Seleção de genes cry de Bacillus thuringiensis que codificam proteínas tóxicas a insetos-praga da cultura do arroz / Screening of bacillus thuringiensis cry genes which codify toxic proteins to the insects pest of rice-crop

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

This work, which is part of the Preservation and Management of Ecossystems and Wild Life research line, has as its aim the selection of the Bacillus thuringiensis cry genes that codify delta-endotoxins active against rice pest insects, representatives of the Lepidoptera (Spodoptera frugiperda, Noctuidae), Coleoptera (Oryzophagus oryzae, Curculionidae) and Hymenoptera (Acromyrmex lundi, Formicidae) orders, which can be used for the management of those insect populations. In order to select B. thuringiensis active against S. frugiperda and O. oryzae there have been used isolates from soil samples that had been collected in agricultural areas in Rio Grande do Sul, and they had gone through the prediction of insecticidal activity by the Polimerase Chain Reaction (PCR), with the primers that magnify DNA fragments which correspond to lepidopterans-specific cry1, cry2 and cry9 genes and coleopterans-specific cry3, cry7 and cry8 genes. The preselected isolates during this phasis of the research, have been assessed regarding in vivo toxicity, by means of bioassays. In the research against hymenopterans, B. thuringiensis isolates from leaf-cutting ants were used, seeing that they had preliminarily been assessed by bioassays against Acromyrmex lundi, in which samples that had been selected as pathogenic have gone through PCR assessment with the primers mentioned earlier. As to the isolates from soil samples, PCR results have shown the presence of eight different genetic profiles evenly distributed throughout the soil of Rio Grande do Sul, with a prevalence of cry9 genes (39.1%). B. thuringiensis protein analysis by SDS-PAGE has identified 14 families of Cry proteins, which may be codified by the genes present in analysed isolates, and unknown proteins as well, that may represent new and not yet characterized cry genes. Taking into consideration the data of the preselection by PCR, among the 46 B. thuringiensis isolates from the soil samples, 56.5 and 21.7% were potencially lepidoptera and coleoptera specific, respectively. For those isolates, during the pathogenicity assays, the highest corrected mortality was of 25.0% for S. frugiperda and of 53.4% for O. oryzae. Isolation data from leaf-cutting ants have shown 14 samples which correspond to B. thuringiensis, seeing that 42.8% are active against A. lundi, of which the corrected mortality has ranged from 14.2 to 100.0%. In those isolates, DNA fragments of cry1 (22.0%) and cry9 (67.0%) have been magnified. The results of this research have been announced in Congresses and Symposiums, seeing that one paper review and three papers with the results of the research in progress have been published in Scientific Journals.

ASSUNTO(S)

thuringiensis microbiologia lepdoptera bacillos entomologia; controle biológico; agricultura; arroz; praga; lepidoptero; zoologia; coleoptero; himenoptero coleoptera

ACESSO AO ARTIGO

Documentos Relacionados