Evaluation of seven viral isolates as potential biocontrol agents against Pseudoplusia includens (Lepidoptera: Noctuidae) caterpillars

Abstract

The caterpillar Pseudoplusia includens (Walker, 1857) (Lepidoptera, Noctuidae), known as soybean looper, is a pest that has recently assumed greater importance in soybean in Brazil. Isolates of nucleopolyhedroviruses (NPVs) of this pest have been identified from cotton in Guatemala and soybean farms in Brazil, providing an interesting perspective of potential use of viral insecticide against the insect in lieu to chemical insecticides. With the objective to contribute to the characterization studies of this virus, morphological and molecular analyses and biological activity were carried out with seven P. includens viral isolates (I-A to I-G). Electron microscopy of viral samples, purified from macerated infected larvae, showed particles with typical morphology of the Baculoviridae family, genus Alphabaculovirus (Nucleopolyhedrovirus - NPV) presenting virions with only a single nucleocapsid per envelope (SNPV) occluded in a protein matrix, forming occlusion bodies (OB). This virus was then classified as P. includens single nucleopolyhedrovirus (PsinSNPV). OB particles analyzed in SDS-polyacrylamide gel showed an intense band corresponding in size to NPV polyhedrin protein. DNA restriction profiles of the PsinSNPV isolates showed differences in the fragment size and number suggesting the existence of genotypic variants, except between I-E and I-F profiles that were similar. Among the isolates tested for infectivity against P. includens, I-A, I-E and I-F were the most virulent. Survival times (ST(50)) varied according to viral concentration, with significant differences among isolates for the three higher concentrations.

Complete Genome Sequences of Six Chrysodeixis includens Nucleopolyhedrovirus Isolates from Brazil and Guatemala

“…Single nucleotide polymorphisms observed among the ChinNPV genomes may also significantly contribute to phenotypic diversity and different degrees of pathogenicity previously reported among the seven isolates herein analyzed (1). …”

“…Chrysodeixis includens nucleopolyhedrovirus isolates, obtained from Chrysodeixis includens larvae collected from cotton and soybean crops from Brazil and Guatemala exhibited genetic and phenotypic diversity in previous studies (1, 2). These viral isolates were initially named as Pseudoplusia includens single nucleopolyhedrovirus (PsinSNPV).…”

Genoma e diversidade genética de populações de Chrysodeixis includens nucleopolyhedrovirus (ChinNPV)

“…includens NPV que vêm se apresentando como mais patogênicos a essa praga (Alexandre et al, 2010), surgem como uma interessante alternativa para os programas de Manejo Integrado de Pragas (MIP) em plantações de soja no Brasil.…”

“…Estudos de caracterização morfológica, molecular e de patogenicidade dos sete isolados virais (ChinNPV-IA a ChinNPV-IG), complementados com a identificação de polimorfismos em regiões altamente conservadas demonstraram a ocorrência de diversidade genética entre os isolados (Alexandre et al, 2010;Craveiro, 2012).…”

“…Diante disso, pôde inferir que as variações genéticas identificadas podem estar ocasionando a variação fenotípica observada entre os isolados, demonstrada pela maior patogenicidade apresentada pelos isolados ChinNPV-IA, ChinNPV-IE e ChinNPV-IF comparados aos outros quatro isolados analisados (Alexandre et al, 2010;Craveiro, 2012).…”