Pathogenic Variation of Pyrenophora teres Isolates Collected from Japanese and Canadian Spring Barley

Twenty-two isolates of Pyrenophora teres Drechs. collected from Japanese and Canadian spring barleys were inoculated to 38 barley varieties having various genetic backgrounds. The analysis of variance for the discase ratings showed that there were significant differences both in the virulence of isolates and the resistance of varieties. However, the interaction among isolates and varieties was not statistically significant. Both Finlay-Wilkinson regression analysis and principal component analysis by Additive Main effects and Multiplicative Interaction effects(AMMI)model classified the isolates into three groups,which were different in origins and sympton types. A spot tyte isolate was distinguished from net type isolates by its generally high virulence. A slight pathogenic differentiation was suggested between Japanese and Canadian net type isolates.