RFLP mapping of the ym4 virus resistance gene in barley

RFLP (restriction fragment length polymorphism) mapping of a recessive gene (ym4) conferring resistance to barley yellow mosaic and barley mild mosaic virus was performed using progeny of 86 F1 anther-derived doubled haploid lines. Two closely linked RFLP markers that flank the gene at a distance of 1.2 centiMorgans were identified. Using one of these markers (MWG10) we obtained a clear differentiation between resistant and susceptible German cultivars. An analysis of a series of unrelated barley lines with probe MWG10 did not reveal additional RFLP fragments. The use of this probe for both marker-assisted selection and the generation of a high-density map around the resistance locus is discussed.