Molecular Mapping Of Yr8 For All-Stage Resistance And A Gene For HTAP Resistance To Stripe Rust In The AVS/Yr8 Wheat Line

Wheat stripe rust, caused by Puccinia stiiformis f. sp. tritici, is one of the most destructive diseases on what in the world. It is a typical obligate and air-borne fungal disease. In the United States, the disease has been one of the most serious diseases of wheat in the Pacific Northwest regions since 1950's, and also has become a major threat in the Great Plains and southeastern states in the recent years. The utilization of resistance cultivars is the most effective, low-cost, and environmentally-friendly approaches to control stripe rust.In this study, a mapping population of 116 BC7:F3 lines from the cross of'Avocet Susceptible'(AvS) and Compair was used to identify and map the gene(s) for HTAP resistance and Yr8. The population was phenotyped with U.S. Pst races PST-43 and PST-45 (avirulent to Yr8) in the seedling stage under greenhouse conditions and with natural infection of the Pst population (virulent to Yr8) at adult-plant stages at two field locations during the 2006 growth season. Infection type and disease severity were recroded three times at boot stage, flowering stage, and milk stage, which were calculated relative area under disease progress curve. The resistance gene analog polymorphism (RGAP) and simple sequence repeat (SSR) techniques were used to identify molecular markers linked to the loci of Yr8 and the HTAP resistance gene(s). The complete set of Chinese Spring (CS) nulli-tetrasomic lines were used to localize RGAP markers to a wheat chromosome. Two flanking markers for Yr8 and HTAP resistance gene were used to test 44 spring and winter wheat genotypes. The results are as follows:1. We confirmed that the Yr8 near-isogenic line (NIL) and the Yr8 donor,'Compair', have both all-stage resistance controlled by a single dominant gene, and high-temperature, adult-plant (HTAP) resistance conferred by a single gene against stripe rust based on the genetic analyze of the BC7:F3 mapping population.2. 29 RGAP markers and 5 SSR markers were screened and identified to link with the resistance loci of Yr8 and HTAP resistance gene. A genetic linkage and QTL mapping were constructed based on these markers.3. One gene was identified to confer HTAP resistance and the gene was tightly linked (1.3 cM) with Yr8 on the short arm of chromosome 2D. 4. The HTAP resistance gene was identified to be different from Yr16 and Yr18, we designated it as Yr46.5. Yr46 contributed to 29.9% to 58.6% of the total variation of the area under disease progress cure data and 9.9% to 27.3% of the total variation of the infection type data.6. Testing 44 spring and winter wheat genotypes with two flanking markers Xgwp145and Xgwm515 for both genes revealed that only Compair had both markers, indicating that the markers can be used in marker-assisted selection to incorporate both Yr8 and Yr46 into wheat cultivars.