| Thirty-five isolates of Cryphonectria parasitica were collected from 15 sites throughout southern Ontario from 1985-1991. All isolates were characterized for morphology in agar culture, virulence in apple and chestnut (Castanea dentata), and the presence of double-stranded RNA (dsRNA). Based on cultural morphology, eight isolates (CCP-1, CCP-2, CCP-4, CCP-14, CCP-15, CCP-19, CCP-28, and CCP-29) were atypical of virulent standard isolates and possessed at least some cultural characteristics associated with hypovirulent isolates of C. parasitica. In the apple virulence assay, 15 Ontario isolates produced significantly smaller lesions in apple tissue than five out of the six virulent standard isolates. In the chestnut sprout assay, seven isolates (CCP-1, CCP-2, CCP-14, CCP-15, CCP-19, CCP-28, and CCP-29) produced significantly smaller lesions than the virulent standard isolates.;To examine the potential for biological control of chestnut blight in Ontario, the vegetative compatibility (v-c) groups of the Ontario isolates and the conversion capability of selected hypovirulent isolates was determined. Eighty percent of the virulent Ontario isolates tested (representing eight v-c groups) were converted by hypovirulent isolates GH 2, Ep 713, Ep 50, and Ontario hypovirulent isolates CCP-19, CCP-28, and CCP-29.;A mixture of Canadian, American, and European hypovirulent isolates may provide an effective biological control strategy for chestnut blight in Ontario. (Abstract shortened by UMI.)... |
