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Stability of Stagonospora nodorum Isolates from Perennial Grass Hosts after Passage Through Wheat

Eleven isolates of Stagonospora nodorum from smooth brome, western wheatgrass, intermediate wheatgrass, Altai wildrye, basin wildrye, and an Agropyron cross were passed through wheat five times using detached leaf inoculations. Lesion length, which was used as a measure of adaptation and aggressiveness, did not increase after passage through wheat. When the wheat-isolate check was removed from the analyses, the cultivar × isolate interactions were nonsignificant, indicating a lack of specificity among the original isolates and isolates passed through wheat. Inoculation of wheat seedlings in a glasshouse confirmed the results obtained with the detached leaf inoculations. These isolates showed no progressive adaptation to wheat and no significant change in their aggressiveness. This indicates that since most isolates from perennial grass hosts produce small lesions on wheat and do not easily adapt to wheat, they apparently would not cause severe symptoms on wheat.