The characterization of selected Bacillus thuringiensis strains isolated from different Latin America countries is presented. Characterization was based on their insecticidal activity against Aedes aegypti , Culex quinquefasciatus , and Anopheles albimanus larvae, scanning electron microscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and plasmid profiles as well as PCR analysis using novel general and specific primers for cry and cyt genes encoding proteins active against mosquitoes ( cyt1 , cyt2 , cry2 , cry4A , cry4B , cry10 , cry11 , cry17 , cry19 , cry24 , cry25 , cry27 , cry29 , cry30 , cry32 , cry39 , and cry40 ). Strains LBIT315, LBIT348, and IB604 showed threefold higher mosquitocidal activity against A . aegypti and C . quinquefasciatus larvae than B . thuringiensis subsp. israelensis and displayed high similarities with the B . thuringiensis subsp. israelensis used in this study with regard to protein and plasmid profiles and the presence of cry genes. Strain 147-8906 has activity against A . aegypti similar to that of B . thuringiensis subsp. israelensis but has different protein and plasmid profiles. This strain, harboring cry11 , cry30 , cyt1 , and cyt2 genes, could be relevant for future resistance management interventions. Finally, the PCR screening strategy presented here led us to identify a putative novel cry11B gene.

Bacillus thuringiensis strains isolated from Latin American soil samples that showed toxicity against three Spodoptera frugiperda populations from different geographical areas (Mexico, Colombia, and Brazil) were characterized on the basis of their insecticidal activity, crystal morphology, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of parasporal crystals, plasmid profiles, and cry gene content. We found that the different S. frugiperda populations display different susceptibilities to the selected B. thuringiensis strains and also to pure preparations of Cry1B, Cry1C, and Cry1D toxins. Binding assays performed with pure toxin demonstrated that the differences in the toxin binding capacities of these insect populations correlated with the observed differences in susceptibility to the three Cry toxins analyzed. Finally, the genetic variability of the three insect populations was analyzed by random amplification of polymorphic DNA-PCR, which showed significant genetic diversity among the three S. frugiperda populations analyzed. The data presented here show that the genetic variability of S. frugiperda populations should be carefully considered in the development of insect pest control strategies, including the deployment of genetically modified maize in different geographical regions.