Inheritance and mapping of a powdery mildew resistance gene introgressed from Avena macrostachya in cultivated oat

The powdery mildew resistance from Avena macrostachya was successfully introgressed into hexaploid oat (A. sativa). Genetic analysis of F1, F2, F3 and BC1 populations from two powdery-mildew resistant introgression lines revealed that the resistance is controlled by a dominant gene, tentatively designated Eg-5. Molecular marker analysis was conducted using bulked-segregant analysis in two segregating F3 populations. One codominant simple sequence repeats (SSR) marker AM102 and four AFLP-derived PCRbased markers were successfully developed. The SSR marker AM102 and the STS marker ASE41M56 were linked to the gene Eg-5, with genetic distances of 2 and 0.4 cM, respectively, in both mapping populations. Three STS markers (ASE45M56, ASE41M61, ASE36M55) co-segregated with Eg-5 in one population while two (ASE45M56, ASE36M55) of them linked to Eg-5 with a genetic distance of 1 cM in another population. The gene was further mapped to be in a region corresponding to linkage group 22_44+18 in the Kanota £ Ogle (KO) hexaploid oat map by comparative mapping. To our knowledge, this is the Wrst report of mapping powdery-mildew resistance in hexaploid oat. The new resistance source of A. macrostachya, together with the tightly linked markers identiWed here, could be beneWcial in oat breeding programmes.