Genetic Dissection of the Powdery Mildew Resistance in a Cultivated Emmer Wheat Accession

Blumeria graminis f. sp. tritici (Bgt), the causal agent of wheat powdery mildew, poses a significant threat to global wheat production. In this study, we identified and characterized a broad-spectrum powdery mildew resistance gene, PmL709, in a resistant cultivated emmer wheat (Triticum dicoccum) accession: L709. Using bulked segregant RNA sequencing (BSR-Seq) analysis and molecular markers, PmL709 was mapped to a 1.7 cM interval on chromosome arm 2BS, flanked by markers Xdw05/YTU95-04/YTU95-06/YTU95-08/Xdw10/Xdw11 and YTU692B-094, corresponding to a 21.82–25.94 Mb physical interval (cv. Svevo), using the segregated population crossed by L709 and a susceptible durum wheat cultivar, Langdon. Referring to the origin, the resistance spectra, and the physical position with known resistance genes on chromosome arm 2BS, PmL709 was likely to be an allele of Pm68. Transcriptomic analysis revealed 3923 differentially expressed genes (DEGs) between resistant and susceptible bulks, enriched in pathways such as phenylpropanoid biosynthesis, MAPK signaling, and plant–pathogen interactions. qRT-PCR validated the differential expression of nine candidate genes within the PmL709 interval, highlighting their potential roles in disease resistance. The flanking markers could accurately trace the presence of PmL709 from resistant accession L709 in a survey of 46 susceptible wheat accessions. These findings provide valuable insights into the genetic and molecular mechanisms of powdery mildew resistance in wheat and offer practical tools for marker-assisted breeding to develop resistant cultivars.