Research Highlights of the CIMMYT Wheat Program 1999-2000

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References Johnson, R. 1978. Practical breeding for durable resistance to rust diseases in self pollinating cereals. Euphytica 27:529-540. Johnson, R. 1988. Durable resistance to yellow (stripe) rust in wheat and its implications in plant breeding. In: N.W. Simmonds and S. Rajaram (eds.) Breeding Strategies for Resistance to the Rusts of Wheat. Mexico, D.F.: CIMMYT. pp. 63-75. McIntosh, R.A. 1992. Close genetic linkage of genes conferring adult-plant resistance to leaf rust and stripe rust in wheat. Plant Pathol. 41:523-527. McIntosh, R.A., G.E. Hart, K.M. Devos, M.D. Gale, and W.J. Rogers. 1998. Catalogue of gene symbols for wheat. A.E. Slinkard (ed.). Proc. 9 th Int. Wheat Genetics Symp., 2-7 Aug. 1998, Saskatoon, Canada. Vol 5:1-235. Peterson, R.F., A.B. Campbell, and A.E. Hannah. 1948. A diagrammatic scale for estimating rust intensity of leaves and stem of cereals. Can. J. Res. Sect. C. 26:496-500. Roelfs, A.P., R.P. Singh, and E.E. Saari. 1992. Rust diseases of wheat: Concepts and methods of disease management. Mexico, D.F.: CIMMYT. 81 pp. Rajaram, S., R.P. Singh, and E. Torres. 1988. Current CIMMYT approaches in breeding wheat for rust resistance. In: N.W. Simmonds and S. Rajaram (eds.). Breeding Strategies for Resistance to the Rusts of Wheat. Mexico, D.F.: CIMMYT. pp. 101-118. Singh, R.P. 1992. Genetic association of leaf rust resistance gene Lr34 with adult plant resistance to stripe rust in bread wheat. Phytopathology 82:835-838. Singh, R.P., and S. Rajaram. 1994. Genetics of adult plant resistance to stripe rust in ten spring bread wheats. Euphytica:72:1-7. Singh, R.P., J. Huerta-Espino, and S. Rajaram. 2000a. Achieving near-immunity to leaf and stripe rusts in wheat by combining slow rusting resistance genes. Acta Phytopathlogica Hungarica 35:133-139. Singh, R.P., J.C. Nelson, and M.E. Sorrells. 2000b. Mapping Yr28 and other genes for resistance to stripe rust in wheat. Crop Sci. 40:1148-1155. 48
Applying Physiological Strategies to Wheat Breeding M.P. Reynolds, B. Skovmand, R.M. Trethowan, R.P. Singh, and M. van Ginkel Physiological Basis of Improved Yield and Biomass Associated with the Lr19 Translocation from Agropyron elongatum Although wheat yields have continued to improve over the last 30 years (Calderini et al., 1999), the physiological and genetic bases for this improvement are only partially understood (Reynolds et al., 1999). Nonetheless, yield increases in several backgrounds have been shown to be associated with introgression of a chromosome segment containing Lr19, namely Agropyron 7DL.7Ag (Rajaram, Singh, and Montoya, unpublished data). The introgression of Lr19 has also been reported to be associated with increased biomass (Singh et al., 1998). As yield improvements due to increased partitioning of biomass to grain yield reaches its theoretical limit (Austin et al., 1980), breeding for larger total biomass becomes increasingly necessary if further genetic gains in yield potential are to be realized. Higher biomass may be achieved by: 1) increased interception of radiation by the crop; 2) greater intrinsic radiation use efficiency (RUE) throughout the crop cycle, and 3) improved source-sink balance permitting higher sink demand and, therefore, higher RUE during grainfilling. Increased light interception could be achieved via early ground cover or improved “stay-green” at the end of the cycle. Improved RUE may be achieved, for example, by decreasing photorespiration or photoinhibtion (Loomis and Amthor, 1999), or through improved canopy photosynthesis related to factors such as canopy architecture. Better source-sink balance may result from increased partitioning of assimilates during spike development so that grain number is increased; this improves RUE during grainfilling as a consequence of increased demand for assimilates. Experiments were conducted to determine which of these mechanisms were associated with greater biomass in near-isogenic lines for the Lr19 gene complex (Table 1) bred as described by Singh et al. (1998) and grown under optimal conditions in Ciudad Obregon, northwestern Mexico, for two cycles between 1998-2000. Results Biomass, yield and yield components. Gene Lr19 was associated with increased yield, above-ground biomass, and grain number in most backgrounds. Averaged over both cycles, the main effect of Lr19 was a 10%, 8% , and 13% increase in yield, biomass, and grain number, respectively, with the latter coming mostly via increased numbers of grains per Table 1. Biomass, yield and yield components for Lr19 isolines in spring wheat backgrounds, averaged over two cycles, Ciudad Obregon, Sonora, Mexico, 1998-2000. Biomass Yield No. grains Grains/ Kernel (g/m 2 ) (g/m 2 ) (per m 2 ) spike wt (mg) Main effect Lr19 1,560 670 17,700 44.4 38.3 Control 1,440 610 15,600 39.9 39.4 P level 0.001 0.001 0.001 0.001 0.05 Background Lr19 Angostura + 1,575 630 15,500 37.9 40.9 Angostura - 1,435 585 13,000 36.0 44.9 Bacanora + 1,495 645 18,700 50.5 34.4 Bacanora - 1,525 620 17,500 43.0 35.6 Borlaug + 1,720 755 19,900 48.5 38.2 Borlaug - 1,520 630 17,300 37.9 36.5 Star + 1,630 690 18,500 43.9 37.2 Star - 1,590 640 17,400 39.7 37.0 Seri + 1,600 675 18,400 47.4 36.6 Seri - 1,420 630 16,000 45.3 39.6 Oasis + 1,350 655 15,300 38.4 42.6 Yecora - 1,180 545 12,700 37.5 42.9 P level (interaction) 0.05 0.05 ns ns 0.1 49
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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 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 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
Page 72 and 73: In 1992-93 the CIMMYT office in Tur
Page 74 and 75: In addition to shuttle breeding sev
Page 76 and 77: the CIMMYT wheat breeding program.
Page 78 and 79: Five participants thought the level
Page 80 and 81: 35. Skovmand, B.; López C., C.; S
Page 82 and 83: 94. Tanner, D.G. 1999. Principles a
Page 84 and 85: 182. Díaz de León, J.L.; Escoppin
Page 86 and 87: 258. Mujeeb-Kazi, A.; Delgado, R.;
Page 88: CIMMYT-Derived Bread Wheat, Durum W
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Research Highlights of the CIMMYT Wheat Program 1999-2000

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