Mapping genes for resistance to barley stripe rust (Puccinia striiformis f. sp. hordei).

Two genes conferring resistance to the barley stripe rust found in Mexico and South America, previously identified as race 24, were mapped to the M arms of barley chromosomes 7 and 4 in a doubled haploid population using molecular markers and the quantitative trait loci (QTL) mapping approach. The resistance gene on chromosome 7 had a major effect, accounting for 57% of the variation in disease severity. The resistance gene on chromosome 4 had a minor effect, accounting for 10% of the variation in trait expression. Two pairs of restriction fragment length polymorphism markers are being used to introgress the resistance genes to North American spring barley using molecular marker-assisted backcrossing.