Bioactivities of cry gene positive Bacillus thuringiensis (Berliner) (Bacillales: Bacillaceae) strains on Ephestia kuehniella Zeller, 1879 and Plodia interpunctella (Hübner, 1813) (Lepidoptera: Pyralidae)

Bacillus thuringiensis is the bacterium most commonly used for biopesticide production due to parasporal crystal formation during its growth cycle. As a consequence of repeated use, B. thuringiensis biopesticides may cause the development of resistance in the pests. Therefore, it is necessary to explore new B. thuringiensis strains with a certain degree of bioactivity. In this study (2012-2013), the bioactivity of native B. thuringiensis strains from the Aegean Region of Turkey were tested against second instar larvae of Ephestia kuehniella and Plodia interpunctella . The bioactivity of 21 B. thuringiensis strains with cry1 , cry2 or cry9 gene was determined as percent mortality according to Abbott’s formula . The highest mortality rates were 42 and 63% in E. kuehniella and P. interpunctella , respectively. These mortality rates were equal to or 1.8 times greater than that of B. thuringiensis subsp. kurstaki . In addition, plasmid profiles of B. thuringiensis strains changed between 5-18 kb . Moreover, SDS-PAGE analysis of the most toxic strains indicated the presence of Cry1 and Cry2 proteins . Two different cry2 gene profiles containing either cry2Aa1 or combination of cry2Aa1 and cry2Ab2 genes were detected by PCR analysis . In addition, partial DNA sequence analysis of cry2A genes indicated phylogenetic differences among the toxic strains and B. thuringiensis subsp. kurstaki . As a result, these B. thuringiensis strains may be used to control both E. kuehniella and P. interpunctella as alternative biopesticides in cases of insect resistance to  currently used B. thuringiensis preparations.