Genetic Analysis Of The Resistance Genes To Stripe Rust In Three Wheat Germplasms And Molecular Mapping Of The HTAP Resistance Gene Yr62

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a devastating disease of wheatworldwide. Resistance is the best approach to control the disease. High-temperatureadult-plant (HTAP) resistance has proven to provide durable protection against stripe rust, butgenes conferring low-levels of HTAP resistance affected by plant growth stage, temperature,humidity, and the inoculum load, do not provide adequate control. Thus developing cultivarswith high-levels of HTAP resistance is urgently needed. It is proven that combining bothHTAP and all-stage resistance genes can achieve long-lasting protection of cultivars againststripe rust.In a previous study, three Spring wheat germplasm PI192252、PI185285and PI195097were identified to have a good resistance to stripe rust through our germplasm evaluationprogram from2004to2010. PI192252showed a high-level of HTAP resistance, PI185285showed a high-level of all-stage resistance and PI195097showed moderate resistance againststripe rust in our germplasm evaluations over several years. To elucidate the genetic basis ofthe resistance, PI192252, PI185285and PI195097were crossed with ‘Avocet Susceptible’(AvS) respectively. A mapping population of F5recombinant inbred lines (RILs) wasdeveloped using single-seed descent. For the AvS/PI192252RIL population, stripe rust testswere conducted with selected Pst races in a greenhouse using a four-way test approach and infour field experiments (at Pullman and Mount Vernon, WA in2011and2012). For AvS/PI185285RIL and AvS/PI195097RIL populations, stripe rust tests were conducted withselected Pst races in a greenhouse and in two field experiments (at Pullman and MountVernon, WA in201). All of the field experiments conducted under natural infections. Data ofinfection type and disease severity (DS) were recorded for each of the parents and RILs threetimes during each of the stripe rust season, and the severity data were used to calculaterelative area under the disease progress curve (rAUDPC) values. QTLs were detected bycomposite interval mapping (CIM) using the software Win QTL Cartographer2.5bases onrAUDPC values. The results are as follows: 1. Two significant QTL were identified in PI192252, explaining74.2%of the totalphenotypic variation for rAUDPC. These two QTL were mapped to the long arm ofchromosome4B (QYrPI192252.wgp-4B) and the short arm of chromosome5B(QYrPI192252.wgp-5B) and explained40-60and22-27%, respectively, of the phenotypicvariation across the four environments. The major effect QYrPI192252.wgp-4B flanked bySSR marker Xgwm495and SNP marker IWA2171covering a7cM interval containing fourother markers (IWA99, IWA1923, Xgwm251and Xgwm192).2. Because QYrPI192252.wgp-4BL is different from officially named Yr genes, such asYr50, we designated it as Yr62.3. Two SSR markers Xgwm251and Xgwm192which closely linked with Yr62werehighly polymorphic in various wheat genotypes, suggesting that these markers are useful inmarker-assisted selection for incorporating the gene into commercial cultivars.4. The quanlitative genetic study of the AvS/PI195097and AvS/PI185285F5RILspopulation, indicating at least two and three genes for all-stage resistance from PI195097andPI185285respectively.The new gene Yr62and two flanking markers Xgwm251and Xgwm192which have100%polymorphism rates in various wheat genotypes should be useful in developing wheatcultivars with high-level and durable resistance to stripe rust.