Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 11, 2011
Publication Date: N/A
Interpretive Summary: The fungal disease, stripe rust of wheat has become more prevalent in the eastern U.S. since 2000. Cooperative research between USDA-ARS in Raleigh and the University of Arkansas became in 2005 to identify new sources of resistance. New sources of resistance were identified that are more effective in the plants as the plants mature. This type of resistance is more desirable than resistance expressed at the seedling stage because the mature-plant resistance will potentially be effective against many races of the pathogen. Although most of the new sources of resistance were effective against many races of the pathogen, a few of the sources expressed specificity to some races and not to others. This may limit the usefulness of the more race-specific, mature plant resistances.
Technical Abstract: Stripe rust, caused by Puccinia striiformis f. sp. tritici, has been an important disease of 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 warmer temperatures than the old strain, and overcame the widely used resistance gene, Yr9. Host resistance is the most effective approach to manage stripe rust. 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 all-stage resistance and adult-plant resistance (APR) to stripe rust in a representative group of contemporary winter wheat cultivars and breeding lines and to assess diversity and durability of resistance genes. Of 50 lines evaluated for all-stage resistance, seven had resistance gene Yr17 that confers resistance to the new strain, but this resistance was difficult to identify in the seedling stage. Of 19 lines evaluated for APR, eight had race-specific APR to the new strain, and ten 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. Based on tests for molecular markers, 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 even though some of the lines were positive for one of the markers. 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.