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

The current study aimed to characterise indigenous Bacillus thuringiensis (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 gyraseB (gyrB) gene. The nucleotide sequences of the amplified gyrB 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 cry, cyt, and vip genes among the strains: cry1 (100%), vip3 (100%), cry2 (83.3%), cry4 (20%), and cyt1 (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.