Abstract
Wheat cultivars Druchamp and Stephens have durable, non-race-specific, high-temperature, adult-plant (HTAP) resistance to Puccinia striiformis, as well as race-specific resistance expressed in both seedling and adult plants. Cultivar Paha has only race-specific seedling resistance. Cultivar Michigan Amber is susceptible to all known North American races of P. striiformis. To determine the gene number and heritability of HTAP resistance and the relationship of HTAP resistance to seedling resistance, diallel, reciprocal crosses were made among Druchamp, Stephens, and Paha or Michigan Amber in a greenhouse. Parents and F 1 , F 2 , B 1 , B 2 . F 3 , and F 5 progeny from all crosses were tested at Pullman, WA, in a plot inoculated with race CDL-25. The same progeny from the crosses of Druchamp and Stephens with Paha were tested at Pullman in a plot inoculated with race CDL-29, and progeny from the crosses of Druchamp with Stephens were tested with naturally occurring race CDL-25 at Mount Vernon, WA. Means and variances of area under disease progress curve based on disease intensity data were used to estimate the number of genes and the heritability of resistance in Stephens and Druchamp. IT data also were analyzed to determine the number of genes in the cultivars. Two to three HTAP resistance genes were estimated for both Druchamp and Stephens. The HTAP resistance genes in Druchamp and Stephens were different from one another and different from the race-specific resistance genes in Druchamp, Stephens, and Paha. The HTAP resistances showed no specificity for races CDL-25 and CDL-29. Estimated broad-and narrow-sense heritabilities of the HTAP resistance were high. Broad-sense heritability was 96.8 % for Druchamp and 95.3 % for Stephens, Narrow-sense heritability was 86.1-89.1 % for Druchamp and 95.4 % for Stephens. When HTAP resistance and seedling resistance were combined, estimated broad-sense heritabilities remained high (85.2-98.7 %), but estimated narrow-sense heritabilities became low and variable (19.8-60.2) depending on the combination of genes. HTAP genes in both Druchamp and Stephens provided high adult-plant resistance over a range of environmentalconditions. Combining these genes for resistance into new commercial cultivars should provide greater stripe rust resistance
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