Characterisation of novel Bacillus thuringiensis isolates against Aedes aegypti (Diptera: Culicidae) and Ceratitis capitata (Diptera: Tephridae)

•Molecular characterization of ten novel Bacillus thuringiensis strains.•Different plasmid and protein profiles compared to those of kurstaki and israelensis ones.•Diversity of the cry gene content of the studied strains.•Diversity of B. thuringiensis isolates producing spherical crystals was reflected in their insecticidal activities.

Bacillus thuringiensis is successfully used in pest management strategies as an eco-friendly bioinsecticide. Isolation and identification of new strains with a wide variety of target pests is an ever growing field. In this paper, new B. thuringiensis isolates were investigated to search for original strains active against diptera and able to produce novel toxins that could be used as an alternative for the commercial H14 strain. Biochemical and molecular characterization revealed a remarkable diversity among the studied strains. Using the PCR method, cry4C/Da1, cry30Ea, cry39A, cry40 and cry54 genes were detected in four isolates. Three strains, BLB355, BLB196 and BUPM109, showed feeble activities against Aedes aegypti larvae. Interestingly, spore-crystal mixtures of BLB361, BLB30 and BLB237 were found to be active against Ceratitis capitata with an LC50 value of about 65.375, 51.735 and 42.972 μg cm−2, respectively. All the studied strains exhibited important mortality levels using culture supernatants against C. capitata larvae. This suggests that these strains produce a wide range of soluble factors active against C. capitata larvae.

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