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Title: Molecular mapping of genes for race-specific overall resistance to stripe rust in wheat cultivar Express

Author
item LIN, F - WASHINGTON STATE UNIV
item Chen, Xianming

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2007
Publication Date: 3/1/2008
Citation: Lin, F., Chen, X. 2008. Molecular mapping of genes for race-specific overall resistance to stripe rust in wheat cultivar Express. TAG 116:797-806.

Interpretive Summary: Stripe rust is one of the most important diseases on wheat. Effective control of the disease is best through monitoring races and growing resistant cultivars. The Express spring wheat cultivar has been widely grown in the western United States and used to differentiate races of the stripe rust pathogen. However, the genes in the cultivar for stripe rust resistance were unknown. To identify genes conferring race-specific, all-stage (overall) resistance to stripe rust, Express was crossed with ‘Avocet S’ (AVS). The parents and progeny populations were tested with four races of the stripe rust pathogen in the seedling stage under controlled greenhouse conditions. Two dominant genes for resistance to stripe rust were identified, one conferring resistance to two and the other conferring resistance to all four races. Linkage groups were constructed for the resistance genes using 146 recombinant inbred lines to identify molecular markers. The gene for resistance to the two races was mapped on the long arm of chromosome 1B, and that conferring resistance to all four races was mapped on the long arm of chromosome 5B. Polymorphism of at least one of the two markers flanking the gene on 5B was detected in 91% of the 44 tested wheat genotypes, suggesting that they would be useful in marker-assisted selection for combining the gene with other resistance genes into wheat cultivars. Knowledge of these genes will be useful to understand recent virulence changes in the pathogen populations.

Technical Abstract: ‘Express’, a hard red spring wheat cultivar that has been widely grown in the western United States, is used to differentiate races of Puccinia striiformis f. sp. tritici, the causal fungal pathogen of wheat stripe rust. To identify genes conferring race-specific, overall resistance to stripe rust, Express was crossed with ‘Avocet S’ (AVS). The parents and F1, F2, F3 and F5 populations were tested with races PST-1, PST-21, PST-43, and PST-45 of P. striiformis f. sp. tritici in the seedling stage under controlled greenhouse conditions. Two dominant genes for resistance to stripe rust were identified, one conferring resistance to PST-1 and PST-21, and the other conferring resistance to all four races. Linkage groups were constructed for the resistance genes using 146 F5 lines to establish resistance gene analog (RGAP) and chromosome-specific simple sequence repeat (SSR) marker polymorphisms. The gene for resistance to races PST-1 and PST-21 was mapped on the long arm of chromosome 1B, and that conferring resistance to all four races was mapped on the long arm of chromosome 5B. We temporarily designate the gene on 1BL as YrExp1 and the gene on 5BL as YrExp2. Polymorphism of at least one of the two markers flanking YrExp2 was detected in 91% of the 44 tested wheat genotypes, suggesting that they would be useful in marker-assisted selection for combining the gene with other resistance genes into many other wheat cultivars. Knowledge of these genes will be useful to understand recent virulence changes in the pathogen populations.