Biotechnology: Herbicide-Resistant Crops

Abstract

Transgenic, herbicide-resistant (HR) crops are planted on approximately 80% of the land covered by transgenic crops worldwide. More than 90% of HR crops are glyphosate resistant (GR); others are resistant to glufosinate. The wide-scale adoption of HR crops, largely for economic reasons, has been the most important development in weed management since the introduction of synthetic herbicides. Of much less importance have been the nontransgenic crops made resistant to acetyl-CoA carboxylase (ACCase)- and acetolactate synthase (ALS)-inhibiting herbicides by selecting for target mutations in culture. Use of GR crops (maize, cotton, soybean, sugar beet, canola, and alfalfa) has generally improved the environmental impact of weed management by reductions in tillage, fuel use, and the use of herbicides with less desirable toxicological profiles than that of glyphosate. Evolution of GR weeds is a threat to the benefits provided by GR crops. The next generation of HR crops with resistance to dicamba, 2,4-dichlorophenoxyacetic acid, and herbicidal inhibitors of hydroxyphenylpyruvate dioxygenase, ALS, and ACCase will provide tools for more diverse weed management approaches in order to mitigate and slow the evolution of herbicide resistance.