title: Effects of Bt maize on the herbivore Spodoptera littoralis (Lepidoptera: Noctuidae) and the parasitoid Cotesia marginiventris (Hymenoptera: Braconidae).
abstract: Recent studies have shown that transgenic insect resistant plants can have negative effects on non-target herbivores as well as on beneficial insects. The study of tritrophic interactions gives insight into the complex mechanisms of food webs in the field and can easily be incorporated into a tiered risk assessment framework. We investigated the effects of transgenic maize (Zea mays) expressing insecticidal proteins derived from Bacillus thuringiensis (Bt maize) on Spodoptera littoralis, a non-target herbivore, and on the hymenopteran parasitoid Cotesia marginiventris. In a laboratory study, S. littoralis larvae were reared for their whole lifespan on a mixture of leaves and stems from 2-4-week old Bt maize plants. S. littoralis survival, developmental times and larval weights were significantly affected by Bt maize diet. However, adult moths, which survived development on Bt maize, were the same size as the adults from the control group. C. marginiventris survival, developmental times and cocoon weights were significantly negatively affected if their S. littoralis host larva had been fed Bt maize. ELISA tests confirmed that S. littoralis larvae ingest high amounts of CrylA(b) toxin while feeding on Bt maize. In S. littoralis pupae and in C. marginiventris cocoon silk, only traces of the toxin could be detected. No toxin was found in S. littoralis and C. marginiventris adults. Thus the toxin is not accumulating in the trophic levels and in fact appears to be excreted. Our results suggest that the effects on C. marginiventris when developing in susceptible S. littoralis larvae are indirect (host mediated). The biological relevance of those results and the significance of this study in risk assessment are discussed.
authors: School of Biological Sciences, University of Southampton, Basset Crescent East, Southampton SO16 7PX, UK.
authors: Eva
authors: E
authors: Vojtech
authors: Michael
authors: M
authors: Meissle
authors: Guy M
authors: GM
authors: Poppy
mesh_terms: D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics / Q000493:pharmacokinetics* / Q000494:pharmacology; D001427:Bacterial Toxins / Q000235:genetics / Q000493:pharmacokinetics* / Q000494:pharmacology; D004731:Endotoxins / Q000235:genetics / Q000493:pharmacokinetics* / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005247:Feeding Behavior; D020387:Food Chain; D006460:Hemolysin Proteins; D006927:Hymenoptera / Q000472:pathogenicity; D007300:Insect Control; D007814:Larva / Q000254:growth & development; D030821:Plants, Genetically Modified / Q000737:chemistry / Q000235:genetics*; D018570:Risk Assessment; D018411:Spodoptera / Q000469:parasitology*; D013534:Survival; D003313:Zea mays / Q000737:chemistry / Q000235:genetics* / Q000382:microbiology
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis