Collecting and partial characterization of Iranian Helicoverpa armigera Single NucleopolyhedroVirus isolates based on polh gene

Nucleic acid-based diagnostic approaches are significant methods in detection and identification of viruses due to their small genome structures and minimal nucleotide differences among virus isolates or strains. In this study, dead or diseased larvae of Helicoverpa sp. were collected from tomato fields in distinct geographic areas in Iran and baculovirus infection was assayed by occlusion body extraction using an optimized Sodium Dodecyl Sulphate method. Two sets of specific polymerase chain reaction (PCR) primer pairs (Pol-a and Pol-b) were designed based on the conserved polyhedrin gene region of 26 fully sequenced HearSNPV/HzNPV isolates. Accordingly, infection by HearSNPV was confirmed in 28 out of 34 tested larvae by PCR amplification of monomorphic fragments of about 370 and 790 nucleotides, respectively. Cloning and sequencing of fragments showed that they belong to the corresponding polyhedron gene from nucleopolyhedriviruses of H. arimegra and H. zea species with 99.6% sequence identity. The phylogeny trees developed for Iranian isolates based on their polyhedron gene sequences showed that they all belong to the Group II Alphabaculovirus and formed one clade with other HearSNPV isolates. This, further confirmed the efficiency of the developed method for baculovirus detection and characterization. To our knowledge, this is the first report of introduction and molecular characterization of some HearSNPV isolates, circulating in these pests in Iran, using a robust DNA-based approach. The excellent efficacy of this method in virus detection makes it a valuable tool for rapid screening of insect cadavers for HearNPV infection, phylogenic studies and virus monitoring in bioinsecticides application.