Genetic mapping and QTL analysis of disease resistance traits in the barley population Baudin x AC Metcalfe

Agenetic map of barley (Hordeum vulgare L.) with 163 amplified fragment length polymorphism and 69 simple sequence repeat (SSR) markers was constructed using a population of 178 doubled haploid lines from a cross between the varieties 'Baudin' and 'AC Metcalfe'. Linkage groups were assigned to barley chromosomes using published map locations of SSR markers as reference points. The total length of the map was 1307.2 cM with an average interval length of 5.6 cM between markers. The genetic map was used to locate quantitative trait loci (QTLs) for several disease resistance traits. The population was tested for spot type net blotch, caused by Pyrenophora teres f. maculata, and net type net blotch, caused by Pyrenophora teres f. teres, in greenhouse experiments and in a range of field environments in Western Australia and Queensland. The response of the lines to leaf rust ( caused by Puccinia hordei L.) at adult plant growth stages was evaluated in Western Australia. Significant marker-trait associations were found for seedling resistance and symptom severity in adult plants to these diseases. A new locus conferring resistance to P. teres f. maculata at both seedling and adult plant stages was detected on the short arm of chromosome 6H. From the seedling testing against P. teres f. teres, five highly repeatable QTLs were detected, on chromosomes 2HS, 2HL, 3HS, 4HL, and 6HS. For leaf rust, one highly significant QTL was detected on chromosome 2HL. The markers within these QTL regions present an opportunity for marker-assisted selection for these traits in barley-breeding programs.