Genetic architecture of wheat stripe rust resistance revealed by combining QTL mapping using SNP-based genetic maps and bulked segregant analysis.

A major stripe rust resistance QTL was mapped to a 0.4 centimorgan (cM) genetic region on the long arm of chromosome 7B, using combined genome-wide linkage mapping and bulk segregant analysis. The German winter wheat cv. Centrum has displayed high levels of adult plant stripe rust resistance (APR) in field environments for many years. Here, we used the combined genome-wide linkage mapping and pool-extreme genotyping to characterize the APR resistance. One hundred and fifty-one F recombinant inbred lines derived from a cross between susceptible landrace Mingxian 169 and Centrum were evaluated for stripe rust resistance in multiple environments and genotyped by the wheat 35K single nucleotide polymorphism (SNP) array. Three stable quantitative trait loci (QTL) were identified using QTL analysis across five field environments. To saturate the major QTL, the wheat 660K SNP array was also used to genotype bulked extremes. A major QTL named QYrcen.nwafu-7BL from Centrum was mapped in a 0.4 cM genetic interval flanking by AX-94556751 and AX-110366788 across a 2 Mb physical genomic region, explaining 19.39-42.81% of the total phenotypic variation. It is likely a previously uncharacterized QTL based on pedigree analysis, reaction response, genotyping data and map comparison. The SNP markers closely linked with QYrcen.nwafu-7BL were converted to KASP markers and validated in a subset of 120 wheat lines. A 211 F breeding population from a cross of an elite cultivar Xinong 979 with Centrum were developed for marker-based selection. Three selected lines with desirable agronomic traits and the positive alleles of both KASP markers showed acceptable resistance which should be used as resistance donors in wheat breeding programs. The other QTL QYrcen.nwafu-1AL and QYrcen.nwafu-4AL with additive effects could enhance the level of resistance conferred by QYrcen.nwafu-7BL.