Molecular characterization of the chitinase genes of native Bacillus thuringiensis isolates and their antagonistic activity against three important phytopathogenic fungi

Bacillus spp. can promote the growth of plants and reduce plant disease incidence or severity by triggering induced systemic resistance to plant pathogens. In addition, bacteria of this genus are chitinase enzyme producers. Chitinase inhibits the growth of fungi by breaking down the chitin-containing cell wall of plant pathogenic fungi. In this study, 270 native Bacillus spp., isolated from various habitats in Kayseri and Adana, Turkey, were screened by PCR for the chitinase gene and 66 of them were found to have this gene. Nine Bacillus thuringiensis (Bt) isolates showing high insecticidal activity against insect pests in our previous studies were selected from 66 isolates containing the chitinase gene. Chitinases with different molecular weights ranging from ~ 40 to 113 kDa were determined by SDS-PAGE. To determine the antagonistic effects against plant pathogenic fungi (Fusarium oxysporum f.sp. niveum, Verticillium dahliae and Aspergillus niger), a dual culture assay was used with nine native and two standard strains of Bt, and radial growth inhibition was calculated as a percentage. Of all the tested isolates, SY33.3 showed the strongest antagonistic activity and thus, can be used as an effective biological control agent against plant pathogenic fungi.