Research Highlights of the CIMMYT Wheat Program 1999-2000

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New Bread Wheats for High Rainfall Environments: The Package M. van Ginkel and L. Gilchrist High rainfall environments make up the second major mega-environment where bread wheat is grown in the world, after irrigated production areas. Particularly in developing countries, regions receiving more than 500 mm of rainfall during the cropping cycle suffer retarded economic development and the associated curses of unemployment, poverty, ill health, and high infancy death rates. Such areas include parts of Eastern, Central, and Southern Africa, the Andean Region of South America, China, and pockets in South Asia. Enormous progress has been achieved in disseminating so-called modern varieties in irrigated regions around the world. Key wheat ideotypes, such as the Veerys and, more recently, the new wheats Kauz and Attila, have demonstrated their wide adaptation and stable performance across this irrigated agro-ecological zone. Adoption of modern wheats has reached almost 100% in high rainfall areas in the last decade. However, few genotypes have shown to contain the complete “package” of requirements for that zone. The Bobwhites constituted an impressive advance some 20 years ago, but with evolving diseases and market demands, new varieties are continuously needed. Usually varieties do well for a certain period and then succumb to diseases, or their quality characteristics remain poor, and local mills import most of the wheat they require, negatively impacting local wheat producers. There are several reasons for production instability in high rainfall areas. For example, more diseases thrive under higher humidity conditions than in irrigated or rainfed areas with low humidity, and nutrient imbalances (both deficiencies and toxicities) are more pronounced in regions where leaching associated with high rainfall is prevalent. In many of these areas, wheat has been imported in large amounts, for a variety of reasons, including famines, political mismanagement of food resources, lack of support for agricultural research, immigration/emigration pressures, cost/benefit considerations, and the high industrial quality of imports. Imported wheats generally come from one or more of the top four wheat exporters in the world: USA, Canada, Argentina, and Australia. Since these countries grow wheat mostly under rainfed conditions and produce the low yields (1.5- 2.5 t/ha) associated with elevated protein levels, imported wheat is generally of superior quality. Traits for High Rainfall Wheats If a nation in a high rainfall area aims to satisfy some, most, or all of its domestic wheat needs, its breeders must address an extensive list of traits. Wheats targeted towards high rainfall areas should have some or, ideally, all of the following key traits: 1. Yield a. High* b. Stable* 2. Disease resistance a. Stripe rust* b. Leaf rust* c. Stem rust* d. Septoria tritici* e. Fusarium spp. (head scab)* f. Barley yellow dwarf virus g. Soil-borne pathogens h. Tan spot i. Powdery mildew 8
3. Abiotic stress tolerance a. Sprouting* b. Soil acidity c. Nutrient imbalances* d. Waterlogging 4. Industrial quality a. Bread making* b. Cookie quality c. Noodle quality (for China and Southeast Asia) Though not all these traits are usually present in the same variety, the 10 marked by an asterisk (*) often constitute the minimum requirement in a high rainfall environment, compared to 5-7 key traits needed in wheats targeted to irrigated environments. Breeding wheats that meet these requirements poses a difficult challenge—one that requires concerted efforts to meet it. The difficulty is compounded by the fact that many countries in high rainfall areas have been investing less in wheat research in recent years. Breeding and Selecting High Rainfall Wheats Breeding wheats possessing the set of traits required in a given target environment is key to getting local farmers to adopt them. To incorporate the key groups of traits detailed above breeders must apply different methodologies; each group will therefore be discussed separately. Yield Traits contributing to high, stable yields across all potential production conditions within the high rainfall mega-environment are not unlike those needed to produce top yields in less stressed conditions under irrigation. Optimum input use efficiencies should result in maximum output (grain yield) per hectare. Hence in the hybridization process of a breeding program targeting high rainfall conditions, the highest yielding genotypes under irrigated conditions should be exploited, i.e., yield genes governing internal physiological processes should be transferred to potential high rainfall wheats. These genes constitute the genetic core of a variety and determine its ultimate yield potential. In addition to the top irrigated wheats, the best yielding high rainfall wheats are also sources of genes for yield. Table 1 lists some of the highest yielding wheats tested under high rainfall conditions in Mexico, in comparison to the check line Prinia. In all three crosses listed in Table 1, top-yielding irrigated wheats (Veery #9, Seri M82, and Tui) are present as progenitors and presumably contributed “yield genes.” An example of an outstanding high rainfall progenitor is Bobwhite, which in the past two decades has proven to be high yielding and stable in such areas around the world. Disease resistance Once the introgression of yield genes into a variety has been secured, their potential must be protected from diseases so that high yields will be phenotypically expressed in farmers’ fields. Protective disease resistance genes should be incorporated into the new wheat through the proper choice of additional parents in the crossing process. Horizontal resistance is pursued against diseases known to have host-pathogen interactions of a specific, race-type nature. Though these diseases are restricted mostly to the rusts, some claim that certain foliar blights also show interactive behavior. Horizontal resistance is also known as adult-plant, partial, or field resistance and, in the case of the rusts, as slow-rusting resistance. This type of resistance is achieved by accumulating several genes, each with minor additive effects. Parents are used in combinations that will yield progenies carrying three or more minor resistance genes for each of the relevant diseases. In the case of the rusts, Table 1. High yielding lines compared to the check variety Prinia, 2000 crop cycle, Toluca, Mexico. Yield Prinia Cross Selection history (t/ha) % PFAU/BOW//VEE#9/ CMSS95Y02460S-0100Y-0200M- 10.87 143 3/DUCULA 19Y-010M-6Y-030M-2SJ-0Y PGO/SERI//BAU/ CMSS95Y02262S-0100Y-0200M- 10.73 141 3/DUCULA 10Y-010M-10Y-030M-2SJ-0Y MILAN/TUI CMSS95Y02595S-0100Y-0200M- 10.36 131 2Y-010M-5Y-030M-3PZ-0Y 9
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 16 and 17: CIMMYT scientists have published on
Page 18 and 19: Taken together these data indicate
Page 20 and 21: Evaluating Advanced Materials Targe
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,
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in ECSA rely heavily on CIMMYT whea
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the pivotal role of Kulumsa in the
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Regional wheat quality classificati
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Table 5. Regional screening nurseri
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In 1992-93 the CIMMYT office in Tur
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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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