Selection of Brazilian Bacillus thuringiensis Strains for Controlling Diamondback Moth on Cabbage in a Systemic Way

Plutella xylostella (L.) (Lepidoptera: Plutellidae) is a pest of great economic importance, due to losses caused in brassica crops worldwide. The control of this pest is hindered by the selection of insects resistant to various chemicals and by its cryptic habit. The aim of this work was to select a new B. thuringiensis strain with potential to control this insect pest in a systemic way because of its cryptic habit between the leaves of the cabbage, as a new control strategy. The strains were characterized by morphological, entomophatogenic, biochemical and molecular methods. No significant differences were observed in the CL 50 values of S1905, S2122 and S2124 strains when compared to Btk HD-1 standard. The strains S1905 and S2124 had presented two main proteins with 130 and 65 kDa, while S2122 presented only 130 kDa protein. The strains presented PCR products with expected sizes for detection of some genes cry1 and cry2 and bipyramidal, spherical, and cuboidal crystals. The strains show some different cry1 genes that it's very important to develop new products with different toxins to be used in management of P. xylostella resistance to B. thuringiensis products and as a systemic bioinsecticide.