Investigation of genetic heterogeneity in wild isolates of Spodoptera frugiperda nuclear polyhedrosis virus by restriction endonuclease analysis of plaque-purified variants.

Spodoptera frugiperda nuclear polyhedrosis virus (SfMNPV was obtained from four different sources and each isolate was cultured in IPLB-SF21 cells. Viral DNA from each isolate was analyzed with EcoR1, Xho1, and BamH1 restriction endonucleases. All four isolates could be distinguished on the basis of minor differences in EcoR1 patterns. Submolar DNA restriction fragments were seen in all isolates indicating that each isolate consisted of a mixture of different genotypes. To investigate this, two of the isolates were plaque purified. Of the total of 13 clones isolated, the DNA from 5 of these had distinctly different EcoR1 restriction endonuclease patterns. The five cloned variants were further analyzed with Xho1, BamH1, and Sac1. Three of the five clones had fragments which comigrated with submolar fragments seen in the wild isolates. Thus, the submolar fragments observed in digests of the DNA from two wild isolates of SfMNPV were due to a mixture of genetic variants.