Selection of a nucleopolyhedrovirus isolate from Helicoverpa armigera as the basis for a biological insecticide

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Background: the cotton bollworm, Helicoverpa armigera, is an insect that causes damage in a wide range of crops in Spain.Seven isolates of H. armigera single nucleopolyhedrovirus (HearSNPV) from the Iberian Peninsula were subjected to molecularand biological characterization and compared with a Chinese genotype (HearSNPV-G4). Results: the estimated sizes of the Iberian genomes varied between 116.2 and 132.4 kb, compared to 131.4 kb of theHearSNPV-G4 reference genome. Phylogenetic analysis based on the lef-8, lef-9 and polh genes revealed that the Iberianstrains were more closely related to one another than to other HearSNPV isolates. Occlusion body (OB) concentration-mortalityresponses (LC 50 values) did not differ significantly among Iberian isolates when tested against a Helicoverpa armigera colonyfrom Oxford (UK). Despite being the fastest killing isolate, HearSNPV-SP1 was as productive as isolates with lower virulence,with an average yield of 3.1 × 109 OBs larva−1 . OBs of HearSNPV-SP1 and HearSNPV-G4 were similarly pathogenic against arecently established colony from southern Spain, although HearSNPV-SP1 was faster killing than HearSNPV-G4 against a rangeof instars. Conclusion: the insecticidal properties of HearSNPV-SP1 mean that this strain is likely to prove useful as the basis for abiological insecticide for control of Helicoverpa armigera in Spain.

This study wasfunded by MEC project numbers AGL2008-05456-CO3-01 and AGL2011-30352-CO2-01 as well as the Gobierno de Navarra project IIQ14065.RI1