For example, under ideal conditions, pyramided crops that produce two or more distinct toxins that kill the same pest can substantially slow the evolution of pest resistance. However, the problem is that these strategies are often based largely on assumptions. Strategies, such as high-dose toxin expression, refuge areas, pyramids, mosaic, and rotation, have been employed in an attempt to delay resistance. Both agribusinesses and regulatory agencies would like to prevent or delay the evolution of resistance in targeted pests to insecticidal Cry toxins. Ī variety of target insects have developed resistance to Bt transgenic crops in the field. These transgenic crops express the proteins in planta and, thereby have led to some agronomic, environmental, and economic benefits compared to conventional crops. In the last two decades, biotechnology has allowed for the expression of these proteins directly in crop plants. Our result highlights the need to better understand the biological factors leading to insecticidal protein resistance and to develop IRM strategies against target insects.īacillus thuringiensis (Bt)-derived crystal proteins, so-called “Cry toxins”, have had over 50 years of safe use as foliar insecticides. Our results suggest that toxins used in a rotation fashion do not work as an effective strategy in delaying ACB resistance evolution to Cry toxins over one-toxin exposure. Furthermore, the evolution of ACB to the Cry1Ab toxin develops faster when Cry1F or Cry1Ie is present, as compared to Cry1Ab exposure only. We found that rotation of multiple toxins did not slow the evolution of resistance to Cry1F or Cry1Ie. We investigated the proteins Cry1Ab, Cry1F, and Cry1Ie, which are widely utilized for commercial insect control. Here, we designed laboratory evolution experiments to test whether Bt-based insecticidal proteins with different MoAs used in rotation could delay resistance from developing in Asian corn borer (ACB), Ostrinia furnacalis. The efficacy of a rotation strategy is reliant on mathematical models based on biological assumptions. This can take the form of planting crops in a rotation pattern when different crops expressing single toxins are available on the market. Data generated from the study will assist in the development of sustainable resistance-management strategies.Ī common strategy for delaying the evolution of resistance to transgenic crops that produce insecticidal proteins from Bacillus thuringiensis is to ensure that insect pests are exposed to multiple toxins with different mechanisms of action (MoAs). The present study suggested that rotation of multiple toxins did not slow the evolution of resistance to Cry1F or Cry1Ie. The species tested was the Asian corn borer, Ostrinia furnacalis (Guenée), the most economically important species of maize pest in Asia. Two (Cry1Ab-Cry1F, Cry1Ab-Cry1Ie) or three (Cry1Ab–Cry1F–Cry1Ie) toxin alternation regimes were tested to imitate two or three single-gene crops in a rotation fashion. To test this prediction, we set out laboratory selection experiments under the alternation of multi-toxins by mixing individual toxins (Cry1Ab, Cry1F, and Cry1Ie) in an artificial diet to emulate single-gene Bt maize plants. A simulation model suggested that the rotation of different single-gene crops planted in subsequent seasons has the potential to delay resistance. Delaying or preventing the evolution of resistance to Bacillus thuringiensis (Bt) toxins produced by transgenic crops in insect pests is a major challenge for agriculture.
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