Molecular characterization of Helicoverpa armigera Nucleopolyhedrovirus (HearNPV) on Helicoverpa armigera Hübner larvae (Lepidoptera: Noctuidae)

Abstract

Nucleopolyhedrovirus (NPV) is a type of biological agent that can be effectively used as a bioinsecticide to control the cob borer caterpillar in corn. Among these viruses, HearNPV (Helicoverpa armigera Nucleopolyhedrovirus) stands out due to its host specificity, environmentally safety, and lack of harm to non-target organisms. The primary objective of this study was to elucidate the molecular characteristics of the DNA polymerase gene of HearNPV. To achieve this, caterpillars were collected from the field, then reared and inoculated in the laboratory under controlled conditions. Following propagation, viral genomic DNA was extracted using a modified CTAB (Cetyltrimethylammonium Bromide) protocol, which is commonly employed for its efficiency in isolating high-quality DNA from various sources. Subsequently, DNA amplification was performed using specific primers: forward primer HearNPV F and reverse primer HearNPV R. These primers were designed to target the DNA polymerase gene, a crucial component in viral replication and a key marker for phylogenetic studies. The results of the phylogenetic analysis indicated that the Bogor strains of HearNPV shared a high degree of similarity with NPVs that infect other species within the Helicoverpa genus, including strains from Spain, Australia, Brazil, Russia, and Japan. Specifically, the nucleotide sequence homology ranged from 98.4% to 99.4%, while the amino acid sequence homology ranged from 98.2% to 99.2%. This high level of homology suggests a close evolutionary relationship and potentially similar biological characteristics among these NPV strains.