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

Abstract

Bacillus thuringiensis (Bt) has a significant 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 fig quality and cultivation. The aim of this work was to isolate, characterize, and determine the lepidopteran toxicity of Bt obtained from fig groves in Aydın Province. A total of 606 colonies (out of 1167) obtained from 380 samples were identified as Bt based on parasporal crystal formation. The 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 fig pests were further characterized based on specific cry gene content, protein profiles, and PCR-RFLP analysis. Among cry1 genes, the cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C, cry1D, and cry1Ea genes were the most frequent (100%). Protein profiles of isolates toxic to C. cautella were different from those of isolates toxic to C. hemipterus. PCR-RFLP analysis indicated that toxic isolates differed from the reference strain with respect to cry1 type gene. Finally, it was concluded that Bt strains isolated from fig groves showed high level of toxicity against fig pests. These 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.

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

“…In fact, we showed that the strains 13 MY and 42 MY contain cry1 gene different from that of B. thuringiensis subsp. kurstaki in our previous study (Alper et al, 2014). Similarly, partial DNA sequence analysis of cry2A genes was different from that of the reference strain according to phylogenetic tree in this present study.…”

“…Profiles of cry genes of the strains were identified previously (Alper et al, 2014) and are presented in Table 2. …”

“…The B. thuringiensis strains were originally obtained from fig-growing areas in Aegean Region of Turkey in an earlier study (Alper et al, 2014). The reference strain, B. thuringiensis subsp.…”

“…Preparation of spore-crystal mixtures and electrophoresis were done as described in Alper et al (2014). For electrophoresis, 5 µg spore-crystal mixture determined by Bradford assay (Bradford, 1976) was loaded per lane along with protein weight marker, SM0661 (Fermentas).…”

<b>Isolation and characterization of <i>Bacillus thuringiensis</i> strains active against <i>Elasmopalpus lignosellus</i> (Zeller, 1848) (Lepidoptera, Pyralidae)

“…According to Alper et al (2014), some strains that harbour the same genes may not be as effective as other toxic strains that have those same genes, indicating that these genes could be poorly expressed because of a weak promoter in the strains. Thus, poor expression of the cry genes in the BR78 and S1302 isolates could explain the cry genes in the genetic profile but not in the protein profile.…”