title: Efficiency and midgut histopathological effect of the newly isolated Bacillus thuringiensis KS δ-endotoxins on the emergent pest Tuta absoluta.
abstract: Tuta absoluta (Povolny, 1994) is a devastating moth to the Solanaceae plants. It is a challenging pest to control, especially on tomatoes. In this work, we studied the entomopathogenic activity of the Cry-forming δ-endotoxins produced by Bacillus thuringiensis strain KS and B. thuringiensis kurstaki reference strain HD1 against T. absoluta. These strains carried the cry2, cry1Ab, cry1Aa / cry1Ac, and cry1I genes, and KS also carried a cry1C gene. The δ-endotoxins of KS were approximately twofold more toxic against the third instar larvae than those of HD1, as they showed lower 50% and 90% lethal concentrations (0.80 and 2.70 μg/cm² (δ-endotoxins/tomato leaf)) compared with those of HD1 (1.70 and 4.50 μg/cm²) (p < 0.05). Additionally, the larvae protease extract showed at least six caseinolytic activities, which activated the KS and HD1 δ- endotoxins, yielding the active toxins of about 65 kDa and the protease-resistant core of about 58 kDa. Moreover, the histopathological effects of KS and HD1 δ-endotoxins on the larvae midgut consisted of an apical columnar cell vacuolization, microvillus damage, and epithelial cell disruption. These results showed that the KS strain could be a candidate for T. absoluta control.
authors.affiliation: Biopesticides Team (LPAP), Centre of Biotechnology of Sfax, University of Sfax, 3018 Sfax, Tunisia.
authors.forename: Kaïs
authors.initials: K
authors.lastname: Jamoussi
authors.forename: Sameh
authors.initials: S
authors.lastname: Sellami
authors.forename: Zina
authors.initials: Z
authors.lastname: Nasfi
authors.forename: Saloua
authors.initials: S
authors.lastname: Krichen-Makni
authors.forename: Slim
authors.initials: S
authors.lastname: Tounsi
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000472:pathogenicity*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000633:toxicity*; D001681:Biological Assay; D004731:Endotoxins / Q000633:toxicity*; D041981:Gastrointestinal Tract / Q000187:drug effects / Q000382:microbiology / Q000473:pathology; D006460:Hemolysin Proteins / Q000633:toxicity*; D006651:Histocytochemistry; D007814:Larva / Q000187:drug effects / Q000382:microbiology; D007915:Lepidoptera / Q000187:drug effects* / Q000382:microbiology; D016019:Survival Analysis
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis