Abstract
Several important crops have been engineered to express toxins of Bacillus thuringiensis (Bt) for insect control. In 1999, US farmers planted nearly 8 million hectares (nearly 20 million acres) of transgenic Bt crops approved by the EPA. Bt-transgenic plants can greatly reduce the use of broader spectrum insecticides, but insect resistance may hinder this technology. Present resistance management strategies rely on a “refuge” composed of non-Bt plants to conserve susceptible alleles. We have used Bt-transgenic broccoli plants and the diamondback moth as a model system to examine resistance management strategies. The higher number of larvae on refuge plants in our field tests indicate that a “separate refuge” will be more effective at conserving susceptible larvae than a “mixed refuge” and would thereby reduce the number of homozygous resistant (RR) offspring. Our field tests also examined the strategy of spraying the refuge to prevent economic loss to the crop while maintaining susceptible alleles in the population. Results indicate that great care must be taken to ensure that refuges, particularly those sprayed with efficacious insecticides, produce adequate numbers of susceptible alleles. Each insect/Bt crop system may have unique management requirements because of the biology of the insect, but our studies validate the need for a refuge. As we learn more about how to refine our present resistance management strategies, it is important to also develop the next generation of technology and implementation strategies.
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Acknowledgements
We thank Melissa Birkett, Hilda Collins, Jennifer Cooley, Bryna Mitchell, Sabrina Siebert, Powell Smith, and Joe Zhao for their assistance in this project. The research was funded by USDA NRI grants 91-37302-6199, 93-01977 and 95-37302-1783.
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Shelton, A., Tang, J., Roush, R. et al. Field tests on managing resistance to Bt-engineered plants. Nat Biotechnol 18, 339–342 (2000). https://doi.org/10.1038/73804
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DOI: https://doi.org/10.1038/73804
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