Identification and characterization of the powdery mildew resistance in cultivated emmer wheat accession Lxd-682 via bulked segregant RNA sequencing.

BACKGROUND

Common wheat (Triticum aestivum L.) is a vital source of nutrition for human consumption. However, wheat production is significantly threatened by various diseases, such as powdery mildew, a widespread fungal disease caused by Blumeria graminis f. sp. tritici (Bgt). Utilizing and identifying resistance genes and elucidating the molecular mechanisms underlying this resistance are the most effective and sustainable ways to fight this disease.

RESULTS

Lxd-682, a cultivated emmer wheat accession, exhibited resistance to 12 out of 13 tested Bgt isolates at the seedling stage. Genetic analysis revealed that this resistance is conferred by a single dominant gene, tentatively designated as PmLxd-682. Molecular mapping positioned PmLxd-682 between the markers WGRE77413 and WGRC1096, with the Pm4-diagnostic marker JS717/JS718 co-segregating. Homology-based cloning and sequence alignment further confirmed that PmLxd-682 is identical to Pm4a. qRT-PCR analysis showed that the alternative splicing PmLxd-682-V2 exhibited higher expression level than that of PmLxd-682-V1 post-Bgt invasion, suggesting its prominent role in fighting Bgt invasion. Additionally, four pathogenesis-related (PR) genes were significantly up-regulated in both Lxd-682 and susceptible parent Langdon upon infection, revealing possibly unimportant roles in resistance pathway. Furthermore, 1,567 differentially expressed genes (DEGs) between resistant and susceptible bulks were identified through BSR-Seq, with 490 ones located within the candidate interval on chromosome 2AL, and potential biological processes associated with resistance were enriched via gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) pathway analysis. To verify the potential regulatory genes, three key genes, TRITD2 Av1G294940, TRITD2 Av1G036490 and TRITD2 Av1G295220 all encoding disease resistance protein, were selected from six candidates via qRT-PCR following post-Bgt invasion. Molecular markers JS717/JS718 and WGRC1096 were confirmed to be available for marker-assisted selection (MAS) of PmLxd-682 in breeding practices.

CONCLUSIONS

The study identified key genetic intervals and genes involved in the resistance of a cultivated emmer wheat accession Lxd-682 to powdery mildew. These findings significantly advance our understanding of plant-pathogen interactions and establish a solid foundation for future genetic and functional studies aimed at improving disease resistance in crops.