Review: Herbicide Resistance in Amaranthus tuberculatus

Amaranthus tuberculatus is the major weed species in many midwestern USA row-crop production fields, and it is among the most problematic weeds in the world in terms of its ability to evolve herbicide resistance. It has now evolved resistance to herbicides spanning seven unique sites of action, with populations and even individual plants often possessing resistance to several herbicides/herbicide groups. Historically, herbicide target-site changes accounted for most of the known resistance mechanisms in this weed; however, over the last few years, nontarget-site mechanisms, particularly enhanced herbicide detoxification, have become extremely common in A. tuberculatus. Unravelling the genetics and molecular details of nontarget-site resistance mechanisms, understanding the extent to which they confer cross resistance to other herbicides, and understanding how they evolve remain as critical research endeavors. Transcriptomic and genomics approaches are already facilitating such studies, the results of which hopefully will inform better resistance-mitigation strategies. The largely unprecedented level of herbicide resistance in A. tuberculatus is not only a fascinating example of evolution in action, but it is a serious and growing threat to the sustainability of midwestern US cropping systems. This article is protected by copyright. All rights reserved.

Keywords: Cross resistance; evolution; genomics; herbicide metabolism; herbicide resistance; nontarget-site resistance; target-site resistance; waterhemp.