Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a devastating disease that threatens wheat production worldwide. Pm12, which originated from Aegilops speltoides, a wild relative of wheat, confers strong resistance to powdery mildew and therefore has potential use in wheat breeding. Using susceptible mutants induced by gamma irradiation, we physically mapped and isolated Pm12 and showed it to be orthologous to Pm21 from Dasypyrum villosum, also a wild relative of wheat. The resistance function of Pm12 was validated via ethyl methanesulfonate mutagenesis, virus-induced gene silencing, and stable genetic transformation. Evolutionary analysis indicates that the Pm12/Pm21 loci in wheat species are relatively conserved but dynamic. Here, we demonstrated that the two orthologous genes, Pm12 and Pm21, possess differential resistance against the same set of Bgt isolates. Overexpression of the coiled-coil domains of both PM12 and PM21 induces cell death in Nicotiana benthamiana leaves. However, their full-length forms display different cell death-inducing activities caused by their distinct intramolecular interactions. Cloning of Pm12 will facilitate its application in wheat breeding programs. This study also gives new insight into two orthologous resistance genes, Pm12 and Pm21, which show different race specificities and intramolecular interaction patterns.

Powdery mildew infection of wheat (Triticum aestivum L.), caused by Blumeria graminis f. sp. tritici (Bgt), is a destructive disease that threatens yield and quality worldwide. The most effective and preferred means for the control of the disease is to identify broad-spectrum resistance genes for breeding, especially the genes derived from elite cultivars that exhibit desirable agronomic traits. Jimai 23 is a Chinese wheat cultivar with superior agronomic performance, high-quality characteristics, and effective resistance to powdery mildew at all growth stages. Genetic analysis indicated that powdery mildew resistance in Jimai 23 was mediated by a single dominant gene, tentatively designated PmJM23. Using bulked segregant RNA-Seq (BSR-Seq), a series of markers was developed and used to map PmJM23. PmJM23 was then located at the Pm2 locus on the short arm of chromosome 5D (5DS). Resistance spectrum analysis demonstrated that PmJM23 provided a broad resistance spectrum different from that of the documented Pm2 alleles, indicating that PmJM23 is most likely a new allele of Pm2. In view of these combined agronomic, quality, and resistance findings, PmJM23 is expected to be a valuable resistance gene in wheat breeding. To efficiently use PmJM23 in breeding, the closely linked markers of PmJM23 were evaluated and confirmed to be applicable for marker-assisted selection (MAS). Using these markers, a series of resistant breeding lines with high resistance and desirable agronomic performance was selected from the crosses involving PmJM23, resulting in improved powdery mildew resistance of these lines.