Isolamento, avaliação e caracterização de Bacillus thuringiensis, com potencial para controle de diptera e lepidoptera

Abstract

Among the insects that harm the socioeconomic development of Serra Gaúcha, exist the dipterous, of the family Simuliidae that, due to its hematofagic process, cause discomfort and allergies to active rural tourists. In the agricultural regions, the lepidopterous, of the family Noctuidae, constitute curses of several cultures, constituting an economical prejudice. Seeking to reduce the use of chemical substances in the control of insects, this work is aimed at isolating the bacteria Bacillus thuringiensis (Bt) for the application of regional programs of Simulids and Noctuids pest control. Samples of insects and of soil of rural and urban areas were collected in the municipal districts of the specific area. Were obtained 721 bacterial colonies, from which, 231 (32,03%) were identified as Bt. Patogenicity tests against Culex quinquefasciatus and Anticarsia gemmatalis were executed with 84 bacteria isolated from soil and 28 bacteria isolated from insects that had a larger capacity of cellular reproduction. The results indicated that the isolated bacteria recovered from the insects were more specific, considering that a larger number of bacteria coming from the soil were more toxic for both species, showing a wider spectrum of entomopatogenic. Just one of the isolated 12 bacteria presented a similar value of CL50 than the one obtained with the lineage pattern IPS-82, in relation of the mortality rate of larvae of C. quinquefasciatus. The profile of the protoxins of one of the isolated ones is characterized by SDS-PAGE, demonstrating that two isolated bacteria obtained from the dipteran, had a similar profile as lineage IPS-82, while two others isolated from the soil, with bands between 65 and 130 kDa, were more toxics for lepidopteran and the two obtained from the soil and three obtained from of insects, and presented one band of approximately 120 kDa, being more effective against caterpillars.