R. L. Villareal

Agronomic performance of chromosomes 1B and T1BL.1RS near-isolines in the spring bread wheat Seri M82

The T1BL.1RS wheat (Triticum aestivum L.) - rye (Secale cereale L.) translocations have been of particular interest and are widely used in bread wheat breeding programs. The objective of this study was to determine the effect of the T1BL.1RS chromosome on grain yield and its components using 20 near-isolines of spring bread wheat cultivar ‘Seri M82’ (10 homozygous for chromosome 1B substitution and 10 homozygous for T1BL.1RS). The test lines have been produced by substituting the 1B chromosome in Seri M82 (T1BL.1RS, T1BL.1RS) through backrossing. Two field experiments were evaluated under optimum (five irrigations) and reduced (one irrigation) moisture conditions for two consecutive production cycles at the Mexican National Agricultural Research Institute, Ciudad Obregon, Sonora, Mexico. The presence of T1BL.1RS had a significant effect on grain yield, harvest index, grains/m2, grains/spike, 1000-grain weight, test weight, flowering date and physiological maturity in both moisture conditions. The agronomic advantage of the 1B substitution lines on above-ground biomass yield at maturity, spikes/m2and grain-filling duration was expressed only under the optimum moisture condition. The presence of T1BL.1RS increased grain yield 1.6% and 11.3% for optimum and reduced moisture conditions, respectively. These results encourage further use of T1BL.1RS wheats in improving agronomic traits, especially for reduced irrigation or rainfed environments.

Yield loss to spot blotch in spring bread wheat in warm nontraditional wheat production areas

Twenty-five spring bread wheat (Triticum aestivum L.) cultivars were evaluated for 2 years at Poza Rica, Mexico, for grain yield, aboveground biomass at maturity, harvest index, yield components, and test weight under a natural epidemic of spot blotch (caused by Cochliobolus sativus) with and without fungicide protection. Diseased plot yields were 43.2% lower than fungicide-protected plot yields. Aboveground biomass yield at maturity and harvest index were reduced by 18 and 31.3%, respectively, on blotched plots. The average percent reduction on primary yield components due to the disease was highest for number of grains per m 2 (32.8%), followed by 1,000-grain weight (30.5%), number of grains per spike (24.6%), and number of spikes per m 2 (12%). Test weight was reduced 8.4%. Resistance to Cochliobolus sativus present in cultivars with resistance from Thinopyrum curvifolium or materials derived from Chinese germ plasm increased grain yield. This germ plasm may be a valuable source of genes for spot blotch resistance in T. aestivum.

The effect of chromosome 1AL/1RS translocation on agronomic performance of 85 F2-derived F6 lines from three Triticum aestivum L. crosses

SummaryThe effect of the 1AL/1RS chromosome translocation on grain yield and other agronomic characteristics of 85 random F2-derived F6 bulks from three 1AL 1RS × 1A bread wheat crosses was determined under optimum and reduced irrigation conditions at CIANO, Yaqui Valley, Sonora, Mexico, during the 1991–1992 and 1992–1993 crop production cycles. Harvest plots of 5.0 m2 were arranged in an alpha lattice design with three replications. The 1AL/1RS translocation increased grain yield, above-ground biomass, spikes/m2, and test weight under both irrigated and dryland conditions. Homozygous chromosome 1A lines, on the other hand, possessed longer spikes with more grains. The 1AL/1RS cultivars had an advantage in 1000-grain weight, which was detected only under optimum irrigation. The translocation lines showed later maturity and longer grainfilling period than the 1A genotypes under one irrigation treatment. A significant relationship between grain yield and test weight was detected only among the 1AL/1RS genotypes, indicating that they possess heavier and plumper grains than the 1A genotypes. These results encourage the continued use of the 1AL/1RS translocation in wheat improvement.

The Contribution of Rye Germplasm Towards Cereal Improvement

Alien introgression methodologies have elucidated the usage of distantly or closely related species through intergeneric and interspecific hybridization strategies. Of the various annual and perennial Triticeae species, Secale cereale (2n=2x=14, RR) is one that expresses a well demonstrated potential for cereal improvement with over five million hectares being cultivated to the rye translocation wheats possessing the 1AL/1RS or 1BL/1RS chromosome translocations. We now attribute a 4.3 percent yield advantage to the 1BL/1RS translocation as observed for present analyses of random F2-derived F6 lines emerging from the Triticum aestivum cvs. Nacozari/Seri 82 combination. Stringent evaluation of the contribution of 1BIJ1RS translocation is anticipated from yield analyses of bread wheat (Seri 82, 1BL/1RS) and dumm wheat (Altar 84, 1B) germplasm in which chromosomes 1B or 1BL/1RS respectively have been substituted by eight backcrosses. We have initially inferred that the adverse bread-making quality is not an exclusive function of the 1BL/1RS translocation. The evaluation of the critical genetic substitution stocks produced by backcrossing to Seri 82 will shed further light upon the contribution of 1BL/1RS translocation towards bread making. Additional utilization of rye comes from germplasm exhibiting improved copper efficiency (5AS/5RL or 4BL/5RL), cereal cyst nematode (6BS/6RL) and Karnal bunt resistance (disomic additions 4R and 6R). Transfers and introgressions from these rye sources are being made into some CIMMYT spring wheats. Advanced derivatives from triticale x T aestivum; with a translocation homozygote; are a source of Septoria tritici resistance. Detection of rye presence has utilized fluorescent in situ hybridization (FISH) as a diagnostic.