Localization of powdery mildew resistance gene Ml-ra on barley chromosome 5

Evidence is presented that the powdery mildew resistance gene called Ml-(41/145) represents a unique, unnamed locus, which we suggest to be designated Ml-ra with reference to variety ‘Ragusa b’. Ml-ra is located on the short arm of chromosome 5 near powdery mildew resistance locus Ml-a and the seed storage protein loci Horl and Hor2. The most likely order of the loci is Horl, Ml-a, Ml-ra, and Hor2.