Molecular characterisation and screening for сry genes of native Bacillus thuringiensis strains from Kazakhstan

The current study aimed to characterise indigenous <i>Bacillus thuringiensis</i> (Bt) strains for their potential use in agricultural broad-spectrum pest control. Twenty-nine Bt strains were isolated from soil in southeastern Kazakhstan. All isolates were Gram-positive and formed endospores. Species identification was conducted by sequencing the <i>gyraseB</i> (<i>gyrB</i>) gene. The nucleotide sequences of the amplified <i>gyrB</i> gene regions were compared with those in the NCBI database, confirming that the isolates were native Bt strains with high homology to known Bt strains (99–100%). In addition, the strains were screened for the presence of genes encoding 11 different crystalline endotoxins using PCR with universal primer pairs. The PCR results showed the distribution frequencies of <i>cry</i>, <i>cyt</i>, and <i>vip</i> genes among the strains: <i>cry1</i> (100%), <i>vip3</i> (100%), <i>cry2</i> (83.3%), <i>cry4</i> (20%), and <i>cyt1</i> (30%). PCR revealed diverse gene profiles among the Bt strains, with 5 distinct profiles identified. Regarding insecticidal activity, strains Bt8, Bt11, Bt26, and Bt28 demonstrated high pathogenicity, with mortality rates ranging from 97% to 100% against codling moth caterpillars, outperforming other Bt isolates.