Restriction endonuclease cleavage patterns of commercial and serially passaged isolates of Heliothis baculovirus.

The restriction endonuclease patterns of three Baculovirus isolates (Br, Vh, El) from Heliothis zea having different passages and production histories were compared. Digestion of the ds DNA genomes of the three isolates with EcoRI, HindIII, and XhoI showed no major difference in the cleavage patterns, although submolar fragments were detected. One of the commercial isolates (Vh) was serially passaged 20 times through larvae of H. zea and a substitute host, H. virescens. EcoRI cleavage profiles of the ds DNA showed the absence of a band in the 3-megadalton region that was present in the original isolates. In addition, the cleavage pattern of the DNA from Vh passed in H. zea showed additional submolar fragments in the 15- and 6-megadalton regions. Differences also were observed in the HindIII and XhoI restriction patterns. No significant differences in virulence between the original isolate and passage isolates were detected after 20 serial passages in larvae of either H. zea or H. virescens.