Genetically Dissecting the Novel Powdery Mildew Resistance Gene in the Wheat Breeding Line PBDH1607

Powdery mildew is one of the most destructive diseases in wheat production. Identifying novel resistance genes and deploying them in new cultivars is the most effective approach to minimize wheat losses caused by powdery mildew. In this study, a wheat breeding line PBDH1607 showed high resistance to powdery mildew at both seedling and adult-plant stages. Genetic analysis of the seedling data demonstrated that the resistance was controlled by a single dominant gene, tentatively designated PmPBDH. The ΔSNP-index based on bulked segregant RNA-seq (BSR-Seq) indicated that PmPBDH was associated with an ~30.8 Mb (713.5 - 744.3 Mb) interval on chromosome arm 4AL. Using newly developed markers, PmPBDH was mapped to a 3.2 cM interval covering 7.1 Mb (719,055,516 - 726,215,121 bp). This interval differed from those of Pm61 (717,963,176 - 719,260,469 bp), MlIW30 (732,769,506 - 732,790,522 bp), and MlNSF10 (729,275,816 - 731,365,462 bp) reported on the same chromosome arm. PmPBDH also differed from Pm61, MlIW30, and MlNSF10 by its response spectrum, origin and/or inheritance mode, suggesting that PmPBDH should be a new Pm gene. In the candidate interval, five genes were found associated with PmPBDH using time-course gene expression analysis, and thus, they are candidate genes of PmPBDH. Six closely linked markers, including two Kompetitive Allele-Specific PCR markers, were confirmed to be applicable for tracking PmPBDH in marker-assisted breeding.