The polyhedral membrane does not protect polyhedra of AcMNPV against inactivation on greenhouse chrysanthemum

Polyhedral inactivation of wild-type AcMNPV and an AcMNPV mutant lacking th e gene for the polyhedral membrane pi protein (AcMNPV-Delta pp34) was studi ed on greenhouse chrysanthetnum. It was hypothesized that polyhedra without a polyhedral membrane might be more susceptible to inactivation on plants. The density of infectious polyhedra of both viruses on the leaf surface de creased in time in a near-exponential fashion. The inactivation curves sugg ested the presence of two distinct fractions of polyhedra with differences in persistence. One function of polyhedra is not inactivated at all, wherea s the other fraction is inactivated in an exponential fashion. Relative ina ctivation rates of the inactivated polyhedra fraction for wild-type AcMNPV and AcMNPV-Delta pp34 were 0.16 and 0.13 per day, respectively, which is no t significantly different. After 28 days on leaves in a greenhouse, both vi ruses still showed residual infectivity. The fi action of residual infectio us polyhedra were not significantly different and amounted to approximately 20% of the original density for both wild-type AcMNPV and AcMNPY-Delta pp3 4. Therefore, the polyhedral membrane does not protect polyhedra against in activation on greenhouse chrysanthemum.