Robert L. Harrison

The nucleopolyhedroviruses of Rachiplusia ou and Anagrapha falcifera are isolates of the same virus.

The 7.8 kb EcoRI-G fragment of Rachiplusia ou multicapsid nucleopolyhedrovirus (RoMNPV), containing the polyhedrin gene, was cloned and sequenced. The sequence of the fragment was 92.3% identical to the sequence of the corresponding region in the Autographa californica (Ac)MNPV genome. A comparison of the EcoRI-G sequence with other MNPV sequences revealed that RoMNPV was most closely related to AcMNPV. However, the predicted amino acid sequence of RoMNPV polyhedrin shared more sequence identity with the polyhedrin of Orygia pseudotsugata MNPV. In addition, the RoMNPV sequence was almost completely identical (99.9%) to a previously published 6.3 kb sequence of Anagrapha falcifera MNPV (AfMNPV). The EcoRI and HindIII restriction fragment profiles of RoMNPV and AfMNPV also were nearly identical, with an additional EcoRI band detected in RoMNPV DNA. Bioassays of these viruses with three different hosts (the European corn borer, Ostrinia nubilalis Hubner, the corn earworm, Helicoverpa zea Boddie, and the tobacco budworm, Heliothis virescens Fabricius) failed to detect any differences in the biological activities of RoMNPV and AfMNPV. These results indicate that RoMNPV and AfMNPV are different isolates of the same virus. The taxonomic relationship of Ro/AfMNPV and AcMNPV is discussed.

Genetic Enhancement of Baculovirus Insecticides

Baculoviruses are arthropod-specific viruses that infect species mainly within the order Lepidoptera (Adams and McClintock, 1991). The two genera nucleopolyhedrovirus (NPV) and granulovirus (GV), within the family Baculoviridae, are identified by occlusion body morphology with single (GV) and multiple (NPV) virions occluded in granules or polyhedra respectively. Baculoviruses are regarded as safe and selective insecticides, but although they have been used successfully for management of a number of agricultural and forestry pests (Federici, 1999; Moscardi, 1999), their use as microbial pesticides has not met their potential. Two of the main reasons for their limited use are the slow speed of kill of the targeted pest relative to classical chemical insecticides, and a narrow host range that may exclude many of the pest species found on a given crop. Genetic engineering has been used successfully to improve the speed of kill of baculovirus insecticides (Harrison and Bonning, 2000a; van Beek and Hughes, 1998). The baculovirus Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) optimized by genetic engineering for improved insecticidal efficacy has shown performance under field conditions comparable to that of classical chemical insecticides (Black et al., 1997; Treacy, 1997; Treacy et al., 2000; DuPont, 1996).