Septoria and Stagonospora Diseases of Cereals - CIMMYT ...

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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,
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: vi Foreword In the mid-1970s the id
Page 11 and 12: 4 Opening Remarks — S. Rajaram Ta
Page 13 and 14: 6 Opening Remarks — S. Rajaram cu
Page 15 and 16: 8 Opening Remarks — S. Rajaram br
Page 17 and 18: 10 Opening Remarks — S. Rajaram T
Page 19 and 20: 12 Opening Remarks — S. Rajaram t
Page 21 and 22: 14 Opening Remarks — S. Rajaram C
Page 23 and 24: 16 Opening Remarks — S. Rajaram r
Page 26 and 27: Session 1: Pathogen Biology Biology
Page 28 and 29: Table 2. The Septoria tritici/Stago
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
Page 40 and 41: ;; yy ;; yy 6 28% 1 32% ;y; ; y y ;
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
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52 Session 3A — G.H.J. Kema and E
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54 A Possible Gene-for-Gene Relatio
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56 Diallel Analysis of Septoria Tri
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58 Session 3A — X. Zhang, S.D. Ha
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60 Session 3A — L. Gilchrist, C.
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62 Session 3A — L. Gilchrist, C.
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64 Session 3B — E. Arseniuk and P
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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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176
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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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