Powdery mildew resistance in barley landrace material .1. Screening for resistance

A total of 4,681 accessions of Hordeum vulgare landrace material from Ethiopia, East Mediterranean, Near East, Nepal and China were sown in the field and subjected to the natural powdery mildew epidemic in Denmark. Apparently resistant accessions were selected. Selfed progeny from them were retested and reselected in subsequent years at four locations in Denmark. Finally, 16 promising donors of resistance were retained. They were characterized in the field and tested in the seedling stage for reaction to up to 72 different isolates of the powdery mildew fungus. The absence of the corresponding virulences in the Danish airborne powdery mildew population was ascertained in five years. The resistances in the 16 donors are apparently mutually different and from known sources of powdery mildew resistance in barley.