The toxicity of the Bacillus thuringiensis (Bt) toxin Cry3Aa-originally used against the main potato pest, the Colorado potato beetle, Leptinotarsa decemlineata-was verified on this species and then evaluated against the Egyptian armyworm, Spodoptera littoralis, which is a pest of several economically important plants. Larvae of S. littoralis were fed a semi-artificial diet supplemented either with a recombinant or with a natural Bt toxin Cry3Aa and with the genetically engineered (GE) potato of variety Superior NewLeaf (SNL) expressing Cry3Aa. Cry3Aa concentration in the diet and the content in the leaves were verified via ELISA (enzyme-linked immunosorbent assay) and HPLC (high-performance liquid chromatography) during and at the end of the experiments. The biological effectiveness of the coleopteran-specific Cry3Aa with previous reports of activity against S. littoralis was tested on five different populations of S. littoralis larvae by monitoring 13 parameters involving development from penultimate instar, weight, the efficiency of food conversion to biomass, ability to reproduce, and mortality. Although some occasional differences occurred between the Cry3Aa treatments and control, any key deleterious effects on S. littoralis in this study were not confirmed. We concluded that the Cry3Aa toxin appears to be non-toxic to S. littoralis, and its practical application against this pest is unsuitable.

• Keywords
• Leptinotarsa decemlineata, Spodoptera littoralis, Superior NewLeaf, biological control, integrated pest management, natural Cry3Aa, recombinant Cry3Aa,
• Publication type
• Journal Article MeSH

Genetically engineered (GE) crops with stacked insecticidal traits expose arthropods to multiple Cry proteins from Bacillus thuringiensis (Bt). One concern is that the different Cry proteins may interact and lead to unexpected adverse effects on non-target species. Bi- and tri-trophic experiments with SmartStax maize, herbivorous spider mites (Tetranychus urticae), aphids (Rhopalosiphum padi), predatory spiders (Phylloneta impressa), ladybeetles (Harmonia axyridis) and lacewings (Chrysoperla carnea) were conducted. Cry1A.105, Cry1F, Cry3Bb1 and Cry34Ab1 moved in a similar pattern through the arthropod food chain. By contrast, Cry2Ab2 had highest concentrations in maize leaves, but lowest in pollen, and lowest acquisition rates by herbivores and predators. While spider mites contained Cry protein concentrations exceeding the values in leaves (except Cry2Ab2), aphids contained only traces of some Cry protein. Predators contained lower concentrations than their food. Among the different predators, ladybeetle larvae showed higher concentrations than lacewing larvae and juvenile spiders. Acute effects of SmartStax maize on predator survival, development and weight were not observed. The study thus provides evidence that the different Cry proteins do not interact in a way that poses a risk to the investigated non-target species under controlled laboratory conditions.

• Keywords
• Bt maize, Cry proteins, arthropod foodweb, environmental risk assessment, genetically modified crops, natural enemies,
• MeSH
• Bacillus thuringiensis MeSH
• Bacterial Proteins genetics   MeSH
• Arthropods * MeSH
• Endotoxins genetics   MeSH
• Plants, Genetically Modified genetics   MeSH
• Hemolysin Proteins genetics   MeSH
• Zea mays genetics   MeSH
• Larva MeSH
• Food Chain * MeSH
• Bacillus thuringiensis Toxins MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Bacterial Proteins MeSH
• Endotoxins MeSH
• Hemolysin Proteins MeSH
• insecticidal crystal protein, Bacillus Thuringiensis MeSH Browser
• Bacillus thuringiensis Toxins MeSH