Diversity of coleopteran-specific cry genes of Bacillus thuringiensis strains isolated from soil of some east and south regions of Iran

Abstract

Isolates were identified by molecular and morphological tests, including coleopteran-specific cry genes in the Iranian native Bacillus thuringiensis collection. Spherical and irregular shapes were observed to be the most frequent shapes using Coomassie brilliant blue staining. PCR analysis with universal and specific primer pairs was used to detect coleopteran-specific cry genes such as cry1I, cry3, cry7, cry18, and cry26. All the isolates contained at least one active coleopteran-cry gene, while the most abundant isolates had cry26 and cry18 genes. The patterns of protein size were characterized in addition to their insecticidal activity against third-instar larvae of Tribolium castaneum. Protein profiles produced bands that varied from 14-180 kDa. Four native isolates containing coleopteran-active cry genes displayed higher activity against T. castaneum larvae than B. thuringiensis subspecies galleriae as a reference strain. The median lethal concentration (LC50) of the most pathogenic isolate, PS1078, was 2.72 × 106 spores/ml. Its 16S rDNA gene sequence analysis demonstrated similarity to B. thuringiensiss subspecies galleriae. The characterization of isolates provided useful data for selecting new isolates to expand novel bio-insecticidal products.

Keywords

• bacillus thuringiensis
• coleopteran-specific cry genes
• tribolium castaneum
• plasmid
• protein profiles