Mendelization and Molecular Mapping of a Large-effect QTL Conferring Durable Adult-plant Resistance to Stripe Rust in a Chinese Wheat Landrace ‘Gaoxianguangtoumai’

Abstract The Chinese wheat landrace ‘Gaoxianguangtoumai’ (GX) has exhibited a high degree of adult-plant resistance (APR) to stripe rust in field environments for more than a decade. To reveal the genetic basis for APR to stripe rust in GX, a set of 249 F6:8 recombinant inbred lines (RILs) was developed from a cross between GX and the susceptible cultivar ‘Taichung 29’. The parents and RILs were evaluated for disease severity at the adult-plant stage in field environments by artificial inoculation with the currently predominant Chinese Puccinia striiformis f. sp. tritici races during three cropping seasons, and genotyped using the Wheat 55K single-nucleotide polymorphism (SNP) array to construct a genetic map with 1,871 SNP markers. Two stable APR quantitative trait loci (QTL), QYr.GX-2AS and QYr.GX-7DS from GX, were detected on chromosomes 2AS and 7DS, which explained 15.5–27.0% and 9.6–15.6% of the total phenotypic variation, respectively. Compared with published genes and QTL, QYr.GX-7DS is likely Yr18, whereas QYr.GX-2AS is probably novel. Haplotype analysis revealed that QYr.GX-2AS is likely to be rare which present in 5.3% of the 325 surveyed Chinese wheat landraces. By analyzing a near-isogenic line population, QYr.GX-2AS was further mapped to an interval with a physical distance of about 1.37 Mb and co-segregated with a Kompetitive allele-specific PCR (KASP) marker. Furthermore, three tightly linked KASP markers were highly polymorphic among 109 Chinese wheat cultivars. The short physical interval and tightly linked KASP markers developed in this study will facilitate marker-assisted selection and map-based cloning of QYr.GX-2AS.