RESISTANCE TO PYRENOPHORA BROMI IN BROMEGRASS

The resistance of strains of northern, southern, and northern/southern hybrids of smooth bromegrass (Bromus inermis) to Pyrenophora bromi, the cause of a major leaf spot disease, was determined in field tests in northern Saskatchewan from 1967 to 1971. Infection derived from natural epidemics was supplemented with that from highly susceptible infector plants spaced in the test plots to improve uniformity of inoculum supply. No bromegrass strains were completely resistant to the pathogen. Four of the eight northern/southern cultivars and three of the five southern cultivars were more resistant to P. bromi than any of the nine northern types. The best southern cultivars, Baylor and Sac, were not significantly more resistant than the cult Magna and less resistant than the S-7382 and S-7306 strains, all of northern/southern-type. Basic clones of northern/southern-type strains, adapted to Western Canada, were superior in resistance to northern clones. Parental clones were more resistant than their progeny and this resistance declined from the Syn. 1 to the Syn. 2 in two northern/southern strains. Selection for resistance to the other major leaf spot pathogen, Selenophoma bromigena, resulted in a limited improvement also in resistance to P. bromi.