Molecular mapping of genes conferring resistance to soil-borne viruses in barley - an approach to promote understanding of host-pathogen interactions

The genetic fine structure of the rym5 locus was studied in a progeny consi sting of 391 doubled haploid lines which were evaluated for resistance to t wo strains of Barley yellow mosaic virus (BaYMV-1, 2) and to Barley mild mo saic virus (BaMMV). The lack of recombinants concerning the reaction to the different bymoviruses provided evidence that rym5 is a complex locus, whic h is either composed of a series of closely linked genes or comprises a sin gle gene being a member of an allelic series. While the presence of the rym 5 gene(s) leads to complete immunity, a novel gene, termed rmm7 conferring partial resistance to BaMMV was mapped in the proximal region of chromosome 1H.