Abstract
Large and small plaque-producing populations of infectious hematopoietic necrosis virus were separated in a salmon embryo cell line, CHSE-214. Plaques produced by the two viral populations increased in size at different rates, indicating that the two plaque types were genetically determined. The small plaque type was numerically dominant in low-passage virus stocks from four locations and in unpassed virus from naturally and experimentally infected fish, suggesting that it is the wild type. The pH of the overlay medium appeared to influence the size of the plaque.
