Abstract
Host specificity of the powdery mildew fungus Blumeria graminis (Erysiphe graminis) isolated from Asperella longe-aristata was clarified by inoculating 16 graminaceous plant species. The fungus was virulent on Triticum spp. in addition to the original host plant species. Isolates of B. graminis f. sp. tritici were virulent on both A. longe-aristata and Triticum spp., however, other formae speciales of Blumeria graminis in Japan were avirulent on A. longe-aristata. Cross-compatibility tests between formae speciales of the fungus showed that an isolate of B. graminis from A. longe-aristata was fertile when crossed with f. sp. tritici of the fungus. These findings show that B. graminis isolated from A. longe-aristata should be classified as f. sp. tritici.
