Response of larval Ephestia kuehniella (Lepidoptera: Pyralidae) to individual Bacillus thuringiensis kurstaki toxins mixed with Xenorhabdus nematophila

• Published in: Journal of invertebrate pathology 2013-09, Vol.114 (1), p.71-75
• Main Authors: BenFarhat, Dalel, Dammak, Mariam, Khedher, Saoussen Ben, Mahfoudh, Salima, Kammoun, Schema, Tounsi, Slim
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Animals; Applied ecology; Bacillus thuringiensis; Bacillus thuringiensis subsp. kurstaki; Bacterial Proteins - toxicity; Biological and medical sciences; crystals; Delta-endotoxin; delta-endotoxins; Ecotoxicology, biological effects of pollution; Endotoxins - toxicity; Ephestia kuehniella; Fundamental and applied biological sciences. Psychology; Hemolysin Proteins - toxicity; Insecta; insecticidal properties; insects; Invertebrates; Larva - drug effects; Larva - growth & development; Larva - microbiology; larvae; Moths - drug effects; Moths - growth & development; Moths - microbiology; Pest Control, Biological; receptors; spores; synergism; Toxicity; Toxicity Tests; Xenorhabdus; Xenorhabdus nematophila
• ISSN: 0022-2011; 1096-0805
• DOI: 10.1016/j.jip.2013.05.009

[Display omitted] •Xenorhabdus cells did not kill E. kuehniella but they stopped its growth.•Spore-crystal of BNS3 was more active than Xenorhabdus cells against E. kuehniella.•No significant improvement of toxicity was detected between BNS3 and Xenorhabdus.•Significative improvement of larvae growth inhibition when Xenorhabdus was used with Cry1Ac or Cry2Aa.•None of the individual toxins are as toxic to E. kuehniella as the parental strain. Bacillus thuringiensis kurstaki strain BNS3 produces parasporal crystals formed by Cry1Aa, Cry1Ac and Cry2Aa delta-endotoxins. In a previous work, we showed that the latter exhibited individually, a weak insecticidal activity against Ephestia kuehniella. In order to improve their toxicities, we studied the combined effect of each delta-endotoxin with X. nematophila cells on E. kuehniella larvae growth. Xenorhabdus cells were used in combination with spore crystal mixture of the wild strain BNS3, known to be active against E. kuehniella, but no improvement in toxicity was observed. This could be due to the high efficiency of BNS3 crystals against this insect. However, when X. nematophila was combined with each of Cry1Aa, Cry1Ac and Cry2Aa, improvement of toxicity was noticed. The best improvements were obtained with Cry1Ac and Cry2Aa, which are more toxic to E. kuehniella than Cry1Aa. The difference in toxicity improvement was attributed to the low affinity of Cry1Aa to BBMV receptors, compared to those of Cry1Ac and Cry2Aa. This synergism between Cry toxins and Xenorhabdus cells could be exploited on control target insect, particularly in case of resistance to Cry toxins.