Characterization of resistance to stripe rust in contemporary cultivars and lines of soft red winter wheat.

摘要

Stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici Eriks. & E. Henn., has been an important disease of soft red winter wheat in the eastern United States since 2000 when a new strain of the pathogen emerged. The new strain was more aggressive and better adapted to wanner temperatures than the old strain, and overcame the important resistance gene, Yr9. Host resistance is the most effective approach to manage stripe rust. Two major types of resistance in wheat to stripe rust are all-stage resistance and adult-plant resistance (APR). All-stage resistance is effective at all growth stages but is usually race specific and overcome by new races of pathogen. APR is expressed at post-seedling stages, increases as plants mature, and can be race specific or race nonspecific. APR that requires high temperature to be expressed is known as high-temperature adult-plant resistance. Soft red winter wheat lines with resistance to the new strain are common, but the genes conferring this resistance are mostly unknown. The objectives of this research were to characterize resistance to stripe rust in a representative group of contemporary soft red winter wheat cultivars and breeding lines and to assess diversity and durability of resistance genes. Of 50 lines evaluated for all-stage resistance, only two had resistance to the new strain, and these appear to have the same resistance gene ( Yr17) that has already been overcome by races in Mexico and the western United States. Of 19 lines evaluated for APR, nine had race-specific APR to the new strain, and nine had APR to both old and new strains. The remaining line, 26R61, had all-stage resistance to the old strain and high level of APR to the new strain. APR was expressed in the field, at low and high temperature regimes under controlled conditions, and as early as jointing stage of plants. Based on race specificity and levels of resistance, at least four genes or alleles controlled APR in these lines. APR gene, Yr18, was not present in any of the tested lines, and it is unlikely that APR gene, Yr29, is present in any of the lines. Although the race-specific APR genes were effective against the new strain, they might not be durable. APR genes effective against both strains may provide durable resistance.