摘要 : The entomopathogenic bacterium <i>Bacillus thuringiensis</i> is a control agent with toxic and environmental characteristics that allows the control of pest insects according to the Integrate Pest Management (IPM) precepts. In ord... 展开 The entomopathogenic bacterium <i>Bacillus thuringiensis</i> is a control agent with toxic and environmental characteristics that allows the control of pest insects according to the Integrate Pest Management (IPM) precepts. In order to find new strains, potentially toxic to <i>Sitophilus oryzae</i> L. 1763 (Coleoptera: Curculinidae), 1.073 strains of <i>B. thuringiensis</i> from parts of Brazil were used. Genetic material was extracted with InstaGene Matrix kit, used for the amplification of sequences in Polymerase chain reaction (PCR), and viewed in 1.5% agarose gel. The gene <i>cry35Ba</i> class was represented by 60 <i>B. thuringiensis</i> isolates (5.6%), which were then subjected to bioassays with <i>S. oryzae</i> larvae. Among the isolates studied, four caused more than 50% mortality in pathogenicity tests, and the isolates 544 and 622 were the most virulent, as determined by CL₅₀ estimates. The four toxic isolates had spherical, bi-pyramidal and cuboid crystals, and a 44-kDa protein was found in sodium dodecyl sulphate - polyacrylamide gel electrophoresis (SDS-PAGE), which coded for the product of <i>cry35Ba</i> genes. These data demonstrate the potential of <i>B. thuringiensis</i> for the management of <i>S. oryzae</i> larvae.Digital Object Identifier http://dx.doi.org/10.1590/S0103-90162010000400015 收起