Environmental impact of genetically modified crops.

Chapter 6 (Page no: 101)

Resistance management of transgenic insect-resistant crops: ecological factors.

From their introduction in 1996-2007, the genetically modified (GM) crops grown with traits for insecticide resistance (GM IR) have been predominantly maize and cotton varieties expressing Bacillus thuringiensis Cry1 toxins for the control of larval stages of relatively few key moth pest species. Resistance management strategies have been refined with the life history of such lepidopteran pests in mind. With the introduction from 2003 of Cry3, Cry34 and Cry35 toxins for coleopteran pests of maize and with an increasing range of GM IR crops and other Bt toxins being commercialized, a much wider range of insect pest species and populations will become exposed to selection. Here, we consider the influence of three broad ecological factors on the evolution and management of pest resistance to GM IR crops: population-level processes; bottom-up effects of the host plant; and top-down effects deriving from natural enemies and pathogens. The exploitation of such ecological factors in resistance management systems, developments in transgenic crops and a novel genetic method for resistance management are discussed.

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