Fomes lignosus (Klotzsch) Bres. A DECAY AND ROT FUNGUS LUBNA JAHAN FORESTRY AND WOOD TECHNOLOGY DISCIPLINE LIFE SCIENCE SCHOOL KHULNA UNIVERSITY KHULNA-9208 2006 Fomes lignosus (Klotzsch) Bres. A DECAY AND ROT FUNGUS COURSE TITLE: PROJECT THESIS COURSE # FWT-5112 This Project Thesis has been prepared in partial fulfillment of the requirement for MS- degree in Forestry from Forestry and Wood Technology Discipline, Khulna University, Khulna. SUPERVISOR SUBMITTED BY Dr. Mohammad Abdur Rahman Professor Forestry and Wood Technology Discipline Khulna University Khulna-9208 Bangladesh. Lubna Jahan Roll # MS-030504 Forestry and Wood Technology Discipline Khulna University Khulna-9208 Bangladesh. TABLE OF CONTENTS Page No. TABLE OF CONTENTS i LIST OF FIGURES iii ABSTRACT iv DEDICATION v ACKNOWLEDGEMENT vi CHAPTER ONE: INTRODUCTION 1-4 1.1 Introduction 1 1.2 Objectives of the study 4 1.3 Methodology 4 CHAPTER TWO: GENERAL INFORMATION OF Fomes lignosus 5-10 2.1 Accepted scientific name 2.2 Common name 5 5 2.3 Synonyms 2.4 Classification of Fomes lignosus (KLOTZSCH) BRES 5 8 2.5 Epidemiology 2.6 Dispersal 2.7 Distribution 2.8 Biology, Ecology and Morphology 8 8 8 8 CHAPTER THREE: PATHOGENIC ROLE of Fomes lignosus 11-24 3.1 Host Plant for Fomes lignosus 3.2 Hevea brasiliensis (RUBBER) 3.2.1 Ultrastructural Aspects of Rubber Tree Root Rot Diseases 3.2.1.1 Colonization and degradation of non lignified tissues 3.2.1.2 Colonization and degradation of lignified tissues 3.3 Tectona grandis (TEAK) 3.4 Cola nitida 3.5 Manihot esculenta (CASSAVA) 3.6 Acacia mangium (MANGIUM) 3.7 Triplochiton Scleroxylon 3.8 Decay Of Rhizome Root And Basal Culm 11 11 12 12 16 18 19 19 19 20 20 3.9 Strip Plantations 22 i 3.10 Management and Control 22 CHAPTER FOUR: CONCLUSION 25 3.1 Conclusion 25 26-32 REFERENCES ii LIST OF FIGURES Page No. Figure-1.1 Rigidoporus microporus (Fr.) Overeem (Baroni, 1998). 2 Figure-2.1 Rigidoporus microporus - white root disease - showing the fruiting body (Anon, 1999). Intercellular colonization of cortical tissues; adjacent cells are separated by a fungal ramification differentiated during the fungal growth (arrow); (x 5000) (Nicole et al., 1987). The intracellular position of hyphae in cortical tissues results in wall-perforation; the digestion of the cellulosic framework is first characterized by granular zone near the fungal filament (arrow); (X 8000) (Nicole et al., 1987). Cellulosic wall penetration; the enzymatic degradation of the wall (double arrows) is completed by mechanical processes (arrows); (X 15000) (Nicole et al., 1987). Aveolar aspects (arrows) of a cellulosic wall of a phloem ce17 degraded by R. lignosus, the fibrillar structure of the wall is profoundly pertubated (x 8000) (Nicole et al., 1987). Middle lamella and cellulose fibers of a sieve tube cell wall in a healthy phloem; (X 20000) (Nicole et al., 1987). The degradation of the middle lamella causes the increase of its osmiophilic properties (arrows) before its perforation; (x ~0000) (Nicole et al., 1987). : Perforation of the middle lamella leads to meatus formation; the degradation then extends to the cellulosic wall (arrows); (X 10000) (Nicole et al., 1987). : Digestion of a part of a suberized cell wall in a young phellem cell (arrows); the degradation of these walls generally occurs when hyphae move in the wall or perforate it; (x 12500) (Nicole et al., 1987). Differentiation of microhyphae by R. Lignosus. Note the accumulation of electron-dense particles near the hypha (arrow); (X 8000) (Nicole et al., 1987). During xylem middle lamella degradation we note first the disorganization of the native structure (1) causing the apparition of a granular matrix (2) and, secondly, the perforation of this matrix and meatus formation (3); (X 20000) (Nicole et al., 1987). After meatus formation resulting in an alteration of middle lamella, the digestive action extends to the primary wall (arrows); (x 20000) (Nicole et al., 1987). Organization of walls of a xylem vessel of a healthy young root; (x 12500) (Nicole et al., 1987). Wood degradation by R. lignosus: a cross section through a vessel wall shows the dissolution of the S1/S2 border layer of the secondary wall characterized by small cavities (arrows) (3.13); the alteration then extends to the S2 layer (arrows) (3.14). (Fig. 3.13: x 25000; Fig. 3.14: x 15000) (Nicole et al., 1987). Decay of basal culm in B. bambos caused by Polyporus sp (Anon, 1995). 9 Figure-3.1 Figure-3.2 Figure-3.3 Figure-3.4 Figure-3.5 Figure-3.6 Figure-3.7 Figure-3.8 Figure-3.9 Figure-3.10 Figure-3.11 Figure-3.12 Figure-3.13 & 3.14 Figure-3.15 iii 13 13 13 14 14 15 15 15 16 17 17 17 18 21 ABSTRACT The fungal genus Fomes is a group of wood-decaying fungi that are found throughout the world on all types of wood — gymnosperms, hard and softwood dicots, and palms. Fomes lignosus (Klotzsch) Bres is a serious root rot pathogen of worldwide distribution. Following girdling experiments in the Congo showing the reduction of infection potential, girdling or poisoning before felling is suggested to ensure that the roots of trees so killed are colonized by saprophytic fungi antagonistic to the major root-rot pathogens. F. lignosus is unable to synthesize the whole thiamine molecule; it can synthesize only one part, thiazole, and the other part, pyrimidine, must be supplied from other sources, e.g. wood, leaves etc. In 1990, a serious root rot disease was observed in different strip plantations of Court ChandpurSubdalpur railroad, Jessore-Benapole highway and Jessore-Satkhira road of greater Jessore district, Bangladesh. These plantations were covered with trees such as Cassia siamea, Acacia auriculiformis, A. nilotica, Albizia procera, Leucaena leucocephala and Dalbergia sissoo. The affected trees died in patches showing wilting symptoms. The leaves of affected trees became brown, dried up and remained attached to the dead branches. The fungus responsible for the disease was isolated and identified as Fomes lignosus [Rigidoporus lignosus]. It is preferable to locate infected trees by their leaf symptoms rather than by root inspection, to avoid host injury. Initial penetration depends on mechanical pressure, but later extra cellular enzymes are involved. The ray cell walls are penetrated mechanically, the xylem through pits. Root disease of teak is widely distributed in Nigeria, where it is present in c. 70% of teak plantations. Disease incidence is more serious in shallow lateritic soils and sites with impeded drainage. The disease may be controlled by using 2% tillex spray on infected trees. Fomes lignosus was found to be the major root disease pathogen of Cola nitida, which was to a lesser extent also susceptible to Fomes noxius and Botryodiplodia theobromae. Guidelines for the control of Rigidoporus lignosus (synonyms include Fomes lignosus) on Hevea in the field have been reported. Treatments consist of various soil-applied fungicides. The disease symptoms on rubber are described, with notes on land preparation for replanting, curative treatment of immature and mature rubber trees, and leguminous cover crops in relation to disease incidence. iv DEDICATED TO MY BELOVED PARENTS v ACKNOWLEDGEMENT I am grateful to my almighty Allah who provided me energy to complete my review. My sincere thanks are to my honourable supervisor and teacher Prof. Dr. Mohammad Abdur Rahman, Forestry and Wood Technology Discipline, University of Khulna, Khulna for offering this review to me. I am indebted to my supervisor for the supply of information on this topic and constant encouragement provided during the preparation of the review. I owe a word of thanks to my younger brother Md. Khairuzzaman Shovon (Hons’ 00 Batch) for his help during this study. I am very grateful to my friend S. M. Nazmul Hossain and Pradip Kumar Sarkar for his continuous help during preparation of this review. I am also very thankful to my younger brother Ranju (’02 Batch) who helped me by way of making available their computer. Finally, I do express my thanks to all of my friends and well-wishers. LUBNA JAHAN vi CHAPTER ONE: INTRODUCTION 1.1 INTRODUCTION Fungi are the most important group of organisms contributing to wood decay. On the other hand, fungi living in symbiosis with living trees and forming mycorrhiza play a critical role in the enhancement of tree growth and vigor. Concerted evolution of woody plant-interacting fungi and their plant hosts is clearly apparent, and can be traced back to the Silurian period around 400 million years ago, when the first vascular plants emerged (Simon et al., 1993; Remy et al., 1994). As the first vascular plants lacked highly developed root systems, symbiotic associations with fungal endophytes might have been crucial for plant survival. Basidiomycetes, including wood-rotting fungi, diverged probably during the Jurassic period around 300 million years ago, at the time of emergence of the early gymnosperms (Berbee & Taylor, 1993). Fungi took advantage of increasing availability of plant materials. As all fungi are heterotrophic, they are dependent on extracellular nutritional sources, e.g. carbon and nitrogen. For this purpose they can either form symbiotic associations with plants or they secrete extracellular enzymes to degrade complex carbon and nitrogen sources, such as starch, pectin, cellulose, lignin and proteins (Carlile & Watkinson, 1994). The fungal kingdom consists of a wide variety of organisms including yeasts, puffballs, moulds, morels, toadstools and polypore fungi which form large bracketshaped fruiting bodies on wood. Polypore fungi belong to the basidiomycetes, a class that consists of highly advanced forms of fungi which have a special sexual life cycle. Basidiomycetes in particular are key players in wood degradation processes. Ascomycetes, such as morels, also produce typical structures for sexual spore formation and reproduction. By contrast, in many molds only a simple filamentous form is known. These fungi are often classified as deuteromycetes. These “lower fungi” can also potentially degrade complex plant polysaccharides and even lignin. Based on their mode of plant interaction, fungi are presently divided into 1 biotrophic, saprotrophic, and necrotrophic species. Typically, wood-colonising microorganisms, such as basidiomycete fungi, are saprotrophic and either pathogenic or harmless to the host plant. Necrotrophy describes a process, in which host tissues are first killed by the fungus and then utilised saprotrophically. Biotrophic fungi utilize living plant materials, whereas saprotrophic fungi gain essential nutrients from dead cell material. A special group of biotrophic fungi are those that form mycorrhiza. These nutritional traits do not represent unvarying trends. In fact, many fungi are not restricted to a single mode but show various degrees of flexibility during their life cycle (Cooke & Whipps, 1993). Figure 1.1: Rigidoporus microporus (Fr.) Overeem (Baroni, 1998). The fungal genus Fomes is a group of wood-decaying fungi that are found throughout the world on all types of wood — gymnosperms, hard and softwood dicots, and palms. Fomes lignosus (Klotzsch) Bres is a serious root rot pathogen of worldwide distribution. Its current name is Rigidoporus microporus (Sw.) Overeem 1924 and basionym is Polyporus lignosus Klotzsch 1833. F. lignosus is unable to synthesize the whole thiamine molecule; it can synthesize only one part, thiazole, and the other part, pyrimidine, must be supplied from other sources, e.g. wood, leaves etc (Riggenbach, 1957). 2 Following girdling experiments in the Congo showing the reduction of infection potential, girdling or poisoning before felling is suggested to ensure that the roots of trees so killed are colonized by saprophytic fungi antagonistic to the major root-rot pathogens (Fassi, 1968). F. lignosus in Hevea brasiliensis in Malaya by leguminous cover crops (Baker and Snyder, 1965). The fungi, both occurring parasitically and saprophytically, are described from sporophores and cultures (Bakshi, et. al., 1963). 3 1.2 OBJECTIVES OF THE STUDY Fomes lignosus/Rigidoporus microporus is an important fungus. At present there is no broad-based and comprehensive compilation of information available about it. Therefore my prime objective is to prepare a review containing different aspects dealing with the theoretical and applied perspectives of F. lignosus. The main objectives are• To know about the wood decay fungus of Fomes lignosus/Rigidoporus microporus. • To assemble, collect relevant information and to provide information in a readily available form to interested researchers, students, NGOs, industries, and traders on different aspects of Fomes lignosus, to highlight its importance. It is anticipated that will stimulate and encourage those concerned with the exploitation of the commercial potential of Fomes lignosus. 1.3 METHODOLOGY To prepare this review all relevant information has been collected from secondary sources. The literatures were mainly collected from Tree CD ROM, Internet, journals and text books. Tree CD provides abstracts of various internationally published journals on all aspects of forestry and forest products. The literatures were sorted out by subject matter of the titles based on which the convent pages were prepared and the body of the review was written up using available information. 4 CHAPTER TWO: GENERAL INFORMATION OF Fomes lignosus 2.1 ACCEPTED SCIENTIFIC NAME Fomes lignosus/ Rigidoporus microporus (Fr.) Overeem 1924 (accepted name) 2.2 COMMON NAME Common Names Name Language root white rot English white root disease English white rot English root rot disease English white cocoa root disease English white Hevea spp. root disease English white thread English caries blanca de la hevea Spanish caries blanca del cacao Spanish enfermedad de las raices blancas Spanish carie blanche de l'hevea French carie blanche du cacaoyer French maladie des racines blanches French pourriture blanche des racines French Weisse Wurzelfaeule Germany penyakit akar putih Indonesia Source: CAB International, 2005 2.3 SYNONYMS Ungulina auberiana (Mont.) Pat. 1900 (synonym) Ungulina contracta (Berk.) Pat. 1900 (synonym) Leptoporus concrescens (Mont.) Pat. 1903 (synonym) Leptoporus evolutus (Berk. & M.A. Curtis) Pat. 1903 (synonym) Polyporus concrescens Mont. 1835 (synonym) Trametes semitosta (Berk.) Corner 1989 (synonym) Polystictus petalodes (Berk.) Cooke 1886 (synonym) 5 Polyporus lignosus Klotzsch 1833 (synonym) Polystictus concrescens (Mont.) Cooke 1886 (synonym) Polyporus armatus (Pat.) Sacc. & Trotter 1925 (synonym) Fomes microporus (Sw.) Fr. 1821 (synonym) Fomes auriformis (Mont.) Sacc. 1885 (synonym) Polyporus bakeri (Pat.) Sacc. & Trotter 1925 (synonym) Polyporus contractus Berk. 1847 (synonym) Trametes limitata Berk. & M.A. Curtis 1872 (synonym) Polyporus auberianus Mont. 1842 (synonym) Coriolus hondurensis Murrill 1907 (synonym) Leptoporus armatus Pat. 1915 (synonym) Leptoporus bakeri Pat. 1915 (synonym) Polyporus evolutus Berk. & M.A. Curtis 1868 (synonym) Polystictus unguiformis (Lév.) Cooke 1886 (synonym) Boletus microporus Sw. 1806 (synonym) Polystictus hondurensis (Murrill) Sacc. & Trotter 1912 (synonym) Fomes semitostus (Berk.) Cooke 1885 (synonym) Fomes sepiater (Cooke) Cooke 1885 (synonym) Leptoporus lignosus (Klotzsch) R. Heim 1934 (synonym) Polyporus minutodurus Lloyd 1922 (synonym) Rigidoporus lignosus (Klotzsch) Imazeki 1952 (synonym) Fomitopsis semitosta (Berk.) Ryvarden 1972 (synonym) Oxyporus auberianus (Mont.) Kreisel 1971 (synonym) Rigidoporus concrescens (Mont.) Rajchenb. 1992 (synonym) Polyporus semitostus Berk. 1854 (synonym) 6 Fomes auberianus (Mont.) Murrill 1905 (synonym) Fomes lignosus (Klotzsch) Bres. 1912 (synonym) Oxyporus lignosus (Klotzsch) A. Roy & A.B. De 1998 (synonym) Polyporus microporus (Sw.) Fr. 1821 (synonym) Coriolus limitatus (Berk. & M.A. Curtis) Murrill 1907 (synonym) Microporus concrescens (Mont.) Kuntze 1898 (synonym) Microporus petalodes (Berk.) Kuntze 1898 (synonym) Microporus unguiformis (Lév.) Kuntze 1898 (synonym) Scindalma auriforme (Mont.) Kuntze 1898 (synonym) Scindalma microporum (Sw.) Kuntze 1898 (synonym) Scindalma semitostum (Berk.) Kuntze 1898 (synonym) Scindalma sepiatrum (Cooke) Kuntze 1898 (synonym) Trametes evolutus (Berk. & M.A. Curtis) Murrill 1907 (synonym) Ungulina semitosta (Berk.) Pat. 1900 (synonym) Polyporus auriformis Mont. 1854 (synonym) Polyporus petalodes Berk. 1856 (synonym) Polyporus phlebeius Berk. 1855 (synonym) Polyporus sepiater Cooke 1881 (synonym) Polyporus unguiformis Lév. 1846 (synonym) Rigidoporus evolutus (Berk. & M.A. Curtis) Murrill 1907 (synonym) Leptoporus contractus (Berk.) Pat. 1900 (synonym) Source: Anon, 2006 7 2.4 CLASSIFICATION OF FOMES LIGNOSUS (KLOTZSCH) BRES Kingdom: Fungi Phylum: Basidiomycota Class: Basidiomycetes Order: Polyporales Family: Meripilaceae Genus: Rigidoporus 2.5 EPIDEMIOLOGY White root rot. Rhizomorphs may extend through soil and along roots, several metres in advance of root penetration (Anon, 1999). 2.6 DISPERSAL Airborne, by rhizomorphs (Anon, 1999). 2.7 DISTRIBUTION Peninsular Malaysia; root; (Singh KG, 1980). 2.8 BIOLOGY, ECOLOGY AND MORPHOLOGY Wood refers to both the dead xylem cells in the center of the tree responsible for structural support (heartwood), and the living xylem cells beneath the bark that carry water and nutrients up the tree (sapwood). Most wood rot fungi degrade the heartwood. Brown rot fungi have enzymes that break down polysaccharides, but leave most of the brown-colored lignin. Most fungi cause white rot, degrading lignin along with the polysaccharides, leaving wood spongy and bleached. Pathogenic fungi attack sapwood and can kill the tree. Disease Cycle: R. lignosus is a rhizomorphic root-infecting fungus with an ectotrophic growth habit. The rhizomorphs extend ahead of the root rot and spread the disease to the tree collar and to other roots of the infected tree. Root contact spreads white root disease from a diseased tree to the roots of adjacent healthy trees. The infected trees are killed (CABI, 2002). 8 F. lignosus is unable to synthesize the whole thiamine molecule; it can synthesize only one part, thiazole, and the other part, pyrimidine, must be supplied from other sources, e.g. wood, leaves etc (Riggenbach, 1957). Describes laboratory and field experiments at the Rubber Research Institute, Kuala Lumpur, on sporophore development and spore yields, duration and intensity of sporulation under various observed conditions of humidity and temperature, 24-hour variations etc., and the static, rotary, and automatic volumetric traps used (Hilton, 1960). The migration of P32 from the host plant to the fungus, as well as its migration from the surface of the fruit-body of the fungus to its hymenial layer by direct application on the upper surface of the fruit body. The experiments included growing Fomes lignosus on carrot tissue culture that had previously absorbed P32; injection of P32 into a Lime tree just above and below sporophores of Ganoderma applanatus var. australis, and application of P32 to the upper surface of G. applanatus var. australis sporophores. Results indicated that the radioactive substance had migrated from the carrot tissue and the tree to the fungi and from the upper surface of the sporophore to the hymenial surface (Bose and Bonet, 1960). Figure 2.1: Rigidoporus microporus - white root disease - showing the fruiting body (Anon, 1999). 9 Affected Plant Stages: No information. Affected Plant Parts: Root. Symptom: Fungus spread through roots. Leaves of infected plants turned pale green, finally becoming yellow, dries and falls. White mycelium or rhizomorph is clearly visible on the root surface (Anon., 2001). Damage: Serious infection can cause the plant to die (Anon., 2001). 10 CHAPTER THREE: PATHOGENIC ROLE OF FOMES LIGNOSUS Fungi compose about 4% of the known species of life on earth and about 8% of estimated unknown species. In spite of their importance, less than 5% of the estimated 1.5 million fungi have been identified. This fact sheet is an inventory of wood decay fungi in American Samoa to date. Fungi that break down woody plants into their basic elements are a critical part of the tropical ecosystem. Without them, dead trees and shrubs would cover the soil and decompose very slowly. New seedlings not only need a clear path to the sunlight, they need the nutrients locked away in dead plants: Rotted wood enriches the soil for plant growth and improves its structure. 3.1 HOST PLANT FOR FOMES LIGNOSUS Hevea brasiliensis (rubber), Theobroma cacao (cocoa), Cocos nucifera (coconut), Coffea (coffee), Elaeis guineensis (African oil palm), Ipomoea batatas (sweet potato), Manihot esculenta (cassava), Nephelium lappaceum (rambutan), Piper nigrum (black pepper), Solanum melongena (aubergine).(CABI, 2002) Averrhoae carambola (Anon., 2001) 3.2 HEVEA BRASILIENSIS (RUBBER) It is a fungus generally associated with rubber plants. However, it has been found in the Congo where there are no rubber plants. It is spotted when the root area has mycelium threads of yellowish-white. The context chiefly of Rubber plantations, the infection potential of root-rot pathogens, especially F. lignosus, in tropical forests, including tabulated data on the relative frequency of fruiting bodies of F. lignosus, Armillaria mellea and other lignicolous Polyporaceae and Xylariaceae in various Congolese forest types and the mode and course of infection of plantations established on former forest sites. Following girdling experiments in the Congo showing the reduction of infection potential, girdling or poisoning before felling is suggested to ensure that the roots of trees so killed are colonized by saprophytic fungi antagonistic to the major root-rot pathogens (Fassi, 1968). The pathogen penetrates undamaged rubber roots directly; it does so more readily through wounds and natural openings. It is preferable to locate infected trees by their leaf symptoms rather than by root inspection, to avoid host injury. Initial penetration depends on mechanical pressure, but later extra cellular enzymes are involved. The fungus is intercellular in the 11 cortex and intracellular in the wood. The ray cell walls are penetrated mechanically, the xylem through pits. The yellowing and curling of leaves on infected trees appears to be due to root injury and not to fungal toxins. Host reactions to infection are the formation of a cork cambium in the cortex and the production of phenols and resins in woody tissue (Peries and Irugalbandara, 1973). 3.2.1 Ultrastructural Aspects of Rubber Tree Root Rot Diseases Rigidiporus lignosus and Phellinus noxius are two of the most severe decay-causing fungi of living trees in West Africa (Pichel, 1956) especially in the Ivory Coast (Nandreitsal, 1985). The root rot they cause is a lethal disease of Heveu brasiliensis (rubber tree). The fungi, living in the soil, contaminate the trees by developing rhizomorphs (R. lignosus) or mycelial sleeves (P. noxius) respectively. Light microscopical observations have shown that these organisms penetrate the tap root of rubber trees through lenticels or wounds and then destroy a large part of root tissues (Nicole et al., 1982 a). Biochemical studies confirm that the major cell wall components are degraded by extracellular fungal enzymes (Geiger et al., 1986a, c, d). But little information is available on the ultrastructure of white rots caused by R. lignosus and P. noxius. 3.2.1.1 Colonization and degradation of non lignified tissues Non lignified tissues of a young rubber tree are among other constituted of primary parenchyme (until 5 weeks old), suber and phloem. Phloem is highly differentiated and contains parenchymatous rays, companion cells, sieve tubes, tannin cells and laticifers. Thus, before wood invasion, R. lignosus and P. noxius have to degrade the major cell wall components of these tissues: cellulose, hemi-cellulose, pectin and suberin. Colonization: Intercellular and intracellular positions are adopted by both fungi. The location in the middle lamella causes pectin dissolution, favoured by hyphal ramifications (Fig. 3.1). Moving through the wall results in a digestion of this wall. The perforation begins with a digestive action (Fig. 3.2) which is often completed by a mechanical process (Fig. 3.3), as it is revealed by the compression of wall cellulose fibers during fungal growth (Nicole et al., 1987). 12 Fig. 3.1: Intercellular colonization of cortical tissues; adjacent cells are separated by a fungal ramification differentiated during the fungal growth (arrow); (x 5000) (Nicole et al., 1987). Fig. 3.2: The intracellular position of hyphae in cortical tissues results in wall-perforation; the digestion of the cellulosic framework is first characterized by granular zone near the fungal filament (arrow); (X 8000) (Nicole et al., 1987). Fig. 3.3: Cellulosic wall penetration; the enzymatic degradation of the wall (double arrows) is completed by mechanical processes (arrows); (X 15000) (Nicole et al., 1987). 13 Degradation: The degradation of cell walls occurs in contact with the hyphae or at some distance in front of them. In the parenchymatous cells, the cellulosic wall turns into an alveolar structure and looses its fibrillar structure (Figs. 3.4 and 3.5). The degradation is often achieved by the loss of the wall. Separation of cells is accompanied, especially in the secondary phloem, by a conspicious change in the intercellular space. The osmiophilic properties of the middle lamella increase (Fig. 3.6) and after its perforation, the erosion extends to the cellulosic wall (Fig. 3.7) before the complete digestion. The progression of R. lignosus and P. noxius in a young bark of rubber tree roots also affects suberized cell walls. The degradation is characterized by the increase of the wall electron opacity or by a direct perforation of walls (Fig. 3.8) (Nicole et al., 1987). Fig. 3.4: Aveolar aspects (arrows) of a cellulosic wall of a phloem ce17 degraded by R. lignosus, the fibrillar structure of the wall is profoundly pertubated (x 8000) (Nicole et al., 1987). Fig. 3.5: Middle lamella and cellulose fibers of a sieve tube cell wall in a healthy phloem; (X 20000) (Nicole et al., 1987). 14 Fig. 3.6: The degradation of the middle lamella causes the increase of its osmiophilic properties (arrows) before its perforation; (x ~0000) (Nicole et al., 1987). Fig. 3.7: Perforation of the middle lamella leads to meatus formation; the degradation then extends to the cellulosic wall (arrows); (X 10000) (Nicole et al., 1987). Fig. 3.8: Digestion of a part of a suberized cell wall in a young phellem cell (arrows); the degradation of these walls generally occurs when hyphae move in the wall or perforate it; (x 12500) (Nicole et al., 1987). 15 3.2.1.2 Colonization and degradation of lignified tissues Wood colonization: In vivo, xylem invasion by R. lignosus is independent of cortical tissuecolonization and occurs through the parenchymatous rays (Nicole et al. 1982 a). The hyphae can be found both within ray cells and the lumen of vessels. Their propagation from cell to cell frequently proceeds through pit membranes which are progressively eroded. The differentiation of microhyphae is rare (Fig. 3.9). For P. noxius, wood invasion starts after the colonization of all cortical tissues. The development of hyphae is similar to R. lignosus (Nicole et al., 1987). Fig. 3.9: Differentiation of microhyphae by R. Lignosus. Note the accumulation of electrondense particles near the hypha (arrow); (X 8000) (Nicole et al., 1987). Wood degradation by R. lignosus: The cell wall degradation is progressive and proceeds in contact with or in front of hyphae. The alteration occurs inwards, from the middle lamella towards the lumen. Two stages characterize the middle lamella and the primary wall degradation: a) an apparition of a granular matrix, after the disorganization of the native structure (Fig. 3.10); b) a progressive perforation of this matrix, causing meatus formation (Fig. 3.11). Then, the alteration reaches the less lignified secondary wall. The junction of S1 and S, layer is particularly susceptible to the fungal action. Indeed, small cavities appear at this level (Figs. 3.12 and 3.13), amalgamate and then extend inwards until causing the disparition of the half S2 layer (Fig. 3.14), showing a strong digestion of the wall framework. S3 layer is saved up by this mechanism. When the progression of decay occurs outwards, the S3 layer is degraded; on this case only S2 and S1 layers are less altered (Nicole et al., 1987). 16 Fig. 3.10: During xylem middle lamella degradation we note first the disorganization of the native structure (1) causing the apparition of a granular matrix (2) and, secondly, the perforation of this matrix and meatus formation (3); (X 20000) (Nicole et al., 1987). Fig. 3.11: After meatus formation resulting in an alteration of middle lamella, the digestive action extends to the primary wall (arrows); (x 20000) (Nicole et al., 1987). Fig. 3.12: Organization of walls of a xylem vessel of a healthy young root; (x 12500) (Nicole et al., 1987). 17 Figs. 3.13 and 3.14: Wood degradation by R. lignosus: a cross section through a vessel wall shows the dissolution of the S1/S2 border layer of the secondary wall characterized by small cavities (arrows) (3.13); the alteration then extends to the S2 layer (arrows) (3.14). (Fig. 3.13: x 25000; Fig. 3.14: x 15000) (Nicole et al., 1987). 3.3 TECTONA GRANDIS (TEAK) Root disease of teak (Tectona grandis) is widely distributed in Nigeria, where it is present in c. 70% of teak plantations. The disease is caused by Rigidoporus lignosus, sporocarps of which have been found in 64% of the infected plantations. Disease incidence is more serious in shallow lateritic soils and sites with impeded drainage. The disease may be controlled by using 2% tillex spray on infected trees. It can also be largely reduced in proposed plantations by careful site selection and pre-treatment of stumps left behind after land clearing (Momoh, 1976). 18 3.4 COLA NITIDA Fomes lignosus was found to be the major root disease pathogen of Cola nitida, which was to a lesser extent also susceptible to Fomes noxius and Botryodiplodia theobromae. As a detection method, collar inspection was found to be more reliable than foliage inspection. In clear-felled plots, root disease incidence was high only in the first few years after establishment, during which lost stands were replaced without much loss in long term revenue. This method of establishment is, therefore, to be preferred to others (Adebayo, 1975). 3.5 MANIHOT ESCULENTA (CASSAVA) Cassava is grown primarily for the tubers which are used as a foodstuff. Tubers may be eaten raw, boiled or fried, or in baked goods. For agricultural purposes, cassava is propagated exclusively by vegetative means from stem-cuttings. It is raised from seed only for the purpose of selection. Cassava has varying numbers of pests in various localities. A worldwide survey shows the following fungi attacking the crop: Absidia cristata, Armillaria mellea, Asterina manihotis, Botryodiplodia theobromae, Botryosphaeria ribis, Cercospora cearae, C. caribaea, C. henningsii, C. manihotis, Colletotrichum manihotis, Corticium rolfsii. Corynespora cassiicola, Diplodia manihotis, Fomes lignosus, F. noxius, Fusarium gibbosum, F. solani, Ganoderma lucidum, Gleosporium manihotis, Glomerella singulata, S. manihotis, Haplographium manihoticola, Hendersonula toruloidea, Hypomyces haematococcus, Irenia entebbensis, Lasiodiplodia theobromae, Megalonectria pseudotrichia, Microsphaeria euphorbiae, Oidium manihotis, Ophiobolus manihotis, Periconia byssoides, P. pycnospora, Phaebotryosphaeria plicatula, Phymatotrichum omnivorum, Physalospora abdita, Ph. rhodina, Phyllosticta manihot, Phytophtora parasitica, Polyporus sapureme (rotting or roots, "saporema," stinking-rot), Polystictus occidentalis, Ragnhildiana manihotis, Rhizopus stolonifer, Rhizoctonia solani, Rosellinia bunodes, Schizophylum alneum, Sclerotium rolfsii, Sphaceloma manihoticola, Tryonectria pseudotrichia, Uromyces janiphae and Verticillium dahliae (Duke, 1983). 3.6 ACACIA MANGIUM (MANGIUM) Mangium is a major fast-growing tree species in forestry plantation programmes in Asia and the Pacific. It tolerates varied site conditions and has adaptability to different planting objectives. Mangium shows most vigorous growth on well-drained, fertile soils in high 19 rainfall areas (>2000 mm annually) in the humid tropics. Although root rot disease caused by Ganoderma sp. (red rot), Phellinus sp. (brown rot) and Rigidoporus lignosus are major problems in mangium stands, there are no specific control recommendations against these fungi. Signs of the disease are evident on the roots after the tree has fallen or upon excavation. Depending on, which fungus causes the disease; there may be dark reddish granular rusty brown encrustation or white thread-like rhizomorphs on the surface of the rots. The usual method of controlling root rot caused by fungi that spread by root contact is to remove and destroy all diseased roots and woody debris (Kerala Agricultural University, 2002). 3.7 TRIPLOCHITON SCLEROXYLON The effect of F. lignosus (Klotzsch) Bress on Triplochiton scleroxylon K. Schum was determined by artificially inoculating 5 to 6-week old seedlings, as well as by conducting a field survey on 1 to 4-year old trees. Inoculated seedlings did not show any foliar symptoms of infection during 4 months of observation. Though heights of inoculated seedlings were not affected by the pathogen, diameters of such seedlings were significantly smaller (atP=0.05) than those of control seedlings. Naturally infected T. scleroxylon trees in the field were very often found close together, usually around infected tree stumps. Leaves of diseased trees remained healthy-looking, thus making detection of the disease difficult in trees lacking signs (viz. rhizomorphs and fruitbodies) of the pathogen (Begho and Ekpo, 1986). 3.8 DECAY OF RHIZOME ROOT AND BASAL CULM Disease causing decay of rhizome, root and basal culm has been reported on different species of bamboos from India, the Philippines, Malaysia and Pakistan. The disease has been recorded on Bambusa bambos in Uttar Pradesh, West Bengal and Kerala, India and on Melocanna baccifera in West Bengal and Assam in India and Bangladesh. Root decay (white rot) of Dendrocalamus giganteus Munro caused by Fomes liguosus (Klotzch) Bres. has been recorded in Malaysia. Ganoderma root rot of bamboos has been recorded in Pakistan and the Philippines (Anon, 1995). Symptoms: The disease causes white spongy to fibrous or brown cubical rot of root, rhizome and basal part of the culm. The sporophores of the fungus develop on the affected bamboo culms at the ground level and on the exposed parts of the affected rhizomes (Figure 3.15). 20 Figure 3.15: Decay of basal culm in B. bambos caused by Polyporus sp (Anon, 1995). Causal Organisms: Ganoderma lucidum (Leyos.) Karst; Polyporius bambusicola P. Henn; Poria rhizomorpha Bagchee and Fomes lignosus (Klotzch) Bres. (Anon, 1995). Etiology: Ganoderma lucidum is a serious root rot pathogen of worldwide distribution. It attacks a large number of broad-leaved, sub-temperate and temperate tree species. It is normally endemic to natural forests and does not cause any serious damage. However, when natural forests are clear-felled, G. lucidum spreads quickly to residual roots and stumps to build up a high inoculum potential. Raising new plantations in such areas without clearing the infected residual stumps and roots causes severe damage to susceptible species. The lateral spread of the disease takes place through root contact. The strictly parasitic habit of G. lucidum makes it incapable of freshly colonizing dead roots or stumps. The fungus is also unable to make free mycelial strands in the soil, except on root surfaces, or outside the roots when in contact with a solid surface like the roots of adjoining plant. Thus, healthy dumps become inflected when their roots come in contact with decayed wood. Poria rhizoniorpha occurs as a saprophyte in the soil, forming abundant rhizomorph strands on decaying roots and other debris. It becomes parasitic in poor and badly drained soils and spreads by means of rhizomorphs. Fomes lignosus attacks living sapwood as well as heartwood. The food base or the wood mass colonized by the fungus is important in root disease development. Fructifications of the fungus arc produced on the affected parts and on humus around the bamboo clumps which serve as the sources of fresh infection (Anon, 1995). Control: Silvicultural measures like isolation trenches may prove effective in containing the disease in between the trenches, thus preventing its spread. 21 3.9 STRIP PLANTATIONS In 1990, a serious root rot disease was observed in different strip plantations of Court Chandpur-Subdalpur railroad, Jessore-Benapole highway and Jessore-Satkhira road of greater Jessore district, Bangladesh. These plantations were covered with trees such as Cassia siamea, Acacia auriculiformis, Acacia nilotica, Albizia procera, Leucaena leucocephala and Dalbergia sissoo. The affected trees died in patches showing wilting symptoms. The leaves of affected trees became brown, dried up and remained attached to the dead branches. The fungus responsible for the disease was isolated and identified as Fomes lignosus [Rigidoporus lignosus]. The occurrence of root rot due to F. lignosus is claimed to be the first in Bangladesh (Basak, 1999). 3.10 MANAGEMENT AND CONTROL R. microporus establishes on stumps of felled forest trees and in roots, which provide a reservoir of infection for later planted tree crops. Ground should thus be prepared 3-4 years prior to planting, allowing for disintegration of infected wood and roots. A thick ground cover will also hasten decay of root fragments. Remove diseased trees and trench to prevent lateral spread (Anon, 1999). Cook et al. (1995) stated: Growth and reproduction of the same plant species at the same sites year after year is the norm in natural plant communities.…Selection pressure imposed by soil borne pathogens may favor…plants with the ability to support and respond to populations of rhizosphere microorganisms antagonistic to their pathogens. Very elegant and well-documented example of a systems approach to disease management comes from a unique rubber production system in Kuala Lampur. Suppression of root rots (causal agents Fomes lignosus and Ganoderma pseudoferreum) when replanting rubber plantations is generated through cultural practices such as saprophytic colonization of old rubber trees, rogueing of diseased plants, and planting mixed understory legumes (Pueraria phaseoloides, Centrosema pubescens, and Calapogonium mucunoides). Rubber is typically replanted immediately after old trees are destroyed, because land is limited. Old trees are poisoned to accelerate colonization by saprophytes before felling (Fox, 1965). Creeping legumes are planted between the rows of rubber seedlings to cover 70% of the soil surface 22 (they are not planted directly within the row of rubber trees) at planting. Over a 60-year period, as the young rubber trees grow, the covers are shaded out and replaced by shadetolerant indigenous species. This creeping cover system creates a form of crop rotation for what is otherwise continuous rubber production. Rubber seedlings planted into infested soil planted to individual or mixed stands of creeping legumes survive better than seedlings planted into clean cultivated fields or planted to grass species (Cronshey and Barclay, 1939; Fox, 1965; Napper, 1932). The creeping covers provide a decoy substrate (physically separated from the young seedlings) to prevent pathogenic colonization of the rubber roots, and they enhance the decay of diseased roots from previous rubber plantings by fixing N and reducing the C: N ratio in the decaying wood, thereby reducing substrate energy availability to the pathogens (Watson et al., 1964). In addition, the covers generate a litter layer that supports antagonists of the pathogen propagules. This system is termed decoy, decay, and deter (Fox, 1965). Infected roots should be removed and the surrounding soil is drenched with systemic fungicide. Plants with serious infection should be removed and burned together with the infected roots (Anon, 2001). An international symposium on factors determining the behavior of plant pathogens in the soil, held at Berkeley in April, 1963. Most of the 39 papers review aspects of the problem without reference to specific crops. R. A. Fox describes the control of Fomes lignosus in Hevea brasiliensis in Malaya by leguminous cover crops (Baker and Snyder, 1965). The fungi, both occurring parasitically and saprophytically, are described from sporophores and cultures (Bakshi, et. al., 1963). Field trials over 3 years showed that 6-monthly application of 10 g tridemorph (as Calixin) per tree could protect Hevea from F. lignosus (Rigidoporus lignosus) infection. All plantations in the country are now examined for diseased trees once a year and such trees and their immediate neighbours are treated twice a year with Calixin; this procedure appears to give promising results (Canh, 1984). Guidelines for the control of Rigidoporus lignosus (synonyms include Fomes lignosus) on Hevea in the field are presented. Treatments consist of various soil-applied fungicides. Recommendations for removal of infected material and measures for the prevention of the disease are included (Canh, 1996). 23 The disease symptoms on rubber are described, with notes on land preparation for replanting, curative treatment of immature and mature rubber trees, and leguminous cover crops in relation to disease incidence (Liyanage, 1976). Generally speaking, the white root-rot fungus (Fomes lignosus) predominates in young rubber plantations (up to the age of six or seven years) in West Java and the agent of red root rot (Ganoderma pseudoferreum) in older ones, but in 1940 the former organism was shown to be responsible for large gaps even in long-established gardens. The incidence of Oidium [heveae] was very high whereas that of Phytophthora spp. and Gloeosporium [alborubrum] was negligible. When 1/4 lb S was used in the planting holes to control Fomes lignosus there was no retarding effect on the growth of the young trees. In preliminary trials against G. alborubrum NiCl2 appeared to give satisfactory control (Peries, 1972). A minor leaf spot disease (Pestalotiopsis versicolor) is newly recorded in W. Malaysia. Acremonium sp. stopped mycelial growth and sporulation of O. heveae on naturally infected leaves of rubber (Rao, 1972). Basidiospores of Corticium salmonicolor were trapped 100 m from the source of inoculum, indicating wind transport. Free water was essential for their germination, which was hastened by extracts of Hevea bark and malt. Trials have underlined the importance of the carrier in the degree of control obtained with fungicides. Natural rubber latex appears mostly worthy of further development as a carrier for tridemorph, the most promising fungicide (Rao, 1972). 24 CHAPTER FOUR: CONCLUSION 4.1 CONCLUSION The fungal genus Fomes is a group of wood-decaying fungi that are found throughout the world on all types of wood - gymnosperms, hard- and softwood dicots, and palms. Fomes lignosus is a serious root rot pathogen of worldwide distribution. White rot fungi are believed to be the most effective lignin-degrading microbes in nature. As a white rot fungus F. lignosus breaks down lignin and cellulose and commonly cause rotted wood to feel moist, soft, spongy or stringy and to appear white. F. lignosus is one of the commonly encountered landscape tree pathogens with these capabilities. Fungicides are not very effective in killing well-established wood-rotting fungi. To limit the fungus, one has to protect soils and trees from compaction, root damage and remove infected trees immediately. Infected trees may topple before any sign or symptom becomes obvious. 25 REFERENCES Adebayo, A.A. 1975. Studies on the Fomes root diseases of kola (Cola nitida (Vent.) Schott and Endlicher). Gambari Experiment Station, Ibadan, Nigeria. GhanaJournal-of-Agricultural-Science. 8: 1, 11-15; 14 Anon, 1975. Tropical crops. 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A Check List of Host and Disease in Malaysia, Ministry of Agriculture: 116-117, 246 Tappan,W.C. and Kilpatrick, J.J. 1970. Pre-treatment of forest trees for root disease control in hevea planting. Part I: Forest inventory and analysis of arboricides applied prior to felling. Rubber Research Institute, Benin, Nigeria. Journal-of-theWest-African-Science-Association. 15: 2, 102-112; 4 32