Identificação de genes cry de Bacillus thuringiensis no controle de Sphenophorus levis, o bicudo da cana-de-açúcar
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Data
2009-01-01
Autores
Cícero, Elaine Aparecida Silva [UNESP]
Ferraudo, Antonio Sergio [UNESP]
Lemos, Manoel Victor Franco [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Instituto Agronômico de Campinas
Resumo
A bactéria B. thuringiensis caracteriza-se pela produção de proteínas tóxicas a representantes de diversas ordens de insetos, as quais são codificadas por genes cry. Este trabalho foi realizado com objetivo de selecionar isolados de B. thuringiensis, por meio da caracterização morfológica e molecular, identificando as diferentes subclasses dos genes cry3 e cry35 e determinar a patogenicidade contra Sphenophorus levis, uma das mais importantes pragas da cultura da cana-de-açúcar. Foram utilizados 1163 isolados de B. thuringiensis e com a observação em microscópio com contraste de fases foram confirmadas como pertencentes à espécie de B. thuringiensis. O material genético foi purificado pela matriz de troca iônica Instagene Matrix e submetido a PCR com iniciadores gerais cry3 e cry35 identificando-se 30 isolados contendo genes com potencial para o controle de coleópteros, os quais juntamente com as linhagens-padrão de B. thuringiensis var. tenebrionis, B. thuringiensis var. morrissone e B. thuringiensis var. tolworthi foram utilizados para a realização do bioensaio. Através de análise discriminante alocaram-se os isolados em quatro grupos quanto à toxicidade de B. thuringiensis. Os grupos ficaram assim definidos: um grupo que promovem até 10% de mortalidade contendo as testemunhas e duas linhagens;um grupo que causou 39% de mortalidade contendo três linhagens padrão e dez isolados; um grupo com 52% de mortalidade contendo treze isolados e um grupo com 70% de mortalidade contendo cinco isolados, os quais devem ser considerados promissores no controle biológico de S. levis.
Bacillus thuringiensis is well known for its ability to produce toxic proteins to different insect orders which are encoded by the cry genes. This work was carried out aiming to select among different B. thuringiensis isolates, by morphological and molecular characterization, identifying different classes of cry3 and cry35 genes, and to determine the level of pathogenicity against Sphenophorus levis larvae, which is one of the most important sugar-cane pests in Brazil. A total of 1163 bacterial isolates were used in this survey in which phase microscopy and molecular markers were used for evaluation that resulted in 30 isolates positive for cry3 and cry35 genes potentially active against coleopterans. These bacterial isolates together with type strains such as B. thuringiensis var. tenebrionis, B.t. var. morrissone e B.t. var. tolworthi were used in bioassays using Sphenophorus levis larvae. Using discriminating analysis four groups of isolates were produced when B. thuringiensis toxicity was taken into account. These groups involved one set of two isolates with up to 10% mortality; another set caused mortality of up to 39% and was made up of ten isolates and three type strains; another set caused mortality of up to 52% containing thirteen isolates and a last set of isolated whose mortality index was 70% containing only five isolates which were considered promising bacterial strains for biological control of S. levis.
Bacillus thuringiensis is well known for its ability to produce toxic proteins to different insect orders which are encoded by the cry genes. This work was carried out aiming to select among different B. thuringiensis isolates, by morphological and molecular characterization, identifying different classes of cry3 and cry35 genes, and to determine the level of pathogenicity against Sphenophorus levis larvae, which is one of the most important sugar-cane pests in Brazil. A total of 1163 bacterial isolates were used in this survey in which phase microscopy and molecular markers were used for evaluation that resulted in 30 isolates positive for cry3 and cry35 genes potentially active against coleopterans. These bacterial isolates together with type strains such as B. thuringiensis var. tenebrionis, B.t. var. morrissone e B.t. var. tolworthi were used in bioassays using Sphenophorus levis larvae. Using discriminating analysis four groups of isolates were produced when B. thuringiensis toxicity was taken into account. These groups involved one set of two isolates with up to 10% mortality; another set caused mortality of up to 39% and was made up of ten isolates and three type strains; another set caused mortality of up to 52% containing thirteen isolates and a last set of isolated whose mortality index was 70% containing only five isolates which were considered promising bacterial strains for biological control of S. levis.
Descrição
Palavras-chave
PCR, Bioassay, Biological control, PCR, Bioensaio, Controle biológico
Como citar
Bragantia. Instituto Agronômico de Campinas, v. 68, n. 4, p. 817-823, 2009.