Can pyramids and seed mixtures delay resistance to Bt crops?

Authors: CARRIERE, YVES - University Of Arizona; Fabrick, Jeffrey; TABASHNIK, BRUCE - University Of Arizona

Submitted to: Trends in Biotechnology
Publication Type: Review Article
Publication Acceptance Date: 12/16/2015
Publication Date: 3/23/2016
Publication URL: https://handle.nal.usda.gov/10113/62182
Citation: Carriere, Y., Fabrick, J.A., Tabashnik, B. 2016. Can pyramids and seed mixtures delay resistance to Bt crops? Trends in Biotechnology. 34(4):291-302. doi: 10.1016/j.tibtech.2015.12.011.

Interpretive Summary: Genetically modified or transgenic crops producing Bacillus thuringiensis (Bt) insecticidal proteins are key management tools against numerous important insect pests. Such Bt transgenic crops produce Bt toxins within the plant and selectively target insect pests while having little impact on beneficial insects or other plants or animals. Bt crops produce either a single toxin or more than one Bt toxin (called a pyramid). Bt pyramids increase the range of activity against pests and delay the development of resistance. Nevertheless, both single-toxin and pyramided Bt crops are vulnerable to the development of resistance. The use of Bt pyramids and the simultaneous planting of non-Bt crops to produce susceptible pest insects (also known as the "refuge strategy") are currently the primary strategies used to delay development of resistance to Bt crops by insect pests. Whereas five factors contribute to the durability of both single-toxin and pyramided crops, three factors contribute uniquely to the durability of pyramids. Here, we show that conditions in the field often deviate from optimal implementation of key resistance management factors for some pests and that additional management strategies to delay resistance to Bt crops are needed.

Technical Abstract: The primary strategy for delaying evolution of pest resistance to transgenic crops that produce insecticidal proteins from Bacillus thuringiensis (Bt) entails refuges of plants that do not produce Bt toxins and thus allow survival of susceptible pests. Recent advances include using refuges together with Bt crop "pyramids" involving two or more Bt toxins effective against the same pest, and planting seed mixtures of pyramided Bt and non-Bt corn plants within fields. We conclude that conditions often deviate from those favoring sustainability of pyramids and seed mixtures, particularly against pests with low inherent susceptibility to Bt toxins. For these problematic pests, promising approaches include using larger refuges and integrating Bt crops with other pest management tactics.