Identification, by selective genotyping, of quantitative trait loci conferring resistance to Cochliobolus sativus in barley line TR 251

Spot blotch, caused by Cochliobolus sativus, is one of the most damaging foliar diseases of barley around the world. Although chemical control of plant diseases is an effective tool to reduce pathogen damage, the most efficient and environmentally sound means of spot blotch control is through the deployment of resistant cultivars. The aim of this study was to elucidate the genetic basis of spot blotch resistance in barley line TR 251, a Canadian breeding line with a high level of spot blotch resistance. Infection responses induced by C. sativus isolate WRS1938 in 226 doubled haploid lines derived from the cross TR 251 × CDC Bold were analyzed, and DNA samples from the parents and bulks of 11 resistance and 11 susceptible lines were tested using bulked segregant analysis (BSA) with 376 SSR markers and 256 combinations of amplified fragment length polymorphism (AFLP) markers. Identification of the quantitative trait loci (QTL)-linked markers was done using a selective genotyping approach by both binomial distribution and hypergeometric distribution tests. Four putative loci on chromosomes 1H, 3H, 5H, and 7H were found to be associated with spot blotch resistance in line TR 251 of these, the two loci located on chromosomes 1H and 5H had not been reported in previous studies. Both of these loci are likely unique and presumably contribute to the superior C. sativus resistance of line TR 251.