A new diagnostic SSR marker for selection of the Rym4/Rym5 locus in barley breeding.

Genomic sequence AY661558, representing a part of the BAC contig of the Rym4/Rym5 locus conferring resistance to the barley yellow mosaic virus complex (BaMMV/BaYMV), was exploited in order to develop SSR markers for practical barley breeding. Out of 57 SSR motifs found within this sequence, primers were designed and tested for the 5 SSRs with the highest repeat length. The polymorphic SSR marker QLB1 co-segregated with rym4 and rym5 phenotypes in respective high-resolution mapping populations developed for the construction of the original BAC contig. The primers targeted 2 sites located 756 bp and 5173 bp downstream of the translation initiation factor 4E (Hv-eIF4E). Physical linkage of the QLB1 marker to the Rym4/Rym5 locus was confirmed experimentally on Morex BAC 519J14, a seed BAC of Hv-eIF4E, and BAC 801A11, which is located proximally to Hv-eIF4E. QLB1 revealed 7 alleles in a set of 100 winter barley lines and cultivars. Five alleles were found within 673 advanced breeding lines derived from applied Polish winter barley breeding programmes, which corresponds to a PIC value of 0.684. No recombinants between Rym4/5 and QLB1 were detected, suggesting that QLB1 can be used efficiently in marker-assisted selection of the Hv-eIF4E-mediated bymovirus resistance.