Characterization of three quantitative trait loci conferring robust resistance to wheat yellow mosaic virus in the wheat cultivar Shunyou.

Key message: Three QTLs for resistance to WYMV were mapped, and the effects of each QTL on three pathotypes were evaluated. The KASP markers identified different origins of these QTLs. Wheat yellow mosaic virus (WYMV) is a soil-borne pathogen, which hampers wheat production in Japan. WYMV is classified into three pathotypes (I-III), with different geographical distributions in Japan. Breeding wheat lines that are resistant to all three pathotypes is crucial for developing broadly adapted cultivars. To elucidate the genetic basis of resistance against WYMV pathotypes I-III, doubled haploid (DH) lines derived from a susceptible cultivar Kitahonami and a resistant cultivar Shunyou that exhibit resistance to all pathotypes were analyzed. Quantitative trait locus (QTL) analysis using phenotypic data from nursery fields, where pathotype I predominates, identified three resistance QTLs, QYm.naro-2A, QYm.naro-6D, and QYm.naro-7A, located on chromosome arms 2AL, 6DL, and 7AS, respectively. Shunyou and DH lines carrying all three QTLs exhibited robust resistance to all pathotypes, whereas partial resistance was observed with one or two QTLs. To facilitate the utilization of these QTLs in breeding programs, three Kompetitive allele-specific PCR (KASP) markers were developed for each QTL. Pedigree analysis of Shunyou suggested that the resistant allele on 2AL originated from domestic parental cultivars, while those on 6DL and 7AS were introduced from foreign cultivars. These KASP markers may be valuable tools for marker-assisted selection, offering the potential to develop wheat cultivars with durable and broad-spectrum resistance to WYMV.