Mapping of Yr62 and a small-effect QTL for high-temperature adult-plant resistance to stripe rust in spring wheat PI 192252.

KEY MESSAGE: This manuscript reports a new gene (Yr62) and a small-effect QTL for potentially durable resistance to stripe rust and usefulness of Yr62 markers for marker-assisted selection. Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease of wheat worldwide. Spring wheat germplasm PI 192252 showed a high level of high-temperature adult-plant (HTAP) resistance to stripe rust in germplasm evaluation over 8 years in the State of Washington. To elucidate the genetic basis of resistance, PI 192252 was crossed with 'Avocet susceptible'. A mapping population of 150 F5 recombinant inbred lines was developed using single-seed descent. Stripe rust tests were conducted with selected Pst races in a greenhouse and in field conditions under natural infections. The relative area under the disease progress curve (rAUDPC) data showed continuous distributions, indicating that HTAP resistance of PI 192252 was controlled by quantitative trait loci (QTL). Two QTL were identified in PI 192252, explaining 74.2 % of the total phenotypic variation for rAUDPC. These two QTL were mapped to chromosomes 4BL (QYrPI192252.wgp-4BL) and 5BS (QYrPI192252.wgp-5BS) with SSR and SNP markers and explained 40-60 and 22-27 %, respectively, of the phenotypic variation across the four environments. Because the major-effect QTL on 4BL is different from previously named Yr genes and inherited as a single gene, it is named Yr62. The SSR marker alleles Xgwm192 222 and Xgwm251 133 flanking Yr62 were different from the alleles in various wheat varieties, suggesting that these markers could be useful in marker-assisted selection for incorporating Yr62 into commercial cultivars.