Research Highlights of the CIMMYT Wheat Program 1999-2000

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Evaluating Advanced Materials Targeted for International Distribution Once advanced lines have been identified, they are yield tested at Obregon under two contrasting moisture regimes to identify the drought tolerant, input responsive genotypes. Following three years of yield and disease evaluation, the selected lines enter the CIMMYT international nursery system in one of the three following nurseries: • SAWYT – Semi Arid Wheat Yield Trial • SAWSN – Semi Arid Wheat Screening Nursery • HLWSN – High Latitude Wheat Screening Nursery Data on the performance of these lines across the target marginal areas are collected by regional cooperators and returned to CIMMYT to aid the selection of parents for the crossing program. Progress to Date in Breeding for Marginal Areas Prior to the introduction of the SAWYT in the early 1990s, the national agricultural research programs of most wheat growing developing countries selected materials for their marginal areas from CIMMYT’s traditional irrigated nurseries with significant success. A recent examination of the performance of 20 years of the Elite Spring Wheat Yield Trial (ESWYT) indicated that yield improved across this period at close to 4% per year (Pingali, 2000). All materials entering the ESWYT have been bred and selected under optimally irrigated conditions. However, results from the SAWYT indicate that rates of progress can be improved through the deployment of materials bred and targeted to moisture stress conditions. In low yielding environments (less than 2.5 t/ha), rates of progress, expressed as yield advantage of the best five lines over the local check cultivar, have increased from 12% in 1991 to 38% in 1997 (Figure 1). Similarly, the yield advantage of these top ranking genotypes in environments suffering intermediate levels of stress (2.5-4.5 t/ha) has improved from 16% to 45% over the same time period. The regression of yield advance over time was significant for both low and intermediate yielding environments (r 2 = 0.62, P
e selected from either the SAWYT or SAWSN in nearly every environment, not all environments differentiated germplasm in the same way as Obregon. Results indicated that a small adjustment to the timing of drought stress in Obregon could improve the correlated ranking of Obregon with some environments, particularly in the Southern Cone of South America. Combining what we know of global wheat environments on the basis of yield performance with GIS and other environmental variables will help to improve definition of the marginal areas and better target germplasm to CIMMYT’s regional cooperators. Advances in molecular biology are expected to provide exciting opportunities to improve the efficiency of wheat breeding for marginal areas. Functional genomics in particular may provide the knowledge needed to enhance parental selection and identify gene clusters important in conferring adaptation to stress. Genomics will likely be a more powerful tool than QTL analysis, as drought tolerance is likely to be controlled by many hundreds, possibly thousands, of gene loci. To complicate matters, these loci “clouds” will change with the environment. As a minimum, DNA fingerprinting of key parental stocks will allow breeders to better design crosses and calculate coefficients of parentage more realistically. Understanding the Target Environment The adaptation of germplasm to marginal areas involves much more than just drought tolerance. For one thing, root health often determines a plant’s ability to perform well under drought. Root growth can be influenced by a number of biotic and abiotic factors including nematodes, root rots, and micro-nutrient toxicities and deficiencies (Table 1). Many of these traits are simply inherited and can be manipulated to improve general adaptation to marginal areas. Bioassays for root diseases are difficult to manage and escapes are frequent; therefore, molecular markers (if available) offer significant advantages. The CIMMYT Wheat Program routinely uses a PCR assay to determine nematode resistance, and more markers are undergoing validation. We know that significant genotype x location interaction occurs from the deployment of SAWYT and ESWYT across many environments, yet we do not understand why certain genotypes perform well in one environment and collapse in another. Deployment of a probe set of genotypes, differentiating for the key soil-borne stresses, is planned over the next few years. It is hoped that this trial will shed some light on the major limitations to the adaptation of wheat in many key marginal areas. This knowledge will help breeders at CIMMYT target germplasm to regions. For example, some areas may be prone to root lesion nematode, and more appropriate advanced lines and parental materials could be provided to our partners there. Knowledge of such constraints is a powerful tool in our efforts to achieve increased food production in the coming decades. As farmers become conscious of the need to conserve soil moisture and reduce erosion (Table 1), farming practices are changing in many wheat growing areas. Wheat breeding programs must be proactive in promoting changes in their selection and evaluation strategies to reflect the changing environment. If research suggests that no genotype x tillage practice interaction exist in a given region, Table 1. Factors affecting yield in dry environments. Patterns of Nutrient stress and Agronomic moisture stress Temperature extremes pH extremes Biotic stress practices Terminal Heat stress; humid P and N deficiency/efficiency Root rots Stubble retention Pre-anthesis Heat stress; dry Deficiency (e.g. zinc) Nematodes Zero tillage Residual moisture Cold stress Toxicity (e.g. boron) Foliar pathogens Crop rotations Reduced irrigation Cold stress–late frost Acid soils, mineral Shifting cultivation General low rainfall Acid soils, volcanic/organic Water harvesting Shallow, marginal, Alkaline soils infertile, eroded lands 15
Page 2 and 3: Research Highlights of the CIMMYT W
Page 4 and 5: Table of Contents New Conservation
Page 6 and 7: Foreword We are pleased to initiate
Page 8 and 9: Hobbs on the zero-till planters fro
Page 10 and 11: Burning is practiced due to a lack
Page 12 and 13: (0.64 million ha), and Bolivia (0.2
Page 14 and 15: New Bread Wheats for High Rainfall
Page 16 and 17: CIMMYT scientists have published on
Page 18 and 19: Taken together these data indicate
Page 22 and 23: this may simply reflect a lack of v
Page 24 and 25: eleased in more than 30 countries u
Page 26 and 27: Parallel enhancement of yield compo
Page 28 and 29: Taken together, these factors sugge
Page 30 and 31: of improved seed and new technologi
Page 32 and 33: The high cost of hybrid seed is one
Page 34 and 35: Only a few cultivars performed well
Page 36 and 37: in CAC. In Turkey, the advantage ov
Page 38 and 39: ows, 2 m long). One plot was inocul
Page 40 and 41: Table 2. Wheat production statistic
Page 42 and 43: Based on farmers’ preferences, 12
Page 44 and 45: Global Monitoring of Wheat Rusts, a
Page 46 and 47: Monitoring nurseries The nurseries
Page 48 and 49: controlled by several QTLs with sma
Page 50 and 51: environments with strong disease pr
Page 52 and 53: eselections, studies at CIMMYT have
Page 54 and 55: References Johnson, R. 1978. Practi
Page 56 and 57: spike. Interaction between Lr19 and
Page 58 and 59: variation in the trait. Both grain
Page 60 and 61: the variation in yield (Figure 2).
Page 62 and 63: References Amani, I., R.A. Fischer,
Page 64 and 65: in ECSA rely heavily on CIMMYT whea
Page 66 and 67: the pivotal role of Kulumsa in the
Page 68 and 69: Regional wheat quality classificati
Page 70 and 71:
Table 5. Regional screening nurseri
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In 1992-93 the CIMMYT office in Tur
Page 74 and 75:
In addition to shuttle breeding sev
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the CIMMYT wheat breeding program.
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Five participants thought the level
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35. Skovmand, B.; López C., C.; S
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94. Tanner, D.G. 1999. Principles a
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182. Díaz de León, J.L.; Escoppin
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258. Mujeeb-Kazi, A.; Delgado, R.;
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CIMMYT-Derived Bread Wheat, Durum W
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Research Highlights of the CIMMYT Wheat Program 1999-2000

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