Candidate markers for powdery mildew resistance genes from wild barley PI284752

PI284752, an accession of wild barley (Hordeum vulgare ssp. spontaneum) resistant to powdery mildew caused by Blumeria graminis f.sp. hordei, was studied with the aim of identifying genes involved in powdery mildew resistance. An F₂ population (456 plants) was established from a cross between the winter barley variety ‘Tiffany' and PI284752. This cross demonstrated a two-locus model of resistance. Linkage analysis using polymorphic DNA markers was carried out on 180 plants. The RGH1a gene sequence from the Mla locus was used as a source for developing the RGH1aE2I2 marker. By interval mapping on chromosome 1HS, one resistance gene was found to be tightly linked with RGH1aE2I2 and it was found to be located 2 cM from GBMS062. In F₂ plants exhibiting resistance reaction type (RT) 0, specific DNA fragments for the RGH1aE2I2 marker were amplified. In plants with RT1 to RT2-3, the resistance was conferred exclusively by the second R gene that we identified, which is linked with Bmac0134 and GBMS247 on chromosome 2HS. The aforementioned markers may be valuable candidates for marker-assisted selection of resistant genotypes conferred by one or both genes.