Distribution, occurrence of cry genes, and lepidopteran toxicity of native Bacillus thuringiensis isolated from fg tree environments in Aydın Province

Abstract

Bacillus thuringiensis (Bt) has a signifcant impact on biological pest control because of the insecticidal activity through its parasporal inclusion bodies (crystal proteins). Fig is an economically important plant in Turkey; agricultural pests result in a considerable economic loss in fg quality and cultivation. Te aim of this work was to isolate, characterize, and determine the lepidopteran toxicity of Bt obtained from fg groves in Aydın Province. A total of 606 colonies (out of 1167) obtained from 380 samples were identifed as Bt based on parasporal crystal formation. Te highest Bt index of 0.60 was observed in the Kuyucak region. A total of 288 Bt isolates were characterized in terms of cry gene content by PCR analysis. It was found that the cry1 plus cry2 genotype was the most abundant (40%) in our collection. Bioactivity tests indicated that 6 isolates exhibited high mortalities against Cadra cautella and 3 isolates were found to exhibit high toxicity against Carpophilus hemipterus. Moreover, 13 Bt isolates exhibiting toxic activity against fg pests were further characterized based on specifc cry gene content, protein profles, and PCR-RFLP analysis. Among c ry1 genes, the cry1Aa , cry1Ab , cry1Ac , cry1B, cry1C, cry1D , and cry1Ea genes were the most frequent (100%). Protein profles of isolates toxic to C. cautella were diferent from those of isolates toxic to C. hemipterus. PCR-RFLP analysis indicated that toxic isolates difered from the reference strain with respect to cry1 type gene. Finally, it was concluded that Bt strains isolated from fg groves showed high level of toxicity against fg pests. Tese strains can serve as potential biopesticides for the control of C. cautella in the region as well as alternative biopesticides in the case of pesticide resistance in insects.