Gene amplification delivers glyphosate-resistant weed evolution

Abstract

In a world of more than 6 billion people, humans heavily rely on the dependable cultivation of the global food grain crops: rice, wheat, soybeans, maize (and cotton for fiber). History shows that threats to food production have major repercussions, including famine, war, and civil unrest. A major threat to food production occurs every single growing season, when wild plant species (weeds) infest crop fields. Humans have battled since the dawn of agriculture to control weeds and to minimize their negative influence on food production. Modern herbicides have largely replaced human labor as the primary tool for weed control, and this has contributed significantly to the productivity of world cropping. However, despite the success of herbicides, weeds remain a primary challenge to food production, in part because selection pressure from herbicides has resulted in the evolution of herbicide resistance in weeds. A current and important example is evolved resistance to the world’s most important herbicide, glyphosate (1). Glyphosate resistance evolution is a major adverse development because glyphosate is a one in a 100-year discovery that is as important for reliable global food production as penicillin is for battling disease. The report by Gaines et al. (2) in this issue of PNAS shows how one economically important weed species has evolved glyphosate resistance via gene amplification.