Linkage maps of wheat stripe rust resistance genes yr5 and yr15 for use in marker-assisted selection

Stripe rust (caused by Puccinia striiformis Westend. f. sp. tritici Eriks.) is a serious disease of wheat (Triticum aestivum L.). Resistance genes Yr5 and Yr15 are the only known all-stage resistance genes that defeat all stripe rust races currently found in the United States. Previously mapped markers for these genes, however, show limited polymorphism across diverse genotypes and/or map at a distance from the genes, reducing the effectiveness of marker-assisted selection. Our objective was to create new linkage maps for both genes using sequence tagged site (STS) and simple sequence repeat (SSR) loci and to evaluate closely linked markers across a diverse panel of wheat genotypes. Two recombinant inbred populations created using Avocet-Susceptible as a susceptible parent and Triticum aestivum L. ssp. spelta (L.) Thell. 'Album' and Triticum dicoccoides Koern. as the Yr5 and Yr15 donors, respectively, were evaluated for resistance to multiple races of stripe rust. Molecular markers that had been previously mapped to wheat chromosome 1B (Yr5) or 2B (Yr15) were mapped on the appropriate population. Markers most closely linked to each gene were evaluated against a panel of genotypes collected from active introgression programs in the United States. The Yr5 gene is flanked on the distal side by STS7/8 marker and by Xbarc349 and Xbarc167 on the proximal side, although none of these markers were diagnostic in all backgrounds. For Yr15, Xbarc8 and Xgwm413 appear to be completely linked with the gene in our population, along with resistance gene analog polymorphism marker Xwgp34. These two SSR markers also appear to be diagnostic in all backgrounds tested with one exception (Zak). We have developed linkage maps for both genes and identified several useful SSR and STS markers for introgression of Yr5 and Yr15.