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GM Crops: Ecological Dimensions

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Transgenic (genetically modified) crops producing insecticidal toxins derived from Bacillus thuringiensis (Bt) bacteria have been scrutinised by government agencies, scientists and the public for their potential to negatively impact non-target organisms in or surrounding agricultural habitats. While several crops have been engineered to express one or more Bt toxins, it is such com (= maize) varieties that have had commercial success. Many strains of Bt exist, each producing one or more toxic crystalline (Cry) proteins, but the deleterious effects of each toxin are usually confined to a few related species in a single order of insects. The species to which an ingested Bt toxin may be harmful is defined by the specific pH levels, enzymes, and gut receptors required to solubilise, activate and bind the toxin. The first commercial Bt-com varieties were produced to control the European com borer ( Ostrinia nubilalis) and other closely related pest moths, making any organism outside this group a non-target species. However, the specific requirements for a toxin to function have caused non-target research to be focused on herbivores, specifically non-pest moths and butterflies. The possibility that use of Bt crops negatively impacts predators and parasitoids that help regulate pest populations is considered elsewhere in this volume.


This chapter is from Hellmich, R. L., Prasifka, J. R. & Anderson, P. L. Effects of Bt plants on non-target herbivores. In GM Crops: Ecological Dimensions, edited by H.F. van Emden & A. J. Gray. Association of Applied Biologists, Wellesbourne, UK, pp. 75–80. 2004.


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