Identity of barley powdery mildew resistances Bw and Ru2

Abstract

A large number of resistances to powdery mildew (Blumeria graminis f.sp. hordei) and their combinations are known in barley (Hordeum vulgare L.). A similarity of resistance spectra between cultivars carrying the resistance Bw, designated for the winter barley cultivar Borwina, and the near-isogenic spring barley line P15, which carries the resistance Ru2, derived from the landrace Rupee, was found. The objective of this study was to test the difference between resistances Bw and Ru2. Six cultivars were tested, four with Bw and two with Ru2. Testing with 40 isolates showed identical reaction spectra between both groups. Testing of the cultivarKompolti 4 (Bw) and line P15 (Ru2) with 300 isolates confirmed this result. Thus, the resistances currently designated Bw and Ru2 can be regarded as identical, and are determined by the gene Ml(Ru2). Both Bw and Ru2 should be designated by the earlier code, Ru2.