Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2013
Publication Date: 2/1/2014
Publication URL: http://handle.nal.usda.gov/10113/58853
Citation: Harrison, R.L., Keena, M.A., Rowley, D.L. 2014. Classification, genetic variation and pathogenicity of Lymantria dispar nucleopolyhedrovirus isolates from Asia, Europe, and North America. Journal of Invertebrate Pathology. 116:27-35. Interpretive Summary: The gypsy moth is a serious pest of trees and forests in the United States and elsewhere. An environmentally safe insecticide for suppressing gypsy moth outbreaks has been developed from a gypsy moth virus. In this study, several samples of gypsy moth virus from all over the world were examined to see how they differ from each other and from the virus used to make the gypsy moth insecticide. A method for quickly identifying and gathering genetic information on insect viruses was used to document genetic differences among the gypsy moth virus samples. It was found that gypsy moth viruses isolated from Asia formed a group that was separate from gypsy moth viruses isolated from Europe and North America. Also, doses of the virus samples required to kill gypsy moth larvae were determined. The information in this study contributes to progress towards improving gypsy moth virus-based insecticides, and will be of interest to those in academia, government, and industry who work with this group of insect viruses or with gypsy moth.
Technical Abstract: Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) has been formulated and applied to control outbreaks of the gypsy moth, L. dispar. To classify and determine the degree of genetic variation among isolates of L. dispar NPVs from different parts of the range of the gypsy moth, partial sequences of the lef-8, lef-9, and polh genes were determined for Lymantria spp. virus samples from host populations throughout the world. Sequence analysis confirmed that all L. dispar virus samples tested contained isolates of the species Lymantria dispar multiple nucleopolyhedrovirus (Baculoviridae: Alphabaculovirus). Phylogenetic inference based on the lef-8 sequences indicated that the LdMNPV isolates formed two groups, one consisting primarily of isolates from Asia, and one consisting primarily of isolates from Europe and North America. The complete genome sequence was determined for an isolate from the Asian group, LdMNPV-2161 (S. Korea). The LdMNPV-2161 genome was 163,138 bp in length, 2,092 bp larger than the previously determined genome of LdMNPV isolate 5-6 (CT, USA). The two genome sequences were co-linear, with an overall nucleotide sequence identity of 97.5% and some differences in ORF content. In droplet-feeding bioassays against neonate L. dispar larvae, isolates LdMNPV-3029 (Virin-ENSh/Russia) and LdMNPV-Ab-a624 (MA, USA) killed neonate larvae with an LC50 values that were 1.8- to 3.2-fold lower than a sample of Gypchek® (CT, USA) and isolates LdMNPV-3041 (Japan) and LdMNPV-2161. This study expands our knowledge about genetic variation among LdMNPV isolates and provides novel information on the distinct groups in which these NPVs occur.