Canadian Forest Service Publications
Relevance of Bt toxin interaction studies for environmental risk assessment of genetically modified crops. 2015. De Schrijver, A.; De Clercq, P.; de Naagd, R.; van Frankenhuyzen, K. 2015. Plant Biotechnology Journal 13: 1221-1223.
Available from: Great Lakes Forestry Centre
Catalog ID: 36437
CFS Availability: PDF (request by e-mail)
Plain Language Summary
Economically important crops like corn and cotton are genetically altered to ward off pest insects so that farmers do not have to spray insecticides. This is most commonly achieved by inserting a gene from an insect-killing bacterium (Bt), which expresses an insecticidal protein in tissues of the crop. Large-scale use of Bt crops for more than two decades has forced some pest insects to become immune to the toxin protein. Firms like Monsanto are now making crops that produce several Bt toxins at once, which makes it harder for pest insects to become immune. Approval of Bt crops by regulatory agencies around the world requires demonstration that the GM crop does not have negative effects on the crop ecosystem, for example by inadvertently killing non-pest insects that may be beneficial. Regulatory agencies typically use published data on insecticidal activity of single proteins to evaluate the environmental risk of Bt crops. The concern is that crops expressing multiple proteins could have impacts on non-pest insects that are more severe than the combined effects of individual toxins. In this paper we review published data on how Bt toxins interact in affecting target and nontarget insects. We conclude that not enough is known about Bt toxin interactions to confidently predict the impact of specific toxin combinations on non-pest species and recommend that regulatory agencies include a requirement for direct testing on selected species.
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