Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/1995
Publication Date: N/A
Citation: Interpretive Summary: Stripe rust of wheat is especially destructive in the western United States. The disease is controlled mainly by resistant cultivars, especially seedling resistance and high-temperature, adult-plant (HTAP) resistance. Seedling resistance is expressed at all stages of plant growth and is race-specific. Varieties with seedling resistance often become susceptible ewithin a few years after their use, because of the evolution of new virulent races of the rust pathogen. HTAP resistance increases as plants become older at higher temperatures but not at low temperatures. HTAP resistance is non-race-specific and durable. The winter wheat varieties Stephens and Druchamp have both types of resistance. To determine the number and heritability of the HTAP resistance genes and the relationship of those genes to seedling resistance genes, Stephens and Druchamp were crossed with each other and with Michigan Amber (a susceptible variety) and dPaha (a seedling-resistant club wheat). Two to three HTAP resistance gene were determined for Druchamp and Stephens. The HTAP resistance genes in Druchamp and Stephens were different from one another and from the seedling resistance genes in Druchamp, Stephens and Paha. HTAP resistances showed no specificity for stripe rust races. Estimated broad-sense and narrow sense heritabilities of the HTAP resistance were high. HTAP resistance genes in both Druchamp and Stephens provided high adult-plant resistance at a range of environmental conditions. It is possible to combine the HTAP genes from Stephens and Druchamp to develop commercial cultivars with greater resistance.
Technical Abstract: Stephens and Druchamp have both race-specific seeding resistance and non race specific high-temperature, adult-plant (HTAP) resistance to Puccinia striiformis. Reciprocal, diallel crosses were made between Stephens and Druchamp and of Stephens and Druchamp with Paha (a seedling-resistant club wheat) or Michigan Amber (a susceptible wheat). Parents and F1, backcrosses, F2, F3, and F5 progeny were evaluated for resistance in the fields using stripe rust intensity (severity) data transformed to area under disease progress curve (AUDPC). Generation means and variances were used to determine gene number and heritability. Infection type data were also used to determine gene number. 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 seedling resistance genes in Druchamp, Stephens and Paha. .The HTAP resistances showed no specificity to races CDL-25 and CDL-29. Both broad-sense and narrow-sense heritabilities of 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 and seedling resistances were combined, broad sense heritabilities were high and consistent (85.2-98.7%), but narrow sense heritabilities were low and variable (19.8-60.2%) depending upon the combinations. HTAP resistance genes in both Druchamp and Stephens provided high adult-plant resistance at a range of environmental conditions.