IN-VITRO PRODUCTION STUDIES WITH A WILD-TYPE HELICOVERPA BACULOVIRUS

The potential use of a wild-type Helicoverpa baculovirus as a biopesti cide, using insect cell culture for its production, has been investiga ted. A Helicoverpa tea cell line was adapted to grow in suspension cul ture using a serum-free medium, SF900II and serum supplemented SF900II . The serum supplemented cells were infected with a wild-type nuclear polyhedrosis virus of Helicoverpa armigera (HaNPV), at different stage s of growth, in conditioned and fresh medium, to determine the effect of cell density on polyhedra production. Cultures infected at low cell densities, produced similar yields of virus (20-40 PIB/cell), irrespe ctive of medium conditions. However, in infections which occurred at h igh cell densities, there was a 16-fold improvement in cell specific y ields, when the spent medium was renewed with fresh medium prior to in fection. Results indicated that only 60-70% of the viable cells in a c ulture produced polyhedra as a result of infections.