Genetic identification and biological characterization of Baculovirus isolated from Helicoverpa armigera (Lepidoptera: Noctuidae) in Brazil
Keywords:
biological control, nucleopolyhedrovirus, vertical transmission, virus adaptionAbstract
Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae are polyphagous, aggressive, and have been found in many of Brazil’s agricultural areas. Biological control with baculoviruses is part of an integrated pest management (IPM) strategy to manage this insect. Three isolates of nucleopolyhedrovirus (NPV) were collected from Brazilian populations of H. armigera, and compared genetically and biologically to Gemstar® (an imported nucleopolyhedrovirus), and to Nucleopolyedrovirus spodoptera (SPNPV) that was passed serially through H. armigera. Genetic sequencing of lef-8 and lef-9 genes revealed that the Brazilian isolates were closely related to nucleopolyhedrovirus species from Australia, South Africa, China, and India. The isolates caused high mortality rates in third instar H. armigera larvae. The mean lethal dose (LD50) and lethal time (LT50) differed between isolates, but was highest for HearNPV-BR2. This is the first report of HearNPV in Brazil, and the insecticidal properties of the BR2 isolate support its potential use in the production of biopesticides to manage H. armigera in Brazil.
Resumo
Lagartas de Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) são polífagas, agressivas e foram identificadas no Brasil atacando extensas áreas de produção agrícola. O controle biológico de baculovírus faz parte do manejo integrado de pragas (MIP). Três isolados de nucleopoliedrovírus (NPV) foram coletados em populações brasileiras de H. armigera e comparados geneticamente e biologicamente, utilizando Gemstar®, com base em um nucleopoliedrovírus importado e multiplicação seriada de Nucleopolyedrovirus spodoptera (SPNPV) em H. armigera. Foram realizados testes genéticos e biológicos entre as estirpes autóctones, comparando-as com o produto comercial Gemstar®. A análise comparativa do sequenciamento genético realizada para os genes lef-8 e lef-9 revelaram que os isolados locais estão, estreitamente, relacionados com espécies de baculovírus da Austrália, Índia, África do Sul e China. Todos os isolados testados possibilitaram o controle de lagartas de terceiro instar de H. armigera. Analises biológicas da dose letal média (DL50) e do tempo letal médio (TL50) variaram entre os isolados testados. O isolado HearNPV-BR2 apresentou os melhores resultados de DL50 e TL50. Ademais, este é o primeiro registro da ocorrência da espécie HearNPV no Brasil, e suas propriedades inseticidas assinalam que a mesma pode ser útil para a fabricação de bioinseticidas para o controle de H. armigera no país.
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