IDENTIFICATION OF RAPD MARKERS LINKED TO A RHYNCHOSPORIUM-SECALIS RESISTANCE LOCUS IN BARLEY USING NEAR-ISOGENIC LINES AND BULKED SEGREGANTANALYSIS

Three hundred random sequence 10-mer primers were used to screen a pai r of near-isogenic lines of barley and their donor parent for markers linked to genes conferring resistance to Rhynchosporium secalis. One p rimer was identified which reproducibly generated a product, SC10-65-H 400, from the donor parent and the Rhynchosporium-resistant near-isoge nic line but not from the recurrent parent. Segregation analysis on a barley doubled haploid population and examination of a further three n ear-isogenic lines, their donor and recurrent parents confirmed that t his marker was linked to the Rhynchosporium resistance locus (Rh) on c hromosome 3L. The presence or absence of SC10-65-H400 was subsequently used along with the resistance phenotype to identify two groups of in dividuals in the doubled haploid population which possessed alternativ e alleles at both loci and defined a genetic interval between these tw o markers. Based on that information two bulked DNA samples were const ructed by combining equal amounts of DNA from five individuals from ea ch group. The two bulks and doubled haploid parental lines were screen ed with 700 1 0-mer primers. Seven products were identified which were present in the 'resistant' bulk and parent and were absent in the sus ceptible samples. Segregation analysis established their association w ith Rh. In addition co-segregation of the linked markers with a set of chromosome arm specific RFLPs confirmed the location of the Rh locus on the long arm of barley chromosome 3.