Altered phenotypic expression of ultraviolet-irradiated nuclear polyhedrosis virus.

UV (254 nm) irradiation of nuclear polyhedrosis virus results in formation of small plaques. The small-plaque effect is reversed by photoreactivation. Analysis of plaque formation kinetics indicates a slower formation and subsequent enlargement of plaques from UV-irradiated virus in comparison to non-irradiated virus. A delay in viral DNA synthesis is suggested as an explanation for the observed small-plaque effect.