Hypovirulence-associated suppression of host functions in Cryphonectria parasitica can be partially relieved by high light intensity

Phenotypic expression by cultured isogenic virulent (EP155) and hypovirulent (EP713) strains of the chestnut blight fungus, Cryphonectria parasitica, was examined under different light regimens. Colony morphology and the levels of pigmentation, conidiation, oxalate accumulation, and phenol oxidase production were all influenced by light intensity, but to different degrees in the two strains. Significantly, exposure of strain EP713 to high light intensity partially relieved the hypovirulence-associated suppression of pigmentation, conidiation, and oxalate accumulation observed at low or intermediate light intensity. These results suggest that light and hypovirulence-associated double-stranded RNAs may influence C. parasitica gene expression by the same or converging regulatory pathways.