RESUMEN
Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) is a baculovirus widely used as a pest control agent. Data on field persistence of this microbial insecticide reveal that sunlight is the most destructive of the environmental factors. The introduction of a physical barrier to protect the baculovirus from sunlight has been proposed. In the present work we report on the coating of a baculovirus surface with a uniform layer of smaller particles. The coating was carried out at pH 3, a condition where the baculovirus surface becomes positively charged and can be covered by sulfate polystyrene latex particles. The heteroflocculation was assessed by isotherm measurements and scanning electron microscopy. High-affinity isotherms were obtained for the two sizes of latex used, and the number of latex particles bound per baculovirus was not affected when pH was changed back to neutral range (5
RESUMEN
Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) is a baculovirus specific for the control of an important soybean defoliator. The baculovirus is comprised of double-stranded DNA, occluded in a proteinaceous structure called a polyhedron. Ultraviolet sunlight is the most destructive factor that affects the persistence of the virus in the field. In the present study, we use a model system wherein the pathogen is covered by another particle of opposite charge in order to test the effectiveness of a physical barrier as a protection against sunlight. Heteroflocculation experiments were carried out using two different age batches of AgMNPV and amidine polystyrene latex particles. The assessment of heteroflocculation was achieved by zeta potential and adsorption isotherm measurements, and by scanning electron microscopy. Despite the great difference in potentials between latex particles and the baculovirus, low-affinity isotherms were obtained in both pure water and 0.1 mM KCl. Adsorbed latex particles were easily washed out from the polyhedron surface. This low affinity could be attributed to the presence of a strongly repulsive hydration force of short range operating on the system. The results suggest that the failure to obtain a good physical barrier against sunlight might be attributed to the difficulty in keeping the polyhedron surface covered. Copyright 2000 Academic Press.