Septoria and Stagonospora Diseases of Cereals - CIMMYT ...

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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.: CIMMYT. pp. 34-40. 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- Mycosphaerella graminicola pathosystem II. Analysis of interaactions between pathogen isolates and host cultivars. Phytopathology 86:213-220. 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. Phytopathology 86:777-786. 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.
Page 1 and 2: Septoria and Stagonospora Diseases
Page 3 and 4: ii The Organizing Committee express
Page 5 and 6: iv 87 Genetic Variability in a Coll
Page 7 and 8: vi Foreword In the mid-1970s the id
Page 9 and 10: 2 Opening Remarks — S. Rajaram ar
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Page 26 and 27: Session 1: Pathogen Biology Biology
Page 30 and 31: Molecular Analysis of a DNA Fingerp
Page 32 and 33: histidine kinase in yeast, although
Page 34 and 35: According to the previous observati
Page 36 and 37: cultivars. The presence of pycnidia
Page 38 and 39: Provided that S. nodorum fungal gen
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Page 42 and 43: Table 1. Sources of isolates or DNA
Page 44 and 45: Septoria/Stagonospora Leaf Spot Dis
Page 46: Interrelations among Septoria triti
Page 49 and 50: 42 Session 2 — B.M. Cunfer disper
Page 51 and 52: 44 Session 2 — B.M. Cunfer beyond
Page 53 and 54: 46 Aggressiveness of Phaeosphaeria
Page 55 and 56: 48 Session 2 — P. Halama, F. Lala
Page 57 and 58: 50 Growth of Stagonospora nodorum L
Page 59 and 60: 52 Session 3A — G.H.J. Kema and E
Page 61 and 62: 54 A Possible Gene-for-Gene Relatio
Page 63 and 64: 56 Diallel Analysis of Septoria Tri
Page 65 and 66: 58 Session 3A — X. Zhang, S.D. Ha
Page 67 and 68: 60 Session 3A — L. Gilchrist, C.
Page 69 and 70: 62 Session 3A — L. Gilchrist, C.
Page 71 and 72: 64 Session 3B — E. Arseniuk and P
Page 75 and 76: 68 Cultivar variances Cultivar vari
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72 Session 3B — N.E.A. Murphy, R.
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74 Inheritance of Septoria Nodorum
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76 Session 3B — N.E.A. Murphy, R.
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78 Session 4 — B.A. McDonald, C.C
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84 Session 4 — E. Arseniuk, H.S.
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86 Session 4 — C. Cowger, C.C. Mu
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88 each isolate. Two of the probes
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90 Mating Type-Specific PCR Primers
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92 Session 4 — Bennett, R.S., S.-
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94 Session 5 — M.W. Shaw and the
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96 Session 5 — M.W. Shaw The path
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98 Spore Dispersal of Leaf Blotch P
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Session 5 — C.A. Cordo, M.R. Sim
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102 Epidemiology of Seedborne Stago
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Session 5 — D.A. Shah and G.C. Be
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106 Session 6A / Session 6B — J.M
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Session 6A / Session 6B — C.C. Mu
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118 Session 6C — M. van Ginkel an
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Session 6C — G. Shaner 128 An exa
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Session 6C — G. Shaner 130 Anothe
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Session 6C — M. Díaz de Ackerman
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134 Septoria tritici Resistance Sou
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Session 6C — L. Gilchrist et al.
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Session 6C — L. Gilchrist et al.
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140 Selecting Wheat for Resistance
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Session 6C — R.M. Gonzalez I., S.
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Session 6C — R.M. Gonzalez I., S.
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Session 6C — R. Loughman, R.E. Wi
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148 Field Resistance of Wheat to Se
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150 Using Precise Genetic Stocks to
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Session 6C — C.M. Ellerbrook, V.
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154 Evaluating Triticum durum x Tri
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156 Sources of Resistance to Septor
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Session 6C — H. Toubia-Rahme and
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160 Partial Resistance to Stagonosp
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Session 6C — C.G. Du, L.R. Nelson
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Session 6C — D.E. Fraser, J.P. Mu
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Session 6C — C.G. Du, L.R. Nelson
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Session 6C — M. Mincu 168 Arcsin
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170 Comparison of Greenhouse and Fi
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Session 6C — S.L. Walker, S. Leat
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Session 6D — L.N. Jørgensen, K.E
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Concluding Remarks — Z. Eyal 178
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184 Dr. Patrice Halama Professor In
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186 Dr. Hala Toubia-Rahme Research
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Septoria and Stagonospora Diseases of Cereals - CIMMYT ...

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