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Title: ENHANCEMENT IN ACTIVITY OF A GEOGRAPHICAL ISOLATE OF THE GYPSY MOTH NUCLEAR POLYHEDROSIS VIRUS DURING SERIAL PASSAGE

Author
item Shapiro, Martin
item ROBERTSON, JACQUELINE
item RATHBURN, HAROLD
item Dougherty, Edward

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Insect viruses are studied to determine their effectiveness as biological control agents against pest insects, in particular, the gypsy moth. Our studies of the pathogenicity of the gypsy moth, Lymantria dispar (L.)., nuclear polyhedrosis virus (LdMNPV) have progressed through several stages. First, we identified the most virulent NPV isolates that originated from North America, Europe, and Asia. Second, we demonstrated that heterogeneity among samples within a geographical isolate is a common phenomenon and we developed a means to identify the most virulent samples, and our third goal was the selection for a more virulent biotype from a heterogeneous LdMNPV population by using in vivo methodology. The Abington, MA isolate was previously shown to be more active than the EPA-registered Hamden, CT isolate. The Abington NPV isolate was then serially passed through gypsy moth larvae 11 times, in hopes of obtaining a still more potent virus. As a result of selection and passage, the isolate became more genetically uniform and killed more gypsy moth larvae at a faster rate than its original parent. This fast-killing virus could be an attractive microbial control agent against the gypsy moth.

Technical Abstract: An Abington, MA geographical isolate of LdMNPV was serially passed through gypsy moth larvae 11 times. After each passage, a sample was chosen as inoculum for the next passage on the basis of both early kill and LC(50)values. That is, the sample which produced the most rapid larval kill at the lowest concentration was selected as inoculum. As selection proceeded, greater numbers of Lymantria dispar (L.) larvae were killed by days 7-8 (i.e., early kill), indicating that in vivo passage had resulted in a faster acting virus biotype. Moreover, a greater percentage of the selected Abington NPV population exhibited faster kill. LC(50) values changed little during selection. Selection also resulted in a more homogeneous virus population, as evidenced by DNA analysis.