Genetic Diversity of Native Bacillus thuringiensis Strains Isolated from Soil of Different Localities in Mali and their cry Gene Profile

Aims: To determine the genetic diversity of Bacillus thuringiensis strains isolated from soils of different locality in Mali, and select strains with cry1F, cry1B and cry1C genes to control caterpillars and strains with cry2 gene against African rice gall midge.

Study Design: Strains of Bacillus thuringiensis (Bt) used in this study belong to collection of Laboratory of Research in Microbiology and Microbial Biotechnology (Laborem-Biotech) and that isolated from different ecological environment of Mali. Bt strains used as positive controls were kindly provided by Dr. Fernando Hercos Valicente from Embrapa Milho e Sorgo (Brazil).

Methodology: The total DNA of the native B. thuringiensis and reference strains were extracted from overnight grown culture. Gene identification was performed by amplification (PCR) of DNA of Bt strains using specific primers. The gel revelation was performed using ethidium bromide and the gel photography was performed using an E-Box VX2 system, Version 15.06.

Results: Native B. thuringiensis strains studied, showed high genetic diversity. 48,3% of the studied B. thuringiensis strains of the collection carry cry1 gene, 49,06% of them harbor both cry1 and cry2 gene, 5.7% of the native Bt strains didn’t react with any cry1 and cry 2 specific primers and 94.3% of the strains produce different PCR products. The analysis of cry1 positive B. thuringiensis showed sub-group frequencies of 7.6% for cry1F and 3.8% for cry1B and cry1C. In native Bt strains of our collection, the cry2 gene was always present with one or two cry1 sub-group(s).

Conclusion: In this study, high genetic diversity in the native Bt strains from the bacterial collection in Mali was observed. Most of the native Bt strains studied harbor the cry1 gene only. In the cry1 gene profile, the cry1F sub-group was found to be the most frequently detected. None of studied Bt strains harbored the cry2 gene only.