Specific Loci for Adult-Plant Resistance to Stripe Rust in Wheat Founder Parent Fan 6 and Their Genetic Dissection in Its Derivatives

Fan 6 is one of the most important founder parents of common wheat in China. The objective of this study was to reveal the genetic structure of Fan 6 and the transmission of its specific loci for adult-plant resistance to stripe rust (Puccinia striiformis f. sp. tritici, Pst) in 39 derivatives. The resistance was evluated using 80 SSR markers assocated with the consensus QTLs for adult-plant resistance to Pst and the phenotypic assessment was conducted at seedling and adult stages after mixed inoculation with Pst races CYR31, CYR32, and CYR33. Fan 6 and seven derivatives showed resistance to Pst in the whole growth stage. Nine SSR allelles, Xwmc631, Xgwm359, Xwmc407, Xgwm501, Xgwm148, Xgwm539, Xgwm533, Xgwm299, and Xgwm639, were identified to be specific to Fan 6, of which Xwmc631, Xgwm359, Xgwm501, Xgwm299, and Xgwm639 exhibited high inheritability in the four derivate generations of Fan 6. The result of marker–trait association analysis showed that six SSR loci were significantly correlated with adult-plant resistance to Pst in Fan 6 and its derivatives. Among them, alleles from Fan 6 on loci Xgwm539 and Xgwm299 were responsible for disease severity, infection type, incidence, disease index, and area under the disease progress curve (AUDPC). These results indicated that the slow stripe-rusting resistance in Fan 6 has been intensively selected in breeding programs using Fan 6 as the founder parent, which will play an important role in Southwestern wheat area of China.