VARIATION IN SEEDLING AND ADULT-PLANT RESISTANCE TO RHYNCHOSPORIUM-SECALIS IN BARLEY

Sixty-six barley cultivars and advanced lines from western Canada were evaluated for resistance to scald caused by Rhynchosporium secalis in both greenhouse-grown seedlings and field-grown adult plants. Eleven of these genotypes had different reactions in the seedling and in the adult plant as measured by percentage leaf area with symptoms (LAS). O f the 66 genotypes, 29 were resistant (LAS < 10) and 3 were moderately resistant (LAS greater than or equal to 10 but < 30) in both seedling and adult plant stages; and 8 were susceptible (LAS greater than or e qual to 30) as seedlings but resistant or moderately resistant as adul t-plants. The rational use of seedling and adult-plant screening for s cald resistance and the desirable types of resistance for breeding pro grams are discussed.