Insecticidal activities of wild type and recombinant invertebrate iridescent viruses on five common pests

Invertebrate iridescent virus 6 (IIV6) can infect a broad range of pest insect species. Viruses with new features created by recombinant DNA technology can be used effectively as biological control agents. Previously, recombinants have been constructed: IIVs harboring green fluorescent protein gene (gfp) in place of IIV6 157L ORF (rCIV-Delta 157L-gfp) and a scorpion Androctonus australis (Linnaeus, 1758) insect toxin gene (AaIT) fused with gfp (rCIV-Delta 157L/gfp-AaIT). In this study, wild type IIV6 and the two recombinants, were evaluated for their ability to cause infections on Helicoverpa armigera (Hubner, 1805) (Lepidoptera: Noctuidae), Spodoptera littoralis (Boisduval, 1883) (Lepidoptera: Noctuidae), Lymantria dispar (Linnaeus, 1758) (Lepidoptera: Erebidae), Euproctis chtysorrhoea (Linnaeus, 1758) (Lepidoptera: Erebidae) and Tenebrio molitor (Linnaeus, 1758) (Coleoptera: Tenebrionidae) larvae. This study was performed at Karadeniz Technical University, Department of Biology during 2018 and 2019. Five different concentrations (10(3), 10(4), 10(5), 10(6) and 10(7) TCID50/ml) of viruses were used to inject each insect larvae. All larvae, infected with rCIV-Delta 157L/gfp-AaIT, became paralyzed, except S. littoralis. The LC50 of insect larvae infected by rCIV-Delta 157L/gfp-AaIT were determined as 0.3 x 10(7), 0.7 x 10(5), 0.2 x 10(5), 0.15 x 10(5), 0.7 x 10(4) TC1D(50)/ml on S. littoralis, T. molitor, L. dispar, H. amiigera and E. chtysorrhoea, respectively. LT50 values, calculated according to the highest virus concentrations, were found as 10.5, 6.2, 4.7, 7.5 and 5 d on S. littoralis, T. molitor, L. dispar, H. armigera and E. chrysorrhoea, respectively, for rCIV-Delta 157L/gfp-AaIT. This study showed that recombinant IIV6 has increased pathogenicity on some insects from Lepidoptera and Coleoptera.