Quantitative Trait Loci Mapping for Powdery Mildew Resistance in Wheat Genetic Population

Powdery mildew is a prevalent wheat disease that affects yield and quality. The characterization and fine mapping of genes associated with powdery mildew resistance can benefit marker-assisted breeding. In this study, quantitative trait loci (QTL) associated with powdery mildew were mapped using a high-density 35K DArT genetic linkage map developed from a population of double haploid lines (DHs) created by crossing "Jinmai 33 (a highly resistance line) with Yannong 19 (a highly susceptible line)". Three stable QTLs for powdery mildew were identified on chromosomes 1B, 2B, and 6A combined with the composite interval graphing method and multiple interval mapping, explaining phenotypic variations (PVE) that range from 4.98% to 13.25%. Notably, <i>Qpm.sxn-1B</i> and <i>Qpm.sxn-2B</i> were identified across three environments, with the PVE ranging from 9.37% to 13.25% and from 4.98% to 5.23%, respectively. The synergistic effects of these QTLs were contributed by the parental line "Jinmai 33". <i>Qpm.sxn-1B</i> was the major stable QTL, and <i>Qpm.sxn-2B</i> was close to <i>Pm51</i>. Furthermore, <i>Qpm.sxn-6A</i> was identified in two environments, accounting for PVE values of 7.13% and 7.65%, respectively, with the resistance effects originating from the male parent. Remarkably, this locus has not been reported previously, indicating that <i>Qpm.sxn-6A</i> represents a newly dis-covered QTL governing powdery mildew genes. Conclusions Five molecular markers available for mark-er-assisted selection were selected for tracking <i>Qpm.sxn-1B</i> and <i>Qpm.sxn-2B</i> in the program. The identification of this novel newly discovered QTL and markers reported in this study will be useful for marker-assisted selection of powdery mildew resistance.