QTL analysis of durable stripe rust resistance in the North American winter wheat cultivar Skiles.

KEY MESSAGE: This study determined the effects of growth stage and temperature on expression of high-temperature adult-plant resistance to stripe rust, mapped six QTL for durable resistance in winter wheat Skiles using a doubled haploid population, and selected breeding lines with different combinations of the QTL using marker-assisted selection. The winter wheat cultivar Skiles has a high level of high-temperature adult-plant (HTAP) resistance to stripe rust caused by Puccinia striiformis f. sp. tritici (Pst). The Skiles HTAP resistance was highly effective at the adult-plant stage even under low temperatures, but high temperatures induced earlier expression and increased levels of resistance. To map resistance genes, Skiles was crossed with the susceptible cultivar Avocet S and a doubled haploid (DH) population was developed. The DH population was tested in fields at Pullman, WA, in 2016, 2017 and 2018, Mount Vernon, WA, in 2017 and 2018 under natural infection, and an environmentally controlled greenhouse at the adult-plant stage with the currently predominant race PSTv-37. The population was genotyped using the 90 K Illumina iSelect wheat SNP chip and selected SSR markers on specific chromosomes. In total, 2526 polymorphic markers were used for QTL mapping and six QTL were detected. Two of the six QTL had major effects across all environments, with one mapped on chromosome 3BS, explaining up to 28.2% of the phenotypic variation and the other on chromosome 4BL, explaining up to 41.8%. Minor QTL were mapped on chromosomes 1BL, 5AL, 6B and 7DL. Genotyping 140 wheat cultivars from the US Pacific Northwest revealed high polymorphism of markers for five of the QTL, and five highly resistant lines with the five QTL were selected from Skiles-derived breeding lines using the markers. This study demonstrated that multiple QTL with mostly additive effects contributed to the high-level HTAP resistance in Skiles.