Dynamics of resistant genes and their relationship to resistance to wheat yellow mosaic disease in Japanese wheat germplasms.

Wheat yellow mosaic (WYM) disease, caused by the wheat yellow mosaic virus (WYMV), significantly affects wheat production. Three WYMV pathotypes-I, II, and III-have been identified in Japan, each with a distinct geographical distribution and pathogenicity. To investigate the historical and geographical distribution of infection-resistant wheat varieties in Japan and the relevant genetics, we comprehensively evaluated the response to WYMV pathotypes and the genotypes conferring resistance in accessions of the Japanese wheat core collection. In the experimental fields harboring WYMV, most of the varieties that showed stable resistance were breeders lines; only a few were traditional varieties. Resistant accessions are particularly prevalent in northern Japan. These results suggest that resistant varieties have been developed through modern breeding, in which crossbreeding with foreign varieties has played a major role. Resistance-conferring genes on the chromosome 2DL and 5AL appeared to have been introduced during this breeding process, and the 5AL locus became widely distributed in Japanese varieties. Through genome-wide association studies, we identified a novel resistance-conferring locus on chromosome 7AS. Furthermore, the resistant haplotype on 7AS confers robust resistance to pathotype I when combined with the haplotype carried on 5AL. The results of this study contribute to the understanding of resistance-associated genetics in the context of WYM disease, highlighting the potential of particular genomes to confer robust and durable resistance in breeding efforts.