POLYHEDRA WITHOUT VIRIONS IN A VERTICALLY TRANSMITTED NUCLEAR POLYHEDROSIS-VIRUS

Polyhedra were observed in larvae, pupae, and adults (f1 generation) of Spodoptera frugiperda whose parents had survived exposure to the S. frugiperda nuclear polyhedrosis virus (NPV). These polyhedra were isolated from the f1 insects and fed to first instars. The polyhedra from f1 larvae and pupae infected the first instars (86-98 and 69-88% infection, respectively), but most of those recovered from adults of the f1 generation did not (0-11% infection). Electron microscopy indicated that the infectious polyhedra from adults contained virions, but the noninfectious polyhedra from adults did not. A monoclonal anti-polyhedrin antibody used in conjunction with fluorescence microscopy reacted positively with the empty, noninfectious polyhedra, indicating that the polyhedrin protein was present. Thus, when the S. frugiperda NPV is vertically transmitted, the infections in the f1 adults are nonlethal and are manifested mainly as noninfectious, empty polyhedra which are composed of the polyhedrin protein. © 1992.