Identification of Some cry1 Genes and Toxicity Determination in Bacillus thuringiensis Isolates Obtained from Mills and Warehouses in Turkey

Abstract

Fifty four isolates of Bacillus thuringiensis (Bt) were isolated from grain products and dust in flour mills and warehouses in Turkey. These isolates were analyzed to determine the presence of cry1 type genes using specific primers for cry1Ab/Ac, cry1Ac, cry1Ad, cry1B, and cry1D genes. PCR results showed that ND7.2 and ND11.3 isolates harbored cry1Ab/Ac, cry1Ac, cry1Ad, cry1B, and cry1D genes. SDS-PAGE profile showed that local isolates produced several protein bands, with molecular masses ranging from 28 to 130 kDa. The insecticidal activity of these isolates against Ephestia kuehniella and Plodia interpunctella larvae was tested. Percentage mortalities against E. kuehniella and P. interpunctella at the lowest concentration (1mg/ml) ranged between 24 to 56%, and 27 to 73%, respectively. Respective mortalities at the highest used concentration (4mg/ml), ranged from 58 to 73%, and 53 to 97%. LC50 for the tested isolates were ranged from 1.631 to 2.649 and 1.675 to 2.665 mg/ml for E. kuehniella and P. interpunctella, respectively, while the corresponding LC50 for Btk were 1.111 and 1.157 mg/ml for both insects. Variations in efficacy of isolates suggest that insecticidal potency of the isolates is not directly related to their cry gene content. However, the presence of three of the investigated cry1 genes (cry1Ad171, cry1Ac180 and cry1A216) in all Bt isolates under investigation indicated that these isolates can be used to produce spore-crystal mixture for controlling lepidopteran pests.