Screening of Bacillus thuringiensis strains toxic to the cotton aphid (Aphis gossypii) / Seleção de estirpes de Bacillus thuringiensis tóxicas ao pulgão do algodoeiro (Aphis gossypii)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The production of the cotton crop is growing and exposes this culture to severe attack of various pests, including the cotton aphid (Aphis gossypii). This insect has caused 44% loss to the culture of cotton, attacking the initial stages of the crop. The continuous sucking sap deforms the shoots, hampers the development of the plant and also expels a sugar secretion ("honeydew") that has symbiotic association with ants and favors the emergence of fumagina. A. gossypii can cause indirect damage through the transmission of virotic diseases such as vermelhão and mosaic of ribs ("azulão"). The control of this pest by the intensive use of chemical insecticides can cause the imbalance of the environment, acting on the natural enemies and selecting resistant populations. Thus, the biological control emerges as an alternative for the control of this pest. Bacillus thuringiensis is a Gram positive bacterium, which produces protein inclusions, known as δ-endotoxins, which have toxic activity to some orders of insects. This bacterium has the potential to be used for the control of sucker insects by the systemic use or using genetically modified plants with cry genes active to the target insect. Strains of the Bank of Germplasm of Bacillus spp. of Embrapa Recursos Genéticos e Biotecnologia were tested against A. gossypii by selective bioassay which were selected the strains S29, S40, S616, S1168 and S1576 that showed more than 50% of mortality. The five selected strains were characterized by protein profile, which ranged from 50 to 130 kDa, and by molecular profile, where some of them were positive for the presence of genes cry1Aa, cry1D, cry2 and cry8. The characterization by electronic microscopy round and bipiramidal crystals were seen in the most strains tested.

ASSUNTO(S)

bactéria entomopatogênica entomopatogenic bacterium bioensaios ciencias agrarias cotonicultura e controle biológico bioassay cotton crop and biological control

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