Gene-based high-density mapping of the gene rym7 conferring resistance to Barley mild mosaic virus (BaMMV)

Abstract

Barley yellow mosaic virus (BaYMV) disease seriously affects winter barley (Hordeum vulgare L.) production. Improvement of resistance to this disease can prevent yield losses. Based on previous reports, the gene rym7 (rmm7), conferring partial resistance to BaMMV, was assigned to chromosome 1H, closely linked to the centromere. In this study, newly developed barley genomic resources were applied to saturate the genetic map at the rym7 locus. Out of a set of 350 gene-based markers of chromosome 1H, we genetically assigned 23 to the rym7 region, delimiting the resistance locus to a 9.9-cM interval close to the centromere by genetic mapping in 53 doubled haploid progeny of a bi-parental mapping population. Nine gene-derived co-dominant markers co-segregated with the resistance locus. Among these, we identified the eukaryotic translation initiation factor Hv-eIF(iso)4E. Its homolog in Arabidopsisthaliana confers resistance to potyviruses. However, sequencing the entire open reading frame of resistant and susceptible genotypes could not reveal any sequence variation in exons of the gene. These results demonstrate how to combine newly developed barley genomic resources for rapid gene-based marker saturation. As a result, several easy-to-handle co-dominant markers have been identified for marker-assisted selection of rym7 in barley breeding.