Molecular detection of endosymbionts in local populations of Helicoverpa armigera (Lepidoptera: Noctuidae) in European part of Russia

Cotton bollworm Helicoverpa armigera is one of the most polyphagous and cosmopolitan pests. Intracellular endosymbionts are widespread in Lepidoptera, often playing an important role in their dynamics. The prevalence of endosymbionts of cotton bollworm in Russia was not investigated. Cotton bollworm larvae and adults were collected in 2018–2020 in Krasnodar Area, and in Voronezh and Saratov Regions (from 131 to 170 insects) and analyzed by PCR using sets of group-specific primers for baculoviruses (locus lef8), bacteria of the genus of Wolbachia (locus wsp), and microsporidia (locus SSU rRNA). Level of infection with baculoviruses was 16 % for the sample of 32 individuals collected in Temryuk District of Krasnodar Area in 2018. The infection rate of the entire sample of 170 individuals was 2.9 %. The lef8 locus demonstrated 98.7–99.6 % of sequence similarity to the nuclear polyhedrosis virus isolates from the cotton bollworm and American bollworm. Among the tested 131 insects, bacteria of the genus of Wolbachia were not detected. PCR screening for microsporidia revealed one positive larvae among 19 insects collected in Krasnoarmeysk District of Krasnodar Area in 2019, which corresponded to the prevalence of 5 %. Partial sequencing of the genes coding for SSU rRNA and largest subunit RNA polymerase II made it possible to identify the new isolate as N. bombycis.