Biological and biochemical comparison of Mamestra configurata and Mamestra brassicae nuclear polyhedrosis virus isolates pathogenic for the bertha armyworm, Mamestra configurata (Lepidoptera: Noctuidae)

Abstract

Nuclear polyhedrosis viruses (NPVs) isolated from bertha armyworm, Mamestra configurata, populations and three NPVs from a related host species, Mamestra brassicae, were compared. Bioassays in first-instar M. configurata showed that the origin of a particular NPV was not predictive of its virulence in bertha armyworm. A M. brassicae NPV, MbNPV-NL, was the most virulent isolate tested with an LD 50 of 10.8 occlusion bodies (OBs) per individual at 10 days postinoculation. A second MbNPV, MbNPV-D, was significantly less virulent than the other isolates with an LD 50 of 154.2 OBs per individual. Although not significantly different from MbNPV-NL, the third MbNPV, MbNPV-NL82/1, and the native M. configurata NPV, McNPV-86/1, were less virulent with LD 50s of 41.3 and 20.1 OBs per individual, respectively. Comparisons of virion structural polypeptides by SDS-PAGE analysis indicated that the McNPV isolates had polypeptide profiles which were distinct from those of the MbNPV isolates, which were all similar. Restriction endonuclease analyses of the virus genomes revealed that the two McNPV isolates had almost identical restriction endonuclease fragment patterns which were distinct from those of the MbNPV isolates.