Isolation characterization and pathogenicity of Helicoverpa armigera single nucleopolyhedrovirus isolate from Türkiye

Abstract

The cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is a major pest of agricultural crops, such as cotton, horticultural plants, a range of vegetable crops and forest trees. Many dead and live larvae and pupa samples of H. armigera, an extremely polyphagous pest, were collected from Adana in Türkiye. It was observed that cadaveric integuments were fragile, and their body tissues were also liquefied. Studies with phase-contrast microscopy revealed a very intense baculovirus infection in cadavers. Transmission electron microscopy exhibited that the new baculovirus had one nucleocapsid in an envelope in the occlusion bodies. Therefore, the isolate was named Helicoverpa armigera single nucleopolyhedrovirus-D (HearSNPV-D). The phylogenetic analysis according to the polyhedrin and late expression factor-8 genes appeared that the new isolate was in close relationship with HearSNPV China and Türkiye isolate. The new isolate was tested on six different insects including its own host Helicoverpa armigera, Hyphantria cunea, Malacosoma neustria, Lymantria dispar, Thaumetopea pityocampa and Spodoptera exigua larvae. Bioassay studies showed that HearSNPV-D was virulent to H. armigera and had a narrow host range. The LC50 value was determined as 0.7 × 105 and 1.9 × 107 OBs/ml for H. armigera and S. exigua, respectively. Non-significant mortality was observed in non-host species by HearSNPV-D, which may reveal the highly specific nature of HearSNPV-D. Therefore, HearSNPV-D can be used as a specific, environmentally friendly control agent for H. armigera.