Genome-Wide Wheat 55K SNP-Based Mapping of Stripe Rust Resistance Loci in Wheat Cultivar Shaannong 33 and Their Alleles Frequencies in Current Chinese Wheat Cultivars and Breeding Lines

Wheat cultivar Shaannong 33 (SN33) has remained highly resistant to stripe rust in the field since its release in 2009. To unravel the genetic architecture of stripe rust resistance, seedlings of 161 recombinant inbred lines (RILs) from the cross Avocet S x SN33 were evaluated with two isolates (PST-Lab.1 and PST-Lab.2) of the stripe rust pathogen (Puccinia striiformis f. sp. tritici) in the greenhouse, and the RILs were evaluated in naturally or artificially inoculated field sites during two cropping seasons. The RILs and parents were genotyped with the wheat 55K single-nucleotide polymorphism array. Three genomic regions conferring seedling resistance were mapped on chromosomes 1DS, 2AS, and 3DS, and four consistent quantitative trait loci (QTL) for adult-plant resistance (APR) were detected on 1BL, 2AS, 3DL, and 6BS. The 2AS locus conferring all-stage resistance was identified as the resistant gene Yr17 located on 2NS translocation. The QTL identified on 1BL and 6BS likely correspond to Yr29 and Yr78, respectively. An APR QTL on 3DL explaining 5.8 to 12.2% of the phenotypic variation is likely to be new. Molecular marker detection assays with the 2NS segment (Yr17), Yr29, Yr78, and QYrsn.n-wafu-3DL on a panel of 420 current Chinese wheat cultivars and breeding lines indicated that these genes were present in 11.4, 7.6, 14.8, and 7.4% of entries, respectively. The interactions among these genes and QTL were additive, suggesting their potential value in enhancing stripe rust resistance breeding materials as observed in the resistant parent. In addition, we also identified two leaf necrosis genes, Ne1 and Ne2; however, the F-1 plants from cross Avocet S x SN33 survived, indicating that SN33 probably has another allele of Ne1 which allows seed to be harvested.