Penicillium stoloniferum virus: altered replication in ultraviolet-derived mutants

Phenotypic mutants of the wild type of Penicillium stoloniferum NRRL5267 were obtained from conidia exposed to ultraviolet light for 60 min (10% survival). Virus content of the wild type and of nine phenotypic mutants was determined by polyacrylamide gel electrophoresis. Four mutants had no detectable Penicillium stoloniferum virus F (PsV-F), whereas the other five had levels of PsV-F in the mycelium similar to the wild-type strain. All nine mutants and the wild type had comparable levels of Penicillium stoloniferum virus S (PsV-S). Maximum virus levels occurred after 9 days of submerged culture in a 2% yeast extract-15% sucrose medium. Virus replication in the fungal host continued after protein, RNA and DNA synthesis levelled off. Virus levels ranged from 85 to 150 E-260 units (extinction units at 260 nm in I cm cell) per 4-7 to 5-3 g dry weight of mycelium for the mutant strains compared to 106 E-260 units per 4-2 g dry weight of the wild-type strain.