Isolation and Characterization of Bacillus thuringiensis Isolates from Hazelnut Orchards in Türkiye

The entomopathogenic bacterium, Bacillus thuringiensis (Bt) has been one of the important sources of biopesticides and applied in biological control against agricultural pests for many decades. Isolation and characterization of Bt isolates from different habitats around the world allow the discovery of new Bt strains with high insecticidal activity and the ability to cope with the problem of resistance to pesticides. The goal of this study is to obtain a new Bt collection from hazelnut orchards in Türkiye and to investigate the insecticidal cry1 gene content of these isolates and to reveal their protein profiles and serovars. Bt was isolated from 28 soil and leaf samples collected from 14 different locations in Ordu province. Of the 302 Bt-like colonies examined, 63 were observed to carry crystals in the form of parasporal inclusions and the Bt index was found to be 0.21. The presence of cry1 gene in Bt isolates were analyzed using Polymerase chain reaction (PCR) analysis. The results showed that 21 isolates (33%) were positive for cry1 gene. When the protein profiles of the Bt isolates were examined by SDS-PAGE analysis, bands of 130 kDa, 60 kDa, 43 kDa and larger than 200 kDa were obtained in most of the samples. In order to reveal the serovar types of Bt isolates, hag gene was amplified and the PCR products were further sequenced. The analysis identified the Bt tochigiensis and Bt xiaguangiensis serovars among the screened Bt isolates. This study reports the isolation and characterization of a novel collection of B. thuringiensis isolates from hazelnut orchards in Ordu province (Northern Türkiye), identifying the cry1 gene carrying strains with potential toxicity against some lepidopteran pests.