Bacillus thuringiensis: molecular characterization, ultrastructural and nematoxicity to meloidogyne sp..

ABSTRACT Nematodes are important pests in agriculture, causing losses that reach $ 125 million annually. In addition to chemical control, biological control using strains of the bacterium Bacillus thuringiensis has been studied. The aim of this study was to evaluate the toxicity of new strain of B. thuringiensis to Meloidogyne sp., in laboratory and in greenhouse, as well as the content of cry genes and structural and ultrastructural analyzes. The MTox 1886-2 isolate was used, at different concentrations, to evaluate the toxicity to juveniles (J2) of Meloidogyne in laboratory, and to eggs and juveniles in greenhouse. Differential Interference Contrast Microscopy, Scanning Electron Microscopy and molecular characterization by PCR were performed. Laboratory results showed 96% of corrected mortality of nematodes treated with 1 x 1010cells/mL, getting a LC50 of 2.6x107 cells/mL. In greenhouse, MTox 1886-2 showed 36% reduction in the number of nematodes, compared to control, and presented better results in the weight of the aerial part and the roots of lettuce plants. Structural and ultrastructural analysis of the spore-crystal mixture of the strain revealed the presence of a bipyramidal crystal protein. The analysis of the content of cry genes by PCR amplification resulted in a fragment of approximately 1000 bp which was sequenced revealing a target gene of the cry1D subfamily. Thus, the prospects for this study is the use of this gene in the development of genetically modified plants, granting resistance to nematodes, or the use in new commercial formulations.