Toxicity of Bacillus thuringiensis Cry proteins to Helicoverpa armigera (Lepidoptera: Noctuidae) in South Africa.
The susceptibility of one of the most important pests in southern Africa, Helicoverpa armigera (Lepidoptera: Noctuidae), to Bacillus thuringiensis Cry proteins was evaluated by bioassay. Cry proteins were produced in Escherichia coli BL21 cells that were transformed with plasmids containing one of six cry genes. The toxicity of each Cry protein to H. armigera larvae was determined by the diet contamination method for second instar larvae and the droplet feeding method for neonate larvae. For each of the proteins, dose-mortality and dose-growth inhibition responses were analyzed and the median lethal dose (LD(50)) and median inhibitory dose (ID(50)) determined. Second instar larvae were consistently less susceptible to the evaluated Cry proteins than neonate larvae. The relative toxicity of Cry proteins ranked differently between neonate larvae and second instar larvae. On the basis of the LD(50) and ID(50) values, Cry1Ab, Cry1Ac, and Cry2Aa were the most toxic of the evaluated proteins to H. armigera larvae. The study provides an initial benchmark of the toxicity of individual Cry proteins to H. armigera in South Africa.
School of Molecular and Cell Biology, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa.
Hua
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Li
Gustav
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Bouwer
D000367:Age Factors; D000818:Animals; D001413:Bacillus thuringiensis; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000633:toxicity*; D004731:Endotoxins / Q000633:toxicity*; D006460:Hemolysin Proteins / Q000633:toxicity*; D020128:Inhibitory Concentration 50; D007306:Insecticides / Q000633:toxicity*; D007814:Larva / Q000187:drug effects / Q000254:growth & development / Q000382:microbiology; D007928:Lethal Dose 50; D009036:Moths / Q000187:drug effects* / Q000254:growth & development / Q000382:microbiology; D010572:Pest Control, Biological; D023382:Toxicity Tests, Acute
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis