</strong>ir own area.Substitution of Wheat ImportsThe local-use approach should functionin <strong>the</strong> plan for achieving crop importsubstitution for wheat through <strong>the</strong>follOWing three steps:• 1. Family use-Farmers fIrst plantwheat for home consumption (smallnumber of farmers, small-sized plotsof 1/5 to 2/5 hal• 2. Local market-Local markets aredeveloped, absorbing <strong>the</strong> increasingproduction (<strong>the</strong> number of farmersincreases. but plots remain small)• 3. Crop import substitution-Quotasfor domestic wheat at flour mills areset and, after a large enough numberof farmers are planting wheat, <strong>the</strong>areas planted by individual farmerscan be qUickly increasedSteps 1 and 2. which are already inprogress. will provide <strong>the</strong> experienceneeded to move to 8tep 3 withconfIdence. This move to step 3 willrequire <strong>the</strong> cooperation of farmers. flourmills and <strong>the</strong> Royal Thai Government.The New Role of Wheat inMore Tropical EnvironmentsWhile <strong>the</strong>re are many problemsconcerned with wheat production,storage and quality in nontraditionalwheat-growing countries, <strong>the</strong>re is alsogreat faith in <strong>the</strong>ir ability to solve <strong>the</strong>seproblems. The idea emphasized in thispaper is that <strong>the</strong> role of tropical wheatshould extend far beyond that ofjustsubstituting for imported wheat. Instead.it has <strong>the</strong> potential to increase <strong>the</strong>amount of basic food available. It canalso provide new job opportunities inrural areas, thus boosting localeconomies. The brief experience inThailand has shown that <strong>the</strong>re is littleproblem with <strong>the</strong> acceptance of wheat asa food. Therefore, <strong>the</strong>re is every reasonto believe that wheat can playa role indirectly helping to feed <strong>the</strong> people of <strong>the</strong>more tropical environments.

324Problems and Benefits ofReintroducing Wheat into <strong>the</strong> PhilippinesA.V. Rotor, National Food Authority, Manila, PhilippinesAbstractIn an attempt to revive wheat groWing in <strong>the</strong> Philippines. an interagency ad hocgroup is entering its third year ofprogram expansion; it has determined anumber ofproblem areas. This paper outlines <strong>the</strong>se areas and analyzes <strong>the</strong>mfor current as well asforfuture action. The problems cited are categorized intotechnological. sociological. economic and governmental matters. Many of <strong>the</strong>seproblems had been anticipated and, <strong>the</strong>refore, served as basesforformulatingmajor decisions and policies and in supporting a proposal to create a nationalwheat program.The Philippines once enjoyed areputation as a wheat-growing country;this was during <strong>the</strong> Spanigh regime.from <strong>the</strong> 17th to <strong>the</strong> end of <strong>the</strong> 19thcentury (1). However, <strong>the</strong> cultivation ofwheat was limited to <strong>the</strong> nor<strong>the</strong>rn partof Luzon and <strong>the</strong> highlands. Basically itwas for home use. although a part of<strong>the</strong> produce was exported through <strong>the</strong>galleon trade between Manila andAcapulco (3).The local wheat varieties have beenpermanently lost. as has <strong>the</strong>irindigenous culture. There have beentwo previous attempts at revivingwheat cultivation in this century. andnow a third one is being undertaken (2).The areas of concern relating to <strong>the</strong>development of a local wheat industryare classified into four categories. Undereach category. <strong>the</strong> major activities arebriefly explained. with problem areasand future courses of action discussed.Production andPost-Harvest ConsiderationsDetermining potential wheat areasBased on <strong>the</strong> results of field trials andcommercial plantings. <strong>the</strong> area suitablefor wheat production appears to be <strong>the</strong>nor<strong>the</strong>rn proVinces of Luzon; it offers avery limited number of hectares forwheat culture. There is a need toexplore o<strong>the</strong>r regions of <strong>the</strong> country.Selecting and breedingof superior varietiesYields obtained from <strong>the</strong> presentvarieties. Trigo 1 (hard grain type) andTrigo 2 (soft type) are between one andtwo tons per hectare. These varietiesleave much to be desired in terms ofhigh and consistent yield levels.resistance to diseases. maturity classand baking quality.Improving packages of technologyPackages of technology have beendeveloped for wheat production. Theycan be used and adopted until betterpackages are available for specificlocations and conditions. Productionmodels have been set up. patterned afterfarming systems that have beensuccessful in <strong>the</strong> last two crop years.Increasing seed supplyUnder an interim arrangement. <strong>the</strong>Ministry of Agriculture and Foodcertifies seed that is produced. while <strong>the</strong>National Food Authority (NFA) handlesseed increase and production on acommercial scale. This cooperativearrangement is an attempt to solve <strong>the</strong>current shortage of seed and to supplyprojected expanSion needs.

325ControlliDg fungal diseasesThe incidence of sclerotium andhelminthosporium infections can causenear crop failures (5). Practical andinexpensive control measures are beingdeveloped. as well as methods ofapplying fungicides.Controlling weedsWeed control constitutes as much as20% of wheat production costs on manyfarms. While available farm labor favorsmanual or mechanical weeding. this is alabor-intensive activity and is expensive.Developing post-harvesttechniques and toolsPaddy rice threshers used for wheat givelow threshing recovery. Threshers arenow being developed that are specific forwheat. Post-harvest technology is now apart of farmer training.EstabUshing anefficient marketing systemWheat is a new addition to NFA's grainmarketing program. The flour millsshould provide a market for local wheatas its volume increases.Economic ConsiderationsProjecting economicgains on <strong>the</strong> macro levelSince 1975. total wheat imports havetotaled 6.732.178 tons (4). Thebreakthrough in commercial productionwould definitely save precious dollars for<strong>the</strong> country. At an average yield of 1.5tons per hectare. some 600.000 hectaresof land are needed to meet presentannual consumption. Since wheat isbest in rice-based areas. follOWing <strong>the</strong>regular rice crop. <strong>the</strong> displacement ofsome of <strong>the</strong> second rice crop and o<strong>the</strong>rcash crops is inevitable.Making wheat comparativelyprofitable with o<strong>the</strong>r cropsExcept for high-value cash crops. wheatshould generate a return on investmentcomparable to that of maize. peanuts,mungbean and rice itself. Highproduction costs plus erratic yieldshave been responsible for a low returnon investment and even losses. Anincrease in government farm pricesubsidy is under consideration.Improving qualityto meet standardsThe inferior quality of locally producedwheat is at present a problem beingfaced by research and extensionpersonnel. Meanwhile, products madefrom local wheat can be improved byblending with premium importedwheat.Organizing cooperativewheat farmingIn <strong>the</strong> absence of large farms within <strong>the</strong>wheat belt. wheat is grown onindividual small farms; farmers areorganized under prototype cooperatives.Wheat cultivation on a plantation scaleis being considered in o<strong>the</strong>r areas.Social ConsiderationsFacilitating acceptanceof <strong>the</strong> new cropA sustained information campaign isbeing carried out. along with fielddemonstrations, seminars and <strong>the</strong>training of farmer cooperators in <strong>the</strong>wheat program.Promoting direct usesof wheat in <strong>the</strong> homeThe conventional pathway of wheat isto <strong>the</strong> flour mill and <strong>the</strong>n to <strong>the</strong> bakerybefore <strong>the</strong> end product reaches <strong>the</strong>consumer. Local groWing of wheat islikely to revolutionize this system. butit will take time. The preparation ofwheat products in <strong>the</strong> home is inagreement with <strong>the</strong> government'snutrition program.

326Governmental ConsiderationsDesigning a nationalwheat programThe present wheat developmentprogram comes under <strong>the</strong> PhilippineCouncil for Agricultural ResourcesResearch Development (PCARRD). Ithas an ad hoc interagency structure,with each of <strong>the</strong> six membersconducting specialized and more or lessindependent projects. The objective of<strong>the</strong> wheat management committee ofPCARRD is to elevate <strong>the</strong> present wheatprogram, now in its third year, to <strong>the</strong>national level. As a national program, itshould gain more support for attainingindustry status. This proposal is nowunder consideration (5).Streng<strong>the</strong>ninginteragency coordinationCooperation among <strong>the</strong> agenciesworking on <strong>the</strong> wheat program shouldbe streng<strong>the</strong>ned, particularly in <strong>the</strong>expansion of commercial projects.Priority research is now focused on fieldproblems being encountered byfarmers.Financing wheat farmersand providing crop insuranceCrop loans and insurance should beprovided to wheat farmers.Arrangements are being made with <strong>the</strong>Technical Board of Agricultural Credit(TBAC) of <strong>the</strong> Central Bank and <strong>the</strong>Philippine Crop Insurance Corporation(PCIC) as part of <strong>the</strong> proposed nationalwheat program.The hope of developing a local wheatindustry hinges on <strong>the</strong> expansion of <strong>the</strong>present program. To a large extent, italso depends on world issues affecting<strong>the</strong> commodity. The Philippines atpresent is bracing itself against aneconomic crisis. Wheat imports, whichin 1982 alone reached 900,000 tonsworth US$ 156 million, are now beingdrastically cut to reduce <strong>the</strong> foreignexchange drain (4). Now is <strong>the</strong> time torevive <strong>the</strong> old, lost wheat industry.References1. Cabafios, J.B. 1960. Progress reporton trial cultures of wheat withcooperators in <strong>the</strong> Philippines.Araneta Journal of Agriculture7(1):36-39.2. Cruz, E.E. 1960. The work of <strong>the</strong>Bureau of Plant Industry on Wheat.Araneta Journal of Agriculture7(1):40-42.3. Gironiere, P. de. 1962. Twentyyears in <strong>the</strong> Philippines. FilipinianaBook Guild I. P. 221.4. National Food Authority. 1984.Briefing materials. Quezon City,Metro Manila, Philippines.5. Philippine Council for Agricultureand Resources Research andDevelopment. 1984. Notes on wheatcrop year 1983-84. Los Bafios,Laguna, Philippines.

The Relative Priority andEconomics of Growing Wheat in NigeriaA.a. OgUDgblle, Institute for Agricultural Research, Ahmadu BelloUniversity, Zaria, NigeriaAbstractThe main aims of <strong>the</strong> Nigerian government policy ofproducing wheat on largescaleirrigation schemes were to substantially increasefood production and toachieve import substitution objectives. Many years after <strong>the</strong> establishment of <strong>the</strong>projects. those objectives are stillfarfrom beingfuifUled. Although wheatproduction appears more profitable than some cereal crop enterprises. averageyields have remained lower than <strong>the</strong> potential. Timely planting. better inputdelivery and improved extension services arefactors crucial to achievingproduction increases. Local market prices are higher than <strong>the</strong> governmentproducer price and, <strong>the</strong>refore. farmers do not sell to <strong>the</strong>.flour mills.327Wheat has been grown traditionally in<strong>the</strong> river valleys in <strong>the</strong> nor<strong>the</strong>rn parts ofNigeria for many years. However. earlyproduction was on a small scale. with<strong>the</strong> grain being sold in local markets asa luxury product used for makingtraditional dishes (4). Its importance in<strong>the</strong> diet of <strong>the</strong> people has increaseddramatically in recent years withincreases in income and population.Annual wheat importation rose fromabout 190.000 tons in 1969 to about1.5 million tons in 1983. costing <strong>the</strong>country nearly US$ 290 million inforeign exchange. A total of US$ 1.95billion was spent on food imports in1980 (5). with wheat constituting <strong>the</strong>single largest item in Nigeria's heavyfood import bill. The sudden popularityof wheat bread in <strong>the</strong> Nigerian diet. and<strong>the</strong> consequent increase in wheatimportation. prompted <strong>the</strong> Nigeriangovernment to encourage <strong>the</strong>production of wheat in substantialquantities domestically.Objectives of <strong>the</strong> WheatProduction and Water ResourceDevelopment PolleyGovernment encouragement ofdomestic wheat production for flourcannot be isolated from <strong>the</strong> agriculturalpolicy of achieving self-suffiCiency infood production and promoting <strong>the</strong>welfare of <strong>the</strong> rural people. The mainobjectives of domestic wheat productionare 1) to stimulate substitution forimported wheat in order to improve <strong>the</strong>balance of payment situation. 2) topromote agro-industrtal developmentand 3) to enhance food productionefforts (1).The majority of <strong>the</strong> wheat consumed inNigeria is in <strong>the</strong> form of bread. In orderto facilitate <strong>the</strong> processing of wheat intoflour. a flour-milling industry wasconsidered. not only as an integral partof <strong>the</strong> package of wheat production. butalso as an important agro-based infantindustry that would have to be protectedfrom foreign competition. This proVided<strong>the</strong> justification for increasing <strong>the</strong>number of flour mills to five by 1980.with a joint capacity of 1.2 million tonsof wheat per annum.Wheat Production andWater Resource DevelopmentSince <strong>the</strong> early 19708. increasedemphasis has been given to <strong>the</strong>development of irrigation. as a means ofachieving <strong>the</strong> full agricultural potentialof <strong>the</strong> country (5). The Sahel drought of<strong>the</strong> early 19708 gave impetus to heavypublic investment in irrigation schemes.About US$ 398.4 million and $2.95

328billion were allocated to irrigation andwater development in <strong>the</strong> 1975-80 and<strong>the</strong> 1980-85 development plan periods.respectively. Irrigated agriculture wasexpected to lead to a significantimprovement in both <strong>the</strong> yield andoutput of crops. This would. in tum.reduce food imports substantially. andbring about a considerable saVings inforeign exchange. By 1976. eleven riverbasin development authorities werecreated in <strong>the</strong> country to carry out <strong>the</strong>planned large-scale irrigation schemes.Nearly 2 million hectares of land wereproposed to be under irrigation by <strong>the</strong>1980-85 period. but less than 20.000hectares were actually being cultivatedby <strong>the</strong> river basin authorities by <strong>the</strong> endof 1980 (6).Wheat production is linked withirrigation development. in that rainfedwheat production has been consideredtechnically unfeasible in Nigeria from<strong>the</strong> onset. Therefore, <strong>the</strong> bulk of wheatproduction was planned to be grown onlarge-scale irrigation schemes. Waterand temperature. <strong>the</strong> most importantlimiting factors in domestic wheatproduction. are adequate in three of <strong>the</strong>river basins that have been fairly welldeveloped within <strong>the</strong> wheat zone of <strong>the</strong>country. These are <strong>the</strong> Chad. SokotoRima and Hadejia Jama-are River BasinDevelopment Authorities. Out of a totalof 345.000 hectares planned fordevelopment of irrigated agriculture in<strong>the</strong> projects. about 163.854 hectareswould be devoted to wheat. Assumingproductivity of 2 tfha. a maximum of330.000 tons per annum could beexpected; this is less than one-third of<strong>the</strong> current wheat imports (2). Theirrigation schemes have been inproduction for more than seven years.and present domestic wheat productionis estimated to be less than 40.000 tons.about 2% of total current consumption.O<strong>the</strong>r crops being grown in <strong>the</strong>irrigation schemes include tomatoes ando<strong>the</strong>r vegetables. maize. soybeans.cowpeas. rice. cotton. groundnut. milletand sorghum. However. only a relativelysmall area of land can be devoted totomatoes and o<strong>the</strong>r vegetables. because<strong>the</strong>y are highly perishable. and <strong>the</strong>irproduction is very labor intensive. Theareas grown to all of <strong>the</strong>se crops isrestricted during <strong>the</strong> dry season in favorof wheat. since it cannot grow at anyo<strong>the</strong>r time of <strong>the</strong> year. Also. <strong>the</strong>re areo<strong>the</strong>r agricultural development projectsfor boosting <strong>the</strong> production of <strong>the</strong>seo<strong>the</strong>r crops under rainfed and irrigatedconditions.Financial Costs andReturns of Producing Wheat,Maize and SorghumMaize. millet and sorghum are among<strong>the</strong> traditional cereal crops whoseproduction could be affected byincreases in wheat production. Table 1illustrates <strong>the</strong> costs and returns involvedin producing one hectare each ofirrigated wheat. rainfed maize andsorghum. These data represent <strong>the</strong>preliminary results from two separatestudies that were carried out in <strong>the</strong>1983-84 season. involVing 50 farmersgrowing wheat in Kadawa village under<strong>the</strong> Hadeija Jama-are irrigation project.and 60 farmers in Daudawa villagegrowing ralnfed maize and sorghumwith improved technology. Onlyfarmers' production costs were includedin <strong>the</strong> study. No attempt was made toestimate <strong>the</strong> capital cost of <strong>the</strong> irrigationscheme with respect to wheat. Laborrepresented a significant portion of <strong>the</strong>total costs. although unpaid family laborconstituted about half of total laborcosts; harvesting was <strong>the</strong> most timeconsumingactivity in cereal production.Poor land leveling increased <strong>the</strong> cost ofirrigation. With <strong>the</strong> exception of maize.wheat gave a higher net income thanmost ralnfed crops. such as sorghum.millet and groundnut.

329Comparative MarketPrices of Staple Food CropsWheat substitutes for o<strong>the</strong>r cereals inproduction and consumption in Nigeria;Table 2 compares <strong>the</strong> price of wheatwith <strong>the</strong> market price of some o<strong>the</strong>rstaple food crops. The local marketprice for wheat remained higher thano<strong>the</strong>r cereal prices until 1980. whenmore wheat became available on <strong>the</strong>local market; it was being substitutedfor sorghum and millet whoseproduction had suffered a setbackbecause of bad wea<strong>the</strong>r and maizeencroachment into <strong>the</strong> traditionalsorghum/millet zones. Although <strong>the</strong>recently announced price ofUSS 585/ton leaves some profit marginfor wheat growers. <strong>the</strong> local marketprice can be as much as three timeshigher. explaining why locallyproduced wheat is not getting to <strong>the</strong>mills.ConclusionsThe policy to produce wheat underlarge-scale irrigation schemes hasgenerated a number of criticisms:• Import substitution through localwheat production has led to allocationof resources to wheat at <strong>the</strong> expenseof crops more natural to <strong>the</strong> domesticenvironment (3);• Despite huge investments. fewerfarmers have benefited. as comparedto schemes designed for rainfedagriculture. Because of <strong>the</strong> irrigationprojects. many farmers have lost <strong>the</strong>irland without adequate compensation(7);• Very little attention was paid to <strong>the</strong>economic feasibility of <strong>the</strong> schemeduring <strong>the</strong> planning stage. andTable 1. Comparative costs and returns of irrigated wheat and rainfed maize and sorghum,Nigeria, 1983-84Costs and returns (US$)Production factors Wheat Maize SorghumOutput (kg/ha) (2500) (2928) (1650)Value.A/ 1462.05 1522.56 900.90Labor cost/ha 404.57 445.58 312.00Cost of inputs o<strong>the</strong>r than laborSeed 77.06 15.60 15.60Fertilizer 67.43 57.20 44.20Herbicide 89.70 78.00Depreciation of oxen and equipment 78.00 78.00Water charges 48.17Tractor charges 111.89Total cost/ha 709.12 686.08 527.80Net return/ha 753.38 836.48 373.10.A/ Wheat was valued at about US$ 0.59/kg, maize .52/kg and sorghum .55/kg

330• Establishment of high-capacity flourmills presupposed continued wheatimportation to ensure full utilizationof available capacity. Both <strong>the</strong> millsand <strong>the</strong> irrigation projects have beenin production for more than sevenyears without any significant suppliesarriving at <strong>the</strong> mills from localsources.Although serious doubts have beenraised as to <strong>the</strong> ability of<strong>the</strong> projectsto increase wheat productionsubstantlally in <strong>the</strong> future. it is toolate to stop <strong>the</strong> construction of damsand canals now. The problem is that<strong>the</strong> irrigation facilities developed for<strong>the</strong> production of wheat and o<strong>the</strong>rcrops have not been efficientlyutilized. The volume orwheatproduced can be increasedsubstantially ifall <strong>the</strong> developed landfor irrigation is allocated andcultivated. Average yield of wheat canalso be increased considerablythrough timely planting. better inputand services delivery and <strong>the</strong>provision of better extension servicesto farmers. Wheat importation shouldbe gradually reduced to enableNigerians to decide what proportion oflocally produced wheat <strong>the</strong>y requirefor traditional dishes and bread.Table 2. Average retail price of cereal crops in selected markets,Zaria, Nigeria, 1973 to 1983Price per ton (US$)Year Sorghum Millet Maize Wheat1973 167.61 169.70 157.53 333.501974 188.34 169.46 183.95 393.391975 178.24 166.45 195.60 364.001976 246.74 241.54 278.33 364.001977 327.60 316.16 401.70 470.861978 423.67 453.05 432.12 732.031979 367.77 413.01 391.56 544.051980 389.87 400.01 456.82 519.481981 676.00 741.00 611.00 663.001982 559.00 702.00 572.00 663.001983 637.00 644.54 679.38 611.00Source: Department of Agricultural Economics and RuralSociology, I.A.R. t Zaria, Nigeria

331References1. Agricultural Extension andResearch Liaison Services. 1979.Report on wheat production inNigeria. Ahmadu Bello University.Zaria. Nigeria.2. Ahmad. M.M. 1983. Economics"ofwheat production under surfaceirrigation: A case study of KadawaIrrigation Project. Researchproposal. Ahmadu Bello University.Zaria. Nigeria.3. Andrae. G.• and B. Beckman. 1981.Wheat trap: Bread andunderdevelopment in Nigeria.Project proposal and outline.Ahmadu Bello University. Zaria.Nigeria.5. Etuk. E.G.• and G.O.I. Abalu. 1982.River basin development in Nigeria:A case study of <strong>the</strong> BakoloriProject. In Proceedings of <strong>the</strong>Fourth Afro-Asian RegionalConference 2:335-346.6. Nwa. E.U.• and B. Martins. 1982.Irrigation development in Nigeria.In Proceedings of <strong>the</strong> Fourth AfroAsian Regional Conference 1:1-16.7. Voh Jacob. P. 1982. Strategies forimproving agricultural productionamong farmers displaced by a manmadelake: A case of Tiga Dam inKano State of Nigeria. InProceedings of <strong>the</strong> Fourth MroAsian Regional Conference2:353-365.4. Andrews. D.J. 1968. Wheat andresearch in Nigeria. NigerianAgricultural Joumal5(2):67-7l.

332Socioeconomic and AgroeconomicImplications of Growing Wheat in SudanF.M. Ali, Agricultural Research Corporation, Wad Medani, SudanAbstractThe success in wheat research has enhanced <strong>the</strong> expansion of<strong>the</strong> wheat area in<strong>the</strong> Sudan; <strong>the</strong> intensijlcation and diversijlcation ofcropping systems hasincreased <strong>the</strong> land availablefor wheat production from 9.000 to 307,000hectares. A summary ofrecommended cultural practices is given. Wheat yieldson experiment stations range between 3 and 4.5 tlha, whereas commercialproduction yields are only .8 to 1.5 tlha. The cost ofwheat production,consumption and imports have increased; studies show that it would be moreeconomical to grow wheat in <strong>the</strong> Gezira than to import it. The expansion inwheat production has contributed to an increase infarmer income, which hasresulted in increased domestic household activities, social activities and leiSureconsumption; it has reduced <strong>the</strong> number offarmers migrating to o<strong>the</strong>rprofessions.Wheat has been regarded as a crop of<strong>the</strong> river-bottom environment north ofKhartoum, where it has long beengrown on a limited scale withtraditional methods of production.However, in <strong>the</strong> 1960s, <strong>the</strong> smallplantings and high cost of production,coupled with an increasing demand forwheat in <strong>the</strong> country, directed <strong>the</strong>attention of policy makers towards <strong>the</strong>areas of irrigated clay soils, whereenvironmental and general climaticconditions are less suitable for wheatproduction.The success in wheat research and <strong>the</strong>goal of <strong>the</strong> government to be selfsufficientin this commodityencouraged <strong>the</strong> expansion of <strong>the</strong> wheatarea. mainly in <strong>the</strong> Gezira and NewHalfa schemes. In <strong>the</strong> 1960-61 season.a large area was planted in <strong>the</strong> Gezirascheme. follOWing recommendationsfrom agricultural research; it had anencouraging average yield ofjust overone ton per hectare. The adoption of<strong>the</strong> intensified and diversified croppingsystem increased <strong>the</strong> land appropriatefor wheat production in <strong>the</strong> Gezira andNew Halfa to 252,000 and 46,200hectares, respectively; <strong>the</strong> wheat area in<strong>the</strong> nor<strong>the</strong>rn part of <strong>the</strong> countryremained at about 9.000 hectares.Wheat area. yield and production hasfluctuated from season to season, asshown in Table 1.Agronomic Aspectsor-Wheat ProductionWheat is grown in <strong>the</strong> Sudan during<strong>the</strong> winter period (October to March)under irrigation. The winter is shortwith relatively higher temperatures andlower humidity than those found in <strong>the</strong>traditional wheat-growing areas of <strong>the</strong>world. Table 2 shows <strong>the</strong> long-termaverage maximum and minimumtemperatures in <strong>the</strong> three mainproduction areas.Research recommendations for wheatproduction in <strong>the</strong> Sudan are availablefor <strong>the</strong> areas of land preparation.planting date. seeding rate andmethods. fertilizer use, irrigation. weed.insect and disease control and varieties.Land preparationPlOWing, disc harrOWing and leveling isrecommended to be carried out inSeptember.Planting dateThe period from mid-October to midNovember is recommended as optimum

Table 1. Area, average yield and total production of wheat in <strong>the</strong> three wheatllrowing regions, Sudan, 1975-76 to 1982-83Gezira New Haifa Nor<strong>the</strong>rn regionArea Yield Production Area Yield Production Area Yield ProductionSeason (000 hal (kg/ha) (000 tons) (000 hal (kg/ha) (OOO tons) (000 hal (kg/ha) (000 tons)1975-76 238 924 220 48 667 32 12 1700 201976-77 212 1178 250 33 619 20 13 1745 231977-78 196 1121 220 30 762 23 15 1293 191978-79 207 598 124 15 452 7 13 1112 141979-80 152 1133 172 16 786 12 13 1428 181980-81 154 548 84 22 690 15 13 1507 201981-82 112 1000 112 18 1095 20 13 1562 201982-83 66 1428 94 20 1428 28 NA!/ NA NAMean 991 812 1478~/ NA = figures not availableSource: Yearbooks of Agricultural Statistics, Department of Economics, Ministry of Agriculture and Irrigation, Khartoum, Sudan~~~

334for sowing. both as a result of researchfindings and for practical reasons.Factors that must be considered by <strong>the</strong>farmer include <strong>the</strong> availability of capitaland farm machinery. as well asirrigation water. for <strong>the</strong> various crops of<strong>the</strong> rotations in <strong>the</strong> different farmingschemes.SeecUDg rate aDd method of sowbagA seeding rate of 143 kg/ha isrecommended. with <strong>the</strong> seed sown witha drill in rows 20 cm apart.FertUlzer useThe only fertilizer recommended isnitrogen applied at sowing as sidedressing at <strong>the</strong> rate of 86 kg/ha.InlgatioDThe general recommendation is toirrigate wheat every two weeks.Weed eODtrolTaking into consideration <strong>the</strong> high seedrate being used and its effect insmo<strong>the</strong>ring weeds. as well as <strong>the</strong>herbicides being used on o<strong>the</strong>r crops in<strong>the</strong> rotation and mechanical weedcontrol dUring land preparation. noherbicides are officially recommendedfor wheat.IDseet aDd cUsease eODtrolThe only economically important insectpest in Sudan is <strong>the</strong> aphid and, to someextent. stem borers. Normally one ortwo sprayings of <strong>the</strong> appropriateinsecticide are applied dUring <strong>the</strong>season. Rust problems are ofimportance in New Halfa and <strong>the</strong>nor<strong>the</strong>rn part of <strong>the</strong> country; hence.only resistant varieties arerecommended for those areas.VarietiesThe principal recommended wheatvarieties for Sudan are Mexicani,Giza 155. Condor. Mukhtar. Shenaband Debera.When wheat is grown follOWing <strong>the</strong>above recommendations. yields as highas 3 to 3.5 t1ha are obtained on <strong>the</strong>experiment farms at Gezira and NewHalfa. In <strong>the</strong> nor<strong>the</strong>rn parts of <strong>the</strong>country. yields of 4 to 4.5 t1ha areachieved.Wheat Production,Imports and ConsumptionConsumption of wheat in <strong>the</strong> Sudanhas continued to rise, due to increasesin population. urbanization and <strong>the</strong>rising income of <strong>the</strong> people. Table 3Table 2. Average maximum and minimum temperatures during <strong>the</strong> wheat productionperiod in <strong>the</strong> three wheat-growing regions, Sudan, 1941 to 1970Wad Medani (Gezira) Kassala (New Haifa) Dongla(central region) (eastern region) (nor<strong>the</strong>rn region)Month Maximum Minimum Maximum Minimum Maximum Minimum(OC) (OC) (OC) (OC) (OC) (OC)October 37.8 21.6 36.9 23.2 38.7 21.1November 36.5 18.0 37.5 20.6 32.9 15.4December 33.8 14.5 35.0 17.0 29.0 10.7January 33.6 14.0 34.3 16.0 27.8 9.3February 35.1 14.7 35.4 16.4 29.7 10.2March 38.4 18.2 38.6 19.2 33.9 14.1Source: Sudan Meteorological Service Memo 5

Table 3. Annual domestic wheat production, imports and consumption, Sudan, 1975-76 to 1979-80Total domestic Amount saved Amount available Imports Total Totalproduction for seed~ for consumption Wheat Flour.!!1 imports consumptionSeason (000 tons) (000 tons) (000 tons) (000 tons) (000 tons) (000 tons)1975-76 264 56 208 120 - 120 3281976-77 294 53 241 207 21 230 4711977-78 317 52 265 143 24 170 4351978·79 117 44 133 187 26 216 3491979-80 219 38 181 298 33 335 516.!/ Includes 5 % extra for seed lossE/ Converted to wheat at extraction rate of 900/0Source: The Policy of Wheat Production in <strong>the</strong> Gezira Scheme (in Arabic)!

336shows domestic production, seedrequirements for sowing with seed lossset at 5%. imports and totalconsumption. Table 4 presents resultsof studies on projected future wheatconsumption, domestic production andimports.Cost of wheat productionThe costs involved in <strong>the</strong> production ofwheat have continued to rise everyyear, as shown in Tables 5 and 6. Thisis mainly due to increases in <strong>the</strong> pricesof production inputs. In spite of <strong>the</strong>sehigh costs of production, it has beenproven that wheat is a profitable cropfor producers when yields exceed950 kglha.Taking into consideration <strong>the</strong> projectedcost of production and prices of wheatin <strong>the</strong> international markets, and with<strong>the</strong> modest projected yields of 2,000.1,430 and 2.500 kg/ha for <strong>the</strong> Gezira,New Halfa and nor<strong>the</strong>rn regions.respectively. it was shown that it wouldbe more economical to grow wheat in<strong>the</strong> Gezira scheme until <strong>the</strong> 1990-91season than it would be to import it.The case of <strong>the</strong> New Halfa scheme canbe seen to be different (Table 7).The Social Impact of Growing WheatSorghum is <strong>the</strong> staple food for most of<strong>the</strong> Sudanese, although wheatconstitutes a major component of <strong>the</strong>diet in certain parts of <strong>the</strong> country,namely in <strong>the</strong> Nor<strong>the</strong>rn Region and NewHaIfa, as well as in urban communities.With <strong>the</strong> increasing prices of sorghumgrain, as well as <strong>the</strong> effort and fuelneeded for sorghum food preparation,increasing numbers of Sudanese areshifting from sorghum to wheat. Theseand o<strong>the</strong>r factors have enhanced farmerenthusiasm for wheat cultivation.Regardless of <strong>the</strong> crop profitability. itscultivation is regarded as a means ofsupplying family consumption needs. Inaddition, <strong>the</strong> high degree ofmechanization of wheat productionensures that it does not tax farmersphysically to any conSiderable degree.Fur<strong>the</strong>rmore. <strong>the</strong> crop was introduced asan addition to o<strong>the</strong>r crops in rotations:thus. it leads to increased family income.These factors have resulted in increaseddomestic household activities, education,social actiVities, leisure consumption andgainful nonagricultural activities amongfarmers: it has also reduced <strong>the</strong> numberof farmers migrating to o<strong>the</strong>rprofessions.Table 4. Projected wheat consumption, production and imports, Sudan,1985-86 to 1991-92Consumption Domestic production ImportsSeason (000 tons) (000 tons) (000 tons)1985-86 643.8 287.4 356.41986-87 672.9 313.5 359.41987-88 703.4 313.5 389.91988-89 735.4 313.5 421.91989-90 769.6 313.5 456.11990·91 805.3 313.5 491.81991·92 843.0 313.5 529.5Source: Ministry of Finance and Economic Planning. 1982. Comparative Study ofCost of Growing Wheat in <strong>the</strong> Sudan and Importing it from Abroad.Khartoum, Sudan.

337Table 5. Financial costs of wheat production in <strong>the</strong> Gezira Scheme, Sudan, 1976-77 to 1981-82Cost per hectare (LS)..!/Land Agricultural Material Land and Miscel·Season preparation operations inputs Harvesting water laneou,.!!/ Total1976-77 6.62 4.76 45.33 10.00 4.76 71.471977·78 6.93 5.00 46.57 10.60 5.00 74.001978-79 11.43 7.98 28.12 11.90 11.31 70.741979-80 11.07 7.74 52.95 17.86 11.90 101.521980-81 17.98 8.21 64.60 20.24 14.28 125.311981-82 18.81 12.86 108.93 19.06 12.14 171.79J!/ 1.3 LS (Sudanese pounds) = US$ 1J!/ Mainly on·farm transport and materialsSource: Ministry of Finance and Economic Planning. 1982. Comparative Study of Cost ofGrowing Wheat in <strong>the</strong> Sudan and importing it from abroad. Khartoum, Sudan.Table 6. Financial costs of wheat production in <strong>the</strong> New Haifa Scheme, Sudan, 1976·77 to 1981·82Cost per hectare (LS).!J'Land Agricultural Material Land and Miscel·Season preparation operations inputs Harvesting water laneous.!!/ Total1976·77 7.55 7.21 35.05 8.21 9.05 67.071977·78 8.48 8.19 38.12 18.38 8.19 81.361978-79 8.98 6.95 45.02 10.48 13.57 85.001979-80 20.83 13.88 51.43 14.28 NA 100.421980-81 12.31 15.48 77.50 14.28 3.12 122.691981-82 24.28 15.12 93.76 17.14 71.43 6.19 227.92J!/ 1.3 LS (Sudanese pounds) = US$ 1il/ Mainly on·farm transport and materialsSource: Ministry of Finance and Economic Planning. 1982. Comparative Study of Cost ofGrowing Wheat in <strong>the</strong> Sudan and Importing it from Abroad. Khartoum, Sudan.

338Table 7. Projected financial costs of imported and locally produced wheat,Sudan, 1982-83 to 1990-91Season1982-831985-861990-91Cost per ton (LS)J!/Local production bl286.78 192.50 465.94(-+g4.28) (-179.16)357.86 139.35 351.10(+218.51) (+6.76)488.04 197.87 492.25(+290.17) (-4.21)~/ 1.3 LS (Sudanese pounds) = US$ 112/ Numbers in brackets = saving or loss of locally produced wheat versusimportsSource: Ministry of Finance and Economic Planning. 1982. ComparativeStudy of Cost of Growing Wheat in <strong>the</strong> Sudan and Importing itfrom Abroad. Khartoum, Sudan.

Comments'D.L. WiDkelmaDll, DIrector, Economics Program, CIMMYT, Mexic&.339I have been asked to comm.ent fur<strong>the</strong>ron <strong>the</strong> demand side of wheats for moretropical environments. It has beendemonstrated over <strong>the</strong> past five yearsthat wheat is a surprisingly plasticcrop. Given <strong>the</strong> evidence that we canincrease <strong>the</strong> productivity of wheats in<strong>the</strong> tropics. <strong>the</strong> question must be asked:To what extent and where should wedo so? Where will future wheatproduction be more promising. andwhere will it be less so?Dr. Harrington has presented a way toget at <strong>the</strong> fundamentals of <strong>the</strong> issue.through assessing <strong>the</strong> real value of <strong>the</strong>resources that might be involved in <strong>the</strong>production of wheat. He discussed <strong>the</strong>application of comparative advantage(<strong>the</strong>se proceedings). based on atechnique called domestic resource costanalysis. One result of his analysis inparts of Thailand was <strong>the</strong> estimation of<strong>the</strong> yield range needed to make wheatcompetitive with its alternatives, bothfrom <strong>the</strong> perspective of <strong>the</strong> fanner andfrom <strong>the</strong> perspective of society. Indifferent local environments. verydifferent yield levels appear to beneeded to make wheat competitive.These differences are largely dependenton <strong>the</strong> alternatives to wheat and on <strong>the</strong>extent to which wheat productioninfluences preceding and followingcrops.Let us consider <strong>the</strong> demand for wheatand for wheat research in <strong>the</strong> tropics.We have heard mention of wheat pricesbeing set by policymakers whoseconcern is especially for urbanpopulations. We have been told thatsome countries need to dispose ofwheat surpluses, and that. in somecases. <strong>the</strong>y may have a desire to createdependencies; o<strong>the</strong>rs saw generosity in<strong>the</strong> subsidizing of wheat for developingcountries. We have also heard aboutpolicies which perhaps reflect anignorance about <strong>the</strong> potentials ofenvironments.Surely all of <strong>the</strong>se considerations play apart. in greater or lesser measure. indecisions affecting <strong>the</strong> role of wheat in<strong>the</strong> more tropical regions of <strong>the</strong> world.Beyond this. however. Dr. Byerleehelped us to consider wheatconsumption from o<strong>the</strong>r perspectives(<strong>the</strong>se proceedings). He pointed outsome apparent inevitabil1tiesinfluencing this consumption.Urbanization and rising incomeshistorically favor wheat consumption.Beyond this. he identified someconcerns-rural income distribution.diets for poor consumers. and foodsecurity-whose influence on wheatutilization must result from carefuljudgments of society-wide issues. Healso discussed exchange rateovervaluation and relative prices whichdepart markedly from those on <strong>the</strong>international market. The utilization ofwheat in tropical countries emergesfrom a mixture of such considerations.It is important to realize. however. thata rising demand for wheat is anapparently inevitable consequence ofurbanization-people want foods whichare more convenient-and of risingincomes-people can insist on morediversity in <strong>the</strong>ir diets. Income is anespecially important factor indeveloping countries. Remember <strong>the</strong>graph describing circumstances innor<strong>the</strong>rn Brazil (Byerlee. <strong>the</strong>seproceedings), shOWing <strong>the</strong> relationshipbetween income level and <strong>the</strong>consumption of particular commodities.As income increased. <strong>the</strong> directconsumption of maize declined. acommon response. but <strong>the</strong> per capitaconsumption of rice and wheatincreased.

340The demand for wheat is going tocontinue to expand as urbanizationcontinues and incomes rise. Some ofthat demand can be filled locallythrough more appropriate wheattechnologies. On a related point. <strong>the</strong>importance of <strong>the</strong> opportunities for localproduction described by wheat importsis not well measured by <strong>the</strong> amount offoreign exchange which can be savedthrough local production. A simpler butstill rough approximation is given bytransportation costs. those of bringingin wheat plus those of sending out <strong>the</strong>compensating export.All of <strong>the</strong>se considerations discussed byByerlee and Harrington provide aportion of <strong>the</strong> background for judging<strong>the</strong> critical question associated with <strong>the</strong>allocation of research resources towheat. Along with o<strong>the</strong>r importantconsiderations. l~d by <strong>the</strong> plantbreeders' sense of <strong>the</strong> opportunities.<strong>the</strong>y can help in deciding in which of<strong>the</strong> many environments scarce researchresources should be focused.Good progress has been made. andmore is in <strong>the</strong> offing as researcherspursue <strong>the</strong> still-emerging opportunitiesfor wheat production in <strong>the</strong> tropics andsubtropics.

7341------_1Closing Remarks, <strong>Symposium</strong> onWheats for More Tropical EnvironmentsB. C. Curtis, Director, Wheat Program, CIMMYT, MexicoThis symposium, sponsored through agrant from <strong>the</strong> United NationsDevelopment Programme, was convenedfor <strong>the</strong> purpose of updating <strong>the</strong>information available on <strong>the</strong> status ofresearch for <strong>the</strong> development ofgermplasm and cultural practices forgrOWing wheat in some of <strong>the</strong> moretropical areas of <strong>the</strong> developing world. Inattendance were a total of 57 peoplerepresenting 22 countries, mostly fromtropical regions with an interest ingrowing wheat. In addition, 38 CIMMYTpersonnel. along with 10 members of<strong>the</strong> wheat program outreach staff,participated in this conference.CIMMYT's tropical wheat projectdeveloped as a result of intense intereston <strong>the</strong> part of several national programsto produce <strong>the</strong>ir own wheat in anattempt to eliminate <strong>the</strong> foreignexchange drain that occurs with heavywheat importation. While <strong>the</strong> project has<strong>the</strong> word "tropical" in its description, ithas been noted that this should not beconstrued to mean wheats for <strong>the</strong> hot,humid, rain forest environments. Wheatis essentially a temperate crop and <strong>the</strong>term, tropical wheat, is merely a simpleway of referring to "wheats for <strong>the</strong> moretropical environments." Some of <strong>the</strong>semore tropical environments are oneswith a winter season with coolertemperatures and drier groWingconditions.In his keynote address, Mr. Mashler saidthat, in <strong>the</strong> late 1970s, he and <strong>the</strong> UNDPrecognized <strong>the</strong> need to fund a project toaid in <strong>the</strong> development of wheats to fitinto <strong>the</strong> nontraditional. more tropicalareas. UNDP was motivated by <strong>the</strong> factthat wheat accounts for more than onefourthof <strong>the</strong> world's grain production, isa staple food for one-third of <strong>the</strong> world'spopulation and has an upwardconsumption trend. With UNDPassistance, CIMMYT has expanded itsresearch to develop wheats for <strong>the</strong> moretropical environments; funds were madeavailable by UNDP in 1982 for a fiveyearperiod. Since <strong>the</strong> initiation of <strong>the</strong>project. much attention has been givento screening wheats for resistance to anumber of diseases and for greatertolerance to heat-related stresses; moreappropriate cultural practices are alsobeing developed for growing wheats in<strong>the</strong> major soil types found in <strong>the</strong>sewarmer. nontraditional wheat-growingareas.Discussions at this conference havefocused largely around two questions:• Can germplasm and cultural practicesbe developed that will make it feasibleto grow wheat in more tropicalenvironments than has been possibleto date?• It is economically sound to attempt todevelop wheats for commercialproduction in <strong>the</strong>se warmer areas?The first question relates primarily to<strong>the</strong> technical aspects of whe<strong>the</strong>r <strong>the</strong>necessary traits can be bred into wheatand whe<strong>the</strong>r suitable cultural practicescan be developed. Discussion on <strong>the</strong>second question has examined <strong>the</strong> likelycomparative economic advantage ofgroWing wheat in <strong>the</strong> warmer, tropicalareas versus groWing o<strong>the</strong>r crops, and<strong>the</strong> economics of satisfying consumerdemand for wheat products in suchareas through domestic production orthrough importation.

..342Developing Wheat Varietiesfor More Tropical AreasFor purposes of discussion, targettropical areas are described as thoseenvironments below 1000 meters inelevation and between 23°N and 23°Slatitudes; such environments are foundin 85 countries around <strong>the</strong> world. and57 of <strong>the</strong>m have an interest in domesticwheat production to satisfy at least partof <strong>the</strong>ir growing consumer demand. Thetwo major mega-environmental zoneswhere tropical wheat may be grown areincluded in two broad classifications:• The hothumid climates (in <strong>the</strong>cooler, drier months) (examples:Thailand, Philippines and Indonesia)• The hot. arid climates (examples:Sudan and Senegal)Wheat will need to be developed for bothof <strong>the</strong>se environments. as well as for <strong>the</strong>many macro-environmets within each of<strong>the</strong>se broad classifications.The technical problems of tropical wheatdevelopment can generally be dividedinto two research areas, cropimprovement (breeding and pathology)and crop management (productionagronomy and economics).Wheat production circumstances in<strong>the</strong>se more tropical locations are far toovariable to specify precisely <strong>the</strong>combination of traits needed: However.<strong>the</strong>re are common production factorsthat appear to be important for all of <strong>the</strong>tropical wheat areas:• Stable yield potentialAgronomic characteristics:Early vegetative VigorEarly maturityLodging resistanceHeat toleranceDrought toleranceResistance to various soil toxicities• Disease resistance• Insect resistance• Grain qualityThe major problems for <strong>the</strong> adaptationof wheat for tropical conditions aresummarized in Table 1.There is some hope of transferring to. wheat genetic resistance to diseasesfrom o<strong>the</strong>r species that are closely ordistantly related. The wide cross work ofCIMMYT cytogeneticists and of those ato<strong>the</strong>r institutions should prove useful inthis endeavor.Successful resistance work is beingcarried out on head scab diseases inBrazil. China and Mexico. However.resistance breeding alone will notovercome <strong>the</strong> problem of diseases. Acombination of genetic resistance (greator small). agronomic practices andchemical control will be necessary.Much research is needed for <strong>the</strong>development of various appropriatecombinations, and differentenvironments will likely require differentcombinations of factors. Combining allof <strong>the</strong> above-mentioned traits into one ormore varieties will probable take adecade or more of intense breeding andevaluation.Agronomic Problemsin More Tropical AreasThe major agronomic problems likely toface farmers who seek to produce wheatin more tropical environments are:• Soil types (latisols, sandy. low-fertilitysoils, soils with micro-nutrientdeficiencies. soils with high acidity)• Waterlogging (hard pans from ricefields in a wheat-rice rotation,deficiency or nonavailability ofnutrients)• Seedbed preparation and tillage• Stand establishment• Planting dates

343Table 1. Probleml for <strong>the</strong> edlPtation of what for tropiall conditionlllKl nriabilitynail" in existing..rmp....,BreedingHeat tolerance:In juvenile plantsIn <strong>the</strong> fruiting period-flowering to ripening (sometimes referredto as <strong>the</strong> "stay green" trait where stems and leaves remaingreen while grains are ripening)Drought tolerance, particularly late in <strong>the</strong> seasonEarlinessTolerance to acid soilsLodging resistanceDisease resistance:Sclerotium rolf.;;HelminthOlPorium complex which occurs in most of <strong>the</strong>tropics (Mehta of Brazil and Raemaekers of Zambiapointed out <strong>the</strong> difficulties of working with this disease)FUfJ8rium spp.Root rotLeaf blotchHead scabPowdery mildew-vegetativeLeaf rust, <strong>the</strong> most important of <strong>the</strong> rusts(stem and stripe rust are not often found)Xanthoma". campestri. and o<strong>the</strong>r spp. of bacteriaInsect resistance (<strong>the</strong> stem borer, semi-looper and armyworms, aphids, etc., are among <strong>the</strong> most importantinsects)Veriability•••••••••••••••No resistance known•••••••••No resistance known• Some variation exists•• Considerable variation exists••• Extensive variation exists

344• Weed control (appropriate herbicidesare not yet identified for <strong>the</strong> tropics)• Seed production and storage• Harvesting practices• Post-harvest technology (seed andgrain storage, insects and grainspoilage)Agronomy has played a tremendous rolein <strong>the</strong> increase in wheat production in<strong>the</strong> world today. But, from what hasbeen reported in this conference, <strong>the</strong>past inputs of agronomy are minorcompared to <strong>the</strong> requirements that willbe necessary for <strong>the</strong> successfulproduction of wheat for tropicalconditions. On-farm research andsubsequent extension education will becritical for <strong>the</strong> generation and transfer oftechnology to <strong>the</strong> tropical wheat farmer.CIMMYT's Crop ImprovementMethodologyCIMMYT screens a large number of lineseach year in Mexico in a shuttlebreeding program between Toluca andCiudad Obregon. Hundreds of <strong>the</strong> moreagronomically promising lines are <strong>the</strong>nscreened at Poza Rica (With a very hotenvironment) and Tlaltizapan (With amedium-hot environment) for heattolerance and helminthosporiumresistance. The best lines are <strong>the</strong>ngrouped into various internationalnurseries for helminthosporiumresistance, drought tolerance. heattolerance, early maturity. etc.• and aresent to multiple locations in <strong>the</strong> worldfor fur<strong>the</strong>r evaluation of <strong>the</strong> respectivetraits. This network of testing andevaluation. referred to as multilocationaltesting. allows for rapid assessmentunder target environments. Performancedata are returned to CIMMYT foranalysis and for <strong>the</strong> planning of newcrosses to combine <strong>the</strong> traits necessaryfor adaptation to tropical conditions.Breeding to combine high yield potentialand o<strong>the</strong>r favorable characters for <strong>the</strong>semore tropical environments willnecessitate a tremendous effort and willrequire <strong>the</strong>-cooperation andcollaboration of wheat scientists in manycountries. This multUocational conceptis a must for <strong>the</strong> development ofgermplasm for <strong>the</strong> tropics. We atCIMMYT hope that, upon your return toyour countries. all of you will be able toinspire your fellow scientists to join inthis challenging and Vitally importantresearch effort.Economics of Wheat Productionin More Tropical AreasMany tropical countries are consumingever-increasing amounts of wheat,virtually all of which is currently beingimported. These consumption andimportation trends give evidence ofpotential markets for domestic wheatproduction. Yet such countries are nottraditional wheat producers. and <strong>the</strong>yhave environmental conditions whichhave not heretofore been conSideredsuitable for <strong>the</strong> production of wheat, atemperate-climate crop.Because of this growing demand forwheat and wheat products innontraditional production areas, issuesof <strong>the</strong> allocation of research resourcesare being raised. In establishingpriorities for agricultural research. policymakers must consider a myriad ofconcerns. including economicdevelopment, income distribution. foodsecurity and foreign exchange. as well as<strong>the</strong> environment. One analyticalprocedure that can be used in thisprocess is that of comparativeadvantage, which indicates <strong>the</strong> ability ofvarious enterprises to contribute tonational income. A basic questionaddressed in comparative advantageanalysis is whe<strong>the</strong>r it is cheaper. interms of domestic resources. for acountry to import a product. such aswheat, or to produce it domestically.

345While efforts to develop wheatgennplasm and production technologiesfor more tropical environments are stillin <strong>the</strong> initial stages. <strong>the</strong> test ofcomparative advantage must be appliedat some stage to detennine whe<strong>the</strong>r thisresearch thrust is feasible. given <strong>the</strong>limited research resources available in<strong>the</strong> developing world. Some preliminaryeconomics research in Thailandindicates that. while wheat does not nowcompete with o<strong>the</strong>r alternative crops.with varieties better adapted to <strong>the</strong>environment and improved culturalpractices. it could become a commercialcrop in certain upland regions. Suchpreliminary evaluations. indicatingminimum yield levels needed to makewheat a competitive crop. provide uswith ecouragement that science can beput to work to make wheat a profitablecrop in areas in which it currently is notgrown.

8 _Appendix IComments on <strong>the</strong> <strong>Symposium</strong>o. de Sousa Rosa, Centro Nacional de Pesquisa de Trigo, PassoFundo, Rio Grande do Sui, BrazilThe importance of <strong>the</strong> United NationsDevelopment Programme's project on<strong>the</strong> development of wheat production fumore tropical environments is fullyrecognized. In Brazil, technologiesdeveloped for <strong>the</strong> production of wheatunder tropical and subtropicalconditions have also been of value forstimulating <strong>the</strong> growth of soybeanproduction and have led toexperimentation with o<strong>the</strong>r crops inareas that were never before consideredappropriate for agriculture. Thus,valuable results can be expected from<strong>the</strong> project, not only in <strong>the</strong> developmentof wheat production. but also in itssecondary effects on <strong>the</strong> cultivation ofo<strong>the</strong>r crops that may be of equal or evengreater importance.UNDP's choice of CIMMYT to head <strong>the</strong>project was a good one. The resultsalready obtained by CIMMYT in <strong>the</strong>improvement of wheat production in <strong>the</strong>world are a proof of this, as are thosewhich can be expected in <strong>the</strong> future.Many countries which produce wheat intropical and subtropical environmentshave already invested great amounts in<strong>the</strong> development of technology. Theseexisting technologies can be ofimportance in <strong>the</strong> CIMMYT program andcan be rapidly adopted by o<strong>the</strong>rcountries with similar problems. It isimportant that researchers in thosecountries participate in <strong>the</strong> efforts thatUNDP and CIMMYT are exerting toincrease <strong>the</strong> production of tropicalwheat, not only as cooperators but withspecific responsibilities for portions of<strong>the</strong> total research program. This can beaccomplished through collaborativeresearch with institutions in <strong>the</strong> variouscountries. The participation of <strong>the</strong>senational institutions in research projectsof international scope could stimulate<strong>the</strong>m to a broader participation; it wouldalso be an important factor for insuring<strong>the</strong> continuity and growth of <strong>the</strong>programs in which <strong>the</strong>y have alreadyinvested.Possibly <strong>the</strong> defmition of <strong>the</strong> tropicalwheat area should be revised to permit<strong>the</strong> inclusiop of subtropical productionareas outside <strong>the</strong> limits of 23°N and23°8 latitudes, areas which, because ofecological characteristics. are as limitedor even more limited for <strong>the</strong> grOwing ofwheat than are many of <strong>the</strong> tropicalareas.Within <strong>the</strong> program for <strong>the</strong> developmentof tropical wheat, <strong>the</strong> difference betweentechnologies appropriate for rainfed andfor irrigated farming systems is verygreat. The compleXities of <strong>the</strong> minfedsystems are much greater and,<strong>the</strong>refore, <strong>the</strong> two areas might beconsidered separately, with differentcourses of action being followed for eachof <strong>the</strong>m.This symposium has been of great valuefor <strong>the</strong> future development of tropicalwheat. and <strong>the</strong> program has beenefficiently planned and carried out. Itsrepetition in three or four years willfur<strong>the</strong>r benefit <strong>the</strong> development of wheatfor <strong>the</strong> mor:e tropical environments.

347Appendix IIWheat Pests and Diseasesc. James, Deputy Director General, CIMMYT, MexicoCIMMYT recognizes <strong>the</strong> importance of<strong>the</strong> many activities related to pests anddiseases that are currently beingconducted in Latin America, Mrica andAsia.Given <strong>the</strong> well-documented interactionbetween environment, plant andpathogen. and <strong>the</strong> important changesthat occur when <strong>the</strong> status of one of<strong>the</strong>m is changed. CIMMYT and itscollaborators should take advantage ofthis opportunity to monitor andinvestigate <strong>the</strong> behavior of pathogensand <strong>the</strong>ir interaction with wheat grownin a tropical environment. Theopportunity is unique because wheat,<strong>the</strong> world's major crop, is being movedinto a totally different environment.Fundamental questions should be posedwhich will generate new knowledge tobe shared with <strong>the</strong> global scientificcommunity and used to evolve apractical strategy for managing pestsand diseases on wheat grown undertropical conditions.Under tropical conditions, <strong>the</strong> two majorfactors that wlll make it more difficult tocontrol pathogens are:• Temperature-For most pathogens,growth is a function of temperature;<strong>the</strong> higher <strong>the</strong> temperature, <strong>the</strong>higher <strong>the</strong> growth rate. Consequently,compared with temperate climates.epidemics wlll progress more rapidly,and a more effective and fasterdecision-making mechanism will berequired to control epidemics.• Humidity-Under some tropicalconditions, humidity is significantlyhigher for longer durations. For mostpathogens, this wlll result in highersporulation, which in tum results inmore inoculum, more spread andfaster-growing epidemics.Since <strong>the</strong>se two major factors,temperature and humidity, canindependently or additively increase <strong>the</strong>growth rate of epidemics, it willprobably be more difficult to managediseases in tropical environments. It ishighly likely that integrated pestmanagement techniques, utilizing morethan one control method simultaneously,wlll have to be used to achievesatisfactory levels of disease and pestcontrol. For example, <strong>the</strong>re may have tobe more effective levels of tolerance, inconjunction with <strong>the</strong> use of systemicfungicides in seed dressings to serve asantlsporulantslsterllants.Continued work on pests andpathogens on wheat grown in a tropicalenvironment can also make animportant contribution in two majorareas:• New information of a fundamentalnature on important phenomenonWe have little information on <strong>the</strong>effect of temperature on <strong>the</strong> rate ofmutation. If increased temperature

348increases mutation rate, this will beextremely important, sincemutations are currently responsiblefor <strong>the</strong> evolution of new races ofpathogens which erode resistanceunder temperate conditions. A studyto assess <strong>the</strong> abUity of unspecializedpathogens to become specialized andmore destructive would also beimportant.• Practical strategy for managingdiseases of wheat grown in a tropicalenvironment-The avaUabUity ofnew information on <strong>the</strong> behavior ofpathogens can be generated throughcollaborative researCh projects. and<strong>the</strong>n applied to <strong>the</strong> development ofapractical strategy for controllingdiseases under field conditions. Theoverall goal of increasing wheatproductivity and production in atropical environment remains <strong>the</strong>principal objective of <strong>the</strong> study, withall o<strong>the</strong>r investigations contributingto that goal.

349Appendix IIIParticipants. <strong>Symposium</strong> on Wheats for More Tropical EnvironmentsSeptember 24-28. 1984ArgentinaIng. Isidro R. CettourEstaci6n Experimental Regional AgricolaInstituto Nacional de TecnologiaAgropecuariaCasilla de Correos 164-3700Presidencia Roque Saenz PefiaChaco, ArgentinaIng. Beatriz A. PerezEstaci6n Experimental Regional AgricolaInstituto Nacional de TecnologiaAgropecuariaCasilla de Correos 164-3700Presidencia Roque Saenz PefiaChaco, ArgentinaAustraliaDr. Ralph A. FischerDivision of Plant IndustryCommonwealth Scientific andIndustrial OrganisationP.O. Box 1600Canberra. Australia 2601Dr. David R. WoodruffSenior Plant PhysiologistQueensland Wheat Research InstituteP.O. Box 5282Toowoomba. QueenslandAustralia 4350BangladeshMr. Islam AshrafulPrincipal Scientific OfficerRegional Agricultural Research StationIshurdi, Pabna, BangladeshBoliviaIng. Jose Abela G.Corporaci6n Gestora del ProyectoAbapo-IzozogCasilla 1281Santa Cruz, BoliviaIng. Rolando Paz F.Director EjecutivoCentro de Investigaci6nAgricola TropicalAvenida del Ejercito 131Casilla 247Santa Cruz, BoliviaIng. Casiano Quintana C.Centro de InvestigacionAgricola TropicalAvenida del EJercito 131Casilla 247Santa Cruz, BoliviaBrazllDr. Gilberto C. LuzzardiFaculdade de Agronomia Eliseu MacielUniversidade Federal de Pelotas96100 Pelotas. Rio Grande do Sui, BrazilDr. Yeshwant R. MehtaInstituto Agronomico do ParanaCaixa Postal 133186100 Londrina, Parana, BrazilIng. Osmar MuzilliInstituto Agronomico do ParanaCaixa Postal 133186100 Londrina. Parana, BrazilDr. Ady R. da SilvaMinisterio de AgriculturaProvarzeas National70374 Brasilia, D.F., BrazilDr. Ottoni de Sousa RosaCentro Nacional de Pesquisa de TrigoCaixa Postal 56999100 Passo Fundo.Rio Grande do SuI, Brazil

CanadaMr. John T. SykesAgricultural SpecialistNatural Resources DivisionCanadian InternationalDevelopment Agency200 Promenade du PortageHull. Quebec. Canada KIA OG4(P.M.B. 1044 Zaria. Nigeria)Costa RicaIng. Carlos A. Salas F.Estaci6n Experimental Fabio BaudrltMorenoUniversidad de Costa RicaAlajuela. Costa RicaEcuadorDr. Jaime E. Tola C.Estaci6n Experimental Santa CatalinaInstituto Nacional de InvestigacionesAgropecuariasCasUla Postal 340Quito. EcuadorGermanyDr. David WoodGerman Agency for TechnicalCooperation (GTZlPostfach 518006236 Eskborn. West GermanyIndiaDr. S.B. SinghGeneral Manager. Seed ProductionU.P. Seeds and Tarat DevelopmentCorporationHaldi (Pantnagarl. Na1nitalPin-263146. IndiaDr. Joginder P. TandonProject Director. Wheat ProgramIndian Agricultural Research InstituteNew Delhi 110012. IndiaDr. Yogendra M. UpadhyayaCoordinator. Regional StationWheat BreedingIndian Agricultural Research Institl.!-teIndore. Madhya Pradesh 452001. IndiaIndonesiaDr. Tohar DanakusumaWheat CoordinatorSukamandi Food Crops ResearchInstituteP.O. Box 11Cikampek. Sukamandi.West Java. IndonesiaMexicoBioI. Eduardo Castafieda S.Sanidad VegetalSecretaria de Agricultura y RecursosHidrauUcosHamburgo 63. 5° Piso06600 Mexico. D.F.Dr. Arturo Hernandez S.Campo Agricola ExperimentalValle de MexicoCentro de Investigaciones de laMesa CentralCampo EI HomoApartado Postal 1056230 Chapingo. MexicoIng. J. Jesus Martinez S.Campo Agricola ExperimentalValle del YaquiCentro de Investigaciones Agricolas delNoroesteApartado Postal 51585000 Ciudad Obregon. Sonora. MexicoDr. Ernesto 8amayoa A.Sub-Director de Investigaci6nInstituto Nacional de InvestigacionesAgricolasApartado Postal 51585000 Ciudad Obregon. Sonora. MexicoDr. Jose A. ValenciaDirector. Centro de InvestigacionesAgricolas del NoroesteApartado Postal 51585000 Ciudad Obregon. Sonora. MexicoNe<strong>the</strong>rlandsDr. Ronald W. StubbsInstitute for Research in Plant Diseases(lPOlP.O. Box 90606709 Wageningen. Ne<strong>the</strong>rlands

351NigeriaMr. Ahmed M. FalakiResearch FellowlLecturerDepartment of AgronomyInstitute for Agricultural ResearchAhmadu Bello UniversityP.M.B.I044Zaria, NigeriaDr. Abraham O. OgungbileDepartment of AgriculturalEconomics and Rural SociologyInstitute for Agricultural ResearchAhmadu Bello UniversityP.M.B.I044Zaria, NigeriaMr. Francis C. OrakwueWheat Breeder/Research FellowDepartment of Plant ScienceInstitute for Agricultural ResearchAhmadu Bello UniversityP.M.B.I044Zaria, NigeriaPakistanDr. Manzoor A. BajwaDirector GeneralAyub Agricultural Research InstituteFaisalabad. PakistanDr. NekM.K. TareenDeputy DirectorAgricultural Research InstituteSariab Quetta. PakistanPeople's Republic of ChinaMr. Liu Zong-ZhenPlant Protection InstituteShanghai Academy of AgriculturalSciencesShanghai, People's Republic of ChinaMr. Zhou ChaofeiWheat BreederInstitute of Food CropsJiangsu Academy of AgriculturalSciencesNanjing, Jiangsu 210014People's Republic of ChinaPhilippinesDr. Filomena F. CamposDirector of ResearchCentral Luzon State UniversityMunoz. Nueva Ecija, PhilippinesDr. Virgilio R. CarangalCoordinator, Asian Cropping SystemsNetworkInternational Rice Research InstituteP.O. Box 933Manila, PhilippinesDr. Crisanto R. EscafioChairman, Management ComitteeWheat Pilot Production ProjectCrops Research DepartmentPhilippine Council for Agriculture andResources Research anp DevelopmentLos Banos, Laguna, PhilippinesDr. Delfin B. LapisInstitute for Plant BreedingUniversity of <strong>the</strong> Philippines atLos BanosLos Banos, Laguna. PhilippinesDr. Abercio RotorNational Food Authority101 E. Rodriguez Sr. AvenueQuezon City, Manila, PhilippinesPolandDr. Andrzej SzolkowskiMain Breeding Station for Rye, Wheatand TriticaleP.O. Box 05-660Warka, PolandSudanDr. Faisal M. AliNational Coordinator, WheatAgricultural Research CorporationWad Medani, SudanDr. Abdalla B. ElahmadiWheat BreederPlant Breeding SectionAgricultural Research CorporationGezira R~searchStationWad Medani, Sudan

3MMr. Mohamed A. GallabiNew Halfa Agricultural CorporationP.O. Box 538Khartoum, SudanMr. Mohamed S. MohamedNew Halfa Agricultural StationP.O. Box 17New Halfa, SudanThailandDr. Phattakun ChandhanamuttaWheat CoordinatorRice Research InstituteDepartment of AgricultureKasetsart UniversityBangkhen, Bangkok 10900, ThailandMr. John G. ConnellLocal Utilization ProgramSou<strong>the</strong>ast Asian Wheat ProgranlCIMMYTP.O. Box 9-188Bangkok,ThailandDr. Supote DechatesOffice of Agricultural EconomicsMinistry of Agriculture andCooperativesRatcha Damnern RoadBangkok, ThailandDr. Benjavan RerkasemMultiple Cropping ProjectFaculty of AgricultureChiang Mai UniversityChiang Mai, ThailandUSADr. Warren E. KronstadDepartment of Crop ScienceAgriculture Hall 138Oregon State UniversityCorvallis, Oregon 97331. USAMr. WUliam T. Mashlersenior DirectorDivision for Global and InterregionalProjectsUnited Nations DevelopmentProgrammeOne UN PlazaNew York, N.Y. 10017. USADr. Milton McDanielAssociate ProfessorSoil and Crop Sciences DepartmentTexas A and M UniversityCollege Station, Texas 77843, USAZambiaMr. Ted V. AngenSoils SurveyorZambia-Canada Wheat Research ProjectP.O. Box 31896Lusaka, ZambiaMr. Balvindar S. AulakZambia-Canada Wheat Research ProjectP.O. Box 31896Lusaka. ZambiaMr. James E. BrandlePlant BreederZambia-Canada Wheat Research ProjectMount Makulu Research StationPrivate Bag 7Chilanga, ZambiaDr. Richard LittleTeam LeaderZambia-eanada Wheat Research ProjectMount Makulu Research StationPrivate Bag 7Chilanga. ZambiaMr. Gabriel C. MusaPlant BreederZambia-eanada Wheat Research ProjectMount Makulu Research StationPrivate Bag 7Chilanga, ZambiaMr. Romain RaemaekersPlant PathologistBelgian Development CooperationMount Makulu Research StationPrivate Bag 7Chilanga, Zambia

353CIMMYT Staff. MexicoMr. Robert D. HavenerDirector GeneralDr. W. Clive JamesDeputy Director GeneralDr. Byrd C. CurtisDirector. Wheat ProgramDr. Arthur R. KlattAssociate DirectorWheat ProgramDr. Donald L. Winkelmann-Director. Economics ProgramDr. Arnoldo AmayaIndustrial Quality LaboratoryDr. Osman AbdallaPost-Doctoral. Wheat ProgramDr. Girma BekeleWheat PathologistDr. Pedro BrajcichDurum Wheat BreederDr. Hans BraunPost-Doctoral. Wheat ProgramMr. Neil BredinData Processing ServicesWheat ProgramDr. Peter BurnettWheat PathologistDr. Norma CashionPost-Doctoral. Wheat ProgramDr. Walter A.J. de MillianoPost-Doctoral. Wheat ProgramDr. Paul Fox.Post-Doctoral. Wheat ProgramIng. Lucy I. GilchristWheat PathologistDr. Homer M. HepworthAgronomist. Head-Training ProgramDr. A. MUjeeb-KaziWheat CytologistDr. Gerbrand KingmaTraining Officer-BreedingDr. E. Bronson KnappTraining Officer-Production AgronomyDr. Pierre MalvoisinAssociate Scientist. Wheat ProgramDr. Mahmood OsmanzaiPost-Doctoral. Wheat ProgramDr. Rob,rto J. PefiaPost-DOctoral. Wheat ProgramDr. J. Michael PrescottWheat'PathologistDr. Sanjaya RajaramBread Wheat BreederIng. Ricardo RodriguezWheat Germplasm SpecialistDr. Eugene SaariWheat PathologistJBreederDr. Ayla SencerCurator. Wheat Germplasm BankDr. Ravi P. SinghPost-Doctoral. Wheat ProgramMr. Douglas TannerAgronomist. Wheat ProgramMr. Leon van BeuningenDutch Associate ScientistWheat ProgramMr. M.C. van den BergAssociate Scientist. Wheat ProgramDr. George VarugheseTriticale BreederMr. Tiff HarrisWriter/Editor. Wheat Program

3MDr. Reynaldo VillarealBread Wheat BreederDr. Stephen R. WaddingtonPost-Doctoral, Wheat ProgramDr. Elizabeth J. WarhamAssociate Scientist, Wheat ProgramDr. Masao YoshidaAssociate Scientist, Wheat ProgramCIMMYT Outreach StaffDI:. Larry ButlerWheat Program, CIMMYT-BARIJoydebpur, Dakha, BangladeshDr. Derek ByerleeEconomics Program, CIMMYTP.O. Box 1237Islamabad, PakistanDr. H. Jesse DubinWheat Program, CIMMYT·INIAPApartado 2600Quito, EcuadorDr. Santiago FuentesWheat Program, CIMMYTc/o Ministerio da Agricultura e PescasApartado 212031131 Lisbon, PortugalDr. Mengu GuierWheat Program, CIMMYT-BARIJoydebpur, Dakha, BangladeshDr. Larry HarringtonEconomics Program, CIMMYTP.O. Box 9-188Bangkok 10900, ThailandDr. Peter HobbsWheat Program, CIMMYTP.O. Box 1237Islamabad, PakistanDr. Christoph E. MannWheat Program, CIMMYTSou<strong>the</strong>ast Asia Regional ProgramP.O. Box 9-188Bangkok 10900, ThailandDr. Mat<strong>the</strong>w McMahonWheat Program, CIMMYT-INIACasilla5427Santiago, ChileDr. David A. SaundersWheat Program, CIMMYTP.O. Box 9-188Bangkok 10900, Thailand

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