Septoria and Stagonospora Diseases of Cereals - CIMMYT ...

Septoria and 

Stagonospora 

Diseases of Cereals: 

A Compilation of Global Research 

M. van Ginkel, 

A. McNab, 

and J. Krupinsky, 

editors

Septoria and Stagonospora 

Diseases of Cereals: 

A Compilation 

of Global Research 

Proceedings of the Fifth 

International Septoria Workshop 

September 20-24, 1999 

CIMMYT, Mexico 

M. van Ginkel, A. McNab, and J. Krupinsky, editors 

Dedicated to the memory of 

Dr. Zahir Eyal

ii 

The Organizing Committee expresses it sincere thanks to the Workshop Sponsors: 

Bayer de México, S.A., and Zeneca Mexicana, S.A. 

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© International Maize and Wheat Improvement Center (CIMMYT) 1999. Responsibility for this 

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Printed in Mexico. 

Correct citation: van Ginkel, M., A. McNab, and J. Krupinsky, eds. 1999. Septoria and Stagonospora 

Diseases of Cereals: A Compilation of Global Research. Mexico, D.F.: CIMMYT. 

ISBN: 970-648-035-8 

AGROVOC descriptors: Wheats; Triticum; Triticum aestivum; Soft wheat; Triticum durum; Hard 

wheat; Winter crops; Plant diseases; Fungal diseases; Septoria; Stagonospora; Blotches; 

Mycosphaerella; Epidemiology; Plant breeding; Selection; Disease resistance; Genetic control; Gene 

location; Cultural control; Plant response; Research projects 

Additional Keywords: Triticum tauschii 

AGRIS category codes: H20 Plant Diseases 

F30 Plant Genetics and Breeding 

Dewey decimal classification: 632.4 

Additional information on CIMMYT is available on the WorldWideWeb at: www.cimmyt.cgiar.org.

Table of Contents 

vi In Memoriam, Dr. Zahir Eyal 

vii Foreword 

1 Opening remarks 

1 Historical Aspects and Future Challenges of an International Wheat Program 

S. Rajaram 

19 Session 1: Pathogen Biology 

19 Biology of the Septoria/Stagonospora Pathogens: An Overview 

A.L. Scharen 

23 Molecular Analysis of a DNA Fingerprint Probe from Mycosphaerella graminicola 

S.B. Goodwin and J.R. Cavaletto 

26 Characterization of Septoria tritici Variants and PCR Assay for Detecting Stagonospora nodorum and 

Septoria tritici in Wheat 

S. Hamza, M. Medini, T. Sassi, S. Abdennour, M. Rouassi, A.B. Salah, M. Cherif, R. Strange, and M. 

Harrabi 

32 Populations of Septoria spp. Affecting Winter Wheat in the Forest-Steppe Zone of the Ukraine 

S. Kolomiets 

34 Septoria passerinii Closely Related to the Wheat Pathogen Mycosphaerella graminicola 

S.B. Goodwin and V.L. Zismann 

37 Septoria/Stagonospora Leaf Spot Diseases on Barley in North Dakota, USA 

J.M. Krupinsky and B.J. Steffenson (poster) 

39 Interrelations among Septoria tritici Isolates of Varying Virulence 

S. Ezrati, S. Schuster, A. Eshel, and Z. Eyal (poster) 

41 Session 2: The Infection Process 

41 Stagonospora and Septoria Pathogens of Cereals: The Infection Process 

B.M. Cunfer 

46 Aggressiveness of Phaeosphaeria nodorum Isolates and Their In Vitro Secretion of Cell-Wall- 

Degrading Enzymes 

P. Halama, F. Lalaoui, V. Dumortier, and B. Paul 

50 Growth of Stagonospora nodorum Lesions 

A.M. Djurle (poster) 

51 Session 3A: Host-Parasite Interactions 

51 Genetic Control of Avirulence in Mycosphaerella graminicola (Anamorph Septoria tritici) 

G.H.J. Kema and E.C.P. Verstappen 

53 Cytogenetics of Resistance of Wheat to Septoria Tritici Leaf Blotch 

L.S. Arraiano, A.J. Worland, and J.K.M. Brown 

54 A Possible Gene-for-Gene Relationship for Septoria Tritici Leaf Blotch Resistance in Wheat 

P.A. Brading, G.H.J. Kema, and J.K.M. Brown 

56 Diallel Analysis of Septoria Tritici Blotch Resistance in Winter Wheat 

X. Zhang, S.D. Haley, and Y. Jin 

59 Analysis of the Septoria Monitoring Nursery 

L. Gilchrist, C. Velazquez, and J. Crossa 

63 Session 3B: Host Parasite Interactions 

63 Host – Parasite Interactions: Stagonospora nodorum 

E. Arseniuk and P.C. Czembor 

71 Identification of a Molecular Marker Linked to Septoria Nodorum Blotch Resistance in Triticum 

tauschii Using F2 Bulked Segregant 

N.E.A. Murphy, R. Loughman, R. Wilson, E.S. Lagudah, R. Appels, and M.G.K. Jones 

74 Inheritance of Septoria Nodorum Blotch Resistance in a Triticum tauschii Accession Controlled by a 

Single Gene 

N.E.A. Murphy, R. Loughman, R. Wilson, E.S. Lagudah, R. Appels, and M.G.K. Jones 

77 Session 4: Population Dynamics 

77 Population Genetics of Mycosphaerella graminicola and Phaeosphaeria nodorum 

B.A. McDonald, C.C. Mundt, and J. Zhan 

83 Characterization of Less Aggressive Stagonospora nodorum Isolates from Wheat 

E. Arseniuk, H.S. Tsang, J.M. Krupinsky, and P.P. Ueng 

85 A Vertically Resistant Wheat Selects for Specifically Adapted Mycosphaerella graminicola Strains 

C. Cowger, C.C. Mundt, and M.E. Hoffer 

iii

iv 

87 Genetic Variability in a Collection of Stagonospora nodorum Isolates from Western Australia 

N.E.A. Murphy, R. Loughman, E.S. Lagudah, R. Appels, and M.G.K. Jones 

90 Mating Type-Specific PCR Primers for Stagonospora nodorum Field Studies 

R.S. Bennett, S.-H. Yun, T.Y. Lee, B.G. Turgeon, B. Cunfer, E. Arseniuk, and G.C. Bergstrom (poster) 

93 Session 5: Epidemiology 

93 Epidemiology of Mycosphaerella graminicola and Phaeosphaeria nodorum: An Overview 

M.W. Shaw 

98 Spore Dispersal of Leaf Blotch Pathogens of Wheat (Mycosphaerella graminicola and Septoria tritici) 

C.A. Cordo, M.R. Simón, A.E. Perelló, and H.E. Alippi 

102 Epidemiology of Seedborne Stagonospora nodorum: A Case Study on New York Winter Wheat 

D.A. Shah and G.C. Bergstrom 

108 Sessions 6A and 6B: Cultural Practices and Disease Management 

108 Influence of Cultural Practices on Septoria/Stagonospora Diseases 

J.M. Krupinsky 

111 Disease Management Using Varietal Mixtures 

C.C. Mundt, C. Cowger, and M.E. Hoffer 

117 Session 6C: Breeding for Disease Resistance 

117 Breeding for Resistance to the Septoria/Stagonospora Blights of Wheat 

M. van Ginkel and S. Rajaram 

127 Breeding for Resistance to Septoria and Stagonospora Blotches in Winter Wheat in the United States 

G. Shaner 

131 Septoria tritici Resistance of Wheat Cultivars at Different Growth Stages 

M. Díaz de Ackermann, M.M. Kohli, and V. Ibañez 

134 Septoria tritici Resistance Sources and Breeding Progress at CIMMYT, 1970-99 

L. Gilchrist, B. Gomez, R. Gonzalez, S. Fuentes, A. Mujeeb-Kazi, W. Pfeiffer, S. Rajaram, R. 

Rodriguez, B. Skovmand, M. van Ginkel, and C. Velazquez (Field presentation) 

140 Selecting Wheat for Resistance to Septoria/Stagonospora in Patzcuaro, Michoacan, Mexico 

R.M. Gonzalez I., S. Rajaram, and M. van Ginkel 

145 Varieties and Advanced Lines Resistant to Septoria Diseases of Wheat in Western Australia 

R. Loughman, R.E. Wilson, I.M. Goss, D.T. Foster, and N.E.A. Murphy 

148 Field Resistance of Wheat to Septoria Tritici Leaf Blotch, and Interactions with Mycosphaerella 

graminicola Isolates 

J.K.M. Brown, G.H.J. Kema, H.-R. Forrer, E.C.P. Verstappen, L.S. Arraiano, P.A. Brading, E.M. Foster, 

A. Hecker, and E. Jenny 

150 Using Precise Genetic Stocks to Investigate the Control of Stagonospora nodorum Resistance in Wheat 

C.M. Ellerbrook, V. Korzun, and A.J. Worland (poster) 

154 Evaluating Triticum durum x Triticum tauschii Germplasm for Resistance to Stagonospora nodorum 

L.R. Nelson and M.E. Sorrells (poster) 

156 Sources of Resistance to Septoria passerinii in Hordeum vulgare and H. vulgare subsp. spontaneum 

H. Toubia-Rahme and B.J. Steffenson (poster) 

159 Soft Red Winter Wheat with Resistance to Stagonospora nodorum and Other Foliar Pathogens 

B.M. Cunfer and J.W. Johnson (poster) 

160 Partial Resistance to Stagonospora nodorum in Wheat 

C.G. Du, L.R. Nelson, and M.E. McDaniel (poster) 

163 Comparison of Methods of Screening for Stagonospora nodorum Resistance in Winter Wheat 

D.E. Fraser, J.P. Murphy, and S. Leath (poster) 

167 Response of Winter Wheat Genotypes to Artificial Inoculation with Several Septoria tritici 

Populations 

M. Mincu (poster) 

170 Comparison of Greenhouse and Field Levels of Resistance to Stagonospora nodorum 

S.L. Walker, S. Leath, and J.P. Murphy (poster) 

173 Session 6D: Chemical Control 

173 Adjusting Thresholds for Septoria Control in Winter Wheat Using Strobilurins 

L.N. Jørgensen, K.E. Henriksen, and G.C. Nielsen 

177 Concluding Remarks 

177 The Septoria/Stagonospora Blotch Diseases of Wheat: Past, Present, and Future 

Z. Eyal (paper presented by A.L. Scharen) 

183 List of Participants

In Memoriam, Dr. Zahir Eyal 

Our friend and colleague, Professor Zahir Eyal, died Friday, July 30, 1999. Zahir was 

intimately involved in all of the International Septoria Workshops, from the first in 1976 held in 

Griffin, Georgia, USA, until the fifth, and present, one held in CIMMYT, Mexico. He put forward 

his many ideas for program and participants in a forceful, but thoughtful way, and was able to 

settle disputes with good humor and a smile. Until the last few days of his life, Dr. Eyal 

continued to work on plans for this Septoria/Stagonospora workshop. 

After finishing agricultural high school in Israel, Zahir went to the USA, where he earned his 

B.Sc. degree from Oklahoma State University and his Ph.D. from Rutgers. This was followed by a 

post-doctoral term at Purdue, where he studied with Jack Schafer and the late Ralph Caldwell. 

His work on septoria of cereals began when he joined the Department of Botany at Tel Aviv 

University in 1967. He developed an integrated program of fundamental and applied research 

aimed at minimizing the economic impact of cereal pathogens, particularly Septoria tritici, on 

production. He reached out to colleagues in many countries and to international organizations, 

most especially CIMMYT, for cooperation. Over the years, Zahir contributed greatly to those 

programs. During his tenure at Tel Aviv University, Professor Eyal served two terms as Head of 

the Department of Botany (1984-87 and 1992-94). 

Professor Eyal was an enthusiastic teacher, well-loved by students, both undergraduate and 

graduate. He taught in English or in Hebrew with equal facility, sharing his knowledge and 

insights with students and faculty during two sabbaticals at Montana State University and at 

several other institutions. The numerous publications he authored with his students and the 

important posts those students occupy today attest to the excellence of his teaching abilities. 

Zahir’s research and outreach programs incorporated ideas that were new to his country; 

they were solidly anchored in basic science and innovative to the end. These programs not only 

improved wheat production in Israel but had positive effects on cereal improvement programs 

throughout the world. At the time of his death, Professor Eyal was Director of the Institute for 

Cereal Crop Improvement at Tel Aviv University, where germplasm of wild ancestors of 

cultivated small grains are being preserved, characterized, and utilized in breeding improved 

cultivars. 

Dr. Eyal’s contributions to research, teaching, university administration, and international 

agriculture are many and far reaching. He received the Hazera Seed Co. Melamed Award in 1968, 

the A.C. Cohen Award in 1978, and in 1995 was made a Fellow of the American 

Phytopathological Society. Professor Eyal served as President of the Israeli Phytopathological 

Society from 1979 to 1982. He will be fondly remembered and sadly missed by his multitude of 

friends, colleagues, and students throughout the world. 

v

vi 

Foreword 

In the mid-1970s the idea of holding a septoria workshop began to take hold among a small 

group of scientists in the USA. They were interested in exchanging ideas and finding ways to 

manage the septoria diseases that affect wheat and other cereals all over the world. The first 

workshop was organized in a matter of a few months and held in Griffin, Georgia, in 1976. 

Among the 50 scientists who attended were a few researchers from outside the US. The 

enthusiasm of that first workshop led to the development of the second, which was a truly 

international meeting attended by more than 100 scientists from many countries, held in 

Bozeman, Montana, in 1983. 

Since then, international septoria workshops have been held about every five years: in 

Zurich, Switzerland, in 1989; in Radzikow, Poland, in 1994; and this year at CIMMYT in El 

Batan, Mexico. Each workshop has expanded the network of scientists who share their 

knowledge and pose the many questions that remain to be solved about these diseases and their 

management. 

The Zurich workshop had increased participation by workers from Europe and Africa. The 

Radzikow workshop brought increased participation from scientists in eastern Europe. The early 

workshops focused on the biology of the pathogens and breeding strategies, subjects in which 

there remain many unanswered questions. The 1994 workshop and the current one emphasize 

molecular approaches to the genetics of the pathogens. 

The Fifth International Workshop provides another opportunity to focus on the Septoria/ 

Stagonospora diseases, but also to see them in the context of the worldwide programs of 

CIMMYT, which emphasize collaboration with developing countries with the aim of developing 

stable high yielding wheat varieties that possess durable resistance to the diseases. 

This workshop also gives us the opportunity to remember our friend and colleague, Zahir 

Eyal, who passed away not long ago. An integral part of the program development process and 

the discussions at each workshop, he organized the scientific program for this workshop as well. 

Zahir Eyal was an enthusiastic supporter of the septoria workshops and the international 

exchange of ideas. He will be missed. 

We would like to express our appreciation for the efforts of Ravi Singh, Maarten van Ginkel, 

and Linda Ainsworth, who organized the workshop. We wish to thank Diana Godínez, María 

Luisa Varela, and Laura Rodríguez for managing the logistical support. We also recognize the 

efforts of Arnoldo Amaya, María Garay, Lucy Gilchrist, Monique Henry, Gilberto Hernández, 

Reynaldo Villareal, Juan José Joven, Marcelo Ortíz, Eliot Sánchez, Kelly Cassaday, Miguel 

Mellado, Wenceslao Almazán, and Antonio Luna, as well as many other members of CIMMYT 

staff who contributed to the success of this event. 

The International Organizing Committee 

September 21, 1999

Opening Remarks 

Historical Aspects and Future Challenges of an 

International Wheat Program 

S. Rajaram 

Wheat Program, CIMMYT, El Batan, Mexico 

I am immensely honored and grateful to the organizing committee of the 5 th International Septoria Workshop for asking 

me to deliver this lecture in the opening session. Even though my presentation is very broad and covers many issues, I assure 

you that I have been involved in breeding for resistance to septoria tritici blotch for at least 25 years, with some remarkable 

success. In this attempt, I would like to recognize the contribution of Prof. Zahir Eyal, who served as a consultant on septoria 

issues to CIMMYT in the 1970s and 1980s. Indeed, he and I have some common intellectual roots through Prof. Ralph 

Caldwell of Purdue University. Prof. Eyal’s untimely death and departure from the scientific community is a loss to us all. I 

dedicate this opening lecture to him. 

Wheat is the most widely 

grown and consumed food crop in 

the world. It is the staple food of 

nearly 35% of the world 

population, and demand for wheat 

will grow faster than for any other 

major crop. The forecasted global 

demand for wheat in the year 2020 

varies between 840 (Rosegrant et 

al., 1995) to 1050 million tons 

(Kronstad, 1998). To reach this 

target, global production will need 

to increase 1.6 to 2.6% annually 

from the present production level 

of 560 million tons. Increases in 

realized grain yield have provided 

about 90% of the growth in world 

cereal production since 1950 

(Mitchell et al., 1997) and by the 

first decade of the next century 

most of the increase needed in 

world food production must come 

from higher absolute yields 

(Ruttan, 1993). For wheat, the 

global average grain yield must 

increase from the current 2.5 t/ha 

to 3.8 t/ha. In 1995, only 18 

countries world worldwide had 

average wheat grain yields of more 

than 3.8 t/ha, the majority located 

in Northern Europe (CIMMYT, 

1996). 

The formidable challenge to 

meet this demand is not new to 

agricultural scientists who have 

been involved in the development 

of improved wheat production 

technologies for the past half 

century. For all developing 

countries, wheat yields have grown 

at an average annual rate of over 

2% between 1961 and 1994 

(CIMMYT, 1996). In Western 

Europe and North America the 

annual rate of growth for wheat 

yield was 2.7% from 1977 to 1985, 

falling to 1.5% from 1986 to 1995. 

Recent data have indicated a 

decrease in the productivity gains 

being achieved by major wheat 

producing countries (Brown, 1997). 

In Western Europe, where the 

highest average wheat grain yield 

is obtained in the Netherlands 

(8.6 t/ha), yield increased from 5 to 

6 t/ha in five years, but it took 

more than a decade to raise yields 

from 6 to 7 t/ha. Worldwide, 

annual wheat grain yield growth 

decreased from 3.0% between 1977- 

1985, to 1.6% from 1986-1995, 

excluding the USSR (CIMMYT, 

1996). Degradation of the land 

resource base, together with a 

slackening of research investment 

and infrastructure, have 

1 

contributed to this decrease 

(Pingali and Heisey, 1997). Whether 

production constraints are affected 

by physiological or genetic limits is 

hotly debated, but future increases 

in food productivity will require 

substantial research and 

development investment to 

improve the profitability of wheat 

production systems through 

enhancing input efficiencies. Due to 

a continuing necessity for multidisciplinary 

team efforts in plant 

breeding, and the rapidly changing 

development of technologies, three 

overlapping avenues can be 

considered for raising the yield 

frontier in wheat: continued 

investments in “conventional 

breeding” methods; use of current 

and expanded genetic diversity; 

and investigation and 

implementation of biotechnology 

assisted plant breeding. 

Conventional Wheat 

Breeding 

It is likely that gains to be 

achieved from conventional 

breeding will continue to be 

significant for the next two decades 

or more (Duvick, 1996), but these

2 Opening Remarks — S. Rajaram 

are likely to come at a higher 

research cost than in the past. In 

recent surveys of wheat breeders 

(Braun et al., 1998; Rejesus et al., 

1996), more than 80% of 

respondents expressed concern that 

plant variety protection (PVP) and 

plant or gene patents will restrict 

access to germplasm. This may 

have deleterious consequences for 

future breeding success. 

Rasmusson (1996) has stated that 

nearly half of the progress made by 

breeders in the past can be 

attributed to germplasm exchange. 

Regional and international 

nurseries have been an efficient 

means of gathering data from 

varied environments and exposing 

germplasm to diverse pathogen 

selection pressures, while 

providing access and exchange of 

germplasm. Breeders utilize these 

cooperative nurseries extensively 

in their crossing programs (Braun 

et al., 1998). However, the number 

of cooperatively distributed wheat 

yield and screening nurseries has 

been greatly reduced during the 

past decade. 

Investments needed for 

breeding efforts will increase with 

increasing yield levels. Further, 

progress to develop higher yielding 

cultivars is reduced with every 

objective added to a breeding 

program. Though the list of 

important traits may get longer and 

longer, little if any assistance has 

been provided by economists to 

prioritize breeding objectives. 

Considering that a wheat breeding 

program like CIMMYT allocates 

around 60% of its resources to 

durable resistance breeding, the 

need for research in this field is 

obvious. Due to high costs, we see 

durable resistance breeding as one 

of the first fields where 

transformation should be applied 

by breeders through introgression 

of one or more genes controlling 

disease resistance. 

Adoption of CIMMYT- 

Based Germplasm 

CIMMYT’s breeding 

methodology is tailored to develop 

widely adapted, disease resistant 

germplasm with high and stable 

yield across a wide range of 

environments. The impact of this 

approach has been significant. 

The total spring bread wheat 

(Triticum aestivum L.) area in 

developing countries, excluding 

China, is around 63 million ha, of 

which 36 million ha or 58% are 

planted to varieties derived from 

CIMMYT germplasm (Table 1) 

(Byerlee and Moya, 1993; 

Rajaram, 1995). During the 1966-90 

period, 1317 bread wheat cultivars 

were released by developing 

countries, of which 70% were either 

direct releases from CIMMYT 

advanced lines or had at least one 

CIMMYT parent (Byerlee and 

Moya, 1993). For the 1986-90 

period, 84% of all bread wheat 

cultivars released in developing 

countries had CIMMYT germplasm 

in their pedigrees. Simultaneously 

the use of dwarfing genes has 

continued to increase over time. 

Today, regardless of the type of 

wheat, more than 90% of all wheat 

varieties released in developing 

countries are semidwarfs, which 

covered 70% of the total wheat area 

in developing countries by the end 

of 1990 (Byerlee and Moya, 1993). 

The continuous adoption of 

semidwarf spring wheat cultivars 

in the post-Green Revolution 

period (1977-90) resulted in about 

15.5 million tons of additional 

wheat production in 1990, valued 

at about US$ 3 billion, of which 

50%, or US$ 1.5 billion, is attributed 

to the adoption of new Mexican 

semidwarf wheat cultivars (Byerlee 

and Moya, 1993). In 1990, an 

estimated 93% of the total spring 

bread wheat production in 

developing countries, excluding 

China, came from semidwarf 

spring wheats, which covered 

about 83% of the total spring bread 

wheat area in developing countries 

(Byerlee and Moya, 1993). 

Table 1. Origin of spring bread wheat varieties in 

developing countries. 

CIMMYT CIMMYT 

NARS cross 

CIMMYT No 

cross parents ancestor CIMMYT 

1966-90 45% 28% 3% 24% * 

1991-97 58% 30% 3% 9% 

* Estimated. 

Note: Excluding China. NARS=national agricultural 

research system. 

The cornerstone of CIMMYT’s 

breeding methodology is targeted 

breeding for the megaenvironments, 

the use of a diverse 

gene pool for crossing, shuttle 

breeding, selection for yield under 

optimum conditions, and multilocational 

testing to identify 

superior germplasm with good 

disease resistance. In this paper we 

would like to present some recent 

developments in CIMMYT’s Wheat 

Program. 

Targeted breeding: The 

mega-environment concept 

To address the needs of diverse 

wheat growing areas, CIMMYT 

introduced in 1988 the concept of 

mega-environments (ME) (Rajaram 

et al., 1994). Mega-environments 

are defined as a broad, not 

necessarily contiguous areas, 

occurring in more than one country 

and frequently transcontinental, 

defined by similar biotic and 

abiotic stresses, cropping system 

requirements, consumer 

preferences, and, for convenience,

y volume of production. 

Germplasm generated for a given 

ME is useful throughout that 

environment, accommodating 

major stresses but perhaps not all 

the significant secondary stresses. 

Within an ME, millions of hectares 

are addressed with a certain degree 

of homogeneity as relates to wheat. 

By 1993, 12 ME had been defined, 6 

for spring wheats (ME1-ME6), 3 for 

facultative wheats (ME7-ME9), and 

3 for winter wheats (ME9-ME12). 

Details of each ME are given in 

Table 2. 

Table 2. Classification of megaenvironments (MEs) used by the CIMMYT Wheat Program. 

Historical Aspects and Future Challenges of an International Wheat Program 3 

Use of diverse genepools to 

maintain genetic diversity 

Recent surveys conducted by 

the CIMMYT Economics Program 

have found that 58% of all wheat 

varieties in developing countries 

derive from CIMMYT germplasm; 

this percentage rises to more than 

80%, if varieties with parents of 

CIMMYT origin are also included 

(Table 1). This spectacular success 

puts an enormous burden on 

CIMMYT to continually diversify 

its germplasm base for resistance 

and stability parameters. 

Broad-based plant germplasm 

resources are imperative for a 

sound and successful breeding 

program. Utmost attention is given 

to the genetic diversity within 

CIMMYT germplasm to minimize 

the risk of genetic vulnerability, 

since it is grown on large areas and 

is widely used by national 

programs. I believe that the use of 

genetically diverse material is 

mandatory to increase yield 

potential and yield stability in the 

future. In any year 500-800 parental 

lines are considered for crossing. 

Major Representative 

Year 

breeding 

Area Moisture Temperature Growth breeding locations/ began at 

ME Latitudea (m ha) b regimec regimed habit Sowne objectivesf, g regions CIMMYT 

SPRING WHEAT 

1 Low 32.0 Low rainfall, Temperate Spring A Resistance to Yaqui Valley, 1945 

irrigated lodging, SR, LR, YR Mexico; Indus 

Valley, Pakistan; 

Gangetic Valley, 

India; Nile Valley, 

Egypt 

2 Low 10.0 High rainfall Temperate Spring A As for ME1 + North African 1972 

resistance to Coast, Highlands of 

YR, Septoria East Africa, Andes, 

spp., sprouting and Mexico 

3 Low 1.7 High rainfall Temperate Spring A As for ME2 + Passo Fundo, 1974 

acid soil 

tolerance 

Brazil 

4A Low 10.0 Low rainfall, Temperate Spring A Resistance to Aleppo, Syria; 1974 

winter drought, Settat, Morocco 

dominant Septoria spp., YR 

4B Low 5.8 Low rainfall, Temperate Spring A Resistance to Marcos Juárez, 1974 

summer drought, Argentina 

dominant Septoria spp., 

Fusarium spp., 

LR, SR 

4C Low 5.8 Mostly Hot Spring A Resistance to Indore, India 1974 

residual drought, and 

moisture heat in seedling 

stage 

5A Low 3.9 High rainfall Hot Spring A Resistance to Joydepur, 1981 

/ irrigated, heat, Helmin- Bangladesh; 

humid thosporium 

spp., Fusarium 

spp., sprouting 

Londrina, Brazil 

5B Low 3.2 Irrigated , Hot Spring A Resistance to Gezira, Sudan; 1975 

low humidity heat and SR Kano, Nigeria 

6 High 5.4 Moderate Temperate Spring S Resistance to Harbin, China 1989 

rainfall/ SR, LR, Helminsummer 

thosporium spp., 

dominant Fusarium spp., 

sprouting, 

photoperiod 

sensitivity 

(cont’d.)


Table 2. Continued. 

Major Representative 

Year 

breeding 

Area Moisture Temperature Growth breeding locations/ began at 

ME Latitudea (m ha) b regimec regimed habit Sowne objectivesf, g regions CIMMYT 

WINTER/FACULTATIVE WHEAT 

7 High – Irrigated Moderate Facultative A Rapid grain Zhenzhou, China 1986 

cold fill, resistance 

to cold, YR, PM, 

BYD 

8A High – High rainfall Moderate Facultative A Resistance to Chillan, Chile 1986 

/ irrigated, cold cold, YR, Septoria 

long season spp. 

8B High – High rainfall Moderate Facultative A Resistance to Edirne, Turkey 1986 

/ irrigated, cold Septoria spp., 

short season YR, PM, Fusarium 

spp., sprouting 

9 High – Low rainfall Moderate Facultative A Resistance to Diyarbakir, Turkey 1986 

cold cold, drought 

10 High – Irrigated Severe cold Winter A Resistance to 

winterkill, YR, 

LR, PM, BYD 

Beijing, China 1986 

11A High – High rainfall Moderate Winter A Resistance to Temuco, Chile 1986 

/irrigated, cold Septoria spp., 

long season Fusarium spp., 

YR, LR, PM 

11B High – High rainfall Severe cold Winter A Resistance to Lovrin, Romania 1986 

/ irrigated, LR, SR, PM, 

short season winterkill, 

sprouting 

12 High – Low rainfall Severe cold Winter A Resistance to 

winterkill, 

drought, YR, 

bunts 

Ankara, Turkey 1986 

Source: Adapted from Rajaram et. al. (1995). 

a Low = less than about 35-40 degrees. 

b Exact area distribution for winter/facultative wheat is not available. 

c Refers to rainfall just before and during the crop cycle. High = >500mm; low = 17.5°C; cold =

wheat to increase grain size. The 

six highest yielding lines derived 

from this program outyielded their 

breadwheat parent by 5-20% in 

yield trials in Cd. Obregon, Mexico. 

Shuttle breeding within 

Mexico 

Young and Frey (1994) provide 

two factors that influence the 

success of a shuttle program: a) the 

use of a germplasm pool 

encompassing genotypes with 

broad adaptation, and b) the use of 

selection environments eliciting 

different responses from plant 

types. They also state that the 

wheat breeding program of N.E. 

Borlaug met these conditions. 

When Borlaug started the shuttle 

breeding approach in 1945, his only 

objective was to speed up breeding 

for stem rust resistance. Since then, 

segregating populations have been 

shuttled 100 times between the two 

environmentally contrasting sites 

in Mexico, Cd. Obregon and Toluca 

(Braun et al., 1992). 

Some of the salient points of 

this shuttle breeding program are: 

• Cd. Obregon is situated at 28 o N 

at 40 masl, in the sunny, fertile, 

and irrigated Yaqui Valley of 

Sonora. Wheats are planted in 

November when temperatures 

are low and harvested in April/ 

May when temperatures are 

high. The yield potential of 

location is high (±10 t/ha); 

wheat diseases are limited to 

only leaf rust, Karnal bunt, and 

black point. 

• The Toluca location is 

characterized by high humidity 

(precipitation: ±1000 mm). The 

nursery is planted in May/June 

when temperatures are high and 

harvested in October when they 

are low. High humidity causes 


incidence of many diseases 

including rust, septorias, BYD, 

and fusarium. 

An important result of shuttle 

breeding was the selection of 

photo-insensitive wheat genotypes. 

Initially, selection for photoperiod 

insensitivity was unconscious, but 

only this trait permitted the wide 

spread of the Mexican semidwarfs 

(Borlaug, 1995). Today, this trait has 

been incorporated into basically all 

spring wheat cultivars grown 

below 48 o latitude and is now also 

spreading to wheat areas above 48 o 

N (Worland et al., 1994). 

Multi-locational testing 

and wide adaptation 

About 1500 sets of yield trials 

and screening nurseries consisting 

of around 4000 advanced bread 

wheat lines are annually sent to 

more than 200 locations. Multilocational 

testing plays a key role in 

identifying the best performing 

entries for crossing. Since the 

shuttle program permits two full 

breeding cycles a year, it takes 

around five to six years from 

crossing to international 

distribution of advanced lines to 

cooperators. This “recurrent 

selection program” ensures 

continuous and rapid pyramiding 

of desirable genes. 

Ceccarelli (1989) pointed out 

that the widespread cultivation of 

some wheat cultivars should not be 

taken as a demonstration of wide 

adaptation, since a large fraction of 

these areas are similar or made 

similar by use of irrigation and/or 

fertilizer. Therefore, the term wide 

adaptation has been used mainly to 

describe geographical rather than 

environmental differences. If this is 

true, the genotypic variation 

should be considerably higher than 

GxE interaction in ANOVAs of 

CIMMYT trials. Braun et al. (1992) 

showed that this is not the case. 

When subsets of locations were 

grouped by geographical and/or 

environmental similarities, GxE 

interaction was mostly greater than 

the genotypic variance. The 

environmental diversity of sites 

where CIMMYT’s 21st 

International Bread Wheat 

Screening Nursery was grown and 

the diversity among genotypes in 

this nursery were demonstrated by 

Bull et al. (1994). They classified 

similarities among environments 

by forming subsets of genotypes 

from the total dataset and 

comparing them with the 

classification based on the 

remaining genotypes. Using this 

procedure they concluded that it 

was not possible to form a stable 

grouping of environments, because 

little or no relationship existed 

among them. 

Conclusions drawn from trials 

carried out on research stations are 

always open to critics who argue 

that these results do not necessarily 

reflect conditions in farmers’ fields. 

However, the wide acceptance of 

CIMMYT germplasm by farmers in 

MEs 1-5 does not support the view 

that the wide adaptation of 

CIMMYT germplasm is based on 

geographical rather than 

environmental differences. 

Breeding for High Yield 

Potential and Enhanced 

Stability 

Selection of segregating 

populations and consequent yield 

testing of advanced lines are 

paramount for identifying high 

yielding and input responsive 

wheat genotypes. The increase in 

yield potential of CIMMYT


cultivars developed since the 1960s 

is shown in Figure 1 (Rees et al., 

1993). The average increase per 

year was 0.9%, and there is no 

evidence that a yield plateau has 

been reached. This progress in 

increasing genetic yield potential is 

closely associated with an increase 

in photosynthetic activity (Rees et 

al., 1993.). Both photosynthetic 

activity and yield potential 

increased over the 30-year period 

by some 25%. These findings may 

have major implications for 

CIMMYT’s future selection strategy 

since there is evidence that wheat 

genotypes with a higher 

photosynthetic rate have lower 

canopy temperature, which can be 

easily, quickly, and cheaply 

measured using a hand-held 

thermometer. If this is verified in 

future trials, this trait may be used 

by breeders to increase selection 

efficiency for yield potential. This 

technique may be particularly 

useful in selecting wheat genotypes 

adapted to environments where 

heat is a production constraint. 

Yield per se is closely associated 

with input responsiveness. 

Increasing the input efficiency at 

low production levels can shift 

crossover points, provided they 

exist, and enhance residual effects 

of high genetic yield potential. 

Furthermore, combining input 

efficiency with high yield potential 

will allow farmers to benefit from 

such cultivars over a wide range of 

input levels. The increase in 

nitrogen use efficiency is shown in 

Figure 2 (Ortiz-Monasterio et al., 

1995). 

CIMMYT’s breeding strategy 

has resulted in the development of 

widely grown varieties, such as 

Siete Cerros, Anza, Sonalika, and 

Seri 82, which at their peak were 

grown on several million 

hectares. Seri 82 was released for 

irrigated as well as rainfed 

environments. Reynolds et al. 

(1994) reported that Seri 82 was 

the highest yielding entry in the 

1st and 2nd International Heat 

Stress Genotype Experiment. 

Seri 82 can be considered as the 

first wheat genotype truly 

adapted to several MEs, 

particularly to ME1, ME2, ME4, 

and ME5. A comparison between 

Seri 82 and Pastor, a recently 

developed CIMMYT cultivar, 

demonstrates the progress made 

in widening adaptation during 

the last ten years. Figure 3 shows 

the performance of Pastor 

(Pfau/Seri//Bow) in CIMMYT’s 

13th Elite Spring Wheat Yield 

Nursery. In 50 trials grown in all 

6 MEs, Pastor yielded 

significantly (P=0.01) lower than 

the highest yielding entry only 

in eight trials. This figure also 

demonstrates that Pastor has no 

tendency to crossover at any 

yield level. While we do not 

reject that crossover may exist 

for some cultivars, Pastor and 

Seri 82 are clear examples that it 

is possible to combine abiotic 

stress tolerance with high yield 

potential. Figure 4 shows the 

yield difference between Seri 82 

and Pastor. Only in 16 out of 50 

trials did Seri outyield Pastor. 

The latter cultivar proves that 

breeding for wide adaptation 

has not yet reached its limit. 

Apart from the physiological 

basis of yield potential, the yield 

gains in CIMMYT wheats are 

due to the utilization of certain 

genetic resources. The 

germplasm has been paramount 

to increase yield in CIMMYT’s 

Wheat Program and in 

Yield in kg/ha 

8000 

Y=-104607+56.56x 

7500 

7000 

R=0.96*** 

Gain/year 0.9% 

6500 

6000 

1960 

1965 1970 1975 1980 1985 1990 

Variety year of release 

Figure 1. Mean grain yields for the historical series 

of bread wheat varieties for the year 1990-93 at Cd. 

Obregon, Mexico (data from Rees et al., 1993). 

Grain yield in kg/ha 

8000 

7000 

6000 

5000 

4000 

3000 

2000 

50 

300 kg N 

ON 

55 60 65 70 75 80 85 

Genotype year of release 

Figure 2. Grain yield of the historical series of bread 

wheats at Cd. Obregon, Mexico, at 0 and 300 kg/ha N 

application (data from J.I. Ortiz-Monasterio et al., 

1995). 

Yield (kg/ha) 

12000 

10000 

8000 

6000 

4000 

2000 

0 

0 

2000 4000 6000 8000 10000 

Location mean yield (kg/ha) 

Maximum yield 

Pastor significantly different 

from highest yield in entry 

Mean 

Figure 3. Yield of Pastor at 50 locations of the 13th 

ESWYT. 

Yield (kg/ha) 

4000 

3000 Pastor 

2000 

1000 

0 

-1000 

Seri 82 

-2000 

-3000 

600 

1000 

2000 

3000 

4000 

5000 

6000 

7000 

8000 

Location mean yield (kg/ha) 

9000 

10000 

Figure 4. Yield difference between Pastor and Seri 82 

at 50 locations of the 13th ESWYT.

Minnesota’s barley program 

(Rasmusson, 1996). Some examples 

are listed next. 

• The incorporation of Norin 10 x 

Brevor germplasm not only 

produced dwarf wheats, but also 

simultaneously gave high yield. 

• Spring and winter crosses 

involving the variety Kavkaz 

resulted in Veerys, representing 

high yield potential and 

enhanced yield stability 

(Figure 5). 

• The incorporation of the Lr19 

gene and Aegilops squarrosaderived 

synthetic wheats has 

further increased yield potential. 

The variety Super Seri has the 

Lr19 gene (Figure 6) and a 

derivative of Ae. squarrosa is 

given in Table 3. 

Breeding for durable disease 

resistance 

From the beginning, 

incorporating durable, non-specific 

disease resistance into CIMMYT 

germplasm was a high priority, 

since breeding widely adapted 

germplasm with stable yields 

without adequate resistance against 

the major diseases would be 

impossible. The concept goes back 

to Niederhauser et al. (1954), 

Borlaug (1966), and Caldwell 

(1968), who advocated developing 

general resistance in the CIMMYT 

Yield (t/ha) 

10 

8 

6 

4 

2 

ISWYN 15 

2 3 5 

Environments (t/ha) 

7 9 

Figure 5. Performance of Veery in 73 global 

environments (ISWYN 15). 


program versus the specific or 

hypersensitive type. Very diverse 

sources of resistance for rusts and 

other diseases are intentionally 

used in the crossing program. The 

major sources are germplasm from 

national programs, advanced 

CIMMYT lines, germplasm 

received from the CIMMYT or 

other genebanks, and CIMMYT’s 

wide crossing program. 

CIMMYT’s strategy in the case 

of cereal rusts is to breed for 

general resistance (slow rusting) 

based on historically proven stable 

genes. This non-specific resistance 

can be further diversified by 

accumulating several minor genes 

and combining them with different 

specific genes to provide a certain 

degree of additional genetic 

diversity. This concept is also 

applied to other diseases like 

septoria leaf blotch, 

helminthosporium spot blotch, and 

fusarium head scab. The present 

situation of CIMMYT germplasm 

regarding resistance to major 

diseases may be summarized as 

follows: 

• Stem rust (Puccinia graminis f.sp. 

tritici) resistance has been stable 

after 40 years of utilization of the 

genes derived from the variety 

Hope. Losses due to stem rust 

Veery 

Average 

yield 

have been negligible since the 

late 1960s. The resistance is 

based on the gene complex Sr2, 

which actually consists of Sr2 

plus 4-5 minor genes pyramided 

into three to four gene 

combinations (Rajaram et al., 

1988). Sr 2 alone behaves as a 

slow rusting gene. Since there 

has been no major stem rust 

epidemic in areas where 

CIMMYT germplasm is grown, 

the resistance seems to be 

durable. 

• Leaf rust (Puccinia recondita f.sp. 

tritici) resistance has been 

stabilized by using genes 

derived from many sources, in 

particular the Brazilian cultivar 

Frontana (Singh and Rajaram, 

1992). No major epidemic has 

been observed in almost 20 

years. Four partial resistance 

genes, including Lr 34, give a 

slow rusting response and have 

been the reason for the 

containment of leaf rust 

epidemics in the developing 

world during the last 15 years. 

About 60% of CIMMYT 

germplasm carries one to four of 

these partial resistance genes. 

Lr34 is linked to Yr18 as well as 

to a morphological marker (leaf 

tip necrosis) that makes the gene 

particularly attractive for 

8500 

Super Seri 

8000 

Bacanora 88 

7500 

Seri 82 Oasis 86 

7000 Yecora 70 

Ciano 79 

Nacozari 76 

6500 

6000 

1960 

Siete Cerros 66 

Pitic 62 

1970 1980 

Year of release 

1990 2000 

Figure 6. Increase in grain yield potential of 

CIMMYT-derived wheats as a function of year of 

release. 

Grain yield in kg/ha


breeders (Singh, 1992a, b). 

CIMMYT continues to look for 

new sources of partial resistance. 

• Stripe rust (Puccinia striiformis): 

Slow rusting genes like Yr18 

have been identified (Singh, 

1992b); however, their 

interaction is less additive than 

for leaf and stem rust. More 

basic research is needed to 

understand the status of durable 

resistance in high yielding 

germplasm. The breakdown of 

Yr9 in West Asia and North 

Africa and the present yellow 

rust epidemics underline the 

need for the release of cultivars 

with accumulated durable 

resistance. 

• Septoria tritici: Initially all 

semidwarf cultivars developed 

for irrigated conditions were 

susceptible. Today more than 

eight genes have been identified 

in CIMMYT germplasm and two 

to three genes in combination 

provide acceptable resistance. 

Future activities will concentrate 

on pyramiding these genes and 

spreading them more widely 

within CIMMYT germplasm 

(Jlibene, 1992; Matus-Tejos, 

1993). 

• Karnal bunt (Tilletia indica): 

More than five genes have been 

identified and most of them are 

partially dominant. Genes 

providing resistance to Karnal 

bunt have been incorporated 

into high yielding lines (Singh et 

al., 1995). 

• Powdery mildew (Erysiphe 

graminis f.sp. tritici): CIMMYT 

germplasm is considered 

vulnerable to this disease. The 

disease is absent in Mexico and 

the responsibility to transfer 

resistance genes has been 

delegated to CIMMYT’s regional 

breeder in South America. 

Breeding for 

Drought Tolerance 

There has been a large 

transformation in the productivity 

of wheat due to the application of 

Green Revolution technology. This 

has resulted in a doubling and 

tripling of wheat production in 

many environments, but especially 

in irrigated areas. High yielding 

semidwarf wheats have 

continuously replaced the older tall 

types at a rate of 2 million ha per 

year since 1977 (Byerlee and Moya, 

1993). 

There is a growing recognition 

that the dissemination, application, 

and adoption of this technology 

has, however, been slower in 

marginal environments, especially 

in the semiarid environments 

affected by poor distribution of 

water and drought. The annual 

gain in genetic yield potential in 

drought environments is only 

about half that obtained in 

irrigated, optimum conditions. 

Many investigators have attempted 

to produce wheat varieties adapted 

to these semiarid environments 

with limited success. Others have 

criticized the Green Revolution 

technology (Ceccarelli et al., 1987) 

for failing to adequately address 

productivity constraints in 

semiarid environments, although 

their own recommended 

technology has had limited impact, 

in particular in farmers’ fields. This 

criticism is in clear contrast to the 

actual acceptance of semidwarf 

wheat cultivars in rainfed areas, 

since most of the 16 million ha 

increase in the area sown to 

Mexican semidwarf wheats in the 

mid-1980s occurred in rainfed 

areas; in 1990, more than 60% of the 

dryland area in developing 

countries were planted with 

semidwarfs (Byerlee and Moya, 

1993). 

Definition of semiarid 

environments and 

description 

of drought patterns 

In Table 2, the major global 

drought patterns observed in 

wheat production are presented 

(Rajaram et al., 1994, Edmeades et 

al., 1989). Through respectively 

dealing with spring (ME4A), 

facultative (ME9), and winter 

wheat (ME12), these three MEs are 

characterized by sufficient rainfall 

prior to anthesis, followed by 

drought during the grain-filling 

period. In South America, the 

Southern Cone type of drought 

(ME4B) is characterized by 

moisture stress early in the crop 

season, with rainfall occurring 

during the post-anthesis phase. In 

the Indian Subcontinent type of 

drought stress (ME4C), the wheat 

crop utilizes water reserves left 

from the monsoon rains during the 

previous summer season. In the 

Subcontinent the irrigated wheat 

crop (ME1) may also suffer drought 

due to a reduced or less than 

optimum number of irrigations. 

The traditional methodology 

for breeding for drought stress is 

typified by handling all segregating 

populations under target 

conditions of drought, and the use 

of local landraces is recommended 

in the breeding process (Ceccarelli 

et al., 1987). The methodology rests

on the assumption that the agroecological 

situation facing the 

farmer does not vary in its 

expression over time and that 

responsiveness of varieties to 

improved growing conditions will 

not be needed. It also assumes that 

crossover will always occur below 

a certain yield level under dry 

conditions, where modern high 

yielding varieties of a responsive 

nature would always yield less 

than traditional landrace-based 

genotypes. Such crossovers may 

occur for selected genotypes, and 

one should always be open to the 

possibility that there are real 

“drought tolerance” traits 

operating at the 1 t/ha and below 

yield level that adversely affect 

high yield potential at the 4 t/ha 

and higher yield levels. So far such 

traits have not been identified at 

CIMMYT. In any case, crossover 

would be restricted to such harsh 

conditions, where in fact farmers 

choose—rightfully so—not to grow 

wheat at all, but to produce other, 

more drought tolerant crops such 

as barley or sorghum, or resort to 

grazing (van Ginkel et al., 1998). 

At CIMMYT we advocate an 

“open-ended system” of breeding 

in which yield responsiveness is 

combined with adaptation to 

drought conditions. Most semiarid 

environments differ significantly 

across years in their water 

availability and distribution 

pattern. Hence it is prudent to 

construct a genetic system in which 

plant responsiveness provides a 

bonus whenever conditions 

improve due to higher rainfall. 

With such a system, improved 

moisture conditions immediately 

translate into greater gains for the 

farmer. 


The Veerys 

In the early 1980s, when 

advanced lines derived from the 

spring x winter cross Kavkaz/ 

Buho//KAL/BB (CM33027) were 

tested in 73 global environments of 

the 15th International Wheat Yield 

Nursery (15th ISWYN) (Figure 5), 

their performance was quite 

untypical compared to any 

previously known high yielding 

varieties. In later tests, we found 

that these lines, called Veerys, carry 

the 1B.1R translocation from rye 

and that the general performance 

of such germplasm was superior 

not only in high yielding 

environments but particularly 

under drought conditions (Villareal 

et al., 1995; Table 4). From the Veery 

cross 43 varieties were released, 

excluding those released in Europe. 

The Veerys represent a genetic 

system in which high yield 

performance in favorable 

environments and adaptation to 

drought could be combined in one 

genotype. The two genetic systems 

are apparently not always 

incompatible, although others have 

claimed that their combination 

would not be possible. However, it 

is possible to hypothesize a plant 

system in which efficient input use 

and responsiveness to improved 

levels of external inputs (in this 

case, available water) can be 

combined to produce germplasm 

for marginal (in this case, semiarid) 

environments that at least 

maintains minimum traditional 

yields and expresses dramatic 

increases whenever conditions 

improve. The impacts described 

below support the utilization of 

this methodology. 

• By the mid-1980s CIMMYT 

germplasm occupied 45% of the 

semiarid wheat areas with 300- 

500 mm of rainfall, and 21% of 

the area less than 300 mm 

(Morris et al., 1991), including 

large tracts in West Asia/North 

Africa (WANA). By 1990 63% of 

the dryland areas, especially in 

ME4A and ME4B, was planted 

with semidwarf wheats (Byerlee 

and Moya, 1993), many carrying 

the 1B/1R translocation. 

• To support the above 

assumptions, an experiment was 

conducted (Calhoun et al., 1994; 

Tables 5 and 6) to determine 

how the most modern and 

widely (spatially) adapted 

germplasm compared to 

commercial germplasm from 

countries representing the 

Mediterranean region (ME4A), 

the Southern Cone of South 

America (ME4B), and the Indian 

Table 4. Effect of the 1BL.1RS translocation on yield characteristics of 28 random F2-derived F6 

lines from the cross Nacozari 76/Seri 82 under reduced irrigated conditions. 

Plant characteristics 1BL.1RS 1B Mean diff. 

Grain yield 4945 4743 202 * 

Above-ground biomass at maturity (t/ha) 12600 12100 500 * 

Grains/m2 14074 13922 152NS 

Grains/spike 43.5 40.6 2.9 * 

1000-grain weight (g) 37.1 36.5 0.5 * 

Source: Villareal et al. (1995). 

Note: NS: not significatnt, * : significant at the 0.05 level.


Table 5. Wheat genotypes representing adaptation to different moisture environments. 

ME1 ME4A ME4B ME4 Irrigation 

(Mediterranean) 

(Southern Cone) 

(Subcontinent) 

Super Kauz, Pavon 76, Genaro 81, Opata 85 

Almansor, Nesser, Sitta, Siete Cerros 

Cruz Alta, Prointa Don Alberto, LAP1376, PSN/BOW CM69560 

C306, Sonalika, Punjab 81, Barani 

Source: Calhoun et al. (1994). 

Table 6. Grain yields of selected wheat genotypes grouped by adaptation and tested under 

moisture regimes in the Yaqui Valley, Mexico, 1989-90 and 1990-91 

Full Late 

Adaptation group 

Early Residual 

irrigation1 drought2 drought3 moisture4 ME1 Irrigation 6636 a * ME4C ME4B ME4C Mediterranean 

Southern Cone 

Subcontinent 

6342 b 

5028 c 

4778 c 

4198 a 

3990 ab 

3148 bc 

3245 bc 

4576 a 

4390 b 

4224 b 

3657 c 

3032 a 

2883 b 

2359 c 

2704 b 

Source: Calhoun, et al. 1994 

1 Received 5 irrigations; 2 received 2 irrigations early before heading; 3 received one irrigation for 

germination and two post heading; 4 received one irrigation for germination only. 

* Means in the same column followed by the same letter are not significantly different at P=0.05. 

Subcontinent (ME4C), under 

conditions artificially simulating 

those three MEs. The most 

widely adapted CIMMYT lines 

outyielded the commercial 

varieties in all artificially 

simulated environments. 

• Nesser is an advanced line with 

superior performance in 

drought conditions bred at 

CIMMYT/Mexico and identified 

at ICARDA/Syria. The cross 

combines a high yielding 

CIMMYT variety Jupateco and a 

drought tolerant Australian 

variety W3918A. The 

performance of Nesser in 

WANA’s ME4A environments 

has been widely publicized 

(ICARDA, 1993), and the line is 

considered by ICARDA to 

represent a uniquely drought 

tolerant genotype. However, it 

was selected at CIMMYT/ 

Mexico under favorable 

environments, and carries a 

combination of input efficiency 

and high yield responsiveness. It 

performs similarly to the Veery 

lines in the absence of rust. 

The breeding scheme 

The breeding scheme 

described below is used to 

combine the two genetic systems. 

Two contrasting selection 

environments are alternated, 

allowing alternate selection for 

input efficiency and input 

responsiveness. 

F1 Crosses involving spatially 

widely adapted germplasm 

representing yield stability and 

yield potential, with lines with 

proven drought tolerance in 

the specific setting of either 

ME4A, ME4B or ME4C. Winter 

wheats and synthetic 

germplasm are emphasized. 

F2 Individual plants are raised 

under irrigated and optimally 

fertilized conditions and 

inoculated with a wide 

spectrum of rust virulence. 

Only robust and (horizontally) 

resistant plants are selected. 

These may represent 

adaptation to favorable 

environments. 

F3, F4 The selected F2 plants are 

evaluated using a modified 

pedigree/bulk breeding system 

(Rajaram and van Ginkel, 1995) 

under rainfed conditions or very 

low water availability. The 

selection is based on individual 

lines rather than individual 

plants. The progenies are 

selected based on such criteria as 

spike density, biomass/vigor, 

grains/m 2 , and others (van 

Ginkel et al., 1998) (Table 7). This 

index helps identify lines which 

may adapt to low water 

situations. 

F5, F6 The selected lines from F4 

are further evaluated under 

optimum conditions. 

Table 7. Genotypic correlation (rg) between 

agronomic traits and final grain yield, for 

optimum environment (full irrigations) and 

reduced water regime (late drought, 

Mediterranean type) in wheat. 

Moisture regime 

Full Late 

Trait irrigation drought 

Days to heading 0.40 0.19 

Days to maturity 0.29 0.27 

Grain fill period -0.32 0.36 

Height -0.39 0.05 

Peduncle length 

Relative peduncle 

-0.46 0.22 

extrusion -0.51* 0.25 

Spike length -0.28 -0.50* 

Spike/m2 -0.12 0.64** 

Grains/spike 0.62* -0.42 

Grains/m2 0.74** 0.68** 

Yield/spike 0.55* -0.64** 

1000 grain weight 0.08 -0.45 

Test weight 0.13 0.05 

Harvest index 0.83** -0.39 

Biomass 0.90** 0.94** 

Straw yield 0.52* 0.86** 

Yield / day (planting) 0.99** 0.57* 

Yield / day (heading) 0.94** 0.44 

Biomass / day (planting) 0.86** 0.69** 

Biomass / day (heading) 0.74** 0.63** 

Vegetative growth rate 0.32 0.63** 

Spike growth rate 0.62** -0.58* 

Grain growth rate 0.17 -0.44 

*, ** indicate significance at the 0.05 and 

0.01probability level, respectively. 

Source: van Ginkel et al. (1998).

F7, F8 Simultaneous evaluations 

under optimum and low water 

environments. Selection of lines 

showing outstanding 

performance under both 

conditions. Further evaluation in 

international environments is 

carried out for purposes of 

verification. 

The proposed breeding 

methodology is supported by 

research published in recent years 

by others, not only on wheat 

(Bramel-Cox et al., 1991; Cooper et 

al., 1994; Duvick, 1990, 1992; 

Ehdaie et al., 1988; Uddin et al., 

1992; Zavala-Garcia et al., 1992), 

where the importance of testing 

and selecting in a range of 

environments, including wellirrigated 

ones, has shown to 

identify superior genotypes for 

stressed conditions. The 

methodology aims at combining 

input efficiency with input 

responsiveness by alternating 

selection environments during the 

breeding process. 

Future Research 

Directions 

Yield stability and yield 

potential 

Traxler et al. (1995) analyzed 

grain yield increases and yield 

stability of bread wheat cultivars 

released during the last 45 years. In 

the early period of the Green 

Revolution, when rapid yield 

increases occurred, variance for 

yield concomitantly increased. 

Since the early 1970s, yield stability 

has increased at the cost of 

increases in yield. However, steady 

progress was made in developing 

varieties with improved stability, 

grain yield or both. For the 

developing world, yield stability 


increased since the beginning of the 

Green Revolution (Smale and 

McBride, 1996). While price policy, 

input supplies, and environmental 

variation contribute more to yield 

stability than the genotype, the 

increasing yield stability reflects 

the emphasis given by breeders to 

develop germplasm with tolerance 

to a wider range of diseases and 

abiotic stresses. Sayre et al. (1997) 

concluded that from 1964 to 1990, 

yield potential in CIMMYT-derived 

cultivars increased at a rate of 67 

kg/ha/yr or 0.88% per year. The 

data did not suggest that a yield 

plateau had been reached and the 

performance of recently released 

lines, such as Attilla (pb343) and 

Babax (Baviacora M92) indicates 

that yield potential has been 

further enhanced. Improvements 

made by breeding for yield stability 

and adaptation may be illustrated 

by data for the advanced line 

Pastor, which outyielded the 

hallmark check cultivar Seri 82 in 

34 out of 50 locations where the 13 th 

Elite Spring Wheat Yield Nursery 

was grown (Figure 4). Discussion 

on how to increase the yield 

potential of wheat often still centers 

around traits that contributed to 

the success of the Green Revolution 

varieties more than 30 years ago, 

e.g., photoperiod and dwarfing 

genes (Worland et al., 1998; Sears, 

1998). 

CIMMYT has made a modest 

investment in restructuring and 

creation of a new plant type 

characterized by robust stem, broad 

leaf, long spike (30 cm), and large 

numbers of grain per spike. The 

new plant type still suffers due to 

diseases and is deficient in quality 

and certain agronomic 

characteristics. In 1994, we 

launched a dynamic breeding 

program to correct these 

deficiencies. 

Plant nutrition 

Selecting for yield potential and 

yield stability under medium to 

high levels of nitrogen has 

indirectly increased efficiency for 

nutrient uptake. Recently released 

CIMMYT bread wheat cultivars 

require less nitrogen to produce a 

unit amount of grain than cultivars 

released in the previous decades 

(Ortiz Monasterio et al., 1997). 

Under low N levels in the soil, N 

use efficiency increased mainly due 

to a higher N uptake efficiency— 

the ability of plants to absorb N 

from the soil—whereas under high 

N levels, the N utilization 

efficiency—the capacity of plants to 

convert the absorbed N into grain 

yield—increased. In spite of the 

increased N use efficiency of 

recently released wheat cultivars, 

the response to nitrogen of wheat 

production systems has been 

observed to be declining in many 

areas of Southeast Asia. In Turkey, 

where zinc deficient soils are 

common, recently released winter 

bread wheat cultivars have 

improved Zn uptake and 

consequently higher grain yield 

than local landraces (M. Kalayci, 

pers. comm.). 

Physiology 

A recent survey of wheat 

breeders suggested that research in 

plant physiology has had a limited 

impact on wheat improvement 

(Jackson et al., 1996). A strong body 

of evidence now indicates that 

physiological traits may have real 

potential for complementing early 

generation phenotypic selection in 

wheat. One of the more promising 

traits identified is canopy


temperature depression (CTD). 

CTD refers to the cooling effect 

exhibited by a leaf as transpiration 

occurs. While soil water status has 

a major influence on CTD, there are 

strong genotypic effects under 

well-watered, heat-stressed, or 

drought-stressed conditions. CTD 

gives an indirect estimate of 

stomatal conductance and is a 

highly integrative trait affected by 

several major physiological 

processes, including photosynthetic 

metabolism, evapotranspiration, 

and plant nutrition. CTD and 

stomatal conductance, measured 

on sunny days during grain filling, 

showed a strong association with 

the yield of semidwarf wheat lines 

grown under irrigation, in both 

temperate (Fischer et al., 1998) and 

subtropical environments 

(Reynolds et al., 1994). In addition, 

CTD, as measured on large 

numbers of advanced breeding 

lines in irrigated yield trials, was a 

powerful predictor of performance 

not only at the selection site but 

also for yield averaged across 15 

international sites. CTD has been 

shown to be associated with yield 

differences between homozygous 

lines, indicating a potential for 

genetic gains in yield, in response 

to selection for CTD (Reynolds et 

al., 1998). 

Germplasm is paramount 

Three-quarters of recently 

surveyed wheat breeders felt that a 

lack of genetic diversity would 

limit future breeding advances 

(Rejesus et al., 1996), though 

genetic diversity was not 

considered an immediately limiting 

factor in most programs. This 

concern was greater from breeders 

in developing and former USSR 

countries (>80%) than from higher 

income countries (59%). 

Furthermore, in countries where 

privatization of wheat breeding 

programs has occurred, 

investments in strategic germplasm 

development that may be risky or 

important only in the long term 

have declined (McGuire, 1997). 

A wide range of opinion has 

been expressed concerning the 

abundance or availability of 

usefully exploitable genetic 

variability. Allard (1996) 

emphasized that the most readily 

useful genetic resources were 

modern elite cultivars, since these 

lines possessed relatively high 

frequencies of favorable alleles. 

Rasmusson and Phillips (1997) 

have shown that the assumption 

that all genetic variability is a result 

of the inherent exclusive 

contribution of two parents, per se, 

is not necessarily true, considering 

results from molecular analysis. 

They discuss mechanisms by which 

induction of genetic variability may 

involve altering the expression of 

genes, the possible mechanisms of 

single allele change, intragenic 

recombination, unequal crossover, 

element transpositions, DNA 

methylation, paramutation, or gene 

amplification. They also stressed 

the possible importance of epistasis 

effects which may have been 

underestimated in the past. 

Introduction of genetic 

variability from distantly related 

wheat cultivars, or related or alien 

species, has often been specifically 

aimed at the introduction of simply 

inherited traits (e.g., genes for 

disease resistance), but it has 

appeared to be of limited value in 

quantitative trait improvement 

(Cox et al., 1997). incorporated 

genes for leaf rust resistance from 

T. tauschii into bread wheat. With 

two backcrosses to the recurrent 

wheat parent, leaf rust resistant 

winter wheat advanced lines with 

acceptable quality and equal in 

yield to the highest yielding 

commercially grown cultivars were 

identified. In addition, it has been 

postulated that since recombination 

between the D genomes of T. 

aestivum and T. tauschii occurred at 

a level similar to that in an 

intraspecific cross (Fritz et al., 

1995), T. tauschii could be 

considered another primary source 

of genes for wheat improvement. 

The number of wheat/rye 

translocations that have had a 

significant impact on wheat 

improvement are actually few in 

number. The majority of the 

1BL.1RS translocations occurring in 

more than 300 cultivars worldwide 

can be traced to one German source 

and all 1AL.1RS translocations, 

widely present in bread wheat 

cultivars grown in the Great Plains 

of the US, trace to one source, 

“Amigo” (Schlegel, 1997a,b; 

Rabinovich, 1998). Other 

translocations carry genes for 

copper efficiency (4BL.5R) and 

Hessian fly resistance (2RL.2BS, 

6RL.6B, 6RL.4B, 6RL.4A; McIntosh, 

1993). Chromosomes 2R and 7R 

enhance zinc efficiency in wheatrye 

addition lines (Cakmak and 

Braun, unpublished). Considering 

the impacts which have come from 

the use of wheat/rye 

translocations, further exploitation 

of these translocations may be 

warranted. 

While there have been reports 

indicating a positive effect of 

1BL.1RS translocations on yield 

performance and adaptation 

(Rajaram et al., 1990), Singh et al. 

(1998) determined that with Seri 82, 

replacing the translocation with 

1BL from cv. Oasis resulted in a 

yield increase of 3.4 and 5.0% in

irrigated and moisture stress 

conditions, respectively. A further 

increase in grain yield in disease 

free conditions of about 5% was 

observed in the irrigated trials 

through the introgression of 

7DL.7Ag translocation carrying the 

Lr19 gene (from Agropyron 

elongatum). This yield increase was 

attributed to higher rate of biomass 

production in the 7DL.7Ag lines. 

However, under moisture stress 

conditions 7DL.7Ag lines were 

associated with a 16% yield 

reduction, possibly due to 

excessive biomass production in 

early growth stages. This would 

suggest that the effect of the 

1BL.1RS translocation is genotype 

specific and that 7DL.7Ag could be 

a useful translocation for 

enhancing yield potential at least in 

irrigated conditions. 

Recent efforts to generate newly 

accessible genetic diversity have 

involved the reconstitution of 

hexaploid wheat by producing 

“synthetic wheat” by crossing 

durum wheat (T. turgidum), the 

donor of the A and B genomes, 

with T. tauschii, the donor of the D 

genome (Mujeeb-Kazi et al., 1996). 

Villareal (1995) and Villareal et al. 

(1997) showed that lines derived 

after two backcrosses to T. aestivum 

showed increased morphoagronomic 

variation, and resistance 

to Karnal bunt and head scab. 

Under full irrigation in 

northwestern Mexico, the yield of 

this material was nearly 8 t/ha. 

When tested under drought 

conditions for two years, nearly all 

of the synthetic derivatives had 

significantly higher 1000-kernel 

weight, with grain yield varying 

between 84 to 114%, when 

compared with the bread wheat 

checks. 


The more focused the breeding 

objective, the more restricted a 

breeder is in the choice of suitable 

parents. The use of genetically 

diverse material will continue to be 

a prime genetic source for 

increasing yield potential, a 

complex trait still not well 

understood genetically or 

physiologically. As long as breeders 

have no other readily accessible 

tools, genetic diversity and the 

opportunity for its recombination 

through crossing will be important 

to break undesired linkages and 

increase the frequency of desirable 

alleles. Future breakthroughs in 

yield potential will likely come 

from such genetically diverse 

crosses. 

Hybrid wheat 

Pickett (1993) and Picket and 

Galwey (1997) evaluated 40 years 

of wheat hybrid development and 

concluded that hybrid wheat 

production is not economically 

feasible because of a) limited 

heterotic advantage; b) lack of 

advantage in terms of agronomic, 

quality, or disease resistance traits; 

c) higher seed costs; and d) 

probably most importantly, 

heterosis could be “fixed” in 

polyploid plants and consequently 

hybrids would have no advantage 

over inbred lines. 

The use of hybrid crops is 

usually targeted to higher yield 

potential environments. Results 

from South Africa (Jordaan, 1996), 

however, show that hybrids 

outyield inbred lines by 15% at a 2 

t/ha mean production potential 

when narrow row spacing and low 

seeding rates (


Conventional plant breeders 

adopt breeding methods that 

increase their breeding efficiency 

but are conservative when making 

methodological changes. A small 

survey of wheat programs having 

unrestricted access to new 

biotechnological methods found 

that few research programs, and no 

main-line wheat breeding 

programs, routinely used MAS or 

quantitatively inherited trait loci 

(QTL). Limitation in use is caused 

by lack of markers for traits of 

interest, population specificity of a 

given marker, or markers’relatively 

high costs when compared with 

conventional selection techniques. 

These limitations may lessen in the 

next decade. 

Modern cultivars are the 

product of recombinations among 

the high number of landraces in 

their pedigrees (Smale and 

McBride, 1996). In contemporary 

breeding programs, however, 

landraces are used directly only as 

a source of qualitatively inherited 

traits. Tanksley and McCouch 

(1997) argued that the lack of 

success from crosses involving 

landraces for the improvement of 

grain yield was mainly due to 

evaluation on a phenotypic basis, 

an imprecise indicator of genetic 

potential. Analyses of QTLs have 

revealed that loci controlling a 

quantitatively inherited trait do not 

contribute equally to the observed 

variation for the trait, and often a 

few QTLs explain most of the 

observed variation. In rice, QTLs 

for yield were identified in a wild, 

low yielding relative. After 

introgression into modern hybrid 

rice cultivars, yield increases of 

17% compared to the original 

hybrid were observed. Based on 

the observed gains, Tanksley and 

McCouch (1997) identified the need 

to more thoroughly evaluate exotic 

germplasm. Those accessions most 

distinct from modern cultivars may 

contain the highest number of 

unexploited, potentially useful 

alleles. 

The comparative genetic 

mapping of cereal genomes has 

identified a vast amount of 

conserved linearity of gene order 

(Devos and Gale, 1997). This 

observation will likely accelerate 

the application of QTLs in wheat, 

as well as aid in the identification 

of genes required for introgression 

from alien species. Considering the 

low number of loci tagged today in 

wheat, the problems related to 

developing a high density map for 

wheat (Snape, 1998), and 

consequently the limited progress 

to identify QTLs for yield in wheat, 

we believe that the impact from 

this linearity on wheat 

improvement will be significant. 

Wheat has been successfully 

transformed for herbicide 

resistance and high molecular 

weight (HMW) glutenins, using 

both the ballistic and Agrobacterium 

tumefaciens systems (Cheng et al., 

1997). Barro et al. (1997) inserted 

two additional HMW glutenin 

subunits, 1Ax1 and 1Dx5, and 

observed a stepwise improvement 

of dough strength. Altpeter et al. 

(1996) introduced 1Ax1 into 

Bobwhite and increased total 

HMW glutenin subunit protein by 

71% over Bobwhite. However, the 

effects of transformation are not 

necessary additive as was shown 

by Blechl et al. (1998), who 

identified trangenics for HMW 

glutenins that also exhibited 

decreased accumulation due to 

transgene-mediated suppression. 

Conclusions 

The challenge to annually 

produce one billion tons of wheat 

within the next 25 years is 

formidable and can be met only by 

a concerted action of scientists 

involved in diverse disciplines 

(agronomy, pathology, physiology, 

biotechnology, breeding), as well as 

economics and politics. I am 

optimistic that this target will be 

met. Today, funds are directed from 

breeding towards biotechnology, 

often due simply to the novelty 

required for publication. 

Eventually, transformation may be 

a valuable technique to alter the 

performance of a genotype; 

however, at least during the next 

decade, the simple decision of a 

breeder in the field to “keep or 

discard” will contribute more to 

yield increase than any other 

approach. In conclusion, I agree 

with Ruttan (1993) who stated that 

“at least for the next two decades to 

come, progress through 

conventional breeding will remain 

the primary source of growth in 

crop and animal production.” 

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Session 1: Pathogen Biology 

Biology of the Septoria/Stagonospora Pathogens: An 

Overview 

A.L. Scharen 

Department of Plant Sciences, Montana State University, Bozeman, Montana, USA 

Abstract 

More than 2000 form-species of fungi, mostly plant parasites, comprise the genera Septoria and Stagonospora. The two 

most important pathogens in wheat production are Mycosphaerella graminicola (Septoria tritici) and Phaeosphaeria 

nodorum (Stagonospora nodorum). Primary inoculum for the wheat diseases caused by these pathogens is most often airborne 

ascospores, but may also be wind- and rain-borne conidia. Field diagnoses may be augmented and made more exact by 

use of rapid immunological tests and molecular genetic methods. Infection processes of S. tritici and S. nodorum are similar, 

but penetration by S. tritici is known only via stomata. Patterns of occurrence of the two pathogens have changed 

dramatically in recent years. Septoria tritici has become more important in northern Europe, and S. nodorum incidence has 

increased in parts of North Africa. Changes in cultivars and cultural practices are thought to be responsible for the shifts in 

pathogens and diseases. Genetics of resistance in the wheat host and virulence in the pathogen populations continues to be 

unclear. Some gene-for-gene interactions have been shown, but in field situations resistance is generally observed as nonspecific 

and pathogen populations vary most in aggressiveness. 

“Scientists build on foundations 

laid by their predecessors…, but 

they show great reluctance to 

inspect those foundations” 

(Ainsworth, 1965). Such reluctance 

was evident for many years in the 

case of the Septoria/Stagonospora 

diseases of cereal grains. 

Nineteenth and early twentieth 

century workers in Europe and 

North America described the 

pathogens and the diseases they 

cause in considerable detail. But, 

only in the years since the advent 

of cultivars bred for dwarf stature 

and high yield under conditions of 

intensive culture have the Septoria/ 

Stagonospora diseases been 

recognized as having major 

impacts upon yield and quality. 

The causal organisms are still 

called by several names, as are the 

diseases. A concise summary of the 

latest information on taxonomy 

and nomenclature was published 

in 1997 (Cunfer, 1997) and 1999 

(Cunfer and Ueng, 1999). I believe 

that we should urge from this 

venue, as did those attending the 

Fourth International Workshop on 

Septoria of Cereals (July 4-7, 1994, 

IHAR, Radzikow, Poland), that all 

workers accept and use the latest 

nomenclature. 

More than 2000 form-species of 

fungi, most of them plant parasites, 

have been assigned to the genera 

Septoria and Stagonospora. Two of 

these that attack wheat are of most 

concern to us. Losses of potential 

yield world-wide from just these 

two are estimated in the millions of 

metric tons of grain and billions of 

U.S. dollars each year. The common 

names of the diseases are septoria 

tritici blotch and stagonospora 

nodorum blotch. Classification and 

19 

nomenclature of these and other 

pathogens of cereals are given in 

Table 1 (Eyal, 1999). The Septoria 

anamorphic states have a 

teleomorphic state assigned to the 

genus Mycosphaerella, while the 

Stagonospora states have 

teleomorphic forms in the genus 

Phaeosphaeria. The teleomorphs are 

very important because they 

furnish the primary inoculum for 

disease development under specific 

environmental conditions. 

Several periods of ascospore 

deposition (both Mycosphaerella and 

Phaeosphaeria) from the atmosphere 

during the months of August to 

October in the northern 

hemisphere and February to April 

in the southern hemisphere have 

recently been shown to have critical 

importance in epidemic 

establishment (Arseniuk et al.,

20 

Session 1 — A.L. Scharen 

Table 1. Classification and nomenclature of the Septoria spp. and Stagonospora spp. fungi on small grain cereals. a 

Genus Teleomorph Anamorph Common name Host 

Septoria spp. Mycosphaerella Septoria tritici Septoria tritici Wheat 

graminicola blotch of wheat 

1998; Shaw and Royle, 1989). The 

anamorphic conidia, also called 

pycnidiospores, are most important 

as secondary inoculum locally as 

the crop is growing and are 

disseminated mainly by rain 

splash. 

Sources of primary inoculum in 

areas where the teleomorph is not 

known remain a matter of 

controversy and speculation, 

particularly in the case of septoria 

tritici blotch. Both S. nodorum and 

S. tritici are found parasitizing a 

wide range of graminaceous hosts. 

(Krupinsky, 1994; Sprague, 1950). 

Several species of grasses have 

been suspected as alternative hosts 

and inoculum sources, but the 

question is yet unresolved. Conidia 

from plant debris may act as 

primary inoculum for disease 

development in some cases. The 

fact remains to puzzle us that no 

case has been reported in which 

septoria tritici blotch and/or 

stagonospora nodorum blotch 

failed to appear because of a lack of 

primary inoculum when a 

- b Septoria tritici f. avenae Oats 

- Septoria tritici f. holci Holcus 

- Septoria tritici f. lolicola Lolium 

- Septoria passerinii Speckled leaf blotch 

of barley 

Barley 

- Septoria secalis Leaf spot of rye Rye 

Stagonospora spp. Phaeosphaeria Stagonospora nodorum Stagonospora nodorum Wheat 

nodorum blotch of wheat 

Phaeosphaeria Stagonospora avenae Oats 

avenaria f. sp. avenae 

Phaeosphaeria Stagonospora avenae Oats, wheat 

a (7) 

avenaria 

f. sp. triticea 

f. sp. triticea and triticale 

b Teleomorphic stages not found. 

susceptible crop and favorable 

environmental conditions 

prevailed. 

As late as the 1960s, diagnosis 

of Septoria diseases on wheat was 

not well developed even among 

plant pathologists and plant 

breeders. Leaf chlorosis and 

necrosis was often viewed as part 

of the natural process of 

maturation. Any of several leaf 

spotting pathogens could have 

been present and contributing to 

leaf death. When Septoria was 

recognized, it was often called 

“head septoria” which we know 

now as stagonospora nodorum 

blotch and “leaf septoria” which 

we know as septoria tritici blotch. 

Both often occur together and with 

other pathogens, and both can 

infect and cause symptoms on all 

parts of the wheat plant. 

Field diagnosis on the basis of 

symptomology is regularly done, 

but often laboratory backup, with 

microscopic examination of spores, 

is necessary for accurate diagnosis. 

As can be seen in Table 2 (Eyal, 

1997), spore size and appearance 

may overlap, so some doubts may 

remain even after microscopic 

examination. Rapid tests have been 

developed that use immunological 

techniques mainly for early 

diagnosis in intensive production 

areas where chemical control is 

commonly used. Molecular genetic 

methods have been used recently 

to show similarities and differences 

between species and forma speciales 

(Arseniuk et al., 1997; Ueng et al., 

1998.). The karyotype of S. nodorum 

suggests 14-19 chromosomes 

having approximately 0.5-3.5 

megabase pairs (Cooley and Caten, 

1991). McDonald and Martinez 

(1991) determined 14-16 bands 

believed to correspond to 

chromosomes of 0.33-3.5 megabase 

pairs in S. tritici. 

Regardless of the fact that 

morphologic and genetic 

differences of considerable 

magnitude exist between S. 

nodorum and S. tritici, histological 

studies have shown that the

Table 2. The Septoria tritici/Stagonospora nodorum pathogens of wheat. 

Pycnidium Pycnidiospore Number Chromosome 

Asexual state (µm) (µm) of septa number Lesion 

Septoria tritici 60-200 35-98 x 1-3 3-5 14-19 a Irregular to 

rectangular, 

elongated 

between veins 

Stagonospora 160-210 15-32 x 2-4 0-3 14-16b Lens shaped, 

nodorum with chlorotic 

border 

Pseudothecium Ascospore Number 

Sexual state (µm) (µm) of cells 

Mycosphaerella 

graminicola 70-100 10-15 x 2-3 2 

Phaeosphaeria 

nodorum 120-200 23-32 x 4-6 4 

a McDonald and Martinez (1991). 

b Cooley and Caten (1991). 

infection process and the 

production of pycnidia in the host 

leaf bear some remarkable 

similarities (Karjalainen and 

Lounatmaa, 1986; Kema et al., 

1996b; Straley, 1979). Usually all 

observed conidia of S. tritici on leaf 

surfaces of either resistant or 

susceptible cultivars germinated 

and produced germ tubes. The 

same can be said in the case of S. 

nodorum, but in one case (T. 

aestivum Manitou, CI 13775 

resistant spring wheat), significant 

differences were found in 

germination of conidia on leaves of 

susceptible and resistant cultivars 

(Straley, 1979). Hyphae of both 

species grow extensively over leaf 

surfaces, branching and often 

crossing stomata and guard cells 

without entering them. 

According to Kema et al. 

(1996b), penetrations of S. tritici 

were strictly stomatal and no direct 

penetrations of the cuticle were 

observed. Appressorial structures 

were seen in both pathogens, not 

associated with particular 

anatomical features, but most often 

in epidermal cracks. In the case of 

S. nodorum, direct epidermal cell 

penetrations under appressorial 

structures could not be observed 

with the light microscope, but were 

confirmed with the scanning 

electron microscope (SEM). 

Stomatal penetration by S. nodorum 

was readily observed 72 h after 

inoculation. Stomata were 

penetrated in either the open or 

closed condition, with or without 

appressoria (Harrower, 1978; 

Straley, 1979). 

Reported patterns of occurrence 

of S. nodorum and S. tritici have 

changed dramatically during the 

past 15 years. In the early 1980s, S. 

nodorum was considered most 

important in northern Europe, 

eastern USA and Western Australia, 

while S. tritici was most prevalent 

in Mediterranean climates and the 

Great Plains of North America. 

Shifts to a greater importance of S. 

tritici have occurred in the UK and 

are continuing to progress in 

central Europe. Some of the 

Biology of the Septoria/Stagonospora Pathogens: An Overview 21 

contributing factors in the UK may 

have been host susceptibility, 

earlier sowing, increased N 

fertilization and high summer 

rainfall as well as resistance to 

certain fungicides (Bayles, 1991). 

An interesting situation that 

could benefit from a systematic 

region-wide study has been 

reported from the Maghreb in 

North Africa. Populations of S. 

tritici particularly adapted to durum 

wheats have evolved, along with 

populations of S. nodorum more 

adapted to aestivum wheats. This 

phenomonon has become 

particularly obvious in Morocco, 

where a decided increase in 

plantings of bread wheats has 

occurred in recent years (Jlibene et 

al., 1995; Saadoui, 1987). 

Where sexual reproduction 

plays a role in epidemics, new 

virulence combinations can be 

selected by host virulence genes, 

and recombination of virulence 

genes will overcome “pyramids” of 

resistance genes (McDonald, 1997). 

Ahmed et al. (1996) concluded that 

S. tritici populations adapt to host 

cultivars and that susceptible 

cultivars tend to select higher levels 

of pathogen aggressiveness in the 

field. Although evidence has been 

accumulated over a long period for 

specific gene-for-gene relationships 

in the S. tritici – wheat system (Eyal 

et al., 1985; Kema et al., 1996a), the 

question remains whether 

distinctive races can be identified 

with specific virulence for 

particular cultivars and whether 

the interaction indicates a gene-forgene 

system in the S. tritici — and 

S. nodorum – wheat pathosystem 

(Johnson, 1992).

22 

Session 1 — A.L. Scharen 

The bulk of evidence continues 

to indicate that in S. nodorum — 

and S. tritici – wheat systems, genefor-gene 

interactions probably 

occur when selected cultures are 

inoculated on specific host plants 

under controlled conditions, but 

when population confronts 

population in the field, resistance 

to infection in wheat is generally 

non-specific and aggressiveness is 

the principal attribute of pathogen 

populations. 

References 

Ahmed, H.U., Mundt, C.C., Hoffer, 

M.E., and Coakley, S.M. 1996. 

Selective influence of wheat 

cultivars on pathogenicity of 

Mycosphaerella graminicola 

(anamorph Septoria tritici). 

Phytopathology 86:454-458. 

Ainsworth, G.C. 1965. Historical 

introduction to mycology. In: The 

Fungi, an Advanced Treatise. G.C. 

Ainsworth and A.S. Sussman 

(eds.). New York, Academic Press. 

748 pp. 

Arseniuk, E., Cunfer, B.M., Mitchell, 

S., and Kresovich, S. 1997. 

Characterization of genetic 

similarities among isolates of 

Stagonospora spp. and Septoria 

tritici by AFLP analysis. 

Phytopathology 87 (Suppl) S5. 

Arseniuk, E., Goral, T., and Scharen, 

A.L. 1998. Seasonal patterns of 

spore dispersal of Phaeosphaeria 

spp. and Stagonospora spp. Plant 

Disease 82:187-194. 

Bayles, R.A. 1991. Varietal resistance 

as a factor contributing to the 

increased importance of Septoria 

tritici Rob. and Desm. In the UK 

wheat crop. Plant Varieties and 

Seed 4:177-183. 

Cooley, R.N., and Caten, C.E. 1991. 

Variation in electrophoretic 

karyotype between strains of 

Septoria nodorum. Molecular and 

General Genetics 228:17-23. 

Cunfer, B.M. 1997. Taxonomy and 

nomenclature of Septoria and 

Stagonospora species on small grain 

cereals. Plant Disease 81:427-428. 

Cunfer, B.M., and Ueng, P.P. 1999. 

Taxonomy and identification of 

Septoria and Stagonospora species 

on small grain cereals. Ann. Rev. of 

Phytopathology (in press). 

Eyal, Z., Scharen, A.L., Huffman, 

M.D., and Prescott, J.M. 1985. 

Global insights into virulence 

frequencies of Mycosphaerella 

graminicola. Phytopathology 

75:1456-1462. 

Eyal, Z. 1999. Septoria and 

Stagonospora diseases of cereals: A 

comparative perspective. 

Proceedings of the 15 th Long 

Ashton International Symposium – 

Understanding Pathosystems: A 

Focus on Septoria. 15-17 September, 

1997. Long Ashton, UK. pp. 1-25. 

Harrower, K.M. 1978. Some aspects of 

the infection process and 

sporogenesis of Septoria nodorum 

and Septoria tritici. Proc. 

Australasian Septoria Workshop, 

20. Christchurch, New Zealand. 

Johnson, R. 1992. Past, present and 

future opportunities in breeding 

for disease resistance, with 

examples from wheat. Euphytica 

63:3-22. 

Jlibene, M., Mazouz, H., Farih, A., and 

Saadoui, E.M. 1995. Host-pathogen 

interaction of wheat (Triticum 

aestivum) and Septoria tritici in 

Morocco. In Proceedings of the 

Septoria tritici workshop. Gilchrist, 

L., van Ginkel, M., McNab, A., and 

Kema, G.H.J. (eds.) Mexico, D.F.: 


Karjalainen, R., and Lounatmaa, K. 

1986. Ultrastructure of penetration 

and colonization of wheat leaves 

by Septoria nodorum. Physiological 

Molecular Plant Pathology 29:263- 

270. 

Kema, G.H.J., Sayoud, R., Annone, 

J.G., and van Silfout, C.H. 1996a. 

Genetic variation for virulence and 

resistance in the wheat- 


pathosystem II. Analysis of 

interaactions between pathogen 

isolates and host cultivars. 


Kema, G.H.J., Yu, D.Z., Rijkenberg, 

F.H.J., Shaw, M.W., and Baayen, 

R.P. 1996b. Histology of the 

pathogenesis of Mycosphaerella 

graminicola in wheat. 


Krupinsky, J.M. 1994. Aggressiveness 

of Stagonospora nodorum isolates 

from alternative hosts after 

passage through wheat. 

Proceedings of the 4 th International 

Septoria of Cereals Workshop. In 

Arseniuk, E., Goral, T., and 

Czembor, P. (eds.) IHAR, 

Radzikow, Poland. pp. 123-126. 

McDonald, B.A., and Martinez, J.P. 

1991. Chromosome length 

polymorphisms in Septoria tritici 

populations. Current Genetics 

19:265-271. 

McDonald, B.A. 1997. The population 

genetics of fungi: Tools and 

Techniques. Phytopathology 

87:448-453. 

Saadoui, E.M. 1987. Physiologic 

specialization of Septoria tritici in 

Morocco. Plant Disease 71:153-155. 

Shaw, M.W., and Royle, D.J. 1989. 

Airborne inoculum as a major 

source of Septoria tritici 

(Mycosphaerella graminicola) 

infections in winter wheat crops in 

the UK. Plant Pathology 38:35-43. 

Sprague, R. 1950. Diseases of cereals 

and grasses in North America. 

Ronald Press, New York. 538 pp. 

Straley, M.L. 1979. Pathogenesis of 

Septoria nodorum (Berk.) Berk. on 

wheat cultivars varying in 

resistance to glume blotch. Ph.D. 

Thesis, Montana State University, 

Bozeman. 

Ueng, P.P., Subramaniam, K., Chen, 

W., Arseniuk, E., Lixin, W., 

Cheung, A.M., Hoffmann, G.M., 

and Bergstrom, G.C. 1998. 

Intraspecific genetic variation of 

Stagonospora avenae and its 

differentiation from S. nodorum. 

Mycol. Res. 102(5):607-614.

Molecular Analysis of a DNA Fingerprint Probe from 


S.B. Goodwin and J.R. Cavaletto 

USDA-ARS, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, USA 

Abstract 

Clones hybridizing to the Mycosphaerella graminicola DNA fingerprint probe pSTL70 were identified from 

subgenomic libraries and sequenced. Analyses of the DNA sequences of these clones plus the original pSTL70 clone revealed 

that pSTL70 contains part of the open reading frame for a probable homologue of an osmosensing histidine kinase gene from 

yeast. The remaining portion of the clone contained a partial reverse transcriptase gene sequence and a 29 base pair direct 

repeat, which could mean that the clone is a transposable element. Methods for converting transposable elements into 

improved DNA fingerprinting techniques are discussed. 

DNA fingerprinting is a 

powerful tool for analyzing the 

genetic structure of fungal 

populations. Several fingerprinting 

strategies have been employed, 

including those based on the 

polymerase chain reaction (PCR) 

such as random amplified 

polymorphic DNA (RAPD), 

amplified fragment length 

polymorphism (AFLP) and DNA 

amplification fingerprinting (DAF). 

These techniques can provide 

information on hundreds of 

potential genetic loci in a very short 

time. However, each method has 

problems that can limit its utility. 

The RAPD technique relies on 

annealing of short (only 10 base) 

primers at low temperatures. This 

leads to high variability and low 

transportability to other labs. 

AFLPs require a reasonably high 

degree of sophistication in 

expertise and facilities, and also can 

suffer from problems with 

repeatability. DAF is operationally 

simple but the large number of 

bands produced can be difficult to 

separate and interpret. 

The most widely used DNA 

fingerprint technique is restriction 

fragment length polymorphism 

analysis using small pieces of 

repetitive genomic DNA as probes. 

This technique has been used 

extensively to analyze the 

population biology of the 

ascomycetes Magnaporthe grisea 

(Hamer et al., 1989) and 


(McDonald and Martinez, 1991), 

and the oomycete Phytophthora 

infestans (Goodwin et al., 1992). 

Thousands of isolates of each 

species have been analyzed. The M. 

grisea repeat (MGR) 586 probe 

contains part of an inverted repeat 

transposon (Farman et al., 1996). 

However, the nature of the 

repeating elements in the M. 

graminicola pSTL70 and P. infestans 

RG57 probes has not been 

determined. 

This study was initiated to test 

whether the M. graminicola pSTL70 

probe was part of a transposable 

element. The long-term goal is to 

clone individual DNA fingerprint 

loci and convert them to a PCR- 

23 

based system by designing specific 

primers to unique regions at each 

genetic locus. 

Materials and Methods 

Subgenomic libraries were 

constructed from isolates IPO 323 

and 94269. These are the parent 

isolates of the M. graminicola 

mapping population (Kema et al., 

1996). Approximately 2 µg of 

genomic DNA from each isolate 

was digested to completion with 

the restriction enzyme Pst I. DNA 

fragments from 0.5-3 kb and from 

3-9 kb for each isolate were excised 

from gels and purified using 

Wizard PCR Prep (Promega, 

Madison, WI). The DNA fragments 

were then ligated into pBluescript 

vector and transformed into 

competent cells of E. coli strain 

INValphaF’. White colonies were 

transferred into 200 µL LB+amp 

medium in 96-well Microtest tissue 

culture plates and grown at 37°C 

overnight. The 96 cultures from 

each plate were transferred onto 

large (150 x 15 mm) LB+amp agar

24 

Session 1 — S.B. Goodwin and J.R. Cavaletto 

plates using a replica plater, and 

incubated upside down at 37°C 

overnight. 

Colony lifts were made onto 8 x 

12 cm pieces of Zeta Probe 

(BioRad) membranes by briefly 

laying the membrane pieces over 

the 96 colonies and lifting to pick 

up the bacteria. Membranes were 

placed colony side up onto blotting 

paper soaked with 10% SDS for 3 

min, then 0.5 M NaOH/1.5 M NaCl 

for 5 min, 0.5 M Tris, pH 8.0/1.5 M 

NaCl for 5 min, and 6x SSC for 5 

min. Finally, a UV Stratalinker 

(Stratagene) was used to crosslink 

the plasmid DNA to the membrane. 

For Southern analysis, pSTL70 

DNA was labeled using the 

Random Primer Fluorescein 

labeling kit with antifluorescein- 

HRP (DuPont NEN) and 

hybridized according to the 

manufacturer’s instructions. 

Approximately 4,000 clones (2,000 

from each isolate) were screened. 

Positive hybridizations were 

verified by digesting each positive 

clone with Pst I to release the insert, 

separating the fragments on 

agarose gels, blotting and probing 

as described above. Clones that 

hybridized after two rounds of 

screening were sequenced using a 

Pharmacia ALF automated DNA 

sequencer. 

Results 

Among 4,000 clones screened, 

five hybridized strongly to pSTL70. 

Complete sequences have been 

obtained for the original pSTL70 

clone and three others. Clones 

2E11, 9A5 and 11E8 each had large 

regions of near identity with 

pSTL70 (Table 1). However, the 

three clones shared no similarity 

with each other. BLASTX searches 

of the putative translation products 

identified a number of GenBank 

accessions with similarity to clones 

pSTL70, 2E11 and 11E8 (Table 1). 

The original pSTL70 clone had high 

similarity to a two-component 

regulator gene from yeast, Sln1, 

and a similar gene from Candida 

albicans. 

Clone 2E11 had even higher 

similarity to the same genes. This 

clone corresponded to and 

extended the 5’ end of pSTL70 

(Figure 1). Clone 11E8 

corresponded to and extended the 

3’ end of pSTL70 (Figure 1). This 

sequence may code for a reverse 

transcriptase. The final 239 bases of 

pSTL70 contained part of the 

putative reverse transcriptase 

coding sequence, but not enough of 

the gene to obtain positive BLAST 

hits in GenBank. 

Table 1. Analysis of the Mycosphaerella graminicola DNA fingerprint clone pSTL70 and three 

additional clones that hybridized to pSTL70 in Southern analysis. 

Size Overlap Blastx E 

Clone (bp) with pSTL70 results value Comments 

pSTL70 2860 N/A Sln1 8e-14 29 bp repeat 

2E11 3073 1278 Sln1 2e-15 Gene sequence 

9A5 2640 1103 No hits N/A 29 bp repeat 

11E8 1636 417 bp Reverse 0.006 Transposable 

transcriptase element (?) 

pSTL70 

2E11 

9A5 

11E8 

The first 917 bases of 11E8 are 

not related to the sequence of 

pSTL70. Clone 9A5 had no 

similarity to any sequences in 

GenBank. The first 1103 bases of 

this clone were identical to pSTL70, 

but the final 1537 bases were 

unrelated (Figure 1). Clones 

pSTL70 and 9A5 both contained a 

29 bp sequence that was tandemly 

repeated approximately 3.5 times 

(Figure 1). Southern analysis of 

genomic DNA from the parents 

and several progeny isolates of the 

M. graminicola mapping population 

revealed that 9A5 also gave a DNA 

fingerprint pattern, while 2E11 and 

16D7 did not (data not shown). 

Discussion 

The M. graminicola fingerprint 

probe pSTL70 (McDonald and 

Martinez, 1991) contains part of the 

open reading frame for the yeast 

two-component regulator gene 

Sln1. This gene has been shown to 

function as an osmosensing 

Sln 1 R 

RT 

Figure 1. Relationships among the Mycosphaerella graminicola DNA fingerprint probe pSTL70 

and related clones. Regions of overlap are indicated by open boxes, unique regions by single 

lines. Clones are labeled on the left. Approximate locations of the Sln1 and reverse 

transcriptase (RT) open reading frames are indicated by arrows. The tandem repeats are 

indicated by R.

histidine kinase in yeast, although 

its function in M. graminicola 

remains unknown. Clone 2E11 

includes an even larger portion of 

this gene containing the first 500 

amino acids of the putative yeast 

homologue. 

Other parts of the pSTL70 clone 

contain a 29 bp tandem repeat and 

a partial coding sequence for a 

reverse transcriptase. These 

indicate that pSTL70 may contain 

part of a transposable element. 

Hybridization analysis confirmed 

that this region of the clone was 

responsible for the DNA 

fingerprint pattern, which 

strengthens the transposable 

element hypothesis. The MGR586 

probe of M. grisea also has been 

shown to contain a transposable 

element flanked by 16 bp tandem 

repeats and 9 bp inverted repeat 

sequences (Farman et al., 1996). If 

pSTL70 is a transposable element, it 

is truncated partway through the 

reverse-transcriptase sequence. 

Cloning and analysis of the 

remaining portion of the reversetranscriptase 

gene will be necessary 

to test whether it is flanked by 

direct and/or inverted repeats. 

It is surprising that the three 

additional clones identified using 

pSTL70 as a probe did not overlap 

with each other. Two of the clones, 

9A5 and 11E8, contained unique 

regions that did not overlap with 

pSTL70. There are two likely 

explanations for this result. One is 

that these clones were from 

different loci in the M. graminicola 

Molecular Analysis of a DNA Fingerprint Probe from Mycosphaerella graminicola 25 

genome that shared segments due 

to independent movements of the 

putative transposable element. The 

other possibility is that one or more 

of these clones is a chimera with 

multiple inserts. The chimera 

hypothesis is being tested by 

additional analyses of the cloned 

sequences. 

If the DNA fingerprint pattern 

of pSTL70 is due to a transposable 

element, it may be possible to make 

specific PCR primers to amplify 

single DNA fingerprint loci. This 

could be accomplished using two 

different strategies. If the element is 

relatively small, primers could be 

made in the single-copy regions 

flanking the element. These should 

give a large amplification product 

when the element is present and a 

small one when it is not. Such 

differences could be resolved easily 

on agarose gels without the need 

for autoradiography, and should be 

easily transportable to other 

laboratories. 

The other approach would be to 

design one primer within the 

transposable element and the other 

in the flanking region. This would 

give a plus/minus polymorphism 

at each locus: plus when the 

transposable element is present and 

minus when it is absent. The 

advantage of this approach is that 

the primers could be designed so 

that the sizes of the PCR products 

would not overlap. It then may be 

possible to use multiplex PCR to 

perform DNA fingerprinting of 

individual genetic loci from small 

quantities of starting genomic DNA 

in single PCR reactions. This would 

be much faster and simpler than 

Southern analysis and would avoid 

the repeatability, transportability, 

and interpretation problems of 

other PCR-based methods for 

fungal population genetic analyses. 

Acknowledgments 

We thank Bruce McDonald for 

providing the original pSTL70 

DNA fingerprint clone and for 

encouragement during the course 

of this project. 

References 

Farman, M.L., S. Taura, and S.A. 

Leong. 1996. The Magnaporthe 

grisea DNA fingerprinting probe 

MGR586 contains the 3’ end of an 

inverted repeat transposon. Mol. 

Gen. Genet. 251:675-681. 

Goodwin, S.B., A. Drenth, and W.E. 

Fry. 1992. Cloning and genetic 

analyses of two highly 

polymorphic, moderately 

repetitive nuclear DNAs from 

Phytophthora infestans. Curr. Genet. 

22:107–115. 

Hamer, J.E., L. Farrall, M.J. Orbach, B. 

Valent, and F.G. Chumley. 1989. 

Host species-specific conservation 

of a family of repeated DNA 

sequences in the genome of a 

fungal plant pathogen. Proc. Natl. 

Acad. Sci., USA 86:9981-9985. 

Kema, G.H.J., E.C.P. Verstappen, M. 

Todorova, and C. Waalwijk. 1996. 

Successful crosses and molecular 

tetrad and progeny analyses 

demonstrate heterothallism in 

Mycosphaerella graminicola. Curr. 

Genet. 30:251-258. 

McDonald, B.A., and J.P. Martinez. 

1991. DNA fingerprinting of the 

plant pathogenic fungus 


(anamorph Septoria tritici). Exp. 

Mycol. 15:146-158.

26 

Characterization of Septoria tritici Variants and PCR 

Assay for Detecting Stagonospora nodorum and Septoria 

tritici in Wheat 

S. Hamza, 1 M. Medini, 1 T. Sassi, 1 S. Abdennour, 1 M. Rouassi, 1 

A.B. Salah, 1 M. Cherif, 1 R. Strange, 2 and M. Harrabi1 1 Laboratoire de Génétique, Institut National Agronomique de Tunisie, Tunisia 

2 Plant Pathology, UCL London, United Kingdom 

Abstract 

Pathogenic specialization of Septoria tritici was studied by inoculating 14 isolates of the fungus, of which seven were 

obtained from durum wheat and seven were isolated from bread wheat. Isolates obtained from durum wheat were more 

virulent on durum wheat, while those isolated from bread wheat were more severe on bread wheat, which revealed 

physiologic specialization of S. tritici to either bread or durum wheat. The sequence coding for the nuclear 5.8S rDNA and 

the internal transcribed spacer (ITS1 and ITS2) were amplified by polymerase chain reaction and sequenced for five isolates 

adapted to bread wheat and five isolates adapted to durum wheat. These sequences were identical between both variants, 

resulting in the absence of divergence inside tritici species. Septoria tritici and Stagonospora nodorum isolates collected 

from Tunisia were tested for amplification with specific primers to these pathogens. This revealed the primer’s efficiency to 

distinguish Septoria species and detect Stagonospora nodorum DNA with as little as 2 pg of DNA. Time course 

quantification of S. tritici mycelia after inoculation of resistant and susceptible cultivars distinguished those cultivars by the 

earliest date of apparition of a PCR product. 

Extensive genetic variation for 

virulence in Septoria tritici or its 

telomorph Mycosphaerella 

graminicola, characterized by 

differential interaction between 

host and pathogen genotypes, 

suggested the involvement of 

specific factors for virulence and 

resistance in the pathosystem 

(Kema et al., 1996a). Specific 

interaction between M. graminicola 

and wheat was well demonstrated 

by statistical evidence (Kema et al., 

1996b), which suggested gene-forgene 

interaction between resistance 

and virulence in host and 

pathogen, respectively. 


specialization is much more 

pronounced on bread wheat and 

durum wheat than differential 

specificity on a particular cultivar. 

In particular when considering the 

presence of pycnidia as a disease 

parameter, bread wheat and durum 

wheat isolates were particularly 

virulent on bread and durum 

wheat, respectively. Therefore 

bread wheat and durum wheat 

variants in M. graminicola were 

considered. The identical sequence 

of the internal transcribed spacer 

ribosomal DNA (ITS rDNA) 

observed by Kema et al. (1996a) 

showed that both variants could 

not be distinguished using their 

ribosomal DNA and that both were 

therefore from a similar taxonomic 

rank. 

PCR has been shown to be a 

powerful technique to detect small 

amounts of fungal plant pathogens. 

The technique is now commonly 

used by field pathologists and 

growers for diagnosing several 

plant pathogens. The early 

detection of plant disease allows 

the judicious use of agricultural 

fungicides; early treatment is often 

more effective because the 

pathogen is less well established in 

its host. PCR amplification using 

specific primers for S. tritici and 

Stagonospora nodorum or Septoria 

nodorum was able to distinguish 

these pathogens and detect a few 

fungal cells in infested wheat 

tissues well before disease 

symptoms were apparent (Beck 

and Ligon, 1995). Since both 

pathogens may infect the same 

plant and visually distinguishing 

them is difficult, the specific 

detection of S. tritici and S. nodorum 

is well circumvented using the PCR 

technique and facilitates the 

decision of whether or not to treat 

with fungicides and which 

fungicides to use.

According to the previous 

observations, this paper describes 

physiologic specialization of bread 

and durum wheat isolates collected 

from Morocco and Tunisia, 

respectively, and the sequence of 

their ITS rDNA. Specific primers 

determined by Beck and Ligon 

(1995) for PCR detection of S. tritici 

and S. nodorum were used to 

differentiate those pathogens from 

other fungal pathogens of wheat 

and to detect their presence in 

asymptomatic wheat plants. Time 

course PCR quantification of S. 

tritici in infected wheat was 

assessed to analyze the evolution of 

mycelia in resistant and susceptible 

cultivars. 


Plant material and 

experimental design 

Thirty-six durum 

wheat and eight bread 

wheat cultivars 

(Table 1) were 

employed to study 

genetic variation for 

virulence. Seeds of the 

cultivars were sown in 

trays with 228 alveolus 

with 3 cm x 3 cm 

surface and 5 cm 

height. Each alveolus 

contained four seeds. 

The experiment was 

conducted in an 

arbitrary complete 

block design with three 

replicates for each 

isolate. Replicates were 

blocked in the same 

tray, separated by two 

rows of alveolus. 

Characterization of Septoria tritici Variants and PCR Assay for Detecting Stagonospora nodorum and Septoria tritici in Wheat 27 

Experimental procedure 

Seven isolates of S. tritici taken 

from durum wheat and seven 

isolates from bread wheat collected 

in different regions of Tunisia and 

Morocco, respectively, were used to 

inoculate durum and bread wheat 

cultivars (Table 2). Eleven-day-old 

seedlings with emerging second 

leaves were inoculated with a 

monosporal suspension till run-off. 

The inoculum was prepared from 

monosporal culture cultivated on 

potato dextrose agar (PDA) 

medium. The spores were scraped 

from the agar, re-suspended in 

distilled water, filtered, and 

adjusted to 106-107 spores/ml. After 

inoculation the trays were 

incubated in a humid chamber for 

72 hours and returned to a growth 

chamber at temperature 20-25°C 

during the day, 17°C during the 

night, and 12 hours photoperiod. 

Table 1. List of durum and bread wheat cultivars used to study 

genetic variation for virulence in Mycosphaerella 

graminicola. 

Code Cultivars Code Cultivars 

01 Florence aurore* 23 Medea AC3 

02 Florence Aurore x PUSA* 24 Medea AC4 

03 Derbessi x Biskri 25 Medea AP1 

04 Guelma* 26 Medea AP2 

05 EAPC6326127* 27 Allorea* 

06 Tunis9* 28 Richelle* 

07 Tunis23* 29 Sebei glabre 

08 Abdelkader 30 Sebei pubescent 

09 Agili pubescent AC1 31 Souri AC8 

10 Bidi AP4 32 Souri AC9 

11 Bidi AP1 33 Medea AC1 

12 Bidi AP3 34 Medea AC2 

13 Bidi AP 35 Medea AP6 

14 Biskri glabre 36 Medea AP10 

15 Biskri glabre AP3 37 Medea RP1 

16 Derbessi AC1 38 Biancullida ICM27 

17 Derbessi AP1 39 Mahmoudi ICM28 

18 Derbessi AP2 40 Mahmoudi ICM67 

19 Hamira AC2 41 Khotifa x ICM75 

20 Hamira AC3 42 ICM313 

21 Hamira AC4 43 ICM314 

22 Hamira AC5 44 Hamira 

* Bread wheat cultivars. 

Disease evaluation 

and statistical analysis 

Disease severity was evaluated 

at 21 days after inoculation on the 

second leaf of the plant and using 

the presence of pycnidia as the 

disease parameter (Kema et al., 

1996a). The collected data were 

treated with SAS software (1993 

version). The presence of pycnidia 

was subjected to analysis of 

variance. The tables of means of the 

14 isolates were subjected to 

hierarchical clustering using the 

statistical analysis software CSTAT. 

DNA extraction from fungal 

spores and infected plants 

Spores of S. tritici and S. nodorum 

cultivated on PDA medium were 

subcultured in 100 ml flasks of yeast 

extract and glucose liquid medium. 

Five-day spore cultures were 

centrifuged and DNA extraction of 

fungal spores was performed using 

CTAB extraction buffer according to 

the protocol described by Morjane et 

al. (1995). DNA extraction from three 

infected leaves was performed 

according to the protocol described 

by Möller et al. (1992). DNA pellet 

after extraction was re-suspended in 

50 µl Tris-HCl; 10 mM EDTA; 1 mM 

(TE) buffer. 

PCR amplification 

and sequencing 

The sequence of ITS rDNA 

concerned 5 isolates (MAR 1, 2, 3, 4, 

5) collected from Morocco (Table 2) 

and 5 isolates (TUN 1, 2, 3, 4, 5) 

collected from Tunisia (Table 2). ITS 

amplification was performed with 

ITS1 (5’- 

TCCGTAGGTGAACCTGCGG-3’) 

and ITS 4 (5’- 

TCCTCCGCTTATTGATATGC-3’) 

universal primers. PCR reactions

28 

Session 1 — S. Hamza, M. Medini, T. Sassi, S. Abdennour, M. Rouassi, A.B. Salah, M. Cherif, R. Strange, and M. Harrabi 

Table 2. Experimental code and origin of Mycosphaerella graminicola collected from Morocco 

and Tunisia to study genetic variation for virulence. 

Isolates collected from Tunisia Isolates collected from Morocco 

Origin Origin 

Code Location Wheat species Code Location Wheat species 

TUN1 Beja DW MAR1 Jemaa Sham BT 

TUN2 Mateur DW MAR2 Douyet BT 

TUN3 Mornag DW MAR3 Agadir BT 

TUN4 El Agba DW MAR4 Ain Orma BT 

TUN5 Zaghouane DW MAR5 Azrou BT 

TUN6 Siliana DW MAR6 Essaouira BT 

TUN7 Mjez El Bab DW MAR7 Tetouan BT 

were performed in a volume of 50 

µl containing 50 mM KCl, 10 mM 

Tris-HCl, pH8.3, 1.5 mM MgCl2, 

200 µM of dNTP, 50 pmole of 

primer, 2.5 units of Taq 

polymerase (Boerhringer- 

Manheim) and 25 ng of genomic 

DNA. Reactions were run in a 

Thermolyne, Temptronic model 

thermal cycler for 30 cycles, each 

consisting of 15s at 94°C, 15 s at 

50°C, and 45 s at 72°C. An 

additional 5 min polymerization 

step at 72°C ended the 

amplification. The products were 

analyzed by electrophoresis of 20 

µl aliquot of each PCR sample on 

0.8% agarose gel. 

Specific DNA amplifications 

were performed as determined by 

Beck and Ligon (1995). ITS1 and 

JB446 (5’- 

CGAGGCTGGAGTGGTGT-3’) 

primers were used for specific 

amplification of S. tritici DNA and 

JB433 (5’- 

ACACTCAGTAGTTTACTACT-3’) 

and JB434 (5’- 

TGTGCTGCGTTCAATA-3’) were 

used to amplify S. nodorum DNA. 

PCR was performed as described 

above, except the annealing 

temperature was 57°C. 

ITS sequencing was performed 

using 90 ng of 500 bp amplified 

product with ITS1 and ITS4. The 

sequence was determined by the 

dideoxynucleotide chain 

termination method using an 

automated sequencer (Perkin 

Elmer) at the Darwin Building of 

University College London 

(London, United Kingdom). 

Fungal DNA amplification in 

resistant and susceptible 

cultivars 

To evaluate the competition of 

plant DNA with fungal DNA using 

ITS1 and ITS4 primers, 

amplification was performed using 

1 µl and 5 µl of plant DNA extract 

mixed with several amounts ( 

0.001, 0.01; 0.1; 1; 10; 100 and 1000 

ng) of fungal DNA. The PCR 

conditions were the same as 

described before with a 57°C 

annealing temperature. 

The time course amplification 

using ITS1 and ITS4 primers was 

realized using 2 µl of DNA extract 

from one infected leaf at 3, 6, 9, 14, 

18, and 22 days after inoculation. 

The PCR conditions were the same 

as described before, with a 57°C 

annealing temperature. 

Results and Discussion 

Bread wheat derived isolates 

almost exclusively produced 

pycnidia in the bread cultivars, 

whereas pycnidial production by 

durum wheat derived isolates was 

almost entirely restricted to durum 

wheat isolates. The analysis of 

variance (Table 3) shows highly 

significant differences (p

cultivars. The presence of pycnidia 

of bread wheat derived isolates 

does not exceed 15% of the leaf 

surface (data not shown). An 

explanation of the observed weak 

virulence would be long time 

conservation of these isolates in 

glycerol. Aggressivity of these 

isolates would be recovered after 

their direct isolation from infected 

leaves and inoculation from fresh 

spore culture. 

Cluster analysis of the 14 

isolates according to the presence 

of pycnidia resulted in nine 

different clusters. Bread wheat 

derived isolates are clearly 

separated from durum wheat 

derived isolates (Figure 1). Durum 

wheat isolates are clustered into six 

groups. Two isolates (TUN7 and 

TUN6) originated from distant 

regions (Mjez El Bab and Siliana, 

respectively) belong to the same 

group, whereas isolates from the 

same regions belong to different 

216.7 

150 

100 

Figure 1. Hierarchical classification of 14 

Septoria tritici isolates as determined by 

CSTAT software. 


50 

MAR1 

MAR2 

MAR3 

MAR5 

MAR4 

MAR6 

MAR7 

TUN7 

TUN6 

TUN4 

TUN5 

TUN3 

TUN2 

TUN1 

0.0 

groups, indicating genetic variation 

for virulence within local 

populations. 

ITS sequence analysis 

Physiological specialization of 

S. tritici to bread wheat and durum 

wheat led to the hypothesis of the 

existence of two subspecies inside 

tritici. For that purpose sequencing 

ITS rDNA would provide evidence 

about the taxonomy of those 

variants. The comparison of the 

consensus sequence of the 550 pb 

ITS region fragments obtained from 

five bread wheat derived isolates 

and five durum wheat derived 

isolates shows 100% homology 

(Figure 2). Therefore S. tritici 

variants belong to the same 

taxonomic rank and cannot be 

considered as two different 

subspecies of tritici. Since both 

variants coexist in the same field 

(McDonald, personal 

communication), permanent 

Figure 2. Nucleotide sequence of the internal transcribed spacer region derived from bread 

wheat (MAR) and durum wheat (TUN) derived isolates of Septoria tritici. The sequence includes 

the 5.8S rDNA gene and the internal transcribed spacer (ITS1 and ITS2). The consensus 

sequences were deduced from bread wheat and durum wheat derived isolates each.

30 

Session 1 — S. Hamza, M. Medini, T. Sassi, S. Abdennour, M. Rouassi, A.B. Salah, M. Cherif, R. Strange, and M. Harrabi 

Figure 2. cont. 

conversion of one variant to the 

other by genetic exchange of 

virulence genes may occur through 

sexual reproduction. 

Diagnosis of S. tritici 

and S. nodorum 

In order to investigate the 

specificity of S. tritici and S. 

nodorum specific primers 

determined by Beck and Ligon 

(1995), we examined whether they 

produce PCR products from other 

fungal pathogens of wheat, such as 

Fusarium graminearum, Ustilago 

maydis, and Puccinia graminis. The 

S. tritici specific primers JB446 and 

ITS1, and S. nodorum specific 

primers JB433 and JB434 did 

produce PCR products only 

from those pathogens (Figure 

3) revealing that these 

primers can be used to 

diagnose S. tritici and S. 

nodorum isolates collected 

from Tunisia. 

Amounts ranging from 2 

µg to 2 pg of S. nodorum were 

tested by PCR amplification with 

their respective specific primers 

(JB433, JB434) to determine the 

DNA threshold that can be 

detected. PCR amplification with 

550 bp 

JB446 and ITS1 JB433 and JB434 

Labda HindIII 

Healthy wheat 

Septoria tritici 

Stagonospora nodorum 

Fusarium graminearum 

Puccinia graminis 

Ustilago maydis 

Lambda HindIII 

Healty wheat 



Fusarium graminearum 

Puccinia graminis 

Ustilago maydis 

Lambda HindIII 

Figure 3. Ethidium bromide stained agarose gel of 

polymerase chain reaction amplification product 

using Septoria tritici specific primers (JB446 and 

ITS1) and Stagonospora nodorum specific primers 

(JB433 and JB434) with healthy wheat DNA and 

fungal DNA of wheat pathogen. 

Lambda DNA HindIII 

2 µg 

200 ng 

20 ng 

2 ng 

200 pg 

20 pg 

2 pg 

Lambda DNA HindIII 

Figure 4. Ethidium bromide stained agarose gel of 

polymerase chain reaction products from 

amplification of 0.2 pg to 2 µg of genomic DNA of 

Stagonospora nodorum DNA using S. nodorum 

specific primers JB433 and JB434. 

JB433 and JB434 was able to detect 

2 pg of S. nodorum DNA (Figure 4), 

which is almost the same amount 

detected by Beck and Ligon (1995).

Provided that S. nodorum fungal 

genomes do not exceed 100 Mbp in 

those conditions, PCR is able to 

detect as little as 20 fungal cells. 

Fungal DNA amplification in 

resistant and susceptible 

cultivars 

Different fragment sizes 600 bp 

and 550 bp amplification products 

were obtained from plant and 

fungal DNA, respectively, using 

ITS1 and ITS4 primers (Figure 5). 

PCR amplification with ITS primers 

and using a mixture of both fungal 

and plant DNA templates resulted 

in the amplification of both 

fragments. However, the intensity 

of the fungal PCR product is 

relative to the amount of fungal 

DNA (Figure 5). These result 

suggest that plant DNA could be 

used as competitor of fungal DNA 

amplification with ITS primers. 

Time course PCR amplification 

using ITS1 and ITS4 primers at 0, 3, 

6, 9, 14, 18, and 22 days after 

inoculation of susceptible (Karim) 

and resistant (Jennah Khotifa) 

cultivars with S. tritici is shown in 

Figure 6. ITS rDNA amplification 

products from fungal DNA (550 bp) 

appeared at 3 and 18 days from 

infected susceptible and resistant 

cultivars, respectively. 

This result showed that the 

multiplication of S. tritici inside the 

plant is delayed in the resistant 

cultivar. Therefore, the time 

interval corresponding to the 

beginning of PCR product 

apparition may be an indicator of 

resistance. Furthermore, the 

intensity of the PCR product 

increased with the days postinoculation 

(Figure 6), indicating a 

quantitative response of the PCR 


600 bp 

550 bp 

1000 ng 

100 ng 

10 ng 

1 ng 

0.1 ng 

0.01 ng 

0.001 ng 

Figure 5. Ethidium bromide stained agarose 

gel of polymerase chain reaction products 

using ITS1 and ITS4 primers with 0.0001 to 

1000 ng fungal DNA of Septoria tritici and 1 µl 

plant DNA extract from healthy wheat leaves. 

550 bp and 600 bp are ITS rDNA amplification 

products from Septoria tritici and wheat, 

respectively. 

Days after inoculation 

0 3 6 9 14 18 22 

600 bp 

550 bp 

Karim 

600 bp Jennah 

550 bp Khotifa 

Figure 6. Ethidium bromide stained agarose 

gel of time course PCR amplification 

products using ITS1 and ITS4 primers with 

Septoria tritici infected wheat (susceptible; 

Karim and resistant; Jennah Khotifa) DNA. 

550 bp and 600 bp are ITS rDNA amplification 

products from S. tritici and wheat, 

respectively. 

assay. These observations are 

preliminary results towards a 

quantification of fungal 

proliferation within tissue to 

rapidly characterize varying levels 

of host resistance. Characterization 

of host resistance by measuring the 

fungal biomass inside wheat leaves 

was tested using ELISA (Kema et 

al., 1996c). This technique did not 

detect the fungal antigen within the 

48 h-8 dpi interval, although a 

slight increase of the fungal tissue 

was observed microscopically during 

that interval. Thus the ability of PCR 

to detect fungal mycelia in a 

susceptible cultivar at 3 dpi better 

reflects the colonization of wheat 

cells by the fungus. These 

preliminary results will also help 

establish an efficient protocol for 

fungicide utilization. Effective 

utilization of fungicides would 

decrease or maintain the intensity of 

the PCR product a long time after its 

application. 

References 

Beck, J.J., and J.M. Ligon. 1995. 

Polymerase chain reaction assays for 

the detection of Stagonospora 

nodorum and Septoria tritici in wheat. 


Kema, G.H.J., J.G. Annone, R. Sayoud, 

C.H. van Silfhout, M. van Ginkel, 

and J. Bree. 1996a. Genetic variation 

for virulence and resistance in the 

wheat-Mycosphaerella graminicola 

pathosystem I. Interaction between 

pathogen isolates and host cultivars. 


Kema, G.H.J., R. Sayoud, J.G. Annone, 

and C.H. van Silfhout. 1996b. 





interactions between isolates and 

host cultivars. Phytopathology 

86:213-219. 

Kema, G.H.J., D. Yu, F.H.J. Rijkenberg, 

M.W. Shaw, and R.P. Baayen. 1996c. 

Histology of the pathogenesis of 

Mycosphaerella graminicola in wheat. 


Morjane, H., J. Geistlinger, M. Harrabi, 

K. Weising, and G. Kahl. 1995. 

Oligonucleotide fingerprinting 

detects genetic diversity among 

Ascochyta rabiei isolates from a single 

chickpea field in Tunisia. Curr. 

Genet. 26:191-197. 

Möller, E.M., G. Bahnweg, H. 

Sanderman, and H.H. Geiger. 1992. 

A simple and efficient protocol for 

solation of high molecular weight 

DNA from filamentous fungi, fruit 

bodies and infected plant tissue. 

Nucleic Acids Res. 20:6115-6116.

32 

Populations of Septoria spp. Affecting Winter Wheat in 

the Forest-Steppe Zone of the Ukraine 

S. Kolomiets* 

Institute of Plant Protection, Ukrainian Academy of Agrarian Sciences, Kiev, Ukraine 

Abstract 

Data in the literature and results of our investigations indicate that septoria leaf blotch of winter wheat has been reported 

annually in the forest-steppe zone of the Ukraine. Septoria tritici is the predominant species among the causal agents of 

septoria leaf blotch of winter wheat. However, the portion caused by Stagonospora nodorum increased to 23-44% in recent 

years. 

Septoria tritici, the pathogen that 

causes leaf blotch, and Stagonospora 

nodorum, the pathogen that induces 

spike and leaf blotch, are the most 

widespread pathogens of winter 

wheat in the forest-steppe zone of 

the Ukraine. 

Septoria spp. induce a decrease 

in assimilation surface, 

developmental retardation, 

premature leaf desiccation, and 

1000-grain weight. In epidemic 

years, yield losses may reach 30– 

50%. Total yield losses caused by 

these pathogens all over the world 

are estimated at 9 million tons. 

Developing cultivars resistant 

to the pathogens and establishing 

their cultivation is impossible 

without investigating the 

composition of pathogenic species 

in a given area and systematically 

recording its changes. Climatic 

conditions, the composition of 

biocenoses, and the substrate 

where pathogens develop 

significantly affect the ratio 

between species. In the literature 

data on the areas occupied by the 

pathogens are quite limited, but 

can be found in articles published by 

Kovalenko (1975), Vasetskaja et al. 

(1983), Dyak (1990), and Sanina and 

Antsiferova (1991). 

In 1995–97, we investigated the 

composition of Septoria pathogens in 

the forest-steppe zone of the Ukraine 

(Kyiv, Cherkasy, Vinnytsya, 

Khmelnytskyy, Ternopil, Zhytomyr, 

and Poltava regions). Studies were 

conducted on promising and 

cultivated cultivars of winter wheat 

using routine methodologies. The 

species were identified via 

evaluation of stable traits: form, 

length, and width of conidia and 

ends. 

Our research demonstrated that 

the forest-steppe zone of the Ukraine 

is occupied by both Septoria 

pathogens, but S. tritici 

predominated in the 1970s, while S. 

nodorum was found only in certain 

years (Kovalenko, 1975). In the 1980s 

S. nodorum was reported in Kyiv (30- 

36%) and Ternopil (13-23%) regions 

(Dyak, 1990). In Cherkasy region 

(6.6%) the pathogen was reported 

only in certain years and was not 

detected at all in Vinnytsya region. 

* Author prevented from attending workshop by unforeseen travel problems. 

In the mid 1990s, the proportion 

of S. nodorum increased among the 

species. Septoria tritici dominated in 

all investigated regions: the highest 

percentage was reported in 

Vinnytsya region (76%), while the 

lowest was reported in Ternopil 

region (53%). In Kyiv, Cherkasy, 

Poltava, Khmelnytskyy, and 

Zhytomyr regions, it reached 68, 

65, 69, 72, and 72%, respectively 

(Figure 1). Data from the literature 

and our own research results 

indicate an increase in the area 

occupied by S. nodorum, as well as 

in its ratio of Septoria pathogens 

present. 

Changes in the ratio of the 

pathogens may be explained by 

changes in climatic conditions, the 

range of cultivars used and, 

possibly, by the spread of S. 

nodorum infection through seeds, 

especially in recent years, when 

seeds were not properly treated. 

Thus the spread of S. nodorum–the 

most aggressive and damaging 

Septoria pathogen–increased under 

the above conditions.

;; yy 

;; yy 

6 

28% 

1 

32% 

;y; ; y y ; ; y y 28% 

31% 

68% 

72% 

2 

72% 

; y 35% 69% ;y 

44% 23% 65% 

3 

77% ;y ;y 4; 

y 

56% 

5 



7 

Figure 1. The proportion between leaf septoriose pathogens of winter wheats in the foreststeppe 

zone of the Ukraine. 

1-Kyiv, 2-Poltava, 3-Cherkasy, 4-Vinnytsya, 5-Ternopil, 6-Khmelnytskyy, 7-Zhytomyr regions. 

Populations of Septoria spp. Affecting Winter Wheat in the Forest-Steppe Zone of the Ukraine 33 

References 

Dyak, U.P. 1990. Distribution of the 

basic inducers of septoriosis on a 

winter wheat in Ukrainian SSR. 

Zaschitz rasteniy 3:7-9. 

Kovalenko, S.N. 1975. Septoria leaf 

blotch of a winter wheat in 

requirements forest-steppe zone of 

Ukraine SSR. Avtoreferat 

diss…kand. biol. nauk. Kiev, 21 p. 

Sanina, A.A., and Antsiferova, L.V. 

1991. Septoria Sacc. species on 

wheat in the European part of the 

USSR. Mikilogia i fitopatologia 

25(3):250-252. 

Vasetskaja, M.N., Kulikova, G.N., and 

Borzionova, T.I. 1983. Septoria 

species of fungi distributed on 

grades of wheat in the USSR. 

Mykologia i phytopatologia 

17(3):210-213.

34 

Septoria passerinii Closely Related to the Wheat 

Pathogen Mycosphaerella graminicola 

S.B. Goodwin and V.L. Zismann 

USDA-ARS, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, USA 

Abstract 

Septoria passerinii is known only from its anamorphic Septoria state; no teleomorph has been identified. In culture, S. 

passerinii looks very similar to Mycosphaerella graminicola from wheat. Comparisons of the nucleotide sequences of the 

internal transcribed spacer (ITS) regions of the ribosomal DNA of both species and of many other fungi in the Dothideales 

revealed that the ITS regions of S. passerinii and M. graminicola differed by only 10 bases out of 571 total. Therefore, these 

species are very closely related. Phylogenetic analysis showed that S. passerinii and M. graminicola grouped together within 

a large cluster of Mycosphaerella species. Thus, S. passerinii almost certainly has a Mycosphaerella teleomorph. 

Septoria passerinii causes 

speckled leaf blotch on barley. The 

colony and conidial morphologies 

of S. passerinii and the wheat 

pathogen Mycosphaerella graminicola 

are very similar. Both are 

pathogens of cereals, and they may 

be closely related. However, 

nothing is known about the 

evolutionary relationships of S. 

passerinii (Cunfer and Ueng, 1999); 

no fruiting structures have been 

found and its teleomorph remains 

unknown. 

Analyses of the internal 

transcribed spacer (ITS) region of 

ribosomal DNA have been very 

useful for elucidating the 

phylogenetic relationships of fungi. 

This region contains the highly 

variable ITS1 and ITS2, separated 

by the conserved 5.8S ribosomal 

RNA gene, and is bounded by the 

highly conserved 18 and 28S 

ribosomal RNA genes. This greatly 

facilitates analysis, because 

polymerase chain reaction (PCR) 

primers within the conserved 

regions of the 18 and 28S genes 

amplify the intervening ITS region 

of approximately 600 bp. 

Furthermore, many fungal ITS 

sequences are available in 

GenBank, which expands the 

number of species available for 

comparison. 

The objective of this research 

was to assemble a database of ITS 

sequences to test the hypothesis 

that S. passerinii is a close relative of 

M. graminicola. The alternative 

hypothesis is that S. passerinii could 

be more closely related to other 

cereal pathogens, such as the 

septoria nodorum pathogen of 

wheat and barley, Phaeosphaeria 

nodorum. 


Isolates of species of 

Mycosphaerella, Leptosphaeria, and 

Phaeosphaeria were obtained from 

various sources (Table 1). DNA was 

extracted from lyophilized tissue 

and the ITS regions were amplified 

using primers ITS4 and ITS5. 

Amplification was with the 

following cycling parameters: 94 C 

for 2 min, 30 cycles of 93 C for 30 s, 

53 C for 2 min, 72 C for 2 min, and 

a final extension of 10 min at 72 C. 

Amplification products were 

purified and cloned. Each clone 

was sequenced in both directions 

on an automated DNA sequencer 

and several clones were sequenced 

per isolate. 

DNA sequence alignment, 

genetic distance calculation, 

bootstrap analysis (1000 

replications), and a neighborjoining 

tree was prepared using 

Clustal X (http://www-igbmc.ustrasbg.fr/BioInfo/ClustalX/ 

Top.html). The final tree was 

printed using NJplot. 

Results 

The ITS regions of all S. 

passerinii isolates were 571 bases 

long, including the primer regions, 

and were essentially identical. A 

BLAST search on GenBank 

identified M. graminicola as the 

closest match to S. passerinii. 

Sequences of other species showing 

good matches with S. passerinii in 

the BLAST search were 

downloaded from GenBank, along 

with those of species of 

Leptosphaeria, Phaeosphaeria, and 

other fungi in the Dothideales 

(Table 1). A multiple alignment 

revealed that the ITS sequences of 

S. passerinii and M. graminicola 

differed by only 10 bases (data not

Table 1. Sources of isolates or DNA sequences for the internal transcribed spacer database of 

Septoria passerinii, Mycosphaerella graminicola, and other fungi in the Dothideales. 

Species Isolate Growth medium Source 

Cladosporium caryigenum LCF — GenBank 

Cladosporium herbarum MZKI B-1002 — GenBank 

Cladosporium sphaerospermum MZKI B-1005 — GenBank 

Dothidea hippophaeos CBS 186.58 — GenBank 

Dothidea insculpta CBS 189.58 — GenBank 

Hormonema dematioides — — GenBank 

Leptosphaeria bicolor — — GenBank 

Leptosphaeria conteca — Malt broth ATCC 

Leptosphaeria doliolum — — Genbank 

Leptosphaeria maculans — — Genbank 

Leptosphaeria microscopica — — Genbank 

Mycosphaerella citri — Yeast malt broth Tobin Peever 

Mycosphaerella fijiensis — PDB ATCC 

Mycosphaerella graminicola — — GenBank 

Mycosphaerella graminicola IPO323 Yeast malt broth Gert Kema 

Mycosphaerella graminicola T1 Yeast malt broth Minnesota 

Mycosphaerella graminicola T48 Yeast malt broth Indiana 

Mycosphaerella musicola — PDB ATCC 

Mycosphaerella pini — — GenBank 

Mycosphaerella tassiana CBS 111.82 — GenBank 

Ophiosphaerella herpotricha — — GenBank 

Ophiosphaerella korrae — — GenBank 

Phaeosphaeria avenaria — — GenBank 

Phaeosphaeria halima — Emerson YpSs ATCC 

Phaeosphaeria nodorum — — GenBank 

Phaeosphaeria spartinae — Emerson YpSs ATCC 

Phaeosphaeria typharum — Emerson YpSs ATCC 

Phaeotheca triangularis MZKI B-950 — GenBank 

Rhizopycnis vagum — — GenBank 

Septoria passerinii 22585 Yeast malt broth ATCC 

Septoria passerinii 26516 Yeast malt broth ATCC 

Septoria passerinii P70 Yeast malt broth North Dakota 


Septoria passerinii P78 Yeast malt broth Minnesota 


Trimmatostroma salinum MZKI B-962 — GenBank 

shown). The neighbor-joining tree 

showed that S. passerinii and M. 

graminicola clustered together along 

with most of the other 

Mycosphaerella species (Figure 1). 

Phaeosphaeria nodorum was in a very 

different cluster that mostly 

contained species of Phaeosphaeria, 

Leptosphaeria, and Ophiosphaerella 

(Figure 1). Bootstrap analysis 

indicated strong support for all of 

the major clusters (Figure 1). 

Discussion 

These data clearly indicate that 

S. passerinii and M. graminicola are 

very closely related. Because these 

two taxa were deeply embedded 

within a large cluster of 

Septoria passerinii Closely Related to the Wheat Pathogen Mycosphaerella graminicola 35 

Mycosphaerella species, it seems 

certain that S. passerinii has, or was 

derived from a progenitor that had, 

a Mycosphaerella teleomorph. This 

must be confirmed by searching for 

the Mycosphaerella stage on infected 

barley tissue. 

In addition to elucidating the 

evolutionary relationships of S. 

passerinii, the cluster analysis raises 

a number of interesting questions. 

For example, Phaeosphaeria, 

Leptosphaeria, and Ophiosphaerella 

form a large cluster. However, it is 

not clear whether Phaeosphaeria 

warrants a separate generic 

designation. Clarifying the 

relationships among the mitosporic 

Dothideales (those with no known 

sexual stage) will require a larger 

number of species and a more 

comprehensive analysis. Aligning 

the 5.8S and ITS2 regions was fairly 

straightforward. However, ITS1 

varied greatly in length, which 

made alignment difficult. The 

alignment used for the cluster 

analysis presented here has not 

been optimized and, thus, should 

be considered preliminary. 

However, the close relationship 

between S. passerinii and M. 

graminicola is certain. 

Reference 

Cunfer, B.M., and Ueng, P.P. 1999. 

Taxonomy and identification of 

Septoria and Stagonospora on small 

grain cereals. Annual Review of 

Phytopathology (in press).

36 

Session 1 — S.B. Goodwin and V.L. Zismann 

0.05 

100 

96 

100 

100 

97.4 

100 

100 

100 

100 

100 

100 

100 

100 

99.9 

99.6 

Leptosphaeria bicolor 

Leptosphaeria conteca 

Ophiosphaerella korrae 

Ophiosphaerellaherpotricha 

Phaeosphaeria typharum 

Phaeosphaeria halima 

Phaeosphaeria avenaria 

Phaeosphaeria nodorum 

Phaeosphaeria spartinae 

Leptosphaeria microscopica 

Leptosphaeria maculans 

Leptosphaeria doliolum 

Rhizopycnis vagum 

Septoria passerinii P78 






Mycosphaerella graminicola T1 


Mycosphaerella graminicola IPO 

Mycosphaerella graminicola T48 

Mycosphaerella citri 

Mycosphaerella musicola 

Mycosphaerella fijiensis 

Mycosphaerella pini 

100 Dothidea hippophaeos 

Dothidea insculpta 

Hormonema dematioides 

Mycosphaerella tassiana 

Cladosporium herbarum 

Cladosporium sphaerospermum 

Trimmatostroma salinum 

Phaeotheca triangularis 

Cladosporium caryigenum 

Figure 1. Phylogenetic analysis of sequences of the internal transcribed spacer region of the ribosomal DNA of 

Septoria passerinii, Mycosphaerella graminicola and other fungi in the Dothideales. All bootstrap values 

above 90% are indicated.

Septoria/Stagonospora Leaf Spot Diseases on Barley in 

North Dakota, USA 

J.M. Krupinsky1 and B.J. Steffenson2 (Poster) 

1 USDA, Agricultural Research Service, Northern Great Plains Research Laboratory, Mandan, ND, USA 

2 Dept. of Plant Pathology, North Dakota State Univ., Fargo, ND, USA 

Abstract 

Diseased barley leaves were collected from fields in North Dakota in 1998. The most common Septoria/Stagonospora 

diseases were septoria speckled leaf blotch (Septoria passerinii) and stagonospora avenae leaf blotch (Stagonospora 

avenae f. sp. triticea). Net blotch (Drechslera teres) and spot blotch (Bipolaris sorokiniana) were also commonly 

present. Stagonospora nodorum blotch (Stagonospora nodorum) and tan spot (Drechslera tritici-repentis), which are 

major diseases on wheat in the area, were detected on barley but at rather low levels. When isolates of S. nodorum from 

barley were tested on wheat and barley in greenhouse inoculations, higher symptom severity ratings were obtained on wheat 

compared to barley, indicating that the isolates obtained from barley were probably wheat-type isolates. Because of the 

importance of both Septoria passerinii and Stagonospora avenae f. sp. triticea on barley, selecting barley for Septoria/ 

Stagonospora resistance will require screening with both organisms. 

Barley (Hordeum vulgare L.) can 

be affected by a number of plant 

diseases that can cause economic 

losses in yield and quality. The 

Septoria/Stagonospora diseases 

common on barley are septoria 

speckled leaf blotch (Septoria 

passerinii Sacc.), stagonospora 

avenae leaf blotch (Stagonospora 

avenae Bissett f. sp. triticea T. 

Johnson [syn. Septoria avenae A.B. 

Frank f. sp. triticea T. Johnson]), and 


(Stagonospora nodorum [Berk.] 

Castellani & E.G. Germano [syn. 

Septoria nodorum {Berk.} Berk. in 

Berk & Broome]) (Kiesling, 1985; 

Mathre, 1997). Barley-type isolates 

of S. nodorum have also been 

identified (Cunfer and Youmans, 

1983; Smedegard-Peterson, 1974). A 

cooperative survey was undertaken 

to determine the importance of 

Septoria/Stagonospora leaf spot 

diseases common on barley in 

North Dakota. 


Diseased barley leaves (green 

leaves with leaf spots) were 

gathered from naturally-infected 

barley plants in the field in 1998. 

Leaves were collected from 70 

fields located in the southwestern, 

central, northeastern, and eastern 

areas of North Dakota. Collected 

leaves were dried and stored dry at 

4C in a refrigerator until processed. 

Leaf sections, 2 cm long, from 

approximately 8 leaves per 

collection, were processed. Leaf 

sections were surface-sterilized for 

3 min in a 1% sodium hypochlorite 

solution containing a surfactant, 

rinsed in sterile distilled water, 

plated on 2% water agar in plastic 

Petri dishes, and incubated under a 

12-h photoperiod (cool-white 

fluorescent tubes) at 21C. After 7 

days, leaf sections were examined 

for fungi. Pycnidiospores from 

pycnidia on the leaf sections were 

identified microscopically. The 

presence of Drechslera teres (Sacc.) 

Shoemaker, Bipolaris sorokiniana 

(Sacc.) Shoemaker, and D. tritici- 

37 

repentis (Died.) Shoemaker was also 

noted. Two to four fungal species 

were present on some leaf sections. 

Isolates were obtained, grown, 

stored, and inoculum was prepared 

as described by Krupinsky (1997). 

Nine isolates of S. nodorum 

obtained from barley were 

compared in glasshouse 

inoculations of wheat and barley 

seedling plants. Two wheat 

cultivars, Eureka and Fortuna, and 

two barley cultivars, Bowman and 

Hector, were used. In a glasshouse, 

seedlings were planted, grown, 

fertilized, inoculated, incubated, 

and assessed for percentage 

necrosis of the first leaf as 

previously reported (Krupinsky 

1997). 


Of the 531 leaf sections 

processed, 45% were infected with 

S. passerinii, 37% with S. avenae f. 

sp. triticea, and 14% with S. 

nodorum. Drechslera teres, B. 

sorokiniana, and D. tritici-repentis

38 

Session 1 — J.M. Krupinsky and B.J. Steffenson 

were identified on 55, 51, and 10% 

of the leaf sections, respectively. 

Using the number of leaf sections 

infected with a particular fungus as 

an indicator of the relative 

importance of a fungus, the most 

common diseases making up the 

leaf-spot disease complex on barley 

in North Dakota were in 

descending order of importance net 

blotch, spot blotch, septoria 

speckled leaf blotch, and 

stagonospora avenae leaf blotch. 

This ranking was similar to those in 

Saskatchewan, Canada, north of 

western North Dakota, where D. 

teres was considered the most 

common leaf spotting pathogen, 

followed by B. sorokiniana, which 

was more common than Septoria 

spp. (Fernandez et al., 1999). In 

Manitoba, Canada, north of eastern 

North Dakota, leaf spot diseases 

were considered to cause minimal 

damage in 1998. Drechslera teres and 

B. sorokiniana were found in 90-93% 

of the barley fields and S. passerinii 

was recovered in 22% of the fields 

(Tekauz et al., 1999). 

Two of these diseases, spot 

blotch and stagonospora avenae 

leaf blotch, are usually minor 

diseases on wheat in central North 

Dakota. Stagonospora nodorum 

blotch and tan spot, although major 

diseases on wheat in North Dakota, 

were only isolated at low levels 

from barley and are not considered 

to be serious problems on barley at 

the present time. Because of the 

importance of both S. passerinii and 

S. avenae f. sp. triticea on barley in 

North Dakota, selecting barley for 

Septoria/Stagonospora resistance will 

require screening with both 

pathogens. 

The nine isolates of S. nodorum 

obtained from barley consistently 

produced higher symptom severity, 

as measured by percentage 

necrosis, on wheat than on barley. 

Overall, Fortuna averaged 28% 

necrosis and Eureka averaged 29% 

necrosis, compared to less than 1% 

for Bowman and Hector. 


The authors thank D. Wetch for 

technical assistance, as well as D.E. 

Mathre and M. Babadoost for their 

reviews and constructive 

comments. 

Mention of a trademark, 

proprietary product, or company 

by USDA personnel is intended for 

explicit description only and does 

not constitute a guarantee or 

warranty of the product by the 

USDA and does not imply its 

approval to the exclusion of other 

products that may also be suitable. 

USDA-ARS, Northern Plains Area, 

is an equal opportunity/ 

affirmative action employer and all 

agency services are available 

without discrimination. 

References 

Cunfer, B.M., and Youmans, J. 1983. 

Septoria nodorum on barley and 

relationships among isolates from 

several hosts. Phytopathology 

73:911-914. 

Fernandez, M.R., Celetti, M.J., and 

Hughes, G. 1999. Leaf diseases of 

barley and oat in Saskatchewan in 

1998. Can. Plant Dis. Survey 79:75- 

77. 

Kiesling, R.L. 1985. The diseases of 

barley. Chapter 10, pages 269-312. 

In: Barley. D.C. Rasmusson, ed. 

American Soc. of Agronomy. 

Madison, WI. 522 pages. 



obtained from wheat in the 

Northern Great Plains. Plant 

Disease 81:1027-1031. 

Mathre, D.E., 1997. Compendium of 

Barley Diseases. Second edition. 

The American Phytopathological 

Society, APS Press, St. Paul, MN. 

90 pages. 

Smedegard-Peterson, V. 1974. 

Leptosphaeria nodorum (Septoria 

nodorum), a new pathogen on 

barley in Denmark, and its 

physiologic specialization on 

barley and wheat. Friesia 10:251- 

264. 

Tekauz, A., McCallum, B., Gilbert, J., 

Mueller, E., Idris, M., Stulzer, M., 

Beyene, M., and Parmentier, M. 

1999. Foliar diseases of barley in 

Manitoba in 1998. Can. Plant Dis. 

Survey 79:74.

Interrelations among Septoria tritici Isolates of 

Varying Virulence 

S. Ezrati, S. Schuster, A. Eshel, and Z. Eyal (Poster) 

Department of Plant Science, Tel Aviv University, Israel 

Reduction in pycnidial 

coverage on Seri 82 was found by 

Halperin et al. (1996) after 

inoculation with two Septoria tritici 

isolates: ISR398 (avirulent) and 

ISR8036 (virulent). Cross protection 

was suggested as a mechanism for 

the suppression phenomenon, 

triggered by the avirulent isolate. 

The aim of the current study was to 

investigate possible interactions 

between new isolates of S. tritici on 

Seri 82 and other wheat cultivars. 

Co-inoculations with mixtures 

of isolates were conducted on 

seedlings and maturing plants of 

various cultivars. The following S. 

tritici isolates and wheat cultivars 

were used: 

• ISR398 - avirulent on Seri 82, 

KK, Bobwhite “S” and IAS20; 

virulent on Shafir. 

• ISR8036 - avirulent on KK, 

Bobwhite “S” and IAS20; 

virulent on Shafir and Seri 82. 

• ISR9812 - avirulent on IAS20; 

virulent on Shafir, Seri 82, KK and 

Bobwhite “S”. 

• ISR9840 - avirulent on KK and 

Bobwhite “S”; virulent on Shafir, 

Seri 82 and IAS20. 

Pairs of isolates were used for 

inoculation with 1:1 mixtures on 

each of the five cultivars. Pycnidial 

coverage by the virulent isolate of 

each pair was used as a reference. 

The results are shown in Table 1. 

Significant suppression of pycnidial 

coverage was observed when 

seedlings were inoculated with 

mixtures composed of a virulent and 

an avirulent isolate. However, no 

suppression was found when isolate 

ISR9840 was used as the virulent 

component. Since all isolates were 

virulent on Shafir, no suppression 

was found on this cultivar. 

Suppression of pycnidial 

coverage was observed on maturing 

plants of Seri 82 in the field 

following co-inoculation at GS 37 

with a 1:1 isolate mixture of 

Table 1. Reduction in pycnidial coverage on seedlings of the wheat cultivars Shafir (SHF), Seri 

82 (SER), IAS 20, Bobwhite “S” (BOW) and Kavkaz/K4500 (KK), inoculated with 1:1 mixture of 

Septoria tritici. Data are percent reduction as compared to pycnidial coverage by the more 

virulent isolate in each case. 

Wheat cultivars 

Isolate mixture SHF SER IAS20 BOW KK 

ISR398 + ISR8036 52.2 98.7 - a - - 

ISR398 + ISR9812 38.3 78.0 - 99.5 99.7 

ISR398 + ISR9840 11.0 7.0 21.6 21.9 - 

ISR8036 + ISR9812 16.3 28.9 - - 71.8 

ISR8036 + ISR9840 26.7 24.3 33.8 27.4 - 

ISR9812 + ISR9840 26.1 24.3 32.8 63.4 100.0 

a Cultivar resistant to both isolates. 

39 

ISR398+ISR8036. The other five 

isolate mixtures on all wheat 

cultivar combinations are currently 

being tested in field trials. 

The identity of pycnidia 

developed on leaves of Seri 82 and 

Shafir, co-inoculated with 

ISR398+ISR8036, was verified using 

specific PCR primers. Isolate 

ISR8036 dominated (>70%) the 

pycnidial population on seedlings 

and from the onset of the epidemics 

in field plots of both Shafir and Seri 

82. The low fraction of ISR398 on 

the susceptible cultivar Shafir is 

explained by competition. In the 

mixture ISR398+ISR8036, isolate 

ISR8036 has a competitive 

advantage over ISR398, attributed 

to its higher aggressiveness. The 

same experimental approach will be 

adapted to the other isolate 

mixtures under investigation, once 

specific PCR primers are obtained 

for ISR9812 and ISR9840. 

The structure of natural 

populations of this pathogen is 

determined by both cultivar-isolate 

interactions and isolate-isolate 

interactions. 

References 

Halperin, T., Schuster, S., Pnini-Cohen, 

S., Zilberstein, A., and Eyal, Z. 1996. 

The suppression of pycnidial 

production on wheat seedlings 

following sequential inoculation by 

isolates of Septoria tritici. 

Phytopathology 86:728-732.

Session 2: The Infection Process 

Stagonospora and Septoria Pathogens of Cereals: The 

Infection Process 

B.M. Cunfer 

Department of Plant Pathology, University of Georgia, Griffin, GA 

Abstract 

Definitive information on the infection process has been reported for Stagonospora nodorum, Septoria tritici, and 

Septoria passerinii. Like other necrotrophic pathogens, they do not elicit the hypersensitive reaction. A significant difference 

in the infection process between Septoria and Stagonospora pathogens is that spore germination and penetration proceed 

much faster for S. nodorum than for S. tritici and S. passerinii. The Septoria pathogens penetrate the leaf primarily 

through stomata, whereas S. nodorum penetrates both directly and through stomata. Stagonospora nodorum kills the 

epidermal cells quickly, but S. tritici and S. passerinii do not kill epidermal cells until hyphae have ramified through the leaf 

mesophyll and rapid necrosis begins. Resistance slows host colonization but has no appreciable effect on the process of lesion 

development. The mechanisms controlling host response are still unclear. The infection process for ascospores is probably very 

similar to that for pycnidiospores. Ascospores of Phaeosphaeria nodorum germinate over a wide range of temperatures and 

their germ tubes penetrate the leaf directly. However, unlike pycnidiospores, the ascospores do not germinate in free water. 

The infection process has been 

studied most intensely for 

Stagonospora nodorum and Septoria 

tritici. One in-depth study on 

Septoria passerinii is available. 

Nearly all of the information 

reported is for infection by 

pycnidiospores. However, the 

infection process for other spore 

forms is quite similar. The 

information presented is mostly for 

infection of leaves under optimum 

conditions. Some studies were 

done with intact seedling plants, 

whereas others were conducted 

with detached leaves. Infection of 

the wheat coleoptile and seedling 

by S. nodorum was described in 

detail by Baker (1971) and 

reviewed by Cunfer (1983). 

Although no precise comparisons 

have been made, it appears that the 

infection process has many 

similarities in each host-parasite 

system and is typical of many 

necrotrophic pathogens. 

Information on factors influencing 

symptom development and disease 

expression are excluded but have 

been reviewed by other authors 

(Eyal et al., 1987; King et al., 1983; 

Shipton et al., 1971). A summary of 

factors affecting spore longevity on 

the leaf surface is included. 

Role of the Cirrus and 

Spore Survival on the 

Leaf Surface 

The most detailed information 

on the function of the cirrus 

encasing the pycnidiospores exuded 

from the pycnidium is for S. 

nodorum. The cirrus is a gel 

composed of proteinatous and 

saccharide compounds. Its 

composition and function are 

similar to that of other fungi in the 

Sphaeropsidales (Fournet, 1969; 

Fournet et al., 1970; Griffiths and 

Peverett, 1980). 

41 

The primary roles of cirrus 

components are protection of 

pycnidiospores from dessication 

and prevention of premature 

germination. The cirrus protects the 

pycnidiospores so that some 

remain viable at least 28 days 

(Fournet, 1969). When the cirrus 

was diluted with water, if the 

concentration of cirrus solution was 

>20%, less that 10% of 

pycnidiospores germinated. At a 

lower concentration, the 

components provide nutrients that 

stimulate spore germination and 

elongation of germ tubes. Germ 

tube length increased up to 15% 

cirrus concentration, then declined 

moderately at higher 

concentrations (Harrower, 1976). 

Brennan et al. (1986) reported 

greater germination in dilute cirrus 

fluid. Cirrus components reduced 

germination at 10-60% relative 

humidity. Once spores are

42 

Session 2 — B.M. Cunfer 

dispersed, the stimulatory effects of 

the cirrus fluid are probably 

negligible (Griffiths and Peverett, 

1980). At 35-45% relative humidity, 

spores of S. tritici in cirri remained 

viable at least 60 days (Gough and 

Lee, 1985). The cirrus components 

may act as an inhibitor of spore 

germination, or the high osmotic 

potential of the cirrus may prevent 

germination. 

Pycnidiospores of S. nodorum 

did not survive for 24 hours at 

relative humidity above 80% at 20 

C. Spores survived two weeks or 

more at

Stagonospora nodorum releases a 

wide range of cell wall degrading 

enzymes including amylase, pectin 

methyl esterase, 

polygalacturonases, xylanases, and 

cellulase in vitro and during 

infection of wheat leaves (Baker, 

1969; Lehtinen, 1993; Magro, 1984). 

The information related to cell wall 

degradation by enzymes agrees 

with histological observations. 

These enzymes may act in 

conjunction with toxins. Enzyme 

sensitivity may be related to 

resistance and rate of fungal 

colonization (Magro, 1984). 

Like many necrotrophs, 

Septoria and Stagonospora 

pathogens produce phytotoxic 

compounds in vitro. Cell 

deterioration and death in advance 

of hyphal growth into mesophyll 

tissue (Bird and Ride, 1981) is 

consistent with toxin production. 

However, a definitive role for 

toxins in the infection process and 

their relation to host resistance has 

not been established (Bethenod et 

al, 1982; Bousquet et al, 1980; Essad 

and Bousquet, 1981; King et al, 

1983). Differences in host range 

between wheat and barleyadapted 

strains of S. nodorum may 

be related to toxin production 

(Bousquet and Kollmann, 1998). 

Initiation of spore germination 

and percentage of spores 

germinated are not influenced by 

host susceptibility (Bird and Ride, 

1981; Morgan 1974; Straley, 1979; 

Straley and Scharen, 1979; Baker 

and Smith, 1978). Bird and Ride 

(1981) reported that extension of 

germ tubes on the leaf surface was 

slower on resistant than on 

susceptible cultivars. This 

mechanism, expressed at least 48 

hours after spore deposition, 

indicates pre-penetration resistance 

to elongation of germ tubes. There 

were fewer successful penetrations 

in resistant cultivars, and 

penetration proceeded more slowly 

on resistant cultivars (Baker and 

Smith, 1978; Bird and Ride, 1981). 

Lignification was proposed to 

limit infection in both resistant and 

susceptible cultivars, but other 

factors slowed fungal development 

in resistant lines. In susceptible 

lines, faster growing hyphae may 

escape lignification of host cells. 

Four days after inoculation of 

barley with a wheat biotype isolate 

of S. nodorum, hyphae grew through 

the cuticle and sometimes in outer 

cellulose layers of epidermal cell 

walls. Thick papillae were 

deposited beneath the penetration 

hyphae and the cells were not 

penetrated (Keon and Hargreaves, 

1984). 

Infection by Septoria 

tritici 

Pycnidiospores of S. tritici 

germinate in free water from both 

ends of the spore or from 

intercalary cells (Weber, 1922). 

Spore germination does not begin 

until about 12 hours after contact 

with the leaf. Germ tubes grow 

randomly over the leaf surface. 

Weber (1922) observed only direct 

penetration between epidermal 

cells, but others concluded that 

penetration through both open and 

closed stomata is the primary 

means of host penetration 

(Benedict, 1971; Cohen and Eyal, 

1993; Hilu and Bever, 1957). Kema 

Stagonospora and Septoria Pathogens of Cereals: The Infection Process 43 

et al. (1996) observed only stomatal 

penetration. Hyphae growing 

through stomata become 

constricted to about 1 µm diameter, 

then become wider after reaching 

the substomatal cavity. 

Hyphae grow parallel to the 

leaf surface under epidermal cells, 

then through the mesophyll to cells 

of lower the epidermis, but not into 

the epidermis. No haustoria are 

formed and hyphal growth is 

limited by sclerenchyma cells 

around the vascular bundles, 

except when hyphae are very 

dense. Vascular bundles are not 

invaded. Hyphae grow 

intercellularly along cell walls 

through the mesophyll, branching 

at a septum or middle of a cell. No 

macroscopic symptoms appear for 

about 9 days except for an 

occasional dead cell, but mesophyll 

cells die rapidly after 11 days. 

Pycnidia develop in substomatal 

chambers. Hyphae seldom grow 

into host cells (Hilu and Bever, 

1957; Kema et al, 1996; 

Weber, 1922). 

Successful infection only occurs 

after at least 20 hours of high 

humidity. Only a few brown flecks 

developed if leaves remained wet 

for 5-10 hours after spore 

deposition (Holmes and Colhoun, 

1974) or up to 24 hours (Kema et 

al., 1996). Host-parasite relations 

are the same on resistant or 

susceptible wheats. Spore 

germination on the leaf surface is 

the same regardless of 

susceptibility. The number of 

successful penetrations is about the 

same, but hyphal growth is faster 

in susceptible cultivars, resulting in 

more lesions. Hyphae extend

44 

Session 2 — B.M. Cunfer 

beyond the necrotic area in all 

cultivars. A toxin may play a role in 

pathogenesis (Cohen and Eyal, 

1993; Hilu and Bever, 1957). In 

contrast, colonization was greatly 

reduced on a resistant line (Kema et 

al., 1996). 

Infection by Septoria 

passerinii 

Green and Dickson (1957) 

present a detailed description of 

the infection process of S. passerinii 

on barley. The infection process is 

similar to S. tritici. Like S. tritici, the 

length of time required for leaf 

penetration is considerably longer 

than for S. nodorum. 

Germ tubes branch and grow 

over the leaf surface at random, but 

sometimes along depressions 

between epidermal cells. Leaf 

penetration is almost exclusively 

through stomata. Germination 

hyphae become swollen, and if 

penetration is unsuccessful, hyphae 

continue to elongate. No 

penetration occurs 48 hours after 

spore deposition. After 72 hours, 

germ tubes thicken over stomata, 

grow between guard cells and on 

surfaces of accessary cells and into 

the substomatal cavities. Direct 

penetration between epidermal 

cells is seen only rarely. 

Spore germination and host 

penetration are the same on 

resistant and susceptible cultivars. 

There is much less extension of 

hyphae within leaves on resistant 

cultivars and papillae are observed 

on many but not all cell walls. 

Hyphae grow beneath the 

epidermis from one stoma to 

another, but do not penetrate 

between epidermal cells. The 

mesophyll is colonized, but no 

haustoria form. After the 

mesophyll cells become necrotic, 

epidermal cells collapse. Mycelial 

development in the leaf is sparse 

and usually blocked by vascular 

bundles. In younger leaves, if the 

vascular sheath is less developed, 

hyphae pass between the bundle 

and the epidermis. Pycnidia form 

in substomatal cavities, mostly on 

the upper leaf surface (Green and 

Dickson, 1957). 

Factors Affecting Spore 

Longevity on the Leaf 

Surface 

Among the Stagonospora and 

Septoria pathogens of cereals, 

definitive information on the 

infection process has been reported 

only for S. nodorum, S. tritici, and S. 

passerinii. Like many other 

necrotrophic pathogens, neither 

group of pathogens elicit the 

hypersensitive reaction. A 

significant difference in the 

infection process between Septoria 

and Stagonospora pathogens is that 

spore germination and penetration 

proceeds much faster for S. 

nodorum than for S. tritici and S. 

passerinii. This has a significant 

influence on disease epidemiology. 

The Septoria pathogens penetrate 

the plant primarily through 

stomata, whereas S. nodorum 

penetrates both directly and 

through stomata. S. nodorum 

penetrates and kills the epidermal 

cells quickly, but S. tritici and S. 

passerinii do not kill epidermal cells 

until hyphae have ramified 

through the leaf mesophyll and 

rapid necrosis begins. 

Histological studies of fungal 

growth following host penetration 

match the data generated from 

epidemiological studies of host 

resistance. Resistance slows the rate 

of host colonization but has no 

appreciable effect on the process of 

lesion development. The 

mechanisms controlling host 

response, whether related to 

enzymes and toxins or other 

metabolites released by the 

pathogens during infection, are still 

unclear. 

There is little information about 

infection by ascospores. The 

infection process is probably very 

similar to that for pycnidiospores. 

Ascospores of Phaeosphaeria nodorum 

germinate over a wide range of 

temperatures, and their germ tubes 

penetrate the leaf directly. However, 

according to Rapilly et al. (1973), 

ascospores, unlike pycnidiospores, 

do not germinate in free water. 

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Benedict, W.G. 1971. Differential effect 

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wheat. Trans. Brit. Mycol. Soc. 

86:381-385. 

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Lacazedieux, J. 1973. Études sur 

l’inoculum de Septoria nodorum 

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Royle, D.J., and Ayres, P.G. 1995. 

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tritici and S. nodorum to UV-B 

irradiation in vitro. Mycol. Res. 

99:1371-1377. 

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A.A., and Shearer, B.L. 1971. The 

common Septoria diseases of 

wheat. Bot. Rev. 37:231-262. 

Straley, M. L. 1979. Pathogenesis of 

Septoria nodorum (Berk.) Berk. On 

wheat cultivars varying in 

resistance to glume blotch. Ph. D. 

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99 pp. 

Straley, M.L., and Scharen, A.L. 1979. 

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585.

46 

Aggressiveness of Phaeosphaeria nodorum Isolates and 

Their In Vitro Secretion of Cell-Wall-Degrading Enzymes 

P. Halama, a F. Lalaoui, a V. Dumortier, a and B. Paul b 

a Institut Supérieur d’Agriculture, Université Catholique de Lille, Lille, France 

b Laboratoire des Sciences de la Vigne, Institut Jules Guyot, Université de Bourgogne, Dijon, France 

Abstract 

The relationship between the in vitro production of cell-wall-degrading enzymes and the aggressiveness of three 

Phaeosphaeria nodorum isolates was studied. When grown in liquid medium containing 1% cell wall from wheat leaves as 

the only carbon source, the isolates secreted xylanase, α-arabinosidase, β-xylosidase, polygalacturonase, β-galactosidase, 

cellulase, β-1.3-glucanase, β-glucosidase, acetyl-esterase, and butyrate-esterase. Time course experiments showed different 

levels of enzyme production and different kinetics between isolates. Xylanase, cellulase, polygalacturonase, and butyrateesterase 

were positively correlated with isolate aggressiveness. The most aggressive isolate produced a higher proportion of 

xylanase than the other two isolates, suggesting the role of this enzyme in the pathogenesis of P. nodorum. 

Studies have revealed that 

Phaeosphaeria nodorum populations 

have significant variability in 

pathogenicity that has been 

measured by the ability of isolates 

to cause symptoms on wheat 

(Griffith and Ao, 1980; Allinghan 

and Jackson, 1981;Yang and 

Hughes, 1986; Krupinsky, 1997). 

As other plant-pathogenic 

fungi, P. nodorum produces a range 

of cell-wall-degrading enzymes 

(CWDE) that enables it to penetrate 

and infect host tissues (Lehtinen, 

1993; Magro, 1984). Very little is 

known about the variability of 

enzyme production in P. nodorum 

populations; there is, however, a 

need to assess the diversity of these 

wall-degrading enzymes and, in 

particular, the extent to which this 

diversity could lead to differences 

in pathogenicity. 

The objective of this study was 

to compare enzymatic variation 

between two wild isolates and one 

mutant isolate of P. nodorum by 

examining CWDEs, and to 

establish the possible relationship 

between enzymes associated to 

pathogenesis and the 

aggressiveness of fungal strains. 


Fungal strains 

Two wild strains (A/5 and 6/T) 

that differed significantly in their 

pathogenic behavior were isolated 

as described by Rapilly et al. (1992). 

The other isolate (300.2) is a 

carbendazim (MBC) resistant strain 

that was obtained using the 

protocol described in a previous 

study (Halama et al., 1999). 

Growth conditions and 

preparation of fungal 

extracts 

The pycniospores used for 

inoculation were produced on 

synthetic (S) medium (Halama and 

Lacoste, 1992). For enzyme 

production, isolates of S. nodorum 

were grown in liquid medium 

(Lehtinen, 1993) in which sucrose 

was replaced by 1% wheat cell 

walls. Wheat cell wall material was 

taken from 1-week-old seedlings of 

cv. ‘Soissons’ and prepared 

according to Lehtinen’s modified 

procedure (Lehtinen, 1993). After 

incubating cultures at 24°C under 

constant shaking (72 rpm), liquid 

filtrates were centrifuged at 8000 g 

for 15 min at 4°C. Supernatants were 

used for enzyme activity assays, and 

each culture experiment was 

replicated three times. 

Enzyme assays 

Cell-wall-degrading enzymes of 

P. nodorum were assayed from the 

crude culture filtrates using 

different methods. The 

dinitrosalicylic acid (DNS) modified 

method, described by Miller (1959) 

for determining the reducing group, 

was used for the endo-enzyme 

assay. Xylanase, endopolygalacturonase, 

cellulase, and β- 

1.3-glucanase activities were 

measured respectively on oat spelts 

xylan, galacturonic acid, 

carboxymethyl cellulose, and 

laminarin used as substrates. 

Absorbances were measured at 540 

nm. The reference sugar was 

glucose. 

Glycosidase activities were 

measured using p-nitrophenyl 

glycoside as a substrate (Poutanen, 

1988). β-glucosidase, β-

galactosidase, β-xylosidase, and αarabinosidase 

activities were 

assayed using p-nitrophenyl-β-Dglucopyranoside, 

p-nitrophenyl-β- 

D-galactopyranoside, pnitrophenyl-β-D-xylopyranoside, 

and p-nitrophenyl-α-Larabinopyranoside, 

respectively, as 

substrates. 

Esterase acetate activity was 

tested as described by Biely et al. 

(1988) using p-nitrophenylacetate. 

Degradation of pnitrophenylbutyrate 

was measured 

using p-nitrophenylbutyrate 

according to the procedure of 

Kolattukudy et al. (1981). In each 

case, p-nitrophenol was used for 

the standard microtitre plate. For 

all enzyme assays, one unit of 

enzyme was defined as the amount 

of enzyme that hydrolyzed 1 mmol 

of appropriate substrate, and each 

activity was expressed in mU.ml -1 . 

Pathogenicity test 

Isolates were tested for their 

relative pathogenicity on detached 

seedling leaves of the cultivar 

‘Soissons’ as previously described 

by Halama et al. (1999). 

Statistical analysis 

The analysis of variance was 

performed with the aid of the 

STAT-ITCF statistical software. 

Differences between the isolates 

were assessed using the Newman- 

Keuls test. Correlations between 

data for aggressiveness rates and 

for enzyme secretion were 

examined. 

Results 

The maximum secretions of 

CWDEs are presented in Table 1, 

which shows that P. nodorum 

isolates were able to produce a 

wide range of enzymes on 

Aggressiveness of Phaeosphaeria nodorum Isolates and Their In Vitro Secretion of Cell-Wall-Degrading Enzymes 47 

synthetic medium supplemented 

with isolated cell wall. The secreted 

enzymes were determined every 

second day over the growth period 

(14 days). 

Time course for production 

of CWDEs 

The A/5 isolate produced, in 

order of decreasing activity, 

xylanase, butyrate-esterase, βglucosidase, 

β-1.3-glucanase, 

acetyl-esterase, cellulase, 

polygalacturonase, β-galactosidase, 

and β-xylosidase (Table 1). Culture 

filtrates of the A/5 isolate had 

significantly higher levels of 

xylanase, butyrate-esterase, 

cellulase, and polygalacturonase 

activities than those of 6/T and 

300.2 isolates. Levels of enzyme 

activity between 6/T and 300.2 

isolates were significantly different 

mainly for two peaks of β-1.3glucanase 

and acetyl-esterase 

activity on days 10 and 14 

produced respectively by the 6/T 

and the 300.2 isolates. Xylanase 

activity by the A/5 isolate on day 

10 was approximately seven times 

higher (1574 mU.m1 -1 ) than that of 

the two other isolates. 

No α-arabinosidase activity 

could be detected in the 

filtrate of A/5 isolate, 

and very low levels were 

detected for 6/T and 

300.2 isolates. Very low 

β-xylosidase activity was 

detected both by A/5 

and 6/T isolates. 

The polygalacturonase activities 

were highest on day 6 for A/5 

isolate (56 mU.ml –1 ), after which 

the activity decreased. For 6/T and 

300.2 isolates, the highest activities 

were 27 and 12 mU.ml -1 

respectively, showing differences in 

their kinetics. As early as the 

second day, isolate 6/T produced a 

large amount of polygalacturonase, 

although isolate 300.2 secreted 

maximum polygalacturonase only 

after 12 days. 

β-1.3-glucanase assay was 

detected mainly for A/5 and 6/T 

isolates. β-glucosidase activity was 

produced by the three isolates with 

maximum activity on day 14 for the 

A/5 and 300.2 isolates and on day 

10 for the 6/T isolate. However, A/ 

5 and 300.2 isolates may not have 

reached their peaks of βglucosidase 

activity at the end of 

the time course. 

Where detected, the cellulase 

activity secreted by P. nodorum 

occurred transiently, and the 

highest activity took place during 

the early stages of fungal culture 

for A/5 isolate. The butyrateesterase 

activity was observed for 

the three isolates with a maximum 

Table 1. Maximum enzyme activity expressed by three 

isolates of Phaeosphaeria nodorum (A/5, 6/T, and 300.2) on 

medium supplemented with wheat cell walls. 

Isolate 

Enzyme A/5 6/T 300.2 

Xylanase 1574 1 (10) 2 213 (6) 200 (14) 

α-arabinosidase 0 5 (8) 7 (14) 

β-xylosidase 6 (10) 16 (14) 8 (14) 

Polygalacturonase 56 (6) 27(2) 12 (12) 

β-galactosidase 17 (12) 21 (10) 20 (14) 

Cellulase 106 (6) 0 3.5 (10) 

β-1,3 – glucanase 145 (12) 165 (10) 12 (12) 

β-glucosidase 153 (14) 158 (10) 118 (14) 

Acetyl esterase 126 (10) 44 (6) 124 (14) 

Butyrate esterase 527 (10) 409 (6) 379 (14) 

1 Data are expressed as mU.ml –1 culture medium filtrate. 

2 Enzyme activity was measured on the day given in 

parentheses.

48 

Session 2 — P. Halama, F. Lalaoui, V. Dumortier, and B. Paul 

at day 10, 6 and 14 for A/5, 6/T 

and 300.2 isolate respectively. 

Acetyl-esterase and β-galactosidase 

activities were also detectable for 

all three isolates. 

Aggressiveness of P. 

nodorum isolates 

The pathogenicity test allowed 

us to distinguish two groups of 

isolates according to their 

aggressiveness (Table 2). Significant 

differences in the average of 

necrosis symptoms were conclusive 

for differentiating the A/5 isolate 

from isolates 6/T and 300.2. The 

A/5 isolate of P. nodorum produced 

longer lesions on detached leaves 

than did the other two isolates 6/T 

and 300.2. Furthermore, there was 

partial correlation between the 

incubation period and length of 

necrotic lesions; the longer lesion of 

A/5 was related to a short latent 

period, but the similar lengths of 

necrotic lesions caused by 6/T and 

300.2 were unrelated to their 

incubation periods. 

Discussion 

Results reported here constitute 

the first report on the relationship 

between aggressiveness and in vitro 

production of CWDEs by P. 

nodorum. Our study indicated that 

Table 2. Lesion length and incubation period 

on detached leaves of wheat (cv. ‘Soissons’) 

caused by isolates of Phaeosphaeria nodorum 

10 days after inoculation. 

Lesion Incubation 

length period 1 

Isolate (mm) (hours) 

A/5 9.78 a 2 43 

6/T 3.60 b 63 

300.2 3.53 b 41 

1 The incubation period was determined by 

measuring the period between inoculation and 

the moment when 50% of the detached leaves 

presented visible lesions. 

2 Within a column, means followed by different 

letters are significantly different according to t 

test (P

References 

Allighan, E.A., and Jackson, L.F. 1981. 

Variation in pathogenicity, 

virulence, and aggressiveness of 

Septoria nodorum in Florida. 


Biely, P., Mackenzie, C.R., Schneider, 

H. 1988. Acetylxylan esterase of 

Schizopyllum commune. Methods in 

Enzymology 160:700-707. 

Carder, J.H., Hignett, R.C., and 

Swinburne, T.R. 1987. Relationship 

between the virulence of hop 

isolates of Verticillium albo-atrum 

and their in vitro secretion of cellwall 

degrading enzymes. Physiol. 

Mol. Plant Pathol. 31:441-452. 

Chan, Y.H., and Sackston, W.E. 1972. 

Production of pectolytic and 

cellulotytic enzymes by virulent 

and avirulent isolates of Sclerotium 

bataticola during disease 

development in sunflowers. Can. J. 

Bot. 50:2449-2453. 

Cooper, R.M. 1977. Regulation of 

synthesis of cell-degrading 

enzymes of plant pathogens. In: 

Cell Wall Biochemistry Related to 

Specificity in Host-Plant Pathogen 

Interactions. Solheim, B. and Raa, 

J. (eds.), pp. 163-211. 

Universitetsforlaget, Oslo. 

Cooper, R.M., Longman D., 

Campdell, A., Henry, M., and Lees, 

P.E. 1988. Enzymic adaptation of 

cereal pathogens to the 

monocotyledonous primary wall. 

Physiol. Mol. Plant Pathol. 32:37- 

47. 

Aggressiveness of Phaeosphaeria nodorum Isolates and Their In Vitro Secretion of Cell-Wall-Degrading Enzymes 49 

Griffith, E., and Ao, H.C. 1980. 

Variation in Septoria nodorum. Ann. 

Appl. Biol. 94:294-296. 

Halama, P., and Lacoste, L. 1992. Etude 

des conditions optimales 

permettant la pycniogénèse de 

Phaeosphaeria (Leptosphaeria) 

nodorum, agent de la septoriose du 

blé. Agronomie 12:705-710. 

Halama, P., Skajennikoff, M., and 

Dehorter, B. 1999. Tredad analysis 

of mating type, mutations and 

aggressiveness in Phaeosphaeria 

nodorum. Mycol. Res. 1:43-49. 

Howel, H.E. 1975. Correlation of 

virulence with secretion in vitro of 

three wall-degrading enzymes in 

isolates of Sclerotium fructigena 

obtained after mutagen treatment. J. 

Gen. Microb. 90:32-40. 

Keon, J.P., Byrde, R.J.W., and Cooper, 

R.M. 1987. Some aspects of fungal 

enzymes that degrade plant cell 

walls. In: Fungal Infection of Plants. 

Pegg, G.F.and Ayres, P.G., (eds.), 

pp.133-157. Cambridge University 

Press. 

Kolattukudy, P.E., Purdy, R.E., and 

Maiti, I.B. 1981. Cutinases from 

fungi and pollen. Methods in 

Enzymology 71:652-664. 


of Stagnospora nodonum isolates 


northern great plains. Plant Dis. 

81:1027-1031. 

Lehtinen, U. 1993. Plant cell wall 

degrading enzymes of Septoria 

nodorum. Physiol. Mol. Plant Pathol. 

43:121-134. 

Magro, P. 1984. Production of 

polysaccharide-degrading 

enzymes by Septoria nodorum in 

culture and during pathogenesis. 

Plant Sc. Let. 37:63-68. 

Martinez, M.J., Alconada, T., Guillen, 

F., Vasquez, C., and Reyes, F. 1991. 

Pectic activities from Fusarium 

oxysporum f. sp. melonis: 

purification and characterization 

of an exopolygalacturonase. FEMS 

Microb. Lett. 81:145-150. 

Miller, G.L. 1959. Use of 

dinitrosalicylic acid reagent for 

determination of reducing sugar. 

Analytical Chemistry 31:426-428. 

Poutanen, K. 1988. Characterization 

of xylanolytic enzymes for 

potential applications. Technical 

Research Centre of Finland, 

Publication 47, pp. 1-59. 

Rapilly, F., Skajennikoff, M., Halama, 

P., and Touraud, G. 1992. La 

reproduction sexuée et 

l’aggressivité de Phaeosphaeria 

nodorum Hedj (Septoria nodorum 

Berk). Agronomie 12:639-649. 

Senna, L.A., and Goodwin P.H. 1996. 

Comparison of cell wall-degrading 

enzymes produced by highly and 

weakly virulent isolates of 

Leptosphaeria maculans in culture. 

Microbiol. Res. 151:401-406. 

Yang, R.C., and Hughes, G.R. 1986. 

Pathogenic variation among 

isolates of Septoria nodorum. Can. J. 

Plant Pathol. 8:356.

50 

Growth of Stagonospora nodorum Lesions 

A.M. Djurle (Poster) 

Department of Ecology and Crop Production Science/Plant Pathology, Swedish University of Agricultural 

Sciences, Uppsala, Sweden 

Disease severity is often 

expressed as a percentage or 

proportion of leaf area showing 

symptoms. Increase in disease 

severity of stagonospora nodorum 

glume blotch is caused by either an 

increase in the number of lesions as 

a result of new infection or by 

expansion of existing lesions. While 

new infections are still in the 

incubation period, existing lesions 

have time to expand considerably 

(Lannou et al., 1994). Berger et al. 

(1997) suggested that lesion 

expansion should become the sixth 

component in describing polycyclic 

epidemics, and should be added to 

the already existing “epidemic 

quintet.” Lesion expansion has, for 

a long time, been considered as one 

of the most important factors for 

stagonospora nodorum disease 

increase (Rapilly et al., 1977; 

Rapilly et al., 1982). 


In a field experiment with 

winter wheat inoculated with 

Stagonospora nodorum, length and 

width of glume blotch lesions were 

measured repeatedly on the three 

uppermost leaves of tagged plants. 

The area of lesions was calculated 

assuming that they had an 

ellipsoidal shape. Lesion growth 

rates were analyzed in relation to 

current weather, lesion size, when a 

lesion was formed (first observed), 

and lesion age. 


The results show that lesions 

followed a pattern of exponential 

growth and thus the rates were not 

constant over time. Among 

weather factors, mean temperature 

was the only factor that had a small 

effect on lesion growth rate, aside 

from the actual size of the lesions. 

Lesions that were formed (first 

observed) before or at heading 

(DC

Session 3A: Host-Parasite Interactions 

Genetic Control of Avirulence in Mycosphaerella 

graminicola (Anamorph Septoria tritici) 

G.H.J. Kema and E.C.P. Verstappen 

DLO-Research Institute for Plant Protection (IPO-DLO), Wageningen, The Netherlands 

Mycosphaerella graminicola is a 

plant pathogenic bipolar 

heterothallic ascomycete (Kema et 

al., 1996c) that causes septoria 

tritici leaf blotch of wheat. The 

disease is currently considered the 

major threat to European wheat 

crops. Our main interest is to 

understand the genetic control of 

specificity in mating and 

pathogenicity in this pathosystem. 

Therefore, we previously studied 

the histopathology of specific 

interactions and the genetic 

variation for virulence and 

resistance in pathogen isolates and 

host species and cultivars, 

respectively. We concluded that 

resistance to M. graminicola in the 

tested wheat cultivars is most 

probably not based on 

hypersensitivity (Kema et al., 

1996d). 

Like others we observed 

numerous host-pathogen 

interactions, which were confirmed 

in repeated field experiments (Eyal 

and Levy, 1987; Saadaoui, 1987; van 

Ginkel and Scharen, 1988; Ahmed 

et al., 1995; Kema et al., 1996a, b; 

Kema and van Silfhout, 1997). The 

next step was to understand the 

genetic control of these 

phenomena. Therefore, we had to 

determine the mating system of M. 

graminicola and find a way to cross 

particular isolates of the fungus, 

which eventually succeeded (Kema 

et al., 1996c). 

Since then, our group continues 

to study genome plasticity in M. 

graminicola and is exploring the 

possibility of dissecting the genetic 

factors that control the interaction 

between host and pathogen, as well 

as mating between pathogen 

strains (Kema et al., 1999). The 

current status and future prospects 

of this work will be discussed. 


Wheat cultivars. Cultivars Shafir, 

Veranopolis, and Kavkaz were 

used as differentials and cvs. 

Taichung 29 and Kavkaz/K4500 

were used as susceptible and 

resistant checks, respectively, in 

seedling experiments. In field 

experiments cvs. Vivant and 

Hereward and the breeding lines 

NSL92-5719, RU51A, and CH76337 

were used. 

Table 1. Responses of wheat cultivars to the parental Mycosphaerella graminicola strains 

IPO323 and IPO94269 in seedling and adult plant experiments conducted in growth rooms and in 

the field, respectively. a 

Seedling Adult plant 

Cultivars IPO323 IPO94269 IPO323 IPO94269 

Taichung 29 + + 

Kavkaz/K4500 - - 

Kavkaz - + 

Veranopolis - + 

Shafir - + - + 

Hereward - + 

Vivant - + 

NSL92-5719 - + 

RU51A +/- - 

CH76337 +/- - 

a Pycnidial coverage: +=susceptible, -=resistant. 

51 

Fungal isolates. Isolate IPO323 

[MAT1-1] and IPO94269 [MAT1-2] 

were crossed to generate an F1 

population. Individual F1 progeny 

isolates were 1) backcrossed to both 

parents for mating type 

identification and to generate BC1 

populations, and 2) intercrossed to 

generate F2 populations. The 

avirulence/virulence of these 

parental isolates to the 

aforementioned cultivars is shown 

in Table 1. 

Experiments. F1, BC1, and F2 

populations were tested at the 

seedling stage in growth rooms and 

repeated twice. Individual progeny 

isolates have been tested several 

times on the differential cultivars in 

the course of additional 

experiments. The F1 mapping 

population was also evaluated on 

differential wheat cultivars in the 

field. Each plot, with randomized

52 

Session 3A — G.H.J. Kema and E.C.P. Verstappen 

cultivars, was replicated twice and 

was inoculated with an individual 

F1 isolate. 


In the seedling experiments all 

progeny isolates were virulent on 

cv. Taichung. None of these isolates 

carried virulence for cv. Kavkaz/ 

K4500, indicating that the parental 

isolates carry the same avirulence 

factor(s) for this cultivar. 

Avirulence for each of the 

differentiating cultivars is inherited 

as a single gene. However, these 

avirulences co-segregated. Thus the 

entire F1, BC1, and F2 progenies 

showed the parental types. This 

suggests that the avirulences for 

these cultivars are tightly linked. 

There are two reasons for this 

hypothesis: 1) additional data 

indicate that cvs. Shafir, 

Veranopolis, and Kavkaz carry 

different resistance factors (Kema et 

al., 1996a, b) and 2) identification of 

recombinant F1 progeny isolates in 

another cross 

(USDA50*IPO323.69.1) with 

avirulence for either Kavkaz or 

Veranopolis (unpublished data). 

Still, two alternative hypotheses 

cannot be excluded: 1) IPO323 

carries an avirulence factor for a 

common resistance factor in the 

tested differentials or 2) an 

avirulence gene product from 

IPO323 is recognized by different 

resistance factors in these cultivars. 

In order to investigate whether 

the avirulence in IPO323 for other 

wheat cultivars (Table 1) would 

segregate independently from the 

identified locus, a field experiment 

was conducted. Again, avirulence 

for the individual cultivars was 

controlled by a single locus. The 

avirulences for cvs. Vivant, 

Hereward, NSL92-5719, and Shafir 

co-segregated, indicating that they 

map to the same position as the 

locus identified in the seedling 

experiments. However, in addition 

to that, the avirulences for the 

breeding lines RU51A and CH76337 

inherited independently from that 

locus. Hence, recombinant progeny 

isolates were identified that were 

entirely virulent or avirulent on all 

cultivars. 

Hence, we hypothesize the 

presence of a complex major effect 

locus of tightly linked avirulence 

genes in M. graminicola IPO323 and 

two additional independent loci 

carrying minor effect avirulence 

factors in IPO94269. The former 

locus was mapped on the M. 

graminicola genome and is currently 

being isolated following map-based 

cloning strategies. 


We thank Jos Koeken, Suzanne 

Verhaegh, and the IPO-DLO 

technical and experimental farm 

staff for contributing to the 

presented data. Stimulating 

discussions with the “Wageningen” 

Mycosphaerella group, the “John 

Innes” Mycosphaerella group, and 

the EU-SIS consortium are kindly 

acknowledged. Part of this project is 

funded by EU-BIOTECH PL096-352. 

References 

Ahmed, H.U., Mundt, C.C., and 

Coakley, S.M. 1995. Host-pathogen 

relationship of geographically 

diverse isolates of Septoria tritici 

and wheat cultivars. Plant 

Pathology 44:838-847. 

Eyal, Z., and Levy, E. 1987. Variations 

in pathogenicity patterns of 

Mycosphaerella graminicola within 

Triticum spp. in Israel. Euphytica 

36:237-250. 

Kema, G.H.J., Annone, J.G., Sayoud, 

R., van Silfhout, C.H., van Ginkel, 

M., and De Bree, J. 1996a. Genetic 




pathosystem. I. Interactions 

between pathogen isolates and 

host cultivars. Phytopathology 

86:200-212. 


J.G., and van Silfhout, C.H. 1996b. 




pathosystem. II. Analysis of 

interactions between pathogen 



Kema, G.H.J., and van Silfhout, C.H. 

1997. Genetic variation for 

virulence and resistance in the 


pathosystem III. Comparative 

seedling and adult plant 

experiments. Phytopathology 

87:266-272. 

Kema, G.H.J., Verstappen, E.C.P., 

Todorova, M., and Waalwijk, C. 

1996c. Successful crosses and 

molecular tetrad and progeny 

analyses demonstrate 

heterothallism in Mycosphaerella 

graminicola. Current Genetics 

30:251-258. 


Waalwijk, C., Bonants, P.J.M., De 

Koning, J.R.A., Hagenaar de 

Weerdt, M., Hamza, S., Koeken, 

J.G.P., and van der Lee, Th.A.J. 

1999. Genetics of biological and 

molecular markers in 

Mycosphaerella graminicola, the 

cause of septoria tritici leaf blotch 

of wheat. In Lucas, J.A., Bowyer, P., 

and Anderson, H.M. (eds.). 

Septoria on cereals: a study of 

pathosystems. CABI Publishing, 

New York, NY, USA, pp. 161-180. 

Kema, G.H.J., Yu, D.Z., Rijkenberg, 


R.P. 1996d. Histology of the 




Saadaoui, E.M. 1987. Physiologic 



van Ginkel, M., and Scharen, A.L. 

1988. Host-pathogen relationships 

of wheat and Septoria tritici. 


Cytogenetics of Resistance of Wheat to Septoria Tritici 

Leaf Blotch 

L.S. Arraiano, A.J. Worland, and J.K.M. Brown 

Cereals Research Department, John Innes Centre, Norwich, UK 

The John Innes Centre holds the 

world’s most comprehensive 

collection of precise genetic stocks 

of wheat. Elements of this 

collection, including intervarietal 

substitution and alien addition 

lines, are ideal for detecting 

chromosomes carrying 

agronomically important genes. 

These lines are being used in 

research on the genetics of 

resistance to septoria tritici leaf 

blotch caused by Mycosphaerella 

graminicola (anamorph Septoria 

tritici). 

A synthetic hexaploid wheat 

(Synthetic) was developed from a 

cross between Triticum dicoccoides 

(AABB) and Aegilops squarrosa (DD) 

(Sears, 1976). Synthetic carries 

genes for resistance to Stagonospora 

nodorum (Nicholson et al., 1993), 

and a complete set of substitution 

lines of Synthetic chromosomes 

into a susceptible wheat variety, 

Chinese Spring (CS), has been 

developed (Worland et al., 1996). 

To study resistance to M. 

graminicola, a detached seedling 

leaf technique (Arraiano et al., 

1999) was used to test both Chinese 

Spring and Synthetic. Individual 

Dutch and Portuguese M. 

graminicola isolates supplied by 

IPO-DLO (Netherlands) were 

tested. Synthetic was completely 

resistant to all isolates, except for 

IPO92006, whereas Chinese Spring 

was susceptible to all isolates 

except IPO323, to which it was 

moderately resistant. The results 

for Chinese Spring are consistent 

with field trial data (Brown et al., 

1999). Baldus and Longbow, the 

susceptible controls, were very 

susceptible to all isolates. 

Based on these results, CS 

(Synthetic) substitution lines were 

tested using the detached leaf 

technique. Leaves were inoculated 

with the Dutch isolates IPO323 and 

IPO94269, to identify the Synthetic 

chromosomes that carry genes for 

resistance to M. graminicola. The 

line carrying chromosome 7D (i.e., 

CS background with the 7D 

chromosome substituted by that of 

Synthetic) showed complete 

resistance to both isolates. Onehundred 

7D single-chromosome 

recombinant lines are now being 

tested to locate Synthetic’s 

resistance gene more precisely in 

relation to microsatellite and RFLP 

markers. 

Bezostaya 1 has been identified 

as a source of resistance to septoria 

tritici leaf blotch (Danon et al., 

1982), and field trials showed it to 

be specifically resistant to IPO323 

(Brown et al., 1999). Substitution 

lines of Bezostaya 1 into Dwarf A, a 

susceptible line, were tested as 

adult plants, and chromosome 3A 

was identified as carrying genes for 

resistance to IPO323. 

Acknowledgment 

This research was supported by 

PRAXIS XXI – Fundação para a 

Ciência e a Tecnologia, Portugal, 

and the Ministry of Agriculture, 

Fisheries and Food, UK. 

References 

53 

Arraiano, L.S., P.A. Brading, and 

J.K.M. Brown. 1999. A detached 

seedling leaf technique to screen 

for resistance to Mycosphaerella 

graminicola in field trials. In 

preparation. 

Brown, J.K.M., G.H.J. Kema, E.C.P. 

Verstappen, H.R. Forrer, L.S. 

Arraiano, P.A. Brading, E.M. 

Foster, A. Hecker, and E. Jenny. 

1999. Resistance to septoria tritici 

leaf blotch caused by isolates of 


(anamorph Septoria tritici) in wheat 

varieties. In preparation. 

Danon, T., J.M. Sacks, and Z. Eyal. 

1982. The relationship among 

plant stature, maturity class and 

susceptibility to Septoria leaf 

blotch of wheat. Phytopathology 

72:1037-1042. 

Nicholson, P., H.N. Rezanoor, and A.J. 

Worland. 1993. Chromosomal 

location of resistance to Septoria 

nodorum in a synthetic hexaploid 

wheat determined by the study of 

chromosomal substitution lines in 

‘Chinese Spring’ wheat. Plant 

Breeding 110:177-184. 

Sears, E.R. 1976. A synthetic 

hexaploid wheat with fragile 

rachis. Wheat Information Service 

41:31-32. 

Worland, A.J., S. Lewis, and C. 

Ellerbrook. 1996. Septoria 

resistance in wheat. In John Innes 

Centre and Sainsbury Laboratory 

Annual Report 1995/96. Norwich, 

UK. p. 46.

54 

A Possible Gene-for-Gene Relationship for Septoria Tritici 

Leaf Blotch Resistance in Wheat 

P.A. Brading, 1 G.H.J. Kema, 2 and J.K.M. Brown 1 

1 Cereals Research Department, John Innes Centre, Norwich, UK 

2 DLO-Research Institute for Plant Protection (IPO-DLO), Wageningen, The Netherlands 

Abstract 

In an F2 population of a cross between the resistant variety Flame and the susceptible variety Longbow it was shown that 

Flame carried one partially recessive gene for resistance to Septoria tritici isolate IPO323, as measured in a detached leaf 

assay. Work is underway to determine whether this resistance gene has a gene-for-gene relationship with the single avirulence 

locus identified in the IPO323 isolate. 

Septoria tritici leaf blotch, 

caused by the fungus 


(anamorph Septoria tritici), is one of 

the most serious foliar pathogens of 

wheat in Europe. In recent field 

trials using individual M. 

graminicola isolates, specific variety 

x isolate interactions have been 

observed (Kema and van Silfhout, 

1997). A number of wheat varieties 

show specific resistance to the 

Dutch isolate IPO323, including the 

British varieties Flame and 

Hereward (Brown et al., 1999). In 

Holland, crosses have been made 

between IPO323 and another 

isolate, IPO94269. Avirulence of 

IPO323 on three specifically 

resistant cultivars, Shafir, Kavkaz, 

and Veranopolis, appears to be 

controlled at a single locus with 

simple inheritance (Kema et al., 

1999). To investigate whether the 

specific resistances of Flame and 

Hereward to IPO323 conform to a 

gene-for-gene relationship and also 

whether Flame and Hereward 

share the same resistance gene, 

crosses between Flame, Hereward, 

and a susceptible variety, Longbow, 

have been made. 

Eighty F 2 seedlings from a cross 

between Flame and Longbow were 

tested in a detached leaf assay 

(Arraiano et al., 1999) in which 

primary and secondary leaves were 

inoculated with IPO323. Leaf 

sections were scored according to 

the percentage leaf area covered 

with lesions bearing pycnidia 15-28 

days after inoculation. Each F 2 

plant was represented by four leaf 

sections tested in separate boxes. 

The parental varieties, Flame and 

Longbow, were also included in 

each box. Comparison of infection 

levels on all four replicate leaf 

sections allowed individual plants 

to be rated as resistant, susceptible 

or intermediate. Flame was always 

resistant and Longbow always 

susceptible. Of the 80 progeny 

tested 23 were scored as resistant 

(less than 10% infection on all 

leaves). The other 57 progeny were 

scored as either susceptible (all leaf 

sections heavily infected) or 

intermediate (variable levels of 

infection). The 1:3 ratio of 

resistant:susceptible/intermediate 

is consistent with a single, partially 

recessive resistance gene in Flame. 

F 3 families generated from the 

80 F 2 individuals are being tested 

as seedlings (GS 25) in a polytunnel 

to test the prediction of a single 

gene for resistance to IPO323 in 

Flame. If this prediction is correct, 

F 3 families from resistant or 

susceptible F 2 individuals are 

expected to be uniformly resistant 

or susceptible, whereas 

intermediate F 2 individuals should 

produce F 3 families segregating 1:3 

for IPO 323 

resistance:susceptibility. 

To investigate whether 

Hereward carries the same IPO323 

resistance gene as Flame, F 2 

progeny of crosses between 

Hereward and Longbow and 

between Hereward and Flame will 

be tested as detached leaves. The 

Hereward x Longbow cross will 

determine whether Hereward’s 

resistance is controlled by a single 

gene. The Hereward x Flame cross 

will test for allelism. The results 

from both tests will be presented. 

As IPO323 avirulence is 

controlled at a single locus (Kema 

et al., 1999) and Flame’s resistance 

to this isolate may be due to a 

single gene, we hypothesize that a 

gene-for-gene relationship exists 

between Flame and IPO323. To 

confirm this hypothesis, we are 

testing 61 progeny isolates from the 

IPO323 x IPO94269 cross on Flame 

and Longbow as detached leaves.


This work was funded by the 

EU Framework 4 Biotechnology 

program and the Ministry of 

Agriculture Fisheries and Foods 

(MAFF). 

A Possible Gene-for-Gene Relationship for Septoria Tritici Leaf Blotch Resistance in Wheat 55 

References 

Arraiano, L.S., P.A. Brading, and 

J.K.M. Brown. 1999. A detached 

seedling leaf technique to screen 

for resistance to Mycosphaerella 

graminicola (anamorph Septoria 

tritici) in wheat varieties. In 

preparation. 

Brown, J.K.M., G.H.J. Kema, H.R. 

Forrer, E.C.P. Verstappen, L.S. 

Arraiano, P.A. Brading and E.M. 

Foster. 1999. Resistance of wheat 

varieties to septoria tritici leaf 

blotch caused by isolates of 

Mycosphaerella graminicola in field 

trials. In preparation. 

Kema, G.H.J., and C.H. Van Silfhout. 







87:266-272. 

Kema, G.H.J., E.C.P. Verstappen, C. 

Waalwijk, P.J.M. Bonants, J.R.A. de 

Koning, M. Hagenaar-de Weerdt, 

S. Hamza, J.G.P. Koeken, and T.A.J. 

van der Lee. 1999. Genetics of 

biological and molecular markers 

in Mycosphaerella graminicola, the 

cause of septoria tritici leaf blotch 

of wheat. In: In Septoria on cereals: 

a Study of Pathosystems. Lucas, 

J.A., P. Bowyer, and H.M. 

Anderson (eds.). CABI Publishing, 

New York, NY, USA. pp.161-180.

56 

Diallel Analysis of Septoria Tritici Blotch Resistance in 

Winter Wheat 

X. Zhang, 1 S.D. Haley, 2 and Y. Jin 1 * 

1 Plant Science Department, South Dakota State University, Brookings, SD, USA 

2 Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO, USA 

Abstract 

In the winter wheat area of the northern Great Plains, leaf spot complex has been problematic in the past decade. In years 

with high precipitation from late April to July, septoria tritici blotch (STB), caused by Septoria tritici, is most prevalent. As 

part of our effort to improve STB resistance, inheritance of STB resistance was investigated by an eight-parent full diallel 

scheme. Parents, F 1 , and reciprocal F 1 were planted on three different dates. Within each planting date, three to five seeds of 

each experimental unit were planted in the greenhouse. Materials were arranged in a randomized complete block design 

(RCBD) with three replicates. Plants at the second-leaf stage were inoculated with a bulk of six S. tritici isolates. Significant 

general combining ability (GCA), specific combining ability (SCA), and reciprocal effects were observed in the analysis of 

variance. The ratio of GCA sum of squares relative to SCA sum of squares suggested that GCA was more important than 

SCA. Additive effects played the major role in host response to STB, while non-additive effects were also detected. General 

combining ability effects of individual genotypes were in close agreement with parental performance. KS94U338, a genotype 

with resistance derived from Triticum tauschii, had the lowest STB score and the highest general combining ability. This 

result indicates that this genotype, possessing resistance distinct from other known sources, should prove useful in breeding 

efforts to improve STB resistance in wheat. 

Winter injury is the most 

adverse factor for winter wheat 

production in the northern Great 

Plains of the USA. Adoption of 

conservation tillage practices, with 

winter wheat planting into spring 

wheat stubble, has increased 

steadily over the past decade. 

While this practice improves winter 

survival, accumulation of wheat 

residue on the soil surface has 

promoted the development of leaf 

spot diseases in this region. Severe 

epidemics of leaf spot complex on 

winter wheat have occurred during 

the last decade. Septoria tritici 

blotch has been predominant in 

years with above average 

precipitation from late April to July. 

Improvement of STB resistance was 

intensified in our project beginning 

in 1995. As part of this effort, we 

initiated studies to investigate 

combining ability of STB resistance 

* First author prevented from attending 

workshop by unforeseen travel 

problems. 

in known resistant genotypes. A 

better understanding of resistance 

could lead to more efficient 

deployment of germplasm 

resources. 


Eight winter wheat genotypes 

(Table 1) were selected based on the 

level of resistance (field and 

greenhouse) and their diverse 

origins of resistance. A total of 64 

genotypes (parents, F 1 , and 

reciprocal F 1 ) were included in the 

test. The study consisted of three 

planting dates at three-day 

intervals. In each planting, three to 

five seeds of each experimental 

unit were planted in plastic 

conetainers filled with a peat-moss 

and perlite mixture. Each planting 

Table 1. Parental means, general combining ability (GCA), specific combining ability (SCA), and 

reciprocal effects of septoria tritici blotch scores on the second leaf in an eight-parent diallel. 

Resistant 

Moderately 

resistant Susceptible 

Parent 1 2 3 4 5 6 7 8 

1 KS94U338 —† 0.5 0.1 0.3 -1.9** 0.9** 0.6* -0.6* 

2 Jagger 0.8* — -0.5 -1.0** -2.0** 1.0** 1.1** 2.0** 

3 KS91W005-1-4 -0.9* -0.9* — -2.0* 1.6** 0.8** 1.0** 0.7* 

4 KS91W0935-29-1 1.3** -0.6 0.0 — 1.3** 0.4 0.5 -0.6* 

5 KS87822-2-1 0.3 0.1 -0.6 -0.5 — 0.1 0.3 0.5 

6 SD93493 -0.1 -0.4 -0.2 0.1 0.2 — -0.8* -1.3** 

7 Tandem -1.1* 0.3 0.2 -0.2 0.1 -0.2 — -0.9* 

8 SD93500 -1.2** -0.3 -0.1 -1.1** -0.2 -0.2 -0.1 — 

Parental means 1.4 1.4 1.9 5.8 5.8 8.0 8.3 8.7 

Parental GCA -2.2** -1.6** -1.1** -0.5** 0.0 1.8** 1.6** 1.8** 

*, ** Significantly different from zero at 0.05 and 0.01 probability levels, respectively. 

† SCA effects are above the diagonal line, and reciprocal effects are below.

consisted of three replicates 

arranged in a randomized complete 

block design (RCBD). 

Six isolates were used 

throughout this study. Fresh 

inoculum was prepared each time 

before inoculation. Conidia of each 

isolate were produced on acidic 

potato dextrose agar petri plates. 

The plates were incubated on a 

laboratory bench for 12 h under 

cool white fluorescent lights at 

room temperature. When the edge 

of pink colonies tended to darken, 

conidia were harvested by flooding 

the plates with doubled-distilled 

water and gently scraping the 

colonies with a rubber spatula 

attached to a glass rod. The conidial 

suspensions from the six isolates 

were combined, filtered through 

two layers of cheesecloth, and 

adjusted to approximately 5-10 x 

10 6 conidia ml -1 . 

Plants were inoculated when 

the second leaf was fully expanded. 

A volume of 100 ml of the conidial 

suspension was sprayed evenly 

onto 300 plants using an atomizer. 

Plants were maintained in a mist 

chamber for 96 h at 100% relative 

humidity and 21±1°C under a 12-h 

photoperiod. To avoid leaf 

senescence, the mist chamber was 

opened 30 min every 24 h while the 

plants were kept wet. Then the 

Table 2. Septoria tritici blotch reading scales used in this study. 

plants were incubated in a growth 

chamber with a 12-h photoperiod at 

21±1°C. 

Twenty-one days after 

inoculation, disease ratings of the 

second leaf were taken based on a 1 

to 9 scale (Table 2). The average 

disease scores of resistant 

genotypes (R) were 1.0 to 4.9; of 

moderate resistant genotypes (MR) 

from 5.0 to 6.9; of moderate 

susceptible genotypes (MS) from 

7.0 to 7.9; and of susceptible 

genotypes from 8.0 to 9.0. The data 

were analyzed with the “Diallel 

analysis and simulation” program 

designed by Burow and Coors 

(1994) according to Griffing’s 

Model 1 (fixed model), Method 1 

(Griffing, 1956). Because these 

experiments were conducted in one 

controlled environment, the 

genotype by environment 

interaction was theoretically 

negligible. Thus, sets (planting 

dates) were treated as replicates, 

and the mean value of the three 

observations within each set 

represented the estimated STB score 

of the replicate. 

A t-test was used to test 

whether the GCA, SCA, and 

reciprocal effects were significantly 

different from zero. The degrees of 

freedom for estimated GCA effects 

(g i ) were (p-1), where p = number 

Rating Symptom description 

1. No visible symptoms are observed, and the leaf remains green and healthy. 

2. A few chlorotic lesions are present, and the infection site is a tan-colored spot. 

3. Extensive chlorotic lesions are present. Lesions occasionally have necrosis at the infection 

sites. 

6. Extensive chlorotic lesions merge with each other, and individual lesions are identified by 

initial infection sites. Necrosis and chlorosis both exist on the leaf. 

7. Lesions fully merge, and more than half of the leaf is desiccated by necrosis. 

8. The entire leaf is desiccated, and water-soaked lesions occupy the entire leaf. 

9. A few pycnidia are visible on the infected sites, and less than 30% of the leaf is occupied by 

pycnidia covered lesions that remain dry and green. 

10. Pycnidia occupy 50 to 70% of the leaf, and infected sites are dry yet still green. 

11. The entire leaf is covered by pycnidial lesions, and the leaf is dry yet still green. 

Diallel Analysis of Septoria Tritici Blotch Resistance in Winter Wheat 57 

of parents. The degrees of freedom 

for estimated SCA effects (s ij ) and 

estimated reciprocal effects (r ij ) 

were p(p-1) (Kang, 1994). 


No significant differences 

between replicates (different 

planting dates) were detected (Table 

3). However, highly significant 

effects (P

58 

Session 3A — X. Zhang, S.D. Haley, and Y. Jin 

with resistance derived from T. 

tauschii, should prove useful in 

breeding efforts to improve STB 

resistance in wheat. The other two 

resistant genotypes, ‘Jagger’ and 

‘KS91W005-1-4’, had large, 

negative, highly significant GCA 

effects. Of the moderate resistant 

parents, ‘KS91W0935-29-1’ and 

‘KS87822-2-1’, only KS91W0935-29- 

1 had significant negative GCA 

effects. Each of the susceptible 

parents (‘SD93493’, ‘SD93500’, and 

‘Tandem’) had high GCA values. 

Specific combining ability 

effects were observed in 20 of the 28 

possible combinations, indicating 

that non-additive effects may exist 

for STB resistance. Reciprocal 

effects were present in five of the 

eight combinations involving 

KS94U338, crosses of KS91W005-1- 

4 with Jagger, and SD93500 with 

KS91W0935-29-1. When crossed 

with KS94U338 as female, the 

hybrids of KS91W005-1-4 and the 

two susceptible parents (SD93500 

and Tandem) had lower disease 

score than those of the reciprocal 

crosses (with reciprocal effects of - 

0.9, -1.1, and -1.2). Apparently 

KS91W005-1-4, Tandem, and 

SD93500 could contribute 

additional resistance when used as 

female. The maternal effects of 

SD93500 were also observed when 

it was crossed with KS91W0935-29- 

1. The maternal effects in 

combinations of KS94U338 with 

Jagger and KS94U338 with 

KS91W0935-29-1 are ascribed to 

KS94U338, due to the positive 

reciprocal effects between crosses 

of KS94U338 used as male and 

female. The existence of reciprocal 

effects in resistance to STB was also 

observed by Jlibene et al. (1994). 

With the observation of 

predominant GCA effects and 

reciprocal effects for enhanced 

resistance, improvement of STB 

resistance can be achieved by 

crossing two parents having good 

resistance, while selecting resistant 

progeny from particular crosses 

based on the direction of the 

crosses is also predictable. 


The authors gratefully 

acknowledge Drs. Rollin Sears, Joe 

Martin, and Stan Cox (Kansas State 

University, USDA-ARS) for 

providing some of the germplasm 

used in our studies. 

References 

Burow, M.D., and J.G. Coors. 1994. 

DIALLEL: A microcomputer 

program for the simulation and 

analysis of diallel crosses. Agron. J. 

86:154-159. 

Griffing, B. 1956. Concept of general 

and specific combining ability in 

relation to diallel crossing systems. 

Aust. J. Biol. Sci. 9:463-493. 

Jlibene, M., J.P. Gustafson, and S. 

Rajaram. 1994. Inheritance of 

resistance to Mycosphaerella 

graminicola in hexaploid wheat. 

Plant Breed. 112:301-310. 

Kang, M.S. 1994. Applied quantitative 

genetics. Kang M.S. Publisher, 

Baton Rouge, LA.

Analysis of the Septoria Monitoring Nursery 

L. Gilchrist, C. Velazquez, and J. Crossa 

CIMMYT Wheat Program, El Batan, Mexico 

Abstract 

The Septoria Monitoring Nursery (SMN) was divided into two sections: 1) the best sources of resistance identified by 

CIMMYT and national agricultural research breeding programs (renewed every three years) and 2) a tentative group of 

differentials. The nursery included two susceptible durum varieties and a resistant one, as well as two susceptible bread wheat 

varieties and a resistant one. Readings of septoria leaf blotch were taken using the double digit modified scale, and analyses 

were done separately by digits. The variance component estimate and the F test for the first and the second digits were highly 

significant for site, as well as for the site x genotype interaction component for the 1 st and 2 nd SMN. An analysis of the group 

of tentative differentials across the seven years and all sites also gave significant differences between sites and between sites 

and genotypes. The contrast between durum and bread wheat for the 1 st SMN was not significant, which indicates that at 

least at those locations there were no host-specific pathogen populations. The contrast between durum and bread wheat was 

significant in the 2 nd SMN, indicating the existence of specific pathogen populations for each of the two crops in some sites. 

The most resistant lines across sites for the 1 st SMN were Trap#1/Bow and #1959, of Chinese origin, and for the 2 nd 

SMN, Eg-AH567.71// 4*Eg-A/3/2*CMH79.243, Cal/NH/H567.71/3/2*Ning 7840/4/CMH83.2277/5/Bow/2*Ning 7840// 

CMH83.2277, and Sha5/Bow. A more detailed analysis of genotype x site interaction will be carried out to identify the 

differential response of some lines to the pathogen populations in different sites. 

The Septoria Monitoring 

Nursery was initiated in 1992 

(Gilchrist, 1994). Based on virulence 

studies on seedlings involving 

Septoria tritici isolates obtained from 

hot spot locations in many countries 

around the world, Kema et al. 

(1996; 1997) found significant 

interaction between pathogen 

isolates and host cultivars. The 

same authors also confirmed the 

specificity of the relationship 

between bread wheat genotypes 

and isolates taken from bread 

wheat, and between durum wheat 

genotypes and isolates collected 

from durum wheat, as 

demonstrated by Eyal et al. (1973), 

Saadaoui (1987), and van Ginkel 

and Scharen (1988). 

A better understanding of 

specificity in the Septoria-wheat 

pathosystem may facilitate 

quantifying its magnitude and 

understanding its role in providing 

protection at the crop level rather 

than under controlled conditions 

(Eyal, 1999). According to Eyal 

(1999), “the International 

Monitoring Nursery philosophy 

executed by CIMMYT can provide 

information on pathogen x cultivar 

interaction in the regional, national 

and international domain. 

Futhermore, it may serve as a 

common basis for broad-base 

evaluation of germplasm to diverse 

pathogen populations under 

variable environmental 

conditions.” 

The information generated by 

this nursery could be extremely 

useful to CIMMYT’s wheat 

breeding program and those of 

national agricultural research 

systems (NARS) in their attempts to 

increase stable resistance over time. 

Material and Methods 

The Septoria Monitoring 

Nursery was divided into two 

sections: 1) one (renewed every 

three years) with the best sources of 

59 

resistance identified by CIMMYT 

and NARS breeding programs and 

2) a tentative group of differentials 

proposed by Dr. Z. Eyal, Tel Aviv 

University, as a fixed group. They 

were Ald/Pvn, Enkoy (K=4500), 

Colotana, IAS 20, Bow CM33203-K- 

9M-2Y-1M-1Y-2M-0Y-1Ptz, Don 

Ernesto (Bow) CM33203-K-9M-33Y- 

1M-500Y-0M-OJ-1J, Seri 82, Kvz- 

K500.L.6.A.4, Beth Lehem, Lakhish, 

Kauz, Penjamo 62, Etit 38 (D), Inbar 

(D), Glennson 81, and Barrigon 

Yaqui (D). 

The same nursery with two 

replications was sent to each site 

during three years to avoid 

environmental and year effects, 

and to obtain more reliable data. 

The first Septoria Monitoring 

Nursery was sent to 23 locations. 

The following group of resistant 

lines selected under Patzcuaro 

(Michoacan state) and Toluca 

(Mexico state) conditions were 

included:

60 

Session 3A — L. Gilchrist, C. Velazquez, and J. Crossa 

1. Trap #1/Bow 

2. Thb//Ias 20/H567.71 

3. PF70354/Bow 

4. Lfn/1158.57//Prl/3/Hahn 

5. Ias 58/4/Kal/Bb//Cj/3/Ald/5/Bow 

6. Br 14*2/Sumai 3 

7. Sushoe #6//Ald/Pav 

8. Br 14*2//Nobre*2/Tp 

9. M2A/Cml//Nyubay/3/CMH 72A .576/Mrg 

10. M2A/Cml//2* Nyubay 

11. CMH80A.253/Sx 

12. CMH80.278/3/Ssfm/H567.71//2*Ssmf 

13. #1959 

14. Sumai#3 

15. CS/Th. curv.//Glenn81/3/Ald/Pvn 

The second Septoria Monitoring 

Nursery was sent to 22 locations 

and included the following resistant 

lines: 

1. Bobwhite (CM 33203-K-10M-7Y-3M-2Y-1M- 

0M) 

2. Cno79/4/CS//Th. curv.//Glenn81/3/Ald/Pvn 

3. TIA.2/4/CS/Th. curv.//Glenn81/3/Ald/Pvn 

4. CS/Th. curv.//Glenn81/3/ Ald/Pvn/4/ CS/Le. 

Rac//*… 

5. Chirya 3 

6. Chirya 1 

7. Chirya 4 

8. CS/Th. curv.//Glenn81/3/Ald/Pvn/4/ Suz8 

9. CS/Th.curv.//Glenn81/3/Ald/Pvn/4/Nanjing 

8401 

10. Eg-A/H567.71//4*Eg-A/3/2*CMH79.243 

11. Cal/NH//H567.71/3/2*Ning 7840/4/… 

12. CMH72A.576/Mrng//CMH78.443/3/ 

CMH79.243/… 

13. CMH77.308/CMH82.205 

14. Ald/Pvn//Ymi #6 

15. Sha 5/Bow 

The nursery included two 

susceptible durum varieties and a 

resistant one, as well as two 

susceptible bread wheat varieties 

and a resistant one. Readings of 

septoria tritici leaf blotch were 

taken using the double digit 

modified scale (Eyal et al., 1987), 

and the analysis was done 

separately by digits. Height and 

spike emergence measurements 

were used as covariants in the 

analysis. 


Seven of the 23 locations were 

included in the analysis of first 

Septoria Monitoring Nursery. 

Practically no infection was 

detected at the other locations due 

to low moisture conditions. The 

sites where weather conditions 

produced medium to good 

epidemics were Argentina (Balcarce 

and Pergamino), Chile (Hidango 

and Chillan), Guatemala 

(Quetzaltenango), Mexico (Toluca, 

four years), and Uruguay (La 

Estanzuela). Some sites were 

eliminated because there was 

strong interference from other 

diseases. Toluca was the only site 

that had no such interference, and it 

allowed four diseases evaluations. 

The variance component 

estimate and the F test for the first 

and the second digits were highly 

significant for the factor site, as was 

the site x genotype interaction 

component, although the latter was 

much smaller than the former 

(Table 1). 

Infection averages per country 

and site are presented in Table 2. 

Results indicate that La Estanzuela 

(Uruguay) and Toluca (Mexico) had 

the heaviest epidemic compared 

with the other sites. 

Table 1. Variance and F test for digits 1 

and 2 of the response to infection by 

Septoria tritici for site and genotype x site 

interaction (1 st SMN). 

Variance 

component F test 

Digit 1 

Site 2.68 82.98*** 

Site x genotype 1.12 1.95*** 

Digit 2 

Site 1.34 40.53*** 


The responses of durum and 

bread wheat lines in the first 

Septoria Monitoring Nursery were 

not significantly different, which 

indicates that at least at those 

locations there were no host-specific 

pathogen populations. There were 

no significant differences between 

the susceptible bread wheat checks 

(Seri 82 and Lakish) and the 

resistant check (Beth Lehem). This 

suggests that the resistant entries 

were not always resistant, and that 

our universal resistant check was 

not always resistant. In the case of 

durum wheat, this difference was 

significant. The resistant variety Etit 

38 was always resistant, while 

susceptible varieties Inbar and 

Barrigon Yaqui were always 

susceptible. 

The mean infection (first and 

second digit) of the varieties across 

sites and years are shown in Table 3. 

The most resistant varieties across 

sites were Trap#1/Bow and #1959, 

of Chinese origin. 

Fourteen of a total of twentytwo 

sites sampled were included in 

the second Septoria Monitoring 

Nursery data analysis. The sites not 

included had problems with 

interference by rust infection or 

experienced low moisture 

conditions. The countries and 

Table 2. Septoria tritici infection average per 

country and site, and disease evaluation for 

digits 1 and 2 (1 st SMN). 

Infection average 

Country and site Digit 1 Digit 2 

Toluca (Mexico) 7.25 6.63 

La Estanzuela (Uruguay) 6.06 6.96 

Chillan (Chile) 6.91 5.32 

SNA-Hidango (Chile) 3.08 5.67 

Balcarce (Argentina) 5.64 4.32 

Pergamino (Argentina) 6.07 4.92 

Quetzaltenango (Guatemala) 2.45 4.07

Table. 3. Infection averages (digits 1 and 2) 

across sites and years (1 st SMN). 

Variety Digit 1 Digit 2 

Trap #1/Bow 3.56 1.49 

Thb//Ias 20/H567.71 4.78 2.70 

PF70354/Bow 4.62 2.73 

Lfn/1158.57//Prl/3/Hahn 4.97 2.61 

Ias 58/4/Kal/Bb//Cj/3/Ald/5/Bow 5.81 3.25 

Br 14*2/Sumai 3 4.25 2.06 

Sushoe #6//Ald/Pvn 4.42 2.92 

Br 14*2//Nobre*2/Tp 

M2A/Cml//Nyubay/3/ 

4.72 2.70 

CMH 72A.576/Mrg 5.36 3.75 

M2A/Cml//2* Nyubay 5.39 3.34 

CMH80A.253/Sx 

CMH80.278/3/Ssfm/ 

6.24 4.79 

H567.71//2*Ssmf 5.51 3.93 

#1959 4.03 1.94 

Sumai#3 

CS/Th. curv. //Glenn81/3/ 

5.25 4.20 

Ald/Pvn 

Tentative differentials 

5.37 3.55 

Ald/Pvn 5.03 3.72 

Enkoy (K=4500) 5.18 3.09 

Colotana 3.06 1.56 

IAS 20 

Bow CM33203-K-9M-2Y-1M- 

3.67 2.31 

1Y-2M-0Y-1Ptz 

Don Ernesto(Bow)CM33203- 

6.29 4.52 

K-9M-33Y-1M-500Y-0M-OJ-1J 6.62 5.50 

Seri 82 7.07 6.33 

Kvz-K500.L6.A.4 6.16 4.48 

Beth Lehem 7.17 6.77 

Lakhish 7.03 6.78 

Kauz 6.92 6.50 

Penjamo 62 7.28 6.75 

Etit 38 (D) 4.04 3.06 

Inbar (D) 4.37 3.15 

Glennson 81 6.44 5.53 

Barrigon Yaqui (D) 7.00 5.74 

locations selected were Argentina 

(Tres Arroyos, La Plata), Chile 

(Temuco), Ethiopia (Holetta), 

Mexico (Toluca, Patzcuaro), 

Portugal (Elvas), Russia 

(Krasnoda), Switzerland (Zurich), 

and Uruguay (La Estanzuela, 

Tarariras). Some of them were 

included for more than one year. 

The variance component 

estimate and the F test for digits 1 

and 2 S. tritici evaluation were 

highly significant for the factor site, 

as was the genotype x site 

interaction component (Table 4). 

Again, the interaction component 

was much smaller than the main 

factor component. 

The S. tritici infection averages 

per country and site for digits 1 

and 2 are presented in Table 5. 

Mexico (Toluca and Patzcuaro) and 

Uruguay (La Estanzuela) had the 

lowest infection averages. This was 

to be expected, given that data for 

these three locations were 

considered in selecting resistant 

lines. 

The contrast between durum 

and bread wheats was significant, 

which indicated that most sites 

included in the second nursery had 

specific pathogen populations for 

every crop (Table 6). As in the first 

nursery, there were no differences 

between the susceptible bread 

wheat checks (Seri 82 and Lakish) 

Table 4. Variance and F test for digits 1 

and 2 of the response to infection by 

Septoria tritici for site and genotype x site 

interaction (2 nd SMN). 

Variance 

component F test 

Digit 1 

Site 1.12 45.07*** 

Site x genotype 

Digit 2 

1.20 2.64*** 

Site 0.78 22.55*** 


Table 5. Septoria tritici infection averages per 

country and site for digits 1 and 2 (2 nd SMN). 

Infection average 

Country and site Digit 1 Digit 2 

Argentina Tres Arroyos 7.81 4.05 

La Plata 6.45 3.46 

Chile Temuco 6.43 5.11 

Ethiopia Holetta 7.64 5.04 

Mexico Toluca 4.87 3.52 

Patzcuaro 6.75 4.90 

Portugal Elvas 7.40 3.94 

Russia Krasnovar 7.36 5.10 

Switzerland Zurich 7.45 3.23 

Uruguay La Estanzuela 6.45 4.47 

Tarariras 7.37 4.98 

Analysis of the Septoria Monitoring Nursery 61 

and the resistant check (Beth 

Lehem). This confirms that the 

resistant check was not always 

resistant, and that our resistant 

check is not universally resistant 

and should be changed. Results 

confirmed that the resistant durum 

variety Etit 38 was always resistant, 

and varieties Inbar and Barrigon 

Yaqui were always 

susceptible(Table 6). 

Infection averages (digits 1 and 

2) of the varieties in the second 

Septoria Monitoring Nursery 

across sites and years are shown in 

Table 7. The most resistant lines 

across sites were: 1) Eg-AH567.71// 

4*Eg-A/3/2*CMH79.243, 2) Cal/ 

NH/H567.71/3/2*Ning 7840/4/ 

CMH83.2277/5/Bow/2*Ning 

7840//CMH83.2277, and 3) Sha 5/ 

Bow. 

Table 6. Differences between average durum 

and bread wheat and resistant (R) and 

susceptible (S) checks for each crop for 

the 1 st SMN, 2 nd SMN, and the combination of 

all sites for the 1 st and the 2 nd SMN. 

Significance 

levels 

Source 

1 

Digit 1 Digit 2 

st SMN 

Bread and durum wheat 

Bread wheat (S) and 

1.93 NS 2.64 NS 

bread wheat (R) 

Durum wheat (S) and 

0.04 NS -0.22 NS 

durum wheat (R) 

2 

1.64 ** 1.38 * 

nd SMN 



1.77 *** 1.89 NS 



-0.07 NS 0.25 NS 


1 

2.02 *** 0.99 ** 

st and 2nd SMN combined 



1.83 *** 2.16 ** 



-0.08 NS 0.23 NS 


NS: Not significant. 

* Significant at the 5% level. 

1.91 *** 1.11 *** 

** Significant at the 1% level. 

*** Significant at the 0.1% level.

62 

Session 3A — L. Gilchrist, C. Velazquez, and J. Crossa 

An analysis of the differential 

group across the seven years and 

all sites also gave significant 

differences between sites and a 

significant sites x varieties value. 

The values of the S. tritici infection 

averages for digits 1 and 2 for each 

variety are in Table 8. 

Table 7. Infection averages (digits 1 and 2) 

across sites and years (2 nd SMN). 

Variety 

Bow CM 33203-K-10M-7Y- 

Digit 1 Digit 2 

3M-2Y-1M-0M 

Cno79/4/CS/Th. curv.// 

6.10 3.26 

Glenn81/3/Ald/Pvn 

TIA.2/4/CS/Th. curv.//Glenn81/ 

6.61 3.62 

3/Ald/Pvn 

CS/Th. curv//Glenn81/3/Ald/ 

6.81 3.92 

Pvn/4/CS/Le.Rac//*… 6.64 3.56 

Chirya 3 6.87 3.75 

Chirya 1 6.82 4.27 

Chirya 4 

CS/Th. curv. //Glenn81/3/Ald/ 

6.94 3.86 

Pvn/4/ Suz8 

CS/Th.curv. //Glenn81/3/Ald/ 

6.26 3.37 

Pvn/4/Nanjing 8401 

Eg-A/H567.71//4*EG-A/3/ 

6.74 4.08 

2*CMH79.243 

Cal/NH//H567.71/3/ 

5.25 2.60 

2*Ning 7840/4/… 

CMH72A.576/Mrng//CMH78.443/ 

5.47 3.38 

3/CMH79.243/… 7.04 5.53 

CMH77.308/CMH82.205 6.67 3.78 

Ald/Pvn//Ymi #6 6.27 3.12 

Sha 5/Bow 

Tentative differentials 

5.96 3.17 

Ald/Pvn 6.10 3.34 

Enkoy (K=4500) 5.37 2.52 


IAS 20 

Bow CM33203-K-9M-2Y-1M- 

4.51 2.34 

1Y-2M-0Y-1Ptz 

Don Ernesto (Bow) CM33203-K 

6.35 3.87 

-9M-33Y-1M-500Y-0M-OJ-1J 6.85 4.45 

Seri 82 7.27 5.39 

Kvz-K500.L.6.A.4 6.60 3.67 


Lakhish 7.82 5.35 

Kauz 7.27 4.74 

Penjamo 62 7.78 5.60 

Etit 38 (D) 4.44 2.90 

Inbar (D) 5.89 3.35 

Glennson 81 6.74 4.75 


A more detailed analysis of 

variety x site interactions will be 

carried out in the near future to 

identify the differential response of 

some lines to the pathogen 

populations in different sites. 


The authors fondly remember 

Dr. Zahir Eyal and recognize his 

positive influence, his wise advice 

to follow this line of research, and 

his keen visualization of its 

potential impact. They also thank 

the NARS cooperators who sent in 

the data that made it possible to 

obtain the reported results. Last, 

but not least, the authors wish to 

thank Dr. Jesse Dubin for 

contributing his well-considered 

ideas on the data analyses. 

Table 8. Septoria tritici infection averages for 

differential varieties across the seven years 

of evaluation covering 33 locations. 

Variety number Digit 1 Digit 2 

Ald/Pvn 5.71 3.43 

Enkoy (K=4500) 5.29 2.69 


IAS 20 

Bow CM33203-K-9M-2Y-1M- 

4.23 2.33 

1Y-2M-0Y-1Ptz 

Don Ernesto (Bow) CM33203-K- 

6.30 4.08 

9M-33Y-1M-500Y-0M-OJ-1J 6.76 4.78 

Seri 82 7.19 5.70 

Kvz-K500.L.6.A.4 6.44 3.90 


Lakhish 7.55 5.81 

Kauz 7.15 5.30 

Penjamo 62 7.61 5.96 

Etit 38 (D) 4.28 2.93 

Inbar (D) 5.37 3.26 

Glennson 81 6.59 4.96 


References 

Eyal, Z., Amiri, Z., and Wahl, I. 1973. 

Physiologic specialization of 

Septoria tritici. Phytopathology 

63:1087-1091. 

Eyal, Z., Sharen, A.L., Prescott, J.M., 


Septoria Diseases of Wheat: 

Concepts and Methods of Disease 

Management. Mexico, D.F.: 

CIMMYT. 46 pp. 

Eyal, Z. 1999. Breeding for resistance 

to Septoria and Stagonospora. In: 

Septoria on Cereals: A Study of 

Pathosystems. Lucas, J.A., Bowyer, 

P. and Anderson, H.M. (eds.). 

CABI Publishing. Wallingford, UK. 

pp. 1-25. 

Gilchrist, L. 1994. New Septoria tritici 

resistance sources in CIMMYT 

germplasm and its incorporation 

in the Septoria Monitoring 

Nursery. In: Proceedings of the 4 th 

International Workshop on: 

Septoria of Cereals. July 4-7, 1994. 

Arseniuk, E., Goral, T., and 

Czembor, P. (eds.). Ihar Radzikow, 

Poland. pp. 187-190. 

Kema, G.H.J., Annone, G.J., Sayoud, 

R., van Silfhout, C.H., van Ginkel, 

M.,and de Bree, J. 1996. Genetic 




pathosystem I. Interaction between 

pathogen isolates and host 

cultivars Phytopathology 86:200- 

212. 






seeedling and adult plant 


87:266-272. 




Van Ginkel, M., and A.L. Scharen. 

1988. Host-pathogen relationships 

of wheat and Septoria tritici. 

Phytopathology 78(6):762-766.

Session 3B: Host-Parasite Interactions 

Host – Parasite Interactions: Stagonospora nodorum 

E. Arseniuk and P.C. Czembor 

Plant Breeding and Acclimatization Institute, Radzików, Poland 

Abstract 

Relative virulence of 15 Stagonospora (Septoria) nodorum (SNB) monopycnidiospore isolates and their mixture was 

studied under field conditions on a differential set of triticale and bread wheat cultivars. The isolates originated from diseased 

triticale and wheat plants sampled in diverse geographical regions of Poland. Significant effects of isolates, cultivars, and 

cultivar by isolate interactions were detected. The interaction between S. nodorum isolates and wheat and triticale 

genotypes appeared to be to a great extent a statistical interaction, rather than a well defined physiological specialization. 

The detection of the interaction was influenced by the amount of disease inflicted by the pathogen isolates on selected host 

genotypes and the effect of environmental conditions on disease development, as well as by the tools and precision with 

which the host was examined. Nonetheless, since the isolate by cultivar interaction was significant in most cases, the term 

virulence is used. The mixture of isolates was classified among isolates showing intermediate virulence on the cultivars 

tested. In comparison to single isolates, the differential capacity of the isolate mixture was also reduced. Relationships 

between mean isolate virulences and cultivar variances of SNB reactions were not significant for leaves (moderate SNB 

level) and significant for heads (low SNB level). A single pathogenic isolate used for screening breeding materials may 

provide reliable information on their SNB resistance. 

Stagonospora nodorum (Berk.) 

Castellani et E.G. Germano 

(=Septoria nodorum (Berk. Berk. in 

Berk. & Broome) [teleomorph 

Phaeosphaeria nodorum (E. Müller) 

Hedjaroude (=Leptosphaeria nodorum 

E. Müller) is a necrotrophic 

pathogen of graminaceous plant 

species. The pathogen, together 

with S. avenae and Septoria tritici, 

belongs to a group of cereal 

pathogens sometimes called 

Septoria complex. Among these 

pathogens special forms have been 

recognized only in S. avenae: f.sp. 

avenae and f.sp. triticea. In the other 

two pathogens, i.e. S. nodorum and 

S. tritici, host specificity is generally 

low, but more pronounced in S. 

tritici (Eyal et al., 1987; Skajennikoff 

and Rapilly, 1983). 

The presence of specificity in 

these pathogen populations is 

based on the analyses of the 

statistical interaction terms between 

cultivars and isolates. The isolate 

by cultivar interaction terms in S. 

nodorum are usually of a smaller 

magnitude than for S. tritici 

(Yechilevich-Auster et al., 1983; 

Scharen and Eyal, 1983; Scharen et 

al., 1985). Therefore, distinguishing 

specificity (virulence) from 

aggressiveness is more difficult for 

S. nodorum. Since specificity in the 

S. nodorum/cereal systems at the 

cultivar level is not so clear, it 

might be called genome specificity. 

Isolate by genotype interactions 

between S. nodorum isolates and 

cereal species have been reported 

by a number of authors under 

controlled environment as well as 

63 

field conditions (Arseniuk et. al., 

1994; Krupinsky, 1986, 1994, 

1997a,b,c). Information on the 

magnitude of such interaction is 

important for inoculum 

composition and resistance 

management in breeding programs. 

Although genetic protection is 

considered the main pillar of host 

defense, the majority of commercial 

wheat cultivars do not have 

suitable protection. 

The lack of resistant germplasm, 

high pathogen variability, and low 

specificity have all contributed to 

the slow progress in breeding for 

resistance and the deficient genetic 

protection in wheat and triticale. 

Therefore, the objective of this 

study was to compare the screening 

efficiency of triticale and wheat 

cultivars for stagonospora

64 

Session 3B — E. Arseniuk and P.C. Czembor 

nodorum blotch (SNB) resistance 

with single isolates and their 

mixture under field conditions. 

Concurrently, the relative virulence 

of S. nodorum isolates, the 

magnitude of cultivar by isolate 

interaction, and the relative 

resistance of the cereal genotypes 

used in the study were examined. 


The relative virulence of 15 

single pycnidiospore isolates of 

Stagonospora (= Septoria) nodorum 

and their mixture was studied in 

1993-1995 under field conditions on 

both winter and spring triticale and 

bread wheat. For the purpose 11 

winter triticale and 4 winter wheat 

cultivars and germplasm lines 

(Tables 1 and 2) and 5 spring 

triticale and 3 spring wheat 

cultivars (Tables 3 and 4) were 

used. The genotypes had been 

preselected earlier based on their 

capacity to differentiate S. nodorum 

isolates in regard to their 

virulence/aggressiveness 

(pathogenicity). (The term 

virulence will be used from this 

point on in this paper, since the 

interaction of isolates by cultivars 

was significant.) 

Fourteen isolates used for the 

study originated from different 

geographical regions of Poland and 

one from Switzerland (87TS-1-1). 

As for host association, of those 15 

isolates, 14 were derived from 

diseased hexaploid triticale plants 

and one (Wen-1-1) from a hexaploid 

bread wheat plant cv. ‘Weneda’ 

(Table 5). No record was made of 

the specific triticale genotypes from 

which the isolates were derived. All 

isolates used in the study were 

derived from single pycnidiospores 

Table 1. Analysis of variance for the amount of SNB on leaves and heads of 11 winter triticale 

and 4 winter wheat cultivars scored on a 0-9 digit scale (0 = resistant, 9 = susceptible) under 

field conditions. 

Leaves Heads 

Source of Mean F Proba- Mean F Probavariation 

D. f. Square value bility D. f. Square value bility 

Years (Y) 2 427.5 21.8 0.01 2 1957.8 2696.1 0.00 

Blocks (B) 

Error 1 (Y × B) 3 19.6 3 0.7 

Scoring dates (S.d.) 3 4217.7 866.7 0.00 2 650.3 4.1 0.07 

Y × S.d. 6 77.7 16.0 0.02 4 55.0 0.3 0.83 

Error 2 (Y×B×S.d.) 9 4.9 6 159.7 

Cultivars (C) 14 113.1 321.3 0.00 14 139.3 346.4 0.00 

Isolates (I) 15 157.3 446.7 0.00 15 131.4 326.8 0.00 

C × I 210 1.4 3.9 0.00 210 1.1 2.8 0.00 

Y × C 28 17.1 48.6 0.00 28 20.2 50.2 0.00 

Y × I 30 26.5 75.4 0.00 28 3.4 8.5 0.00 

S.d. × C 42 4.5 12.7 0.00 30 46.3 115.1 0.00 

S.d. × I 45 2.2 6.3 0.00 30 3.7 9.1 0.00 

Y × C × I 420 0.7 1.9 0.00 56 1.2 3.1 0.00 

Y × S.d. × I 90 1.4 3.9 0.00 60 1.8 4.6 0.00 

Y × S.d. × C 84 1.8 5.2 0.00 420 0.3 0.7 1.00 

S.d. × C × I 630 0.3 0.8 1.00 420 0.7 1.8 0.00 

Y × S.d.× C × I) 1260 0.3 0.7 1.00 840 0.3 0.7 1.00 

Error(Y×B×S.d.×C×I) 2868 0.4 2151 0.4 

Table 2. The expression of virulence by 15 Stagonospora nodorum isolates and their mixture (a composite isolate) on leaves and heads of 11 

winter triticale (t) and 4 winter wheat (w) cultivars under field conditions. 

Almo Ugo Malno Lasko Grado Dagro Bolero Presto Largo LAD- DAD- Alba Jawa Begra Liwilla 

No. Isolate (t) (t) (t) (t) (t) (t) (t) (t) (t) 285 (t) 187 (t) (w) (w) (w) (w) Mean 

1 Lb-2-1 3.9* 4.1 3.7 2.9 4.3 4.5 3.0 3.1 3.5 4.4 3.8 3.5 4.2 4.9 3.4 3.8 

2 Lb-3-1 4.8 4.7 4.1 3.6 4.8 5.0 4.0 3.8 4.2 5.1 4.7 3.9 4.7 5.3 3.5 4.4 

3 Lb-4-1 4.8 4.6 4.3 3.5 4.9 4.9 3.8 3.8 4.3 5.0 4.5 3.9 4.4 5.6 3.6 4.4 

4 Z-20-1 3.4 3.5 3.4 2.6 3.8 3.9 2.9 2.8 3.3 3.6 3.5 3.3 4.1 4.9 3.1 3.5 

5 Z-22-1 4.1 4.2 4.2 3.6 4.9 5.0 3.3 4.1 4.6 5.4 4.8 3.8 4.7 5.6 3.5 4.4 

6 Gw-3-1 5.9 5.8 5.5 4.9 6.2 5.9 4.6 5.3 5.3 5.9 5.6 4.5 5.4 6.1 4.3 5.4 

7 TS87-1-1 5.4 5.4 5.3 4.8 5.8 5.9 4.3 5.2 5.0 5.7 5.1 4.7 5.6 6.1 4.7 5.3 

8 Wen-1-1 5.1 5.3 5.3 4.3 6.0 5.9 4.5 5.3 5.1 5.2 5.4 4.3 5.2 5.6 4.1 5.1 

9 Ml-2-1 3.5 3.3 3.4 2.9 3.9 4.0 2.8 2.8 3.7 3.7 3.5 3.2 4.3 5.0 3.1 3.5 

10 Ch-9-1 3.2 3.5 3.3 2.8 3.7 3.7 2.6 2.8 3.2 3.3 3.3 2.8 4.0 4.8 3.3 3.3 

11 Wr-6-1 4.4 4.2 4.0 3.5 4.5 4.5 3.5 3.6 4.2 4.5 4.4 3.8 4.6 4.9 3.8 4.2 

12 Ch90-3-1 5.1 4.9 4.8 4.1 5.8 5.9 4.1 4.8 4.8 5.6 8.6 3.8 5.1 5.4 3.8 5.1 

13 Rd93-1-1 4.0 3.8 3.7 3.0 4.3 4.3 3.1 3.2 3.5 4.0 4.0 3.4 4.3 5.4 3.7 3.8 

14 T91-1-4 3.4 3.9 3.3 2.8 3.9 4.1 2.8 2.7 3.5 4.1 4.0 3.3 4.3 4.9 3.0 3.6 

15 Lu90-1-1 4.3 4.5 4.3 3.4 5.3 5.3 3.4 4.4 4.7 4.8 4.3 3.8 4.8 5.2 3.6 4.4 

16 Mixture 5.0 4.6 4.5 3.9 5.4 5.3 3.7 4.3 5.0 5.4 4.8 4.0 4.9 5.4 3.5 4.6 

Mean 4.4 4.4 4.2 3.5 4.8 4.9 3.5 3.9 4.2 4.7 4.6 3.7 4.7 5.3 3.6 4.3 

LSD 0.05 = 0.114 for virulence of isolates on leaves; LSD 0.01 = 0.110 for reaction of cultivars on leaves. 

* Mean score on a 0-9 scale of 4 SNB scorings per season × 6 blocks over 3 growing seasons.

and, as determined after the 

research was completed, all were of 

the wheat biotype. 

The isolates used for inoculation 

were increased on bread wheat 

grain. The composite isolate (a 

volumetric mixture of isolates) was 

prepared by mixing equal volumes 

of spore suspensions of all isolates 

adjusted to equal concentrations of 

spores/ml. Plants were inoculated 

at the late boot stage (5 × 106 spores/ml) and after heading (2 × 

106 spores/ml). SNB was rated 

visually on a 0 (resistant) - 9 

(susceptible) scale at about weekly 

intervals. Separate notes were taken 

for leaves and heads four and three 

times, respectively, on winter types, 

and four and two times, 

respectively, on spring types. All 

Table 3.The expression of virulence by 15 Stagonospora nodorum isolates and their mixture (a 

composite isolate) on leaves and heads of 5 spring triticale and 3 spring wheat cultivars un-der 


Jago Maja Gabo Grego Migo Henika Eta Sigma 

No. Isolate (t) (t) (t) (t) (t) (w) (w) (w) Mean 

1 Lb-2-1 2.8* 2.6 2.2 2.9 2.8 3.6 2.4 2.8 2.8 

2 Lb-3-1 2.7 2.8 2.4 3.2 2.7 3.5 3.0 2.8 2.9 

3 Lb-4-1 2.8 2.1 2.3 2.8 2.8 3.4 2.6 2.6 2.7 

4 Z-20-1 1.9 2.1 2.2 2.5 2.7 3.2 2.2 2.3 2.4 

5 Z-22-1 2.2 2.2 2.3 2.3 2.5 2.8 2.2 2.1 2.3 

6 Gw-3-1 3.3 3.3 3.6 3.4 3.7 4.2 3.2 3.0 3.4 

7 TS87-1-1 4.4 4.3 4.4 4.3 4.9 4.9 4.1 4.1 4.4 

8 Wen-1-1 3.8 3.8 3.9 4.2 4.0 4.8 3.9 3.8 4.0 

9 Ml-2-1 2.7 2.8 2.5 2.5 3.2 2.9 2.7 2.9 2.8 

10 Ch-9-1 2.8 2.9 2.7 2.5 3.2 2.7 3.1 2.9 2.8 

11 Wr-6-1 2.7 3.1 2.6 2.3 2.9 2.9 2.6 2.7 2.7 

12 Ch-90-3 2.2 2.4 2.2 2.0 2.4 2.6 2.3 2.1 2.3 

13 Rd91-1-3 2.1 2.5 2.1 2.0 2.3 2.2 2.0 2.2 2.2 

14 T91-1-4 2.9 3.6 3.4 2.9 3.9 3.8 3.3 3.6 3.4 

15 Lu90-1-1 3.8 4.5 4.1 4.3 4.9 4.8 4.2 4.4 4.4 

16 Mixture 3.6 4.1 3.7 3.6 4.3 4.6 3.7 3.9 3.9 

Mean 2.9 3.1 2.9 3.0 3.3 3.6 3.0 3.0 3.1 

LSD0.01 = 0.243 - for virulence of isolates on leaves; LSD0.01 = 0.172 - for reactions of cultivars on leaves. 

* Mean score on a 0-9 scale of 4 SNB scorings per season x 5 blocks over 3 growing seasons. 

Table 4. The expression of virulence by 15 Stagonospora nodorum isolates and their mixture (a 

composite isolate) on heads of 5 spring triticale and 3 spring wheat cultivars under field 

conditions. 

Jago Maja Gabo Grego Migo Henika Eta Sigma 

No. Isolate (t) (t) (t) (t) (t) (w) (w) (w) Mean 

1 Lb-2-1 0.2 0.0 0.1 0.3 0.1 1.3 2.0 2.0 0.7 

2 Lb-3-1 0.1 0.1 0.3 0.2 0.0 2.2 2.0 2.0 0.9 

3 Lb-4-1 0.1 0.0 0.3 0.0 0.0 2.6 3.1 2.0 1.0 

4 Z-20-1 0.0 0.5 0.1 0.4 0.0 2.6 2.8 2.0 1.0 

5 Z-22-1 0.3 0.2 0.1 0.3 0.1 1.7 2.9 2.0 0.9 

6 Gw-3-1 0.7 0.2 0.0 1.0 0.8 2.9 3.5 2.0 1.4 

7 TS87-1-1 0.3 0.2 0.3 0.3 0.1 2.2 3.3 3.5 1.3 

8 Wen-1-1 0.2 0.2 0.6 0.4 0.3 2.9 3.2 3.5 1.4 

9 Ml-2-1 0.3 0.0 0.1 0.1 0.1 1.8 2.2 2.5 0.9 

10 Ch-9-1 0.0 0.1 0.1 0.0 0.0 1.6 1.6 2.0 0.7 

11 Wr-6-1 0.1 0.2 0.1 0.1 0.0 1.6 1.8 1.5 0.7 

12 Ch-90-3 0.4 0.4 0.2 0.3 0.3 1.9 1.9 2.5 1.0 

13 Rd91-1-3 0.0 0.0 0.0 0.6 0.0 1.8 2.0 2.5 0.9 

14 T91-1-4 0.1 0.2 0.2 0.0 0.0 2.2 1.9 2.0 0.8 

15 Lu-90-1 0.1 0.1 0.1 0.0 0.2 2.1 1.8 2.0 0.8 

16 Mixture 0.0 0.3 0.0 0.3 0.2 2.0 2.4 3.0 1.0 

Mean 0.2 0.2 0.2 0.3 0.1 2.1 2.4 2.3 1.0 

LSD 0.01 = 0.268 - for virulence of isolates on heads; LSD 0.01 = 0.189 - for reactions of cultivars on heads. 

* Mean score on 0 - 9 scale of 2 SNB scorings per season ¥ 5 blocks over 3 growing seasons. 

Host – Parasite Interactions: Stagonospora nodorum 65 

the tabulated data (Tables 2, 6, 3, 4) 

are averages of the numbers of 

replications and disease scoring 

dates. 

A split-plot experimental design 

was used. One experimental block 

comprised a number of main plots 

equal to the number of individual S. 

nodorum isolates studied. The main 

plots (rows of parcels) contained 1m2 

parcels (subplots) planted to 

assigned cereal cultivars and 

germplasm lines. Individual isolates 

of the pathogen, considered as the 

main plots, were randomly 

assigned to the sets of subplots. The 

number of subplots within the main 

plot was equal to the number of 

cereal genotypes studied (15: 11 

triticales + 4 wheat genotypes) and 

8 (5 triticales + 3 wheat genotypes) 

for both winter and spring types, 

respectively. Each isolate (main 

plot) had its own control, treated 

with a fungicide (Tilt 250 EC, 0.1% 

a.i., 500 l/ha). In fact, the disease 

scores were actually differences 

between disease levels on cereal 

subpolts inoculated with individual 

isolates and its mirror images 

protected chemically. Isolate main 

plots containing the cereal subplots 

(cultivars/lines) were replicated 

twice for both winter and spring 

types (in 1994 only once). 

Data were subjected to an 

analysis of variance using an 

MSUSTAT computer program, 

Version 5.25 (developed by R. Lund, 

Montana State University, MT 

59715-002, USA) for a split-plot 

experiment. The variance among 

cereal cultivars/germplasm lines 

for disease reaction to individual S. 

nodorum isolates was regressed

66 


Table 5. Origin of Stagonospora nodorum isolates. 

against mean virulence of the 

No. Isolate name Host Geographic origin (location) 

isolates. Similarly, the variance 

1 Lb-2-1 triticale Lubinicko, woj. zielonogórskie 

among isolates for virulence to 

2 

3 

4 

Lb-3-1 

Lb-4-1 

Z-20-1 

triticale 

triticale 

triticale 

Lubinicko, woj. zielonogórskie 

Lubinicko, woj. zielonogórskie 

Zadabrowie. woj. przemyskie 

individual cultivars/lines was 

regressed against mean resistance 

5 

6 

7 

Z-22-1 

Gw-3-1 

TS87-1-1 

triticale 

triticale 

triticale 

Zadabrowie. woj. przemyskie 

Grodkowice, woj. krakowskie 

Z¸rich, Switzerland 

of the cultivars/lines expressed on 

the 0-9 scale. 

8 Wen-1-1 winter wheat Weneda Elblag, woj. torunskie 

9 

10 

Ml-2-1 

Ch-9-1 

triticale 

triticale 

Malyszyn, woj. gorzowskie 

Choryn, woj. poznanskie Results 

11 Wr-6-1 triticale Wrocikowo, woj. olsztynskie 

12 Ch90-3-1 triticale Chelm, woj. chelmskie 

13 Rd93-1-1 triticale Radzików, woj. warszawskie 

All isolates of S. nodorum used 

14 

15 

T91-1-4 

Lu90-1-1 

triticale 

triticale 

Torun, woj. torunskie 

Lucmierz, woj. lódzkie 

in the study were pathogenic to 

leaves and to heads of all triticale 

and bread wheat cultivars (Tables 

2, 6, 3, 4). On average, the disease 

Table 6. The expression of virulence by 15 Stagonospora nodorum isolates and their mixture (a composite 

isolate) on heads of 11 winter triticale (t) and 4 winter wheat (w) cultivars under field conditions. 

on leaves was 2-3 times 

more severe than on 

No. Isolate 

Almo Ugo 

(t) (t) 

Malno Lasko Grado Dagro Bolero Presto Largo 

(t) (t) (t) (t) (t) (t) (t) 

LAD- 

285 (t) 

DAD- 

187 (t) 

Alba Jawa Begra Liwilla 

(w) (w) (w) (w) Mean 

heads. Some of the 

isolates did not cause 

1 Lb-2-1 0.7* 0.8 1.5 1.4 1.3 1.4 0.7 0.8 0.9 1.6 1.1 1.8 2.9 2.7 1.8 1.4 

disease on heads of 

2 Lb-3-1 1.2 1.0 1.7 1.7 1.7 2.2 1.2 1.5 1.5 2.5 1.6 2.7 3.6 3.6 1.9 2.0 spring triticale genotypes 

3 

4 

5 

Lb-4-1 

Z-20-1 

Z-22-1 

1.3 

0.5 

0.9 

1.4 

0.6 

0.8 

2.2 

0.7 

1.1 

2.1 

0.6 

1.2 

2.5 

1.9 

1.2 

2.8 

1.1 

1.8 

1.8 

0.7 

0.8 

1.8 

0.8 

1.3 

1.8 

0.9 

1.0 

3.1 

1.2 

2.1 

1.8 

0.9 

1.6 

2.3 

1.6 

2.3 

3.6 

2.3 

3.2 

3.2 

2.0 

2.9 

2.3 

1.6 

1.9 

2.3 

1.2 

1.6 

(Table 4). The lack of 

disease was due to low 

6 Gw-3-1 2.1 2.1 3.2 2.7 2.5 3.6 2.1 2.8 2.0 3.5 2.6 4.2 5.2 4.4 3.8 3.1 rainfall and drought 

7 

8 

TS87-1-1 

Wen-1-1 

1.8 

1.6 

2.1 

2.2 

3.2 

2.7 

2.8 

2.6 

3.3 

3.3 

3.7 

3.4 

2.2 

1.8 

2.8 

2.3 

2.6 

2.2 

4.0 

3.6 

2.5 

2.6 

3.3 

3.4 

4.9 

4.5 

4.1 

3.9 

3.7 

2.7 

3.1 

2.9 

during the summers. In 

9 Ml-2-1 0.7 0.6 0.9 0.9 2.3 1.3 0.6 0.6 0.8 1.8 1.0 1.7 2.7 2.2 1.7 1.3 spite of the adverse 

10 

11 

12 

Ch-9-1 

Wr-6-1 

Ch90-3-1 

0.7 

1.4 

1.4 

0.5 

1.3 

1.3 

0.6 

1.8 

2.2 

0.7 

1.6 

2.3 

0.9 

1.5 

2.8 

0.9 

2.4 

3.2 

0.7 

1.3 

1.5 

0.7 

1.7 

1.8 

0.6 

1.4 

1.6 

1.3 

2.4 

3.1 

1.0 

1.7 

2.1 

1.2 

2.4 

2.7 

2.1 

3.5 

4.3 

1.9 

3.2 

3.3 

2.9 

2.8 

2.6 

1.1 

2.0 

2.4 

weather, the same 

isolates were able to 

13 Rd93-1-1 0.8 0.9 0.8 1.1 2.3 1.8 0.8 1.2 1.1 1.9 1.4 2.1 2.6 2.4 3.6 1.7 cause the disease on 

14 

15 

T91-1-4 0.6 

Lu90-1-1 1.0 

0.5 

0.9 

1.0 

1.6 

1.4 

1.5 

1.6 

1.7 

1.7 

2.1 

0.8 

1.0 

1.0 

1.4 

1.1 

1.6 

1.8 

2.6 

1.2 

1.4 

2.1 

2.4 

2.8 

3.5 

2.6 

2.7 

1.8 

2.4 

1.5 

1.9 

heads of more SNB 

16 Mixture 1.1 1.3 2.4 2.3 2.4 3.0 1.6 1.7 2.1 2.6 1.7 2.7 4.0 3.3 2.8 2.3 susceptible wheat 

Mean 1.1 1.1 1.7 1.7 2.1 2.3 1.2 1.5 1.4 2.4 1.6 2.4 3.5 3.0 2.5 2.0 cultivars. 

LSD0.01 = 0.141 - for virulence of isolates on heads; LSD0.01 = 0.136 for reaction of cultivars on heads. 

* Mean score on a 0-9 scale of 3 SNB scorings per season ¥ 6 blocks over 3 growing seasons. 

Due to a large 

number degrees of freedom and 

Table 7. Analysis of variance for the amount of SNB on leaves and heads of 5 spring triticale low error values, most of the 

and 3 spring wheat cultivars scored on a 0-9 digit scale (0 = resistant, 9 = susceptible) under 


Leaves Heads 

Source of Mean F Proba- Mean F Probavariation 

D. f. Square value bility D. f. Square value bility 

sources of variation included in the 

analysis of variance (Tables 1 and 7) 

proved to be significant. The main 

effects of cultivars and isolates 

Blocks (B) 4 844.03 18.13 0.01 4 13.17 1.84 0.28 

were highly significant. It is 

Scoring dates (R.d.) 3 1553.60 33.37 0.00 1 39.55 5.52 0.08 noticeable that the effect of isolates 

Error (B × S.d.) 

Cultivars (C) 

Isolates (I) 

12 

7 

15 

46.56 

193.32 

11.3 

272.50 

15.65 

0.00 

0.00 

4 

7 

15 

7.17 

238.49 

4.58 

552.86 

10.62 

0.00 

0.00 

was smaller than that of cultivars. 

This would indicate that the 

C × I 

S.d. × C 

S.d. × I 

105 

21 

45 

0.636 

4.95 

0.693 

0.90 

6.97 

0.98 

0.76 

0.00 

0.51 

105 

7 

15 

0.71 

2.55 

0.167 

1.65 

5.91 

0.39 

0.01 

0.00 

0.98 

reaction of cultivars to inoculation 

with different isolates of S. nodorum 

S.d. × I × C 

Error (B×S.d.×C×I) 

315 

2032 

0.239 

0.709 

0.34 0.00 105 

1016 

0.129 

0.431 

0.30 1.00 was determined mainly by the

cultivar genotype. Nonetheless, the 

differences in virulence among 

isolates were large enough to make 

cultivar response range from 

resistant to susceptible, depending 

on the isolate used (Tables 2, 6, 3, 4). 

The effect of cultivar by isolate 

interaction was not significant only 

for SNB assessment on leaves of 

spring genotypes (Table 7). In all 

other cases, the latter effect, though 

highly significant, contributed only 

slightly to the total variance (Tables 

1 and 7). 

The significance of cultivar by 

isolate interaction indicated that 

there is some degree of specificity 

in the host-pathogen relationship. 

The low specificity in the 

pathosystem was confirmed 

through Spearman rank 

correlations. They revealed that 

rankings of the genotypes on their 

disease reaction to inoculation with 

individual S. nodorum isolates, and 

conversely, the rankings of isolates 

on their virulence expressed on the 

genotypes were correlated. 

The analyses of variance of the 

disease scores revealed significant 

differences between disease scoring 

dates, primarily on leaves. This 

means that the disease progressed 

with the passing of time. For SNB 

on heads, scoring dates were 

bordering on significance for both 

winter and spring genotypes. This 

indicates that, due to adverse 

environmental conditions 

(primarily summer droughts), 

disease progress over time was 

slower on heads than on leaves 

(Tables 1 and 7). The highly 

significant interactions between 

disease scoring dates and other 

components of the analysis of 

variance indicate that the disease 

response progressed at different 

rates (Tables 1 and 7) on individual 

genotypes (S.d. by C) between 

consecutive scoring dates, and that 

the isolates (S.d. by I) caused more 

disease during the intervals 

between consecutive scoring dates. 

This may have something to do 

with the susceptibility of plant 

tissue at different growth stages. 

Older tissue may be more 

susceptible. The significance of 

second and third degree 

interactions among years, scoring 

dates, isolates, and cultivars 

indicated that disease progress was 

influenced by all factors involved, 

i.e. host and pathogen genotypes, 

as well as the environment. 

It should be pointed out that the 

interactions of years with isolates 

and cultivars (Table 1 and 7), 

although significant, were low and 

contributed only slightly to total 

variation. Thus rankings of 

cultivars based on their SNB 

reaction and isolates on their 

Cultivar variances 

4.6 

4.2 

3.8 

3.4 

3.0 

2.6 

Cv. variance = 1.306 + 0.488 (mean isolate virulence) 

r = 0.682, p

68 



Isolate variances 

5.6 

5.4 

5.2 

7 

6 

5 

4 

3.2 

2.8 


Mixture 

5.0 

Gw-3-1 TS87-1-1 

4.8 

4.6 

Lb-4-1 

Ch90-3-1 

Z-22-1 

4.4 T91-1-4 

Lu90-1-1 

Lb-3-1 

4.2 

4.0 

3.8 

2.6 

Wr-6-1 

Ch-9-1 

2.8 

MI-2-1 

Lb-2-1 

Z-20-1 

3.0 

Rd93-1-1 

3.2 

Cv. variance = 1.203 + 1.094 (mean isolate virulence) 

r = 0.607, p



4.6 

4.0 

3.4 

2.8 

2.2 

1.6 

3.2 3.6 4.0 4.4 4.8 5.2 5.6 

Mean cultivars reactions on leaves (0-9 scale) 

Figure 5. Relationship between the mean reactions of 11 winter triticale (t) and 4 winter wheat 

(w) cultivars and variances of SNB induction on leaves of the cultivars by 15 Stagonospora 

nodorum isolates and their mixture (3 years’ data). 

5.5 

5.0 

4.5 

4.0 

3.5 

3.0 

2.5 

2.0 

1.5 

r = 0.044, n.s. 

Lasko (t) 

Bolero (t) 

Presto (t) 

Largo (t) 

Bolero (t) 

Ugo (t) 

Almo (t) 

Presto (t) 

Liwilla (w) 

Alba (w) 

Lasko (t) 

Malno (t) 

DAD-187 (t) 

Malno (t) 

Almo (t) 

Largo (t) 

Grado (t) 

Ugo (t) 

DAD-187 (t) 

Dagro (t) 

LAD-285 (t) 

Alba (w) 

Liwilla (t) 

LAD-285 (t) 

Dagro (t) 

Jawa (w) 

Grado (t) 

Begra (w) 

Begra (w) 

Jawa (w) 

Isolate variance = 0.285 + 11.022 

(mean cultivar reaction) 

r = 0.624, p < 0.03 

1.0 

0.8 1.4 2.0 2.6 3.2 3.8 

Mean cultivars reaction on heads (0-9 scale) 

Figure 6. Relationship between the mean reactions of 11 winter triticale (t) and 4 winter wheat 

(w) cultivars and variances of SNB induction on heads of the cultivars by 15 Stagonospora 

nodorum isolates and their mixture (3 years’ data). 


7.0 

6.5 

6.0 

5.5 

r = 0.577, n.s. 

Sigma (w) 

5.0 

Henika (w) 

4.5 

4.0 

Gabo (t) 

Eta (w) 

3.5 

Jago (t) Maja (t) 

3.0 Grego (t) 

Migo (t) 

2.5 

2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8 

Mean cultivar reaction on leaves (0-9 scale) 

Figure 7. Relationship between mean reactions of 5 spring triticale (t) and 3 spring wheat (w) 

cultivars and variances of SNB induction on leaves of the cultivars by 15 Stagonospora nodorum 

isolates and their mixture (3 years’ data). 

Host – Parasite Interactions: Stagonospora nodorum 69 

showed two distinct resistance 

groups (Figures 7 and 8). 

Correlations between mean host 

reactions on leaves and heads and 

the variances in SNB induction 

among isolates were significant 

only for heads (Figures 5 and 7) and 

not for leaves (Figures 6 and 8). It 

was found that a highly susceptible 

genotype is not necessarily efficient 

in differentiating virulence among 

isolates (Figures 5, 4, 7, 8). 

Conclusions 

The results produced in the 

study do not seem to support that 

using a mixture of S. nodorum 

isolates is the most efficient way to 

differentiate cereal breeding 

materials on their SNB resistance. 

The finding for S. nodorum is in 

accordance with results obtained by 

Zelikovitch and Eyal (1991) that 

inoculation of wheat seedlings and 

adult plants with a mixture of S. 

tritici isolates resulted in significant 

suppression of symptoms (necrosis 

and pycnidial coverage) compared 

to the most virulent single isolate in 

the mixture. 

1. Screening for SNB resistance 

with a few virulent isolates that 

also show good differential 

capacity seems most appropriate. 

Screening breeding materials 

with a single highly virulent 

isolate may provide reliable 

information on their SNB 

resistance. 

2. Sets of selected isolates and 

cultivars differentiated each 

other sufficiently well, but 

according to cluster analyses 

similar results could have been 

obtained with a lower number of 

both isolates and germplasm 

lines.

70 


3. The reported data indicate that 

the interaction between S. 

nodorum isolates of the wheat 

biotype and wheat and triticale 

genotypes to a great extent is 

more a matter of statistics than a 

well defined physiological 

specialization. Whether the 

interaction is detected or not 

depends upon the amount of 

disease inflicted by the pathogen 

isolates on selected host 

genotypes, the effect of 

environmental conditions on 

disease development, and the 

tools and precision with which 

the host has been examined. 


This study was financially 

supported by the ICD-RSE-FAS- 

USDA (Project no. PL-AES-241, 

Grant no. MR-USDA-93-139) and 

by the Plant Breeding and 

Acclimatization Institute. The 

technical assistance of T. Bajor, E. 

Matyska, and E. Pawióska is 

gratefully acknowledged. 


2.4 

2.0 

1.6 

1.2 

0.8 

Isolate variance = 0.048 + 0.503 (mean cultivar reaction) 

r = 0.928, p = 0.01 

References 

Arseniuk, E., A L. Scharen, P.M. Fried, 

and H.J. Czembor. 1994. 

Pathogenic interactions in X 

Triticosecale - Septoria spp. and 

Triticum aestivum - Septoria spp. 

systems. Hod. Rol. Aklim., Nasien. 

(Special Edition) 38(3/4):101-108. 

Eyal, Z., A.L. Scharen, J.M. Prescott, 

and M. van Ginkel. 1987. The 



Management. Mexico D.F.: 


Eyal, Z. 1992. The response of fieldinoculated 

wheat cultivars to 

mixtures of Septoria tritici isolates. 

Euphytica 61:25-35. 

Krupinsky, J.M. 1986. Virulence on 

wheat of Leptosphaeria nodorum 

isolates from Bromus inermis. Can. 

J. Plant Path. 8:201-207. 


of Stagonospora nodorum from 

alternative hosts after passage 

through wheat. Hod Rol. Aklim., 

Nasien. (Special Edition) 38(3/ 

4):123-126. 

Krupinsky, J.M. 1997a. 

Aggressiveness of Stagonospora 

nodorum isolates obtained from 

wheat in the Northern Great 

Plains. Plant Dis. 81:1027-1031. 

Henika (t) 

Eta (w) 

Sigma (w) 

0.4 

Migo (t) 

Jago (t) Maja (t) 

Gabo (t) Grego (t) 

0.0 

-0.2 0.4 1.0 1.6 2.2 2.8 3.4 

Mean cultivar reaction on heads (0-9 scale) 

Figure 8. Relationship between mean reactions of 5 spring triticale (t) and 3 spring wheat (w) 

cultivars and variances of SNB induction on heads of the cultivars by 15 Stagonospora nodorum 

isolates and their mixture (3 years’ data). 

Krupinsky, J.M. 1997b. Stability of 

Stagonospora nodorum isolates from 

perennial grass hosts after passage 

through wheat. Plant Dis. 81:1037- 

1041. 

Krupinsky, J.M. 1997c. Aggressiveness 


from perennial grasses on wheat. 

Plant Dis. 81:1032-1036. 

Scharen, L.A., and Z. Eyal. 1983. 

Analysis of symptoms on spring 

and winter wheat cultivars 

inoculated with different isolates 

of Septoria nodorum. 


Scharen, L.A., Z. Eyal, M.D. Huffman, 

and J.M. Prescott. 1985. The 

distribution and frequency of 

virulence genes in geographically 

separated populations of 

Leptosphaeria nodorum. 


Skajennikoff, M., and F. Rapilly. 1983. 

Aggressivness of Septoria nodorum 

on wheat and triticale. Effects of 

the host and infected organs. 

Agronomie 3:131-140. 

Yechilevich-Auster, M., E. Levi, and 

Z. Eyal. 1983. Assessment of 

interactions between cultivated 

and wild wheats and Septoria 

tritici. Phytopathology 73:1077- 

1083. 

Zelikovitch, N., and Z. Eyal. 1991. 

Reduction in pycnidial coverage 

after inoculation of wheat with 

mixtures of isolates of Septoria 

tritici. Plant Dis. 75:907-910.

Identification of a Molecular Marker Linked to Septoria 

Nodorum Blotch Resistance in Triticum tauschii Using 

F2 Bulked Segregant 

N.E.A. Murphy, 1 R. Loughman, 2 R. Wilson, 2 E.S. Lagudah, 3 

R. Appels, 3 and M.G.K. Jones1 1 WA State Agriculture Biotechnology Centre, Division of Science and Engineering, Murdoch University, 

Murdoch, Australia 

2 Agriculture Western Australia, Bentley Delivery Centre, Western Australia 

3 Plant Industries, CSIRO, Canberra, Australia 

Abstract 

A search was conducted for a molecular marker linked to a gene for resistance to septoria nodorum blotch in the 

Triticum tauschii accession RL5271. DNA was extracted from leaves of F2 plants which were progeny tested to identify 

homozygous resistant and homozygous susceptible F2 plants. The DNA from the homozygous resistant plants was pooled 

together and the low copy sequences were enriched using renaturation kinetics and hydroxyapatite to remove the repetitive 

DNA sequences. The pooled DNA from the homozygous susceptible plants was treated in the same manner. The pooled 

DNA and the parental DNA were screened using RAPD primers. Two markers present in the pooled resistant DNA and 

in the parental DNA were identified and cloned. These markers were verified using RFLPs with the cloned marker as a 

probe. One of the probes did not produce any polymorphism as a RFLP, even when a number of different restriction 

enzymes were used. The second marker was polymorphic between the two parents when the DNA was restricted with 

HindIII and then MseI. In the 14 homozygous F2 plants tested, the marker was completely linked to the resistance gene. 

This marker may be valuable in introgressing the resistance gene from T. tauschii into a commercial bread wheat cultivar. 

Septoria nodorum blotch is the 

major disease of wheat (Triticum 

aestivum L.) in the Western 

Australian wheat belt. It is caused 

by Stagonospora nodorum (Berk.) 

Castellani & E.G. Germano 

(teleomorph Phaeosphaeria nodorum 

(E. Müller) Hedjaroude). The 

preferred method of control is the 

use of resistant cultivars, but this 

has been limited in the past by the 

lack of major genes for resistance. 

In bread wheat inheritance of 

resistance to septoria nodorum 

blotch is frequently complex 

(Mullaney et al., 1982; Scharen and 

Krupinsky, 1978). 

The complex and additive 

nature of septoria nodorum 

resistance in bread wheats has 

made the selection for resistance 

difficult. Relatively small 

improvements in the overall 

resistance can be difficult to 

identify, as they can be masked by 

strong environmental effects. 

Selection of resistant plants is 

complicated by the association of 

resistance and both plant height 

and maturity (Rosielle and Brown, 

1980; Scott et al., 1982). The use of a 

molecular marker would help 

overcome these problems by 

avoiding interpretation of 

phenotype under environmental 

influences (Allen, 1994). 

Furthermore, if the molecular 

marker is co-dominant, it will make 

it possible to identify an individual 

plant as homozygous for resistance 

without further progeny testing. 

This ability to identify homozygous 

71 

plants would be particularly useful 

in any program where extensive 

backcrossing would be required, 

such as the introgression of a 

resistance gene from wild wheats. 

The aim of this work was to 

identify a molecular marker that is 

linked to a single gene conferring 

resistance to septoria nodorum 

blotch identified in the accession 

RL5271 of the wild wheat Triticum 

tauschii. 


A cross between the resistant 

accession RL5271 and the 

susceptible accession CPI110889 

was progeny tested. The F2 plants 

were progeny tested using F3

72 

Session 3B — N.E.A. Murphy, R. Loughman, R. Wilson, E.S. Lagudah, R. Appels, and M.G.K. Jones 

families to identify homozygous F2 

plants. The DNA of eight 

homozygous resistant F2 plants 

and 14 homozygous susceptible F2 

plants was selected for the analysis. 

Equal amounts of DNA from 

the homozygous resistant F2 plants 

were bulked together as was the 

DNA from the homozygous 

susceptible F2 plants. Each bulked 

sample and the DNA from each 

parent were divided into two 

aliquots. One aliquot was left 

untreated. The second aliquot was 

treated to enrich the proportion of 

low copy sequence DNA by 

removing the repetitive DNA 

sequences using hydroxyapatite 

after selective renaturation. The 

technique followed Eastwood et al. 

(1994). The double-stranded DNA 

was removed from the samples 

after a Cot value of 120 had been 

achieved (Smith and Flavell, 1975). 

The DNA was re-suspended in 

0.1xTE buffer and diluted to a final 

concentration of 5ng/ml of DNA. 

RAPD reactions were carried 

out on a Perkin-Elmer PE9600. The 

random primers were produced by 

Operon Technologies (Alameda, 

Ca.). The RAPD products were 

electrophoresed on polyacrylamide 

gels, and the gels were stained 

using ethidium bromide with gel 

images recorded digitally using a 

Bio-Rad Gel Doc 1000 system. For 

each primer nine reactions were 

carried out: a negative control, 

sterile distilled water, was used 

instead of template DNA, the next 

four reactions used the total 

genomic DNA as template, and the 

final four reactions used the nonrepetitive 

DNA as template. 

If a polymorphism was 

identified, the polymorphic band 

was stabbed with a sterile syringe 

needle. The needle was washed in 

sterile distilled water which was 

used as template for a further 

RAPD reaction using the same 

primer and reaction conditions that 

had generated the polymorphism. 

The amplified fragment was ligated 

into the plasmid pGEM-T. The 

plasmids were transformed into E. 

coli cells by heat shock. The 

following day colonies were 

screened using PCR primers, and 

permanent cultures were 

established from insert-containing 

clones. 

The cloned polymorphic band 

was used as an RFLP probe to 

verify and determine the linkage of 

the potential marker to the 

resistance gene. Total genomic 

DNA of the parental accessions was 

digested with a number of 

restriction enzymes, singly and in 

combination, to find a restriction 

enzyme that would produce a 

polymorphism with the marker 

between the resistant and the 

susceptible parent. The marker 

band was prepared using an alkali- 

SDS minprep, double digested with 

NcoI and SacI, separated on an 

agarose gel and purified using 

agarase. The purified band was 

labeled using random nonamer 

primers with 32P as dCTP. The 

membranes were hybridized 

overnight, washed the following 

morning, and exposed to 

autoradiograph film for up to one 

week. 

When a suitable restriction 

enzyme had been selected, the 

DNA from the selected seven 

homozygous resistant F2 plants 

and seven homozygous susceptible 

F2 plants was digested, 

electrophoresed and blotted using 

an alkali capillary blot. The 

membranes were autoradiographed 

for up to two weeks. 

Results 

Sixty random primers were 

used to screen the DNA samples. 

Two polymorphic bands were 

identified by comparing the 

banding pattern of the resistant 

parent and the resistant bulk with 

the susceptible parent and the 

susceptible bulk. The first was 

amplified using primer OPJ6 and 

was approximately 770bp long 

(OPJ6770 ). The second polymorphic 

band was amplified using primer 

OPJ18 and the fragment was 

approximately 350bp (OPJ18350 ). 

Both bands were ligated into 

pGEM-T. 

For the first marker, OPJ6770 , no 

restriction enzyme nor combination 

of enzymes tested was able to 

produce a polymorphism between 

the resistant and the susceptible 

parent. Consequently the marker 

could not be tested for its linkage to 

resistance. The second marker, 

OPJ18350 , produced a 

polymorphism between the 

resistant and susceptible parent 

when the DNA was double 

restricted with HindIII and 

followed by MseI. The 

polymorphism was present as an 

extra band in the resistant parent. 

All of the F2 plants tested were 

correctly classified as resistant or 

susceptible when the marker was 

used.

Discussion 

A marker linked to a resistance 

gene to septoria nodorum blotch in 

the Triticum tauschii accession 

RL5271 has been found. The marker 

and the resistance gene appear to 

be completely linked; however, a 

greater number of plants need to be 

tested to develop a more accurate 

estimate of the linkage. The 

multiple bands produced when the 

marker was used as an RFLP probe 

indicate that regions of repetitive 

DNA exist within the marker, 

which is not uncommon (Eastwood 

et al., 1994). 

The RFLP probe is currently 

being sequenced and primers 

designed that will allow the 

development of a sequence 

characterized amplified region 

(SCAR). This will allow a simpler 

and faster test to be developed. The 

simpler assay will be required if it 

is to be used extensively in a 

marker-assisted selection program. 

If the designed primers do amplify 

a polymorphism between the 

Identification of a Molecular Marker Linked to Septoria Nodorum Blotch Resistance in Triticum tauschii 73 

resistant and the susceptible plants, 

it may be one of several types. The 

primers may amplify a region that 

is present in the resistant plants but 

not in the susceptible plants. This 

marker will be dominant and will 

not allow for the identification of 

heterozygotes; however, this will 

enable simple alternatives to 

running the PCR product on a gel 

to determine if the band is present 

or not to be used (Dedryver et al., 

1996). This will remove one of the 

major time constraints and limiting 

factors in the screening of large 

numbers of plants. Alternatively, 

the SCAR primers could amplify 

different size fragments between 

the resistant and the susceptible 

plants. This type of polymorphism 

will allow heterozygotes to be 

identified (co-dominant), as both 

alleles will be amplified. This in 

turn will allow the selection of 

homozygotes for use in a 

backcrossing population, where the 

direct and accurate selection of 

homozygotes will be of greatest 

benefit. 

References 

Allen, F.L. 1994. Usefulness of plant 

genome mapping to plant 

breeding. In Plant Genome 

Analysis (G.M. Gresshoff, ed.). 

CRC Press, London. 

Dedryver, F., M.F. Jubier, J. 

Thouvenin, and H. Goyeau. 1996. 

Molecular markers linked to the 

leaf rust resistance gene Lr24 in 

different wheats. Genome 39:830- 

835. 

Eastwood, R.F., E.S. Lagudah, and R. 

Appels. 1994. A directed search for 

DNA sequences tightly linked to 

cereal cyst nematode (CCN) 

resistance in Triticum tauschii. 

Genome 37:311-319. 

Mullaney, J., M. Martin, and A.L. 

Scharen. 1982. Generation mean 

analysis to identify and partition 

the components of genetic 

resistance to Septoria nodorum in 

wheat. Euphytica 31:539-545. 

Rosielle, A.A., and A.G.P. Brown. 

1980. Selection for resistance to 

Septoria nodorum in wheat. 


Scharen, A.L., and J.M. Krupinsky. 

1978. Detection and manipulation 

of resistance to Septoria nodorum in 

wheat. Phytopathology 68:245-248. 

Scott, P.R., P.W. Benedikz, and C.J. 

Cox. 1982. A genetic study of the 

relationship between height, time 

of ear emergence and resistance to 

Septoria nodorum in wheat. Plant 


Smith, D.B., and R.B. Flavell. 1975. 

Characterisation of the wheat 

genome by renaturation kinetics. 

Chromosoma 50:223-242.

74 

Inheritance of Septoria Nodorum Blotch Resistance in a 

Triticum tauschii Accession Controlled by a Single Gene 

N.E.A. Murphy, 1 R. Loughman, 2 R. Wilson, 2 E.S. Lagudah, 3 

R. Appels, 3 and M.G.K. Jones1 1 WA State Agriculture Biotechnology Centre, Division of Science and Engineering, Murdoch University, 


2 Agriculture Western Australia, Bentley Delivery Centre, Western Australia 


Abstract 

A potentially useful source of resistance has been identified in an accession of Triticum tauschii. A cross was made 

between the resistant T. tauschii accession, RL5271, and a susceptible accession, CPI110889, to study the genetics of 

resistance from this source. The parental accessions and the F1 and F3 progeny were screened in the glasshouse as seedlings. 

The resistant parent took significantly longer to develop symptoms, developed significantly fewer lesions, and expressed 

significantly lower levels of disease than the susceptible parent. The F1 mean response for disease severity indicated there was 

no complete dominance. The genotypic ratios generated by screening the F3 families were not significantly different from the 

genotypic ratio expected for a single gene. The effectiveness and simple genetic control of the resistance in the T. tauschii 

accession RL5271 may be useful as a resistance source in a bread wheat breeding program. 

Septoria nodorum blotch, 

caused by Phaeosphaeria nodorum (E. 

Müller) Hedjaroude (anamorph 


Castellani, and E.G. Germano), is 

the principal foliar disease of wheat 

(Triticum aestivum L.) in the cereal 

belt of Western Australia (Murray 

and Brown, 1987). The preferred 

method of control is the use of 

resistant cultivars. In bread wheat 

inheritance of resistance to septoria 

nodorum blotch is reported to be 

complex, with an additive action of 

the genes (Mullaney et al., 1982; 

Scharen and Krupinsky, 1978). 

Resistance is often linked to a 

number of traits such as height and 

maturity (Rosielle and Brown, 1980; 

Scott et al., 1982), which makes 

breeding for resistance difficult. 

Promising levels of resistance to 

septoria nodorum blotch were 

found when a collection of T. 

tauschii accessions was investigated 

for resistance to septoria nodorum 

blotch. The ability to use these 

potential resistance sources in a 

wheat breeding program will be 

influenced by the number of genes 

controlling the resistance and its 

expression in a bread wheat 

background. The aim of this work 

was to investigate the differences 

between the parents in the 

components of resistance and to 

determine the number of genes 

controlling resistance to septoria 

nodorum blotch in the Triticum 

tauschii accession RL5271. 


The resistant T. tauschii 

accession RL5271 was crossed to a 

susceptible accession CPI110889. 

The 17 F1 progenies were selfed, 

producing 300 F2s which were 

selfed to produce the F3 families. 

The F1 plants were screened for 

resistance to assess dominance, and 

the F3 plants were screened to 

determine the genotypic ratio, 

which was used to estimate the 

number of genes controlling 

resistance. 

The T. tauschii seed was 

germinated on sterile filter papers 

in petri dishes and vernalized 

before being sown into pots in a 

glasshouse. In the F3 generation, a 

random selection of approximately 

200 F3 families was screened 

sequentially in two subpopulations. 

Each sub-population 

was grown on a single bench in the 

glasshouse, and each F3 family 

contained 10 plants. 

The plants were inoculated 

when the third leaf on the main 

stem had emerged. A single isolate 

of Stagonospora nodorum was used. 

The inoculum was produced using 

V8 Czapek-Dox agar (V8CDA) as a

modified method of Cooke and 

Jones (1970). The plants were 

inoculated with 106 spores/mL, 

with a surfactant, until the point of 

run-off using an airless spraypainting 

gun while the pots were 

revolving on a turntable at 33 rpm. 

After inoculation the plants were 

placed in a humidity chamber for 

48 hours and then returned to the 

bench. The plants were rated using 

the youngest fully emerged leaf at 

the time of inoculation on the main 

tiller eight days after inoculation. 

The leaves were rated using disease 

score (DS), a 0 to 5 severity scale 

where 0 was an immune response 

and a score of 5 was given if the 

leaves were fully necrosed. The DS 

is based upon the number, size, and 

type of lesions, as well as the area 

of the leaf covered by the lesions. 

The two parental accessions 

were assessed twice for two 

components of resistance, and the 

F1 plants were assessed once. The 

components were the incubation 

period (IP, the number of days from 

the time of inoculation till 

symptoms first appear) and the 

infection frequency (IF, the number 

of lesions per square centimeter of 

leaf tissue at IP). In the first 

screening the IF had to be 

transformed using a natural 

logarithmic function, and during 

the second screening it was 

transformed using a square root 

function to remove the trends in the 

residuals. 

The F3 families were classified 

using the response of individual 

plants within an F3 family. During 

the rating it was evident from the 

parental accession’s response that a 

Inheritance of Septoria Nodorum Blotch Resistance in a Triticum tauschii Accession Controlled by a Single Gene 75 

score of less than 2.5 was resistant 

and a score of equal to or greater 

than 2.5 was susceptible. A F3 

family was classified as resistant if 

all its plants had a DS of less than 

2.5 and as susceptible if all the 

plants had a disease score greater 

than or equal to 2.5. Any family 

with plants with a DS of less than 

2.5 and greater than 2.5 were 

classified as segregating. 

Results 

In both tests the components of 

resistance showed significant 

differences between the resistant 

and susceptible parents in their 

response to infection. The IP for the 

parents was not significantly 

different in the first screening but 

the resistant parent (RL5271) had a 

Table 1. The incubation period (IP), infection 

frequency (IF), and disease score (DS) of the 

F1 mean response during screening 1, and the 

parental accessions, RL5271 and CPI110889, 

during screenings 1 and 2. 

IF 

IP (lesions/ 

(days) cm2 ) i DS 

Screening 1 

F1 8.5bii RL5271 

0.8a 1.3b 

(Resistant parent) 

CPI110889 

6.8a 0.8a 0.4a 

(Susceptible parent) 

Screening 2 

RL5271 

5.9a 2.0b 2.2c 

(Resistant parent) 

CPI110889 

5.5a 2.4a 0.9a 

(Susceptible parent) 3.5b 5.8b 3.3b 

i Back transformed values are presented for the 

IF in both screenings. 

ii Numbers from the same screening and for the 

same trait followed by different letters are 

significantly different from each other at p

76 

Session 3B — N.E.A. Murphy, R. Loughman, R. Wilson, E.S. Lagudah, R. Appels, and M.G.K. Jones 

different from the expected 

genotypic ratio for a single gene 

(X2 =0.81, p=0.67) (Table 2). When 

the genotypic ratios of the two subpopulations 

were compared using 

a Pearson’s chi-squared test for 

homogeneity, they were not 

significantly different (X2 =0.84, 

p=0.66). The combined ratio (45 

resistant F3 families, 97 

segregating, and 52 susceptible 

families) was not significantly 

different from the genotypic ratio 

expected for a single gene (X2 =0.50, 

p=0.78) (Table 2). 

Discussion 

Resistance to septoria nodorum 

blotch in the Triticum tauschii 

accession RL5271 is controlled by a 

single gene. From the F1 mean 

response there was no evidence of 

complete dominance or 

recessiveness for resistance. The 

resistant parent took significantly 

longer to develop symptoms, 

developed significantly fewer 

infections and expressed 

significantly lower levels of disease 

than the susceptible parent. The 

variation in the resistance 

components between the two 

parents was consistent with 

previous studies reporting a 

resistance response. The IP has 

been shown to vary significantly 

among wheats with longer IP being 

associated with resistance 

(Wilkinson et al., 1990; Bruno and 

Nelson, 1990). The IF was 

significantly lower for the resistant 

parent, which is consistent with 

previous work where a low IF has 

been associated with resistance 

(Wilkinson et al., 1990; Ma and 

Hughes, 1993; Loughman et al., 

1996). The inheritance of the IF has 

been found to be clearly dominant 

in the F1 (Ma and Hughes, 1993) 

which is consistent with this study. 

Resistance in Triticum tauschii 

accession RL5271 is the first singlegene 

resistance to septoria 

nodorum blotch identified in the D 

genome. Resistance to septoria 

nodorum blotch has been 

previously identified in another 

Triticum tauschii accession 

(=Aegilops squarrosa Tausch). It was 

found to be controlled by three 

genes, located on chromosomes 3D, 

5D, and 7D, with 3D being the most 

important of the three (Nicholson 

et al., 1993). The simplicity of the 

inheritance and strong expression 

of the resistance gene in T. tauschii 

warrants making an attempt at 

introgressing the resistance into a 

bread wheat background. 


This work was funded by the 

Grains Research and Development 

Corporation of Australia. 

References 

Bruno, H.H., and L.R. Nelson. 1990. 

Partial resistance to septoria glume 

blotch analyzed in winter wheat 

seedlings. Crop Science 30:54-59. 

Cooke, B.M., and D.G. Jones. 1970. 

The effect of near-ultraviolet 

irradiation and agar medium on 

the sporulation of Septoria nodorum 

and Septoria tritici. Transactions of 

the British Mycological Society 

54:221-226. 

Loughman, R., R.E. Wilson, and G.J. 

Thomas. 1996. Components of 


graminicola and Phaeosphaeria 

nodorum in spring wheats. 


Ma, H., and G.R. Hughes. 1993. 


blotch in several Triticum species. 


Mullaney, J., M. Martin, and A.L. 






Murray, G.M., and J.F. Brown. 1987. 

The incidence and relative 

importance of wheat diseases in 

Australia. Australasian Plant 


Nicholson, H., N. Rezanoor, and A.J. 






Chinese Spring wheat. Plant 

Breeding 110:177-184. 






1978. Detection and manipulation 

of resistance to Septoria nodorum in 



Cox. 1982. A genetic study of the 





Wilkinson, C.A., J.P. Murphy, and 

R.C. Rufty. 1990. Diallel analysis of 

components of partial resistance to 

Septoria nodorum. Plant Disease 

74:47-50.

Session 4: Population Dynamics 

Population Genetics of Mycosphaerella graminicola and 

Phaeosphaeria nodorum 

B.A. McDonald, 1 C.C. Mundt, 2 and J. Zhan2 1 Institute of Plant Sciences, Phytopathology Group, Zürich, Switzerland 

2 Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA 

Abstract 

Restriction fragment length polymorphisms (RFLPs) in the nuclear (nu) and mitochondrial (mt) genomes were used to 

determine the genetic structure of populations of Mycosphaerella graminicola and Phaeosphaeria nodorum from 

around the world. Both fungi have genetic structures consistent with a regular sexual cycle and a high degree of gene flow 

occurring on a global scale. Gene as well as genotype diversity in the nuDNA are high for both fungi. There was no 

evidence for widespread clones within field populations of either fungus. While both fungi had less diversity in the mtDNA, 

M. graminicola exhibited significantly less diversity for the mtDNA compared to P. nodorum. Mycosphaerella 

graminicola populations from Patzcuaro, Mexico, and Australia exhibited significantly lower gene diversity, suggesting 

that these populations originated from a limited number of founders. Collections of M. graminicola taken from the same 

field between 1990 and 1995 showed that genetic drift is negligible, suggesting that effective population sizes are very large. 

A replicated field experiment showed that selection can cause significant changes in genotype frequencies during the course 

of a growing season, and that the contributions of immigration and recombination to genetic diversity in field populations 

can change over the growing season. 

Ten years ago, we began 

developing DNA-based markers as 

tools to learn about the population 

genetics of the wheat leaf blotch 

pathogen Mycosphaerella 

graminicola. One year later, we 

began parallel studies using the 

same genetic tools for the wheat 

glume blotch pathogen 

Phaeosphaeria nodorum. We began 

with two elementary questions 

regarding the population genetics 

of both fungi. How much genetic 

diversity is present within 

populations? How is genetic 

diversity distributed within and 

among populations? As our 

knowledge of the genetic structure 

of both pathogens deepened, we 

addressed more complex questions. 

What are the relative contributions 

of sexual and asexual reproduction 

to the genetic structure of 

populations? How stable are 

populations over time? Does 

selection for specific pathogen 

genotypes occur on particular host 

genotypes? Is there evidence for 

host specialization in these 

pathosystems? 

To address the latter questions, 

we utilized increasingly 

sophisticated field experiments to 

differentiate among the various 

evolutionary forces acting on 

populations of these fungi. In this 

manuscript, I will briefly review 

our understanding of the 

population genetics of both fungi at 

this point in time. The majority of 

this manuscript was distilled from a 

review chapter written for the Long 

Ashton Symposium on Septoria in 

Cereals held in 1997. Detailed data 

to support our interpretations are 

presented in that chapter 

(McDonald et al., 1999). 


77 

DNA markers 

The RFLP markers utilized for 

these studies were developed in the 

same way for both fungi utilizing 

the methods described in 

McDonald and Martinez (1990b). 

Single-locus probes were used to 

measure gene diversity for 

individual RFLP loci and to 

measure population subdivision 

and genetic similarity among 

populations (McDonald and 

Martinez, 1990a; Boeger et al., 1993; 

McDonald et al., 1994; Keller et al., 

1997a,b). Probes that hybridized to 

repetitive elements were used for

78 

Session 4 — B.A. McDonald, C.C. Mundt, and J. Zhan 

DNA fingerprinting and to make 

measures of genotype diversity 

(McDonald and Martinez, 1991; 

Keller et al., 1997a,b). To measure 

variation in the mitochondrial (mt) 

genome, we purified mtDNA and 

used it as a probe to hybridize to 

the entire digested mitochondrial 

genome for each individual. 

Sampling methods 

Hierarchical sampling methods 

now are commonly used in plant 

pathology (Kohli et al., 1995; 

McDonald et al., 1995; McDonald, 

1997). For many of the collections 

described in this manuscript, a 

standardized six-site hierarchy was 

used to sample field populations 

(McDonald et al., 1999). For other 

field collections, long transects were 

arranged in a field and leaves were 

sampled at 1-2-meter intervals 

along each transect. For some 

collections, leaves were collected at 

random in a field. All isolates in a 

collection were taken from a single 

field at a single time point for the 

majority of collections. I refer to 

these collections as field 

populations. Four collections of 

isolates came from the same 

country or geographical region, but 

did not originate from a single field. 

I refer to these as regional 

populations to distinguish them 

from field populations. 

For P. nodorum, the Arkansas 

population was made up of isolates 

collected from infected seed from 

two different seed lots distributed 

in Arkansas. The crested 

wheatgrass population consisted of 

isolations made from the weed 

crested wheatgrass over a two-year 

period in the state of North Dakota. 

The goal for each collection was to 

have a large enough field sample to 

be confident that allele frequencies 

for individual RFLP loci were 

representative of the entire field 

population. Only populations 

having at least 25 isolates were 

included in the analysis. A 

summary of the M. graminicola and 

P. nodorum isolates in our collection 

was presented previously 


Data analysis 

Methods used to measure gene 

and genotype diversity, genetic 

similarity, population subdivision, 

and gametic disequilibrium have 

been published elsewhere 

(McDonald and Martinez, 1990a; 

Boeger et al., 1993; Chen et al., 1994; 

Chen and McDonald, 1996). The 

DNA fingerprint probes were 

validated for both fungi in previous 

experiments (McDonald and 

Martinez, 1991; Keller et al., 1997b). 

Here we will pay special attention 

to the collection of M. graminicola 

isolates from Mexico. 


Genetic diversity and 

mating/reproduction systems 

Both gene and genotype 

diversity are high for both fungi. 

On average, 18 alleles were present 

for 11 RFLP loci across ~2000 

isolates of M. graminicola, and five 

alleles were present for seven loci 

across ~950 isolates of P. nodorum. 

In each population, between 3-4 

alleles were present in ~90% of the 

isolates (McDonald et al., 1999). 

Nei’s measure of gene diversity 

across all populations averaged 0.44 

across eight RFLP loci for M. 

graminicola and 0.51 across seven 

RFLP loci for P. nodorum. Though 

both fungi exhibited high gene 

diversities, M. graminicola had a 

significantly greater number of 

alleles per locus then P. nodorum 

and P. nodorum had a more even 

distribution of allele frequencies. 

Comparisons of gene diversities 

across populations revealed some 

interesting patterns. The Israeli 

population had significantly higher 

gene diversity than other 

populations around the world 

(McDonald et al., 1999). We 

interpret this as evidence that the 

Middle East is a center of diversity 

for M. graminicola, and the likely 

center of origin for this fungus. The 

Mexican population exhibited 

lower gene diversity than other 

populations. It was made from 

leaves collected by Dr. Lucy 

Gilchrist at a CIMMYT disease 

nursery in Patzcuaro, a location 

remote from other wheat fields (L. 

Gilchrist, personal communication). 

The Mexican population also 

exhibited a lower genotype 

diversity than expected (McDonald 

et al., 1999), having a higher 

incidence of a few widespread 

clones than any other population 

surveyed. These findings are 

consistent with a small founding 

population that has not undergone 

regular sexual reproduction. We 

hypothesized that these isolates 

represent an historic inoculation of 

the Patzcuaro site with a few 

isolates that were not sexually 

compatible. We hope to collect 

another M. graminicola field 

population from wheat-growing 

areas of Mexico to obtain a more 

representative sample of this 

fungus in that region.

The gene diversity in the P. 

nodorum population was lowest in 

the collections from crested 

wheatgrass and from Mexico 

(McDonald et al., 1999). These were 

the only two collections that were 

fixed for one allele at an RFLP 

locus. These populations also 

exhibited substantial differences in 

allele frequencies for some RFLP 

loci when compared to other 

populations (McDonald et al., 

1999). It is possible that the lower 

gene diversity and different allele 

frequencies in the crested 

wheatgrass population resulted 

from selection due to host 

specialization. However, the 

finding that common alleles are 

shared between isolates taken from 

crested wheatgrass and wheat 

suggests that crested wheatgrass 

may serve as a reservoir of 

inoculum for P. nodorum that infects 

wheat. The differences in the 

Patzcuaro population may reflect 

founder events and the geographic 

isolation of this location as 

described previously for M. 

graminicola. 

Genotype diversity. Genotype 

diversity in the nuclear genome 

was high for both fungi (McDonald 

et al., 1999). In the majority of 

populations surveyed, each leaf 

was colonized by a unique fungal 

genotype. When isolates shared the 

same DNA fingerprint, they usually 

were sampled from the same leaf. 

The only evidence for a widespread 

clone in M. graminicola was in the 

Patzcuaro population. The only 

evidence for a widespread clone in 

P. nodorum was from our first 

collection in a Texas field 


Population Genetics of Mycosphaerella graminicola and Phaeosphaeria nodorum 79 

It appears that the typical 

population of both fungi exhibits a 

low degree of clonality at the field 

level. Clones were usually 

distributed across an area of 

approximately 1 square meter and 

did not become widespread. This 

finding is consistent with limited 

spread of the splash-dispersed 

conidia for both fungi. 

Our interpretation of the high 

degree of genotype diversity is that 

populations of both fungi undergo 

regular sexual cycles and that the 

primary inoculum for both fungi is 

likely to be ascospores (Chen and 

McDonald, 1996; Keller et al., 

1997b). We have used tests for the 

randomness of associations among 

RFLP loci to indicate the frequency 

of sexual recombination for both 

fungi (Chen and McDonald, 1996). 

Associations were random for both 

fungi in the cases where sample 

sizes were adequate to make robust 

tests for disequilibrium, supporting 

the hypothesis of random mating. 

Though the sample size was 

smaller (N=160), the Israel 

population also showed the 

gametic equilibrium and high 

genotypic diversity typical of a 

random mating fungus (McDonald 

et al., 1999), suggesting that the 

teleomorph is present in the Middle 

East. 

After a field experiment 

provided evidence that the 

teleomorph was contributing 

significantly to infection during the 

growing season (Zhan et al., 1998), 

we sampled lower leaves in the 

crop canopy in Oregon and found 

the teleomorph existing as a 

significant fraction of all fruiting 

bodies on wheat leaves (C. Cowger, 

C.C. Mundt, and B.A. McDonald, 

unpublished). 

mtDNA diversity. For both fungi, 

the mtDNA exhibited less diversity 

then the nuDNA. The mtDNA 

genome ranges from 48-62 kb in size 

for both fungi. Among 385 isolates 

of P. nodorum from Switzerland, 

Texas, and Oregon, we found only 

46 different mtDNA haplotypes 

compared to over 300 nuDNA 

haplotypes. Fifteen of the mtDNA 

haplotypes were shared among 

these field populations (S. Keller 

and B. A. McDonald, unpublished 

data). 

The mtDNA of M. graminicola 

exhibited even lower diversity. We 

routinely found only 2-3 mtDNA 

haplotypes in field populations of 

M. graminicola (McDonald et al., 

1999). We sometimes found only 

one M. graminicola mtDNA 

haplotype in a field (McDonald et 

al., 1999). We picked the three most 

common mtDNA haplotypes from 

around the world and digested the 

mtDNA with 10 different restriction 

enzymes that sampled ~5% of the 

entire 48 kb of mtDNA sequence in 

an attempt to detect cryptic 

variation. Types 1, 2, and 3 mtDNA 

haplotypes produced identical 

digestion patterns with all enzymes 

in all populations tested, suggesting 

that these mtDNA haplotypes are 

identical globally (B.A. McDonald 

and K. Hogan, unpublished). We 

have proposed that the limited 

mtDNA diversity is due to a 

selective sweep that occurred as M. 

graminicola populations became 

specialized to infect bread wheat 

(McDonald et al., 1999).

80 


Genetic drift 

The high nuclear gene diversity 

found in most populations for both 

fungi suggests that population 

sizes are very large and the effects 

of genetic drift are small. In a 

previous experiment, we showed 

that the population genetic 

structure of an M. graminicola 

population did not change over a 

three-year period of 1990-1992 

(Chen et al., 1994). We have 

extended data from this population 

to 1995 and find the same result. 

The frequencies of neutral RFLP 

alleles did not change significantly 

over time (Table 1), and the degree 

of population subdivision across 

years is less than 1% (Table 2), 

demonstrating that population 

sizes are large enough to make 

genetic drift insignificant as an 

evolutionary force in populations 

of this fungus. 

Population subdivision 

and gene flow 

The distribution of genetic 

diversity across populations was 

consistent with a significant level 

of gene flow for both fungi. 

Common alleles at individual 

RFLP loci were shared among 

nearly all populations (McDonald 

et al., 1999), and allele frequencies 

often were quite similar though 

populations were separated by 

thousands of kilometers 

(McDonald et al., 1999). We have 

interpreted this similarity as 

indicating a significant degree of 

gene flow among populations of 

both fungi on an international scale 

(McDonald et al., 1995; Keller et al., 

1997). Global estimates of GST were 

0.06 and 0.07 for M. graminicola and 

P. nodorum, respectively. These 

values of GST are consistent with 

movement of 11 and 7 individuals 

among populations globally every 

generation. 

Table 1. Allele frequencies for seven RFLP loci in Mycosphaerella graminicola collections from 

Corvallis, Oregon, in 1990, 1991, 1992, and 1995. Alleles present at a frequency of less than 0.05 in 

all four populations were pooled into one category (allele “p”). Sample sizes (N) used to 

calculate allele frequencies are shown for each locus. The chi-square values and their degrees 

of freedom (in parentheses) for measurement of population differentiation are also included. 

Populations 

RFLP Locus Allele 1990 1991 1992 1995 c2 pSTS192-PstIA 1 0.943 0.877 0.911 0.953 6.36(6) 

2 0.030 0.088 0.054 0.047 

p 0.027 0.035 0.036 0.000 

N 401 57 56 43 

pSTS192-PstIB 1 0.980 1.000 0.981 1.000 1.99(3) 

P 0.020 0.000 0.019 0.000 

N 406 56 56 44 

pSTS14-PstI 1 0.808 0.825 0.821 0.818 0.85(6) 

2 0.187 0.175 0.179 0.182 

p 0.005 0.000 0.000 0.000 

N 407 57 56 44 

pSTS2-PstI 1 0.648 0.667 0.571 0.818 8.87(9) 

2 0.085 0.056 0.125 0.023 

3 0.203 0.204 0.214 0.136 

p 0.065 0.074 0.089 0.023 

N 400 54 56 44 

pSTL10-PstI 1 0.680 0.649 0.518 0.643 14.51(9) 

2 0.051 0.053 0.107 0.000 

3 0.220 0.281 0.357 0.286 

p 0.049 0.018 0.018 0.071 

N 409 57 56 43 

pSTL53-PstI 1 0.475 0.561 0.536 0.465 26.86(18) 

2 0.119 0.070 0.107 0.023 

3 0.161 0.158 0.232 0.070 

5 0.042 0.053 0.000 0.047 

6 0.119 0.140 0.107 0.209 

7 0.027 0.000 0.000 0.047 

p 0.057 0.018 0.018 0.140 

N 404 57 56 43 

pSTS197-PstI 1 0.632 0.649 0.589 0.591 

2 0.227 0.175 0.286 0.364 9.65(9) 

3 0.108 0.158 0.107 0.045 

p 0.033 0.018 0.018 0.000 

N 259 57 56 44 

Table 2. Nei’s measures of gene diversity and population subdivision for 7 RFLP loci in 

Mycosphaerella graminicola populations collected from Corvallis, Oregon, in 1990, 1991, 1992, 

and 1995. 

Hi a 

The present lack of subdivision 

in the nuclear genome probably 

reflects historic movement of both 

fungi around the world. It is 

possible that gene flow is not a 

RFLP Loci 1990 1991 1992 1995 HTb HSc Dstd Gste pSTS192A-PstI 0.110 0.222 0.166 0.091 0.126 0.125 0.001 0.008 

pSTS192B-PstI 0.039 0.000 0.104 0.000 0.039 0.039 0.000 0.007 

pSTS14-PstI 0.312 0.289 0.294 0.298 0.307 0.307 0.000 0.000 

pSTS2-PstI 0.531 0.508 0.610 0.323 0.524 0.520 0.004 0.007 

pSTL10-PstI 0.486 0.497 0.592 0.526 0.506 0.501 0.005 0.010 

pSTL53-PstI 0.716 0.633 0.636 0.722 0.704 0.700 0.004 0.006 

pSTS197-PstI 0.537 0.523 0.560 0.517 0.540 0.536 0.004 0.007 

Pooled 0.390 0.382 0.423 0.354 0.392 0.390 0.003 0.006 

Notes:a= gene diversity for each population; b= combined gene diversity across all collections; c= gene 

diversity within populations; d= gene diversity among populations; e= population differentiation

significant evolutionary force at 

present. However, we consider it 

more likely that some gene flow 

continues as a result of the global 

commerce in grain. The obvious 

mechanism for gene flow on a 

regional basis is air-dispersed 

ascospores. In the case of P. 

nodorum, the most likely 

mechanism for intercontinental 

dispersal is infected seed (King et 

al., 1983). Since it has been shown 

that M. graminicola can infect seed 

(Brokenshire, 1975) we consider it 

likely that this also is the 

mechanism for long distance gene 

flow in M. graminicola. Whatever 

the mechanism, the high degree of 

similarity in populations around 

the world for both fungi suggests 

that they have been transported 

around the world by humans. 

Evidence for selection 

We recently completed an 

experiment to measure competition 

among 10 genotypes of M. 

graminicola in a field setting. The 10 

isolates were inoculated onto three 

host treatments consisting of a 

moderately resistant wheat variety 

(Madsen), a susceptible wheat 

variety (Stephens) and a 1:1 

mixture of these cultivars. Our 

most important finding in this 

experiment was that intense 

competition appeared to occur 

among the different genotypes. 

Significant changes in the 

frequencies of specific pathogen 

genotypes occurred over the season 

(McDonald et al., 1999). Some 

isolates showed evidence for 

adaptation to particular hosts. The 

results from this experiment 

provided our first direct evidence 

Population Genetics of Mycosphaerella graminicola and Phaeosphaeria nodorum 81 

that selection operates on specific 

M. graminicola pathogen genotypes 

in a field setting. 

We have not yet conducted 

similar replicated field experiments 

to measure selection in P. nodorum. 

But we have indirect evidence that 

selection does not result in 

widespread clones that are adapted 

to specific host genotypes. In an 

experiment conducted in 

Switzerland in collaboration with 

Martin Wolfe’s group, we sampled 

50 isolates of P. nodorum from each 

of nine wheat fields near Zurich. 

Three different wheat varieties were 

represented three times each among 

the nine wheat fields. Though fields 

planted to the same variety used the 

same source of seed, no genotypes 

were shared among field 

populations. Only six pairs of clones 

were found among the 432 isolates 

that were assayed. Isolates with the 

same DNA fingerprints always 

came from the same site within a 

field (Keller et al., 1997b). 

Taken together, all of our 

experiments suggest that nuclear 

genotypes do not persist through 

time for either fungus. Instead, the 

genes are the units of selection that 

are carried forward across 

generations. Selection operates on 

the population instead of the 

individual. In order to gain a 

representative spectrum of the 

diversity for virulence in natural 

populations, plant breeders should 

include the widest possible 

diversity of strains when screening 

germplasm for resistance to these 

fungi. Similarly, chemical 

companies should include at least 

several hundred strains in their 

screens for resistance to fungicides. 

Conclusions 

Given our present data, we have 

drawn the following conclusions 

regarding the evolutionary forces 

that affect the population genetics 

of M. graminicola and P. nodorum: 

• For both fungi, the mating system 

includes both sexual and asexual 

reproduction. Asexual 

reproduction may have an 

important impact over an area of 

a few square meters, but the 

sexual reproduction has much 

greater consequences for the 

evolutionary biology of both 

fungi. Genotypes are ephemeral 

but genes persist in populations 

through time. 

• Population sizes are large enough 

to make genetic drift negligible 

for both fungi. Large population 

sizes also ensure that ample 

mutations are present in every 

population to allow for a rapid 

response to selection, e.g. 

mutations from avirulence to 

virulence for major resistance 

genes. The population from 

Patzcuaro, Mexico, exhibits a 

genetic structure consistent with 

a founder effect. 

• Gene flow is sufficient to unite 

large geographical areas into a 

single genetic population. If gene 

flow is ongoing, then breeders 

should continue to test their 

resistant lines over the widest 

possible geographical area. If 

gene flow is episodic, continued 

vigilance is needed to limit the 

spread of new virulence genes 

and fungicide resistance genes. 

Quarantines in areas with low 

gene diversity, such as Australia, 

should be enforced to limit the 

evolutionary potential of these 

populations. If CIMMYT 

continues to use Patzcuaro as a 

field site to screen for resistance

82 


to M. graminicola and P. nodorum, 

it may want to consider 

introducing more diverse fungal 

populations from other parts of 

Mexico into this disease nursery. 

• Selection appears to operate on 

both nuclear and mitochondrial 

genomes in M. graminicola. 

Though selection may increase 

the frequency of particular 

genotypes over the course of a 

growing season, it appears that 

particular genotypes are unlikely 

to reach high frequencies within 

field populations because of the 

limited dispersal potential for 

conidia. But the genes in the most 

fit individuals will persist and be 

recombined to create novel 

genotypes in the next growing 

season. Over the course of many 

growing seasons, selection will 

change the frequency of genes 

that affect adaptation to the 

wheat host, but new genotypes 

will appear each season. It is too 

early to say if selection operates 

the same way in P. nodorum. 

In summary, the population 

genetics of P. nodorum and M. 

graminicola are very similar. This 

probably reflects the similarity in 

their life histories. Both fungi 

produce airborne sexual ascospores 

and splash-dispersed asexual 

spores. They both infect aboveground 

plant parts on the same 

host and they both infect seeds that 

can be transported globally as part 

of the world commerce in wheat. 

Use of multi-allelic, neutral genetic 

markers combined with 

hierarchical sampling has allowed 

us to achieve a much greater 

understanding of the population 

biology of both fungi. 


BAM gratefully acknowledges 

the many collectors and 

collaborators around the world who 

responded to his request for 

infected leaf material. Funding for 

this project came from the USDA 

National Research Initiative 

Competitive Grants Program (Grant 

# 93-37303-9039), the National 

Science Foundation (Grant # DEB- 

9306377), the Texas Agricultural 

Experiment Station (Hatch project 

#6928), and the Swiss National 

Fund (Grant # 5002-38966). 

References 

Boeger, J.M., Chen, R.S., and 

McDonald, B.A. 1993. Gene flow 

between geographic populations of 


(anamorph Septoria tritici) detected 

with RFLP markers. 


Brokenshire, T. 1975. Wheat seed 

infection by Septoria tritici. 

Transactions of the British 

Mycological Society 64:331-335. 

Chen, R.S., and McDonald, B.A. 1996. 

Sexual reproduction plays a major 

role in the genetic structure of 

populations of the fungus 

Mycosphaerella graminicola. Genetics 

142:1119-1127. 

Chen, R.S., Boeger, J.M., and 

McDonald, B.A. 1994. Genetic 

stability in a population of a plant 

pathogenic fungus over time. 

Molecular Ecology 3:209-218. 

Keller, S.M., McDermott, J.M., 

Pettway, R.E., Wolfe, M.S., and 

McDonald, B.A. 1997a. Gene flow 

and sexual reproduction in the 

wheat glume blotch pathogen 

Phaeosphaeria nodorum (anamorph 

Stagonospora nodorum). 


Keller, S.M., Wolfe, M.S., McDermott, 

J.M., and McDonald, B.A. 1997b. 

High genetic similarity among 

populations of Phaeosphaeria 

nodorum across wheat cultivars and 

regions in Switzerland. 


King, J.E., Cook, R.J., and Melville, S.C. 

1983. A review of Septoria diseases 

of wheat and barley. Annals 

Applied Biology 103:345-373. 

Kohli, Y., Brunner, L.J., Yoell, H., 

Milgroom, M.G., Anderson, J.B., 

Morrall, R.A.A., and Kohn, L.M. 

1995. Clonal dispersal and spatial 

mixing in populations of the plant 

pathogenic fungus, Sclerotinia 

sclerotiorum. Molecular Ecology 

4:69-77. 

McDonald, B.A. 1997. The population 

genetics of fungi: tools and 

techniques. Phytopathology 87:448- 

453. 


1990a. DNA restriction fragment 

length polymorphisms among 


(anamorph Septoria tritici) isolates 

collected from a single wheat field. 



1990b. Restriction fragment length 

polymorphisms in Septoria tritici 

occur at a high frequency. Current 

Genetics 17:133-138. 


1991. DNA fingerprinting of the 

plant pathogenic fungus 



Experimental Mycology 15:146-158. 

McDonald, B.A., Miles, J., Nelson, L.R., 

and Pettway, R.E. 1994. Genetic 

variability in nuclear DNA in field 

populations of Stagonospora 

nodorum. Phytopathology 84:250- 

255. 

McDonald, B.A., Pettway, R.E., Chen, 

R.S., Boeger, J.M., and Martinez, J.P. 

1995. The population genetics of 

Septoria tritici (teleomorph 

Mycosphaerella graminicola). 

Canadian Journal of Botany 73 

(supplement), S292-S301. 

McDonald, B.A., Zhan J., Yarden O., 

Hogan K., Garton J., and Pettway 

R.E. 1999. The population genetics 

of Mycosphaerella graminicola and 

Phaeosphaeria nodorum. pp. 44-69 In: 

Septoria in Cereals: a Study of 


P., Anderson, H.M., eds. CABI 

Publishing, Wallingford, UK. 

Zhan, J., Mundt, C.C., and McDonald, 

B.A. 1998. Measuring immigration 

and sexual reproduction in field 

populations of Mycosphaerella 


88:1330-1337.

Characterization of Less Aggressive Stagonospora 

nodorum Isolates from Wheat 

E. Arseniuk, 1 H.S. Tsang, 2 J.M. Krupinsky, 3 and P.P. Ueng 4 

1 Plant Breeding and Acclimatization Institute, Radzików, Poland 

2 Department of Biochemistry, University of Maryland, MD, USA 

3 USDA-ARS, Northern Great Plains Research Lab, Mandan, ND, USA 

4 USDA-ARS, Molecular Plant Pathology Lab, Beltsville, MD, USA 

Abstract 

Two less aggressive Stagonospora nodorum isolates, 9074 and 9076, were characterized by inoculation tests, mating 

ability, and molecular tools. As expected, they caused mild symptom severity on wheat, triticale, and rye. They crossed 

with other S. nodorum isolates and had “+” mating type determinant(s). These two isolates also had the same restriction 

patterns and sequences in the internal transcribed spacer (ITS) region of rDNA similar to other S. nodorum isolates. 

With AFLP analysis, it was concluded that these less aggressive S. nodorum isolates were closely related and genetically 

different from highly aggressive ones. 




(E. Müller) Hedjaroude) causes 

septoria nodorum blotch on wheat, 

barley, and other small grains 

(Sprague, 1950). Genetic variation 

of S. nodorum isolates has been 

reported (Allingham and Jackson, 

1981; Krupinsky, 1997a,b; Scharen et 

al., 1985). Understanding this 

genetic variation would help in the 

selection and/or development of 

resistant germplasm. This study 

was undertaken to determine 

whether less aggressive isolates 

could be characterized and how 

they relate to highly aggressive 

isolates. 


Inoculation tests 

Stagonospora nodorum isolates 

were obtained from lesions on 

infected wheat (Sn26-1, 9074, and 

9076) and rye (Sn48-1) in Poland 

and USA. Isolates 9074 and 9076 

were collected from Richland and 

Gallatin counties in Montana, 

respectively. These two isolates 

were associated with mild symptom 

severity on detached wheat leaves 

and seedlings, and considered to be 

less aggressive isolates (Krupinsky, 

1997a,b). Plants were inoculated by 

spraying a 3-ml pycnidiospore 

suspension (3 x 10 6 spores/ml) per 

pot onto 10-day-old seedlings. 

Three wheat cultivars (Alba, Begra, 

and Liwilla), two triticales (Bogo 

and Pinokio) and one rye (Zduno) 

were used as host plants. The 

plants were maintained in a high 

humidity environment for 72 h 

after spraying. Fourteen days after 

inoculation, 10 primary leaves were 

assessed for percentage necrosis 

and scored using a 1 (resistant) to 9 

(susceptible) scale. The experiments 

were repeated three times. 

Determination of mating type 

Isolates 9074 and 9076 were 

mated in vitro with reference “+” 

and “–“ strains of the pathogen 

with a procedure developed in the 

lab (Arseniuk et al., 1997). 

DNA isolation and 

characterization of ITS of 

nuclear rDNA 

Growth of fungal culture in a 

liquid medium, isolation and 

purification of genomic DNA 

mainly followed the procedures 

83 

described earlier (Ueng et al., 1992). 

The internal transcribed spacer 

(ITS) region of the nuclear rDNA 

repeat units was amplified by PCR 

following the protocol reported 

earlier (Ueng et al., 1998; White et 

al., 1990). Two highly aggressive S. 

nodorum isolates, 8408 and 9506-2 

(Krupinsky, 1997a; Krupinsky, 

unpublished data) were compared 

with the two less aggressive ones, 

9074 and 9076. The PCR products of 

the ITS region were restricted with 

endonuclease enzymes, DraI, 

HaeIII, HpaII, and PvuII. The 

sequences of PCR-amplified ITS 

regions were determined using a 

DNA sequencer (Applied 

Biosystem 373A, Perkin Elmer, 

Foster City, CA). 

AFLP analysis 

The amplified restriction 

fragment polymorphism (AFLP) 

technique was used to explore 

DNA polymorphisms in four S. 

nodorum isolates with different 

degrees of aggressiveness on 

wheat. The AFLP Analysis 

System I (Life Technologies, 

Gaithersburg, MD) kit was used 

following the protocol provided by

84 

Session 4 — E. Arseniuk, H.S. Tsang, J.M. Krupinsky, and P.P. Ueng 

the manufacturer. Cluster analysis 

using the unweighted pair group 

method with an arithmetic average 

(UPGMA) algorithm was 

performed to produce a phenogram 

based on the banding patterns 

produced by AFLP (Rohlf, 1990). 


In the greenhouse seedling 

inoculations, isolates 9074 and 9076 

generally showed lower symptom 

severity on wheats, triticales, and 

rye (Table 1). The results agreed 

with the previous work on 

detached wheat leaves and 

seedlings (Krupinsky, 1997a,b). It 

was also shown that Polish isolate 

Sn48-1, originally isolated from rye, 

caused severe symptom severity on 

rye (Table 1) and less symptom 

severity on triticale (a cross 

between wheat and rye). 

After the isolates mated, 

pseudothecia with mature 

ascospores were formed after 50-80 

days of incubation. Isolates 9074 

and 9076 were both shown to be 

“+” mating types. The ITS regions 

of rDNA in these two isolates had 

the same endonuclease restriction 

patterns and DNA sequences as the 

two highly aggressive isolates 8408 

and 9506-2, and other wheatbiotype 

S. nodorum isolates (Beck 

and Ligon, 1995; Ueng et al., 1998). 

This would confirm that these two 

less aggressive isolates are wheatbiotype 

S. nodorum isolates. Of a 

total 390 bands generated by 48 

AFLP reaction combinations, only 

78 bands were shared by all four 

isolates in this study. The genetic 

diversity was high in highly 

aggressive isolates, and between 

highly and less aggressive ones 

(Figure 1). Cluster analysis showed 

great similarity between the two 

less aggressive isolates. The 

presence of differential AFLP 

fragments in the highly aggressive 

isolates may be related to 

aggressiveness and may be useful 

to identify virulent elements in the 

future. 


The authors thank Yan Zhao of 

USDA-ARS, MPPL, Beltsville, MD, 

for his technical support and 

Weidong Chen of the University of 

Illinois for his comments and 

suggestions. 

References 

Allingham, E.A., and L.F. Jackson. 

1981. Variation in pathogenicity, 

virulence, and aggressiveness of 

Septoria nodorum in Florida. 


Arseniuk, E., P.C. Czembor, and B.M. 

Cunfer. 1997. Segregation and 

recombination of PCR-based 

markers in progenies of in vitro 

mated isolates of Phaeosphaeria 

nodorum (Müller) Hedjaroude. 

Phytopathology 87 (Supplement) 

S5. 

Beck, J.J., and J.M. Ligon. 1995. 

Polymerase chain reaction assays 

for the detection of Stagonospora 

nodorum and Septoria tritici in 


Table 1. Comparison of Stagonospora nodorum isolates on cereal seedlings. 

Wheat Triticale Rye 

Isolates Alba Begra Liwilla Bogo Pinokio Zduno 

Sn26-1 4.1+1.63 6.2+1.70 1.8+0.70b 4.3+1.24 3.1+1.55 3.0+1.97f 

Sn48-1 2.2+1.00 4.3+1.46 2.1+0.96b 6.6+0.94 6.4+1.72 8.3+1.03 

9074 1.5+0.57 3.1+1.92a 1.0+0.56c 1.7+0.99d 1.8+0.73e 2.2+2.02f, g 

9076 2.1+0.52 2.9+0.92a 1.0+0.53c 1.4+0.57d 1.8+0.71e 2.0+1.80g 

The rating scale for fungal infection is from 1 (resistant) to 9 (susceptible).With T-test at the confidence 

level of 0.05, the pairs with the same letters are not significantly different. 




northern great plains. Plant Dis. 

81:1027-1031. 




Plant Dis. 81:1032-1036. 

Rohlf, F.J. 1990. Numerical Taxonomy 

and Multivariate Analysis System. 

Version 1.6. Exeter, Setauket, NY. 

Scharen, A.L., Z. Eyal, M.D. Huffman, 

and J.M. Prescott. 1985. The 

distribution and frequency of 

virulence genes in geographically 

separated populations of 

Leptosphaeria nodorum. 


Sprague, R. 1950. Diseases of cereals 

and grasses in North America. 

Ronald Press Co., New York. 

Ueng, P.P., G.C. Bergstrom, R.M. Slay, 

E.A. Geiger, G. Shaner, and A.L. 

Scharen. 1992. Restriction fragment 

length polymorphisms in the 

wheat glume blotch fungus, 

Phaeosphaeria nodorum. 


Ueng, P.P., K. Subramaniam, W. Chen, 

E. Arseniuk, L. Wang, A.M. 

Cheung, G.M. Hoffmann, and G.C. 

Bergstrom. 1998. Intraspecific 

genetic variation of Stagonospora 

avenae and its differentiation from 

S. nodorum. Mycol. Res. 102:607- 

614. 

White, T.J., T. Bruns, S. Lee, and J. 

Taylor. 1990. Amplification and 

direct sequencing of fungal 

ribosomal RNA genes for 

phylogenetics. PCR Protocols. 

Innis, M.A., D.H. Gelfand, J.J. 

Sninsky, and T.J. White (eds.). pp. 

315-322. 

Dice Similarity 

0.5 0.6 0.7 0.8 0.9 1.0 

8408 

9506-2 

9074 

9076 

Figure 1. UPGMA phenogram of four 

Stagonospora nodorum isolates based on the 

Dice Similarity Coefficients (Sd ) of 390 

individual AFLP DNA fragments.

A Vertically Resistant Wheat Selects for Specifically 

Adapted Mycosphaerella graminicola Strains 

C. Cowger, C.C. Mundt, and M.E. Hoffer 

Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA 

Abstract 

At its commercial release in Oregon, USA, in 1992, the winter bread wheat cultivar Gene was highly resistant to 

Mycosphaerella graminicola. Within just four years, that resistance had substantially disintegrated. In 1997, we collected 

M. graminicola isolates from experimental field plots of Gene and two other cultivars in Corvallis, Oregon, and in a 

greenhouse experiment inoculated seedlings of the same three cultivars with those isolates. Gene seedlings were resistant to all 

isolates derived from the other two cultivars, but were susceptible to six of seven isolates derived from Gene. A similar 

experiment using a small number of 1992 isolates from the same three cultivars had previously shown no isolates virulent on 

Gene, in keeping with other published data on Gene’s early resistance. Commercial cultivation of Gene, which increased to 

about 15% of the local wheat area during the period 1992-1995, appears to have selected for strains of M. graminicola 

adapted to specific virulence on Gene. Cultivar specificity is a feature of the M. graminicola-wheat pathosystem. 

The issue of whether M. 

graminicola is specific in its 

interactions with cultivars of a 

single wheat species (wheat or 

durum) has been widely debated. 

Recent studies (Ahmed et al., 1995; 

Ahmed, et al., 1996; Kema, et al., 

1996; Kema, et al., 1997) 

consistently indicate the existence 

of interactions between cultivars of 

a single species and isolates 

derived from that species. 

However, most experiments where 

interaction has been measured 

have utilized tester cultivars and 

isolates not originating on them. 

Such experiments can reveal only 

the potential for cultivar-specific 

adaptation. Here, we report the 

appearance of cultivar specificity 

when tester cultivars were 

challenged with isolates selected on 

those same cultivars in the field. 


We conducted two experiments 

involving the soft white winter 

wheat cultivars Gene (P.I. 560129), 

Madsen (P.I. 511673), and Stephens 

(C.I. 017596). Monopycnidial 

isolates of M. graminicola were 

obtained from Corvallis, Oregon, 

field plots of these cultivars in 1992 

and again in 1997. Greenhouse 

experiments were performed with 

these isolates in 1994 and 1998, 

respectively. We used two isolates 

derived from each cultivar in 1992, 

and seven or eight isolates from 

each cultivar in 1997. Seedlings of 

each cultivar were grown in pots in 

the greenhouse, and each tester pot 

was inoculated at 21 days with an 

individual isolate in a factorial 

design. Both experiments were 

replicated four times. The percent 

of leaf area covered by lesions was 

assessed at 21 days after 

inoculation. Data were log e - 

transformed and subjected to 

analysis of variance. 

Results 

Of the six 1992 isolates tested, 

including two from Gene, none 

was virulent to Gene (data not 

shown). By contrast, the 1997 

isolates derived from Gene were 

generally virulent to Gene, while 

85 

the 1997 isolates derived from the 

other two cultivars were avirulent 

to Gene (Table 1). Analysis of 

variance showed no significant 

cultivar-of-origin x tester 

interaction for the 1992 isolates, and 

a significant cultivar-of-origin x 

tester interaction for the 1997 

isolates (not shown). Linear 

contrasts (not shown) were used to 

dissect the cultivar-of-origin x tester 

interaction, and they revealed a 

highly significant interactive effect 

of the tester Gene vs. testers 

Madsen and Stephens (P = 0.0068). 

Discussion 

From its release in 1992, Gene 

expanded to occupy 15% of the 

Willamette Valley wheat area by 

1995, but then declined (Figure 1) 

as its resistance to M. graminicola 

broke down (and incidence of 

septoria nodorum blotch, to which 

Gene was always susceptible, 

increased).

86 

Session 4 — C. Cowger, C.C. Mundt, and M.E. Hoffer 

Our first greenhouse 

experiment used only six isolates, 

but it supports published field data 

on Gene’s resistance during the 

years leading up to its release in 

1992 (Ahmed et al., 1995; Mundt et 

al., 1999). Our data suggest that 

cultivar specificity can develop in 

the M. graminicola-wheat 

pathosystem, and that this 

pathogen is capable of rapidly 

adapting to qualitative host 

resistance. Past observations 

suggested that resistance to M. 

graminicola does not break down 

rapidly or completely (Johnson, 

1992; Kema et al., 1996). However, 

the resistance of Gene succumbed 

within less than five years. We 

believe that Gene’s resistance is 

probably under monogenic or 

oligogenic control, and is perhaps 

due to the Stb4 gene (Kronstad et 

al., 1994). Further, M. graminicola 

strains able to defeat Gene’s 

vertical resistance appear to persist 

in the local population despite the 

limited continuing commercial 

production of Gene. 

References 





and wheat cultivars. Plant Pathol. 

44:838-847. 

Table 1. Percent diseased leaf area of greenhouse-grown wheat seedlings inoculated with 

Mycosphaerella graminicola isolates collected in 1997. a 

Cultivar of origin Tester cultivar 

& isolate nbr. Gene Madsen Stephens Mean 

Gene 

1 19.9 26.4 9.4 18.6 

2 3.4 18.5 16.7 12.8 

3 13.0 29.5 23.4 21.9 

4 11.2 17.9 29.6 19.5 

5 43.6 63.4 63.4 56.8 

6 21.1 32.9 33.0 29.0 

7 37.2 61.3 56.6 51.7 

Meanb 21.3ac Madsen 

35.7a 33.1a 30.1a 

8 0.9 77.1 56.0 44.7 

9 3.0 7.4 11.5 7.3 

10 4.2 30.6 28.4 21.0 

11 10.7 38.0 31.5 26.8 

12 1.0 30.1 28.7 19.9 

13 1.3 30.1 22.6 18.0 

14 0.2 19.6 7.8 9.2 

15 0.7 15.1 13.4 9.8 

Mean 

Stephens 

2.8b 31.0a 25.0a 19.6b 

16 3.3 22.7 24.7 16.9 

17 1.0 13.2 7.9 7.4 

18 0.4 31.0 21.7 17.7 

19 2.5 31.4 24.9 19.6 

20 2.7 22.0 16.1 13.6 

21 0.7 15.5 14.3 10.2 

22 2.2 36.1 28.3 22.2 

Mean 1.8b 24.6a 19.7a 15.4b 

Grand mean 8.4 30.5 25.9 21.6 

a Experiment conducted in 1998. 

b Means are the untransformed percent diseased leaf area over four replications. Statistical analyses 

c 

were conducted on loge-transformed data. 

Within a column, means followed by the same letter are not significantly different at the 95% 

confidence level based on Fisher’s protected least significant difference. 









future opportunities in breeding for 

disease resistance, with examples 

from wheat. Euphytica 63:3-22. 


J.G., and van Silfhout, C.H. 1996. 












pathosystem. III. Comparative 



87:266-272. 

Kronstad, W.E., Kolding, M.F., Zwer, 

P.K., and Karow, R.S. 1994. 

Registration of ‘Gene’ wheat. Crop 

Sci. 34:538. 

Mundt, C.C., Hoffer, M.E., Ahmed, 

H.U., Coakley, S.M., DiLeone, J.A., 

and Cowger, C.C. 1999. Population 

genetics and host resistance. Pages 

115-130 in: Septoria on Cereals: A 

Study of Pathosystems. J.A. Lucas, 

P. Bowyer, and A.M. Anderson, eds. 

CAB International, Wallingford, 

United Kingdom. 

Percent of valley wheat area 

70 

60 

50 

40 

30 

20 

10 

Gene 

Madsen 

Stephens 

0 

1990 91 92 93 94 95 96 97 

Figure 1. Percent of soft white winter wheat 

area occupied by three cultivars in the 

Willamette Valley of Oregon during the period 

1990-97.

Genetic Variability in a Collection of Stagonospora 

nodorum Isolates from Western Australia 

N.E.A. Murphy, 1 R. Loughman, 2 E.S. Lagudah, 3 R. Appels, 3 and M.G.K. Jones1 1 WA State Agriculture Biotechnology Centre, Division of Science and Engineering, Murdoch University, 


2 Agriculture Western Australia, Western Australia 


Abstract 

Stagonospora nodorum isolates were collected from the Western Australian cereal-belt during 1993. These isolates 

and a subset of isolates taken from a single location were used to assay the level of variation within the pathogen 

population. The isolates were compared using anonymous nuclear DNA markers. Three low copy number and a single 

high copy number probe were used to generate restriction fragment length polymorphisms (RFLPs). The collection 

exhibited a high genotypic diversity for the high copy number probe. This is consistent with the high level of sexual 

reproduction previously found in the fungal population. Only minor differences between the total collection of isolates 

and the subset of isolates taken from the single location were found. 

Septoria nodorum blotch is one 

of the most important leaf diseases 

of wheat (Triticum aestivum L.) in the 

Western Australian cereal-belt 

(Murray and Brown, 1987). It is 

caused by Stagonospora nodorum 

(Berk.) Castellani & E. Germano 


(E.Muller) Hedjaroude). Previous 

work on the variability of S. nodorum 

has been conducted principally on 

phenotypic traits such as 

aggressiveness (Allingham and 

Jackson, 1981) and culture color 

(Scharen and Krupinsky, 1970). 

These studies have shown that there 

is considerable variation between 

isolates collected within relatively 

small distances (Allingham et al., 

1981). More recently studies have 

assayed the genotypic variability 

using molecular techniques. 

RFLPs were used to look at two 

populations of S. nodorum in the USA 

using a hierarchical system of 

sampling (McDonald et al., 1994). 

Considerable genetic variation was 

found to occur on a relatively small 

scale. The same set of eight probes 

were used to study a population of 

S. nodorum isolates gathered in 

Switzerland and two populations 

from the USA using a similar 

hierarchical sampling system. The 

Swiss population was genetically 

similar to the populations from the 

USA, providing evidence for gene 

flow between the populations (Keller 

et al., 1997a) and the gene diversity 

for four of the seven RFLP loci tested 

was not significantly different 

between the populations (Keller et 

al., 1997a). 

The aim of this investigation was 

to examine the level of genetic 

diversity among a collection of 

Western Australian S. nodorum 

isolates using RFLPs and to compare 

the results obtained with similar 

work done in other regions of the 

world. 


A total of 118 isolates from 38 

locations were used in the study. 

Thirty-nine of the isolates were 

obtained from an existing collection. 

Of these 39 historical isolates, 26 

87 

were from a single site at 

Badgingarra Research Station, 

recognized as an area where high 

levels of disease severity could be 

expected. These isolates were 

captured as single ascospores in 

spore traps during 1991. The 

remaining 79 isolates were collected 

from 26 locations throughout the 

cereal belt in 1993. They were 

isolated as ascospores from wheat 

stubble remaining from the 1992 

crop. 

The cultures of S. nodorum were 

revived on wheat meal agar plates to 

confirm their identity through 

pycnidiospore production. Mycelia 

was cultured in liquid broth and the 

DNA extracted (Lagudah et al., 1991). 

The genomic DNA was digested 

with HindIII and run on an agarose 

gel. A capillary alkali method was 

used to transfer the DNA onto the 

membrane. Three low copy number 

probes (pASN15, pASN125 and 

pJSN73) were used to produce a 

multilocus haplotype, and a single 

high copy number probe (pSNS4) 

was used to generate a fingerprint for

88 

each isolate. Two of the probes used 

were from the genomic library of a 

Western Australian isolate of S. 

nodorum (pASN15 and pASN125) 

and the remaining two probes were a 

gift from Bruce McDonald of Texas 

A&M University (pJSN73, pSNS4). 

Both genomic libraries were set up 

by the restriction of genomic DNA 

from a S. nodorum isolate using PstI. 

Each probe was labelled with alpha 

32 P. Hybridization was carried out 

for a minimum of 12 hours. The 

membranes were washed and placed 

on x-ray film for up to 14 days. 

Each probe was assumed to 

represent a single RFLP locus and 

each restriction fragment length 

variant were treated as an allele 

(McDonald et al., 1994). Each allele 

for each RFLP locus was designated 

an arbitrary number. The high copy 

number probe (pSNS4) was used to 

identify clones within the same 

multilocus haplotype (McDonald et 

al., 1994). The subset of the isolates 

from Badgingarra was treated as a 

separate collection to determine if 

the same level of genetic diversity 

present in the total collection was 

also present at a single location. The 

allelic frequencies, Nei’s measure of 

gene diversity (Nei, 1973), the 

genotypic diversity, and the gametic 

disequilibrium were all calculated as 

described in McDonald et al. (1994). 

Results 

There were two alleles for probes 

pASN125 and pJSN73 and four for 

probe pASN15. Only four S. nodorum 

isolates had the same DNA 

fingerprint using the high copy 

number probe pSNS4. Nei’s measure 

of gene diversity was 0.23 for 

pJSN73-HindIII, 0.50 for pASN15- 

HindIII and 0.56 for pASN15-HindIII. 

The average over all three loci was 

0.43 in the clone-corrected data. For 

the Badgingarra subset no clones of 

S. nodorum were identified. The 

allelic frequencies were very similar 

for the three loci compared with the 

total population (being 0.27, 0.49, 

and 0.60, respectively) and Nei’s 

measure of gene diversity averaged 

0.45 over the three loci. 

For the clone-corrected data of 

the total population, 25% of the 

allele pairs were in significant 

gametic disequilibrium (Table 1). 

When all of the alleles were added 

together for each locus pair in the 

clone-corrected data, one of the 

locus pairs was in significant 

gametic disequilibrium (Table 1). In 

the Badgingarra subset, 20% of all 

the allelic combinations had a 

significant disequilibrium 

coefficient, and for each locus pair, 

one pair were in significant gametic 

disequilibrium (Table 1). 

There were 100 different 

fingerprint haplotypes produced 

from 103 isolates, giving a genotypic 

diversity of 92.2, 90% of its 

maximum value. In the subset 

collection from Badgingarra, the 

genotypic diversity was 15, 100% of 

its maximum value. 

Table 1. Gametic disequilibrium for the clonecorrected 

data of the total population and the 

Badgingarra subset for each of pair of alleles 

between each pair of loci and for each pair of loci. 

Probe pASN15 pJSN73 pASN125 

pASN15 4/8 0/8 

15.7** (3) 7.15 (3) 

pJSN73 0/8 1,2 1/4 

2.05 (3) 3.70 (1) 

pASN125 3/8 0/4 

9.62 (3) 1.71 (1) 

1 Clone-corrected data only; values above the 

diagonal are for the total population and values 

below the diagonal are for the Badgingarra subset. 

2 For each set of comparisons, the first line shows the 

number of allele pairs that are in significant gametic 

disequilibrium (p

ecombination plays in the 

population dynamics. This level of 

variation may have implications for 

the cereal plant breeding and 

selection program if it is a reflection 

of the potential variability for 

aggressiveness in the pathogen. If 

the level of genotypic variation does 

reflect the level of variation in 

aggressiveness, selecting resistance 

using the widest possible range of S. 

nodorum isolates would be desirable. 

The most practical method to 

screen breeding lines for a wide 

selection of S. nodorum isolates is to 

use straw from previously infected 

wheat as a source of inoculum 

(Holmes and Colhoun, 1975). 

Previous work investigating the 

effect of the host genotype upon the 

selection of S. nodorum provided no 

evidence of specialization of the 

pathogen with the host cultivar 

(Keller et al., 1997b) according to 

neutral RFLP markers. It would also 

be unnecessary to use straw from 

numerous sites, as the genotypic 

variation encountered at a single site 

can account for as much as 95% of 

the total genotypic variation within a 

population (Keller et al., 1997b). 

Using straw from a collection of 

cultivars and from a number of sites 

may be unnecessary, as it would 

provide only a modest increase in 

the overall genotypic diversity. 

References 

Allingham, E.A., and L.F. Jackson. 1981. 

Variation in pathogenicity, virulence 

and aggressiveness of Septoria 

nodorum in Florida. Phytopathology 

71:1080-1085. 

Bathgate, J.A., and R. Loughman. 1995. 

Ascospores as primary inoculum of 

Phaeosphaeria spp. in Western 

Australia. 10th Biennial Australasian 

Plant Pathology Society Conference. 

New Zealand, Lincoln University, 

28-30th August. p. 100. 

Holmes, S.J.I., and J. Colhoun. 1975. 

Straw-borne inoculum of Septoria 

nodorum and Septoria tritici in 

relation to incidence of disease on 

wheat plants. Plant Pathology 24:63- 

66. 

Keller, S.M., J.M. McDermott, R.E. 

Pettway, M.S. Wolfe, and B.A. 

McDonald. 1997a. Gene flow and 

sexual reproduction in the wheat 

glume blotch pathogen Phaesophaeria 

nodorum (anamorph Stagonosopora 

nodorum). Phytopathology 87:353- 

358. 

89 

Keller, S.M., M.S. Wolfe, J.M. 

McDermott, and B.A. McDonald. 

1997b. High genetic similarity 

among populations of Phaeosphaeria 

nodorum across wheat cultivars and 

regions in Switzerland. 


Lagudah, E.S., R. Appels, and D. 

McNeil. 1991. The Nor-D3 locus of 

Triticum tauschii: natural variation 

and genetic linkage to markers in 

chromosome 5. Genome 34:387-395. 

McDonald, B.A., J. Miles, L.R. Nelson, 

and R.E. Pettway. 1994. Genetic 




255. 

Murray, G.M., and J.F. Brown. 1987. 

The incidence and relative 

importance of wheat diseases in 

Australia. Australasian Plant 


Nei, M. 1973. Analysis of gene diversity 

in subdivided populations. 

Proceedings of the National 

Academy of Science, USA 70:3321- 

3323. 


1970. Cultural and Inoculation 

studies of Septoria nodorum cause of 

glume blotch of wheat. 


90 

Mating Type-Specific PCR Primers for Stagonospora 

nodorum Field Studies 

Bennett, R.S., 1 S.-H. Yun, 1 T.Y. Lee, 1 B.G. Turgeon, 1 B. Cunfer, 2 

E. Arseniuk, 3 and G.C. Bergstrom 1 * (Poster) 

1 Department of Plant Pathology, Cornell University, Ithaca, NY, USA 

2 Department of Plant Pathology, University of Georgia, Griffin, GA, USA 

3 Plant Breeding and Acclimatization Institute, Radzików, Poland 

* corresponding author 

Abstract 

Conserved regions of the mating type genes (MAT) in Cochliobolus heterostrophus, Mycosphaerella zeaemaydis, 

and Alternaria alternata were used to design primers to identify the mating type genes and thus assign 

mating types to Stagonospora nodorum. These primers successfully distinguished between mating types of S. 

nodorum isolates that had been identified through traditional crosses. The primers were used to screen a small sample of 

S. nodorum isolates from New York, thus revealing the presence of both mating types. This efficient method of 

identifying mating types may help determine the role of sexual recombination in the epidemiology of S. nodorum, as 

well as elucidate phylogenetic relationships among related species. 



(teleomorph = Phaeosphaeria 

nodorum (E. Müller) Hedjaroude) is 

the causal agent of stagonospora 

nodorum blotch, a major disease of 

wheat around the world. 

Phaeosphaeria nodorum is 

heterothallic and thus requires 

strains of the two different mating 

types to produce ascospores 

(Müller, 1989). The potential 

significance of sexual reproduction 

in the epidemiology of 

stagonospora nodorum blotch has 

been heightened by the high RFLP 

variability found among field 

isolates (McDonald et al., 1994). 

Fungi that regularly reproduce 

sexually have more opportunities 

to develop fungicide resistance and 

to overcome cultivar resistance. 

Furthermore, airborne ascospores 

would permit dissemination over 

longer distances than splashdispersed 

conidia. 

MAT genes have been identified 

for several species of 

Loculoascomycetes including 

Setosphaeria turcica, Mycosphaerella 

zeae-maydis, Alternaria alternata, and 

several Cochliobolus spp. (Arie et al., 

1997). Both genes, MAT-1 and MAT- 

2, contain conserved regions that 

allow the relatively rapid 

identification of these genes from an 

increasing group of ascomycetes. A 

high mobility group (HMG) and abox 

motif are the conserved regions 

in MAT-2 and MAT-1, respectively 

(Turgeon, 1998). These sequences, 

besides elucidating sexual 

mechanisms and phylogeny, may 

also help address epidemiological 

questions. 

We have developed primers to 

identify the mating types of P. 

nodorum from the conserved MAT 

regions of related fungi. Preliminary 

data on the mating type prevalence 

in a small sample of New York field 

isolates is also presented. 


Fungal isolates and media 

Three S. nodorum isolates of 

different mating types (two (-) 

(SN435PL-98, SN437GA-98) and 

one (+) (SN436GA-98)) (Arseniuk 

et al., 1997a,b) were grown on V-8 

juice agar (200 ml V8 juice, 3 g 

CaCO3 , 15 g agar per 800 ml of 

distilled water). After 

approximately seven days, mycelial 

plugs were taken and placed into 

yeast-malt-sucrose broth (5 g yeast 

extract, 5 g malt extract, 20 g 

sucrose per 1 liter of distilled 

water), and placed on a shaker (150 

rpm) at room temperature. Mycelia 

were harvested after 5-7 days by 

filtering through 3-ply sterile 

cheesecloth lining a Buchner funnel 

and were rinsed with distilled 

water. The samples were then 

frozen and lyophilized overnight. 

MAT-1 and MAT-2 C. heterostrophus 

laboratory strains (C5 and C4, 

respectively) were used as controls.

Thirty-eight arbitrarily chosen 

field isolates of S. nodorum collected 

from New York in different places 

and years were grown on 

cellophane discs overlaid on V-8 

juice agar. After approximately 

seven days, mycelia were scraped 

off the cellophane and placed in 

microcentrifuge tubes to be 

lyophilized. 

DNA extraction 

Lyophilized mycelia were 

ground in liquid nitrogen. The field 

isolates were ground directly in 

microcentrifuge tubes with a small 

amount of white quartz sand (-50 + 

70 mesh, Sigma Chemical 

Company, St. Louis, MO). DNA 

was extracted by a miniprep 

procedure (Wirsel et al., 1996). 

Amplification of the HMG 

and a-boxes by PCR 

PCR primers (Sn-HMG1 and 

Sn-HMG2) for the HMG box (Table 

1) were designed from conserved 

regions in the HMG box of the MAT 

gene of Cochliobolus heterostrophus, 

M. zeae-maydis, and A. alternata, 

whereas the primers (Sn-ab1 and 

Sn-ab2) for the a-box were designed 

from the a-boxes of M. zeae-maydis 

and A. alternata. The primers were 

synthesized by the Cornell 

University DNA Services Facility 

and were dissolved (100 µM) in 

Table 1. PCR primers used to amplify 

fragments of MAT genes in Stagonospora 

nodorum. 

MAT-1 

Sn-ab1 5’ AA(A/G)GCN(C/T)TNAA(C/ 

T)GCNTT (C/T)GTNGG 3’ 

Sn-ab2 5’ TC(C/T)TTNCC(A/G/T)AT(C/T) 

TG(A/G)TCNCG(A/G/T)AT 3’ 

MAT-2 

Sn-HMG1 5’ AA(A/G)GCNCCN(AC) 

GNCCNATGAA 3’ 

Sn-HMG2 5’ TT(C/T)TT(C/T)TT(C/T)T(CG) 

NCCNGG(C/T)TT 3’ 

sterile distilled water and stored at 

–20C. Each PCR reaction mixture 

had approximately 20 ng of 

genomic DNA in 50 µl reaction 

buffer [1X PCR Buffer (Perkin 

Elmer, Norwalk, CT), 0.2 mM 

dNTPs, 2.5 mM MgCl2, , 2 µM each 

primer, and 0.025 U Taq 

polymerase]. The samples were 

denatured at 95C for 2 min, and 

then subjected to 30 cycles of 95C 

for 1 min, 50C for 30 sec, and 72C 

for 1.5 min. After extension at 72C 

for 10 min, the samples were kept 

at 4C. 5 µl aliquots of the PCR 

products were analyzed on a 2% 

agarose gel in TAE buffer. 

Cloning, sequencing, and 

analysis of PCR products 

The MAT sequences from 

related fungi predicted that a PCR 

product of ~270 bp for the HMG 

box and a product of ~230 bp for 

the a-boxes would result if the 

amplifications were successful. 

Products of these sizes were cloned 

from the PCR reaction into the 

vector pCR2.1, using the guidelines 

Mating Type-Specific PCR Primers for Stagonospora nodorum Field Studies 91 

of the manufacturer (Invitrogen 

Co., San Diego, CA). DNA 

sequences were determined at the 

Cornell University DNA Services 

Facility. Sequences were aligned 

with the LaserGene program 

MegAlign (DNASTAR Inc., 

Madison, WI), using the clustal 

method. A BLAST search was done 

using the NCBI/Genbank internet 

databases. 

Gel blot hybridization 

A standard DNA gel blot 

hybridization procedure was 

followed (Sambrook et al., 1989). 

Results 

HMG alpha 

The primers for the HMG box 

were used with genomic DNA of 

(+) and (-) S. nodorum strains as 

templates. A PCR product 

approximately 0.3 kb, matching the 

~270 bp predicted, was present in 

the (+) (MAT-2) strain, but was not 

present in the (-) (MAT-1) strains 

(Figure 1). The primers for the abox, 

however, amplified the 

1 2 3 4 5 6 7 8 9 101112131415161718 

Figure 1. PCR products amplified with the HMG and a-box primers. Lanes 2-9 were amplified using 

HMG (MAT-2) primers, and lanes 10-17 were amplified with a-box (MAT-1) primers. Lanes 2,10 and 

3,11: C. heterostrophus C5 (MAT-1) and C. heterostrophus C4 (MAT-2), respectively; lanes 4,12 and 

5,13: plasmid with cloned a-box from SN435PL-98 and plasmid with cloned HMG box from SN436GA- 

98, respectively; lanes 6 and 14: SN436GA-98; lanes 7 and 15: SN437GA-98; lanes 8 and 16: SN005NY- 

85; lanes 9 and 17: SN197NY-88. A ~0.3-kb band (arrowhead) was amplified in the MAT-2 isolates 

only, and a band above 0.2-kb (asterisk) was amplified only in the MAT-1 isolates.

92 

Session 4 — Bennett, R.S., S.-H. Yun, T.Y. Lee, B.G. Turgeon, B. Cunfer, E. Arseniuk, and G.C. Bergstrom 

expected product (~230 bp) from 

only the (-) (MAT-1) strains. The 

primers were also able to 

distinguish between the MAT-1 and 

MAT-2 C. heterostrophus controls. 

The BLAST search of the S. 

nodorum cloned products showed 

highest homology to the MAT 

genes of Cochliobolus spp. 

In gel blot hybridization, a 

single band was obtained from 

DNA of the (+) SN436GA-98 isolate 

only when probed with the HMG 

box; no hybridization occurred on 

the (-) SN435PL-98 isolate. 

Likewise, a single band was 

obtained when SN435PL-98 was 

probed with the a-box, and no 

hybridization occurred to the DNA 

of SN436GA-98. 

When these primers were used 

to test the 38 field isolates, 20 were 

shown to be of the MAT-1 mating 

type and 18 were of the MAT-2 

mating type. 

Discussion 

A PCR technique that readily 

identifies the mating type can be a 

useful tool for studying S. nodorum. 

Surveying for the distribution of 

mating types in the field may result 

in a better understanding of the 

role of sexual reproduction in the 

disease cycle. The preliminary data 

given here tested S. nodorum 

isolates that were collected in New 

York wheat fields between 1985 

and 1995. These isolates are not 

only temporally random, but 

spatially unrelated. More 

informative surveys of spatially 

distributed isolates from single 

fields are being conducted. 

However, the preliminary data 

presented here do indicate that 

both mating types exist in New 

York and that sexual recombination 

is possible. 

Mating types may also serve as 

an additional marker for 

experiments requiring genetically 

characterized isolates. As 

previously established (Arie et 

al,.1997), we refer to (-) isolates 

containing the a-box as MAT-1, and 

(+) isolates containing the HMG 

box as MAT-2. Finally, as outlined 

in a review by Turgeon (1998), MAT 

gene sequences may provide 

valuable information for 

phylogenetic analyses, particularly 

of related species, the study of 

pathogenesis, and the underlying 

mechanisms of reproductive life 

styles in fungi. 

References 

Arie, T., S.K. Christiansen, O.C. Yoder, 

and B.G. Turgeon. 1997. Efficient 

cloning of ascomycete mating type 

genes by PCR amplification of the 

conserved MAT HMG box. Fungal 

Genetics and Biology 21:118-130. 

Arseniuk, E., B.M. Cunfer, S. Mitchell, 

and S. Kresovich. 1997a. 

Characterization of genetic 

similarities among isolates of 

Stagonospora spp. and Septoria tritici 

by amplified fragment length 

polymorphism analysis. 

Phytopathology 87 (Supplement) S5. 

Arseniuk, E., P.C. Czembor, and B.M. 

Cunfer. 1997b. Segregation and 

recombination of PCR-based 

markers inprogenies of in vitro 

mated isolates of Phaeosphaeria 

nodorum (Müller) Hedjaroude. 

Phytopathology 87(Supplement), S5 

. 

McDonald, B.A., J. Miles, L.R. Nelson, 

and R.E. Pettway. 1994. Genetic 




255. 

Müller, E. 1989. On the taxonomic 

position of Septoria nodorum and 

Septoria tritici, p. 11-12. In: 

Proceedings from the Third 

International Workshop on Septoria 

Diseases of Cereals. Zurich, 

Switzerland. 

Sambrook, J., E.F. Fritsch, and T. 

Maniatis. 1989. Molecular Cloning: 

A Laboratory Manual, 2 nd ed. Cold 

Spring Harbor Laboratory Press: 

Cold Spring Harbor, NY. 

Turgeon, B.G. 1998. Application of 

mating type gene technology to 

problems in fungal biology. Annual 

Review of Phytopathology 36:115- 

137. 

Wirsel, S., B.G. Turgeon, and O.C. 

Yoder. 1996. Deletion of the 

Cochliobolus heterostrophus mating 

type (MAT) locus promotes function 

of MAT transgenes. Current 

Genetics 29:241-249.

Session 5: Epidemiology 

Epidemiology of Mycosphaerella graminicola and 

Phaeosphaeria nodorum: An Overview 

M.W. Shaw 

Department of Agricultural Botany, School of Plant Sciences, The University of Reading, Reading, England 

Abstract 

The within-season and between-crop methods of multiplication and survival, and their environmental relations are 

reviewed. Mycosphaerella graminicola multiplies within a season by conidia which are primarily but not exclusively 

dispersed by rain. Arguments are given that the influence of ascospores within a crop will be minor, but they are the 

major source of movement of the pathogen into new crops. Phaeosphaeria nodorum also multiplies within a season by 

conidia, but has clearer associations with wet weather. The role of ascospores in movement between crops may vary 

geographically; seed transmission seems to be very important in some areas. 

In this contribution, I have tried 

to summarize what is understood 

of the epidemiology of these two 

diseases. My aim has been to 

produce a concise summary to 

introduce the detailed and novel 

contributions that follow. I have 

tried to give slightly more extended 

discussion of those areas where 

new ideas have arisen or our 

understanding has changed 

substantially in the last few years. 

The relevant questions for both 

diseases fall into two classes. First, 

qualitative: what conditions allow 

inoculum transfer, permit infection, 

and encourage sporulation? 

Second: quantitative: in a given 

agro-ecosystem, what factors in 

practice regulate pathogen 

population size? The two questions 

are related, but both need to be 

answered if the diseases are to be 

managed most effectively. The 

answers also depend greatly on 

scale: within a region and over 

several years, very different 

processes and factors may need to 

be considered from those operating 

within a crop and within a season. 

The paper is restricted to wheat. 

Mycosphaerella 

graminicola 

Within a crop 

As discussed later, infection of a 

crop is usually initiated by airborne 

ascospores (Shaw and Royle, 1989). 

The density of initial infections is 

such that once a few sporulating 

lesions per square meter exist, a 

polycyclic epidemic on successive 

leaf layers follows (Shaw and 

Royle, 1993). Pycnidia are produced 

within roughly 14 to 40 days, 

depending on both temperature 

and host cultivar. Conidia may be 

dispersed by single rain splashes 

within a circle of about 1 m radius, 

the number dispersed decreasing 

exponentially with distance, with 

half distances of the order of 10 cm 

(Bannon and Cooke, 1998; Brennan 

et al., 1985a; Brennan et al., 1985b). 

Initial dispersal is to the ground or 

to surface water on a leaf, whence 

further dispersal is possible. 

However, spores contacting leaf 

surfaces are bound to the surface 

within a short time. The average 

number of splashes moving a spore 

during rain of given intensity and 

duration is hard to estimate, but is 

93 

unlikely to be large, so half 

distances for effective horizontal 

dispersal will be of the order of 20- 

50 cm at most. Each initial infection 

may plausibly produce 50,000 to 

500,000 conidia (10-100 pycnidia of 

ca. 5000 spores) (Eyal, 1971). 

Although most of these are not 

dispersed far, considering them as 

evenly dispersed over a circle of 0.5 

m radius gives 5-50 spores per 

square centimeter from initial 

infections spaced at about 1/m 2 . If 

they had 2-20% infection efficiency, 

the crop would be saturated with 

latent lesions. Fortunately, infection 

efficiency is usually lower than this, 

but if few spores are present, 1% of 

those applied may cause infection 

under good infection conditions. 

The actual environmental 

conditions permitting infection are 

lax because the pathogen tolerates 

extended breaks in humidity 

during the infection process (Shaw, 

1991a; Shaw and Royle, 1993). 

Certainly, within two infection 

cycles the pathogen population in 

crops with moderate initial 

amounts of disease will be limited 

by the rate of growth of leaf area

94 

Session 5 — M.W. Shaw 

and the favorability of the 

environment rather than by 

shortage of inoculum. However, 

spread by splash is very inefficient 

over other than short distances, and 

if initial infections are widely 

spaced, then the disease should 

remain patchy and therefore cause 

limited damage. 

The preceding paragraph 

ignored vertical spread, which has 

been argued to be the key factor 

determining severe disease on the 

uppermost leaf layers of a wheat 

crop. Vertical movement of splash 

droplets is limited, declining 

exponentially with typical halfdistances 

of 5 cm, but varies 

between storms (Bannon and 

Cooke, 1998; Shaw, 1987; Shaw, 

1991b). Probably more critically, the 

distance between leaf layers with 

and without infection varies greatly 

according to both the architecture 

of the wheat cultivar and the latent 

period of the pathogen on the 

cultivar. Lovell et al. (1997) have 

shown how the interaction of these 

causes great variation in the 

potential for spread of pathogen to 

the upper part of the crop, where it 

becomes damaging. 

Once a few sporulating lesions 

are present on a reasonable 

proportion of the uppermost leaves 

of a wheat crop, there is potential 

for multiplication leading to 

widespread infection and 

premature leaf death, except in very 

dry weather. 

The major advance since the last 

Workshop is the recognition that 

pseudothecia are produced 

regularly throughout the year 

under at least some conditions on 

at least some cultivars (Hunter et 

al., 1999; Kema et al., 1996). This 

means that sparse initial infections 

could spread much more effectively 

by windblown ascospores, and that 

multiplication of the disease could 

take place efficiently in the absence 

of rain, dew alone providing 

wetness for infection by dry 

dispersed spores. This is a 

potentially dramatic change to our 

view of the ecology of the organism. 

However, the effect on epidemics 

within a season is probably limited, 

because the pseudothecia are 

always produced long after 

pycnidia. Two extreme situations 

can be imagined: one in which 

pycnidia can infect often during the 

season, one in which they can never 

infect. 

In the first situation, even in the 

fastest quoted latent periods for 

perithecia, the effect on the 

epidemic rate of ascospore 

production is equivalent to perhaps 

1000-10,000 extra spores from a 

single infection, produced at 

roughly the time when the next 

generation of lesions from the 

pycnidia produced earlier are 

themselves producing pycnidia. If 

the multiplication ratio of lesions 

from one generation to the next is R, 

then the pycnidial route is 

producing of the order of R * 10,000 

conidia in the time during which 

the sexual route is producing 10,000 

spores: a ratio of 1:R. Order of 

magnitude estimates of R can be 

obtained in at least two ways. First, 

the ratio between the number of 

lesions a latent period after disease 

first entered a crop and the initial 

number of lesions. For the crops 

observed by Shaw and Royle (1989) 

this ratio was about 100. Second, the 

ratio between the initial number of 

lesions on the uppermost leaves of a 

crop, and the number one latent 

period later (Shaw and Royle 1993): 

this too suggests a large number. 

The effect on the epidemic rate 

must be very small. This is borne 

out by detailed modelling (Eriksen 

et al., in prep.). 

In the second situation, 

pseudothecia are the only route by 

which infection can progress. In 

this case, the latent period is at least 

double the latent period for an 

epidemic otherwise similar but 

driven by pycnidia. Since the latent 

period is at least doubled, and any 

gains in infection or dispersal 

efficiency are offset by the reduced 

number of ascospores produced, 

the rate of the epidemic is at least 

halved. A rather more qualitative 

prediction would be that where 

conditions prevent conidial 

dispersal, epidemics will develop 

very slowly, and be damaging only 

where initial disease is rather 

widespread. It will clearly be very 

interesting to study epidemic 

progress in areas where pycnidial 

progression is not possible, and see 

whether this prediction is true. 

In fact, even this may overstate 

the case, since the fungus is 

heterothallic (Kema et al., 1996) and 

presumably therefore requires two 

infections of opposite mating type 

to be adjacent in order to produce 

ascospores. It is not known how 

close together infections must be to 

mate effectively. Metcalfe (1999) 

found internal hyphae spanning an 

average maximum of 11 mm in a 

susceptible wheat cultivar just 

before pycnidia were produced, so 

infections more than 20 mm apart 

may be isolated. In a sparse, slow 

epidemic this may be rare. Mating 

will be commonest in situations 

where inoculum is not limiting the 

pathogen population in any way, 

but in these cases, the extra 

inoculum provided by ascospores 

will not affect epidemic rate.

When inoculum is common low 

in the canopy, but transport is 

potentially limiting infection of 

upper leaves, ascospores could 

profoundly alter the risk of severe 

infection on the uppermost leaves, 

because rainfall is not required for 

their movement to these leaves. 

However, recent work confirms 

(under UK conditions at least) the 

apparent association of severe M. 

graminicola with rain (Lovell et al., 

1997); and windblown transport of 

spores from close to the ground to 

the upper leaves of a dense canopy 

is not efficient because windspeeds 

are not high within the canopy. 

Nonetheless, the simple picture of 

rain moving spores from the base of 

the canopy onto the upper leaves as 

the only risk factor requires 

modification and may well be 

misleading under some 

circumstances. 

Interactions between genetics 

and ecology are of interest, and 

could complicate the population 

dynamics of the pathogen 

considerably, at worst rendering 

forecasts almost impossible. The 

fittest isolate on a given cultivar can 

vary with temperature (B. al- 

Hamar, University of Reading, 

personal communication). This 

means that equivalent sized 

populations could have 

intrinsically different growth-rates 

according to the combination of 

weather conditions which gave rise 

to them, so that identical 

environmental conditions and 

initial population sizes would give 

rise to different population 

responses. 

Between crops 

Windblown ascospores appear 

to be the main mechanism by 

which M. graminicola moves 

between crops, both from one 

Epidemiology of Mycosphaerella graminicola and Phaeosphaeria nodorum: An Overview 95 

season to the next and within a 

season. However, there is little 

documentation of the relative 

importance of local debris and 

widely dispersed, generalized 

sources of inoculum for new crops. 

In northern Europe, with most 

wheat grown in rotation and with 

full tillage, the generalized air 

spora appear to dominate sources. 

However, this situation must differ 

in different farming systems. Where 

wheat is a scarcer crop, the 

generalized concentration of 

ascospores in the air must be lower, 

and where no-till and continuous 

cropping is common but the wheat 

fields are scattered, one would 

expect local sources to dominate. 

There is relatively little evidence 

published about this outside 

Europe and northern America. A 

curious feature of the disease in, for 

example, the UK seems to be that 

the extremely efficient control of 

the pathogen achieved on the 

upper part of the plant by fungicide 

does not appear to have reduced 

the ability of the fungus to produce 

ascospores and infect subsequent 

crops. This could have two 

explanations: 1) in stubbles, 

ascospores are produced as much 

on the lower parts of plants, never 

managed by fungicide, as on the 

upper parts; or 2) the dominant 

triazole fungicides act only as 

fungistats and after the death of 

leaves, fungal development and the 

production of pseudothecia can 

continue as if the treatment had 

never taken place. Genetic and 

physiological evidence suggests 

that alternate hosts are unimportant 

in perpetuating the disease on 

wheat. 

As noted in a previous review 

(Shaw, 1999), the proportion of land 

devoted to wheat in a region could 

affect the importance of M. 

graminicola as a pathogen. As the 

proportion increases, so the 

distance between last year’s fields 

and this year’s will decline. Even 

by wind, the number of spores 

moving a given distance declines 

rapidly with distance, so moderate 

changes in average distance 

between fields could cause 

substantial changes in the density 

of initial infections. In turn, at low 

densities, this could affect the 

importance of the disease at the end 

of the cropping season. The detail 

depends on how cropland is 

organized and how new 

wheatlands tend to be disposed 

relative to old, as well as on the 

strength of linkages between initial 

and end-of-season disease. 

At the Long Ashton conference 

in 1997, a crucial question in 

understanding the uniformity in 

genetic composition of M. 

graminicola worldwide was whether 

seed-borne transport could ever 

occur. This apparently simple 

question remains open, and is far 

from simple, since very, very rare 

events could provide enough 

migration to leave populations 

genetically linked. Suppose a 

million seeds each from a diseased 

crop and a fungicide treated crop 

are grown, and a lesion appears on 

one plant from the diseased crop. 

Can we confidently say that lesion 

arose from seed transmission or 

could it have been attributable to a 

failure of isolation and a stray 

ascospore? Some form of gene 

exchange between widely 

dispersed populations apparently 

occurs, so the geneticists tell us, but 

it may be almost impossible to 

distinguish the various categories 

of very rare events giving rise to 

this.

96 

Session 5 — M.W. Shaw 

The pathogen appears to have 

been becoming more widespread 

worldwide. A most interesting 

series of data is provided by Gilbert 

(1998) showing a more or less 

linear increase in M. graminicola 

incidence between 1990 and 1995 in 

southern Manitoba, from a very 

scarce disease to the most 

prevalent. Coupled with the 

genetic evidence that populations 

worldwide are genetically very 

similar (McDonald et al., 1995) it 

does seem possible that a novel 

form of the pathogen has been 

spreading worldwide. If true, this 

would raise the interesting 

question as to what 

epidemiological characteristic 

confers the new form’s 

invasiveness. 

Phaeosphaeria 

nodorum 

Within crops 

Multiplication is more rain 

dependent than M. graminicola, 

since pycnidia are produced in 

response to rain as well as 

dispersed by it. Conidia require 

wet periods to infect and do not 

tolerate interruptions well. The 

pathogen also appears to multiply 

ineffectively in cold conditions. 

Correlations with weather 

conditions are much better (Djurle 

et al., 1996; Gilbert et al., 1998) and 

more closely linked in time to 

serious outbreaks than for M. 

graminicola. In wet, warm weather, 

typical of summer in some regions, 

latent periods can be shorter than 

in M. graminicola. Progress up the 

growing plant is correspondingly 

faster and more regular 

(Mittermeier and Hoffmann, 1984). 

Like M. graminicola spores, 

spores of some isolates of P. 

nodorum infect with a startlingly 

high probability when rare on a leaf 

surface, the infection efficiency per 

spore falling rapidly with total 

numbers attacking in a droplet 

(Jeger et al., 1985)(MWS, 

unpublished). The ecological 

advantage is presumably that 

reinfection of a new crop is very 

effective, after which survival of the 

isolate is more or less certain. The 

epidemiological consequence is 

surprisingly rapid early spread of 

the pathogen with subsequent rapid 

decline in apparent epidemic rate. 

Between crops 

Phaeosphaeria nodorum can be 

seedborne, and before routine 

fungicide treatment of seed and the 

upper parts of the crop, substantial 

numbers of seeds were infected. In 

some regions, such as northern 

Europe, the disease appears to have 

become much less important during 

the 1980s and 1990s. It is tempting 

to ascribe this decline to the 

increased use of fungicides 

reducing seed infection both in the 

ear and at planting. Recent 

experiments in other parts of the 

world suggest that seedborne 

inoculum is crucial in many places 

(Milus and Chalkley, 1997). 

Alternate hosts seem to harbor 

isolates of the pathogen capable of 

attacking wheat, but there is 

sufficient partial specialization that 

these do not act as the source of 

most infections on wheat as well as 

isolates clearly partially specialized 

to other hosts (Krupinsky, 1997a; 

1997b). Crop residues have been 

shown to be important (Cunfer, 

1998) but international survey 

evidence does not suggest they are 

the dominant source of inoculum 

(Leath et al., 1994). 

Ascospores have been found, 

but the evidence for their ubiquity 

and epidemiological importance 

seems to vary geographically. 

Trapping experiments like those 

used to show how airborne 

inoculum of P. nodorum varies 

through the year have been 

published by Cunfer (1998). These 

showed that in Georgia, USA, 

inoculum persisted for long periods 

in stubble, detectable sporadically 

for at least 18 months after the crop 

was harvested. As little as 17 m 

from a field edge, inoculum was 

trapped only once, in March, even 

though both mating types of the 

fungus were present and could 

potentially form perithecia. This 

suggests that sexual reproduction is 

unusual, though possibly not 

absent. 

These data are consistent with 

the relatively old published data on 

ascospore release in France (Rapilly 

et al., 1973). Anecdotally, near 

Reading in 1994 we observed a 

sudden patch of the disease in May 

in a first wheat. Although all 

isolations were from a single plot, 

and the disease had not been 

previously observed in that crop, 13 

genotypes tested using RFLPs were 

of different genotypes (C.N.F.M.R.J 

Pijls and M.W. Shaw, unpublished). 

However, the most extensive 

study made, in Poland, 

demonstrated a quite different 

picture, with ascospores of P. 

nodorum present throughout the 

year and at densities that appeared 

to be independent of distance from 

the nearest infected plot (Arseniuk 

et al., 1998). Ascospores were also 

found throughout the year in 

northern Germany, but the trap was 

operated over an unharvested field, 

so it is not possible to say whether

the spores were from local or 

distant sources (Mittelstadt and 

Fehrmann, 1987). 

References 

Arseniuk, E., T. Goral, and A.L. 

Scharen. 1998. Seasonal patterns of 

spore dispersal of Phaeosphaeria 

spp. and Stagonospora spp. Plant 

Disease 82:187-194. 

Bannon, F.J., and B.M. Cooke. 1998. 

Studies on dispersal of Septoria 

tritici pycnidiospores in wheatclover 

intercrops. Plant Pathology 

47:49-56. 

Brennan, R.M., B.D.L. Fitt, G.S. Taylor, 

and J. Colhoun. 1985a. Dispersal of 

Septoria nodorum pycnidiospores by 

simulated rain and wild. Journal of 


Brennan, R.M., B.D.L. Fitt, G.S. Taylor, 

and J. Colhoun. 1985b. Dispersal of 

Septoria nodorum pycnidiospores by 

simulated raindrops in still air. 

Journal of Phytopathology 112:281- 

290. 

Cunfer, B.M. 1998. Seasonal 

availability of inoculum of 

Stagonospora nodorum in the field in 

the southeastern USA. Cereal 

Research Communications 26:259- 

263. 

Djurle, A., B. Ekbom, and J.E. Yuen. 

1996. The relationship of leaf 

wetness duration and disease 

progress of glume blotch, caused 

by Stagonospora nodorum, in winter 

wheat to standard weather data. 

European Journal of Plant 


Eriksen, L., M.W. Shaw, and H. 

Østergård. 1999. A model of the 

effect of pseudothecia on epidemic 

progress and genetic composition 

in Mycosphaerella graminicola. (In 

preparation.) 

Eyal, Z. 1971. The kinetics of 

pycnospore liberation in Septoria 

tritici. Canadian Journal of Botany 

49:1095-1099. 

Gilbert, J., S.M. Woods, and A. Tekauz. 

1998. Relationship between 

environmental variables and the 

prevalence and isolation frequency 

of leaf-spotting pathogen in spring 

wheat. Canadian Journal of Plant 


Epidemiology of Mycosphaerella graminicola and Phaeosphaeria nodorum: An Overview 97 

Hunter, T., R.R. Coker, and D.J. Royle. 

1999. The teleomorph stage, 

Mycosphaerella graminicola, in 

epidemics of septoria tritici blotch 

on winter wheat in the UK. Plant 


Jeger, M.J., E. Griffiths, and D.G. 

Jones. 1985. The effects of postinoculation 

wet and dry periods, 

and inoculum concentration, on 

lesion numbers of Septoria nodorum 

in spring wheat seedlings. Annals 

of Applied Biology 106:55-63. 

Kema, G.H.J., E.C.P. Verstappen, M. 

Todorova, and C. Waalwijk. 1996. 

Successful crosses and molecular 

tetrad and progeny analyses 

demonstrate heterothallism in 

Mycosphaerella graminicola. Current 

Genetics 30:251-258. 

Krupinsky, J.M. 1997a. Aggressiveness 



Plant Disease 81:1032-1036. 

Krupinsky, J.M. 1997b. Stability of 



through wheat. Plant Disease 

81:1037-1041. 

Leath, S., A.L. Scharen, M.E. 

Dietzholmes, and R.E. Lund. 1994. 

Factors associated with global 

occurrences of septoria nodorum 

blotch and septoria tritici blotch of 

wheat. Plant Disease 77:1266-1270. 

Lovell, D.J., S.R. Parker, T. Hunter, D.J. 

Royle, and R.R. Coker. 1997. 

Influence of crop growth and 

structure on the risk of epidemics 

by Mycosphaerella graminicola 

(Septoria tritici) in winter wheat. 

Plant Pathology 46:126-138. 

McDonald, B.A., R.E. Pettway, R.S. 

Chen, J.M. Boerger, and J.P. 

Martinez. 1995. The population 

genetics of Septoria tritici 

(teleomorph Mycosphaerella 

graminicola). Canadian Journal of 


Metcalfe, R.J. 1999. Selection for 

resistance to demethylation 

inhibitor fungicides in 

Mycosphaerella graminicola on 

wheat. PhD, The University of 

Reading. 

Milus, E.A., and D.B. Chalkley. 1997. 

Effect of previous crop, seedborne 

inoculum, and fungicides on 

development of Stagonospora 

blotch. Plant Disease 81:1279-1283. 

Mittelstadt, A., and H. Fehrmann. 

1987. Zum Auftreten der 

Hauptfruchtform von Septoria 

nodorum in der Bundesrepublik 

Deutschland. Zeitschrift für 

Pflanzenkrankheiten und 

Pflanzenschütz 94:380-385. 

Mittermeier, L., and G.M. Hoffmann. 

1984. Untersuchungen zur 

Populationsentwicklung von 

Septoria nodorum in Feldbestund 

von Weizen. Zeitschrift fur 

Pflanzenkrankheiten und 

Pflanzenschutz 91:629-640. 

Rapilly, F., B. Foucault, and J. 

Lacazedieux. 1973. Études sur 

l’inoculum de Septoria nodorum 

Berk. (Leptosphaeria nodorum 

Müller) agent de la septoriose du 

blé. I. Les ascospores. Annales de 

Phytopathologie 5:131-141. 

Shaw, M.W. 1987. Assessment of 

upward movement of rain splash 

using a fluorescent tracer method 

and its application to the 

epidemiology of cereal pathogens. 


Shaw, M.W. 1991a. Interacting effects 

of interrupted humid periods and 

light on infection of wheat leaves 

by Septoria tritici (Mycosphaerella 

graminicola). Plant Pathology 

40:595-607. 

Shaw, M.W. 1991b. Variation in the 

height to which tracer is moved by 

splash during natural summer rain 

in the UK. Agricultural and Forest 

Meteorology 55:1-14. 

Shaw, M.W. 1999. Population 

dynamics of septoria in the crop 

ecosystem. In Septoria on Cereals: 

A Study of Pathosystems (J.A. 

Lucas, P. Bowyer and H.A. 

Anderson, eds.). CABI Publishing, 

Wallingford, UK. pp. 82-95. 

Shaw, M.W., and D.J. Royle. 1989. 






Shaw, M.W., and D.J. Royle. 1993. 

Factors determining the severity of 

Mycosphaerella graminicola (Septoria 

tritici) on winter wheat in the UK. 

Plant Pathology 42:882-899.

98 

Spore Dispersal of Leaf Blotch Pathogens of Wheat 

(Mycosphaerella graminicola and Septoria tritici) 

C.A. Cordo, 1, 3 M.R. Simón, 2 A.E. Perelló, 1, 4 and H.E. Alippi1 1 Centro de Investigaciones de Fitopatología (CIDEFI), Facultad de Ciencias Agrarias y Forestales de La Plata, 

La Plata, Argentina 

2 Laboratorio de Cerealicultura, Facultad de Ciencias Agrarias y Forestales de La Plata, La Plata, Argentina 

3 Comisión de Investigaciones Científicas (CIC), Provincia de Buenos Aires, Argentina 

4 Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Provincia de Buenos Aires, 

Argentina 

Abstract 

The spatial and temporal patterns of discharge and dissemination of air-borne Mycosphaerella graminicola spores 

and of Septoria tritici spores through rain splash were studied. Spore traps were used to monitor both ascospores and 

pycnidiospores when the wheat crop was in the vegetative and debris states. Relationships between distance from a point 

source and weather variables such as rainfall, relative humidity, and air temperature were analyzed. The release of 

pycnidiospores was favored by rainfall, as was explained through the multiple regression model (18% of the variation). Air 

dispersal of ascospores and splash dispersal of pycnidiospores were significantly influenced by each of the weather 

variables. The number of air-borne ascospores increased in association with rainfall. The multiple regression model 

explained 59% of the variation. The correlation analysis showed significant association with temperature, humidity, and 

rainfall; the regression coefficients of the climatic variables were significant. The effect of different distances from the 

inoculum source on the density of rain-splashed pycnidiospores and wind-borne ascospores was not significant. 

Pycnidiospores were the omnipresent inoculum in the cereal-producing area during the observed period. Thus this 

inoculum poses a risk to crop production and may be important to the epidemiology of septoria diseases under the climatic 

conditions in the wheat-producing areas of Argentina. 

Leaf blotch, caused by Septoria 

tritici Rob.ex Desm. (teleomorph 

Mycosphaerella graminicola (Fuckel) 

Schroeter, in Cohn) is an important 

wheat (Triticum aestivum) disease 

that causes yield losses in different 

regions of the world every year 

(Shipton et al., 1971; Eyal, 1981; 

Eyal et al., 1987). Its incidence 

depends on cultivar susceptibility, 

inoculum availability, crop 

management practices, and 

favorable environmental conditions 

(cool temperature, high humidity, 

and frequent rain). Climatic factors, 

especially precipitation, affect 

fungal growth and the amount and 

timing of spore production, as well 

as the release, dispersal, and 

deposition of spores. Unusually 

intense rain may cause the onset of 

a S. tritici epidemic in a wheat crop. 

The greatest risk to a crop is related 

to the occurrence of conditions that 

favor spore dispersal during and 

shortly after flag leaf emergence. 

Spore dispersal and infection at this 

time favors a second generation of 

pathogens. Spore dissemination 

patterns of Phaeosphaeria spp. and 

Stagonospora spp. have been 

described (Arseniuk and Góral, 

1998; Góral and Arseniuk, 1998; 

1991). The release of M. graminicola 

ascospores occurred at two peak 

times of the year (at crop 

emergence and emergence of the 

upper two leaves) (T. Hunter 

unpublished). 

This work aimed at producing a 

mathematical model of 

pycnidiospore and ascospore 

dispersal by: 

1. determining the pattern of spore 

dispersal during a 6-month 

period; 

2. investigating the effect of 

climatic variables (rainfall, 

temperature, humidity) on 

density of air-borne spores; and 

3. doing a preliminary analysis of 

the dispersal distance for both 

types of spores. 


In the experiment station 

situated in Los Hornos, near La 

Plata, Buenos Aires Province, airborne 

spores were collected on 13 

spore traps made of PVC capsules 

containing slides covered with 

petroleum jelly. The capsules were 

fixed to wooden stakes 0.7 m above 

the soil surface. Glass tubes 0.03 m 

in diameter and 0.16 m long were

placed near the capsules to catch 

rain-splashed spores. The capsules 

moved with the wind to ensure that 

the slides caught spores in different 

weather conditions. The spore traps 

were located at different distances 

(11 of them at 1.5 m and 2 at 12 m) 

from a wheat plot 30 m long and 10 

m wide. Spore samplers were 

arranged parallel to the length of 

the test plot. 

The plot was sown on 24 June 

1998 and inoculated twice (17 July 

and 12 August) to obtain high 

disease incidence. Plants were 

inoculated when the second leaf 

unfolded (GS12). The main shoot 

and second side shoot (GS 22) 

(Zadoks et al., 1974) were 

inoculated by spraying a 

pycnidiospore suspension (5 x 10 6 

spores/ml) of one S. tritici isolate. 

Slides were collected and examined 

weekly from October 1998 to March 

1999. The rain-splashed spores were 

identified by observing one drop of 

rain water stained with aniline blue 

(1/100) solution under the 

microscope. Four spore counts (1 

cm 2 each) were done on every 

sample. Furthermore, ascospores 

and pycnidiospores on the entire 

slide area covered with petroleum 

jelly were counted. 

Different populations of spores 

were observed under a light 

microscope at 100x magnification. 

Identification was based on the 

morphology of Mycosphaerella spp. 

and Phaeosphaeria spp. ascospores 

and Septoria spp. pycnidiospores. 

Viability of air-borne spores was 

determined by recording their 

germination directly on the 

petroleum jelly on the slides. 

Climatic variables (rainfall, 

temperature, and relative humidity) 

were recorded at the meteorological 

observatory in La Plata. 

Spore Dispersal of Leaf Blotch Pathogens of Wheat (Mycosphaerella graminicola and Septoria tritici) 99 

Multiple regression analyses 

were used to explore the 

relationship between the number of 

pycnidiospores in rain water and 

petroleum jelly, and ascospores in 

petroleum jelly, and the three 

weather variables. An analysis of 

variance was performed to 

determine significant differences 

between spore traps placed at 

different distances. Pycnidiospore 

and ascospore dispersion was 

plotted in relation to climatic 

variables. 


During the observed period, the 

weekly mean temperature ranged 

between 14ºC and 25ºC, relative 

humidity between 64 and 84%, and 

rainfall between 0 and 135 mm. 

Figure 1a and b, and Figure 2a, 

b, and c show the distribution of 

pycnidospores in rain water and 

petroleum jelly and of ascospores in 

no. spores/slide/week 

no. spores/slide/week 

14 

12 

10 

8 

6 

4 

2 

0 

40 

35 

30 

25 

20 

15 

10 

5 

0 

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8/11/98 

Pycnidiospores 

Ascospores 

18/10/98 

25/10/98 

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22/11/98 

15/11/98 

22/11/98 

29/11/98 

5/12/98 

29/11/98 

5/12/98 

12/12/98 

12/12/98 

rain water with weather variables 

throughout the 24 weeks of 

sampling. 

During the 6-month period, 

pycnidiospores were always 

present in both types of sampling. 

Figure 1a shows an increase in rainsplashed 

pycnidiospores around 

the week of 21 December. This 

increase was associated with a high 

rainfall regimen in which intense 

rains lasting as long as five hours 

without interruption occurred. 

However, correlation coefficients 

and partial correlation coefficients 

with weather variables were not 

significant (Table 1). Application of 

a multiple regression model did not 

yield significant numbers either 

(Table 2). The increased amount of 

pycnidiospores was associated with 

the increase in rainfall between 22 

January and 9 February 1999. The 

pycnidiospore pattern showed a 

marked reduction from 30 

December to 9 February. This was 

Mean of pycnidiospores 

21/12/98 

30/12/98 

Sampling date 

21/12/98 

30/12/98 

6/1/99 

15/1/99 

6/1/99 

15/1/99 

22/1/99 

29/1/99 

Mean of pycnidiospores and ascospores 

Sampling date 

22/1/99 

29/1/99 

9/2/99 

17/2/99 

9/2/99 

17/2/99 

26/2/99 

5/3/99 

26/2/99 

5/3/99 

12/3/99 

19/3/99 

12/3/99 

19/3/99 

Figure 1. Mean counts of pycnidiospores in rainwater (a), and pycnidiospores and ascospores in 

petroleum jelly (b) settled on microscope slides. 

A 

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B 

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Temperature (°C) 

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Relative humidity (%) 

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Figure 2. Weekly mean rainfall (a), weekly mean temperature (b), and weekly mean relative 

humidity (c). 

related to the end of the crop 

vegetative period and the advent of 

saprophytic pathogens on the 

wheat debris. A new increase in 

pycnidiospores on 5 March was 

related to the first natural infection 

of seedlings by septoria leaf blotch. 

The pycnidiospore pattern in 

petroleum jelly was constant from 

the first week of observation 

(Figure 1b). The increased density 

was associated with the amount of 

rain water. The correlation 

A 

27/3/99 

B 

27/3/99 

C 

27/3/99 

coefficient and the partial 

regression coefficient between 

pycnidiospores and rainfall were 

significant (Table 1), as was the 

regression coefficient for rainfall in 

the multiple regression model. This 

model explained 18% of the 

variance (Table 2). Temperature and 

humidity during this period were 

probably not so high as to affect the 

number of pycnidiospores released. 

Similar to observations by Arseniuk 

and Góral (1998), we recorded high 

Table 1. Correlation coefficients and partial 

correlation coefficients between number of 

pycnidiospores in rain water and petroleum 

jelly and number of ascospores of Septoria 

tritici and Mycosphaerella graminicola with 

weather variables. 

Temp- Relative 

erature humidity Rainfall 

Pycnidiospores/ 

rain water -0.20 ns a 0.06 ns 0.26 ns 

-0.19 ns b 0.04 ns 0.04 ns 

Pycnidiospores/ 

p. jelly 0.12 ns 0.11 ns 0.53** 

0.27 ns 0.01 ns 0.46* 

Ascospores 0.53** 0.46* 0.57** 

0.62** 0.42* 0.60** 

a= correlation coefficient. 

b= partial correlation coefficient. 

Table 2. Multiple regression model of 

weather variables and number of 

pycnidiospores in rain water, petroleum jelly, 

and ascospores of Septoria tritici and 

Mycosphaerella graminicola. 

Significance 

Coefficient level 

No. of pycnidiospores 

in water 

Constant 9.33 

Temperature -0.26 ns 

Relative humidity -0.01 ns 

Rainfall 

No. of pycnidiospores 

in p. jelly 

0.02 ns 

Constant 11.31 ns 

Temperature 0.20 ns 

Relative humidity 0.07 ns 

Rainfall 

No. of ascospores 

0.08 P

ainfall increased. Periods of low 

rainfall were associated with low 

ascospore density (30 December to 

15 January, 17 February, and 5 

March). Temperatures after week 12 

were in general above 20ºC, 

whereas in the previous period they 

were generally lower. It is thus 

likely that both the disease cycle 

and the increase in temperature 

affected ascospore release. Analysis 

of the partial correlation, which 

considers variables as being 

independent, showed significant 

association with temperature, 

relative humidity, and rainfall 

(Table 1). The multiple regression 

model (Table 2) explained 59% of 

the variance, and the regression 

coefficients for climatic variables 

were significant. As Arseniuk and 

Góral established in 1998, the 

abundance of ascospores reached 

its peak at harvest time. After 

harvest, plant debris decomposed 

and the amount of air-borne spores 

was reduced. Despite this 

reduction, ascospores were also 

released when there was low 

rainfall and adequate relative 

humidity. Arseniuk and Góral 

(1998) observed that less than 1 mm 

of rainfall and high relative 

humidity were enough to increase 

the number of air-borne ascospores. 

Spore Dispersal of Leaf Blotch Pathogens of Wheat (Mycosphaerella graminicola and Septoria tritici) 101 

Finally, the effect of different 

distance from the inoculum source 

(1 m and 12 m) on the density of 

ascospores and pycnidiospores was 

not significant, in agreement with 

Góral and Arseniuk (in press 1998; 

Arseniuk and Góral, 1998) (Table 

3). The number of spores near the 

inoculum source and at 12 m was 

similar. 

It is concluded that air dispersal 

of ascospores and pycnidiospores 

plays a role in the epidemiology of 

Mycosphaerella (Septoria) blotch 

under the climatic conditions east 

of Buenos Aires, Argentina. 

Pycnidiospores were produced in 

greater abundance than ascospores 

and they were the predominant 

source of inoculum. The abundance 

of pycnidiospores probably reflects 

their greater importance in the 

epidemiology of leaf blotch of 

wheat. 

Table 3. Analysis of variance for mean values 

of pycnidiospores and ascospores sampled at 

different distances from an inoculum source. 

Source of variation Mean square 

Distance 53.7 ns 

Error 35.0 

ns= not significant according to the F test. P=0.05. 


We are grateful to the Comisión 

de Investigaciones Científicas, 

Buenos Aires Province, and the 

Consejo Nacional de 

Investigaciones Científicas y 

Tecnológicas for their financial 

support. We also thank Ing. Agr. D. 

Bayo, Mrs. N. Kripelz, Mr. B. Cordo 

López, and J. Balonga for their 

technical assistance. 

References 

Arseniuk, E., and T. Góral. 1998. 

Seasonal patterns of spore 

dispersal of Phaeosphaeria spp. and 

Stagonospora spp. Plant Dis. 82:187- 

194. 

Eyal, Z. 1981 Integrated control of 

Septoria diseases of wheat. Plant 

Dis. 65:763-768. 

Eyal, Z., A.L. Scharen, M.J. Prescott, 






Góral, T., and E. Arseniuk. 1991. 

Effect of climatic conditions on 

liberation and dispersal of spores 

of Leptosphaeria spp. in the air. 

Phytopath. Polonica 2 (XIV):28-34. 

Góral, T., and E. Arseniuk. 1998. The 

study of relationship between 

distance from a point inoculum 

source, weather variables, and the 

air presence of Phaeosphaeria spp. 

ascospores in warmer and cooler 

sub-periods of a growing season. 

Plant Breeding and Seed Science 

(in press). 

Shipton, W.A., W.J.R. Boyd, A.A. 

Rossielle, and B.I. Shearer. 1971. 

The common Septoria diseases of 

wheat. Bot. Rev. 27:231-262. 

Zadoks, J.C., Chang, T.T., and 

Konzak, C.F. 1974. A decimal code 

for the growth stages of cereals. 

Weed Research 14: 415-421.

102 

Epidemiology of Seedborne Stagonospora nodorum: 

A Case Study on New York Winter Wheat 

D.A. Shah and G.C. Bergstrom 

Department of Plant Pathology, Cornell University, Ithaca, New York, USA 

Abstract 

Stagonospora nodorum blotch is the most important component of the foliar disease complex that attacks New York winter 

wheat. Ascospores of the teleomorph Phaeosphaeria nodorum are not commonly observed in New York, where wheat is 

generally preceded in sequence by several years of nonhost, rotational crops. Wheat seed infection by Stagonospora 

nodorum is common, the extent and range depending mainly on rainfall during the production season. Transmission of the 

pathogen from infected seeds to coleoptiles can approach 100% over a wide soil temperature range; transmission to the first 

leaves is less than 50% and is most efficient at soil temperatures below 17 ºC. Nevertheless, under the high densities at which 

wheat is sown, a significant number of infected seedlings per unit area can originate from relatively low initial seed infection 

levels and transmission efficiencies. Stagonospora nodorum blotch epidemics arising from infected seed potentially can be 

managed by reducing initial seedborne inoculum and its transmission. Wheat cultivars exhibit differential responses to 

infection of seed by S. nodorum, and this seed resistance appears to be under genetic control separate from foliar resistance. 

Breeding for reduced frequencies of seed infection and transmission, along with improved disease management in seed 

production fields and the application of seed fungicides, may comprise an effective integrated strategy for managing 

stagonospora nodorum blotch in wheat production systems similar to that in New York. 

The Pathosystem 

in New York 

Approximately 53,000 hectares 

of soft winter wheat (mainly white 

cultivars for pastry flour) are 

cultivated annually as a rotational 

crop on vegetable, dairy, and cash 

grain farms in western and central 

New York. Stagonospora nodorum 

blotch is the most prevalent and 

severe foliar disease affecting the 

crop (Schilder and Bergstrom, 

1989). The disease is currently 

undermanaged. Adapted wheat 

cultivars are susceptible, and 

because of low grain prices and 

inconsistent returns on fungicide 

expenditure, few producers apply 

foliar fungicide. 

Several observations led to the 

hypothesis that infected seed is the 

primary inoculum source for 


epidemics in New York. Firstly, 

infected wheat debris, regarded as 

the primary inoculum source in 

continuously or frequently cropped 

wheat systems, is eliminated from 

wheat fields by three- to six-year 

rotations. New York wheat fields 

are also relatively small and 

scattered, reducing the chances of 

infected debris blowing from one 

wheat field to another. Stagonospora 

nodorum infects several grasses, but 

their role in epidemic initiation on 

wheat is likely minimal (Krupinsky, 

1997), and there is some evidence 

of host specificity (Ueng et al., 1994; 

Krupinsky, 1997). The teleomorphic 

stage, P. nodorum, formed typically 

on wheat straw, has not been 

recovered in New York, despite 

concerted searches of debris and 

aerial spore trapping from fields 

affected heavily by stagonospora 

nodorum blotch (Bergstrom, 

unpublished). Moreover, most 

straw is baled and removed from 

fields shortly after harvest, and the 

remaining stubble is sometimes 

plowed under in late summer 

before planting alfalfa or grass, or 

is plowed the following spring 

prior to planting of corn, 

vegetables, or soybean. 

About 40% of New York winter 

wheat is underseeded with red 

clover, which serves as a winter 

cover crop. Clover attains a height 

of 30 to 40 cm, enough to 

completely cover unplowed 

stubble 20 to 25 cm high, thus 

impeding spore dispersal. 

Assuming that the P. nodorum stage 

does occur undetected, current 

cultural practices would diminish 

substantially its role in disease 

epidemiology in New York wheat. 

Shah et al. (1995), using DNA 

fingerprinted isolates of the 

pathogen, demonstrated that 

seedborne S. nodorum could initiate 

foliar epidemics under New York 

field conditions and foliar disease 

severity during grain development 

may be correlated with seed 

infection incidence (Shah et al., 

1995).

Seed Surveys 

Most New York wheat 

producers sow certified seed that 

has passed minimal standards for 

germination, cultivar purity, 

contamination by weed seed and 

foreign materials, and infection by 

smuts and bunts. Infection by S. 

nodorum is not part of the 

certification standard. Winter 

wheat seedlots were surveyed from 

1990 to 1996 for S. nodorum by 

assaying seed samples on SNAW 

medium (Manandhar and Cunfer, 

1991). Parts of the survey have 

been published (Shah and 

Bergstrom, 1993). In some years, all 

sampled lots contained seed 

infected by S. nodorum, and no 

cultivar was completely resistant to 

seed infection. Seasons with higher 

rainfall during wheat elongation 

through grain formation stages 

resulted in elevated seed infection 

incidences compared to low rainfall 

seasons (Figure 1). 

Transmission from 

Infected Seed 

Four lots (representing the cvs. 

Cayuga, Geneva, and Harus), 

ranging in infection incidence from 

Seed infection incidence (%) 

50 

140 

40 

120 

100 

30 

20 

1-71 

2-77 

80 

60 

40 

10 

0-19 

0-42 

20 

0 

1990 1991 1995 

Year 

1996 

0 

Figure 1. Mean seed infection incidence by 

Stagonospora nodorum in New York winter 

wheat lots in four production seasons. 

Incidence of infection range is shown over 

each bar. Rainfall averaged over the months 

of April-June and the 15 major wheat 

growing counties in western and central 

New York are shown by the line graph. 

Rain (mm) 

Epidemiology of Seedborne Stagonospora nodorum: A Case Study on New York Winter Wheat 103 

53 to 96%, were sown in soil at five 

temperatures (9, 13, 17, 21, 25 ºC), 

at 90 % relative humidity and a 16h 

photoperiod. All seedlings were 

harvested at the second leaf 

emerging stage, and coleoptiles 

were inspected for lesions induced 

by S. nodorum. Segments of the first 

leaf were plated onto Bannon’s 

medium (Bannon, 1978). Plates 

were incubated for 14 d under near 

ultraviolet light at room 

temperature. Leaf pieces were then 

inspected for S. nodorum pycnidia, 

which confirmed infection of the 

leaf. Transmission frequencies to 

the coleoptiles and first leaves were 

analyzed by SAS Proc Mixed 

(version 6.12; SAS Institute Inc., 

Cary, NC). 

Germination was slightly, but 

not significantly, lower at 9 ºC. 

Transmission to the coleoptiles was 

high at each temperature, but the 

effect of temperature was 

significant (P = 0.0001), reflecting 

differences in transmission at the 

extremes of 9 and 25 ºC. Pycnidia 

were found sometimes on the 

coleoptiles. Transmission to the 

first leaf was much less frequent 

and was temperature dependent. 

The average transmission 

frequency at 9 ºC was 0.39, but 

dropped to 0.03 at 25 ºC. The 

pathogen was not distributed 

evenly in leaf tissue. It was 

recovered at higher frequency from 

sections of the first leaf proximal to 

the stem than from sections taken 

from the leaf apex region. 

Approximately 50% of infected first 

leaves were asymptomatic. 

At a transmission frequency of 

0.1, based conservatively on our 

results, a seedlot with 5% infected 

seed would give rise to an average 

of one infected seedling per m 2 in a 

stand of 200 seedlings per m 2 . 

Simulations 

We simulated stagonospora 

nodorum blotch epidemics from 

infected seedlings at main shoot and 

3 tillers to early dough, a period of 

about 60 to 70 d for New York wheat, 

using apparent infection rates (sensu 

van der Plank, 1963) derived from or 

reported in the literature (Jeger et al., 

1983; Rambow, 1989) and the logistic 

model (van der Plank, 1963). Near 

100% incidence of infection by the 

early dough stage is possible from as 

low as one infected plant per m 2 

(Figure 2). Relatively low seed 

infection incidences and transmission 

rates, without any increase in disease 

incidence over the winter, could 

conceiveably result in 50% of all 

plants infected by flowering (Figure 

3). Decreasing the initial seedling 

disease incidence can delay the 

epidemic significantly (Figure 3). 

Differential Seed 

Infection Among 

Cultivars 

To examine the possibility of 

cultivar differential response to seed 

infection, we assayed seed samples 

Disease incidence 

1 

0.8 

0.6 

0.4 

0.2 

0 

0 10 20 30 40 50 60 70 

Days 

Figure 2. Increase in stagonospora nodorum 

blotch incidence with apparent infection rates 

of 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, or 0.19, starting 

from an initial seedling disease incidence of 

0.005, which corresponds to 1 infected plant 

per m2 at a density of 200 per m2 . A period of 70 

days corresponds to the interval from main 

shoot and 3-tiller stage to early dough stage 

under New York winter wheat production 

conditions.

Session 5 — D.A. Shah and G.C. Bergstrom 

104 

from each of four New York winter 

wheat trial locations in 1995 and 

1996. Data for two 1995 sites are 

shown in Figure 4. Results for 1996 

were similar. The effect of local 

environment is significant; seed 

infection at site B is greater for all 

cultivars than at site A. The initial 

inoculum sources were the same at 

both sites since seed used for 

sowing came from the same lot for 

any given cultivar. Some cultivars 

(Delaware and Houser, for 

instance) had consistently less seed 

infection than others, even across 

different production environments 

(Figure 4). 

Screening of the cultivars for 

differential responses to seed 

infection by S. nodorum was 

continued under glasshouse 

conditions. Flag leaves and ears 

were inoculated with spore 

suspensions of a single isolate at 

10 6 spores/ml. Flag leaves were 

assessed for percent leaf area 

diseased 15 d post-inoculation, and 

seeds were assayed on SNAW 

medium upon maturity. Seed 

infection was high, but again, some 

cultivars had less seed infection 

than others. There was a strong 

correlation between the field based 

Disease incidence 

1 

0.8 

0.6 

0.4 

0.2 

0 

0 10 20 30 40 50 60 70 

Days 

Figure 3. Increase in stagonospora nodorum 

blotch incidence from initial seedling 

disease incidences of 0.001, 0.003, 0.005, 0.01, 

0.02, or 0.04, given an apparent infection rate 

of 0.14. The 70 day period corresponds to the 

interval from main shoot and 3-tiller stage to 

early dough stage under New York winter 

wheat production conditions. 

observations and the results of the 

quantitative glasshouse 

inoculations when cultivars were 

ranked according to seed infection 

level. There appears to be genetic 

mechanisms of resistance to seed 

infection by S. nodorum. The poor 

correlation between flag leaf 

disease severity and seed infection 

incidence suggests that seed and 

foliar resistance are under separate 

genetic control. 

Potential for Integrated 

Management 

No single control tactic is likely 

to reduce seedborne inoculum 

below levels that could initiate 

epidemics under favorable 

environments. The most effective 

triazole seed fungicides can reduce 

pathogen transmission in grossly 

infected seedlots so that only 1 to 

2% of seedlings are infected, still 

enough for epidemics to develop 

(Bergstrom, unpublished). A 

strategy integrating breeding for 

reduced seed infection and 

transmission frequencies, improved 

disease management in seed 

production fields, and the 

application of seed fungicides may 

Seed infection incidence (%) 

60 

50 

40 

30 

20 

10 

0 

Site A 

Site B 

Delaware 

Houser 

Annett 

Chelsea 

ACRon 

Pioneer 2737W 

NYBatavia 

Karena 

Harus 

Caledonia 

Geneva 

Arkona 

Diana 

Year 

Figure 4. Differential seed infection of winter 

wheat cultivars by Stagonospora nodorum at 

two New York sites (A and B), located 5 km 

apart but differing in microclimate, in 1995. 

be employed to manage 


effectively in wheat production 

systems similar to that in New York. 

References 

Bannon, E. 1978. A method of detecting 

Septoria nodorum on symptomless 

leaves of wheat. Ir. J. Agric. Res. 

17:323-325. 

Jeger, M.J., Gareth-Jones, D., and 

Griffiths, E. 1983. Disease spread of 

non-specialised fungal pathogens 

from inoculated point sources in 

intraspecific mixed stands of cereal 

cultivars. Ann. Appl. Biol. 102:237- 

244. 

Krupinsky, J.M. 1997. Stability of 



through wheat. Plant Dis. 81:1037- 

1041. 

Manandhar, J.B., and Cunfer, B.M. 1991. 

An improved selective medium for 

the assay of Septoria nodorum from 

wheat seed. Phytopathology 81:771- 

773. 

Rambow, M. 1989. Befallsentwicklung 

von Septoria nodorum Berk. in 

winterweizenbeständen. 

Nachrichtenbl. Pflanzenschutz DDR 

43:209-212. 

Schilder, A.M.C., and Bergstrom, G.C. 

1989. Distribution, prevalence, and 

severity of fungal leaf and spike 

diseases of winter wheat in New 

York in 1986 and 1987. Plant Dis. 

73:177-182. 

Shah, D., and Bergstrom, G.C. 1993. 

Assessment of seedborne 

Stagonospora nodorum in New York 

soft white winter wheat. Plant Dis. 

77:468-471. 

Shah, D., Bergstrom, G.C., and Ueng, 

P.P. 1995. Initiation of Septoria 

nodorum blotch epidemics in winter 

wheat by seedborne Stagonospora 


457. 

Ueng, P.P., Cunfer, B.M., and Chen, W. 

1994. Identification of the wheat and 

barley biotypes of Stagonospora 

nodorum using restriction fragment 

length polymorphisms and 

biological characteristics. 

Phytopathology 84:1146. 

Van der Plank, J.E. 1963. Plant Diseases: 

Epidemics and Control. New York 

and London. Academic Press. 349 

pp.

Sessions 6A and 6B: Cultural Practices and Disease Management 

Influence of Cultural Practices on Septoria/Stagonospora 

Diseases 

J.M. Krupinsky 

USDA-Agricultural Research Service, Northern Great Plains Research Lab, Mandan, ND, USA 

Abstract 

The use of cultural management practices is probably one of the oldest approaches to controlling plant diseases. How 

cultural management practices such as crop rotation, tillage (residue level), fertilizer application, seeding operations, and 

disease-free seed can influence the incidence and severity of Septoria/Stagonospora diseases are reviewed. Considering that 

early reports on cultural practices have been reviewed previously, recent research will be emphasized. Management practices 

such as the use of resistant cultivars, cultivar blends, and the use of fungicides will be covered by others at the workshop. 

From ancient times various 

cultural practices have been used to 

reduce plant diseases and have 

paralleled the development of 

agriculture (Howard, 1996). 

Disease severity can be modified 

by various cultural practices, but 

the magnitude and direction of 

these effects are not always 

consistent (King et al., 1983; 

Shipton et al., 1971; Tompkins et al., 

1993). In some studies, disease 

severity can be affected more by 

trial location than by the agronomic 

practices being tested (Tompkins et 

al., 1993). 

Considering that early reports 

on cultural practices have been 

reviewed (Eyal, 1981; King et al., 

1983; Shipton et al., 1971), more 

recent research will be emphasized 

in this paper. A number of cultural 

practices such as crop rotation, 

tillage, fertilization, seeding, and 

disease-free seed will be reviewed. 

Other practices, including the use 

of resistant cultivars, cultivar 

blends, and fungicides are 

management practices that are 

covered by other authors in these 

proceedings. 

Crop Rotation: A Key 

Factor 

The survival of Septoria/ 

Stagonospora spp. on residue from a 

previous wheat crop is the most 

important means of carryover from 

one crop to the next. Researchers 

have recommended proper crop 

rotations in combination with other 

practices to reduce the severity of 

Septoria/Stagonospora diseases. 

Plowing and burning have also 

been used to reduce the amount of 

residue-borne inoculum, but these 

practices alone may still leave 

sufficient inoculum for the next 

wheat crop (Eyal, 1981; King et al., 

1983; Shipton et al., 1971). Although 

resistant cultivars are covered by 

other authors in these proceedings, 

the impact of resistant cultivars on 

the carryover of pathogens should 

also be considered. Murray et al. 

(1990) pointed out with septoria 

tritici blotch (STB) that resistant 

cultivars not only reduce crop losses 

but the residue can also influence 

the next crop. Residue from 

resistant crops reduces the potential 

disease severity the following year 

because less inoculum is provided 

to initiate the epidemic. 

105 

Early researchers, such as Rosen 

(1921), included proper crop 

rotation in their recommendations 

for control of stagonospora 

nodorum blotch (SNB). Crop 

rotations take advantage of the fact 

that plant pathogens important on 

one crop may not cause disease 

problems on another crop. 

Appropriate crop rotations lengthen 

the time between crop types so that 

pathogen populations have time to 

decline. Although pathogens may 

not be completely eliminated, there 

is a reduction in the pathogen 

population. By rotating among crop 

types, the pathogens on residue 

from the previous crop will not 

infect the crop being grown 

(Krupinsky et al., 1997). Crop 

rotation allows time for the 

decomposition of residue on which 

pathogens carry over, and natural 

competitive organisms reduce the 

pathogens on the remaining residue 

while unrelated crops are being 

grown. Crop rotation is a key factor 

affecting the health and productivity 

of future wheat crops (Cook and 

Veseth, 1991). Crop rotation and 

residue management are most 

effective with pathogens that are 

disseminated only short distances 

but not as effective for pathogens

106 

Session 6A / Session 6B — J.M. Krupinsky 

disseminated over long distances. 

When inoculum is produced within 

a field and is disseminated only 

short distances, as with 

Stagonospora nodorum in the 

southeastern USA, crop rotation is 

an important management practice 

(Cunfer, 1998). 

When evaluating methods of 

reducing the risk of disease 

severity with reduced tillage, 

Bailey and Duczek (1996) indicated 

that the most effective means of 

reducing disease is crop rotation. In 

Saskatchewan, Canada, Pedersen 

and Hughes (1992) reported that 

crop rotation was effective in 

reducing the severity of epidemics 

caused by a leaf spot disease 

complex of S. nodorum and Septoria 

tritici. In general, Septoria/ 

Stagonospora disease severity is 

greater when wheat is grown in 

monoculture, compared to wheat 

following an alternative crop. In 

Germany, Käesbohrer and 

Hoffmann (1989) reported that 

winter wheat was infected earlier 

and more frequently by S. nodorum 

in wheat after wheat, compared 

with wheat in a crop rotation. 

Sutton and Vyn (1990) found that 

the severity of SNB on spikes of 

winter wheat was higher after 

wheat compared to wheat after 

soybeans. 

Disease severity was 

significantly higher under 

monoculture than under rotation, 

particularly with no tillage, with a 

leaf-spot disease complex 

composed of Pyrenophora triticirepentis, 

Bipolaris sorokiniana, and S. 

nodorum (Reis et al., 1992, 1997). 

With P. tritici-repentis and S. tritici 

as the dominant pathogens, STB 

was significantly higher on winter 

wheat when grown in monoculture 

(Odorfer et al., 1994). With P. triticirepentis 

and S. nodorum as the 

dominant pathogens, Fernandez et 

al. (1998) observed that wheat after 

wheat had a higher disease severity 

than wheat grown after flax or 

lentil. This was particularly evident 

in years with high disease pressure 

but not in years with low disease 

pressure. 

In general, most carry-over 

inoculum of Septoria/Stagonospora 

diseases is minimized by crop 

rotations that include wheat or 

other cereals every third year 

(Wiese, 1987). Considering that 

plant residue decays more rapidly 

in warm humid conditions than in 

drier and cooler conditions, the 

amount of time necessary between 

wheat crops may vary depending 

on the environment and location. 

In Israel, Eyal (1981) reported that a 

3-5 year rotation is needed to 

decrease the incidence of STB. 

Under favorable disease conditions 

in Saskatchewan, Canada, a 

rotation of two years between 

spring wheat crops reduced disease 

severity and provided adequate 

control of STB and SNB (Pedersen 

and Hughes, 1992). Also in 

Saskatchewan, Fernandez et al. 

(1998) recommended two years of 

spring wheat followed by two 

years of a non-cereal crop, or by a 

non-cereal crop and summer fallow 

to reduce disease severity (P. triticirepentis 

and S. nodorum). 

Since Fernandez et al. (1993) 

indicated that S. nodorum, along 

with Fusarium graminearum and B. 

sorokiniana, survived longer on 

wheat residue after summer fallow 

compared to wheat residue after 

corn or soybean crops, summer 

fallow may not be as effective as an 

alternative crop in reducing 

inoculum levels. In the 

southeastern USA, S. nodorum 

inoculum may be present on wheat 

stubble on the soil surface 22 

months after a wheat crop is 

harvested, leading to 

recommendations for crop rotation 

and tillage (Cunfer, 1998). In 

addition to crop rotation, 

intercropping can be used to 

reduce inoculum movement in the 

field. In Ireland, Bannon and Cooke 

(1998) reported that the dispersal of 

pycnidiospores of S. tritici was 

reduced 33% horizontally and 63% 

vertically in a wheat-clover 

intercrop. 

Tillage 

Infested residue provides an 

important mechanism for the 

carryover of Septoria/Stagonospora 

spp. from one crop to the next. 

Tillage promotes residue 

decomposition by fracturing the 

residue and exposing it to residuedecomposing 

microorganisms. 

Thus, tillage operations such as 

plowing have been recommended 

as a means to reduce residue (King 

et al., 1983; Shipton et al., 1971). 

In recent years, conservation 

tillage practices have been 

promoted to reduce soil erosion 

and conserve soil moisture. These 

minimum or no tillage operations 

increase the quantity of crop 

residue on the soil surface. 

Increased levels of crop residues 

may influence the incidence and 

severity of plant diseases, 

depending upon the disease and 

region. Conservation tillage or 

reduced tillage practices increase, 

decrease, or have no effect on plant 

diseases (Bailey and Duczek, 1996; 

Sumner et al., 1981). Conservation 

tillage may have different effects on 

plant diseases depending on the 

soils, region, or prevailing 

environment, and the biology of 

the disease organism.

Differences in weather cycles in 

wheat growing areas are often 

dramatic, which may account for 

some of the differences in the 

impact of diseases described in the 

literature. When comparing tillage 

effects in northeastern North 

Dakota, USA, Stover et al. (1996) 

observed that different diseases 

dominated each year with different 

weather conditions. They found 

that P. tritici-repentis dominated in 

the first two years of the study, and 

septoria foliar diseases and 

fusarium head blight dominated in 

the third year. 

Tillage or lack of tillage can also 

affect the severity of individual 

diseases. Sutton and Vyn (1990) 

reported that P. tritici-repentis and 

S. nodorum were promoted when 

wheat was grown after wheat and 

minimum or no tillage was used, 

whereas S. tritici was suppressed. 

The reverse occurred when wheat 

followed alternative crops in all 

tillage treatments or following 

wheat under conventional tillage. 

With airborne ascospores of S. 

tritici implicated as the source of 

primary inoculum in Oklahoma, 

USA, Schuh (1990) concluded that 

the amount of residue after 

different tillage operations did not 

have a strong effect on disease 

severity. 

In western Canada, Bailey and 

Duczek (1996) indicated that foliar 

diseases increase under reduced 

tillage but not always to damaging 

levels. With conditions for low 

disease development, Bailey et al. 

(1992) did not observe consistent 

tillage effects on foliar diseases. In 

Kentucky, USA, Ditsch and Grove 

(1991) reported that SNB was not 

affected by tillage but powdery 

mildew infection (Erysiphe 

graminis) was higher under no 

tillage. In North Dakota, USA, with 

a leaf-spot disease complex 

composed mainly of P. triticirepentis 

and S. nodorum, Krupinsky 

et al. (1998) found generally higher 

levels of necrosis and chlorosis 

associated with no tillage 

compared to minimum or 

conventional tillage. However, in 

some trials the tillage effect varied 

depending on the nitrogen 

treatment. With a leaf-spot disease 

complex composed of P. triticirepentis, 

B. sorokiniana, and S. 

nodorum, Reis et al. (1992, 1997) 

reported that disease incidence and 

severity were higher with 

minimum and no tillage treatments 

in Brazil. In the eastern USA, both 

tillage and crop rotation are 

recommended to avoid losses to 

SNB (Cunfer, 1998; Milus and 

Chalkley, 1997). 

Burning of Residues 

Although burning crop residue 

was recommended in the past 

(King et al., 1983; Shipton et al., 

1971), it is no longer recommended 

because of environmental concerns. 

In addition, burning may not be 

hot enough to eliminate all residue, 

leaving sufficient infested residue 

to provide carryover of inoculum 

for another wheat crop (Eyal, 1981). 

In northeastern North Dakota, 

USA, Stover et al. (1996) compared 

chisel plowing (high residue) to 

moldboard plowing and burning 

followed by moldboard plowing. 

The effect of chisel plowing on 

early season foliar disease did not 

consistently carry over to late 

season severity ratings. In the first 

year, chisel plowing resulted in the 

highest late season disease severity, 

in the second year, there were no 

differences, and in the third year, 

the chisel plow treatment had the 

lowest late season disease severity. 

Influence of Cultural Practices on Septoria/Stagonospora Diseases 107 

Overall, yields were not affected by 

a tillage (burning)-related foliar 

disease effect. 

Plant Nutrition: Nitrogen 

Fertilizer 

As with other management 

practices discussed above, 

environmental conditions influence 

disease development and treatment 

responses, leading to variation in 

research results among different 

geographical regions. The severity of 

Septoria/Stagonospora diseases may 

increase or decrease with increasing 

nitrogen rates depending on the 

region. Tiedemann (1996) suggested 

that inconsistencies of Septoria/ 

Stagonospora disease response to 

nitrogen fertilization may be due to 

in part to environmental factors such 

as ozone. 

High rates of nitrogen fertilizer 

have been reported to increase the 

severity of Septoria/Stagonospora 

diseases. In addition, increased 

nitrogen can increase the danger of 

lodging and delayed maturity 

(Shipton et al., 1971). In 

Pennsylvania, USA, Broscious et al. 

(1985) reported that the severity of 

SNB and powdery mildew increased 

significantly on winter wheat as the 

rate of spring applied nitrogen 

fertilizer increased. Similarly, Ditsch 

and Grove (1991) in Kentucky, USA, 

reported that SNB and powdery 

mildew were lowest on winter 

wheat at the zero nitrogen treatment 

but increased as nitrogen rates 

increased. In New York, USA, under 

conditions of low disease severity, 

Cox et al. (1989) suggested that high 

rates of nitrogen have the potential 

to increase yield and foliar disease 

severity on winter wheat in the 

northeastern USA. In Tennessee, 

USA, Howard et al. (1994) reported 

that the severity of three foliar

108 


diseases (S. tritici, S. nodorum, and 

leaf rust [Puccinia recondita]) 

increased on winter wheat with 

higher nitrogen rates, especially 

when fungicides were not applied. 

In the United Kingdom, Leitch and 

Jenkins (1995) reported that 

Septoria/Stagonospora disease 

(principally STB) development on 

winter wheat was enhanced with 

the application of nitrogen 

throughout the season. A wide 

range of timing and splits of 

nitrogen application did not 

significantly influence the level of 

disease severity after anthesis. Also 

in the United Kingdom, Jenkyn and 

King (1988) found an increase in 

Septoria/Stagonospora diseases 

(mostly STB) on winter wheat after 

fallow compared to winter wheat 

after ryegrass. They attributed the 

increase in disease severity to an 

increased accumulation of available 

nitrogen during the fallow period. 

There have also been reports of 

no effect or a decrease in the 

severity of Septoria/Stagonospora 

diseases on wheat with increased 

nitrogen rates. In Germany, 

assessing disease damage by the 

number of pycnidia and number of 

latent infections of S. nodorum on 

winter wheat, Büschbell and 

Hoffmann (1992) reported that the 

influence of nitrogen rates was not 

significant. Also in Germany, 

Tiedemann (1996) reported that 

increased nitrogen reduced the 

severity of SNB on spring wheat, 

while increasing the severity of 

powdery mildew and leaf rust. 

This nitrogen effect on the disease 

severity of SNB was reversed at 

elevated ozone concentrations. In 

the United Kingdom, late season 

applications of urea solution 

reduced the severity of STB on the 

flag leaf of winter wheat (Gooding 

et al., 1988). Naylor and Su (1988) 

reported that the severity of SNB 

on winter wheat was not affected 

by increased nitrogen levels early 

in the season and even decreased 

with increasing nitrogen later in the 

season. 

In Maryland, USA, SNB was 

reduced on winter wheat with a 

higher nitrogen fertility rate (Orth 

and Grybauskas, 1994). They 

suggested that the reduction of 

SNB was apparently due to 

interference of splash dispersal of 

spores in a denser canopy and the 

suppressive effect of high nitrogen 

fertility. In glasshouse trials, they 

also reported that increased 

nitrogen fertility decreased the 

severity of SNB on the same winter 

wheat cultivars tested in the field. 

In North Dakota, USA, with a leafspot 

disease complex composed 

mainly of P. tritici-repentis and S. 

nodorum, Krupinsky et al. (1998) 

reported that with low nitrogen 

levels disease severity was higher 

in no tillage compared to 

conventional tillage. At higher 

nitrogen levels, the difference in 

disease severity for tillage 

treatments was greatly reduced. 

In Saskatchewan, Canada, the 

development of Septoria/ 

Stagonospora diseases on winter 

wheat was influenced by nitrogen 

fertility in one trial out of nine 

(Tompkins et al., 1993). Greater 

disease severity was associated 

with low nitrogen fertility. They 

suggested that lesion development 

may be promoted by nitrogen 

deficiency or a nutrient imbalance. 

Also in Saskatchewan, Fernandez 

et al. (1998) reported an increase in 

disease severity with an increase in 

nitrogen deficiency in dry years 

with a leaf-spot disease complex 

composed mainly of P. triticirepentis 

and S. nodorum. Disease 

severity declined with treatments 

receiving no phosphorus. 

Seeding Operations 

A higher disease severity of STB was 

associated with earlier sowings in New 

South Wales, Australia (Murray et al., 

1990). The longer time between sowing 

and heading probably leads to a higher 

disease severity. When studying 

seeding rates, row spacing, and depth 

of seeding in Pennsylvania, USA, 

Broscious et al. (1985) reported that 

increased seeding rates increased SNB 

in four out of 13 trials and decreased 

SNB in one trial. They suggested that 

growers could reduce row spacing from 

18 cm to 13 cm to increase yields 

without increasing disease severity. In 

Saskatchewan, Tompkins et al. (1993) 

reported that the severity of Septoria/ 

Stagonospora diseases increased with a 

higher seeding rate. Disease severity 

was not influenced by row spacing. 

Narrow row spacing (10 cm) with 

increased nitrogen rates reduced SNB 

on winter wheat and increased yields in 

Maryland, USA (Orth and Grybauskas, 

1994). 

Use of Disease-Free Seed 

Seed infected with S. nodorum can be 

a source of primary inoculum and a 

probable source of transmission from 

one wheat crop to the next. Inoculum 

can survive in seed for extended 

periods of time. Septoria tritici can be 

seed-borne but is not a significant 

source of inoculum (Eyal, 1981; King et 

al., 1983; Shipton et al., 1971). Although 

the use of disease-free seed may not be 

considered a cultural practice, it should 

be evaluated by the producer as a 

management practice for reducing 

disease severity. Cultural practices such 

as crop rotation may not be effective if 

seed infected with S. nodorum is used 

for planting (Luke et al., 1983). The 

beneficial effect of disease-free seed can 

be negated by sowing into residue from 

a previous wheat crop (Luke et al., 1983, 

1985; Milus and Chalkley, 1997).

In Germany, Rambow (1990) 

indicated that infected seed was the 

main source of primary inoculum. In 

Poland, Arseniuk et al. (1998) 

reported that higher seed infestation 

by S. nodorum resulted in higher 

disease levels in the field. 

Stagonospora nodorum was found in 

98% of the wheat seed samples 

tested in North Carolina, USA, and 

the fungus survived for more than 

two years on stored seed (Babadoost 

and Hebert, 1984). Using seed lots 

infected 1% to 40% with S. nodorum, 

Luke et al. (1986) reported that 10% 

seed infection was adequate to cause 

a severe epidemic in the southeastern 

USA. In the northeastern USA, Shah 

et al. (1995) found that in 1990-91, a 

season mildly conductive to disease 

development, plots sown to seed 

with less than 1% infection by S. 

nodorum developed epidemics. In 

1991-92, epidemics were initiated 

with seed infection levels as low as 

0.5%. They demonstrated that the 

same isolates in the seed used for 

planting were found in the seed 

harvested. This indicated that seed 

populations of S. nodorum could 

initiate epidemics of SNB in new 

locations and could provide year-toyear 

perpetuation of these 

populations. In Manitoba, Canada, 

plants from shriveled seed caused by 

S. nodorum had lower seedling vigor 

but with increased number of tillers 

on plants from the shriveled seed, 

the yield from plump or shriveled 

seed plots could not be differentiated 

(Gilbert et al., 1995). 

When disease-free seed is not 

available, chemical treatments and 

fungicides can be used to reduce or 

eliminate Septoria/Stagonospora 

pathogens from seed used for 

planting (Eyal, 1981; King et al., 1983; 

Shipton et al., 1971). The use of 

fungicides for seed treatment are 

covered by other authors in these 

proceedings. 

Conclusion 

With relatively low value crops 

such as small cereal grains, there is 

a need for cultural management 

practices that can reduce the 

impact of diseases (Howard, 1996). 

With the adoption of conservation 

tillage practices, additional longterm 

research is needed to 

minimize disease severity with 

integrated diverse cropping 

systems. Hopefully new 

experiments that study the 

interaction of cultural practices, 

including the development of new 

crop rotation sequences, will 

provide additional information in 

the future. Adapted resistant 

cultivars, which are an important 

factor in reducing disease 

epidemics, should be used when 

available. The best strategy to 

minimize the impact of Septoria/ 

Stagonospora diseases is to integrate 

several cultural practices into one 

system. The integration of several 

cultural practices should minimize 

disease impacts on the economics 

for the grower without increasing 

the cost of production. 


I thank B. M. Cunfer and D. E. 

Mathre for their reviews and 

constructive comments. Mention of 

a trademark, proprietary product, 

or company by USDA personnel is 

intended for explicit description 

only and does not constitute a 

guarantee or warranty of the 

product by the USDA and does not 

imply its approval to the exclusion 

of other products that may also be 

suitable. USDA-ARS, Northern 

Plains Area, is an equal 

opportunity/affirmative action 

employer and all agency services 

are available without 

discrimination. 

Influence of Cultural Practices on Septoria/Stagonospora Diseases 109 

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368. 

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R.D. 1983. Control of Septoria 

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951. 

Luke, H.H., Barnett, R.D., and Pfahler, 

P.L. 1985. Influence of soil infestation, 

seed infection, and seed treatment on 

Septoria nodorum blotch of wheat. 

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P.L. 1986. Development of Septoria 

nodorum blotch on wheat from 

infected and treated seed. Plant Dis. 

70:252-254. 

Milus, E.A., and Chalkley, D.B. 1997. 

Effect of previous crop, seedborne 

inoculum, and fungicides on 

development of Stagonospora blotch. 

Plant Dis. 81:1279-1283. 

Murray, G.M., Martin, R.H., and Cullis, 

B.R. 1990. Relationship of the severity 

of Septoria tritici blotch of wheat to 

sowing time, rainfall at heading and 

average susceptibility of wheat 

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Comparison of disease incidence on 

triticale and wheat at different 

nitrogen levels without fungicide 

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Cultivars 9:110-111. 

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1994. [The effects of different leaf 

crops in long lasting monoculture 

with winter wheat. 2 nd 

communication: Disease 

development and effects of 

phytosanitary measures]. Agribiol. 

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Development of Septoria nodorum 

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cultivation schemes in Maryland. 

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seed infestation as an infection 

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Plant Protection Bull. 44:153-155. 

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Villa Giardino. 

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Santos, H.P., and Medeiros, C.A. 

1997. Effects of cultural practices on 

the severity of leaf blotches of 

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incidence of pathogenic fungi in the 

harvested seed. Fitopatologia 

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spatial pattern of Septoria leaf 

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1340. 

Shah, D., Bergstrom, G.C., and Ueng, 

P.P. 1995. Initiation of Septoria 

nodorum blotch epidemics in 

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Stagonospora nodorum. 


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Tompkins, D.K., Fowler, D.B., and 

Wright, A.T. 1993. Influence of 

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Disease Management Using 

Varietal Mixtures 

C.C. Mundt, C. Cowger, and M.E. Hoffer 

Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA 

Abstract 

Few data are available that evaluate the impact of variety mixtures on the Septoria/Stagonospora diseases of cereals. 

The splash-dispersed nature of the pathogens and the predominance of quantitative variation for host resistance and 

pathogenicity in the Septoria/Stagonospora diseases may make interactions more complex than for the rusts and 

mildews, where major gene interactions have been the main object of study. We have found that epidemic progression of 

septoria tritici blotch can be substantially suppressed in mixtures of a susceptible and a moderately resistant variety, 

sometimes to below the level of the more resistant variety grown in pure stand. Mycosphaerella graminicola populations 

sampled from variety mixtures have been found to be reduced in pathogenicity in all mixtures that have been investigated 

thus far. Disruptive selection may be an important mechanism affecting disease progression and evolution of M. 

graminicola in variety mixtures. Major genes for resistance have the potential to contribute substantially to the use of 

variety mixtures for control of Septoria/Stagonospora diseases, both through their epidemiological impacts on disease 

spread, and through effects of induced resistance between avirulent and virulent genotypes of the pathogen that may occur 

in variety mixtures. 

Variety mixtures have been 

investigated to the greatest extent 

for obligate parasites of small 

grains (Garrett and Mundt, 1999; 

Wolfe, 1985), and are being utilized 

commercially for control of these 

diseases (Garrett and Mundt, 1999; 

Mundt, 1994). Much less 

information is available regarding 

the impact of variety mixtures on 

diseases caused by non-obligate 

pathogens. 

The effects of variety mixtures 

may differ for the Septoria/ 

Stagonospora diseases compared to 

rusts and mildews for at least two 

reasons. First, steep dispersal 

gradients caused by splash 

dispersal of conidia may decrease 

inoculum exchange among host 

genotypes in mixture and, hence, 

reduce the efficacy of mixtures for 

disease control (Fitt and 

McCartney, 1986; Mundt and 

Leonard, 1986). Second, qualitative 

incompatibility reactions are much 

less common for septoria diseases 

in current agricultural systems 

compared to the rusts and 

mildews. 

Though there clearly is much 

more host/pathogen specificity 

than has been suggested in the past 

for Mycosphaerella graminicola 

(Ahmed et al., 1995; Ahmed et al., 

1996; Cowger et al., this volume; 

Kema et al., 1986; 1987), the general 

lack of use of major genes for 

resistance to the Septoria/ 

Stagonospora diseases in agriculture 

places much greater emphasis on 

quantitative interactions. For M. 

graminicola, there clearly can be 

substantial quantitative variation 

for pathogenicity that is under the 

influence of host selection (Ahmed 

et al., 1995; 1996; Mundt et al., 

1999) and may be influenced by 

host diversity. In addition, Jeger et 

al. (1981a) have derived models 

111 

which indicate, based on 

epidemiological considerations, 

that variety mixtures can impact 

disease severity even in the absence 

of host/pathogen specificity. 

There are a limited number of 

studies that address the impact of 

variety mixtures on Septoria/ 

Stagonospora diseases in the field. 

Jeger et al. (1981b) found that 

mixing wheat varieties with 

apparent non-specific resistance 

reduced the severity of 

stagonospora nodorum blotch by 

more than 50% relative to the 

mixture components grown 

separately in pure stands, though 

overall severity levels were very 

low. Mundt et al. (1995) studied all 

possible equiproportional mixtures 

among two susceptible, one 

moderately resistant, and one 

highly resistant wheat variety. 

Mean disease reductions late in the

Session 6A / Session 6B — C.C. Mundt, C. Cowger, and M.E. Hoffer 

112 

epidemics were 27, 9, and 15% for 

the three seasons, with substantial 

differences among specific 

mixtures. 

The purpose of the work 

reported herein was to investigate 

in greater detail the effects of wheat 

variety mixtures on epidemic 

progression of septoria tritici blotch 

and to determine the influence of 

host diversity on pathogenicity of 

M. graminicola populations derived 

from field plots of pure and mixed 

stands of wheat varieties in the 

Willamette Valley of Oregon, USA. 

This location is highly conducive 

for development of the Septoria/ 

Stagonospora blotches of wheat, with 

frequent rains from November 

through June. Naturally occurring 

epidemics have varied from 

moderate to severe over the past 

decade, and commercial fields of 

susceptible varieties are sprayed 

every year. 

In Oregon, septoria tritici blotch 

is currently more important than 

stagonospora nodorum blotch, 

perhaps due to competitive 

exclusion caused by earlier 

ascospore showers of M. graminicola 

as compared to Phaeosphaeria 

nodorum (DiLeone et al., 1997). 

Septoria tritici blotch epidemics in 

Oregon begin from a very dominant 

sexual stage, with primary 

infections resulting from heavy 

ascospore showers (Mundt et al., 

1999). Ascospore showers often 

peak in November, after fall rains 

have begun, but continue at some 

level throughout the crop season 

(DiLeone et al., 1997), including 

secondary cycles of sexual 

recombination (Zhan et al., 1998). 


Field plots 

Plots were grown at the Botany 

and Plant Pathology Field 

Laboratory near Corvallis, OR, 

during the 1997-98 winter wheat 

season. Plots were sown at a rate of 

322 seeds/m2 on 20 October 1997. 

Each plot was 3.0 m (12 rows) x 5.2 

m, and planted within a 

“checkerboard” of barley (Hordeum 

vulgare) plots of equal size. 

Standard fertilization and weed 

control practices were used, 

supplemented by hand-weeding. 

Epidemics were initiated from 

naturally occurring ascospore 

showers. 

Treatments included two 

susceptible (Stephens and W-301) 

and two moderately resistant 

(Cashup and Madsen) varieties, 

and the four possible 

equiproportional mixtures of a 

susceptible and a moderately 

resistant variety. Treatments were 

replicated four times in a 

randomized complete block design. 

Percent of leaf area covered by 

lesions, on a whole-canopy basis, 

was recorded from early February 

through mid-June. Each plot 

received a rating that was the 

average of two observers. 

At the end of the season, leaves 

were sampled from each plot to 

obtain isolates for greenhouse tests 

of pathogenicity, as described 

below. The pathogen was sampled 

along a diagonal across the inner 10 

rows of each plot, with one 

sampling point per row. Two or 

three flag leaves were collected 

from each sampling point. Leaf 

samples were collected on 12 June 

1998, a time when the pathogen 

had been exposed to repeated 

generations of selection on the host 

varieties. 

Greenhouse experiment 

A greenhouse experiment was 

conducted in spring 1999 to 

determine pathogenicity of the 

field-collected isolates. Plants of 

Stephens, W-301, Cashup, and 

Madsen were raised in 10-cm 

plastic pots filled with a 

greenhouse mix that included a 

slow-release fertilizer. 

Approximately 15 seeds of a 

cultivar were sown in each pot. 

Before inoculation, plants were 

thinned to 10 per pot. Daytime 

greenhouse temperature was 

maintained from 20-25°C, and 

sodium-halide lights were used to 

extend daylength to 16 h. 

Cultures were obtained from 

field-collected leaves, stored, and 

increased by standard methods that 

have previously been described 

(Ahmed et al., 1996). Equal 

numbers of spores of the 10 isolates 

(one from each of the sampling 

points of each plot) were combined 

and the total suspension adjusted 

to 105 spores/ml. 

At 21 days after seeding, groups 

of four pots (one of each of the four 

varieties) were inoculated with a 

suspension derived from each field 

plot by placing them on a turntable 

at 16 rpm and applying 33.3 ml of 

the suspension with a hand 

sprayer. Surfactant (Tween) was 

added at the rate of one drop per 50 

ml of spore suspension. After 

inoculation, the plants were kept in

a moist chamber (wooden frame 

covered with a polyethylene 

sheet) for 72 hours. High 

humidity (95% or above) was 

maintained using a humidifier 

(ultrasonic, cool mist type) inside 

the moist chamber. The pots were 

subsequently returned to a 

greenhouse bench in a 

randomized complete block 

design. 

Percent lesion area on the 

second leaf from the base of each 

of the 10 plants in each pot was 

estimated visually at three weeks 

after inoculation. Each of two 

observers half of the plants in 

each pot. 

% diseased leaf area 


90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

6-Feb 

6-Feb 

Madsen (MR) 

Stephens (S) 

Mixture 

27-Feb 

20-Mar 

Madsen (MR) 

W-301 (S) 

Mixture 

27-Feb 

20-Mar 

10-Apr 

10-Apr 

Effects of pathogen diversity 

on epidemic progression 

A field experiment that allowed 

us to examine the influence of 

pathogen diversity on epidemic 

increase in variety mixtures was 

conducted in the 1994-95 season. 

These plots were treated in a 

manner highly similar to those 

described above, and have been 

discussed in more detail elsewhere 

(Zhan et al., 1998). Treatments were 

a complete factorial of three host 

treatments (pure stand of Madsen, 

pure stand of Stephens, and a 1:1 

mixture of Madsen:Stephens) and 

two inoculation treatments (natural 

and artificial) in a completely 

random design with three 

replications. One set of plots was 

naturally inoculated, while the 

1-May 

1-May 

22-May 

22-May 

12-Jun 

12-Jun 



90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

6-Feb 

6-Feb 

Cashup (MR) 

Stephens (S) 

Mixture 

27-Feb 

20-Mar 

Cashup (MR) 

W-301 (S) 

Mixture 

27-Feb 

20-Mar 

Disease Management Using Varietal Mixtures 113 

other was sprayed in November 

1994 with a mixture of 10 isolates to 

competitively exclude the highly 

diverse inoculum provided by 

outside ascospore showers. 

Results 

The Madsen/Stephens and 

Cashup/Stephens mixtures 

suppressed epidemic development 

below that of the more resistant 

component in each mixture (Figure 

1). In contrast, the mixtures 

containing the variety W-301 as the 

susceptible component performed 

less well, with the Cashup/W-301 

mixture showing no epidemic 

suppression relative to the mean of 

the component pure stands 

(Figure 1). 

Figure 1. Disease progress of septoria tritici blotch in naturally-occurring epidemics of pure stand varieties 

and 1:1 variety mixtures. MR = moderately resistant and S = susceptible. 

10-Apr 

10-Apr 

1-May 

1-May 

22-May 

22-May 

12-Jun 

12-Jun


114 

Greenhouse tests indicated that non-inoculated genotypes 

host diversity had a substantial comprising 35-40% of the 

impact on pathogenicity of M. population later in the season. In 

graminicola (Table 1). All populations contrast, natural inoculum has been 

derived from the mixtures produced estimated to result in hundreds of 

less disease on its component unique genotypes per m 

varieties in the greenhouse than the 

mean of the populations derived 

from the pure stand components in 

the field. 

Molecular analyses (Zhan et al., 

1998) have previously shown that the 

artificial inoculation used in the 

1994/95 season competitively 

excluded 97% of potential ascospore 

infections early in the season, though 

immigration and sexual 

recombination among inoculated 

and/or naturally occurring 

genotypes within plots resulted in 

2 

(McDonald et al., 1996). For the 

artificially-inoculated plots, 

epidemic progression for the 

Madsen/Stephens mixture was 

approximately midway between 

the two pure stands throughout the 

epidemic (Figure 2). By contrast, in 

the naturally-inoculated plots, 

epidemic progression in the 

mixture began midway between 

the pure stands, but became 

suppressed to near that of the 

moderately resistant variety as the 

season progressed (Figure 2). 

Table 1. Disease severity (percent of second leaf 

area covered by septoria tritici blotch lesions) 

caused by Mycosphaerella graminicola populations 

derived from single wheat varieties and variety 

mixtures in replicated field plots. 

Source of population 

Variety mixture Mixturea Pure standsb Madsen/Stephens 9.5 15.9 

Madsen/W-301 9.3 11.6 

Cashup/Stephens 10.8 13.4 

Cashup/W-301 6.6 9.0 

a Mean disease severity for populations derived from a 

given mixture when tested separately on each of the 

component varieties. For example, populations 

collected from the Madsen/Stephens mixture in the 

field were tested separately on Madsen and Stephens 

in the greenhouse. 

b Mean disease severity for populations derived from the 

component pure stands and tested on the same variety. 

For example, to compare with populations derived from 

the Madsen/Stephens mixture, populations collected 

from pure stands of Madsen in the field were tested on 

Madsen in the greenhouse and populations derived 

from pure stands of Stephens in the field were tested 

on Stephens in the greenhouse. 

percent disease 

percent disease 

100 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

25-Jan 

100 

90 

80 

70 

60 

50 

40 

Discussion 

Our results indicate that some 

variety mixtures suppress epidemic 

progression of septoria tritici blotch 

even in the absence of major genes for 

resistance. There are at least two 

plausible explanations for this result. 

First, the models of Jeger et al. (1981a) 

have shown that, in absence of host/ 

pathogen specificity, mixtures can 

decrease, increase, or have no effect 

on epidemic progression, depending 

on the relative levels of sporulation 

and infection frequency in the 

component varieties. Thus, 

differences between mixtures and 

pure stands in our experiment might 

be explained by differences in 

resistance components between 

cultivars, though we have not 

measured these components. 

Artificially inoculated plots 

Madsen 

Stephens 

Stephens/Madsen mixture 

15-Mar 4-May 23-Jun 

Naturally inoculated plots 

Madsen 

Stephens 

Stephens/Madsen mixture 

30 

20 

10 

0 

25-Jan 15-Mar 4-May 23-Jun 

Figure 2. Disease progress of septoria tritici blotch on a 

moderately resistant variety (Madsen), a susceptible 

variety (Stephens) and a 1:1 mixture of the two varieties 

in epidemics initiated from artificial inoculation with 10 

isolates or from naturally occurring inoculum.

A second explanation is that 

disruptive selection may reduce the 

fitness of pathogen populations 

that cycle between host genotypes 

in mixtures. The disruptive 

selection hypothesis is supported 

by the reduced fitness of M. 

graminicola populations derived 

from the variety mixtures as 

compared to the pure stands. It 

should be noted that the mean 27% 

fitness reduction of populations 

from mixtures that was found in 

our study is likely an 

underestimation, as disease 

severity in a monocyclic test 

accounts for only infection 

efficiency and lesion expansion, but 

not other fitness components such 

as sporulation rate or latent period. 

Additional support for the 

disruptive selection hypothesis is 

that variety mixtures suppressed 

epidemic development under 

conditions of natural inoculation, 

but not when artificially inoculated 

with a limited number of isolates. 

This result would be expected 

under the disruptive selection 

hypothesis, as there would be 

insufficient pathogen variation 

within the artificially inoculated 

plots for disruptive selection to 

occur. Such disruptive selection 

was earlier suggested to increase 

the efficacy of barley variety 

mixtures for control of powdery 

mildew (caused by Erysiphe 

graminis) (Wolfe et al., 1981) and to 

reduce the fitness of mildew 

genotypes that were able to 

overcome more than one major 

resistance gene in the mixtures 

(Chin and Wolfe, 1984). 

The levels of disease 

suppression contributed by our 

variety mixtures may not be 

sufficient as the sole control 

practice, but would certainly be 

useful in an integrated 

management program. In addition, 

we are currently more interested in 

the potential for varietal 

diversification to slow pathogen 

evolution towards increased 

virulence and/or aggressiveness 

(sensu Vanderplank, 1968) than we 

are for the immediate effects on 

epidemic progression. This is 

crucial in the Willamette Valley of 

Oregon, as there is evidence that 

even quantitative resistance to M. 

graminicola may erode in our 

environment (Mundt et al., 1999). 

Though not addressed in the 

research reported here, major genes 

for resistance may contribute 

substantially to control of septoria 

diseases in wheat variety mixtures. 

Our earlier studies showed that 

mixtures containing both a 

susceptible and a highly resistant 

variety provided greater disease 

control than other types of 

mixtures (Mundt et al. 1995). The 

subsequent “breakdown” of the 

high-level resistance in the variety 

Gene (Cowger et al., this volume) 

might be seen to increase the 

overall level of disease in such 

mixtures. On the other hand, 

mixtures of a virulent and avirulent 

pathogen isolate have been shown 

to reduce pycnidial production of 

M. graminicola very substantially 

(Halperin et al., 1996), which could 

greatly increase the value of 

“defeated” major genes in variety 

mixtures. 

Disease Management Using Varietal Mixtures 115 

In summary, there appears to be 

some potential for variety mixtures 

to suppress septoria blotch 

epidemics and to slow pathogen 

evolution. Currently available data 

are very scant, however, and 

substantially greater field 

evaluation is required to determine 

the short- and long-term value of 

the diversity approach for control 

of Septoria/Stagonospora diseases. 

References 





and wheat cultivars. Plant Pathol. 

44:838-847. 








Chin, K.M., and Wolfe, M.S. 1984. 

Selection on Erysiphe graminis in 

pure and mixed stands of barley. 

Plant Pathol. 33:535-546. 

DiLeone, J.A., Karow, R.S., Coakley, 

S.M., and Mundt, C.C. 1997. 

Biology and Control of Septoria 

Diseases of Winter Wheat in Western 

Oregon. Oregon State Univ. Ext. 

Serv. Crop Sci. Bull. 109. 17 pp. 

Fitt, B.D.L., and McCartney, H.A. 

1986. Spore dispersal in relation to 

epidemic models. Pages 311-345 in: 

Plant Disease Epidemiology, Vol. 1. 

K.J. Leonard and W.E. Fry, eds. 

McGraw-Hill, New York. 

Garrett, K.A., and Mundt, C.C. 1999. 

Epidemiology in mixed host 

populations (mini-review). 

Phytopathology 89:accepted 

pending revisions. 

Halperin, T., Schuster, S., Pnini- 

Cohen, S., Zilberstein, A., and 

Eyal, Z. 1996. The suppression of 

pycnidial production on wheat 

seedlings following sequential 

inoculation by isolates of Septoria 

tritici. Phytopathology 86:728-732.


116 

Jeger, M.J., Griffiths, E., and Jones, 

D.G. 1981a. Disease progress of 

non-specialised fungal pathogens 

in intraspecific mixed stands of 

cereal cultivars. I. Models. Ann. 

Appl. Biol. 98:187-198. 

Jeger, M.J., Jones, D.G., and Griffiths, 

E. 1981b. Disease progress of nonspecialised 

fungal pathogens in 

intraspecific mixed stands of cereal 

cultivars. II. Field experiments. 

Ann. Appl. Biol. 98:199-210. 

Kema, G.H.J., Sayoud, R., and van 

Silfhout, C.H. 1996. Genetic 












pathosystem. III. Comparative 



86:213-220. 

McDonald, B.A., Mundt, C.C., and 

Chen, R.S. 1996. The role of 

selection on the genetic structure 

of pathogen populations: Evidence 

from field experiments with 



Mundt, C.C. 1994. Use of host genetic 

diversity to control cereal diseases: 

Implications for rice blast. Pages 

293-307 in: Rice Blast Disease. S.A. 

Leong, R.S. Zeigler, and P.S. Teng, 

eds. CAB International, 

Cambridge, and the International 

Rice Research Institute, Manila. 

Mundt, C.C., and Leonard, K.J. 1986. 

Analysis of factors affecting 

disease increase and spread in 

mixtures of immune and 

susceptible plants in computersimulated 

epidemics. 




and Cowger, C. 1999. Population 

genetics and host resistance. Pages 

115-130 in: Septoria in Cereals: a 

Study of Pathosystems. Lucas, J.A., 

Bowyer, P., Anderson, H.M., eds. 

CABI Publishing, Wallingford, UK. 

Mundt, C.C., Brophy, L.S., and 

Schmitt, M.E. 1995. Choosing crop 

cultivars and mixtures under high 

versus low disease pressure: A 

case study with wheat. Crop Prot. 

14:509-515. 

Vanderplank, J.E. 1968. Disease 

Resistance in Plants. Academic 

Press, New York. 206 pp. 

Wolfe, M.S. 1985. The current status 

and prospects of multiline 

cultivars and variety mixtures for 

disease resistance. Annu. Rev. 


Wolfe, M.S., Barrett, J.A., and Jenkins, 

J.E.E. 1981. The use of cultivar 

mixtures for disease control. Pages 

73-80 in: J.F. Jenkyn and R.T. 

Plumb, eds. Strategies for the 

Control of Cereal Disease. Blackwell, 

Oxford. 






88:1330-1337.

Session 6C: Breeding for Disease Resistance 

Breeding for Resistance to the Septoria/Stagonospora 

Blights of Wheat 

M. van Ginkel and S. Rajaram 

Wheat Program, CIMMYT, El Batan, Mexico 

Abstract 

Genetic resistance remains the first line of defense against the septoria foliar blights, especially in developing countries. 

Resistance genes with major or minor effects may be either recessive or dominant. A few genes may be enough to confer 

resistance, as in the case of partial resistance. Additive gene effects contribute more to resistance than dominance effects. 

Among normally maturing semidwarf wheats possessing resistance, those carrying Rht2 may be more resistant to Septoria 

tritici than those with Rht1. In the case of Stagonospora nodorum, resistance of the flag leaf and of the spike may be at least 

partly under separate genetic control. 

Five confounding factors complicate selection for resistance: 1) maturity and plant height affect the expression of 

resistance; 2) the relationship between seedling and adult plant responses is highly inconsistent; 3) the correlation between 

disease response and yield loss is very variable; 4) there is interaction among fungal isolates on the leaf surface; and 5) it is 

essential to determine the implications of the existence of races for resistance breeding. 

Durability of resistance across years and locations is a particular concern, and examples of both erosion of resistance and 

stable resistance have been put forward. There is clear proof of differential variety by isolate interactions at the seedling stage 

and on adult plants in the field. However, almost without exception, the size of the interaction component is about a 

magnitude smaller than that of the main effects due to varieties and isolates. Recent molecular experiments on the genetic 

structure of S. tritici populations have found a lack of adaptation to the host genotype. 

The methodology applied at CIMMYT for pyramiding resistance genes in wheat includes utilizing proven resistance 

sources as parents, selecting for resistance using a shuttle breeding program between contrasting locations, and confirming 

resistance through global multilocation testing. The best resulting lines are fed back into the crossing program as parents. The 

first genepool exploited for resistance to S. tritici by CIMMYT breeders originated in Brazil and Argentina, followed by 

winter wheats and, subsequently, Chinese materials. New sources of resistance, such as highly promising synthetic wheats, 

are currently being exploited in combination with the previous sources. 

Globally the septoria diseases 

have increased in importance over 

the past decades, and as Walter 

Spurgeon Beach wrote in 1919: 

“The genus is the more worthy of 

study on account of its high 

economic importance.” The two 

main septoria blights addressed in 

this paper are caused by Septoria 

tritici and Stagonospora nodorum. 

However, inferences can be drawn 

for the septoria blights in other 

cereals, such as Septoria passerinii on 

barley. Several excellent overviews 

have been written on the genetics of 

resistance to the septoria diseases of 

cereals and on how to breed for 

such resistance (Shipton et al., 1971; 

King et al., 1983; Nelson and 

Marshall, 1990; Lucas et al., 1999; 

Eyal, 1999). Most of those reviews 

were published 10 years or more 

ago, but a great deal of the 

information they contain is still 

correct and relevant today. 

117 

This paper emphasizes some of 

the more recent literature (post 1990) 

on the genetics and breeding of 

resistance, and how these new 

insights may be applied in developing 

varieties that express durable 

resistance to the septoria blights.

118 

Session 6C — M. van Ginkel and S. Rajaram 

The Need for Resistance 

In most wheat production 

environments, although not in all, 

genetic resistance is the most 

economical approach to control 

fungal diseases. There are, however, 

two other control methods—cultural 

and chemical—that may be utilized. 

In the case of the septoria foliar 

blights, crop residues play a critical 

role in the over-seasoning of the 

pathogen and in supplying the 

primary inoculum for the 

subsequent cropping cycle. In recent 

years zero and reduced tillage 

practices have been gaining 

popularity for reasons ranging from 

the economics of production to 

protection of the environment, and 

the trend is likely to become 

stronger in the near term. Hence 

cultural control methods involving 

specific residue removal seem less of 

an option than a few decades ago. 

However, in the more distant future, 

we may once again see a 

contraction, particularly in the use 

of the zero tillage option, as the 

problems of excessive fungicide use 

and disease buildup both above and 

below the soil become more 

intractable. 

Chemical control will always 

need to be available as an option. In 

particular when conditions are 

unexpectedly conducive to 

disease—for example, due to 

excessive rainfall—a wellresearched 

chemical option must be 

close at hand. Under such 

circumstances chemical control may 

often be justified because it can 

avoid production losses of great 

economic value. 

Considering the above 

mentioned control options, 

breeding for resistance must 

remain the first line of defense, 

especially in developing 

countries. In such countries other 

options, while attractive in 

theory, often cannot be 

implemented in a timely fashion 

and/or the resources needed for 

their development and largescale 

application are lacking, 

even in an emergency. 

Where resistance is not 

effective, tolerance can be sought 

(McKendry and Henke, 1994a). 

Despite more than 25 years of 

interest in tolerance to the 

septoria blights, its mechanism(s) 

in general remains vague 

(Zuckerman et al., 1997). There is, 

however, little doubt that 

tolerance is widely available and 

operational in modern-day 

germplasm. 

Sources of Resistance 

Many sources of resistance to 

the septoria foliar blights, 

including some wild relatives of 

wheat, have been studied over 

the years. The interest in “alien 

sources” is not new; in the early 

part of this century, wild relatives 

resistant to the Septoria spp. were 

already being tested and 

identified (Beach, 1919; Mackie, 

1929). Some of those sources were 

reported in the official literature, 

while others were used in 

breeding programs and reported 

less in written form. 

Although grouping the 

sources of resistance based on 

origin or wheat class is to a 

certain extent arbitrary, commonly 

used classifications are: derived 

from South American (in particular 

Brazilian) sources, winter wheats, 

Chinese origin, and wild relatives 

of wheat. Some of the major 

sources confirmed by several 

authors are listed in Table 1. 

Table 1. Sources of resistance to Septoria tritici 

and Stagonospora nodorum confirmed by several 

authors. Generally only one key reference is given. 

Septoria tritici Reference 

Anza Wilson (1994) 

Bezostaya 1 Danon et al. (1982) 

Bobwhite Gilchrist et al. (1995) 

Bulgaria 88 Rillo and Caldwell (1966) 

Carifen Lee & Gough (1984) 

Colotana Danon et al. (1982) 

Fortaleza 1 Danon et al. (1982) 

Israel 493 Wilson (1979) 

Milan Gilchrist et al. (1995) 

Nabob Narvaez & Caldwell (1957) 

Oasis Danon et al. (1982) 

Seabreeze Rosielle & Brown (1979) 

Sheridan 

Synthetic wheats 

Danon et al. (1982) 

(some) May & Lagudah (1992) 

Tadinia Somasco et al. (1996) 

Tinamou Gilchrist et al. (1995) 

T. dicoccon Gilchrist & Skovmand (1995) 

T. speltoides McKendry & Henke (1994) 

T. tauschii Appels & Lagudah (1990); May 

& Lagudah (1992); McKendry 

& Henke (1994b) 

Veranopolis Rosielle & Brown (1979) 

Vilmorin 

Stagonospora 

nodorum 

Gough & Smith (1985) 

Aegilops longissima Ecker et al. (1990a) 

Atlas 66 Kleijer et al. (1977) 

Blueboy II Nelson (1980) 

Cotipora Bostwick et al. (1993) 

Frondoso Mullaney et al. (1982) 

Fronthatch Mullaney et al. (1982) 

Oasis Nelson (1980) 

T. monococcum Ma & Hughes (1993) 

T. speltoides Ecker et al. (1990b) 

T. tauschii Ma & Hughes (1993) 

T. timopheevii Ma & Hughes (1993) 

Inheritance of 

Resistance 

Resistance genes having major 

effects have been identified in 

wheat (Nelson and Marshall, 1990). 

They have been found to transmit

their resistance in either a recessive 

or dominant fashion (Eyal, 1999). 

However, in most cases, resistance 

appears dominant, with the F1 

from a cross between a resistant 

and a susceptible parent expressing 

an intermediate level of resistance 

that is more similar to that of the 

resistant parent. A few genes may 

be enough to confer resistance that 

will hold up in farmers’ fields 

(Dubin and Rajaram, 1996). While 

heritabilities tend to be only of 

moderate magnitude, progress in 

breeding for resistance is evident. 

Although the number of genes 

available may be quite high, 

accumulating a few key ones may 

be sufficient to achieve resistance. 

As has been shown for durable 

resistance to leaf rust (Singh et al., 

1991), several of the alleged 


S. tritici may also be controlled by 

only one or a just a few genes 

(Jlibene and El Bouami, 1995). It 

would seem that those components 

that are genetically different could 

be combined into the same genetic 

background by crossing. Once 

available, molecular markers will 

be of tremendous use for 

accumulating resistance to such 

environmentally sensitive diseases. 

The expression of S. tritici 

resistance was studied in T. tauschii 

accessions, synthetic wheats 

derived from them, plus 

derivatives of synthetic wheats 

crossed to common wheats. The 

results obtained all pointed to 

inheritance based on one or a few 

dominant genes (Appels and 

Lagudah, 1990; May and 

Lagudah, 1992). 

Chromosome 5D of T. tauschii 

contributed a high level of resistance 

to S. nodorum in a synthetic cross 

with a T. dicoccum line and in 

derived substitution lines 

(Nicholson et al., 1993). 

Chromosomes 5D, 3D, and 7D 

contributed resistance in decreasing 

order of importance. Aegilops 

longissima and Ae. speltoides were 

shown to contribute S. nodorum 

resistance based on two to four 

partially dominant to overdominant 

genes (Ecker et al., 1990a 

and b). Triticum timopheevii 

transmitted one S. nodorum 

resistance gene located on 

chromosome 3A to its progeny from 

a cross with a susceptible durum 

parent (Ma and Hughes, 1995). 

In most published accounts of 

quantitative analyses, additive gene 

effects or general combining ability 

(GCA) effects contributed more to 

resistance than dominance or special 

combining ability (SCA) effects (van 

Ginkel and Scharen, 1987; Bruno 

and Nelson, 1990; Danon and Eyal, 

1990; Wilkinson et al., 1990; Jonsson, 

1991; Jlibene et al., 1994). However, 

significant non-additive effects were 

often identified in the same studies. 

SCA effects tend to be an order of 

magnitude weaker than GCA 

effects. Indirectly Nelson and Fang 

(1994) confirmed these conclusions 

when they observed an absence of 

heterosis for components of S. 

nodorum resistance, indicating a 

general lack of over-dominance 

effects that enhance resistance. 

Jlibene et al. (1994) found a small 

cytoplasmic effect in a few of 

their crosses. 

Breeding for Resistance to the Septoria/Stagonospora Blights of Wheat 119 

Triticales were found not to be 

any more resistant than most 

wheats, and a range of reactions to 

both S. tritici and S. nodorum was 

observed (Scharen et al., 1990). 

Tritordeum amphiploids (doubled 

derivatives from crosses between 

Hordeum chilense and Triticum spp.) 

expressed the S. tritici resistance of 

the barley parent both as seedlings 

in greenhouse tests and adult 

plants in field trials (Rubiales et 

al., 1992). 

Tolerance to S. nodorum was 

shown to be a mechanism that is 

genetically different from (partial) 

resistance and involves several 

chromosomes (Rapilly et al., 1988). 

Distinct characters were identified 

within each of these two defense 

mechanisms. 

Although the introduction of 

alien cytoplasm from wild wheat 

relatives reduced partial resistance 

somewhat, it did increase tolerance 

as measured by reduced yield 

losses (Keane and Jones, 1990). 

Agronomic Traits 

and Resistance 

After a period in the 1960s and 

1970s of seemingly increased levels 

of disease susceptibility in the 

semidwarf wheats (Santiago, 

1970), modern semidwarf 

germplasm carrying high levels of 

resistance was subsequently 

identified. Many are now widely 

grown as commercial varieties. 

As in previous studies, 

Camacho-Casas et al. (1995) 

showed that it is possible to breed 

normally maturing semidwarf 

wheats if proper disease conditions

120 


are created during the selection 

process and attention is paid to 

achieving the desired maturity. 

Nevertheless, tall and/or late 

versions of similar isogenic lines 

tend to be less affected by the 

septoria/stagonospora blights than 

their shorter, earlier sister lines. 

The roles in conferring S. tritici 

resistance of the two most common 

dwarfing genes may not be the 

same (Baltazar et al., 1990). In the 

four crosses studied, the Rht2 

dwarfing gene tended to be 

associated more often with 

increased levels of resistance. 

Plants carrying Rht1 were more 

susceptible. 

In the case of S. nodorum, 

resistance of the flag leaf and of the 

spike may be at least partly under 

separate genetic control (Rosielle 

and Brown, 1980; Bostwick et al., 

1993; Hu et al., 1996). Resistance of 

the flag leaf was found to be coded 

for by genes on chromosomes 3A, 

4A, and 3B, while spike resistance 

was located on the same 

chromosomes and on 7A (Hu et al., 

1996). 

Determination 

of Resistance 

One of the most confounding 

factors in determining resistance to 

the septoria blights has been and 

continues to be the interaction 

between resistance and maturity 

and plant height, as mentioned 

above. Parlevliet (1990) describes 

how the ranking of resistance may 

even change dramatically, once 

these factors have been 

corrected for. 

Deviation from regression was 

proposed by van Beuningen and 

Kohli (1990) to correct for the 

confounding factors of heading and 

plant height. Loughman et al. 

(1994a) proposed a numerical 

classification approach that creates 

clusters of similar entries based on 

response patterns including disease 

reaction, maturity, and height. If 

proper checks are included, cluster 

analysis helps to identify resistant 

material. 

A second confounding factor in 

quantifying resistance is the 

relationship between seedling and 

adult plant responses. Somasco et 

al. (1996) showed that long-term 

resistance to S. tritici, such as that 

found in Tadinia (derived from the 

winter wheat Tadorna), was 

strongly expressed in both 

seedlings and adult plants. Kema 

and van Silfhout (1997) showed 

that not all isolates respond 

similarly to seedling and adult 

plant infection. 

Several studies have found that 

resistance to S. nodorum is 

expressed differently in seedlings 

than in adult plants (Koric, 1988; 

Arseniuk et al., 1991). These studies 

concluded that while only 

preliminary seedling data should 

be considered, subsequent adult 

plant screening is imperative. 

In a set of bread wheats and 

durum wheats, seedling response 

to a crude toxic extract of S. tritici 

produced a varietal ranking 

different from the adult plant 

reaction to field inoculation with a 

spore mixture of the same fungus 

(Harrabi et al., 1995). 

However, media containing 

crude extracts from grain inoculated 

with S. nodorum elicited a differential 

response that correlated well with 

field resistance or susceptibility of 

the spike (Keller et al., 1994). 

Resistant lines showed a higher 

percentage of embryo-forming callus 

in the presence of the extract. 

A third major confounding factor 

is the correlation between disease 

response and yield loss. Under field 

conditions visually observed 

symptoms of S. nodorum on the flag 

leaf or spike were not always well 

correlated to yield losses (Tvaruzek 

and Klem, 1994). Lack of 

consistently high correlations 

between S. nodorum disease scores 

and final yield loss motivated 

Walther (1990) to study a more 

extensive scoring method. When 

flag leaves of protected and nonprotected 

plots were scored on three 

dates around the middle of the 

epidemic, correlations rose to 0.73. 

Stagonospora nodorum severity 

scores on the flag leaf had the 

highest correlations with yield loss, 

followed by those on the flag leaf -1 

(Walther and Bohmer, 1992). Spike 

infection was poorly correlated with 

yield. Heritability of disease 

variables could be further increased 

if plant height and maturity were 

corrected for, with heritability values 

for weighted assessments 

reaching 0.89. 

The practice of using detached 

leaves to determine resistance 

appears to have diminished in the 

past decade. Most work is now 

carried out on seedlings and adult 

plants in the greenhouse or the field.

Durability of Resistance 

Durability of S. nodorum 

resistance within a crop cycle 

decreased with leaf age, and the 

older lower leaves proved more 

susceptible than the younger upper 

leaves (Jonsson, 1991). Due to this 

effect, late maturing germplasm is 

often wrongly considered more 

resistant than early maturing lines. 

Thus it is crucial to measure 

resistance at the same adult 

growth stage. 

More debated than durability 

within a crop cycle is the issue of 

durability of resistance across years 

and locations. Johnson in his 1992 

general review of breeding for 

disease resistance highlights the 

difficulty of establishing the 

presence of differential hostpathogen 

interaction in the septoria 

foliar blights. He compares data 

gathered by the Eyal group (Eyal et 

al., 1973) with those of van Ginkel 

(van Ginkel and Scharen, 1985) and 

concludes that even the 

interpretation of quite similar data 

may differ. In practice, he 

concludes, no unequivocal demise 

of varieties due to truly differential 

races of the septoria foliar blights 

has been reported. 

The increase of disease severity 

over time on the same variety has 

been noted in the Netherlands, 

Australia, Israel (Jorgensen and 

Smedegaard-Petersen, 1999), and 

the USA (Mundt et al., 1999). 

However, it was not unequivocally 

shown whether this was due to an 

evolution of aggressiveness in the 

pathogen population or due to 

differential host-pathogen 

interaction based on the evolution 

of new virulence patterns. Mundt et 

al. (1999) conclude that the 

cultivation of susceptible hosts will 

result in selection for 

aggressiveness. In Germany several 

varieties were shown to retain their 

resistance to isolates of S. nodorum 

collected annually from all over the 

former East Germany for more than 

10 years, except for small variations 

over years due to specific weather 

conditions (Walther, 1993). 

Clear proof of differential 

variety by isolate interaction at the 

seedling stage was presented by 

Kema et al. (1996). However, as in 

previous studies by this group and 

others, the size of the interaction 

component was about a magnitude 

smaller than that of the main effects 

due to varieties and isolates. In a 

later monocyclic field experiment, 

Kema and van Silfhout (1997) 

applied isolates specifically selected 

for their virulence differences at the 

seedling level, to adult plant plots. 

Again, small but significant 

interactions between isolates and 

varieties were apparent in this 

monocyclic situation. The 

significant interaction effect was 

largely due to two of the three 

isolates interacting differentially 

with two of the 22 varieties tested. 

Recent work on Kenyan isolates 

indicated that variety by isolate 

interaction in the field, while 

present, was small, with the 

interaction component accounting 

for only about 5% of the main 

effects (Arama, 1996). 


Recent experiments on the 

genetic structure of S. tritici 

populations in response to host 

differences found a total lack of 

evidence for adaptation to the host 

genotype (McDonald et al., 1996). 

Different hosts had no differential 

effects on the dynamics of the 

pathogen population. On the other 

hand, Ahmed et al. (1996) found 

that susceptible varieties selected 

for more aggressive pathogen 

populations. However, the 

virulence levels of the pathogen 

isolates were associated with the 

variety of origin. 

Varietal mixtures of resistant 

and susceptible varieties have met 

with mixed success. Recent 

comparisons by Loughman et al. 

(1994b) of pure lines and mixtures 

did not find that mixtures have any 

advantage when it comes to 

durability of resistance. 

Interaction among isolates on 

the leaf, which can enhance or 

reduce expected disease severities 

(Eyal, 1992; Gilchrist and 

Velazquez, 1994), adds another 

component to the mix of virulence 

and aggressiveness. 

The implications for resistance 

breeding of the above findings on 

variety by isolate interactions 

remain to be tested further in real 

agricultural settings. However, it 

does appear that the response of 

the septoria/stagonospora foliar 

blights to their hosts cannot 

compare to the highly volatile 

population dynamics we see in the 

wheat rusts.

122 


It is essential to determine the 

practical relevance of the presence of 

races of the septoria foliar blights 

when applying a resistance breeding 

strategy. Indeed, the importance of 

this topic cannot be overstated. New 

insights into the genetic structure of 

the pathogen population and its 

dynamics, especially as supported 

by biotechnological tools, may 

increase our understanding 

significantly in the near term. 

Breeding for Resistance 

at CIMMYT 

The methodology applied at 

CIMMYT for breeding for disease 

resistance in wheat has been 

outlined in previous publications, 

including the proceedings of several 

international septoria workshops 

(Mann et al. 1985; van Ginkel and 

Rajaram, 1989; van Ginkel and 

Rajaram, 1993; Gilchrist et al., 1995; 

van Ginkel and Rajaram, 1995). The 

methodology consists of three key 

components: utilizing proven 

resistance sources as parents, 

selecting for increased resistance in 

a shuttle breeding program, and 

confirming resistance by 

multilocation testing. The best 

identified lines are fed back into the 

crossing program as parents to 

further accumulate resistance, 

bringing the process full circle. 

The materials that provide the 

best resistance are made available 

by CIMMYT to all collaborators 

around the world who request 

them. Lists of such materials are 

published periodically (Gilchrist, 

1994). Gilchrist et al. (this volume) 

have provided a new overview of 

lines found to be consistently 

resistant by CIMMYT researchers. 

Every year CIMMYT 

distributes to collaborators the 

newest wheat lines that combine S. 

tritici resistance with a full 

“agronomic package,” including 

adaptation to high rainfall 

environments, superior yield, a 

certain level of resistance to other 

prevalent diseases such as the rusts 

and scab, and acceptable grain 

quality. 

The parental stocks emphasized 

in developing these lines have a 

relatively long history of proven 

resistance in many locations 

around the world. The first 

genepool exploited for resistance to 

S. tritici by CIMMYT breeders was 

that represented by such lines as 

IAS20 from Brazil and Klein Atlas 

from Argentina. The Tinamou line 

is an example of a widely adapted, 

resistant line that was developed 

from those resistance sources. Then 

followed the winter wheats, in 

particular those from the former 

USSR, such as Aurora. Examples of 

elite lines emanating from that 

work are the group of Bobwhite 

lines, such as the cultivar 

PROINTA Federal and the Milan 

lines, which have shown strong 

disease resistance throughout the 

world, including in the hotspots of 

eastern Africa and the Southern 

Cone of South America (Kohli, 

1995; Dubin and Rajaram, 1996). 

Subsequently, Chinese materials, 

such as the Ning, Shanghai, and 

Suzhoe series, plus other varieties 

from China, were heavily crossed 

by CIMMYT breeders. A key 

resistant line that resulted from 

that effort was Catbird. This 

history is discussed in more detail 

by Gilchrist et al. (this volume). 

New sources of resistance, such 

as highly promising synthetic 

wheats, are currently being 

exploited. CIMMYT’s Wide Crosses 

Program produces synthetic wheats 

by crossing CIMMYT elite durum 

wheats to accessions of Aegilops 

squarrosa (syn. Triticum tauschii and 

Ae. tauschii). The resulting triploid 

seedlings are treated with colchicine 

to double the number of 

chromosomes, resulting in manmade 

(hence “synthetic”) hexaploid 

bread wheats. Certain of those 

wheats have shown remarkable 

levels of S. tritici resistance, and low 

severities bordering on immunity 

have also been observed. Since 

synthetic wheats are relatively easy 

to cross with common wheats, their 

resistance can be readily 

introgressed into agronomically 

acceptable plant types, and 

combined with other resistances. 

CIMMYT’s breeding 

methodology emphasizes regularly 

exposing segregating materials to 

disease epidemics. Since the 

breeding program also targets 

resistance to several other diseases 

besides S. tritici, straw is used as the 

source of primary inoculum. Straw 

residues may carry inoculum for tan 

spot, fusarium head scab, fusarium 

foliar blight, and different species of 

bacteria in addition to the septorias. 

In special cases and in specific 

studies, pure liquid S. tritici spores 

are applied. 

CIMMYT applies a shuttle 

breeding methodology in which 

materials are alternately grown in a 

high rainfall site in the Mexican 

highlands (Toluca) and an irrigated 

site in northwestern Mexico (Cd. 

Obregon). As a result, the material

targeted for S. tritici-prone regions 

is exposed to the disease 3-4 times 

during the segregating phase when 

grown in Toluca. During the 

selection process, selection 

intensity is increased as the 

segregating populations are 

advanced. At the end of the shuttle 

breeding process, all homozygous 

lines are exposed for two 

additional cycles at three sites in 

the high rainfall Mexican 

highlands: Toluca, Patzcuaro 

(Gomez and Gonzalez, 1987), and 

El Tigre. 

Shuttle breeding is followed by 

multilocation testing at key 

locations around the world through 

a network of cooperators. The 

global data allow truly outstanding 

material (see Gilchrist et al., these 

proceedings) to be identified and 

used as new parents in the ongoing 

process of recombining genetically 

different sources of resistance, and 

they also offer the prospect of 

combining different resistance 

mechanisms. 

Future work will concentrate on 

combining accumulated resistances 

that are based on different genes 

and/or different resistance 

mechanisms, with superior yield, 

scab resistance, shattering 

tolerance, and industrial quality. 

Conclusions 

Several conclusions in regard to 

the impact of our increased 

understanding of resistance on 

related breeding aspects can be 

drawn from the combined research 

of the past decade: 

1. There are many sources of genetic 

resistance available that have 

either been shown to be different 

or seem to behave differently. 

Many of those resistances have 

proven to be quite stable. 

2. Seedling data at best are an 

indication of adult plant 

resistance, and testing adult 

plants in a field situation appears 

crucial. 

3. A variety is rarely replaced 

solely or primarily because it 

succumbs to one of the 

septoria/stagonospora blights. 

4. The relative role of virulence and 

aggressiveness in the field may 

soon be elucidated using 

molecular tools in combination 

with the ability to cross among 

isolates. The outcome should 

have direct impact on breeding 

strategy. 

5. The diversity of isolates at the 

field level makes gaining a 

deeper understanding of 

interactions among these isolates 

of paramount importance. The 

breeder needs to take this into 

consideration when planning to 

artificially inoculate, or rely on 

multisite testing. 

6. Multilocation confirmation of 

advanced lines remains a 

necessity, while the debate on 

possible specificity continues. 


While several of these exciting 

issues remain in debate, advances 

in breeding for resistance to the 

septoria/stagonospora pathogens 

have not ceased. Breeders have 

continued to produce varieties with 

higher yields, better industrial 

quality, and improved resistance to 

multiple diseases. 

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Breeding for Resistance to Septoria and 

Stagonospora Blotches in Winter Wheat in 

the United States 

G. Shaner 

Department of Botany and Plant Pathology, Purdue University, 

West Lafayette, IN, USA 

This report will concentrate on 

resistance breeding efforts in the 

winter wheat region of the United 

States, where leaf blotch, caused by 

either Septoria tritici or Stagonospora 

nodorum, has been a chronic 

disease. Leaf blotch has been a 

recognized problem in the eastern 

soft winter wheat region of the US 

for more than 50 years. Historically, 

Stagonospora nodorum was the major 

pathogen in the southeastern US 

and Septoria tritici was the major 

pathogen in the north-central 

regions. Since the mid 1980s, 

however, S. nodorum has been at 

least as damaging in the northcentral 

region as S. tritici. 

The Purdue University-USDA 

small grain improvement program 

provides an example of efforts to 

manage leaf blotch by use of 

genetic resistance. During the mid 

1950s, wheat breeders began to 

incorporate resistance to S. tritici 

into adapted soft red winter wheat 

cultivars. At that time, S. tritici was 

clearly the dominant leaf blotch 

pathogen. The primary sources of 

resistance were wheat cultivars 

from South America, e.g. Bulgaria 

88, Sao Sepe, and Sudeste. 

Eventually, most effort 

concentrated on Bulgaria 88 as the 

source of resistance. Cultivars 

Oasis and Sullivan, released in 1973 

and 1977, respectively, carried this 

resistance (Patterson et al., 1975; 

1979). When Oasis or Sullivan are 

inoculated at the adult plant stage 

in the greenhouse with spores of S. 

tritici, they are highly resistant. 

Infection results in small chlorotic 

flecks, with little or no chlorosis 

and no formation of pycnidia. 

Resistance in these cultivars 

segregates as a single, dominant 

Mendelian factor when they are 

crossed to a susceptible cultivar. 

Although Oasis derived its 

resistance to S. tritici mainly from 

Bulgaria 88, it evidently carried 

additional factors for resistance to 

S. nodorum because it exhibited a 

degree of resistance and performed 

well in areas of the southeastern US 

where this species was the 

dominant leaf spotting pathogen. 

This additional resistance may 

have resulted from the fact that 

selection for resistance in Indiana 

was entirely in the field under 

conditions of natural infection, and 

there may have been more S. 

nodorum present than was 

suspected. 

Since the latter half of the 1980s, 

S. nodorum has emerged as the 

dominant leaf spotting pathogen in 

Indiana (Shaner and Buechley, 

1995). This shift in pathogen 

populations has evidently occurred 

throughout the north central region 

127 

of the US, and leaf blotch must now 

be regarded as a complex involving 

both S. tritici and S. nodorum. In 

more southern regions, S. nodorum 

continues to be the major leaf 

spotting pathogen. 

Management of this disease 

complex by genetic resistance 

requires resistance to both 

pathogens. Despite at least 50 years 

of effort in breeding for resistance 

to leaf blotch, progress has been 

modest. Evidence for this 

conclusion comes from descriptions 

of cultivars developed in this 

region and from direct observation 

of many cultivars in field trials. 

An estimation of the degree of 

resistance available in currently 

available cultivars of soft red 

winter wheat can be obtained from 

data collected in statewide wheat 

performance trials conducted each 

year in Indiana. For many years, 

entries in this trial have been 

evaluated for disease. Leaf blotch is 

encountered every year to some 

degree in Indiana wheat fields, but 

at varying severity. For the period 

1973–91, leaf blotch symptoms 

reached the flag leaf of susceptible 

cultivars within 26 days of heading 

in 10 of the 19 years (Shaner and 

Buechley, 1995).

Session 6C — G. Shaner 

128 

An examination of leaf blotch 

severity data from 1986 through 

1996, collected from two locations 

in Indiana (Tippecanoe and 

Daviess Counties), can be used to 

estimate progress in development 

of cultivars with resistance to this 

disease complex. The number and 

identity of entries in these trials 

varied from year to year. Typically, 

a cultivar would be included for 

several consecutive years, but not 

for the full period covered by these 

trials. Each year, the trial included 

most cultivars of soft red winter 

wheat offered for sale in Indiana 

and adjacent states. The cultivars 

Arthur and Caldwell were 

included in every trial as long-term 

checks. Severity of leaf blotch in 

these trials was estimated using a 0 

to 9.5 scale, modified from one 

developed at CIMMYT (Shaner and 

Buechley, 1995). This scale is 

reproduced here as Table 1 for 

convenient reference. The ratings of 

leaf blotch severity discussed here 

were made when wheat was in the 

early to mid dough stage of 

development. 

Table 1. Leaf blotch severity scale for wheat. 

There are several ways 

that the question of 

improvement in resistance to 

leaf blotch can be 

investigated using data from 

these trials. If the general 

level of resistance among 

cultivars increased over the 

14-year period, then the trial 

mean leaf blotch severity, 

based on all cultivars, 

should decline relative to the 

severities for the check 

cultivars. Among the 16 

trials, trial means ranged 

from 5.4 to 9.2, reflecting 

variation among years in the 

suitability of weather for leaf 

blotch development. This 

variation in trial means was 

closely followed by the 

values for the two long-term 

check cultivars, Arthur and 

Caldwell. The trial mean 

was always less than the 

severity for Caldwell and 

usually less than the severity 

for Arthur, but there was no 

evidence for a greater 

disparity between the trial 

mean and the checks over 

Severity 

10 

9 

8 

7 

6 

5 

4 

Mean 

Arthur 

Caldwell 

86 PAF 

87 PAF 

89 PAF 

90 PAF 

90 DAV 

91 PAF 

9 DAV 

93 PAF 

93 DAV 

94 PAF 

94 DAV 

96 PAF 

96 DAV 

97 DAV 

98 DAV 

99 PAF 

Trial 

Figure 1. Trial means and means for check cultivars 

Arthur and Caldwell for leaf blotch ratings, 1986 

through 1999, at two locations in Indiana. PAF = 

Purdue Agronomy Farm (Tippecanoe County); DAV = 

Daviess County. 

time (Figure 1). The conclusion 

from this is that the newer cultivars 

are not more resistant collectively 

than those included in trials during 

earlier years, as represented by the 

two check cultivars. 

If only a few cultivars in a trial 

had substantially improved 

resistance, then the mean of all 

entries in that trial might not reflect 

this improvement, but the standard 

deviation of cultivar means should 

be greater than in trials lacking 

exceptionally resistant cultivars. If 

there has been progress in 

Range in percent severity on indicated leaf 

Scale value Flag Flag-1 Flag-2 Flag-3 Mean severityx 1 0-5 0.1 

2 5-20 2.9 

3 20-40 8.1 

4 1-10 40-70 15.6 

5 0-1 10-25 70-90 25.5 

6 1-10 25-75 90-100 37.8 

7 10-50 75-100 100 52.3 

8 1-20 50-90 100 100 69.3 

9 20-90 90-100 100 100 88.5 

9.5 90-100 100 100 100 99.1 

x Mean severity is the average for the four leaves, based on midpoint values for each range. Mean severity (P) can be 

calculated from the scale value (S) according to: P = -0.38253 – 0.69435 S + 1.17499 S2 (R2 = 0.999).

development of cultivars resistant to 

leaf blotch, then the variance of 

cultivar means should be seen to 

increase over the years. Plotting trial 

means and standard deviations over 

time revealed no tendency for the 

standard deviation to increase with 

time or to vary with the trial mean 

(Figure 2). 

Examination of data from 

individual trials may reveal to what 

extent resistance is expressed under 

conditions of severe, moderate, or 

mild disease pressure. Results from 

three trials are presented here for 

illustration. The trial with the 

greatest severity of leaf blotch was 

in Daviess County during 1990. The 

trial mean severity was 9.2. The 

cultivars with the least disease in 

this trial had a rating of 8. Thus, 

Severity 

10 

8 

6 

4 

2 

0 

Breeding for Resistance to Septoria and Stagonospora Blotches in Winter Wheat in the United States 129 

Mean 

St dev 

86 PAF 

87 PAF 

89 PAF 

90 PAF 

90 DAV 

91 PAF 

9 DAV 

93 PAF 

93 DAV 

94 PAF 

94 DAV 

96 PAF 

96 DAV 

97 DAV 

98 DAV 

99 PAF 

Trial 

Figure 2. Mean and standard deviation of leaf blotch 

severity on wheat in cultivar trials from 1986 through 

1999 at two locations in Indiana. 

8 

;; yy 

6 

;; yy ;; yy 

4 

;; yy ;; yy ;; yy ;; yy ;; yy ;; yy ;; yy 

2 

;; yy 

0 

;; yy ;; yy ;; yy ;; yy ;; yy ;; yy 

4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 

Severity class 

Figure 4. Frequency distribution of mean leaf blotch 

severities on wheat cultivars evaluated during 1993 

in Tippecanoe County, Indiana. 

Number of entries 

under conditions of great disease 

pressure, symptoms progressed to 

the flag leaves of all cultivars 

(Figure 3). The entire range in 

resistance was confined to the 

degree of flag leaf area that was 

blighted. All lower leaves were 

completed destroyed by leaf blotch. 

Mean leaf blotch severity was 

very low in the trial conducted in 

Tippecanoe County during 1993 

(Figure 4). The range among 

cultivar severity means was 

somewhat greater than in the 

previous example, because severity 

values were not truncated by the 

maximum possible value. The most 

severely affected cultivars showed 

only a few lesions on the flag leaf. 

On most of the cultivars, leaf blotch 

was at most only 10% on leaf F-1. 



15 

The trial conducted during 1997 

in Daviess County represents 

moderately severe disease pressure. 

The trial mean was 7.8 (Figure 5). 

Blotch symptoms reached the flag 

leaf on fewer than half of the 

cultivars in this trial, but the 

cultivars with the least amount of 

disease had symptoms on leaf F-1. 

Regardless of overall disease 

pressure, the range in leaf blotch 

severity among cultivars within a 

trial was not great. 

Analysis of these field trial data 

provides no evidence for substantial 

increases in resistance in a region of 

the United States where leaf blotch 

is a chronic and often severe disease 

of wheat. At best, a resistant cultivar 

will hold symptom development 

back by a few days on the flag and 

flag-1 leaves. 

10 

5 

0 

4 4.5 5 5.5 

;; yy ; y ; 

;; yy; 

y; 6 6.5 7 7.5 8 8.5 9 9.5 

Severity class 

; ;; yy 

;; yy 

;; yy 



in Daviess County, Indiana. 

20 ;; yy 

15 

10 ;; yy ;; yy 

5 ;; yy ;; yy ;; yy 

0 

;; yy ;; yy ;; yy ;; yy 

4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 

Severity class;; 



in Daviess County, Indiana. 

y 

y 

y

Session 6C — G. Shaner 

130 

Another approach to 

determining progress in breeding 

winter wheat for resistance to leaf 

blotch is to examine cultivar 

registrations in the journal Crop 

Science over a period of years. 

Registrations for 131 wheat 

cultivars were published in 

volumes 28-39, of which 96 were 

for winter wheat. Of these winter 

wheat cultivars, 25 were reported 

to have some degree of resistance 

to S. tritici or S. nodorum and 2 were 

reported to be susceptible. For the 

other 69 cultivars there was no 

mention of reaction to either of 

these pathogens. The summary for 

winter wheat cultivars includes 

both hard and soft, and red and 

white classes, covering the eastern 

portion of the US, the Great Plains, 

and the Pacific Coast states. 

Because leaf blotch has historically 

been a greater problem in the 

eastern region of the US, data were 

summarized for this region. Of 39 

wheat cultivars developed in the 

eastern soft wheat region of the US, 

15 were described as having some 

resistance, none were described as 

susceptible, and there was no 

mention of reaction for 24 cultivars. 

The absence of any comment about 

reaction to leaf blotch is interesting, 

because for many other wheat 

pathogens and pests (e.g. rusts, 

powdery mildew, viruses, Hessian 

fly), the registration articles 

commonly documented 

susceptibility as well as resistance. 

Of the 15 cultivars described as 

being resistant, 12 were described 

as having resistance to S. nodorum, 

7 of which were described as 

having resistance to S. tritici as 

well. The other three cultivars were 

described as being resistant only to 

S. tritici. 

An association has long been 

noted between tall stature, late 

maturity, and resistance to leaf 

blotch caused by either S. tritici or 

S. nodorum (Camacho-Casas et al., 

1995; Scott et al., 1982). Late 

maturity and tall stature per se may 

confer a significant degree of leaf 

blotch in such cultivars. Where leaf 

blotch is the greatest threat in 

North America, the eastern soft 

wheat region, breeders have 

emphasized development of short 

(90 to 100 cm), early maturing 

cultivars, as a way to reduce risk 

from rust infection, to permit grain 

filling before the excessive hot and 

humid conditions of summer, and 

to permit double-cropping with 

soybeans. The desired standards of 

early maturity and short stature 

may be an important reason for the 

lack of progress in achieving 

adequate levels of resistance to the 

leaf blotch pathogens. 

Hectares of soft wheat 

production in the eastern US have 

been declining for many years. 

Poor yields and poor grain quality 

because of disease have been a 

major reason for the abandonment 

of wheat production by many 

farmers. Unless greater degrees of 

resistance can be bred into highyielding, 

early-maturing, shortstatured 

wheat cultivars, this 

downward trend in production will 

likely continue. 

References 

Camacho-Casas, M.A., W.E. 

Kronstad, and A.L. Scharen. 1995. 

Septoria tritici resistance and 

associations with agronomic traits 

in a wheat cross. Crop Sci. 35:971- 

976. 

Patterson, F.L., Roberts, J.J., Finney, 

R.E., Shaner, G.E., Gallun, R.L., 

and Ohm, H.W. 1975. Registration 

of Oasis wheat. Crop Sci. 15:736- 

737. 

Patterson, F.L., Shaner, G.E., Huber, 

D.M., Ohm, H.W., Finney, R.E., 

Gallun, R.L., and Roberts, J.J. 1979. 

Registration of Sullivan wheat 

Crop Sci. 19:297. 

Scott, P.R., Benedikz, P.M., and Cox, 

C.J. 1982. A genetic study of the 





Shaner, G., and Buechley, G. 1995. 

Epidemiology of leaf blotch of soft 

red winter wheat caused by 

Septoria tritici and Stagonospora 

nodorum. Plant Disease 79:928-938.

Septoria tritici Resistance of Wheat 

Cultivars at Different Growth Stages 

M. Díaz de Ackermann, 1 M.M. Kohli, 2 and V. Ibañez1 1 INIA La Estanzuela, Colonia, Uruguay 

2 CIMMYT Regional Wheat Program, Uruguay 

Abstract 

Nine wheat cultivars planted in the greenhouse were inoculated with a mixture of three isolates of Septoria tritici at 

four different growth stages. The first evaluation, done six weeks after inoculation, showed that the facultative wheats at 

growth stage (GS) 39 (flag leaf ligule just visible) and spring wheats at GS 65 (flowering halfway complete) reached the 

highest levels of infection, with two exceptions, cvs E. Pelón 90 and P. Oasis. In the second evaluation a week later, the 

highest level of infection was reached when facultative wheats were inoculated at GS 32-33 (stem elongation-first node 

detectable) and spring wheats at GS 39 (flag leaf ligule just visible). In both evaluations, the effects of cultivars, seeding 

date/GS at inoculation, and the interaction between cultivars and GS at inoculation were significant. Septoria tritici 

susceptibility increased with the age of the plants. The increase in the level of infection was significantly lower in cv P. 

Superior (Bobwhite), indicating a certain level of adult plant resistance. 

Wheat is an important crop in the 

western region of Uruguay, where it 

is grown for grain and forage 

(double purpose) in the mixed 

farming system, or solely for grain 

production. Among diseases present 

in the country, Septoria tritici leaf 

blotch is one of the most important, 

and it can be particularly severe 

during the wheat-growing season in 

this temperate high rainfall 

environment. The wide range of 

planting dates from May (or even 

earlier for double purpose crops) to 

August determines the growth stage 

(GS) at the time of primary infection, 

later in the fall or in early spring. 

Facultative wheats, sown in the fall, 

are infected very early (seedling 

stage) or at the beginning of spring 

(boot stage), depending on the year. 

Spring wheats, sown later than the 

facultative types, are exposed mainly 

to spring infections. 

Reduced disease severity 

associated with tall plant stature and 

late maturity has been observed 

(Danon et al., 1982; Eyal and Talpaz, 

1990; van Beuningen and Kohli, 

1990; Tavella, 1978). However, the 

relationship between the resistance 

expressed at the seedling stage and 

the adult plant stage, or vice versa, 

is not fully understood. Kema and 

van Silfhout (1995) found 

significant correlations for one of 

three isolates inoculated on 22 

wheat cultivars at the seedling and 

adult plant stages. On the other 

hand, Arama, Parlevliet, and van 

Silfhout (1994) described three 

types of resistance: resistance only 

in seedling (seedling resistance), 

resistance only in adult plant (adult 

plant resistance), and resistance in 

both seedling and adult plant 

(overall resistance). 

The objective of this study was 

to determine the level of resistance 

in nine wheat cultivars, 

representing different reactions to S. 

tritici in the field, at different 

growth stages and under controlled 

conditions. 


131 

Nine wheat cultivars with 

different growth habits and field 

reactions to Septoria tritici were 

planted in three pots each, five 

plants per pot, on four seeding 

dates: 28 April . , 16 May . , 31 May . , 

and 27 June 1995. The pots 

measured 29 and 20 cm in their 

upper and lower diameters, 

respectively, and 20 cm in height. 

The cultivars’ growth habit, 

progenitors, and field reaction to S. 

tritici are presented in Table 1. The 

concentration of S. tritici spore 

suspension was adjusted to 106 conidia per ml, with the aid of a 

hemacytometer. The cultivars were 

inoculated with a mixture of three 

isolates (26S, 4407, and E. Federal) 

on 17 July, at the growth stages 

(Zadoks et al., 1974) indicated in 

Table 2. The selected isolates were 

characterized by Diaz de 

Ackermann et al. (1994). The plants 

were kept in a humid chamber until 

20 July. Due to the delayed

Session 6C — M. Díaz de Ackermann, M.M. Kohli, and V. Ibañez 

132 

appearance of symptoms, two 

evaluations were done, the first 

on 28 August . and the second on 

5 September. 

The infection was scored as 

percent of leaf area affected by 

the disease, on two tillers per 

plant and five leaves per tiller. 

Transformed data (Loge +0.5) for 

the flag leaf, F-1, and F-2, as 

well as the average of the three 

leaves, were analyzed using 

SAS GLM procedure (Version 

6.12; SAS Institute, Cary, NC). 

Infection on the lower two 

leaves was not included in this 

analysis due to many missing 

values. 

Results and 

Discussion 

The analysis of variance 

(ANOVA) for each leaf and the 

average of the three leaves 

showed significant differences 

between cultivars and seeding 

dates, as well as significant 

interaction between seeding dates 

and cultivars in both evaluations. As 

the results were similar for 

individual leaves and the average of 

the three top leaves, only data for 

the latter are presented (Table 3). 

Differences among cultivars 

were found on the first two seeding 

dates (28/04 and 16/05) during the 

first evaluation, and on the 

intermediate dates (16/05 and 31/ 

05) during the second evaluation. 

All the cultivars except B. 

Charrúa showed different infection 

levels on different seeding dates at 

first evaluation. This interaction is 

explained by the cultivars’ different 

Table 1. Cross, growth habit and field reaction to Septoria tritici of nine wheat cultivars. 

Cultivar Cross Growth habit Reaction 

E. Cardenal Veery#3 Spring S1 INIA Mirlo Car 853/Coc//Vee#5/3/Ures Spring R 

E Pelón 90 Kavkaz/Torim73 Spring R-MR 

ProINTA Superior Bobwhite Spring MR 

ProINTA Oasis Oasis/Torim Spring S 

E. Federal E.Hornero/CNT8 Facultative MR 

E Halcón Buck6/MR74507 Facultative MR 

Buck Charrúa RAP/RE//IRAP/3/LOV/4/RAP/RE//IRAP Facultative R 

LE 2196 E. Jilguero/ND526 Facultative R 

1 S: susceptible, R: resistant, MR: moderately resistant. 

Table 2. Growth stages of spring and facultative wheat varieties at time of inoculation. 

Seeding date 28/04 16/05 31/05 27/06 

Spring wheats 65 39 30-31 22-23 

Facultative wheats 39 32-33 30 24-25 

Table 3. Average level of infection of top three leaves, comparison among date of seeding (small 

letter) and cultivars (capital letter). Evaluation August 28th and September 5th . 

Sowing date 28/04 16/05 31/05 27/06 

GS Facultative 39 32/33 30 24/25 

GS Spring 65 39 30/31 22/23 

Cultivar 1st . eval 1st . eval 2nd . eval 1st . eval 2nd . eval 1st . eval 2nd . eval 

E.Cardenal 11.65 aA 3.81 bA 46.24 aA 0.16 c 3.57 bA 0.00 c 0.45 c 

I. Mirlo 1.98 aCD 2.17 aAB 23.93 aB 0.00 b 1.96 bB 0.00 b 0.66 c 

E. Pelón 90 1.32 aDE 2.20 aAB 16.86 aC 0.02 b 1.76 bB 0.00 b 0.19 c 

P. Superior 2.92 aC 1.50 bB 8.14 aD 0.00 c 1.86 bB 0.00 c 0.11 c 

P. Oasis 1.79 bCD 4.25 aA 27.22 aB 0.26 c 2.18 bB 0.02 c 0.44 c 

E. Federal 7.64 aB 3.17 bA 19.15 aC 0.00 c 0.50 bD 0.00 c 0.43 b 

E. Halcón 1.25 aE 0.23 bC 3.61 aE 0.03 b 1.13 bC 0.00 b 0.17 c 

B. Charrúa 0.14 aE 0.03 aC 2.91 aE 0.00 a 0.56 bCD 0.00 a 0.44 b 

LE 2196 1.66 aDE 0.22 bC 6.65 aD 0.03 b 1.23 bB 0.00 b 0.33 c 

Average 3.37 1.95 17.19 0.06 1.64 0.00 0.36 

behavior on the different seeding 

dates/GS at inoculation. Early 

seedling infection demonstrated 

higher sensitivity for detecting 

differences among cultivars. 

During this evaluation, the 

facultative wheat varieties were 

found to have higher Septoria 

susceptibility at GS 39 (flag leaf 

ligule just visible) and spring 

varieties at GS 65 (flowering 

halfway complete). These were 

followed by GS 32/33 (stem 

elongation-first node detectable) 

and GS 39 for facultative and 

spring varieties, respectively. 

Inoculations at GS 22 to GS 31 

did not produce adequate 

infection levels. 

At the second evaluation on 5 

September, the group seeded on the 

first date was already dry. For the 

remaining three sowing dates, the 

highest infection level was shown by 

facultative wheat varieties inoculated 

at GS 32-33 and by spring wheat 

varieties inoculated at GS 39. 

Comparison of the cultivars’ field 

reactions to S. tritici with infection 

under controlled conditions showed 

differences in I. Mirlo, P. Superior, E. 

Halcón, and P. Oasis. These cultivars 

are considered resistant (R), 

moderately resistant (MR), moderately 

resistant (MR), and susceptible (S), 

respectively, under field conditions; 

under controlled conditions they were

MS, R, R, and MS, respectively. The 

interaction between cultivar and 

growth stage at inoculation 

indicated the lack of precision that 

may occur while evaluating 

resistance of a variety. 

In the first evaluation, with 

relatively low levels of infection, 

cultivars such as P. Oasis showed 

significantly lower infection levels 

at GS 65 than at GS 39. E. Pelón 90 

showed similar behavior without 

being significantly different at 

these two growth stages. However, 

in contrast to P. Oasis and E. Pelón 

90, P. Superior presented a 

significantly higher infection level 

at GS 65 than at GS 39 (Table 3; 

Figure 1). Although the infection 

level of P. Superior at the initial 

stages was almost equal to that of 

% of infection 

0 

Sowing date 27/06 31/05 16/05 28/04 

ZGS 22-23 30-31 39 65 

Figure 1. Level of infection, average of three 

% of infection 

12 

9 

6 

3 

50 

40 

30 

20 

10 

Leaves, August 28th. 

Cardenal 

Oasis 

Mirlo 

Pelón 

Superior 

Leaves, September 5th. 

Charrúa 

Halcón 

LE2196 

Federal 

Superior 

Pelón 

Mirlo 

Oasis 

Cardenal 

0 

Sowing date 27/06 31/05 16/05 

S-ZGS 22-23 30-31 39 

F-ZGS 24-25 30 32-33 

Figure 2. Level of infection, average of three 

susceptible varieties P. Oasis and E. 

Cardenal at the second evaluation, P. 

Superior showed the slowest 

increase over time to become the 

most resistant genotype at the adult 

plant stage. This suggests that P. 

Superior (Bobwhite) may have a 

certain degree of adult plant 

resistance. 

In general, spring habit, high 

yielding, early maturing semidwarf 

wheats showed higher levels of 

Septoria infection than the facultative 

wheats (tall and late maturing). The 

highest infection level observed in a 

facultative wheat (E. Federal) is 

equivalent to the level demonstrated 

by a moderately resistant spring 

variety such as E. Pelón 90 (Figure 2). 

As per the definition put forward by 

Arama, Parleviet, and van Silfhout 

(1994), Buck Charrúa seems to 

possess overall resistance. A high 

degree of resistance was observed at 

the juvenile stage in all varieties. 

Only P. Superior demonstrated 

adult-plant resistance. Further 

studies are required to evaluate the 

level of resistance in stages earlier 

than GS 22-25. 

Conclusions 

The S. tritici susceptibility of 

different wheat varieties seems to 

increase with the age of the plants. 

However, the rate of this increase 

(the slope of the curve) is different 

for each cultivar. As a result 

interactions were observed between 

the cultivars’ susceptibility (infection 

level) and growth stage at the time of 

infection (inoculation). This suggests 

that several evaluations may be 

required to determine a cultivar’s 

potential as a parent in a crop 

improvement program. 

Septoria tritici Resistance of Wheat Cultivars at Different Growth Stages 133 

References 

Arama, P.F., Parlevliet, J.E., and van 

Silfhout, C.H.1994. Effect of 

plant height and days to heading 

on the expression of resistance in 

Triticum aestivum to Septoria tritici 

in Kenya. In: Proceedings of the 

4 th . International Workshop on: 

Septoria of cereals. E. Arseniuk, 

T. Goral, and P. Czembor (eds.). 

July 4-7, 1994. IHAR Radzikow, 

Poland. pp. 153-157. 

Danon, T., Sacks, J.M., and Eyal, Z. 

1982. The relationship among 

plant stature, maturity class, and 

susceptibility to septoria leaf 


72:1037-1042. 

Díaz de Ackermann, M., Stewart, S., 

Ibañez,V., Capdeville, F., and 

Stoll, M. 1994. Pathogenic 

variability of Septoria tritici in 

isolates from South America. In: 

Proceedings of the 4 th 


Septoria of cereals. July 4-7, 1994. 

Ihar Radzikow, Poland. 

pp. 335-338. 

Eyal, Z., and Talpaz, H. 1990. The 

combined effect of plant stature 

and maturity on the response of 

wheat and triticale accessions to 

Septoria tritici. Euphytica 

46:133-141. 

Kema, G.H.J., and van Silfhout, 

C.H. 1995. Comparative 

virulence analysis of Septoria 

tritici to seedling and adult plant 

resistance. In: Breeding for 

disease resistance with emphasis 

on durability. Regional 

Workshop for Eastern, Central 

and Southern Africa. D.I. Danial 

(ed.). Njoro, Kenya, October 4-7, 

1994. p. 221. 

Tavella, C.M. 1978. Date of heading 

and plant height of wheat 

cultivars, as related to septoria 

leaf blotch damage. Euphytica 

27:577-580. 

Van Beuningen, L.T., and Kohli, 

M.M. 1990. Deviation from the 

regression of infection on 

heading and height as a measure 

of resistance to septoria tritici 

blotch in wheat. Plant Disease 

74:488-493. 


Konzak, C.F. 1974. A decimal 

code for the growth stages of 

cereals. Weed Res. 14:415-4214.

134 

Septoria tritici Resistance Sources and Breeding 

Progress at CIMMYT, 1970-99 

L. Gilchrist, 1 B. Gomez, 2 R. Gonzalez, 2 S. Fuentes, 3 A. Mujeeb-Kazi, 1 W. Pfeiffer, 1 S. Rajaram, 1 R. Rodriguez, 3 B. 

Skovmand, 1 M. van Ginkel, 1 and C. Velazquez1 (Field presentation) 

1 CIMMYT Wheat Program, El Batan, Mexico 

2 National Livestock and Agricultural Research Institute (INIFAP), Mexico 

3 Retired CIMMYT Staff 

Abstract 

An overview is provided of the sources of Septoria tritici resistance used in the CIMMYT bread wheat program, and of 

progress in breeding for resistance for wheat mega-environment 2 (high rainfall) in 1970-99. Several phases can be 

distinguished: use of Russian winter wheat, lines from the Southern Cone of South America (Brazil, Chile and Argentina) 

and USA as resistance sources; introduction of disease resistance from Brazilian sources into semi-dwarf and early 

backgrounds; introduction of genes from triticale and Triticum diccocon into common wheat; introgression of resistance 

from synthetic hexaploids and derivatives into susceptible bread wheat stocks; pyramiding of Chinese resistance sources with 

the sources mentioned above, and combining them into adapted agronomic types. Some preliminary work on resistant durum 

wheat sources, including some of the best ones from Tunisia, is presented. 

Bread Wheat Program 

The semidwarf wheats 

developed in Mexico in the 1960s 

were widely distributed. The 

modern wheat varieties that 

replaced local wheats were 

successful because of their wide 

adaptation, high yield potential, 

and disease resistance (mainly to 

stem and leaf rust) for favorable, 

irrigated production conditions 

(Rajaram et al., 1994). 

The emphasis of CIMMYT’s 

bread wheat breeding program on 

disease resistance was expanded in 

the 1970s to include resistance to 

Puccinia striiformis and Septoria 

tritici for the high rainfall wheat 

growing areas of the world (megaenvironment 

2). These are 

temperate environments with an 

average precipitation of >500 mm. 

The search for S. tritici resistance, 

the accumulation of resistance 

genes, and the incorporation of 

resistance into high yielding 

advanced lines have been very 

successful in the CIMMYT bread 

wheat program. 

Three main groups of sources 

were used to introduce resistance: 

a) Russian winter wheat, b) lines 

from the wheat growing areas of 

Brazil, Chile, and Argentina 

(Southern Cone of South America), 

and c) to a lesser extent, lines from 

the USA (Mann et al., 1985) 

(Table 1). The resistance of these 

lines was identified and/or 

confirmed in different countries 

through the International Septoria 

Nursery (ISEPTON), beginning 

in 1971. 

The breeding program focused 

on combining the semidwarf plant 

type with high yield potential and 

resistance to leaf and stripe rust 

plus septoria leaf blotch. 

Germplasm was screened and 

selected for septoria leaf blotch at 

two locations in Mexico: Patzcuaro 

and Toluca. Patzcuaro is located at 

2,200 m altitude in the western 

Mexican highlands (Michoacan 

state). It proved suitable for testing 

advanced lines, since epidemics of 

S. tritici occur naturally every year. 

In some years we can also select for 

resistance to Pyrenophora triticirepentis 

and Stagonospora nodorum. 

The Atizapan experiment station in 

Toluca (Mexico state) at 2,600 m 

altitude has an intense rainy season 

during the summer months (800- 

900 mm). Artificial epidemics are 

created by inoculating with 

infected straw or a spore 

suspension involving a mixture of 

isolates. 

Numerous lines with acceptable 

resistance levels were derived from 

crosses using the above mentioned 

sources and subsequent testing in 

Toluca and Patzcuaro (Table 2).

Another set of resistant lines 

was created by the wheat 

germplasm enhancement 

section. The S. tritici resistance of 

lines from Brazil (IAS 20, Pelotas 

Arthur, Colotana, IAS 58, and 

Maringa), which are tall and 

late-maturing with weak straw, 

was incorporated into earlymaturing, 

high yielding 

semidwarf lines. Thus earlymaturing, 

short, high yielding 

lines were developed that had a 

level of resistance similar to that 

of the original resistant parent 

(Table 3). 

Bread wheat lines were also 

crossed with triticale, and the 

resulting lines showed high 

levels of S. tritici resistance 

(Table 4). Subsequently, some of 

the lines listed in Table 3 were 

combined with triticale-derived 

lines (Table 5) in an attempt to 

pyramid several resistance 

genes. 

CIMMYT’s wheat wide 

crosses program has generated a 

wide range of resistant 

germplasm from D genome 

synthetics and their synthetic 

derivatives (Mujeeb-Kazi et al., 

1996; 1998; 1999). These 

materials express high levels of 

resistance to several leaf 

pathogens, including Bipolaris 

sorokiniana, Pyrenophora triticirepentis, 

and S. tritici. Their 

resistance may be to one or a 

combination of these pathogens. 

Table 6 shows a group of 

representative synthetic wheats 

with high levels of resistance to 

S. tritici. 

Septoria tritici Resistance Sources and Breeding Progress at CIMMYT, 1970-99 135 

Table 1. Main sources of Septoria tritici resistance used by the CIMMYT wheat breeding 

program in the 1970s. 

Ex-USSR Southern Cone of SA USA spring Other 

winter wheat spring wheat wheat sources 

Aurora IAS 55 Chris Enkoy 

Kavkaz IAS 58 Era Salomoni Seafoam 

Bezostaja 1 PF 70254 Frontana-Kenya Kvz/K4500 L.6A.6 

Maringa x Newthatch 

Carazinho 

IAS 63 

Lagoa Vermelha 

Tizano Pinto Precoz 

IAS 62 

CTN 7 

CTN 8 

Gaboto 

IAS 20 

Table 2. CIMMYT-derived lines with acceptable Septoria tritici resistance from the ex-USSR, 

USA, France, Brazil, Chile, and Romania. 

Advanced line Pedigree cross Number S. tritici score a Origin 

Veery Kvz/Buho//Kal/Bb CM 33027 76-86 Ex-USSR 

Bobwhite Au//Kal/Bb/3/Wop CM 33203 32-76 Ex-USSR 

Musala Lee/Kvz/3/Cc//Ron/Cha CM16780 Ex-USSR 

Sunbird Gll/Cuc//Kvz/Sx CM34630 42-77 Ex-USSR 

Milan VS73.600/Mirlo/3/ CM75113 21-74 France/Ex 

Bow//Ye/Trf USSR 

Attila ND/VG9144//Kal/Bb/ CM85836 73-76 USA/Ex- 

3/Yaco/4/Veery USSR 

Bagula Ore F1 158/Fdl// CM59123 53-75 USA/Romania 

Mfn/2*Tiba63/3/Coc 

/4/Bb/GLl//Carp/3/Pvn 

Prinia Prl/Vee#6/Myna/Vul CM90722 74-76 Ex-USSR 

Chilero 4777*2//Fkn/Gb54/3/ CM66684 74-76 Ex-USSR 

Vee#5/4/Buc/Pvn 

Corydon Car 853/Coc/Vee/3/ CM81074 41-75 Chile/ Brazil/ 

E7408/Pam//Hork/PF73226 Ex - USSR 

Tinamu IAS58/4/Kal/Bb// CM81812 32-75 Brazil/Ex- 

Cjm71/Ald/5/Au// USSR 

Kal/Bb/3/Wop 

a Double digit scale (Saari and Prescott, 1975; Eyal et al., 1987) indicating the range of damage during two 

screening cycles in Toluca. 

Table 3. Short, early-maturing, Septoria tritici resistant lines derived from tall, late-maturing, 

resistant Brazilian varieties, with a resistance similar to that of the original resistant parents. 

Lines Cross number S. tritici score a 

IAS 20/H567.71//4*IAS 20 CMH 79.243 35-52 

IAS 20/H567.71//IAS 20/3/IAS 58 CMH 78.390 31-42 

IAS 20/H567.71//IAS20/3/3*MRNG CMH 78.443 32-63 

CLT/H471.71A//4*CLT CMH 83.2277 32-53 

H.567.71/3*P.Ar CMH 77.308 32-74 

IAS 20 – 11-62 

IAS 58 – 31-54 

Maringa – 31-54 

Colotona – 11-51 

Pelotas Arthur – 21-71 


screening cycles in Toluca.

Session 6C — L. Gilchrist et al. 

136 

Table 4. Septoria tritici resistant lines derived from bread wheat x triticale crosses. 


INIA 66/RYE*2//ARM/3/H277.69 CMH 72.A576 21-42** 

M2A/CML//2*NYUBAY CMH 80.A1267 22-52 

M2A/CML//Nyubay/3/ CMH72A576/MRG CMH 82.961 32-43 



Table 5. Septoria tritici resistant lines combining resistance from Brazilian sources and bread 

wheat x triticale derived lines. 


H.567.71/3*P. Ar/MRNG//IAS20/H567.71/ 

IAS20/3/3*MRNG/79.243/4/M2A/CML// 

NYUBAY/3/INIA66/Rye*2//ARM/3/H277.69 

CMH 85.3215 31-42 

EAGLE/H567.71//4*EAGLE/3/2*IAS20 

/H567.71//4*IAS20 

CMH 79.243 11-43 



Table 6. Synthetic hexaploid wheats (Triticum turgidum x Aegilops tauschii; 2n=6x=42) with high 

levels of resistance to Septoria tritici. 

Synthetic hexaploids Cross number S. tritici score a 

Aco 89/Ae. tauschii (309) b CIGM90.595 11-11 

Croc1/Ae. tauschii (879) CIGM89.479 11-21 

Doy1/Ae. tauschii (372) CIGM93.229 11-21 

Sty-US/Celta//Pals/3/SRN-5/4/Ae. tauschii (502) CIGM93.261 11-11 

Altar 84/Ae. tauschii (502) CIGM93.395 11-11 



b Accession number in the wide cross working collection in CIMMYT’s wheat genebank. 

Table 7. Synthetic hexaploids crossed with susceptible and moderately susceptible bread 

wheats to develop advanced derivatives resistant to Septoria tritici. 

Advanced derivative Cross number S. tritici score a 

Altar 84// Aegilops tauschii (191) b CIGM92.337 21-52 

//Yaco/3/2*Bau 

Croc 1/ Aegilops tauschii (205)//Kauz CIGM90.248 11-31 

Croc 1/ Aegilops tauschii (205)/5/Br12*3/4/ CIGM90.252 11-32 

Ias 55*4….. 

Altar 84/Aegilops tauschii (219)//Opata CIGM90.429 11-32 

Altar 84/Aegilops tauschii (219)//2*Seri CMSS92YO1855M 21-32 

Altar 84/Aegilops tauschii (224)//2*Yaco CIGM91.191 11-32 

Bcn/3/Fgo/USA2111//Aegilops tauschii (658) CASS94Y00146S 11-22 

Opata/6/68111/Rgb-V//Ward/3/Fgo/4/ CASS94Y00247S 11-22 

Rabi/5/Aegilops tauschii (878) 

Filin/4/Snip/Yan79//Dack/Teal/3/ CASS94Y00072S 32-32 

Aegilops tauschii (633) 

Altar 84/Aegilops tauschii (191)// Opata/3/ CIGM93.566 11-22 

Altar 84/Aegilops tauschii (224)//Yaco(1)… 

Mayoor//TkSN1081/Aegilops tauschii (222) CASS94Y00009S 11-22 



b Accession number in the wide cross working collection in CIMMYT’s wheat genebank. 

The high levels of resistance 

present in the synthetic hexaploids 

were incorporated into susceptible 

bread wheat advanced lines and in 

some cases were used to reinforce 

the intermediate susceptibility 

present in some lines (Table 7). To 

pyramid the resistance genes, 

resistant alien germplasm 

possessing tertiary gene pool 

diversity was crossed with resistant 

Chinese germplasm (Table 8). 

Another effort to diversify the 

sources of resistance focused on the 

Triticum dicoccon collection in the 

wheat genebank (Gilchrist and 

Skovmand, 1995). Early tall 

accessions with resistance to P. 

striiformis and S. tritici, and weak 

straw were identified from 

genebank collections. One of these 

accessions was selected and 

crossed to a very susceptible 

selection of the line Kauz. The 

resulting lines combine high levels 

of resistance to P. striiformis and S. 

tritici with good agronomic type 

(Table 9). 

In a second effort of the bread 

wheat breeding program (1986-87) 

to increase variability of the 

resistance base, a group of 

advanced bread wheat lines 

consisting of resistance sources in 

an adapted background (Table 10) 

was crossed with a group of 

Chinese lines having acceptable 

levels of resistance (Sumai #3, 

Suzhoe #8, Suzhoe #6 Ningmai #4, 

Yangmai #4, Ning 8401, YMI #6, 

Shangai #5, Shangai #, Nanjing 

7840, Wuhan 2, and Wuhan 3). 

Once the resistance of the 

Chinese materials had been 

introduced, a new effort was

initiated to combine high yield 

potential and pyramid resistance 

genes (Table 11). 

Shuttle breeding between 

different sites is very important 

for selection and helps to increase 

effective resistance across 

different locations where S. tritici 

is a problem. A large number of 

advanced lines showing very high 

levels of resistance have been 

selected through shuttle breeding. 

New sources have also been 

selected with this methodology. A 

representative example of new 

sources coming from the Southern 

Cone of South America that were 

identified in the region through 

the LACOS (Advanced Lines for 

the Southern Cone) nursery is 

given in Table 12. 

Durum Wheat Program 

In the countries of West Asia 

and North Africa (WANA), severe 

epidemics of septoria leaf blotch 

have occurred, especially in 

Morocco, Tunisia, and Turkey 

(Saari, 1974). Isolates of the 

pathogen have been identified in 

different regions, along with their 

specificity for durum and bread 

wheat. Breeding efforts have 

increased resistance levels, but 

selection for resistance is 

complicated by different disease 

reactions at different locations 

and in different years. This may 

be due to different environmental 

conditions or to the variability of 

S. tritici populations (Arama et al., 

1988); van Silfhout et al. (1989) 

have reported specificity in some 

durum and bread wheat isolates. 

Complementary information was 


Table 8. Advanced wheat lines resistant to Septoria tritici and derived from crosses of perennial 

Triticeae species and Chinese germplasm. 

Lines Crosses S. tritici score a 

CS/Thinopyrum curvifolium//Glenn.81/3/Ald/Pvn CIGM84295 31-43 

Cno79/4/CS/Thinopyrum curvifolium// CIGM88829 32-62 

Glenn.81/3/Ald/Pvn 

Cno 79/4/CS/Thinopyrum curvifolium//Gen/3/ CIGM8876 32-42 

Ald/Pvn/4/CS/Leymus racemosus//2*CS/3/Cno 79 

Inia66/Thinopyrum distichum//Inia66/3//4/Gen/ CIGM88734 31-62 

CS/Thinopyrum curvifolium//Glenn.81/3/Ald/Pvn 

CS/Thinopyrum curvifolium//Glenn 81/3/Ald/Pvn/ CIGM87.116 51-72 

4/Ningmai#4/Oleson//Ald/Yangmai#4 

CS/Thinopyrum curvifolium/Glenn 81/3/ CIGM87.123 31-42 

Ald/Pvn/4/Suzhoe#8 

CS/Thinopyrum curvifolium//Glenn 81/3/ CIGM87.1109 41-53 

Ald/Pvn/4/Ningmai 8401 

Chir3/5/CS/Thinopyrum curvifolium//Glenn 81 CIGM93.612 21-22 

/3/Ald/Pvn/4/Cs/Leymus racemosus//2*CS/3/Cno79 



Table 9. Triticum dicoccon/Kauz advanced lines with resistance to Septoria tritici. 

Advanced lines and pedigree Cross number S. tritici score a 

T. dicoccon PI 1254156/2*Kauz GRSS93SH18-0M-12SH-2M-1Y 11-51 



T. dicoccon PI 1254156/2*Kauz GRSS93SH27-OM-10SH-3M-1Y 11-72 


Kauz (susceptible parent) 89-99 

Bobwhite (moderately resistance check) 41-46 

T. dicoccon PI 1254156 (resistant parent) 11-71 



Table 10. Advanced lines consisting of sources of Septoria tritici resistance in an adapted 

background, crossed with a group of resistant Chinese lines. 

Advanced line Cross S. tritici score a 

Shangai#5/Bow CM91100 32-72 

Ald/Pvn//YM#6 CM91065 21-72 

Suzhoe#6//Ald/Pvn CM91128 32-71 

YM#6/Thb*2 CMH87.2698 42-72 

Ald/Pvn//Ning#7840 CMH91325 11-47 

Sha#5/Weaver CM95103 11-32 

Sha#8/Gen CM95124 11-32 

Milan/Sha#7 CM97550 52-63 

Sabuf CM95073 53-32 

Catbird CM91045 42-76 



Session 6C — L. Gilchrist et al. 

138 

Table 11. Bread Wheat Program advanced lines with high yield potential containing different 

combinations of Septoria tritici resistance sources in their pedigrees. 

Advanced lines Cross S. tritici score a 

Trap#1/Bow CM 84548 21-35 

PF70354/Bow CM 67910 21-54 

Gov/Az//Mus/3/Dodo/4/Bow CM 79515 31-64 

Ald/Pvn//YMI#6/3/Ald/Pvn CM 96723 11-41 

Ias20*3/H567.71//Sara CM 81021 11-31 

Ning8675/Catbird CMSS92Y00639S 32-52 

Thb/CEP7780//Suz#9/Weaver/3/Ng8675 CMSS92Y02302T 52-63 

Cbrd/5/Cs/Thinopyrum curvifolium// 

Glen/3/Gen/4/L2266/1406.101//Buc/ 

3/Vpm/Mos83.11.4.8//Nac 

CMBW91MO3723 11-21 

Sha3/Seri//Kauz/3/Sha4/Chil CMBW91M03723 11-21 

Bau/Milan CM103873 11-21 

Lfn/II58.57//PRL/3/Hahn CM77224 31-42 

Sha #3/Seri//Psn/Bow CMBW90M2470 31-42 

Suz #6/Weaver//Tui CMBW90M2474 11-21 



Table 12. Bread wheat germplasm resistant to Septoria tritici that was selected through shuttle 

breeding and collaborative nurseries (CIMMYT/national agricultural research programs). 

S. tritici 

Lines and crosses score a Origin 

T00011/T00007 

A8972-1T-2N-1B-2T-2T-0T 

53 Argentina 

L.A.CIAT(Santa Cruz) 63 Bolivia 

Talhuen INIA 31 Chile 

Br14/CEP847 

B31615-0A-0Z-1A-15A-0A 

21 Brazil 

Iapi/Fink 

CP3409-1E-0Y-0E-18Y-0E 

31 Paraguay 

E Fed/F.5.83.7792 (Bajas) 42 Uruguay 



found by Eyal et al. (1985), whose 

studies revealed that isolates from 

Syria and Tunisia were more 

virulent on tetraploid than on 

hexaploid varieties. 

Based on this information, elite 

durum wheat lines were selected in 

Toluca and Patzcuaro, as was 

described earlier for bread wheat. A 

representative group of these 

selections is listed in Table 13. This 

germplasm is under observation in 

the WANA region, but the dry 

conditions that have prevailed in 

recent years have not permitted 

accurate information to be obtained 

on the resistance of germplasm preselected 

in Mexico. However, 

information from Tunisia (Table 14) 

has contributed greatly to 

enhancing the effective resistance 

in durum wheat germplasm, and 

the disease data from that location 

have been used to design crosses. 

Conclusion 

In conclusion, there are 

numerous sources of resistance to 

S. tritici. For the most part, the 

genetic constitution of these 

sources remains unclear, but the 

information contained in this paper 

suggests that they are genetically 

different. Resistance sources in 

CIMMYT’s genebank collections 

are available on request. 

References 

Arama, P.F., van Silfhout, C.H., and 

Kema, G.H.J. 1988. Report on the 

Cooperative research project 

between IPO, Tel Aviv University 

and CIMMYT. 31 pp. 

Eyal, Z., Scharen, A.L., Hoffman, 

M.D., and J.M. Prescott. 1985. 

Global insights into virulence 

frequencies of Mycosphaerella 


75(12):1456-1462. 

Eyal, Z., A.L. Sharen, J.M. Prescott, 






Gilchrist, L., and Skovmand, B. 1995. 

Evaluation of emmer wheat 

(Triticum dicoccon) for resistance to 

Septoria tritici . In: Gilchrist, L., van 

Ginkel, M., McNab, A., and Kema, 

G.H.J., eds. Proceedings of a 

Septoria tritici workshop. Mexico, 

D.F.: CIMMYT. Pp 130-134. 

Mann, C.E., Rajaram, S., and R.L. 

Villarreal. 1985. Progress in 

breeding for Septoria tritici 

resistance in semidwarf spring 

wheat at CIMMYT. In: Sharen, A.L. 

Septoria of Cereals: Proceedings of 

the workshop, held August 2-4, 

1983, at Montana State University, 

Bozeman, Montana. Pp. 22-26.

Mujeeb-Kazi, A., V. Rosas, and S. 

Roldan. 1996. Conservation of the 

genetic variation of Triticum 

tauschii (Coss) Schmalh. (Aegilops 

squarrosa auct. Non L.) in synthetic 

hexaploid wheats (T. turgidum L.s. 

lat X T. tauschii; 2n=6x=42, 

AABBDD) and its utilization for 

wheat improvement. Genetic 

Resources and Crop Evolution 

43:129-134. 

Mujeeb-Kazi, A., Gilchrist, L., 

Villareal, R.L., and Delgado, R. 

1998. D-genome synthetic 

hexaploids: Production and 

utilization in wheat improvement 

In: Triticeae III, Jaradat, A.A.(ed.), 

ICARDA, Aleppo. Pp. 369-374. 

Mujeeb-Kazi, A., Gilchrist, L., 

Villareal, R.L., and Delgado, R. 

1999. Registration of ten wheat 

germplasm lines resistant to 

Septoria tritici leaf blotch. Crop 

Science (in press). 

Rajaram, S., van Ginkel, M., and 

Fischer, R.A. 1994. CIMMYT’s 

wheat breeding megaenvironments 

(ME). In: 


Wheat Genetics Symposium, July 

19-24, Beijing, China. Pp 1101-1106. 

Saari, E.E. 1974. Results of studies on 

Septoria in the near East and 

Africa. Proc. of Fourth FAO 

Rockefeller Foundation Wheat 

Seminar. Tehran, Iran, May 21-June 

2, 1973. Pp. 275-283. 

Saari, E.E., and Prescott, J.M. 1975. A 

scale for appraising the foliar 

intensity of wheat diseases. Plant. 

Dis. Rep. 59:377-380. 

van Silfhout, C.H., Arama, P.F., and 

Kema, G.H.J. 1989. International 

survey of factors of virulence of 

Septoria tritici. In: Fried, M.P., ed., 

Proceedings, Septoria of Cereals. 

Zurich, Switzerland, July 4-7, 1989. 


Table 13. Elite durum wheat lines with resistance to Septoria tritici selected at Toluca and Patzcuaro. 

Lines Cross S. tritici score a 

Aaz77 3/Olus CD 94270 21-22 

Ajaia 12/F3Local 

(Sel.Ethio.135.85)//Plata 13 

CD 98331 21-32 

Eco/CMH76A.722//Yav/3/ 

Altar 84/4/Ajaia 2/5/Kjove 1 

CD 91B2636 32-42 

Gs/Cra//Sba81/3/Ho/4/Mex 1/ 

5/ Memo/6/2*Altar 84 

CDSS 92B1193 32-33 

Himan9/ Bejah 6 CD91B2096 21-21 

Kucuk CD 91B2620 T-11 

Lhnke//Gs/Str/3/Altar 84/4/Focha 1 CDSS92B1076 21-22 

Liro 2 CD 93352 31-31 

Lotus 1/Espe CD97015 11-21 

Lymno 8 CD92314 21-42 

Nus/Silver//CMH82A.1062/ 

Rissa/3/Chen/Altar84/4/Don 

CD91B2664 21-32 

Patka 3 CD 78995 11-21 

Plata1 Smn//Plata 9 CD97899 T- 11 

Plata10/6/Mque/4/Usda573//Qfn/ 

Aa 7/3/Alba-D/5/Avohui/7/ Plata 1 

CD98581 32-43 

Plata 6/ Green17 CD96789 11-21 

Plata7/Fillo 9//Sbak CD99545 31-32 

Plata 8/4/Garza/Afn//Cra/ 

3/Gta/5/Rascon 

CD91B2061 32-42 

Rascon 21/Long CDWS91M377 32-42 

Rascon 37/Green 2 CD91B1975 31-32 

Rascon 37/Tarro 2//Rascon 37 CDSS92B1022 31-32 

Rascon 39/Tilo 1 CDSS92B61 21-22 

Sn Turrk Mi 83-84 503/ 

Lotus 4//Lotus 5 

CD97775 T - 11 

Sooty 9/Rascon 37 CD91B1938 31-32 

Sora/2*Plata 12 CD92011 T - 11 

Topdy 18/Focha 1//Altar 84 CDSS92B1034 22-32 



Table 14. Durum wheat germplasm with resistance to Septoria tritici from Tunisia. 

Lines Cross S. tritici score a 

Karim (Check S ) CM9799 98-97 

Khiar (check S) CD57.005 97-97 

BD 2337 – 53-42 

BD 2338 – 64 

BD 2339 – 64 

Src2/Src1 ICD88.66 75-74 

Gdfl/ T. dicoccoides- 

SY20013/Bcr 

– 64-53 

Bcr/Guerou 1 ICD87.0572 75-76 

Zeina 2 ICD88.1233 44-32 

Zeina 4 ICD88.1233 64-32 

Aus 1/5/Cndo/4/Bry*2/ 

Tace//II27655/3/Tme/Zb/2*W 

ICD88.1120 53-76 

Srn 3/Ajaia 15//Don 87 CD96855 73-42 

Porron 1 CD85328 54 

Poho/Ajaia CD99818 64 

Cali/ship 2// Fillo 7 CD98278 42 

Plata 6/Green 17 CD96789 52 

CMH82A.1062/3/Ggovz394//Sba81/ 

Plc/4/Aaz 1/Crex/5/Hui//Cit71/CII 

CD97395 43 



140 

Selecting Wheat for Resistance to 

Septoria/Stagonospora in Patzcuaro, Michoacan, Mexico 

R.M. Gonzalez I., 1 S. Rajaram, 2 and M. van Ginkel2 1 Campo Morelia, National Livestock and Agricultural Research Institute, Mexico 

2 CIMMYT Bread Wheat Program 

Abstract 

The research reported in this paper was conducted in the humid, temperate area of Patzcuaro in the state of Michoacan, in 

Mexico, where there is a high natural incidence of Septoria/Stagonospora spp. Nine wheat genotypes that had previously been 

selected for resistance to Septoria/Stagonospora spp. were included in the study. They were compared to two check varieties, one 

tolerant and one susceptible. The materials were tested with and without chemical protection. Three years’ data were analyzed and 

relative yield losses of 10-32% were found. Two different responses were observed among the outstanding genotypes. On the one 

hand, several lines expressed little reduction in yield when challenged by the septoria pathogens. Depending on their yield potential, 

final yield could be moderate to quite good. These could be classified as resistant or tolerant to Septoria/Stagonospora spp. Some of 

these same materials did show a considerable level of severity; their response would thus be better classified as tolerance rather than 

resistance. On the other hand, certain materials with high yield potential did lose yield following the attack by the septoria foliar 

blights, but retained sufficient expression of yield potential to compete well with the local check variety. These should not be classified 

as resistant nor tolerant, but may well be desirable from a production standpoint. The line that best combined these traits is IAS20/ 

H567.71/5*IAS 20. It is being considered for release under the name Patzcuaro. Severity of foliar disease on the flag leaf proved to be 

well correlated with yield loss. 

Over the past 15 years, Mexico’s 

National Livestock and 

Agricultural Research Institute 

(INIFAP) and CIMMYT have 

worked together on breeding bread 

wheats for resistance to Septoria 

tritici and Stagonospora nodorum in 

the Patzcuaro, Michoacan, region of 

Mexico. Natural conditions in this 

area favor the yearly development 

of these two Septoria species 

(Gomez and Gonzalez, 1987). The 

area enjoys a temperate climate, 

with mean temperatures of 8-21ºC, 

> 800 mm annual rainfall, and > 

85% relative humidity. The isolates 

of Septoria/Stagonospora spp. that 

thrive under these conditions are 

very aggressive, which makes this 

a stress environment for wheat. 

According to Eyal et al. (1985), the 

Septoria isolates present in the 

Patzcuaro area are among the most 

virulent in the world. 


In this study, 11 advanced 

wheat lines from CIMMYT 

nurseries (Table 1) targeted for high 

rainfall production environments 

(e.g., HRWSN and ASWSN) were 

evaluated with and without 

chemical protection during 1994-96. 

The variety Curinda M-87, 

which has functioned as reference 

in our work for the past 10 years, 

was used as the resistant/tolerant 

check variety in the trials (Table 1). 

The variety Batan was the 

susceptible check. Although both S. 

tritici and S. nodorum were present, 

the former was found in a higher 

proportion in most years. 

Fungicides Terbuconazole and 

Tecto were used for chemical 

control. Terbuconazole was applied 

every 10 days starting from 

tillering to grain milk stage at a 

dosage of 0.5 l/ha. Tecto was 

applied in the same dosage every 

eight days, starting at the end of 

the booting stage. 

Days to flowering, percentage 

flag leaf area affected by Septoria/ 

Stagonospora spp. (% flag leaf 

severity, FLS) at grain milk stage, 

plant height, grain yield, and test 

weight were measured. Yield losses 

and correlations were calculated for 

individual years. 


Several lines expressed higher 

levels of resistance than the 

resistant check variety Curinda 

(29% FLS) (Table 1). Severities as 

low as 1-3% were noted in 

individual years. Across the three

Selecting Wheat for Resistance to Septoria/Stagonospora in Patzcuaro, Michoacan, Mexico 141 

Table 1. Response of 11 wheat lines to natural infection by Septoria/Stagonospora, in regard to flag leaf severity 

(FLS in %), yield, percentage loss, in field plots either protected or unprotected with fungicide, in Pátzcuaro, 

Michoacan. México, during 1994, 1995, and 1996. 

Yield (kg/ha) % 

Entry Cross/Selection history CC * % ** UP % Yield loss % Flag leaf 

1 CURINDA 

Tolerant check 

2875 e *** 100 2042 d 100 29 28 

2 BATAN 

Susceptible check 

3521 b 122 2271 c 111 36 23 

3 IAS20/H567.71/5* IAS20 

CM78A-544-7B-1Y-1B-1Y-2B-1Y-0B 

3826 b 133 3694 a 181 4 1 

4 CHIL//ALD/PVN 

CM92801-65Y-0M-0Y-4M-0RES 

2820 e 98 1590 e 78 44 36 

5 THB/CNT 7 

CM 830057-0Z-0A-1A-1A-1A-0Y 

2632 f 92 2243 c 110 15 10 

6 LIRA/TAN//SPB 

CM96824-U-0Y-0H-0SY-4M-0RES 

2792 f 97 1847 d 90 34 18 

7 ALD/PVN//YMI 6 

CM 91065-2M-0M-0Y-0M-2Y-0B-5PZ 

3681 b 128 2681 b 131 27 3 

8 BAU/MILAN 

CM103873-2M-030Y-020Y-010M-4Y-0M 

3312 c 115 1986 d 97 40 15 

9 ISEPTON89-82E/BR6//PF83144 

F32938-2M-0AL-0AL-0AL-4Y-0M 

3049 d 106 3014 b 148 1 1 

10 BOW/MII//RES/NAC/3/PFAU 

CM1033644-2FC-0M-1FC-0C 

4432 a 154 2688 d 132 39 8 

11 CAR853/COC//VEE/3/E7408/PAM//HORK/PF73226 

CM80174-32Y-04M-0Y-3M-1M-0M 

3854 b 134 2292 d 112 41 24 

LSD 498 545 

Mean 3344 2396 

C.V. 10 16 



1 CURINDA 


4153 c 100 3125 a 100 25 18 

2 BATAN 


3492 e 84 2285 c 73 35 53 

3 IAS20/H567.71/5* IAS20 

CM78A-544-7B-1Y-1B-1Y-2B-1Y-0B 

4521 b 108 3375 a 108 35 26 


CM92801-65Y-0M-0Y-4M-0RES 

4007 d 96 2722 b 87 32 45 

5 THB/CNT 7 

CM 830057-0Z-0A-1A-1A-1A-0Y 

4035 d 97 3153 a 101 22 21 


CM96824-U-0Y-0H-0SY-4M-0RES 

3854 d 92 2986 a 96 22 30 


CM 91065-2M-0M-0Y-0M-2Y-0B-5PZ 

4722 b 114 2875 a 92 39 16 

8 BAU/MILAN 

CM103873-2M-030Y-020Y-010M-4Y-0M 

3952 d 95 3333 a 102 20 13 


F32938-2M-0AL-0AL-0AL-4Y-0M 

4007 d 97 3368 a 108 17 5 


CM1033644-2FC-0M-1FC-0C 

5292 a 127 3236 a 104 39 13 


CM80174-32Y-04M-0Y-3M-1M-0M 

4549 b 110 3222 a 103 29 21 

LSD 484 592 

Mean 4235 3045 

C.V. 8 13 

* (CC) Chemical control and (UP) Unprotected. 

** Percentage relative to the tolerant check, Curinda M87. 

*** Values followed by the same letter are not significantly different at the 0.05 probability level. 

1994 

1995

Session 6C — R.M. Gonzalez I., S. Rajaram, and M. van Ginkel 

142 

Table 1. Continued... 



1 CURINDA 


2896 c 100 2826 c 100 3 40 

2 BATAN 

Suscepible check 

2038 e 70 1637 f 57 19 61 

3 IAS20/H567.71/5* IAS20 

CM78A-544-7B-1Y-1B-1Y-2B-1Y-0B 

3359 b 116 3173 a 112 6 27 


CM92801-65Y-0M-0Y-4M-0RES 

2644 d 91 2289 e 81 13 75 

5 THB/CNT 7 

CM 830057-0Z-0A-1A-1A-1A-0Y 

3206 b 111 2766 c 98 14 31 


CM96824-U-0Y-0H-0SY-4M-0RES 

2710 d 94 2655 c 94 2 62 


CM 91065-2M-0M-0Y-0M-2Y-0B-5PZ 

3961 a 137 3291 a 116 17 28 

8 BAU/MILAN 

CM103873-2M-030Y-020Y-010M-4Y-0M 

3028 c 105 2326 d 82 23 10 


F32938-2M-0AL-0AL-0AL-4Y-0M 

3146 b 109 2847 b 101 10 22 


CM1033644-2FC-0M-1FC-0C 

3456 b 119 3185 a 113 26 38 


CM80174-32Y-04M-0Y-3M-1M-0M 

3156 b 110 2852 b 101 28 33 

LSD 412 345 

Mean 3094 2713 

C.V. 9 11 




years Curinda, when unprotected, 

yielded on average 2688 kg/ha, 

expressing a 19% loss (Table 2). 

Several lines were also superior to 

the check in yield, and suffered less 

yield loss. 

In this study percent flag leaf 

area affected correlated negatively 

with yield loss (-0.71 to -0.83; 

Table 3). This negative correlation 

appears strong and reliable over 

years. 

Although grain yield of most 

lines tested varied over years 

depending on climatic and 

production conditions (Figure 1), in 

general their performance relative 

to the resistant check Curinda 

showed impressive consistency 

over time. In contrast, the 

susceptible check Batan yielded 

less every year as a percentage of 

the check (Tables 1 and 2; Figure 1), 

and seemed to be losing its 

resistance progressively. 

The plots protected with 

fungicide provide a partial 

expression of each line’s yield 

potential in the absence of disease 

stress. However, other abiotic 

stresses, such as soil acidity and 

nutrient imbalances related to 

leaching following excessive rain, 

also reduce yield in this high 

rainfall environment. The 

difference between the protected 

and unprotected plots provides a 

measure of yield loss due to 

disease. Mean yield losses were in 

the 10-32% range. The line 

ISEPTON89-82E/BR6//PF83144 

experienced the lowest loss (10%), 

while the susceptible check Batan 

suffered the highest (32%). 

1996 

Comparing protected and 

unprotected plots provides a measure 

of the contribution of resistance or 

tolerance to yield. If the yield 

difference is small (i.e. the loss is 

small), the genotype tested 

apparently has a certain level of 

resistance/tolerance that enables it to 

express most, if not all, of its yield 

potential. However, useful 

information can also be gained from 

direct comparison of lines in a 

disease-prone setting, in companion 

plots without the use of fungicides, in 

particular when screening germplasm 

to identify potential varieties. This is 

less expensive than also growing 

protected plots, and hence allows 

larger numbers of entries to be tested. 

To be acceptable to farmers, a 

variety must yield the same or better 

than the commercial check variety. 

Candidate varieties can be acceptable

and appear well adapted to the 

point of being releasable to farmers 

for two reasons, or a combination of 

both. On the one hand, a line may 

express true resistance or tolerance. 

In that case challenge by the 

pathogen does not result in great 

reductions in yield (Tables 1 and 2). 

Yield potential is roughly 

maintained due to resistance, with 

only minimum disease severity, or 

due to tolerance when considerable 

disease severity may be noted but 

losses are little. The line 

ISEPTON89-82E/BR6//PF83144 is a 

good example of a resistant 

Selecting Wheat for Resistance to Septoria/Stagonospora in Patzcuaro, Michoacan, Mexico 143 

genotype (9% FLS) with minimum 

yield loss (10%) and a high mean 

yield of 3034 kg/ha, 13% more 

than the tolerant check, Curinda, 

in the presence of disease. Most 

lines suffered yield losses which 

percentage-wise were roughly 

equivalent to about two-thirds of 

their percentage-wise flag leaf 

severity scores. Good examples of 

very sensitive lines are ALD/ 

PVN//YMI 6 and BAU/MILAN, 

whose mean % yield losses (27%- 

28%) were almost twice that of 

their FLS scores (13%-16%). 

Table 2. Mean response of 11 wheat lines to natural infection by Septoria/Stagonospora, in regard to flag leaf 

severity, yield, percentage loss, in field plots either protected or unprotected with fungicide, in Patzcuaro, 

Michoacan, Mexico, over 1994, 1995, and 1996. 

Mean values 

% Overall 

Yield mean yield 

Entry Cross/Selection history CC * % ** UP % loss % Flag leaf kg/ha % 

1 CURINDA 


3376 c *** 100 2688 d 100 19 29 3005 c 100 

2 BATAN 


3016 e 89 2003 h 75 32 46 2470 f 82 

3 IAS20/H567.71/5* IAS20 

CM78A-544-7B-1Y-1B-1Y-2B-1Y-0B 

4094 b 121 3380 a 126 13 18 3709 a 123 


CM92801-65Y-0M-0Y-4M-0RES 

3062 d 91 2216 g 82 30 52 2606 d 87 

5 THB/CNT 7 

CM 830057-0Z-0A-1A-1A-1A-0Y 

3298 c 98 2727 c 101 17 21 2991 c 99 


CM96824-U-0Y-0H-0SY-4M-0RES 

3098 d 91 2519 e 94 20 37 2786 d 93 


CM 91065-2M-0M-0Y-0M-2Y-0B-5PZ 

4160 a 123 2998 b 112 28 16 3534 a 118 

8 BAU/MILAN 

CM103873-2M-030Y-020Y-010M-4Y-0M 

3449 c 102 2473 f 92 27 13 2924 d 97 


F32938-2M-0AL-0AL-0AL-4Y-0M 

3486 c 103 3034 b 113 10 9 3242 b 108 


CM1033644-2FC-0M-1FC-0C 

4441 a 132 3058 b 114 31 20 3696 a 123 


CM80174-32Y-04M-0Y-3M-1M-0M 

3870 b 115 2798 b 104 28 26 3292 b 109 

LSD 346 312 314 

Mean 3577 2717 3114 

C.V. 12 15 18 

Chemical control (CC) 3577 a 

Unprotected (UP) 2717 b 

1994 3344 b ns 

1995 4234 a ns 

1996 3153 c ns 

LSD 181 




On the other hand, a line may 

have a very high intrinsic yield 

potential in the absence of biotic 

stresses, such as attacks by Septoria/ 

Stagonospora spp. Even if 

susceptible to the fungus, such 

lines may express a residual yield 

that competes well with that of the 

check variety (and may even 

outyield it in certain cases). These 

lines are not resistant—on the 

contrary, they may be quite 

susceptible. Their virtue lies in 

their high initial yield potential, 

which allows a considerable loss 

due to disease, and still produces

Session 6C — R.M. Gonzalez I., S. Rajaram, and M. van Ginkel 

144 

an impressive final yield when 

challenged by the fungus. In this 

study BOW/MII//RES/NAC/3/ 

PFAU is an example of a line with 

high yield potential, which despite 

having 20% of its flag leaf area 

damaged by Septoria/Stagonospora 

spp., resulting in a 31% mean yield 

loss, still yielded 14% more than 

the commercial check. 

The most desirable genotype is 

one that combines high yield 

potential with resistance/tolerance 

to the fungus; this results in 

relatively low losses in the presence 

; 

200 

;;; 

% yield of check Curinda 

150 

100 

CC 1994 

CC 1995 

CC 1996 

UP 1994 

UP 1995 

UP 1996 

of disease, and outstanding yields 

in its absence. The line IAS20/ 

H567.71/5*IAS 20 combines these 

traits; only 18% of its foliage was 

affected, which translated into a 

minimal yield loss of 13% and 

resulted in the trial’s top mean 

yield of 3380 kg/ha, 26% over the 

commercial check, Curinda, in the 

presence of disease (Table 2 and 

Figure 1). It produced a very 

respectable yield of 4094 kg/ha, the 

third highest of the group, in the 

absence of disease. This line is now 

being considered for release under 

the name Patzcuaro. 

References 

Table 3. Correlation coefficients of flag leaf severity and yield with various other characters, Patzcuaro, 

Michoacan, Mexico, during 1994, 1995, and 1996. 

Eyal, Z., A.L. Scharen, M.D. Huffman, 

and J.M. Prescott. 1985. Global 

insights into virulence frequencies 

of Mycosphaerella graminicola. 


Gomez, B.L., and R.M. Gonzalez I. 

1987. Mejoramiento genético de 

trigos harineros para resistencia a 

Septoria tritici en el área de 

temporal húmedo en Mexico. In 

Conferencia regional sobre la 

septoriosis del trigo, M.M. Kohli 

and L.T. van Beuningen, eds. 

Mexico, D.F.: CIMMYT. pp 42-57. 

Variables Variables 1994 1995 1996 

Flag leaf severity due to infection Yield -0.81 -0.83 -0.71 

by Septoria/Stagonospora Test weight -0.72 -0.34 -0.44 

Plant height -0.48 -0.55 -0.62 

Yield loss (%) 0.71 0.33 0.71 

Days to flowering -0.42 -0.71 -0.84 

Yield Test weight 0.72 0.85 0.76 

Plant height 0.62 0.44 0.55 

Yield loss (%) -0.75 -0.49 -0.86 

Days to flowering 0.46 0.86 0.79 

; 

; ; ; 

; ; ; ; ; 

; 

; ; ; ; ;; ; ; ; 

; ;; ; ; ; ; ;; ; ; ; 

; ; ; ; ;; ; ; ; 

; ;; ; ;; ; ; ; ; ; ; ; ; ; 

; ;; 

; ;; ;; ; ; 

; ;; ;; ; ; ; 

; ; ; ; ; ; ; 

; 

; ; ; ; ; ; ; 

; ;;; 

; ; ; ; ; ; 

;;; ; ; 

; ; ; 

;; 

;; ; ; ; 

; ;; ; ; ; ; 

; ;; ; ; ; ; 

; ;; ; ; ; ; 

50 Curinda Batan 3 4 5 6 7 8 9 10 11 

Figure 1. Yield as percentage of the tolerant check Curinda, in chemically controlled plots (CC) and 

unprotected plots (UP) of nine wheat lines, during 1994, 1995 and 1996. Patzcuaro, Michoacan, Mexico.

Varieties and Advanced Lines Resistant to Septoria 

Diseases of Wheat in Western Australia 

R. Loughman, 1 R.E. Wilson, 1 I.M. Goss, 1 D.T. Foster, 1 and N.E.A. Murphy2 1 Agriculture Western Australia, Bentley Delivery Centre, Western Australia 

2 WA State Agriculture Biotechnology Centre, Division of Science and Engineering, Murdoch University, 


Abstract 

The development of bread wheats in Western Australia has resulted in the release of several varieties with improved 

response to the commonly occurring leaf spot diseases caused by Phaeosphaeria nodorum, Mycosphaerella graminicola, 

and Pyrenophora tritici-repentis. In a yield trial evaluating resistance to M. graminicola, susceptible varieties suffered 20- 

50% yield loss, while yield loss of resistant crossbreds and varieties was 0-15%. Similar responses were observed in most lines 

for grain weight when assessed in M. graminicola-infected row plots. In P. nodorum-infected row plots, susceptible 

varieties suffered 30-50% grain weight loss, while resistant lines suffered 0-30% loss in grain weight depending on year 

of testing. 

In Western Australia resistance 

to Phaeosphaeria nodorum is sought 

in combination with Mycosphaerella 

graminicola and Pyrenophora triticirepentis 

resistance, as these 

pathogens frequently occur in 

combination (Loughman et al., 

1994). Improved resistance to these 

diseases is sought by continually 

crossing the most resistant, best 

adapted lines with resistance 

donors. A selection of varieties, 

advanced lines, and potential 

resistance sources were assessed for 

resistance in replicated field 

experiments using susceptible 

adapted wheats with comparable 

maturities as benchmarks. 


Lines were evaluated for 

response to infection with M. 

graminicola or P. nodorum in 

separate experiments in 1995-96 

using split plot designs of three 

replicates. At Mt. Barker lines were 

sown as 5-row, 5-m subplots. Main 

plots were established in early 

spring as either fungicide 

protected (three applications of 

125 g tebuconazole/ha) or 

inoculated twice with aqueous 

pycnidiospore suspensions of the 

pathogen. Growth stage (Zadoks 

et al., 1974) and % infection of the 

flag-3 leaves were assessed in late 

spring. Yields were assessed. At 

South Perth lines were sown as 

40-cm, 2-row subplots with 18-cm 

row spacings, each subplot 

separated from its neighbor by a 

single row of barley. Main plots 

were established with fungicide 

or inoculation as above. Separate 

experiments were established for 

M. graminicola and P. nodorum. 

Heading date (as day of the year) 

and disease severity as percent 

infection of the flag or flag and 

second top leaves were recorded 

in spring. Grain weights were 

assessed from a random 

subsample of harvested grain. 

Relative grain weights of infected 

plots were calculated as a 

percentage of fungicide 

protected plots. 

Results and 

Discussion 

Resistance to M. 

graminicola 

Cascades (Tadorna.Inia / 

3*Aroona), Tammin (Bod/Eradu 

sib.xbvt//Atlas66.2Madden), 

and Nyabing (Ar- 

3Ag3(WT329)/ 

(IW753)Jab.Ag4C) developed 

low to moderate infection and 

yielded 5.4, 5.2, and 4.1 t/ha, 

respectively in the presence of 

disease. These yields were not 

significantly different from 

fungicide sprayed plots (yield 

diseased was 89-99% relative to 

the fungicide protected plots). In 

contrast, two susceptible 

varieties of similar maturity, 

Gamenya and Datatine, 

developed high infection scores 

and yielded 1.5 and 3.2 t/ha, 

respectively when diseased. 

These yields were significantly 

different from fungicide sprayed 

plots (yield diseased was 48-72% 

relative to fungicide protected). 

145

Session 6C — R. Loughman, R.E. Wilson, I.M. Goss, D.T. Foster, and N.E.A. Murphy 

146 

Table 1. Maturity (growth stage), percent leaf disease (Dis), yield, hundred-grain weight (HGW), and relative 

yield (RY) and relative grain weight (RGW) of wheat varieties infected with Mycosphaerella graminicola in a 

yield trial at Mt. Barker and small row plots at South Perth, 1995. Comparisons for percent flag leaf disease 

should be made between varieties of similar maturity. 

Mt. Barker South Perth 

Growth Dis Yield(t/ha) RY Dis HGW (g) RGW 

stage Flag-3 Fung Inoc % Flag Fung Inoc % 

Resistant and moderately resistant lines 

77Z893 44 2 5.4 5.3 98 86 3.6 2.5 70 

Nyabing 42 30 4.1 4.1 99 38 4.2 3.4 81 

Cascades 41 23 6.0 5.4 89 86 4.2 2.5 57 

Tammin 41 3 5.8 5.2 90 23 4.2 3.1 76 

483W3 40 0 5.1 5.2 101 21 3.2 3.4 105 

486W189 39 0 4.6 4.3 92 32 3.9 4.2 106 

78Z976 39 5 5.7 5.0 89 40 3.1 2.7 87 

Calingiri 38 1 5.9 5.0 85 43 4.0 3.7 94 

Resistant and moderately resistant control varieties 

Millewa 43 9 4.5 3.9 86 78 3.3 2.2 69 

Aroona 40 13 3.9 4.4 114 99 3.6 2.5 72 

Corrigin 40 2 5.7 5.2 91 70 3.1 2.5 80 

Susceptible control varieties 

Kulin 55 85 4.0 2.2 55 99 2.7 1.6 63 

Tincurrin 42 90 4.5 3.6 80 99 3.6 2.2 68 

Datatine 41 50 4.5 3.2 72 73 3.4 2.5 72 

Gamenya 41 88 3.2 1.5 48 99 3.6 1.9 59 

Stiletto 38 23 4.5 3.2 70 98 4.1 2.8 69 

lsd 5% 2.5 23 1.0 32 0.7 23 

cv % 4 41 13 44 13 19 

Table 2. Maturity (heading day of year, Hd), percent leaf disease (Dis), hundred-grain weight (HGW), and 

relative grain weight (RGW) of wheat varieties infected with Phaeosphaeria nodorum in short row plot 

experiments in South Perth, 1995-96 (- denotes testing discontinued). Comparisons for percent flag leaf 

disease should be made between varieties of similar maturity. 

1995 1996 

Hd Dis HGW (g) RGW Dis HGW(g) RGW 

d.o.y. 

Moderately resistant lines 

Flag Fung Inoc % F,F-1 Fung Inoc % 

Brookton 225 64 3.6 3.7 101 52 3.5 2.8 80 

W48795 228 46 3.6 3.6 101 4 3.8 2.9 76 

81W1137 230 43 3.8 3.6 97 - - - - 

Tammin 231 32 3.9 3.9 103 8 4.3 3.0 71 

W48433 232 33 3.2 3.1 98 30 3.8 3.0 81 

Resistant and moderately resistant controls 

ALMRES-83-18 225 72 4.3 3.6 83 56 3.9 2.8 74 

CNT2 236 21 4.6 4.2 93 45 4.1 3.9 103 

Aus20917 236 40 3.1 2.5 81 27 2.8 2.4 87 

Qualset601-68 

Intermediate lines 

238 18 3.6 3.0 85 20 4.0 2.9 73 

W486110 220 50 4.9 4.2 87 39 4.0 3.3 83 

Westonia 220 83 4.1 3.3 80 76 3.2 2.2 69 

Cascades 226 83 4.1 3.2 80 83 3.7 2.0 54 

Carnamah 226 68 3.4 2.9 86 32 4.1 2.1 51 

Cunderdin 228 50 3.7 3.0 82 41 2.9 2.4 81 

Susceptible control varieties 

Kulin 221 99 3.4 2.2 66 91 3.2 1.5 46 

Aroona 225 87 4.6 2.2 49 92 3.2 1.6 50 

Millewa 225 96 2.6 2.0 77 97 3.3 1.3 44 

Gamenya 228 77 3.4 2.1 64 51 3.2 2.0 63 

Cranbrook 236 71 3.1 2.5 80 48 3.4 2.0 61 

Spear 242 59 4.2 2.6 63 1 4.1 3.0 75 

lsd 5% 23 0.6 24 18 0.8 28 

cv % 26 10 19 23 16 26

Calingiri (Chino/Kulin// 

Reeves) also exhibited resistance 

and while some of this low disease 

expression may have been due to 

later maturity, the performance was 

measurably superior to the similar 

maturing but susceptible variety 

Stiletto. Crossbreds 483W3, 78Z976 

and 77Z893 (Corrigin sib) also 

expressed high levels of resistance, 

as indicated by low disease scores, 

the non-significant yield losses, and 

the resulting high relative yields 

(yield diseased was 89-101% 

relative to fungicide protected) 

(Table 1). 

Resistance to P. nodorum 

Five moderately resistant lines 

achieved high grain weights in 

diseased plots relative to fungicide 

protected plots. Variety Brookton 

(Torres/Cranbrook//76W596/ 

Cranbrook) developed significantly 

less disease and no significant 

grain weight reduction when 

compared with susceptible 

varieties of equivalent maturity 

such as Aroona or Millewa. 

W48795, Tammin, and sister line 

81W1137 had similar maturity to 

susceptible variety Gamenya. 

These lines developed significantly 

less disease than Gamenya and had 

smaller grain weight reductions in 

the presence of disease. Line 

W48433, derived from CNT2, was 

similar to Tammin and developed 

low disease in 1995 and high 

relative grain weights in 1995 and 

1996. This line was comparable 

with the resistant parent CNT2 for 

disease severity and relative grain 

weight in 1995, though relative 

grain weight appeared less robust 

than that of CNT2 in 1996 (Table 2). 

Varieties and Advanced Lines Resistant to Septoria Diseases of Wheat in Western Australia 147 

Westonia (SpicaTimg.Tosc/ 

Cr:J2.Bob), Cunderdin (Cranbrook 

sib/Sunfield sib), Carnamah 

(Bolsena-1ch(RAC529)/77W660), 

and Cascades gave responses that 

were intermediate between the 

resistant and susceptible lines. 

Although hundred grain weight 

reductions in the presence of 

disease were generally significant, 

the grain weight reductions were 

less than for susceptible lines. 

Although excellent levels of M. 

graminicola resistance from diverse 

sources have been observed in lines 

such as 483W3 and 78Z976, 

moderate resistance derived from 

WW15 via Aroona and Condor 

(Wilson, 1994) has had the greatest 

impact in the development of 

commercial varieties. While this 

moderate resistance can be more 

difficult to identify in intensive 

disease nurseries, its effect has been 

observed often in practice and 

previously reported (Loughman 

and Thomas, 1992). 

Significant progress has been 

made in developing moderate 

resistance to P. nodorum. 

Commercial varieties currently 

exhibit improved responses 

compared with their susceptible 

predecessors, and some varieties 

and advanced lines perform at 

similar levels to resistant control 

varieties. In some cases moderate 

resistance to different leaf spot 

diseases has been combined. 

Cascades combines moderate 

resistance to both M. graminicola 

and P. tritici-repentis (Loughman et 

al., 1998). Brookton, Cunderdin, 

and Westonia have moderate 

resistance to P. tritici-repentis 

(Loughman et al., 1998), in 

combination with partial resistance 

to P. nodorum. Because P. nodorum, 

M. graminicola, and P. tritici-repentis 

frequently occur as disease 

complexes in Western Australia, 

combinations of resistance are 

important for effective disease 

management. 

References 

Loughman, R., and Thomas, G.J. 1992. 

Fungicides and cultivar control of 

Septoria diseases of wheat. Crop 

Protection 11: 349-54. 

Loughman, R., Wilson, R.E., and 

Thomas, G.J. 1994. Influence of 

disease complexes involving 

Leptosphaeria (Septoria) nodorum on 

detection of resistance to three leaf 

spot diseases in wheat. Euphytica 

72: 31-42. 

Loughman, R., Wilson, R.E., Roake, 

J.E., Platz, G.J., Rees, R.G., and 

Ellison, F.W. 1998. Crop 

management and breeding for 

control of Pyrenophora triticirepentis 

causing yellow spot of 

wheat in Australia. In Duveiller, E., 

H.J. Dubin, J. Reeves, and A. 

McNab (eds.). Helminthosporium 

Blights of Wheat: Spot Blotch and 

Tan Spot. Mexico, D.F.: CIMMYT. 

Wilson, R.E. 1994. Progress toward 

breeding for resisance to the two 

septoria disease of wheat in 

Australia. Pp. 149-152 In: E. 

Arseniuk (ed.). Septoria of Cereals, 

Proc. Fourth International 

Workshop on Septoria Diseases of 

Cereals. IHAR, Radzikow, Poland. 


Konzak, C.F. 1974. A decimal code 

for the growth stages of cereals. 

Weed Research 14: 415-21.

148 

Field Resistance of Wheat to Septoria Tritici Leaf Blotch, 

and Interactions with Mycosphaerella graminicola 

Isolates 

J.K.M. Brown, 1 G.H.J. Kema, 2 H.-R. Forrer, 3 E.C.P. Verstappen, 2 L.S. Arraiano, 1 P.A. Brading, 1 E.M. Foster, 1 A. 

Hecker, 3 and E. Jenny3 1 John Innes Centre, Norwich, UK 

2 DLO-Research Institute for Plant Protection, Wageningen, The Netherlands 

3 Swiss Federal Research Station for Agroecology and Agriculture, Zürich, Switzerland 

Abstract 

The resistance of 71 varieties of bread wheat to six isolates of Mycosphaerella graminicola was studied in field trials in 

the Netherlands, Switzerland, and the UK, carried out over three years. There was a wide range of Septoria tritici infection. 

Some varieties had especially good resistance, including lines from Europe (especially Switzerland) and Latin America. Many 

interactions between varieties and isolates were detected. In particular, 27 varieties of diverse origins were specifically 

resistant to the isolate IPO323. Variety-by-isolate interactions were stable over years and locations. The existence of these 

interactions and the fact that they are stable over environments implies that certain widely used resistances to Septoria tritici 

might break down through the evolution of specific virulence in the fungus. Breeders should take these interactions into 

account in their efforts to develop varieties with durable resistance. 

Septoria tritici leaf blotch is 

now the most economically 

important foliar disease of wheat in 

Europe, and controlling it with 

fungicides costs several hundred 

million dollars a year. Resistance to 

septoria tritici leaf blotch is 

therefore a major target for most 

European wheat breeders. 

However, if resistant varieties are 

to be economically worthwhile, 

resistance must be both effective 

and durable. 

Strong, specific interactions 

between wheat varieties and 

isolates of the pathogen, 

Mycosphaerella graminicola, have 

been found in both seedlings and 

adult plants (Kema and van 

Silfhout, 1997), while the resistance 

of at least one variety, Gene, has 

“broken down” through the 

evolution of a virulent pathogen 

population (Mundt et al., 1999). 

This means that breeders need to 

know not only which varieties may 

be good sources of resistance in 

breeding programs, but also 

whether or not resistance genes in 

these varieties are at risk from 

virulent isolates of M. graminicola. 

This paper reports a series of 

field trials carried out in England, 

The Netherlands, and Switzerland 

between 1994 and 1997. The aims 

were to investigate resistance to 

septoria tritici leaf blotch in a 

representative set of European 

varieties, to evaluate potential new 

sources of resistance, to study the 

responses of varieties to different 

isolates of M. graminicola and to test 

the stability of variety-by-isolate 

interactions over a range of 

environments. 


A total of 71 wheat varieties of 

diverse origins were included in 

the field trials. The majority were 

cultivars or breeding lines 

developed by European breeders. 

Most of these were winter wheats. 

Several varieties that are potential 

sources of septoria tritici leaf blotch 

resistance were also included, as 

were a number of varieties that are 

parents of precise genetic stocks 

held by the John Innes Centre. 

Trials were inoculated with six 

monospore isolates of M. 

graminicola from the IPO-DLO 

collection. Six trials were 

conducted, three in the 

Netherlands, one in Switzerland, 

and two in England. Each trial was 

sown in a split-plot design with 

two replicate blocks. Within each 

block, there were five or six main

plots, each inoculated with one 

isolate, such that isolates were 

randomized within blocks, while 

varieties were randomized within 

main plots. The percentage of the 

leaf area that was necrotic or 

covered by lesions bearing 

pycnidia was estimated visually. 

Results 

Levels of necrosis and pycnidia 

were highly correlated, so further 

analysis was based on pycnidia 

scores. There was highly significant 

variation between varieties in the 

level of disease and highly 

significant interactions between 

varieties and isolates. However, 

there was no significant variation 

in variety-by-isolate interactions 

among the six trials. This implies 

that variety-by-isolate interactions 

were stable over the range of 

environments used in this series of 

trials. 

There was a wide range of 

resistance among the varieties 

grown in the trials. The existence of 

strong variety-by-isolate 

interactions and the small number 

of isolates used means that one 

cannot be certain which varieties 

have good, overall resistance to the 

European population of M. 

graminicola. However, some lines 

were identified that should be 

tested further, preferably with more 

isolates. The most resistant was the 

Brazilian cultivar Veranopolis, a 

well-known source of resistance. 

Four of the top ten varieties were 

from the FAP breeding program in 

Switzerland, including the popular 

cultivar Arina. Other varieties 

which had very good resistance to 

Field Resistance of Wheat to Septoria Tritici Leaf Blotch, and Interactions with Mycosphaerella graminicola Isolates 149 

the isolates used in these trials 

included cultivars and breeding 

lines from several European 

countries, as well as another 

well-known source of resistance, 

Kavkaz-K4500 l.6.a.4, and 

Frontana, one of the parents of 

Veranopolis. 

Variety-by-isolate interactions 

were most pronounced in tests 

with the isolate IPO323. A total of 

27 cultivars and breeding lines, 

from several European countries, 

China, Israel, and the USA, 

showed specific resistance to this 

isolate. One or more varieties 

showed specific resistance to four 

of the other five isolates, while 

specific susceptibility to four 

isolates was also detected. 

Discussion 

There is good resistance to 

septoria tritici in a wide range of 

European wheat germplasm 

from several countries. Plant 

breeders may be able to exploit 

this resistance by recombining 

quantitative resistance from 

different sources. There may be 

some additional value in 

introducing resistance from 

sources outside Europe. The 

striking success of the Swiss 

breeding program may be 

attributed to a long tradition of 

selection for foliar disease 

resistance, using both artificial 

and natural inoculation. 

Furthermore, trials are conducted 

without fungicides in several 

locations with diverse climatic 

conditions. 

The existence of strong 

variety-by-isolate interactions, as 

well as the fact that they are 

stable over environments, means 

that breeders must take account 

of the possibility that certain 

resistances may not be durable. 

This is particularly the case with 

resistance to IPO323, although it 

is not known if this resistance is 

controlled by the same genes in 

different varieties. One strategy 

for breeding might be to use 

several specific resistance genes 

in a breeding program and aim to 

select varieties with combinations 

of resistances. An alternative 

would be to avoid selecting for 

specific resistances altogether, 

aiming instead for a high level of 

quantitative resistance. 


This research was supported 

in part by the EU Framework 4 

Biotechnology program, the UK 

Ministry of Agriculture, Fisheries 

and Food, and Praxis XXI 

(Portugal). 

References 

Kema, G.H.J., and C.H. van 

Silfhout. 1997. Genetic variation 

for virulence and resistance in 

the wheat-Mycosphaerella 

graminicola pathosystem III. 

Comparative seedling and adult 

plant experiments. 


Mundt, C.C., M.E. Hoffer, H.U. 

Ahmed, S.M. Coakley, J.A. 

DiLeone, and C. Cowger. 1999. 

Population genetics and host 

resistance. In: Septoria on 

Cereals: a Study of 

Pathosystems. J.A. Lucas, P. 

Bowyer, and H.A. Anderson 

(eds.). CAB Publishing, 

Wallingford, UK. pp. 115-130.

150 

Using Precise Genetic Stocks to Investigate the Control of 

Stagonospora nodorum Resistance in Wheat 

C.M. Ellerbrook, 1 V. Korzun, 2 and A.J. Worland 1 (Poster) 

1 John Innes Centre, Colney, Norwich, UK (Poster) 

2 IPK, Gatersleben, Germany 

Abstract 

A substitution series of ‘Synthetic 6x’ into ‘Chinese Spring’ had previously been studied to determine which of the 21 

chromosomes of ‘Synthetic 6x’ conferred resistance to Stagonospora nodorum; from this single chromosome recombinant 

lines (SCRs) have been developed for substitution lines that improve the resistance of ‘Chinese Spring’ to the pathogen. The 

SCRs were screened for their response to infection. Marker assisted screening was also employed on the SCR populations; 

micro-satellite, RFLP and iso-electric focusing, coupled with conventional QTL analysis and morphological character scoring 

(vernalization response). As these markers had been previously mapped, it would be possible to pinpoint the resistance gene(s) 

and find a linked marker. Chromosome 5D had been shown to be the most effective against Stagonospora nodorum and is 

also known to carry the isozyme genes, Ibf-1 and Mdh-3, a range of micro-satellite markers, a sparse selection of RFLP 

markers, and a vernalization response gene (Vrn 3). Screening revealed that the resistance gene (Srb3) was located on the 

long arm between Ibf-1 and the RFLP probe Xpsr 912, but being 15.6 and 12.0 cM, respectively, away from Srb3, they could 

not be used as markers for resistance. SCRs have been developed for the remaining chromosomes, and screening continues to 

precisely map the resistance gene(s). 

Stagonospora nodorum (Septoria 

nodorum Berk.) is the causal agent 

of leaf and glume blotch in wheat 

with infection reducing yield by up 

to 40%. Conventional fungicide 

control has significant 

environmental and economic 

consequence, thus alternative 

methods of control are being 

sought. Several Aegilops species 

including Ae. squarrosa exhibit 

partial resistance to the pathogen. 

This resistance is expressed in a 

synthetic amphiploid ‘Synthetic 6x’ 

derived from a cross between Ae. 

squarrosa and Triticum dicoccum 

(McFadden and Sears, 1946; Sears, 

1976). A substitution series of 

‘Synthetic 6x’ chromosomes into 

‘Chinese Spring’ was developed 

and is maintained at the John Innes 

Centre. This series was utilized in 

disease tests to determine the 

chromosomal location of the 

resistance gene(s) (Nicholson et al., 

1993) as ‘Chinese Spring’ was 

shown to be susceptible to 

Stagonospora nodorum (Scott and 

Benedikz, 1977). 

From the D genome Ae. 

squarrosa parent, chromosome 5D 

conferred a high level of resistance, 

as did 3D and 7D. Resistance was 

most pronounced in 5D where the 

percentage leaf infection was near 

to that of the amphiploid. Three 

chromosomes from the T. dicoccum 

parent (AB genome) 2A, 3B, and 5A 

conferred resistance but to a lesser 

extent than that promoted by the D 

genome chromosomes. SCRs were 

then developed for these 

chromosomes. This paper reports 

the results of experiments to 

localize the resistance genes and 

assign markers linked to the genes. 


Single chromosome 

recombinant lines were developed 

by crossing the individual 

chromosome substitution lines, 

previously identified as conferring 

resistance, to ‘Chinese Spring’ 

euploid (or ditelocentric), and then 

backcrossing the F 1 with the 

corresponding monosomic from 

the ‘Chinese Spring’ monosomic 

series (Sears, 1954). Monosomic 

plants were then selected in the 

backcrossed F 1 progeny and selfed 

for disomic extraction (Figure 1). 

Infection response was scored 

on juvenile plants. Seeds had been 

placed on moist filter paper in petri 

dishes and incubated at 25 o C for 2 

days (with 2 days cold shock at 4 o C 

to promote germination if 

necessary) and then planted 

individually in pots of John Innes 

no. 2 compost. In all experiments 

the plantlets were grown fully 

randomized over 10 replications 

with an additional uninfected 

replicate as a control.

The seedlings were inoculated 

when the second leaves were fully 

expanded with a 1 x 10 6 spore/ml 

suspension of an aggressive isolate 

(S353/88). The plantlets were then 

placed in propagators and 

transferred to growth chambers for 

72 h at 15 o C in complete darkness 

to establish infection. Once this had 

been completed, the plants were 

moved to a containment glasshouse 

and removed from their 

propagators. Disease was scored at 

10 and 17 days post-inoculation 

and expressed as the percentage of 

leaf area lesioned (at the intervals 1, 

5, 10, 25, 40, 60, 75, 90, and 100%). 

The scores were transformed using 

the angular transformation and an 

analysis of variance carried out 

using the GENSTAT 5 statistical 

package. The significance of 

Chinese Spring ditelocentric for the long arm 

(2n = 42 tt) 

Background 

Chinese Spring monosomic (2n = 41) 

Selfing of each monosomic plant 

Using Precise Genetic Stocks to Investigate the Control of Stagonospora nodorum Resistance in Wheat 151 

differences in the mean scores 

relative to ‘Chinese Spring’ and 

‘Synthetic 6x’ was estimated using 

a two-tailed t-test. 

Morphological characters were 

scored on field plots, with three 

replicates of 11 plants in 

randomized blocks to enable QTL 

analysis and screening for Vrn3. 

Biochemical analysis involved 

the isoelectric focusing technique, 

using seed embryo or endosperm 

on flat bed electrophoresis 

apparatus, showing separation of 

the proteins at their relevant 

isoelectric points (pI) (Liu and 

Gale, 1989). 

X 

X 

Cs/Syn 5D (2n = 42) 

Selection of monosomic plants (2n = 41 ) or monotelosomics (2n = 41 t) 

Selection of disomic (2n = 42) single chromosome recombinant lines (SCRs) 

Figure 1. Development of single chromosome recombinant lines (SCRs) for the long arm of chromosome 

5D (18). 

F1 

Molecular marker techniques 

required extraction of DNA (phenol 

chloroform method) and in the case 

of RFLPs digesting with enzymes 

that have a 4 base-pair recognition 

sequence (Bam HI, Eco RI) and 

then hybridizing with P 32 labeled 

CTP (Southern, 1975). The microsatellite 

technique was PCR-based 

and used micro-satellite probes 

developed at IPK-Gatersleben. Both 

techniques clearly revealed the SCR 

progeny as either ‘Chinese Spring’ 

or ‘Synthetic 6x’ type. 

Marker results were input into 

Mapmaker (Lincoln et al., 1992) to 

compare the segregation of 

markers in the progeny, and a map 

of resistance gene(s) location 

5D

Session 6C — C.M. Ellerbrook, V. Korzun, and A.J. Worland 

152 

related to the markers analyzed 

was compiled. QTLs were also 

assigned to markers on the 

chromosome using the Students ttest. 

To date only the 5D SCR 

population has been analyzed for 

disease resistance and associated 

markers. 

6.8 cM 

8.2 cM 

2.1 cM 

3.2 cM 

12.0 cM 

12.0 cM 

15.6 cM 

7.8 cM 

7.4 cM 

16.1 cM 

7.4 cM 

10.3 cM 


Following analysis of the 5D 

population (85 lines), it was found 

that S. nodorum resistance was 

under the control of a single gene 

Srb3, which was located between 

Ibf-1 and Xpsr 912, with a QTL for 

plant height (Qph) being linked to 

Ibf-1 (Figure 2). However, these 

genes are too remote from Srb3 to 

Mdh 3 

Wms 205 

Dms 3 

Xpsr 628 

Xpsr 906 

Xpsr 574 

Xpsr 912 

Srb 3 

Ibf-1 

Wms 182 

Wms 174 

Wms 292 

Xpsr 819 

Vrn 3 

Qsy (QTL for plant yield) 

Qey (QTL for ear yield) 

Qph (QTL for plant height) 


be useful as flanking markers. 

Work is continuing to locate more 

markers on chromosome 5D, as the 

region in which Srb3 is located 

currently has a low marker 

concentration. RFLP screening is 

also underway with recently 

developed markers and with the 

collaboration at IPK-Germany; any 

new 5D micro-satellites produced 

will also be screened. It is hoped 

Qsn (QTL for spikelet number) 


Figure 2. Relative position of the Stagnospora nodorum resistance gene Srb3 and previously mapped markers.

that this continuing work will help 

to complete the map more 

successfully. 

Mapping, field trials, and 

disease screening are now in 

progress on the SCR populations 

for chromosomes 2A, 3D, and 7D. 

Our results have shown that S. 

nodorum resistance in wheat is 

inherited in a complex manner 

involving several genes. By 

studying them in single 

chromosome recombinant lines, we 

should be more able to fully 

understand their heritability as 

well as highlighting linked 

markers. 

Using Precise Genetic Stocks to Investigate the Control of Stagonospora nodorum Resistance in Wheat 153 

References 

Lincoln, S.E., Daly, M., and Lander, 

E.S. 1992. Constructing genetic 

maps with MAPMAKER/EXP 3.0. 

Whitehead Institute Technical 

Report (Second edition). 

Lui, C.J., and Gale, M.D. 1989. Ibf-1, a 

highly variable marker system in 

Triticeae. TAG 77:233-240. 

McFadden, E.S., and Sears, E.R. 1946. 

The origin of Triticum spelta and its 

free-threshing hexaploid relatives. 

J. Heredity 37:81-89 and 107-116. 

Nicholson, P., Rezanoor, H.N., and 

Worland, A.J. 1993. Chromosomal 






Breeding 110:177-184. 

Scott, P.R., and Benedikz, P.W. 1977. 

Septoria Plant Breeding Institute 

Annual Report 128-129. 

Sears, E.R. 1954. The aneuploids of 

common wheat. Missouri 

Agricultural Experimental Station 

Research Bulletin 572, pp. 1-58. 

Sears, E.R. 1976. A synthetic 

hexaploid wheat with fragile 

rachis. Wheat Information Service 

41-42, 31-32. 

Southern, E.M. 1975. Detection of 

specific sequences among DNA 

fragments separated by gel 

electrophoresis. J. Mol. Biol. 

98:503-517.

154 

Evaluating Triticum durum x Triticum tauschii Germplasm 

for Resistance to Stagonospora nodorum 

L.R. Nelson 1 and M.E. Sorrells 2 (Poster) 

1 Agricultural Research & Extension Center, Texas A&M University, Overton, TX, USA 

2 Dept. of Plant Breeding, Cornell University, Ithaca, NY, USA 

Abstract 

This study was conducted to determine resistance of 50 CIMMYT Triticum durum x Triticum tauschii populations to 

septoria glume blotch. Seedlings were inoculated at the 2-leaf stage, and data were recorded on disease severity and latent 

period. Several lines from this population demonstrated good resistance compared to check entries and are being used as 

sources of resistance to septoria glume blotch in the wheat breeding program. 

Septoria glume blotch caused 

by Stagonospora nodorum is a 

significant disease of wheat in the 

southern and eastern USA. 

Immunity of wheat to S. nodorum 

has not been found (Dantuma, 

1955), but variation in resistance is 

apparent. New sources of genetic 

resistance are needed in order to 

reduce yield losses cause by this 

fungal disease. In our research we 

have studied components of partial 

resistance (Nelson and Marshall, 

1990). A relatively simple test to 

evaluate resistance is based on 

measuring incubation period and 

disease severity at a different 

length(s) of time after inoculation. 

In this study, we utilized these two 

components to evaluate resistance 

of wheat germplasm to septoria 

glume blotch. The objective of this 

study was to screen a collection of 

50 exotic CIMMYT germplasm 

accessions for resistance to septoria 

glume blotch, and compare any 

resistance found with that of 

moderately resistant checks to 

determine the potential of exotic 

germplasm. 


Seed of 50 CIMMYT 

populations and a susceptible 

(TAM 107) and a resistant (TX76- 

40-2) check (Nelson et al., 1994) 

were planted in rows in soil in flats. 

The CIMMYT germplasm consisted 

of 50 amphiploids from crosses 

between Triticum durum and 

Triticum tauschii obtained from Dr. 

A. Mujeeb Kazi, CIMMYT, via Dr. 

Mark Sorrells at Cornell University. 

The wheat was germinated and 

grown in the greenhouse until the 

2-leaf stage. At that time spores of 

S. nodorum were sprayed on the 

wheat, which was then placed in a 

humidity chamber. The plants were 

removed from the humidity 

chamber after 50 hours. During this 

50 hour period, a cool mist blower 

operated for 15 minutes every 2 

hours during the day, and for 15 

minutes every 4 hours during the 

night, which kept the leaves moist, 

but did not cause run-off. After the 

50-hour period, the flats were 

removed from the chamber and 

allowed to continue growing in the 

greenhouse. Five days after being 

removed from the humidity 

chamber, some plants began to 

show leaf necrosis. Disease ratings 

were recorded for each row, or 

entry, on a 0 to 9 disease rating (0 = 

no symptoms; 9 = severe necrosis) 

on day 5, 8, and 11, to obtain an 

estimate of incubation period and 

disease severity. A mean rating 

over the above three days was also 

calculated. 

Results 

Data are presented in Table 1 

for each day’s rating and the mean 

disease rating. The susceptible and 

resistant checks provided a 

benchmark or standard upon 

which to compare these lines. Any 

lines that have disease ratings 

similar or less than the resistant 

check (TX76-40-2) may be useful in 

a wheat-breeding program and 

could provide new resistance. Any 

lines similar to the susceptible 

check TAM 107 will not be useful 

for increasing resistance to septoria 

glume blotch. TAM 107 was 

already highly diseased by day 5, 

indicating a very short incubation 

period. Some lines had low disease 

ratings on day 5, but by day 11, had 

high disease ratings, similar to 

TAM 107. This indicates a longer 

incubation period, and this 

resistance may be useful in a 

breeding program to delay the 

buildup of the disease.

Table 1. Disease rating of CIMMYT durum x T. 

tauschii wheat lines for septoria glume blotch on 

a 0 to 9 scale where 0 = no disease and 9 = very 

high disease rating. 

Rating Rating Rating Mean 

Entry number day 5 day 8 day 11 rating 

TAM 107 Susc. Ck 7 7 7 7 

Syn-1 Altar 21 3 7 7 6 

Syn-2 Altar 219 1 4 6 4 

Syn-3 Altar 219 4 6 6 5 

Syn-4 Altar 219 7 6 6 6 

Syn-5 Altar 224 7 7 7 7 

Tx76-40-2 Res. Ck 0 1 1 1 

Syn-6 Altar 224 4 3 4 4 

Syn-7 Altar 224 3 3 6 4 

Syn-8 Altar 221 3 4 6 4 

Syn-9 Altar 223 1 2 3 2 

Syn-10 Altar 223 2 3 4 3 

Syn-11 Altar 192 1 3 4 3 

Syn-12 Altar 198 1 3 2 2 

Syn-13 Altar 198 0 0 1 1 

Syn-14 Altar 198 1 2 2 2 

Syn-15 Altar 211 1 3 2 2 

Syn-16 Chen 205 7 6 7 7 

Syn-17 Chen 205 8 8 8 8 

Syn-18 Chen 205 6 7 7 7 

Syn-19 Chen 205 5 5 5 5 

Syn-20 Chen 205 3 3 5 4 

Syn-21 Chen 205 2 3 5 3 

Syn-22 Chen 205 5 5 7 6 

Syn-23 Chen 205 4 4 6 5 

Syn-24 Chen 205 3 3 3 3 

Syn-25 Chen 205 5 5 5 5 

Syn-26 Chen 215 3 3 3 3 

Syn-27 Chen 215 0 2 2 1 

Syn-28 Chen 224 7 6 6 6 

Syn-29 Chen 224 7 7 4 6 

Syn-30 Chen 224 7 7 4 6 

Syn-31 Chen 224 4 5 5 5 

Syn-32 Chen 224 3 3 4 3 

Syn-33 Chen 224 5 5 5 5 

Syn-34 Chen 224 3 5 5 4 

Syn-35 Chen 224 6 6 6 6 

Syn-36 Chen 224 6 6 4 5 

Syn-37 Chen 224 7 7 7 7 

Syn-38 Chen 224 5 6 6 6 

Syn-39 Cndo/R143// 

Ent “S”/Mex 214 7 6 6 6 

Syn-40 “ “ 5 6 5 5 

Syn 41 “ “ 3 5 5 4 


Ent”S”/Mex 221 5 5 5 5 


Ent”S”/Mex 221 5 4 4 4 

Syn-45 “ “ 4 7 7 6 

Syn-45 “ “ 3 4 5 4 

Syn-46 “ “ 6 7 6 6 

Syn-45 Laru’s 309 3 5 5 4 

Syn-48 5 6 6 6 

Syn-49 “ “ 8 7 8 8 

Syn-50 “ “ 2 3 3 3 

Evaluating Triticum durum x Triticum tauschii Germplasm for Resistance to Stagonospora nodorum 155 

Highly resistant lines were 

Syn 9, Syn 12, Syn 13, Syn 14, 

Syn 15, and Syn 27. Their 

resistance was similar to TX76- 

40-2. Moderately resistant lines 

were Syn 10, Syn 11, Syn 32, and 

Syn 50. Several other lines also 

demonstrated a moderate 

degree of partial resistance. 

Lines Syn 1 through 15 may 

have a similar genetic 

background for the A and B 

genomes because they all have 

Altar as the durum parent. Of 

the resistant lines, the T. tauschii 

parents were 223 for Syn 9 and 

10, 192 for Syn 11, 198 for Syn 

12-14 and 211 for Syn 15. ‘Chen’ 

and ‘Laru’ “S” were the durum 

parents for Syn 27 and 50 and 

the T. tauschii lines were 215 and 

309, respectively. It appears that 

at least some of the resistance in 

this germplasm originated in the 

T. tauschii lines used to make the 

amphiploids. 

Discussion 

It appears that we have 

several promising new sources 

of resistance in a wheat 

background that can be crossed 

with our adapted winter wheat. 

We are presently increasing seed 

of these 50 lines in our 

greenhouse. We have crossed 

several of the best lines for 


with both hard and soft red winter 

wheat in our crossing program 

during 1998/99. Since this 

germplasm contains sources of 


which are likely not present in our 

soft red winter wheat, there may be 

an opportunity to pyramid genes 

and make significant improvement 

in resistance to this disease. 


Appreciation is expressed to 

CIMMYT for developing and 

sharing the germplasm. 

References 

Dantuma, G. 1955. The heavy attack 

of diseases during the ripening of 

wheat in 1954. Euphytica 5:94-95. 

Nelson, L.R., R.D. Barnett, D. 

Marshall, C.A. Erickson, M.E. 

McDaniel, W.D. Worrall, N.A. 

Tuleen, and M.D. Lazar. 1994. 

Registration of TX76-40-2 wheat 

germplasm. Crop Sci. 34:1137. 

Nelson, L.R., and D. Marshall. 1990. 


Septoria nodorum and Septoria 

tritici. Advances in Agronomy 

44:257-277.

156 

Sources of Resistance to Septoria passerinii in Hordeum 

vulgare and H. vulgare subsp. spontaneum 

H. Toubia-Rahme and B.J. Steffenson (Poster) 

North Dakota State University, Department of Plant Pathology, Fargo, ND, USA 

Abstract 

Septoria speckled leaf blotch (SSLB), incited by Septoria passerinii and Stagonospora avenae f. sp. triticea, has 

become one of the most serious diseases of barley in the Upper Midwest region of the USA. In barley SSLB can cause 

significant losses in both the yield and quality. The major malting and feed barley cultivars in the Upper Midwest are very 

susceptible to SSLB. Resistance breeding is the most effective strategy for controlling this disease. A diverse group of barley 

germplasm including Hordeum vulgare subsp. spontaneum accessions, advanced midwestern breeding lines, and 

commercial cultivars was evaluated at the seedling stage in the greenhouse for reaction to S. passerinii. Of 200 accessions 

tested, 79 were found resistant. Most of H. vulgare subsp. spontaneum accessions (17 of 24) were resistant to S. passerinii. 

These accessions all originated from the Middle East, except one that was from Tibet. Most of the advanced midwestern 

breeding lines found resistant to this pathogen have Gloria”S”/Copal”S” (an ICARDA/CIMMYT barley line) in their 

pedigree, which is believed to be a source of resistance to S. passerinii. From this study, it is evident that many barley 

accessions possess resistance to S. passerinii. Additional evaluations will be made on this germplasm to S. avenae f. sp. 

triticea to identify accessions that possess effective resistance to both SSLB pathogens. 

Septoria speckled leaf blotch 

(SSLB), caused by Septoria passerinii 

and Stagonospora avenae f. sp. 

triticea, has become an increasingly 

important disease of barley 

(Hordeum vulgare L.) over the past 

decade in the Upper Midwest 

region of the USA. In surveys of 

North Dakota barley fields in 1998, 

S. passerinii and S. avenae f. sp. 

triticea were recovered from 45% 

and 37% of leaves exhibiting leaf 

spot symptoms, respectively 

(Krupinsky and Steffenson, this 

volume). Yield losses of 20% have 

been recorded in barley due to S. 

passerinii infection (Green and 

Bendelow, 1961). In recent trials 

conducted in North Dakota, yield 

losses of 23% to 38% were 

observed in Robust barley infected 

with SSLB (J. Lukach and B. 

Steffenson, unpublished data). In 

addition to reducing yield, SSLB 

also reduces kernel plumpness and 

malt extract, which are important 

malt quality characters (Green and 

Bendelow, 1961). 

Host plant resistance provides 

the most practical and 

environmentally safe method of 

disease control. Unfortunately, all 

major malting and feed barley 

cultivars in the Upper Midwest 

region are susceptible to SSLB. The 

objectives of this study were to 1) 

identify sources of resistance to S. 

passerinii in commercial barley 

cultivars, agronomically advanced 

midwestern breeding lines, and 

Hordeum vulgare subsp. spontaneum 

accessions; and 2) evaluate 

previously reported sources of S. 

passerinii resistance to a 

midwestern isolate of this 

pathogen. 


In total, 200 barley entries 

including 24 H. vulgare subsp. 

spontaneum accessions were 

evaluated at the seedling stage in 

the greenhouse. Five seeds of each 

entry were planted in pots (10 x 10 

cm) filled with a potting mix 

consisting of peat moss (75%) and 

perlite (25%). Slow-release (14-14- 

14, N-P-K, 2 g/pot) and watersoluble 

(15-0-15, N-P-K, 2 g/pot) 

fertilizers were added at the time of 

planting. All seedlings were grown 

in the greenhouse at 20±3ºC with a 

14-h photoperiod. The fungal 

isolate (ND97-15) used in this 

study was obtained from naturally 

infected barley leaves collected 

from a commercial field in 

Bottineau county, North Dakota, in 

1997. For inoculum production, the 

isolate was grown on yeast malt 

agar (YMA) (Eyal et al., 1987) in 

plastic Petri dishes at 21ºC with a 

12-h photoperiod (cool-white 

fluorescent tubes). When pycnidia 

developed and sporulated, mass 

spore transfers were made by 

removing with a sterile needle 

cirrhi from pycnidia and 

transferring them to other YMA 

plates. After 4-5 days of incubation 

under the same conditions, 

pycnidia were harvested by 

flooding the surface of the plates

with double-distilled water and 

scraping the agar surface with a 

rubber spatula. This suspension of 

pycnidia was blended for 30 s in a 

blender to release pycnidiospores 

and then filtered through four 

layers of cheesecloth. Tween-20 

(polyoxyethylene-20-sorbitan 

monolaurate) was added to the 

pycnidiospore suspension at a rate 

of 100 µl/l to facilitate the uniform 

distribution and adsorption of 

inoculum onto the leaf surfaces. 

Barley seedlings were 

inoculated with the pycnidiospore 

suspension (5 x 10 5 

pycnidiospores/ml) at the two-leaf 

stage (10-12 days old). Inoculated 

seedlings were incubated at 21ºC/ 

dark and 25ºC/light for 72 h in 

mist chambers, where the relative 

humidity was maintained near 

100%. The first 40 h of incubation 

was in darkness, followed by a 

photoperiod of 5 h for next two 

days. Plants were allowed to dry 

off slowly before being transferred 

to the greenhouse under the same 

conditions previously described. 

The reaction of the entries to S. 

passerinii was assessed on the 

second leaves of seedlings 17 days 

after inoculation using a 0-5 rating 

scale where 0, 1, and 2 are 

indicative of resistance and 3, 4, 

and 5 of susceptibility. Resistant 

(cv. Atlas) and susceptible (cv. 

Betzes) checks were included in the 

experiment. 


Hordeum vulgare and H. vulgare 

subsp. spontaneum accessions were 

classified as susceptible or resistant 

based on their reaction to S. 

passerinii at the seedling stage. 

Sources of Resistance to Septoria passerinii in Hordeum vulgare and H. vulgare subsp. spontaneum 157 

Marked differences were observed 

in the reaction of barley accessions 

to S. passerinii infection. In total, 79 

lines were found resistant to S. 

passerinii. Of the 24 H. vulgare 

subsp. spontaneum accessions 

tested, 17 were resistant. These 

accessions all originated from the 

Middle East, except one, which was 

from Tibet. Similar results were 

obtained by Metcalfe et al. (1977) 

who found that all H. vulgare 

subsp. spontaneum accessions 

collected in the Middle East were 

resistant to S. passerinii. 

All of the major 6-rowed 

malting (Foster, Stander, and 

Robust), and 2-rowed feed 

(Bowman, Conlon, and Logan) 

cultivars grown in the Upper 

Midwest region were susceptible. 

Of 120 advanced midwestern 6and 

2-rowed breeding lines, 41 

were resistant. Most of these 

breeding lines have Gloria”S”/ 

Copal”S” (an ICARDA/CIMMYT 

barley line) in their pedigree. This 

line exhibited S. passerinii resistance 

under field conditions in North 

Dakota and is presumed to be the 

source of resistance to S. passerinii 

in these breeding lines (J. 

Franckowiak, personal 

communication). 

Nine accessions (AC Hamilton, 

Atlas, Bolron, CIho 4439, CIho 

4780, CIho 10644, Feebar, Nomini, 

and Starling) previously reported 

to have resistance to S. passerinii 

were also resistant to the North 

Dakota isolate (ND97-15) used in 

this study. Other barley accessions 

resistant to this isolate were: Atlas 

54, Baronesse, Belford, CIho 4428, 

CIho 4940, Flynn 1, Glacier, and 

Vaughn. Only a few studies have 

been advanced on the genetics of 

resistance in barley to S. passerinii. 

Peterson (1956) indicated that the 

variety Atlas possesses dominant 

resistance genes to S. passerinii. 

Buchannon (1961) found two 

recessive genes conferring 

resistance to S. passerinii in the 

cultivar Feebar, and Rasmusson 

and Rogers (1963) reported two 

different dominant resistant genes, 

Sep2 and Sep3, in the accessions 

CIho 4780 and CIho 10644, 

respectively. Metcalfe et al. (1970) 

found that a single dominant gene 

governs resistance to S. passerinii in 

CIho 4439. It is evident that many 

barley accessions possess resistance 

to this pathogen; however, none 

has been exploited in midwest 

barley breeding programs, as all of 

the major malting and feed 

cultivars are susceptible to S. 

passerinii. 

Segregating populations 

derived from some of the described 

sources of resistance and 

susceptible commercial cultivars 

are under evaluation in our 

laboratory to study the genetics of 

resistance in barley to S. passerinii 

and to identify molecular markers 

linked to S. passerinii resistance 

gene(s). All accessions found 

resistant to S. passerinii in this study 

will also be evaluated to S. avenae f. 

sp. triticea. This test will enable us 

to identify sources of resistance to 

both S. passerinii and S. avenae f. sp. 

triticea and to determine whether 

resistance to both pathogens is 

governed by the same or by 

different gene(s). The development 

of barley cultivars with resistance 

to both S. passerinii and S. avenae f. 

sp. triticea is necessary, as both 

pathogens are common in the 

Upper Midwest production area.

Session 6C — H. Toubia-Rahme and B.J. Steffenson 

158 

References 

Buchannon, K.W. 1961. Inheritance of 

reaction to Septoria passerinii Sacc. 

and Pyrenophora teres (Died.) 

Drechsl., and of row number, in 

barley. Ph.D. diss. University of 

Saskatchewan, Saskatoon. 40 pp. 







Green, G.J., and V.M. Bendelow. 1961. 

Effect of speckled leaf blotch, 

Septoria passerinii Sacc., on the 

yield and malting quality of barley. 

Can. J. Plant Sci 41:431-435. 

Metcalfe, D.R., Buchannon, K.W., 

McDonald, W.C., and E. Reinbergs. 

1970. Relationships between the 

‘Jet’ and ‘Milton’ genes for 

resistance to loose smut and genes 

for resistance to other barley 

diseases. Can. J. Plant Sci 50:423- 

427. 

Metcalfe, D.R., Chiko, A.W., Martens, 

J.W., and A. Tekauz. 1977. Reaction 

of barleys from the Middle East to 

Canadian pathogens. Can. J. Plant 

Sci 57: 995-999. 

Peterson, R.F. 1956. Progress report, 

Cereal Breeding Laboratory, 

Winnipeg, Manitoba, 1949-54. 36 

pp. 

Rasmusson, D.C., and W.E. Rogers. 

1963. Inheritance of resistance to 

Septoria in barley. Crop Sci 3:161- 

162.

Partial Resistance to Stagonospora nodorum in Wheat 159 

Soft Red Winter Wheat with Resistance to Stagonospora 

nodorum and Other Foliar Pathogens 

B.M. Cunfer1 and J.W. Johnson2 (Poster) 

1 Department of Plant Pathology, and 2 Department of Crops and Soils, Griffin Campus, University of Georgia, 

Griffin, GA, USA 

Soft red winter wheat 

germplasm adapted to the 

southeastern USA that has a high 

level of resistance to Stagonospora 

nodorum has been difficult to 

identify. Some partially resistant 

cultivars with long-lasting 

resistance have been developed, 

but these are replaced frequently 

due to loss of resistance to 

powdery mildew (Blumeria 

graminis), leaf rust (Puccinia 

recondita), and Hessian fly 

(Mayetiola destructor). Four lines, 

GA 84202, GA 85240, GA 85410AB, 

and GA 861460, with good 

agronomic traits have been selected 

and included among elite lines in 

the Georgia wheat breeding 

program in the past eight years. 

These lines have resistance to S. 

nodorum which is equal or better 

than that of older cultivars such as 

Oasis. They are also resistant to 

current populations of leaf rust 

present in the southeastern USA, 

most races of powdery mildew, and 

Hessian fly. 

The lines selected were 

evaluated in the greenhouse and 

field over a six-year period against 

100 or more advanced and elite 

lines and standard check cultivars 

each year. Seedling plants were 

inoculated in the greenhouse each 

year. Adult plants were inoculated 

in the field with S. nodorum and 

exposed to natural infection. Data 

were collected in field trials at 

Griffin and Plains, GA, under 

moderate to severe disease 

pressure from powdery mildew, 

leaf rust, and leaf and glume 

blotch. Results from the 

greenhouse and field were 

generally in good agreement. 

Seeds of each line have been 

deposited in the USDA Small 

Grains Collection, Aberdeen, ID. 

These lines may be useful in other 

regions where they are adapted. 

For example, in addition to being 

agronomically adapted, 85410AB 

and 84202 were found to be 

resistant to stripe rust (P. striiformis) 

and leaf rust in a field trial at 

Colonia, Uruguay, in 1995. These 

lines are facultative wheats 

adapted to winter wheat culture in 

regions with a mild to moderate 

winter climate. They have been 

used as parents in several 

advanced and elite breeding lines 

currently being evaluated in the 

Georgia breeding program.

160 

Partial Resistance to Stagonospora nodorum in Wheat 

C.G. Du, 1 L.R. Nelson, 2 and M.E. McDaniel 3 (Poster) 

1 Dept. of Computer Science, Texas A&M Univ., College Station, TX. USA 

2 Texas A&M Univ. Agri. Res. & Ext. Center, Overton, TX, USA 

3 Soil and Crop Sciences Dept., Texas A&M Univ., College Station, TX, USA 

Abstract 

Seedling plants of parents, F 1 crosses, and F 2 populations were inoculated at the two-leaf stage with spores of 

Stagonospora nodorum in a humidity chamber to determine incubation period (IP), latent period (LP) and necrosis 

percentage (NP). Incubation period, LP, and NP exhibited polygenic inheritance and were controlled by 2-3, 3, and 1-4 genes, 

respectively. Each of the components of partial resistance showed moderate to high heritabilities. 


Stagonospora nodorum, common 

name septoria glume blotch (SGB), 

has been difficult because no genes 

for immunity exist. There are 

numerous sources of genetic 

resistance; however, most have 

been labeled as partial resistance 

and in some manner delay the 

growth of the pathogen. In this 

study our objectives were to 

conduct a quantitative genetic 

analysis of three components of 

resistance to SGB in wheat. Second, 

to compare 10 wheat parents, 21 F 1 , 

and 21 F 2 crosses for foliar disease 

reaction induced by inoculation, 

and third, to investigate the 

heritability estimates and gene 

numbers governing SGB resistance. 


Six soft winter wheat and four 

hard wheat genotypes that varied 

greatly in resistance to SGB were 

used in two incomplete diallel 

crosses. Soft wheat lines were 

TX92D7374, TX82-11, L890682, 

18NT, ‘Coker 9803’, and ‘Coker 

9543’. Hard wheat lines were 

TX91V3308, TX84V344, ‘TAM 300’, 

and SWM14240. SWM14240 is a 

wheat line selected in the 

northwestern US from CIMMYT 

germplasm and therefore is likely 

to have different genes for SGB 

resistance. Seeds were germinated 

on moist filter paper for two days 

and then transplanted into pots 

containing a soil/peat moss 

mixture. Two plants in each pot 

were treated as two samples of the 

particular hybrid or parent. Plants 

were inoculated and placed in a 

humidity chamber for 50 h, as 

previously described (Nelson, 

1980). Hayman’s approach (1954) 

was used to calculate components 

of genetic variations. 

Results 

Estimation of components 

of variation 

Hard winter wheat: Incubation 

period. Parents with the highest 

frequency of dominant alleles have 

the smallest Vr (variance) and Wr 

(parent-offspring covariance); thus 

their relative position along the Vr/ 

Wr regression line reflects the 

frequency of dominant alleles. 

Sorting the parents used in these 

crosses in order of decreasing 

dominance gave the follow 

sequence: TX91V3308, TAM 300, 

TX84V344, and SWM14240. 

SWM14240 had least dominant 

effect (Figure 1). The fixable 

variation D and the dominance 

component H were calculated 

(Table 1). Narrow sense heritability 

was 66% and 61% in F 1 in F 2 

generations, respectively. Gene 

number governing the incubation 

period was 2-3 (Table 1). 

Latent period. The analysis of Wr, 

Vr, and Wr/Vr graphical statistics 

in both F 1 and F 2 provided detail 

information on the interrelation 

between the parents. The order of 

decreasing dominance was 

TX84V344, TAM 300, TX91V3308, 

and SWM14240 for F 1 (Figure 1); 

TAM 300, TX91V3308, TX84V344, 

and SWM14240 for F 2 . Average 

degree of dominance was partial 

dominance because of the positive 

intercepts. SWM14240 had the least 

dominant effect. TAM 300 had the 

2.0 

(F1 LP) 4 

4 

(F2 LP) 

Wr 

2 

1 

4 

(F1 LP) 

0.5 

0 

3 

2 

1 

3 

1 

3 

1 

2 

3 

2 

4 

(F1 LP) 

0.5 Vr 2.0 

Figure 1. Parent-offspring covariance (Wr)/ 

variance (Vr) for SNB incubation period and 

latent period of F1 and F2 hard winter wheat 

crosses. 

1 = TX91V3308 2 = TX84V344 

3 = TAM 300 4 = SWM14240

largest dominant effect. Narrow 

sense heritability was 64% and 68% 

in F 1 and F 2 generations, 

respectively (Table 1). There were 

about three genes governing the 

resistance of latent period. The 

additive effect D and dominance 

component H1 and H2 were also 

calculated. Additive D was 3.74 for 

the F 1 and 3.75 for the F 2 

generation. 

Soft winter wheat: Incubation 

period. The order of decreasing 

dominance was TX82-11, 

TX92D7374, 18NT, Coker 9803, 

Coker 9543, and L890682 for F 1 , 

and TX82-11, 18NT, Coker 9803, 

Coker 9543, L890682, and 

TX92D7374 for F 2 generations. 

Mean square of Wr-Vr was not 

significant. Dominance seems to 

account for the major proportion of 

the non-additive variation. The 

additive variation D and the 

dominant component H were 

estimated in Table 2. The 

dominance ratio H1/D, an estimate 

of the average level of dominance, 

was 0.7 and 0.6 for F 1 and F 2 

generations, respectively. This 

indicates that resistance for 

incubation period was partially 

dominant. There were 2-3 genes 

controlling IP in the soft wheat. 

Percent necrosis. The order of 

decreasing dominance was TX82- 

11, 18NT, Coker 9803, TX92D7374, 

Coker 9543, and L890682. 

Dominance and non-allelic 

interaction was important in 

necrosis. H/D>1 indicates that 

necrosis had over-dominance 

effects (Table 2). Heritability 

estimated for necrosis was similar 

by different methods of calculation. 

Narrow sense heritability for 

necrosis was relatively low. Only 

one gene controlled % necrosis in 

soft winter wheat. It was different 

from hard winter wheat and may 

have resulted from the genotype X 

environment interaction-over 

dominance effects. 

Discussion 

Nelson and Marshall (1990) 

stated that resistance that reduced 

the infection rate had polygenic 

inheritance. Jeger (1980) indicated 

that resistance to SGB may involve 

four independent polygenes. The 

results of this study agree with 

these previous studies. IP, LP and 

PN had polygenic inheritance. 

Incubation period, LP, and NP were 

controlled by 2 to 3, 3, and 1 to 4 

genes in the hard and soft wheat 

studies, respectively. Previous 

studies (Nelson 1980; Mullaney et 

al., 1982; Scott et al., 1982) also 

provided evidence for polygenic 

control of host reaction to S. 

nodorum both at the seedling plant 

stage and the mature plant stage. 

The most accepted hypothesis is 

that these polygenes are 

Table 1. Genetic variation of components of partial resistance for hard winter wheat crosses. 

Incubation period Latent period Necrosis 

Component F1 F2 F1 F2 F1 F2 

D 2.51 2.38 3.74 3.75 365.76 360.37 

H1 2.03 2.51 2.16 2.34 459.48 441.15 

H2 0.88 1.34 1.33 0.52 265.07 59.52 

F 2.40 1.87 3.10 3.24 475.17 350.18 

E 0.32 0.51 0.76 0.70 37.12 42.52 

H narrow 66% 61% 64% 68% 30% 77% 

Number of genes 3 2 3 3 4 3 

Partial Resistance to Stagonospora nodorum in Wheat 161 

independently inherited. Our 

research may indicate some of the 

polygenes may have multi-effects. 

For example, one of the latent 

period resistant genes may also be 

a resistant gene in incubation 

period polygenes. 

Analysis of components of 

variation. The H1/D value of F 1 

hard wheat, and F 1 and F 2 soft 

wheat were less than one with the 

exception of F 2 hard winter wheat 

(1.1). This means that additive gene 

action was of greater importance in 

the components in this study. 

Therefore, incubation period could 

be a very useful selection criterion 

for SGB resistant breeding. Both F 1 

and F 2 hard winter wheat crosses 

had larger additive value D than 

dominant value H1. It is likely that 

the non-additive genetic effects 

were due predominantly to 

contribution from additive x 

additive epistatic gene action rather 

than dominance. 

Additive gene action and 

additive x additive epistatic gene 

action are most easily utilized and 

exploited in homozygous 

genotypes. Latent period would 

also be a good selection criterion 

for SGB resistant breeding. H1/D 

values for hard and soft wheat 

crosses were greater than 1. Over 

dominance may have been present 

for necrosis. Nelson (1980), 

Table 2. Genetic variation of components of 

partial resistance for soft winter wheat crosses. 

Component Incubation period Necrosis 

F1 F2 F1 

D 1.19 1.60 3.66 

H 1 0.83 0.92 148.27 

H 2 0.50 1.44 123.54 

F 0.55 1.24 -4.00 

E 0.91 0.72 26.99 

H narrow 32% 39% 22% 

Number of genes 2 3 1

Session 6C — C.G. Du, L.R. Nelson, and M.E. McDaniel 

162 

Wilkinson et al. (1990), and 

Bostwick et al. (1993) had similar 

results. It is reasonable for the 

components of resistance to show 

dominant gene action in the F 1 

generation because of gene 

interaction. From the breeder’s 

viewpoint, necrosis should not be 

an early generation selection 

criterion for SGB resistant breeding. 

Heritability. Estimates of 

heritability in all crosses studied 

were moderate to high. Relatively 

high heritability for spike and flag 

leaf reaction to SGB have been 

estimated in previous studies 

(Rosielle and Brown, 1980; Fried 

and Meister, 1987; Bostwick et al. 

1993). Therefore, early generation 

selection for SGB should be 

effective. 

References 

Bostwick, D.E., H.W. Ohm, and G. 

Shaner. 1993. Inheritance of 

septoria glume blotch resistance in 


Fried, P.M., and E. Meister. 1987. 

Inheritance of leaf and head 

resistance of winter wheat to 

Septoria nodorum in a diallel cross. 

Genetics 77:1371-1375. 

Hayman, B.I. 1954. The theory and 

analysis of diallel crosses. Genetics 

39:789-809. 

Jeger, M.J. 1980. Ultivariate models of 

the components of partial 

resistance. Protection Ecology 

2:265-269. 







Nelson, L.R. 1980. Inheritance of 



Nelson, L.R., and D. Marshall. 1990. 


Septoria nodorum and S. tritici. 

Advances in Agronomy 44:257- 

277. 



Septoria nodorum Berk. in wheat. 



Cox. 1982. A genetic study on the 


of ear emergence, and resistance to 


Pathol. 31:45-60. 


R.R. Rufty. 1990. Diallel analysis of 



Dis. 74:47-50.

Comparison of Methods of Screening for Stagonospora 

nodorum Resistance in Winter Wheat 

D.E. Fraser, 1 J.P. Murphy, 1 and S. Leath 2 (Poster) 

1 Department of Plant Pathology, North Carolina State Univ., Raleigh, NC, USA 

2 Department of Plant Pathology, USDA-ARS, NCSU, Raleigh, NC, USA 

Abstract 

Isolates of Stagonospora nodorum that varied in levels of aggressiveness were used in both controlled environment and 

field tests to determine whether isolate aggressiveness enhanced selection of resistant wheat genotypes. Two segregating wheat 

populations that differed in mean levels of resistance to S. nodorum were developed. Components of resistance measured in 

controlled environments indicated significant differences among isolate treatments. Measurement of disease severity in field 

studies also indicated significant differences among the isolate treatments. For the breeding population (random selections of 

genotypes in F 3 , F 4 , F 5 , and F 6 generations), incubation period measured in both juvenile and adult plant tests were most 

highly correlated with resistance measured in the field. For the biparental population (progeny of a resistant by susceptible 

cross), incubation period and percent leaf area diseased on the flag leaf for adult plant tests were most highly correlated with 

resistance measured in the field. Rankings of genotypes based on their resistance in both field and controlled environment 

tests indicated that five of the ten most resistant genotypes measured under controlled conditions were also identified as 

resistant in field tests. Similarly, four of the ten most susceptible genotypes measured under controlled conditions were also 

identified as susceptible in field tests. Combinations of adult and juvenile screening tests may allow for the identification of up 

to eight of ten genotypes resistant in controlled environments that are also resistant in field tests. 

Glume blotch, caused by the 

ascomycete fungus Stagonospora 

nodorum (teleomorph Leptosphaeria 

nodorum) is an economically 

important disease of wheat. 

Resistance to S. nodorum is 

controlled by multiple genes (Jeger 

et al., 1983; Mullaney et al., 1982; 

Nelson and Gates, 1982; Wilkinson 

et al., 1990) and expression of 

resistance is strongly affected by 

the environment. 

Previous studies attempting to 

correlate components of host 

resistance measured in controlled 

environments with host resistance 

under field conditions have 

reported variable results 

(Wilkinson et al., 1990; Rufty et al., 

1981). A better understanding of 

the relationship between isolate 

aggressiveness and host response 

could provide more effective 

selection methods for resistance to 

S. nodorum. The objective of this 

study was 1) to use isolates with 

different levels of aggressiveness to 

measure differences in components 

of resistance among genotypes in 

two segregating wheat 

populations, under both field and 

controlled environments and 2) to 

determine which components are 

the most effective in selection of 

resistant genotypes. 


Two wheat populations were 

used in all studies. Population 1 

(biparental) consisted of the F3:5 

progeny of NKC 8427 (resistant) by 

Caldwell (susceptible) cross. 

Population 2 (breeding) was 

composed of random F3, F4, F5, 

and F6 lines from a southern US 

soft red winter wheat nursery in 

North Carolina. A total of 50 lines 

from each population were used in 

all studies. A collection of 60 NC 

field isolates was screened in a 

seedling assay and the most 

163 

aggressive isolate and least 

aggressive isolate in the collection 

were selected for further study. The 

same isolate treatments were used 

in all subsequent studies and 

consisted of the most and least 

aggressive isolates (A and D, 

respectively) applied singly, in 

combination (AD), and a noninoculated 

control. 

Field tests 

Hill-plots were planted on a 0.3m 

square grid in three replications 

at Laurel Springs, NC, in 1997 and 

at both Laurel Springs and Kinston, 

NC, in 1998. Each population of 50 

genotypes was inoculated with a 

spore suspension of a different 

isolate treatment at either Feekes 

growth stage (GS) 10.1 in 1997 and 

Feekes GS 9 in 1998. Percent leaf 

area diseased (% LAD) was 

recorded at four bi-weekly 

intervals after inoculation using the 

Saari-Prescott scale.

Session 6C — D.E. Fraser, J.P. Murphy, and S. Leath 

164 

Greenhouse tests 

Seeds of each genotype were 

over-planted and thinned to two 

plants per pot and allowed to grow 

in alternating 12-hour light and 

dark periods at 16 to 26 o C. 

Experimental design was a 

randomized complete block with 

four replications in time. 

At GS 10 the penultimate leaf of 

one plant/pot was marked and a 2 

ml droplet of a single isolate spore 

suspension standardized to 1 x 10 6 

spores ml -1 applied to the leaf. 

Presence/absence of a lesion at 5 

and 10 days was recorded. 

Following the last rating on the 

penultimate leaf of one plant, the 

flag leaf of the other plant/pot was 

marked. Spore suspensions of each 

isolate treatment were applied to 50 

genotypes per population using 

hand atomizers until run-off 

occurred. Glass slides placed in the 

plant canopy during inoculation 

indicated that 50-75 spores were 

deposited per mm -2 . Incubation 

period and % LAD on each plant 

were recorded. 

Growth chamber 


planted and grown for 21 days in 

12 h light and darkness periods in 

day/night temperatures of 22/ 

18 o C. At the 2-leaf stage, spore 

suspensions of the same four 

isolate treatments as described 

previously were applied to 50 

genotypes per population using 

hand atomizers until run-off 

occurred, with approximately 65 

spores deposited per mm -2 of leaf 

tissue. Incubation period and % 

LAD on each plant were recorded. 

Experimental design was a 

randomized complete block with 

four replications. 

Detached leaf test–adult and 

juvenile 


planted and grown in the 

greenhouse for three weeks 

(juvenile) and ten weeks (adult), 

respectively. For the juvenile test, 

fully expanded second leaves were 

cut from each genotype in both 

populations. For the adult test, 

plants were grown to Feeke’s GS 

10.1, and the flag leaf was excised 

from each plant. Each single leaf 

was cut into four equal sized pieces 

and placed on 150 ppm 

benzimidazole agar in a box 

divided in 4-cm grid squares. Each 

grid square represented each of the 

isolate treatments on a single 

genotype. A 2 ml droplet of a single 

isolate spore suspension was 

placed in the center of each leaf 

piece. Incubation period, lesion 

expansion rate, and final lesion size 

was recorded. Both the adult and 

juvenile tests were replicated four 

times. 


The level of resistance in the 

breeding population was generally 

higher than the biparental 

population in all tests. The AUDPC 

values indicated significant 

differences among isolate 

treatments in the field at Laurel 

Springs in 1997 and at both 

locations in 1998 (Table 1). 

Genotype by environment 

interaction was significant. 

Isolate treatments in 

greenhouse evaluations were 

significantly different for most of 

the components of resistance 

measured (Tables 2 and 3). Results 

of inoculations with the most and 

least aggressive isolates in 

combination (AD) were similar to 

inoculations with the most 

aggressive isolate alone and both of 

these treatments resulted in higher 

numbers of lesions, more rapid 

rates of lesion expansion and 

higher % LAD than inoculation the 

least aggressive isolate. Shorter 

incubation periods were not 

consistently associated with the 

most aggressive isolate or the most 

and least aggressive isolate 

together. Components of resistance 

measured in controlled 

environments were highly 

correlated with each other (Table 4). 

Few components of resistance 

measured in controlled 

environments correlated with field 

measured disease severity. A 

comparison of the controlled 

environment studies with field data 

from Kinston in 1998 indicated that 

adult plant incubation period and 

% LAD on the flag leaf for adult 

plant spray inoculation were highly 

correlated (P>0.01) with field 

Table 1. Area under the disease progress curve values for disease severities measured on hill 

plots inoculated with isolates of Stagonospora nodorum. 

Laurel Springs 1997 Laurel Springs 1998 Kinston 1998 

Isolate treatments Breeding Biparental Breeding Biparental Breeding 

A (most) a 2724b 1669b 2196a 1678a 1587a 

D (least) 2783a 1667b 1972c 1557c 1561c 

AD (both) 2770a 1806a 1733d 1608b 1628a 

NI (control) 2694c 1829a 2087b 1367d 1452d 

a ‘Most’ and ‘least’ aggressive refer to isolate reaction measured in the isolate screening assay done on 

seedlings in controlled conditions.

disease severity in the biparental 

population. Adult and juvenile 

plant incubation period and lesion 

expansion rate measured in the 

detached leaf test were highly 

correlated with field disease 

severity measured at Kinston in 

1998 in the breeding population. 

Similar results were obtained 

for disease measured at Laurel 

Springs in 1997. Components of 

resistance were not highly 

correlated with field disease 

measured at Laurel Springs in 1998. 

Comparison of Methods of Screening for Stagonospora nodorum Resistance in Winter Wheat 165 

Resistant genotypes 

A comparison of genotype 

rankings measured in the field with 

those measured in controlled 

environments indicate that for the 

biparental population at Kinston in 

1998, five of the ten most resistant 

genotypes in the field were also 

identified by the measurements of 

the incubation period and % LAD 

on the flag leaf in the adult plant 

tests. Similarly, rankings based on 

% LAD measured in the adult plant 

spray test ranked five of the same 

ten most resistant genotypes 

identified by the field disease 

severity values at Laurel Springs in 

1998. The numbers were slightly 

lower for the breeding population. 

At Kinston in 1998, four of the ten 

most resistant genotypes in the 

field were also identified as 

resistant by measurements of % 

LAD for adult plant spray 

inoculation. Combining adult plant 

greenhouse tests and juvenile 

detached leaf tests could increase 

this number to seven or eight of the 

top ten resistant genotypes 

identified in controlled 

Table 2. Components of resistance to Stagonospora nodorum measured on F 3:5 lines of NKC 8433 x Caldwell cross in controlled environments. 

Dlt a Juvenile Dlt Adult Phytotron(Juvenile) Greenhouse 

Isolate Incubation # of Incubation Lesion Incubation # of Droplet Spray 

treatments b (days) lesions (days) expansion ( days) lesions incubation %LAD 

A (most) 7.9 a 2.4 b 12.7 c 0.14 b 12.9 a 2.4 bc 3.8 a 5.5 ab 

D (least) 8.1 b 2.3 b 10.4 b 0.13 a 13.1 a 1.7 a 4.3 a 3.9 a 

AD (both) 7.6 a 2.7 c 9.4 a 0.20 c 12.9 a 1.8 b 5.4 b 4.8 a 

NI(control) 20.0 c 0.0 a - - 17.1 b 1.2 a 20.0 c - 

a Detached leaf test. 

‘b ‘Most’ and ‘least’ aggressive refer to isolate reaction measured in the isolate screening assay done on seedlings in controlled conditions. 

Table 3. Components of resistance to Stagonospora nodorum measured on random F 3 , F 4 , F 5 and F 6 lines from a southern US winter wheat nursery 

in controlled environments. 

Dlt a Juvenile Dlt Adult Phytotron(Juvenile) Greenhouse 

Isolate Incubation # of Incubation Lesion Incubation # of Droplet Spray 

treatments b (days) lesions (days) expansion ( days) lesions incubation %LAD 

A (most) 8.4 a 2.5 b 12.7 b 0.11 a 13.5 a 2.1 c 5.1 b 3.7 a 

D (least) 9.0 b 2.4 b 10.8 a 0.12 b 12.8 a 1.6 b 3.4 a 2.8 a 

AD (both) 8.3 a 2.4 b 11.0 a 0.19 c 13.7 a 2.2 c 4.9 b 4.1 ab 

NI (control) 20.0 c 0.0 a - - 17.5 b 0.9 a 20.0 c - 

a Detached leaf test. 

b ‘ Most’ and ‘least’ aggressive refer to isolate reaction measured in the isolate screening assay done on seedlings in controlled conditions. 

Table 4. Correlations among resistance components measured in controlled environments and in field tests. 

Treatment A (most) a Treatment AD(most/least) Treatment D(least) 

Resistance component Biparental Breeding Biparental Breeding Biparental Breeding 

Adult dlt – incubation 0.23 * 0.30 * NS NS NS 0.25 * 

Adult dlt- lesion expansion NS -0.34 ** NS NS 0.2 0* 0.20 * 

Juvenile dlt – incubation NS -0.40 ** NS NS NS NS 

Juvenile dlt – lesion size NS NS 0.20 * 0.20* 0.27 * NS 

Adult spray test - %LAD NS NS 0.23 * NS 0.33** 0.14 

a ‘Most’ and ‘least’ aggressive refer to isolate reaction measured in the isolate screening assay done on seedlings in controlled conditions.

Session 6C — C.G. Du, L.R. Nelson, and M.E. McDaniel 

166 

environment tests also being 

identified as resistant under field 

conditions. 

Susceptible genotypes 

Of the ten most susceptible 

genotypes in each population, four 

were also identified as susceptible 

by measurement of juvenile plant 

incubation period. Combining 

results from both the adult plant 

and juvenile plant detached leaf 

tests resulted in as high as seven of 

the ten most resistant genotypes in 

the field also being identified as 

resistant under controlled 

conditions. 

In general, evaluation of 

components of resistance may 

provide a more efficient selection 

method by allowing for the 

removal of extremely susceptible 

types and identification of resistant 

types before large-scale field 

selection. Based on our results and 

practicability to the plant breeder, a 

combination of juvenile detached 

leaf tests and adult plant 

inoculations (droplet or spray) in 

the greenhouse could aid in the 

selection of parental materials with 

resistance to S. nodorum. These 

methods could also be used for 

screening the progeny of 

segregating populations. Highly 

aggressive isolates or combinations 

of isolates with different levels of 

aggressiveness help to maximize 

differences among genotypes in 

both field and controlled 

environments 

Epidemiology 

In addition to measuring 

components of resistance to S. 

nodorum in the field and in 

controlled conditions, molecular 

analyses of the development of the 

epidemics in the field were also 

studied using these same isolate 

treatments and populations. The 

information provided by the 

molecular analyses may explain 

differences among treatments in 

the field and help elucidate the role 

of the natural inoculum in 

epidemic development. 

References 

Jeger, M.J., D.G. Jones, and H. 

Griffiths. 1983. Components of 

partial resistance of wheat 

seedlings to Septoria nodorum. 








Nelson, L.R., and C.E. Gates. 1982. 

Genetics of host plant resistance of 

wheat to Septoria nodorum. Crop 

Sci. 22:771-773. 

Rufty, R.C., T.T. Hebert, and C.F. 

Murphy. 1981. Evaluation of 


wheat. Plant Dis. 65:406-409. 





Dis. 74:47-50.

Response of Winter Wheat Genotypes to Artificial 

Inoculation with Several Septoria tritici Populations 

M. Mincu (Poster) 

Research Institute for Cereals and Industrial Crops, Fundulea, Romania 

Abstract 

A study was conducted to identify genotypic differences in the response of winter wheat to artificial inoculation with 

several Septoria tritici populations. Twenty-two genotypes were grown in two locations and artificially inoculated with four 

Septoria tritici populations. Significant effects of host genotype, pathogen population, and host-pathogen interaction were 

found. Most released cultivars were susceptible. Several entries, including some Aegilops spp. derivatives, were resistant to 

all Septoria populations in both locations. Septoria tritici populations differed both in aggressiveness and virulence. A 

strong host-pathogen interaction was found in several cultivars with medium average resistance. 

Septoria tritici is a major foliar 

disease of wheat in Romania. Yield 

losses caused by septoria leaf 

blotch can reach 25% in years that 

favor the disease. Most currently 

grown wheat cultivars are more or 

less susceptible to Septoria tritici. 

Therefore, resistance to this 

pathogen is a high-priority 

breeding goal. 

Material and Methods 

Twenty-two winter wheat 

genotypes were grown on 2-m+ 

plots using three replications in 

each of two locations (Fundulea in 

the south and Brasov in the central 

part, near the mountains). Artificial 

inoculation was conducted by 

spraying the plants at heading with 

a spore suspension diluted to 10 

spores/ml, from four Septoria tritici 

populations, collected from several 

regions of Romania. After spraying, 

the plants were covered with 

plastic sacks to maintain the 

humidity necessary for infection. 

The intensity of the attack was read 

30 days after inoculation, using the 

0 to 9 scale developed by Saari and 

Prescott at CIMMYT (1995). For 

statistical analysis, the arc sin 

transformation was used. 

Significance of differences among 

genotypes was determined using 

the Duncan test. 


The analysis of variance 

(ANOVA) shows there are 

significant effects of wheat 

genotypes, pathogen populations, 

and host x pathogen interaction 

(Table 1). Genotype classifications 

for each pathogen population in 

the two locations are presented in 

Tables 2 and 3. Most released 

cultivars were susceptible to all 

populations and in both locations. 

On the other hand, several entries 

showed low intensities of attack 

with all populations and in both 

locations (e.g. F91552G8-01, Admis, 

ZE16547, KS93U134, G1662-51, 

G557-5, G557-6). The last four are 

derivatives from crosses with 

Aegilops spp. Finally, some entries 

(such as Turda 81) showed a very 

variable response to different 

Septoria populations. 

167 

The differences between host 

genotypes are more pronounced 

than between pathogen 

populations. The pathogen 

populations produced different 

attack intensities in the two 

locations. In Fundulea, all Septoria 

populations had a higher 

pathogenicity than in Brasov. In 

Brasov, the pathogenicity of all 

populations was approximately 

equal, but in Fundulea Population 

4 was less pathogenic, compared 

with the other populations. The 

host-pathogen interactions in the 

two locations are exemplified in 

Figures 1-4. A strong host-pathogen 

interaction was noticed for several 

cultivars in both locations. 

Reference 

Saari, E.E., and Prescott, M. 1975. A 

scale for appraising the foliar 

intensity of wheat diseases. Plant 

Dis. Rep. 59:377-380. 

Table 1. Analysis of variance (MS) for the 

intensity of Septoria tritici attack on the leaf in 

Fundulea and Brasov. 

Source of variation Fundulea Brasov 

Genotypes (G) 1479.276*** 696.308*** 

Error (a) 81.600 5.582 

Populations (P) 3041.026*** 688.315*** 

G x P 339.740*** 69.820*** 

Error (b) 30.020 3.300

Session 6C — M. Mincu 

168 

Arcsin (sqrt (intensity %)) 

90 

80 

70 

60 

50 

40 

30 

ZE-16547 

G 1662-51 

G 557-5 

KS93U134 

20 

P4 P2 P1 P3 

Septoria tritici populations 

Figure 1. Interaction between genotypes and 

population (intensity of the attack on the leaf), 

Fundulea - sources of resistance. 


90 

80 

70 

60 

50 

40 

30 

Admis 

Dropia 

Lovrin 34 

Turda 81 

Apullum 

20 

P4 P2 P1 P3 




Fundulea - cultivars. 



90 

80 

70 

60 

50 

40 

30 

20 

P1 P4 P3 P2 




Brasov - sources of resistance. 

90 

80 

70 

60 

50 

40 

30 

ZE-16547 

G 1662-51 

G 557-5 

KS93U134 

Admis 

Dropia 

Lovrin 34 

Turda 81 

Apullum 

20 

P1 P4 P3 P2 




Brasov - cultivars. 

Table 2. The reaction of genotypes to Septoria tritici infection–intensity of attack on the leaf in Fundulea. 

Genotypes Population 1 Population 2 Population 3 Population 4 Mean 

ZE16547 26.6 a † 26.6 a 26.6 a 26.6 a 26.6 

G557-5 26.6 a 26.6 a 26.6 a 26.6 a 26.6 

G557-6 26.6 a 26.6 a 26.6 a 26.6 a 26.6 

KS93U134 26.6 a 26.6 a 26.6 a 26.6 a 26.6 

91552G8-01 28.8 a 28.8 a 30.8 a 26.6 a 28.7 

G1662-51 26.6 a 26.6 a 37.2 b 26.6 a 29.2 

649T2-1 28.8 a 33.0 ab 39.2 bc 26.6 a 31.9 

Lovrin 34 51.2 bc 43.1 cde 38.9 bc 34.9 ab 32.3 

Rapid 45.0 b 28.8 a 31.0 ab 26.6 a 32.8 

Admis 26.6 a 49.2 ef 43.3 cd 26.6 a 36.4 

577U1-106 46.9 b 48.9 ef 50.8 d 26.6 a 36.6 

Dropia 44.9 b 36.9 bc 42.7 c 33.0 a 39.4 

93396G1-1 26.6 a 52.8 ef 59.0 ef 26.6 a 41.2 

92033G2-1 55.0 bcd 28.8 a 51.2 de 33.2 ab 42.0 

91375GA-13 57.0 cd 31.0 b 63.9 fg 26.6 a 44.6 

93009G11-12 59.0 de 35.2 abc 61.2 ef 26.6 a 45.5 

Fundulea – 4 61.2 def 46.9 de 55.0 e 35.2 ab 49.6 

93122G6-2 26.6 a 61.2 gh 63.5 f 48.9 d 50.0 

Apullum 68.9 f 30.8 ab 59.7 ef 43.0 bc 50.6 

508U3-201 26.6 a 56.6 fg 72.8 g 46.9 cd 50.7 

Turda 81 83.9 g 43.0 cd 83.9 h 37.2 b 62.0 

Cadril 249 66.2 de 63.9 h 72.3 g 48.9 d 62.8 

† Means in columns followed by the same letter are not significantly different by Duncan’s test at the 0.05% level.

Response of Winter Wheat Genotypes to Artificial Inoculation with Several Septoria tritici Populations 169 

Table 3. The reaction of genotypes to Septoria tritici infection–intensity of attack on the leaf in Brasov. 

Genotypes Population 1 Population 2 Population 3 Population 4 Mean 

ZE16547 26.6 a † 26.6 a 26.6 a 26.6 a 26.6 

G557-6 26.6 a 26.6 a 26.6 a 26.6 a 26.6 

KS93U134 26.6 a 26.6 a 26.6 a 26.6 a 26.6 

91552G8-01 26.6 a 26.6 a 26.6 a 26.6 a 26.6 

Admis 26.6 a 26.6 a 26.6 a 26.6 a 26.6 

649T2-1 26.6 a 28.8 a 26.6 a 26.6 a 27.1 

G557-5 26.6 a 26.6 a 26.6 a 28.8 a 27.1 

Cadril 249 26.6 a 31.0 b 26.6 a 26.6 a 27.7 

G1662-51 26.6 a 33.2 b 26.6 a 26.6 a 28.2 

Rapid 26.6 a 28.8 a 37.2 c 28.8 a 30.3 

93396G1-1 26.6 a 37.2 c 33.2 b 26.6 a 30.9 

93009G11-12 26.6 a 39.2 c 33.2 b 26.6 a 31.4 

508U3-201 26.6 a 37.2 c 35.2 b 26.6 a 31.4 

Apullum 26.6 a 33.2 b 37.2 c 31.0 b 32.0 

Turda 81 33.2 b 26.6 a 43.1 d 31.0 b 33.5 

91375GA-13 31.0 b 45.0 d 35.2 b 26.6 a 34.5 

93122G6-2 26.6 a 45.0 d 37.2 c 31.0 b 35.0 

577U1-106 33.2 b 39.2 c 37.2 c 33.2 c 35.7 

92033G2-1 37.2 d 48.9 e 45.0 d 37.2 d 42.1 

Dropia 33.2 b 56.8 g 43.1 d 50.8 e 46.0 

Fundulea – 4 50.8 e 52.8 f 52.8 e 39.2 d 48.90 

Lovrin – 34 35.2 c 52.8 f 68.9 f 50.8 e 51.92 

† Means in columns followed by the same letter are not significantly different by Duncan’s test at the 0.05% level.

170 

Comparison of Greenhouse and Field Levels of Resistance 

to Stagonospora nodorum 

S.L. Walker, 1,2 S. Leath, 1,3 and J.P. Murphy 2 (Poster) 

1 Department of Plant Pathology, North Carolina State University, Raleigh, USA 

2 Department of Crop Science, North Carolina State University, Raleigh, USA 

3 USDA-ARS, North Carolina State University, Raleigh, USA 

Abstract 

A biparental population of 150 recombinant wheat inbred (RI) lines segregating for reaction to Stagonospora nodorum 

was developed and tested in the greenhouse and field for levels of resistance. The F 3:4 lines were tested in the greenhouse for 

incubation period and percent leaf infection 5 and 10 days after initial symptoms of disease. Plants were tested at both the 

juvenile and adult stages. Adult plants were also tested for percent disease on the spike. The F 3:5 lines were tested in the field 

over four locations for level of adult leaf and head resistance. Heritability of leaf resistance to S. nodorum was calculated to 

be 0.56 on an entry means basis and 0.17 on a per plot basis. Heritability of resistance of the spike was calculated to be 0.57 on 

an entry means basis and 0.20 on a per plot basis. Both heritability estimates are based on field data. Correlations between 

field data and greenhouse data were generally weak, notably between field data and greenhouse performance of juvenile plants. 

However, resistance of the spike in the field and the greenhouse were highly correlated (r = 0.74). 

Resistance to Stagonospora 

nodorum is an economical way to 

control glume blotch as well as a 

component of integrated 

management of the disease. 

Resistance to S. nodorum is complex 

and polygenic, particularly in adult 

plants. There is some evidence that 

resistance in the spike and at the 

juvenile growth stage are under 

different genetic control than adult 

leaf resistance (Eyal et al., 1987). By 

understanding the relationships 

between juvenile, adult leaf, and 

resistance of the spike as well as 

field and greenhouse resistance, 

one could improve progress in 

selecting the most resistant lines. 

Also, an understanding of the 

various components of resistance 

and the epidemiology of glume 

blotch in a given area would allow 

deploying the most useful 

component of resistance in that 

environment. 


A cross of the soft red winter 

wheat cultivars Caldwell= (CItr 

17897) ( mod. susceptible) x Coker 

8427 (9766) (PI601429) (mod. 

resistant) was made, and progeny 

were advanced in bulk to the F 3 

generation. Individual spikes were 

taken from the F 3 generation and 

used to form 150 F 3:4 derived lines. 

The F 3:4 lines were tested in the 

greenhouse for incubation period 

and percent leaf area diseased at 

both the juvenile and adult plant 

growth stages. Percent diseased 

tissue on the spike was measured 

at the adult growth stage. 

A test consisted of a single plant 

from each F 3:4 line using a 

completely randomized design. A 

total of four tests were replicated in 

time during the winter of 1997-98. 

Plants were inoculated with a 

mixture of three S. nodorum isolates 

at a concentration of 1.0 x 10 6 

conidia/ml plus 0.01% Tween 80. 

Inoculations on juvenile plants 

were performed at the three-leaf 

stage, while adult inoculations 

occurred at anthesis. After 

inoculation, plants were kept in 

high humidity for 72 hours. Plants 

were rated each day for incubation 

period, and then at five and ten 

days after the incubation period 

was determined for each individual 

line. Leaf and spike ratings in the 

greenhouse were recorded as a 

percentage of the total leaf or head 

tissue displaying symptoms. Spike 

ratings underwent square root 

transformation prior to statistical 

analysis. 

Field testing was performed 

during the 1998-99 growing season 

at three locations: Johnston Co., 

Lenoir Co., and Ashe Co., North 

Carolina, USA. F 3:5 lines were 

planted as hillplots, consisting of 25 

seeds planted together as a group. 

Hillplots were planted on a grid, 

with 0.3 m separating each plot. 

Three repetitions of each line were 

planted in a randomized complete

lock design within each location. 

Dried wheat straw cut the previous 

season from a field heavily infected 

with S. nodorum was distributed at 

each location to induce disease. 

Overhead irrigation was used at 

the Lenoir and Ashe County 

locations, but was unavailable at 

the Johnston County location. 

Heritability estimates were 

calculated as described by Fehr 

(1991). 

Each hillplot was rated for level 

of disease on the leaf and on the 

spike. Leaf disease ratings were 

done using the double digit scale 

(Eyal et al., 1987), indicating both 

the highest point of disease in a 

hillplot and the percentage of 

disease at that point. Disease on the 

spike was recorded as the 

percentage of diseased tissue and 

underwent square root 

transformation prior to statistical 

analysis. Statistical analysis was 

performed using SAS release 6.12. 

Correlation analysis used the 

Spearman ranked test. 


A range of values for each 

measured trait was produced 

among lines in both the greenhouse 

and in the field (Table 1). The 

Comparison of Greenhouse and Field Levels of Resistance to Stagonospora nodorum 171 

analysis of variance demonstrated 

significant differences among lines 

(p < 0.001) for each trait in both the 

greenhouse and the field (data not 

shown). Using field data, 

heritability of adult leaf resistance 

was calculated and found to have a 

value of 0.56 on an entry means 

basis and a value of 0.17 on a per 

hillplot basis. Heritability of 

resistance of the spike was 0.57 on 

an entry means basis and 0.20 on a 

per plot basis. These data indicate 

the genetic component of resistance 

in this population has a large effect 

on disease expression. Ranking of 

mean resistance scores among lines 

was consistent over three locations. 

Correlation analysis 

demonstrated a negative 

correlation between adult 

incubation period and leaf 

resistance in the greenhouse and 

field, as well as a small positive 

correlation between adult 

greenhouse leaf resistance and field 

leaf resistance (Table 2). The largest 

and most significant correlation 

was between greenhouse and field 

resistance of the spike (0.74). This 

indicates screening for resistance of 

the spike in the greenhouse may 

provide an alternative to field 

testing. In the greenhouse, juvenile 

plant reactions demonstrated little 

Table 1. Means, standard deviations, and ranges of Stagonospora nodorum traits measured in the greenhouse and field. 

correlation with adult plant 

resistance traits either in the 

greenhouse or in the field, 

indicating a possible separate 

genetic mechanism for juvenile 

resistance. Resistance of the spike 

and leaf resistance in the field 

produced a correlation value of 

0.55, indicating some relationship 

between the traits, but a large 

degree of variation between the 

traits remained unexplained. 

We are currently using AFLP 

and RAPD markers in an attempt 

to match polymorphisms at the 

molecular level with traits 

measured in the field and 

greenhouse to gain some insight 

into the genetics of resistance to 

this disease. 

References 

Eyal, Z., A.L. Scharen, J.M. Prescott, 






Fehr, W.R. 1991. Principles of Cultivar 

Development. Vol 1. MacMillan 

Publishing. USA. p. 99. 

Trait Growth Stage and Environment Mean Std. Dev. Min. Max. 

Incubation period Juvenile, greenhouse 5.8 days 0.94 days 4.0 days 10.0 days 

Leaf area disease 

after 5 days Juvenile, greenhouse 5.5% 4.7% 0.5% 30.0% 


after 10 days Juvenile, greenhouse 10.2% 7.8% 0.4% 42.5% 

Incubation period Adult, greenhouse 5.4 days 0.86 days 3.5 days 9.5 days 


after 5 days Adult, greenhouse 8.4% 7.2% 1.0% 48.8% 


after 10 days Adult, greenhouse 27.8% 19.0% 3.0% 90.0% 

Head area disease Adult, greenhouse 3.2% 0.8% 0% 23.0% 

Leaf rating Adult, field 72.1% 7.7% 48.0% 88.8% 

Head rating Adult, field 25.0% 1.0% 0% 100%

Session 6C — S.L. Walker, S. Leath, and J.P. Murphy 

172 

Table 2. Spearman correlation coefficients between Stagonospora nodorum traits measured in the greenhouse and field. 

Adult a Adult b Adult c Adult d Juv. e Juv. f Juv. g Field h Field i 

incub. day 5 day 10 head incub. day 5 day 10 leaf head 

Adult incub. 1.0 -0.40*** -0.36*** -0.11 0.04 -0.12 -0.16* -0.26** -0.13 

Adult day5 -0.40*** 1.0 0.75*** 0.12 0.00 0.16* 0.20** 0.18* 0.21** 

Adult day10 -0.36*** 0.75*** 1.0 0.13 -0.03 0.14 0.18* 0.23** 0.19* 

Adult head -0.11 0.12 0.13 1.0 0.11 0.03 0.06 0.48*** 0.74*** 

Juv. incub. 0.04 0.00 -0.03 0.11 1.0 -0.05 -0.15 -0.08 0.00 

Juv. day5 -0.12 0.16* 0.14 0.03 -0.05 1.0 0.69*** 0.10 0.08 

Juv. day10 -0.16* 0.20* 0.18* 0.06 -0.15 0.69*** 1.0 0.09 0.08 

Field leaf -0.26** 0.18* 0.23** 0.48*** -0.08 0.10 0.09 1.0 0.55*** 

Field head -0.13 0.21** 0.19* 0.74*** 0.00 0.08 0.08 0.55*** 1.0 

*, **, *** p < 0.05, 0.01, 0.0001, respectively. 

a. Incubation period of adult plants in greenhouse test. 

b. Percent leaf area disease of adult plants five days after first sign of disease in greenhouse test. 

c. Percent leaf area disease of adult plants ten days after first sign of disease in greenhouse test. 

d. Percent area head disease of adult plants in greenhouse test. 

e. Incubation period of juvenile plants in greenhouse test. 

f. Percent leaf area disease of juvenile plants five days after first sign of disease in greenhouse test. 

g. Percent leaf area disease of juvenile plants five days after first sign of disease in greenhouse test. 

h. Leaf disease rating in field tests. 

i. Head disease rating in field tests.

Session 6D: Chemical Control 

Adjusting Thresholds for Septoria Control in Winter Wheat 

Using Strobilurins 

L.N. Jørgensen, 1 K.E. Henriksen, 1 and G.C. Nielsen2 1 Department of Crop Protection, Danish Institute of Agricultural Sciences, Slagelse, DK 

2 The Danish Agricultural Advisory Centre, Skejby, DK 

Abstract 

In semi-field trials in spring wheat, azoxystrobin has shown a longer residual and preventive effect on Stagonospora 

nodorum than the triazole propiconazole. Three weeks after application, more than 90% control was still obtained with one 

quarter of the recommended rate of azoxystrobin. Propiconazole gave in comparison only 50% control. In another semi-field 

trial using Septoria tritici, azoxystrobin and propiconazole had a similar curative effect, both being significantly better than 

chlorothalonil. Different dosages (12-100% of normal rate of azoxystrobin) were tested in field trials. When taking into 

account the different timing, the most profitable dose has varied between 50 and 100% of normal rate, depending on growth 

stage and disease pressure. If optimal timing is used, 25-50% of normal rate has generally been sufficient. In 1998 in field 

trials azoxystrobin and the co-formulation propiconazole + fenpropimorph or tebuconazole provided similar control of S. 

tritici when applied after 4 or 8 days of precipitation, respectively. The test model for azoxystrobin recommended between 36 

and 45% of the normal rates. Azoxystrobin gave an increase in yield of 100-600 kg ha -1 above the co-formulation or 

tebuconazole. So far azoxystrobin has shown profitable yields in all trials carried out in Denmark since 1994. However, it is 

still not known how many days of precipitation are required to make spraying with azoxystrobin profitable. 

Based on historical trial data, it 

has been shown that in Denmark an 

economically important attack of 

Septoria tritici or Stagonospora 

nodorum requires more than 7-8 

days of precipitation (>1 mm rain) 

between GSZ 32 and 30 days 

thereafter (Hansen et al., 1994). This 

model has been incorporated into 

the decision support system PC- 

Plant Protection and is widely used 

by Danish farmers as a guide for 

septoria control (Secher et al., 1995). 

Under validation the model has 

given correct answers in 75% of the 

events studied (Jørgensen et al., 

1999). The experience using 

triazoles for control of septoria 

diseases in Denmark has been that 

their application is justified in 

approximately half of the years. 

Adjusting the model for 

strobilurins requires knowledge of 

their preventive and curative effect, 

the residual effect, the dose 

response at different timing, and the 

yield responses measured in relation 

to fungicides. Several of these 

aspects are under investigation 

using azoxystrobin as representative 

of the strobilurins. 


In outdoor semi-field trials, 

spring wheat (cv. Dragon) was 

grown in 8-liter pots using 20 seeds 

per pot and 4 replicates. The plants 

were exposed to normal weather 

conditions (May, June, and July). 

Two types of trials were carried out 

using either artificial inoculation of 

S. nodorum or S. tritici at growth 

stage 39-45. The plants were 

inoculated by spraying each pot 

with 25 ml of a suspension 

containing 2.5 x 10 6 spores ml -1 of 

either S. nodorum or S. tritici. After 

inoculation the pots were covered 

with polyethylene for two days to 

provide high humidity conditions 

173 

for infection. Plants were treated 

with fungicide either after 

inoculation to investigate the 

curative effect, or before inoculation 

to examine the preventive and 

residual effect. Azoxystrobin, 

propiconazole, and chlorothalonil 

were tested at 100-25% of the 

normal rate using a laboratory pot 

sprayer with flat-fan nozzles (Hardi 

4110-14) and a water volume of 167 l 

ha -1 . Percent total coverage of the 

plants by disease as well as percent 

severity on individual leaves were 

assessed. 

Dose response field trials were 

carried out by the Danish Institute 

of Agricultural Sciences (DIAS), and 

the trials testing the septoria model 

using either 4 or 8 days of 

precipitation were conducted by 

DIAS and the Danish Agricultural 

Advisory Centre (DAAC). The 

design of the trials was in the first 

case split plot and in the second

Session 6D — L.N. Jørgensen, K.E. Henriksen, and G.C. Nielsen 

174 

systematic complete block design 

with 5 replicates and a plot size of 

20-32 m 2 . The fungicides were 

applied with knapsack sprayers at 

low pressure (2-3 bar) using flat 

fan nozzles in a volume of 200-300 

l ha -1 . The following products 

were tested: Tilt top (125 g 

propiconazole + 375 g 

fenpropimorph per liter), Folicur 

(250 g/l tebuconazole per liter), 

and Amistar (250 g azoxystrobin 

per liter). Septoria attacks were 

observed in all trials, with S. tritici 

being dominant, but mixed 

infections with S. nodorum were 

also seen. Plots were harvested 

with a plot combine harvester, 

and grain yield was corrected to 

15% moisture content. When 

calculating net yields (profit), the 

prices used were: Tilt top 375 

% control 

10 

8 

6 

4 

2 

- 1 1 1 

Days before and after application 

Figure 1. Curative control of Septoria tritici using 1 / 2 

rate of three different fungicides at different timing. 

12% attack in untreated. 

% control 

50 

40 

30 

20 

10 

vs. 65vs.55- 

Chlorothalonil 

vs.39- DKkr per liter and Folicur 400 

DKkr per liter, Amistar 583 dkr per 

liter, and 60 dkr per application; 

grain price, 750 dkr per ton. Danish 

fungicide prices include a 33% tax. 


Semi-field trials have shown 

that azoxystrobin has a curative 

effect on S. tritici similar to 

propiconazole and much better 

than chlorothalonil (Figure 1). 

Compared to very effective 

triazoles like epoxiconazole, the 

effect of azoxystrobin is, however, 

lower (data not shown). 

Azoxystrobin showed a very 

effective, long preventive effect 

against S. nodorum (Figure 2), 

lasting for three weeks or more. In 

comparison propiconazole + 

Propiconazole 

Azoxystrobin 

vs. 33- 

0 

100 75 50 25 12.5 

Percent of normal dose rate 

Figure 3. Percent attack of Septoria tritici at GS 75 

after application of different dosages 

of azoxystroin at different growth stages. 2 trials, 1998. 

% control 

100 

80 

60 

40 

20 

0 

fenpropimorph had only a residual 

preventive effect for 10 days. In 

field trials the early season effect 

(GSZ 31) of azoxystrobin has been 

found to be inferior to the effect of 

the co-formulation propiconazole + 

fenpropimorph, something which 

has not been observed following 

applications carried out around 

heading (Jørgensen and Nielsen, 

1998). 

Field trials using four different 

dosages of azoxystrobin, along 

with several other trial series 

(Jørgensen and Nielsen, 1998), have 

shown that azoxystrobin and other 

strobilurins may be used at a 

reduced dose (Figures 3 and 4). 

Different dosages, 12-100% of the 

normal azoxystrobin rate, have 

been tested in trials. When taking 

Propiconazole 

Azoxystrobin 

1 6 12 18 24 

Spraying day after inoculation 

Figure 2. Control of Stagonospora nodorum 

preventatively using 1 / 2 rate of two fungicides. 35% 

attack in untreated. 

t/ha 

1.6 

1.2 

0.8 

0.4 

0 

vs.39- vs.65- vs.33- vs.55- 100 75 50 25 12.5 

Percent of normal dose rate 

Figure 4. Net yield in winter wheat after one 

application af azoxystrobin for control of Septoria 

tritici using different dosages and timing. 2 trials, 1998.

into account different timing, the 

most profitable dose under severe 

disease pressure in 1998 varied 

between 50 and 100% of the normal 

rate, depending on growth stage 

and disease pressure. Using 

optimal timing, 50% was sufficient. 

When summarizing results from all 

trials with azoxystrobin, the most 

profitable treatment is most likely 

applied between GSZ 39 and 55, 

using 25 to 50% of the normal dose. 

In three seasons, different 

thresholds have been investigated 

as background for recommending 

spraying azoxystrobin for septoria 

control. In 1998 the difference 

between using a threshold of 4 or 8 

days of precipitation above 1 mm 

was minor (Table 1). Similar results 

were found in two trials in 1997 

(data not shown). In two trials in 

1996, four days was the optimal 

threshold (Jørgensen et al., 1999). 

Mixing azoxystrobin with 

Adjusting Thresholds for Septoria Control in Winter Wheat Using Strobilurins 175 

Table 1. Results from trials using 4 and 8 days of precipitation as a threshold model for control of septoria diseases in winter wheat. 

Treatment 9 trials 1999 No. of appl. TFI a % septoria GS 69-71 Yield and yield inc. (t/ha) Net yield (t/ha) 

Untreated 0 0 21 6.67 

Tilt top 1.0 GSZ 45 1 1 8 1.05 0.47 

PC-P Tilt top 8 days 0.9 0.36 12 0.80 0.55 

PC-P Tilt top 4 days 1.4 0.65 7 0.91 0.47 

Amistar 1.0 GSZ 45 1 1 7 1.67 0.81 

PC-P Amistar 8 days 0.9 0.36 12 1.20 0.85 

PC-P Amistar 4 days 1.3 0.43 7 1.19 0.75 

PC-P Amistar+Folicur 8 days 0.9 0.44 12 1.26 0.90 

PC-P Amistar+Folicur 4 days 1.3 0.52 8 1.18 0.74 

LSD95 % septoria 

0.35 

Treatment 3 trials 1998 No. of appl. TFIa Flag leaf 2nd leaf Yield and yield inc. (t/ha) Net yield (t/ha) 

Untreated 0 0 33.2 80.6 7.40 - 

Folicur 1.0 GSZ 45 1 1 2.0 32.5 1.70 1.09 

PC-P Folicur 8 days 1 0.41 4.1 43.6 1.16 0.86 

PC-P Folicur 4 days 2 0.84 5.6 28.7 1.76 1.15 

Amistar 1.0 GSZ 45 1 1 2.8 42.3 2.00 1.14 

PC-P Amistar 8 days 1 0.41 5.5 55.7 1.79 1.39 

PC-P Amistar 4 days 1.3 0.42 9.2 44.7 1.89 1.46 

PC-P Amistar+Folicur 8 days 1 0.5 3.6 43.8 1.88 1.47 

PC-P Amistar+Folicur 4 days 1.3 0.5 10.9 35.8 1.91 1.45 

LSD95 6.8 10.9 5.3 

a TFI = Treatment frequency index. 

tebuconazole has given results 

similar to azoxystrobin applied alone 

at both 4 and 8 days. These results 

indicate that the curative effect of 

azoxystrobin against S. tritici under 

Danish conditions are similar or 

better than the triazoles 

propiconazole and tebuconazole 

used on the Danish market. 

Based on collected information, 

so far the test model for strobilurins 

recommends spraying after four 

days of precipitation starting at GSZ 

32. If spraying is carried out before 

GSZ 51, 10 days’ protection can be 

expected before days of precipitation 

have to be counted again. If applying 

after GSZ 51, 20 days’ effect can be 

expected from azoxystrobin, which 

in practice means that no further 

application is needed. The 

recommended rates of azoxystrobin 

in the model vary between 35 and 

45% of the normal rate. 

References 

Hansen, J.G., Secher, B.J., Jørgensen, 

L.N., and Welling, B. 1994. 

Threshold for control of Septoria 

spp. in winter wheat based on 

precipitation and growth stage. 


Jørgensen, L.N., and Nielsen, G.C. 

1998. Reduced dosages of 

strobilurins for disease 

management in winter wheat. 

Brighton Crop Protection 

Conference. Pest and Diseases 993- 

998. 

Jørgensen, L.N.; B.J.M. Secher, and H. 

Hossy. 1999. Decision support 

systems featuring Septoria 

Management. In: Septoria on 

Cereals: a Study of Pathosystems. 

J.A. Lucas, P. Bowyer, and H. M. 

Anderson (eds.). CABI Publishing, 


Secher, B.J., Jørgensen, L.N., Murali, 

N.S., and Boll, P.S. 1995. Field 

validation of a decision support 

system for control of pests and 

diseases in cereals in Denmark. 

Pesticide Science 45:195-199.

176

Concluding Remarks 

The Septoria/Stagonospora Blotch Diseases of Wheat: 

Past, Present, and Future 

Z. Eyal (paper presented by A.L. Scharen) 

Department of Plant Sciences and the Institute for Cereal Crops Improvement (ICCI), Tel Aviv University, Tel Aviv, 

Israel 

Abstract 

Septoria tritici and stagonospora nodorum blotch of wheat are regarded as major diseases because of their impact on crop 

management and wheat production. Both pathogens mainly affect the crop’s grain filling processes. Early research dealt 

mostly with genetic, cultural, and chemical control measures. Chemical control remains one of the major means of protecting 

wheat production, mostly through the use of new families of systemic fungicides. Emphasis has been given to epidemiological 

studies, in many cases associated with chemical control; however, in recent years epidemiological studies have expanded to 

include the effect of primary inoculum initiated from dispersal of ascospores of both pathogens. That shift in focus has 

introduced issues such as disease cycle, mating types, and their effect—together with pathogenicity—on each pathogen’s 

population structure. Recent findings attributed population structure to the pathogens’ sexual rather than asexual stage. The 

association between virulence spectrum and pathogenicity and the contribution of the sexual stage remains to be investigated. 

The impact of such studies on population structure may dictate adapting the proper breeding strategies. A population that is 

ever changing due to recombination and gene flow may influence the use of sources for specific resistance. As for the 

introduction of DNA technology into Septoria/Stagonospora: wheat so far has been able to identify population genetic 

trends in both pathogens, but they have yet to be linked to virulence patterns. The use of genetic transformation in both 

pathogens makes it possible to follow post-penetration processes by following reporter genes. This may reveal that 

synchronous events associated with the disease cycle, such as the building of fungal biomes and the initiation of picnidia 

formation, are all under the control of host-parasite interaction. Mutations in virulence genes facilitate studying their 

function and genome mapping. Concurrently resistance genes can be identified, studied, and mapped. This is an exciting era 

for Septoria tritici/Stagonospora nodorum x wheat interaction. 

The septoria/stagonospora 

blotch diseases of wheat are incited 

by Septoria tritici Roberge in 

Desmaz. (teleomorph: 

Mycosphaerella graminicola (Fückel) 

J. Schrot. in Cohn) and by 

Stagonospora nodorum (Berk) E. 

Castellani and E. G. Germano 

(teleomorph: Phaeosphaeria nodorum 

(E. Müller) Hedjaroude), 

respectively. The two pathogens 

cause major foliar diseases of 

wheat, inflicting considerable yield 

losses in many countries 

worldwide (King et al., 1983; Pnini- 

Cohen et al., 1998). It is of interest 

to note that these two pathogens 

are rare in many rice-wheat 

management systems in southeast 

Asia or others in Africa. 

The increased economic 

importance of these pathogens, 

especially of S. tritici, can be 

attributed to the cultivation of 

susceptible cultivars with a 

concomitant enhancement of 

resistance to other foliar pathogens 

(e.g., rusts, powdery mildew), 

predominance of wheat in crop 

management systems usually 

characterized by poor management 

of crop residues, increased nitrogen 

fertilization, high summer rainfall, 

earlier sowing, and resistance to 

MBC fungicides (Eyal, 1999). 

A surge in scientific research on 

these two pathogens occurred in 

the early 1980s, when a wide range 

of scientific data were published in 

177 

control-related disciplines (mostly 

chemical control and 

epidemiology) and less on 

biological and genetic aspects 

associated with the pathogens 

(Eyal, 1999). Breeding for disease 

resistance lagged due to scarcity of 

resistant germplasm and poor 

understanding of host-pathogen 

relationships and of how to 

manipulate resistance sources in 

breeding schemes. 

The shift in importance from 

stagonospora nodorum blotch to 

septoria tritici blotch (Pnini-Cohen 

et al., 1998) that occurred in certain 

European countries was explained 

by the biological differences in their 

disease cycles (shorter for S. tritici)

Concluding Remarks — Z. Eyal 

178 

and possibly due to differential 

sensitivity of the two pathogens to 

commercially used fungicides 

(Shaw, 1999). These explanations— 

which may reflect the situation in 

certain Western European 

countries—may not hold true in 

other wheat management systems. 

Still, the verification of the 

mechanism(s) affecting such shifts 

is extremely important, since it may 

dictate adoption of different control 

strategies. 

The sources of primary 

inoculum are rather variable: 

airborne ascospores, 

pycnidiospores from plant refuse, 

wild grasses, and, possibly, infested 

(infected?) seeds (Brokenshire, 

1975). Several wild grass species 

can serve as sources of inoculum to 

cultivated wheat, and some of them 

can contribute to speciation in 

pathogen populations. Artificial 

inoculation of wheat seedlings by 

isolates secured from grasses may 

not provide information on their 

contribution under natural 

infection. The possible contribution 

of infected seeds to the onset of 

disease was confirmed for S. 

nodorum, but is not well established 

for S. tritici. The current world 

trade of grain and, for that matter, 

of infested/infected grain provides 

ample opportunities for the 

dissemination of inoculum 

worldwide if such a distribution 

system is operative. 

Global virulence surveys 

conducted by Eyal et al. (1985) and 

Kema et al. (1996) have shown 

considerable diversity at the 

species level (Triticum spp.) and 

differential response on the selected 

“differential” set of wheat cultivars. 

McDonald et al. (1999) stated that 

“since it has been shown that M. 

graminicola can infect seed 

(Brokenshire,1975), we consider it 

likely that this is also the 

mechanism for long distance gene 

flow in M. graminicola.” The 

authors quoted King et al. (1983) 

that in the case of S. nodorum, the 

most likely mechanism for 

intercontinental dispersal is 

infected seed. It should be noted 

that Brokenshire (1975) stated that 

“infection of seedlings from 

infected untreated seed samples 

has proved unsuccessful with 

Triticum dicoccum.” The report on 

seed infection of S. tritici by 

Brokenshire (1975) was not further 

verified and thus introduced 

ambiguity in the understanding of 

the possible dissemination of this 

pathogen by seeds. The 

epidemiological implications of 

naturally-infected grasses for shortscale 

dissemination and seeds 

(especially for S. tritici) for longdistance 

transport, warrant 

detailed investigations. 

The supposition that 

population genetics of M. 

graminicola using single-locus 

probes to measure gene diversity 

for individual RFLP loci , 

population subdivision, and 

genetic similarity among 

populations (McDonald et al., 1999) 

can be superimposed on virulence 

patterns was not supported in 

studies on populations from 

California and Oregon (Mundt et 

al., 1999). Isolates of S. tritici from 

these states differed significantly in 

their pathogenicity (Ahmed et al., 

1996), yet they manifested 

similarity in allele frequencies as 

measured by RFLPs (Chen and 

McDonald, 1996). The finding that 

the genetic diversity measured 

among 122 isolates collected in an 

S. tritici nursery at Patzcuaro, 

Mexico, was among the lowest, 

does not imply that the pathogen 

has a narrow virulence pattern. The 

Patzcuaro S. tritici population was 

reported to possess virulence to 

some of the most resistant wheat 

cultivars (e.g., Bobwhite”S” and 

Kavkaz/K4500 L.6.A.4) (McDonald 

et al., 1999). 

Based on genetic population 

studies, McDonald et al. (1999) 

suggest that “if CIMMYT continues 

to use Patzcuaro as a field site to 

screen for resistance to M. 

graminicola and S. nodorum, it may 

want to consider introducing more 

diverse fungal populations from 

other parts of Mexico into this 

disease nursery.” It should be 

mentioned that some of the testing 

sites in the Patzcuaro area were 

artificially inoculated in the early 

1980s with a mixture of Mexican S. 

tritici isolates to ensure selection 

pressure on breeding materials 

(Santiago Fuentes, personal 

communication). The suggestion 

made by McDonald et al. (1999) 

implies that genetic diversity 

measured by random RFLP alleles 

can be used as an estimator of 

virulence pattern. It is therefore 

proposed that unless genetic 

diversity measured by random 

alleles is not highly correlated with 

diversity in virulence patterns, the 

former should not be used as an 

estimator of virulence in disease 

resistance breeding schemes. The 

issue of selecting relevant fungal 

isolates in screening for disease 

resistance will be further discussed. 

The quantitative estimation of 

host response percent (pycinidia 

and/or necrosis) for both S. tritici 

and S. nodorum and thereafter 

analyses of the interaction term of 

cultivar x isolates by statistical 

means (ANOVA) have been used to 

estimate genetic variation in these 

pathosystems (Eyal and Levy, 

1987). Such a statistical measure

equires a predetermined set of 

“differentiating cultivars,” which 

was not agreed to by Septoria tritici/ 

Stagonospora nodorum workers, 

suitable methodology (sampling, 

culturing of pathogen, inoculum 

age and dosage, incubation 

categories, disease assessment, 

etc.), and controlled environmental 

conditions to ensure reliability of 

results. The lack of a uniform 

methological approach and, in 

particular, of a common and 

agreeable set of differentials 

introduces difficulties in comparing 

and drawing conclusions on a 

wider basis. 

The suggested speciation of M. 

graminicola on durum (Triticum 

durum) and common wheat (T. 

aestivum) may require the inclusion 

of differentiating cultivars of both 

species when they are grown 

together or in studies where both 

are tested (Kema et al., 1996; 

Saadaoui, 1987). Isolates from one 

species may not be pathogenic to 

the other Triticum species; still, they 

may show a significant interaction 

term when a proper set of cultivars 

of a species is being inoculated 

with isolates from the same species. 

Cross infection of the two species 

was reported for isolates secured 

from either Triticum species (Eyal, 

1999; Kema et al., 1996). The 

specific pathogenicity towards T. 

durum may have bearing on the 

structure of S. tritici populations 

(Saadaoui, 1987). Alternate 

cropping of bread wheat cultivars 

in a durum wheat management 

system may express a lower than 

expected infection level on the 

former than under uninterrupted 

bread wheat management. 

Today it is generally accepted 

that the specificity in virulence is 

low in S. nodorum, but can be 

The Septoria/Stagonospora Blotch Diseases of Wheat: Past, Present, and Future 179 

detected in S. tritici populations 

provided proper differentiating 

germplasm is used (Eyal, 1995). 

The magnitude of specificity in the 

S. tritici - wheat pathosystem and 

its implications for breeding for 

disease resistance requires 

elaboration. Few dominant single 

genes conferring resistance were 

identified (e.g. Stb 1 - Bulgaria 88, 

Stb 2 - Veranopolis; Stb 4 - Tadinia) 

(Somasco et al., 1996). There are 

several reports that these resistant 

sources are not providing the 

claimed protection when moved 

across S. tritici populations with 

wide virulence patterns (Ballantyne 

and Thomson, 1995; Eyal, 1999). 

It is proposed that specificity 

and inheritance studies should be 

conducted with germplasm that is 

agronomically relevant to breeding, 

preferably exhibiting resistance to a 

wide virulence pattern (such as 

“Bobwhite“S”, IAS20-IASSUL, or 

other Frontana derivatives, 

Kavkaz/K4500 L.6.A.4, and other 

sources identified through 

multilocation testing) (Eyal et al., 

1987). Special attention should be 

given to resistant wheat accessions 

developed in wide-cross programs. 

Some of these accessions may be 

susceptible to other foliar diseases 

that may need attention when 

incorporating Septoria/Stagonospora 

resistance. Germplasm used in 

virulence studies is usually derived 

from disease nurseries naturally or 

artificially infected with the 

pathogen of interest. Only in a few 

cases has the virulence spectrum of 

these populations been categorized. 

It is therefore likely that 

identified resistant germplasm may 

have only limited use either as a 

breeding source or as 

“differentials.” Resistant 

germplasm that has withstood 

prolonged testing to variable 

pathogen populations can be 

considered a potential source for 

breeding for resistance. Special 

attention should be given to avoid 

selecting tall stature and late 

maturing germplasm that may 

introduce such non-genetic factors 

into germplasm evaluation, or 

germplasm with poor agronomic 

characteristics. 

Isolates possessing virulence to 

important resistance sources can 

become the “core virulence 

spectrum” for screening 

germplasm. There is no criterion as 

yet for selecting “relevant” isolates 

in artificially inoculated breeding 

trials. The criteria dictating the 

choice of isolates for genetic studies 

of virulence (Kema et al., 1999) may 

use considerations other than 

breeding. The choice by Kema et al. 

(1999) of S. tritici isolates such as 

IPO323 (avirulent on Veranopolis, 

Kavkaz, and Shafir) and IP094269, 

which is virulent on these cultivars, 

in studying the genetics of 

avirulence in this pathogen merits 

adoption by other Septoria tritici / 

Stagonospora nodorum investigators. 

The correlation between 

seedling and adult host response 

has been substantiated by several 

investigators (Eyal, 1999; Kema and 

van Silfhout, 1997). Screening for 

resistance at the seedling stage 

does not provide an integral view 

of the tested germplasm. Seedling 

tests can serve as a supplementary 

measure and are an excellent tool 

for detailed, controlled studies on a 

multitude of biological issues 

associated with host-pathogen 

interactions. The seedling test as a 

screening measure is hampered by 

not knowing whether the used 

isolates are relevant to the 

virulence spectrum of the


180 

populations to which the test 

germplasm will be subjected under 


Cross testing of germplasm to 

both seedling and field conditions 

is usually performed with 

predetermined isolate(s) that can 

serve as a “basic virulence set” 

(Eyal, 1999). Its composition may 

change by introducing isolates 

found to be virulent on specific 

resistant germplasm, or omitting 

others. The set should include 

isolate(s) whose virulence on 

specific accessions has been 

repeatedly confirmed. The 

multilocation Septoria Monitoring 

Nursery initiated by CIMMYT can 

provide information as to the 

magnitude of protection of some of 

the identified sources and 

contribute information on 

worldwide virulence patterns. 

The contribution of the sexual 

stage to the virulence spectrum 

needs special attention. Evidence 

from studies on population 

genetics emphasizes the major 

influence of the sexual stage on the 

genetic diversity of the population 

(Chen and McDonald, 1986; Eyal 

and Levy, 1987; Eyal et al., 1985; 

Jlibene et al., 1994; McDonald et al., 

1999; Zhan et al., 1998). McDonald 

et al. (1999) stated that asexual 

reproduction may have an 

important impact over a limited 

area (e.g. few square meters), 

whereas sexual reproduction has 

much greater consequences for 

population genetics. 

The limited scope of clonality in 

M. graminicola and P. nodorum 

populations strengthens the need 

for comparative studies on 

virulence. The limitation of such 

studies resides with selected 

“wheat differentials.” This 

difficulty can be partly overcome 

by tracing specific virulences 

within the pathogen population on 

certain resistance accessions (e.g. 

Kavkaz/K4500 L.6.A.4). Low 

frequency of virulence to Kavkaz/ 

K4500 L.6.A.4 was reported for the 

first time in Israel (Ezrati et al., 

1998), interestingly, in Nahal Oz, 

where McDonald et al. (1999) 

detected the greatest genetic 

diversity using random RFLP 

alleles. Low frequency of virulence 

on Kavkaz/K4500 L.6.A.4 was 

reported in the global virulence 

surveys conducted by Eyal et al. 

(1995) and Kema et al. (1996). This 

germplasm was not used in 

international and Israeli breeding 

programs in the past and therefore 

no selective advantage can explain 

its detection. It is expected that the 

presence of virulence on this 

accession at Nahal Oz can be 

accounted for by the fact that the 

sexual stage is operative there, as 

implied by McDonald et al. (1999). 

Chen and McDonald (1996) 

hypothesized that M. graminicola 

isolates can be produced via 

genetic recombination with the 

same combination of virulence 

genes that may not have the same 

recent ancestors, thus contributing 

to multiple clonal lineages in the 

population. The distribution of this 

virulence in space (locations) and 

time (years) is under study. 

The expression of virulence on 

certain wheat germplasm was 

reported to be altered upon 

inoculation with mixtures of S. 

tritici isolates (Ezrati et al., 1998; 

Zelikovitch and Eyal, 1991). When 

a resistant cultivar (e.g., Seri 82) is 

inoculated with a mixture of 

avirulent (ISR398) and virulent 

(ISR8036) isolates, the level of 

pycnidia produced on the seedlings 

and adult plants in the field 

resembles that produced by the 

avirulent isolate inoculated singly 

(Ezrati et al., 1998). The virulent 

isolate ISR8036 predominated in 

the population of pycnidia on both 

seedlings and adult plants of the 

susceptible cultivar Shafir 

inoculated with a 1:1 mixture of the 

two isolates. It was suggested that 

isolate ISR8036, which induced the 

same level of pycnidia on Shafir as 

ISR398, was more aggressive than 

the latter, giving it a competitive 

advantage in the population. 

The suppression phenomenon 

was also operative when an array 

of resistant cultivars (e.g. 

Bobwhite”S”, IAS 20-IASSUL, and 

Kavkaz/K4500 L.6.A.4) were 

inoculated with appropriate 

mixtures of avirulent and virulent 

isolates (Ezrati et al., 1998). These 

findings are indicative of the 

commonality of the phenomenon 

where resistance induced by an 

avirulent S. tritici isolate can 

provide tissue protection against 

the virulent isolate. The level of 

protection, the conditions under 

which it is expressed, and the 

mechanism(s) associated with the 

induction needs further 

investigation. 

It is possible that under field 

conditions, induced resistance may 

be operative under low to 

moderate S. tritici epidemics, 

provided a certain level of genetic 

resistance is present in the infected 

wheat cultivar. The reported 

differences in aggressiveness 

among isolates (Ahmed et al., 1996; 

Ezrati et al., 1998; Mundt et al., 

1999) suggest that the structure of 

an asexual population 

progressively developed on wheat 

plants can be strongly affected by 

both virulence and aggressiveness. 

If the sexual stage is the sole

provider of primary inoculum from 

distant sources (Shaw and Royle, 

1989) or from within the crop 

(Gilchrist and Velazquez, 1994), the 

structure of the population will 

probably change annually. 

The vertical progression within 

the crop of pseudothecia from 

lower to upper leaves (Gilchrist 

and Velazquez, 1994) may give an 

advantage to “local” populations, 

though it does not exclude the 

possibility that the primary 

inoculum may come from a 

distance and then perpetuate itself 

within the crop. Hunter et al. (1999) 

stressed that the continuous 

development of a functional sexual 

stage suggests that there is genetic 

exchange throughout the growing 

season that can respond over time 

to selection pressure exerted by 

resistant germplasm. The role of 

the asexual stage in epidemics and 

in formulating the virulence 

structure of the population under 

such conditions is not clear. 

The genetic variation for 


wheat-S. tritici pathosystem, in 

addition to having implications for 

breeding for disease resistance, 

provides an opportunity to expand 

our knowledge on the biology and 

genetics of the interaction. The 

recognized specificity in the 

relationship linked with the 

implementation of new DNA 

technology allows for a more 

thorough understanding of the 

pathogen, the host, and the 

interaction. This makes it possible 

to adopt methodologies from other 

host-pathogen systems and apply 

them to the economically important 

wheat-S. tritici/S. nodorum 

pathosystems. 

The Septoria/Stagonospora Blotch Diseases of Wheat: Past, Present, and Future 181 

Issues associated with the 

ability to infect wheat and 

processes related to the infectioncycle 

(biochemical, involvement of 

toxins, tissue necrosis, induction of 

pycnidia formation, and 

suppression of production), 

virulence (genotypic diversity and 

population structure), pathogen 

migration, the potential of genetic 

recombination on pathogen 

structure and then on disease 

management, and genetic host 

resistance (specific, non-specific) 

are currently being investigated 

with the aid of molecular tools 

(Caten, 1999; Eyal, 1999; Kema et 

al., 1999; Baker et al., 1997; Eyal et 

al., 1985). Genetic diversity and 

population structure are being 

revealed with the aid of RFLP, 

RAPD probes, and DNA 

fingerprinting (McDonald et al., 

1999). 

The issue of mating types and 

possible sequencing of genes 

associated with these types, and 

mapping of the M. graminicola and 

P. nodorum genomes are being 

investigated by Caten (1999) and 

Kema et al. (1999). Genetically 

transformed S. tritici isolates and 

tagged mutants with altered 

virulence are being investigated by 

Pnini-Cohen et al. (1998). The use 

of reporter gene(s) (e.g. GUS, GFP) 

in genetically transformed S. tritici 

and S. nodorum isolates and 

immunological assays can greatly 

contribute to the understanding of 

in planta qualitative and 

quantitative post-inoculation 

events. The interrelations between 

isolates in a population and the 

effect of induced resistance and 

competition on a pathogen 

population are elucidated with the 

aid of isolate-specific PCR primers 

(Ezrati et al., 1998). The elucidation 

of loci associated with host 

resistance employ QTL analyses, 

and genomic analysis may some 

day contribute to the identification 

of sequences linked to resistance. 

It is likely that genes associated 

with resistance to S. tritici and S. 

nodorum share products with 

structural similarities to other plant 

defense systems (Baker et al., 1997). 

The structural features shared by 

several R (resistance) gene products 

are a leucine-rich repeat (LRR) 

motif or a serine-threonine kinase 

domain. Some of these genes 

encode cytoplasmic receptor-like 

proteins that contain an LRR 

domain and a nucleotide binding 

site (NBS). It is therefore possible 

that these gene products are 

operative in wheat and can be 

tagged. The identification of 

specific interactions between 

avirulence genes in S. tritici 

(AVRmg) and genes for resistance 

in the wheat plant may pave the 

way for the “genetic dissection of R 

gene-mediated induction of 

hypersensitive (?)” (or suppression 

of symptoms in isolate mixtures ?) 

host defense. This insight can be 

used to genetically engineer wheat 

cultivars resistant to a broad 

spectrum of pathogens. It will 

require a better understanding of 

avirulence, specific resistance, and 

host-pathogen interactions and 

their products in those 

pathosystems, prior to the 

formulation of a protection 

strategy. As a consequence, the 

economic and ecological (chemical 

protection) impact on wheat 

production will be reduced.


182 

References 








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88:1330-1337.

List of Participants 

Mr. Shaukat Ali 

Graduate Student 

North Dakota State University 

320 Walster Hall 

Fargo ND 58105 

Phone: (701) 231-7855 

Email: sali@prairie.NoDak.edu 

Ms. Lia Arraiano 

Phd Student 

John Innes Centre 

Colney Lane 

Norwich Research Park 

Norwich Norfolk NR4 7UH 

United Kingdom 

Phone: +44 (1603) 452571 ext. 2618 

Fax: +44 (1603) 502241 

Email: lia.arraiano-e-castroalves@bbsrc.ac.uk 

Professor Edward Arseniuk 

Plant Breeding and Acclimatization 

Institute 

Radzikow 

05-870 Blonie 

Poland 

Phone: (48-22) 725 4536; (48-22) 349 470 

[home] 

Fax: (48-22) 725 4714 

Email: e.arseniuk@ihar.edu.pl 

Dr. Gary C. Bergstrom 

Professor 

Department of Plant Pathology 

Cornell University 

334 Plant Science Building 

Ithaca NY 14853-4203 

Phone: +1(607) 255-7849 

Fax: +1(607) 255-4471 

Email: gcb3@cornell.edu 

Dr. Penny Brading 

Post-Doctoral Scientist 

Cereals Research Dept. 


Colney Lane 

Norwich Research Park 

Norwich Norfolk NR4 7UH 


Phone: +44 (1603) 452571 ext. 2618 

Fax: +44 (1603) 502241 

Email: penelope.brading@bbsrc.ac.uk 

Dr. James K.M. Brown 

Pathologist & Geneticist 

Cereals Research Department 


Colney Lane 

Norwich Norfolk NR4 7UK 


Phone: +44 (1603) 452571 

Fax: +44 (1603) 456844 

Email: james.brown@bbsrc.ac.uk 

Dr. Cristina C. A. Cordo 

Facultad de Agronomia 

Catedra de Fitopatologia La Plata 

Universidad Nacional de la Plata 

Calle 60 y 119; c.c. 31 

La Plata 1900 

Argentina 

Phone: +54 0221 4 83 18 31 

Fax: +54 0221 4 25 23 46 

Email: criscordo@infovia.com.ar 

Ms. Christina Cowger 

Graduate Research Assistant 

Botany Dept. 

Oregon State University 

2082 Cordley Hall 

Corvallis OR 97331-2902 

Phone: +1 (541) 737-4408 

Fax: +1 (541) 737-3573 

Email: cowgerc@bcc.orst.edu 

Dr. Barry M. Cunfer 


Dept. Plant Pathology 

University of Georgia 

1109 Experiment St. 

Griffin GA 30223-1797 

United States 

Phone: +1(770) 412 4012 

Fax: +1(770) 228 7305 

Email: bcunfer@gaes.griffin.peachnet.edu 

Dr. Pawel Czembor 

Research Assistant 

Plant Breeding & Acclimatization Inst. 

Radzikow 

05-870 Blonie 

Poland 

Phone: +48 (22) 7253611 

Fax: +48 (22) 7254714 

Email: p.czembor@ihar.edu.pl 

Prof. Amos Dinoor 

Professor of Plant Pathology 

Faculty of Agriculture, Food and 

Environmental Quality Sciences 

The Hebrew University of Jerusalem 

P.O. Box 12 

Rehovot 76100 

Israel 

Phone: + 972 (8) 9481358 

Fax: +972 (8) 9466794 

Email: dinoor@agri.huji.ac.il 

Dr. Annika Djurle 

Plant Pathology 1 

Department of Ecology and Crop 

Production Sciences 

SLU 

P.O. Box 7043 

SE-75007 UPPSALA 

Sweden 

Phone: +46 (18) 67 16 02 

Fax: +46 (18) 67 28 90 

Email: annikad@pinus.slu.se 

Mr. Keith E. Duncan 

Biologist 

DuPont Agricultural Biotechnology 

E. I. DuPont de Nemours Co., Inc. 

E402 Experimental Station 

Wilmington , DE 19880-0402 

United States 

Phone: 302 695 4298; 302 695 

3891(laboratory) 

Fax: 302 695 4509 

Email: keith.e.duncan@usa.dupont.com 

Ms. Clare Marie Ellerbrook 

Research Scientist 


Colney Lane 

Norwich UK NR4 7UH 


Phone: +44 (1603) 452571 

Fax: +44 (1603) 456844 

Email: clare.ellerbrook@bbsrc.ac.uk 

Ms. Smadar Ezrati 

Ph. D. Student 

Department of Botany 

Tel-Aviv University 

Tel Aviv 69978 

Israel 

Phone: +972 (3) 640 9766 

Fax: +972 (3) 640 9380 

Email: ezrati@post.tau.ac.il 

Dr. Lucy Gilchrist 

Pathologist 

Wheat Program 

CIMMYT 

Lisboa 27, Col. Juárez 

Delegación Cuauhtemoc 

Apdo. Postal 6-641 

06600 Mexico D.F. 

Mexico 

Phone: +52 5804 2004 

Fax: +52 5804 7558/9 

Email: l.gilchrist@cgiar.org 

183 

Ing. Rebeca Margarita Gonzalez Iñiguez 

Investigador de Trigo y Triticale 

Instituto Nacional de Investigaciones 

Forestales y Agropecuarias 

Silvestre Guerrero 449, Colonia 5 de 

Diciembre 

58280 Morelia Mich. 

Mexico 

Phone: (43) 15 9489 y 15 9021 

Fax: (43) 151091 

Dr. Stephen B. Goodwin 

Plant Pathologist 

Department of Botany and Plant Pathology 

USDA/ARS Purdue University 

1155 Lily Hall 

West Lafayette IN 47907-1155 

United States 

Phone: +1(765) 494-4635 

Fax: +1(765) 494-0363 

Email: goodwin@btny.purdue.edu

184 

Dr. Patrice Halama 


Institut Superieur d’Agriculture 

41 rue du port 

59046 Lille cedex 

France 

Phone: +33 (03) 28 38 48 48 

Fax: +33 (03) 28 38 48 47 

Email: p.halama@isa.fupl.asso.fr 

Dr. Sonia Hamza 

Associate Professor 

Laboratoire de Genetique 

INAT 

43 Av. Chrales Nicolle 

1082 El Mahrajene Tunis 

Tunisia 

Phone: +216 (1) 840 270 

Fax: +216 (1) 799 391 

Email: hamza.sonia@inat.agrinet.tn 

Dr. Karen K. Hanson 

Cereal Pathology Specialist 

Plant Pathology 

Zeneca Agrochemicals 

Jealott’s Hill Research Station 

RG42 6ET Bracknell Berishire 

Ukraine 

Phone: +44 (01344) 414488 

Fax: +44 (01344) 414502 

Email: 

Karen.Hanson@AGUK.ZECECA.com 

Prof. Mouncef Harrabi 

Professor and Director General 

Crop Science Department 

INAT 

43 Ave. Charles Nicolle 

1082 Tunis 

Tunisia 

Phone: +216 (1) 840270 

Fax: +216 (1) 799391 

Email: harrabi.moncef@inat.agrinet.tn 

Dr. Pavel Horcicka 

Head 

Wheat Breeding Department 

SELGEN 

Plant Breeding St. Stupice 

25084 Sibrina 

Czech Republic 

Phone: +42 (2) 81972462 

Fax: +42 (2) 81970465 

Email: horcicka@zero.cz 

Dr. Jerry W. Johnson 

Wheat Breeder 

Crop and Soil Sciences Division 

University of Georgia 

Georgia Station 

Griffin GA 30223 

United States 

Phone: +1 (770) 228 7321 

Fax: +1 (770) 229 3215 

Email: jjohnso@gaes.griffin.peachnet.edu 

Ms. Lise Nistrup Jorgensen 

Senior Scientist 

Research Centre Flakkebjerg 

Danish Institute of Agricultural Sciences 

Slagelse 

DK-4200 Flakkebjerg 

Denmark 

Phone: +45 (58) 113300 

Fax: +45 (58) 113301 

Email: LiseN.Jorgensen@agrsci.dk 

Dr. Ute Kastirr 

Scientific Collatorator 

Federal Centre for Breeding Research on 

Cultivated Plants 

Institute for Resistance Research and 

Pathogendiagnostics 

Theodor-Roemer-Weg 4 

D-06449 Aschersleben 

Germany 

Phone: +49 (0) 3473 879197 

Fax: +49 (0) 3473 879200 

Email: u.kastirr@bromo.qlb.bafz.de 

Dr. Gert H.J. Kema 

Senior Scientist 

IPO-DLO 

P.O. Box 9060 

6700 GW Wageningen 

Netherlands 

Phone: +31 317 476149 

Fax: +31 317 410113 

Email: G.H.J.Kema@IPO.DLO.NL 

Mr. Awgechew Kidane 

Quarantine Pathologist 

Ethiopian Agricultural Research 

Organization, 

Holetta ARC 

P.O. Box 2003 

Addis Ababa 

Ethiopia 

Phone: +251 

Fax: +251 

Email: CIMMYT-Ethiopia@cgiar.org 

Dr. Theodore J. Kisha 

Research Agronomist 

Agronomy Department 

Purdue University 

1150 Lilly Hall 

West Lafayette IN 47907 

United States 

Phone: +1 (765) 496 1917 

Fax: +1 (765) 496 2926 

Email: tkisha@purdue.edu 

Dr. Holger Klink 

Plant Pathologist at the University of Kiel 

Inst. for Phytopathlogie 

University of Kiel 

Hermann-Rodewald-Str.9 

D-24118 KIEL 

Germany 

Phone: +49 431 880 2994 

Fax: +49 461 880 1583 

Email: 

Barbara.Muth@ageurope.zeneca.com; 

Evelyn.Badeck@ageurope.zeneca.com 

Notes: HK@phytomet.uni.kiel.de 

Dr. Manfred Konradt 

Technical Manager 

ZENECA Agrochemicals 

Cmil-von-Behringstr.2 

D-60439 Frankfurt/Main 

Germany 

Phone: +49 069 58 01 414 

Fax: +49 069 5801 672 

Email: Barbara.Muth@ageurope.zeneca.com; 


Notes: 

Manfred.Konradt@geurope.zeneca.com 

Dr. Joseph M. Krupinsky 

Research Plant Pathologist 

Northern Great Plains Research Lab 

USDA-ARS 

P.O. Box 459 

Mandan ND 58554-0459 

United States 

Phone: +1(701) 667-3011 

Fax: +1(701) 667-3054 

Email: Dvorakl@mandan.ars.usda.gov; 

krupinsj@mandan.ars.usda.gov 

Dr. Steven Leath 

Research Plant Pathologist 


USDA-ARS 

Box 7616, NCSU 

Raleigh NC 27695 

United States 

Phone: 919-515 6819 

Fax: 919-515 7716 

Email: Judith_Sulentic@ncsu.edu 

Notes: steven_leath@ncsu.edu 

Dr. Robert Loughman 

Senior Plant Pathologist 

Plant Protection Branch 

Agriculture Western Australia 

Plant Research and Development Services 

Locked Bag No. 4 

Bentley Delivery Centre W.A. 6983 

Australia 

Phone: +61 (618) 93683691 

Fax: +61 (618) 93672625 

Email: jtoms@agric.wa.gov.au; 

rloughman@agric.wa.gov.au 

Prof. Dr. Bruce McDonald 

Group Leader 

Institute of Plant Sciences/Phytopathology 

Federal Insitute of Technology 

ETH-Zentrum, LFW 

Universitaetstr 2/LFW-B16 

CH-8092 Zuerich 

Switzerland 

Phone: +41 (1) 632 3847 

Fax: +41 (1) 632 15 72 

Email: Bruce.McDonald@ipw.agrl.ethz.ch

Dr. Ehud Meidan 

Wheat Breeder 

HAZERA Quality Seeds 

Mivhor 

M.P. Lachish-Dargm 75354 

Israel 

Phone: +972 (7) 6878155 

Fax: +972 (7) 6814057 

Email: Udi_Meidan@hazera.com 

Dr. Eugene Milus 

Associated Professor 


University of Arkansas 

217 Plant Science Bldg. 

Fayetteville AR 72701 

United States 

Phone: +1(501) 575-2676 

Fax: +1(501) 575-7601 

Email: gmilus@comp.uark.edu 

Miss Mihaela V. Mincu 

Junior Research worker 

Research Institute for Cereals and 

Industrial Crops 

FUNDULEA 

CP 22-171 

Bucuresti 

Romania 

Phone: +40 3154040 

Fax: +40 3110722 

Email: fundulea@cons.incerc.ro 

Mrs. Rose John Mongi 

Wheat Breeder 

MARTI-Uyole 


P.O. Box 400 

Mbeya 

Tanzania 

Phone: + 255 (1) 614-645 

Fax: +255 

Email: c/o CIMMYT-Ethiopia@cgiar.org 

Dr. Chris C. Mundt 


Dept. of Botany and Plant Pathology 

Oregon State University 

2082 Cordley Hall 

Corvallis OR 97331-2902 

United States 

Phone: +1 541 737 5256 

Fax: +1 541 737 3573 

Email: mundtc@bcc.orst.edu 

Dr. Noel E.A. Murphy 

Research Fellow 

Murdoch University 

DSE South St 

Murdoch 6150 

Australia 

Phone: +61 (8) 9360 6097 

Fax: +61 (8) 9360 6303 

Email: nmurphy@central.murdoch.edu.au 

Dr. Lloyd R. Nelson 

Wheat Breeder and Professor 

Texas A&M Research and Extension Center 

P.O. Box 200 

Overton TX 75684-0200 

United States 

Phone: +1(903) 834 6191 

Fax: +1(903)-834 7140 

Email: Ir-nelson@tamu.edu 

Ms. Guita Cordsen Nielsen 

Senior Adviser 

The National Department of Plant 

Production 

The Danish Agricultural Advisory Centre 

Udkaersvej 15 

DK-8200 Skejby Aarhus 

Denmark 

Phone: +45 (87) 405439; +45 (87) 405000; 

+45 20282695 mobile 

Fax: +45 (87) 405010 

Email: gcn@lr.dk 

Notes: Damgaard, Vroldvej 168; DK-8660 

Skaderborg; Phone: +45 (86) 57 98 00 

Dr. Thomas S. Payne 

Wheat Breeder/Pathologist 

Wheat Program 

CIMMYT-East Africa 

P.O. Box 5689 

Addis Ababa 

Ethiopia 

Phone: +251 (1) 615-127 

Fax: +251 (1) 614-645 

Email: t.payne@cgiar.org 

Telex: 21207 ILCA ET 

Dr. Sanjaya Rajaram 

Director 

Wheat Program 






Mexico 

Phone: +52 5804 2004 

Fax: +52 5804 7558/9 

Email: s.rajaram@cgiar.org 

Dr. Albert L. Scharen 

Professor Emeritus 

Department of Plant Sciences 

Montana State University 

Bozeman MT 59717 

United States 

Phone: +1(406) 994-5162 

Fax: +1 (406) 994-1848 

Email: uplas@montana.campuscwix.net 

Mrs. Silvia Schuster 

Research Assitant 

Plant Sciences Department 

Tel-Aviv University 

Tel Aviv 

Israel 

Phone: +972 (3) 640 9766 

Fax: +972 (3) 640 9380 

Email: schus@post.tau.ac.il 

Dr. Gregory Shaner 


Botany and Plant Pathology 

Purdue University 

1155 Lilly Hall of Life Sciences 

West Lafayette IN 47907-1155 

United States 

Phone: +1(765) 494 4651 

Fax: +1 (765) 494 0363 

Email: shaner@btny.purdue.edu 

Dr. Michael W. Shaw 

Reader, Sch. of Plant Sciences 

The University of Reading 

Whiteknights 

Reading, RG6 6AS UK 


Phone: +44 118 931 8091 

Fax: +44 118 931 6577 

Email: M.W.Shaw@reading.ac.uk 

Dr. Ravi P. Singh 

Rust Genetist 

Wheat Program 






Mexico 

Phone: +52 5804 2004 

Fax: +52 5804 7558/9 

Email: r.singh@cgiar.org 

Dr. Bent Skovmand 

Head, Wheat Genetic Research 

Wheat Program 

International Maize and Wheat 

Improvement Center 




06600 México D.F. 

Mexico 

Phone: +52 5804 2004 ext. 2226 

Fax: +52 5804 7558/9 

Email: b.skovmand@cgiar.org 

Dr. Brian J. Steffenson 

Associate Professor 



P.O. Box 5012 

Fargo ND 58105-5012 

United States 

Phone: +1(701)231-7078 

Fax: +1(701)231-7851 

Email: bsteffen@badlands.nodak.edu 

Dr. Enrique Torres 

Calle 72 A No. 16-15 (301) 

Bogota 

Colombia 

Phone: +57-1-2359861, dentro Colombia: 

91-2359861 

Fax: +57-1-2359861 

Email: etorres@hotmail.com 

185

186 

Dr. Hala Toubia-Rahme 

Research Associate 

Dept. of Plant Pathology 


P.O. Box 5012 

Fargo ND 58105-5012 

United States 

Phone: +1 (701) 231 7018 

Fax: +1 (701) 231 7851 

Email: 

Hala_Toubia_rahme@ndsu.nodak.edu 

Dr. Ludvik Tvaruzek 

Research Worker 

Agricultural Research Insitute Kromeriz 

Havlickova 2787 

767 01 Kromeriz 

Czech Republic 

Phone: +42 634317138 

Fax: +42 63422725 

Email: tvaruzek@vukrom.cz 

Dr. Peter Ueng 

Scientist 

Plant Molecular Biology Laboratory 

USDA-ARS 

MPPL, BARC-West, Bldg. 011A 

Beltsville MD 20705 

United States 

Phone: +1 (301) 504 6308 

Fax: +1 (301) 504 5449 

Email: pueng@asrr.arsusda.gov 

Dr. Maarten van Ginkel 

Head, Bread Wheat Program 

Wheat Program 





06600 México D.F. 

Mexico 

Phone: +52 5804 2004 

Fax: +52 5804 7558/9 

Email: m.van-ginkel@cgiar.org; http:// 

www.cimmyt.mx 

Ms. Carmen Velazquez 

Wheat Program 


Lisboa 27, Col. Juarez 

Delegacion Cuauhtemoc 


Mexico D.F. 

Mexico 

Phone: +52 5804 2004 

Fax: +52 5804 7558/9 

Email: c.velazquez@cgiar.org 

Prof. Dr. Joseph Alexander Verreet 


Inst. for Phytopathlogie 

University of Kiel 

Hermann-Rodewald-Str.9 

D-24118 KIEL 

Germany 

Phone: +49 431 880 2996 

Fax: +49 461 880 1583 

Email: 

Barbara.Muth@ageurope.zeneca.com; 


Notes: JAV@phytomet.uni.kiel.de 

Mr. Robin Wilson 

Senior Wheat Breeder 

Crop Industries 

Agriculture Western Australia 

Locked Bag No. 4 

Bentley Delivery Centre W.A. 6983 

Australia 

Phone: +61 (618) 9368 3691 

Fax: +61 (618) 9367 2625 

Email: rwilson@agric.wa.gov.au 

Dr. Bruno Zwatz 

Head of the Institute 

Federal Office and Research Centre for 

Agriculture 

Institute of Phytomedicine 

Spargelfeldstrasse 191 

Vienna Wien A-1226 

Austria 

Phone: +43(1)73216-5500 

Fax: +43(1)73216-5194 

Email: bzwatz@bfl.gv.at; 

margarethe.zaufal@relay.bfl.at

ISBN: 970-648-035-8 

International Maize and Wheat Improvement Center 

Centro Internacional de Mejoramiento de Maíz y Trigo 

Lisboa 27, Apartado postal 6-641 México, D.F., México

Septoria and Stagonospora Diseases of Cereals - CIMMYT ...

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