Selection and Screening of Clonal Isolates of the Abington Strain of Gypsy Moth Nuclear Polyhedrosis Virus

Abstract

Clonal isolates of the Abington strain of the Lymantria dispar multiple-embedded nuclear polyhedrosis virus (LdMNPV) were selected by plaque purification. After an initial screening for productivity of 35 clones in a continuous gypsy moth cell line (IPLB-LdFB), 17 clones were selected for further evaluation in vivo and in vitro. An eighteenth clone, LdMNPV-Ab-a624, was also included in these experiments as our "type" isolate. Based on these tests, extensive variability can be seen in the Abington isolate of the gypsy moth virus. While relatively little in vitro productivity differences were observed between the clones, two clones showed no activity in a larval bioassay while the mean lethal concentration for 50% of the test insect (LC50's) for the other clones ranged from 2.2 × 104 to greater than 6.5 × 105 occlusion bodies per diet cup, with the a624 clone having a LC50 of 1.2 × 105. The LT50's (time for half the larvae to die) varied from 9.8 to 18.7 days in these clones with a624 having a LT50 of 13.5 days. While certain advantages exist for the use of clones in biopesticide production schemes, the results of this study indicate careful screening of isolates should be made to ensure an acceptable product.