Glyphosate - Resistant Crops and Weeds : Now and in the Future

The adoption of transgenic crops (also called GMOs and biotech crops) worldwide has been rapid and impressive, reaching 120 million ha in 2008, and continues to grow at a steady pace (James, 2008). Approximately 80% of the total area devoted to these crops has been planted with herbicide-resistant crops, virtually all being glyphosate-resistant (GR) crops. Thus, a single genetic trait—glyphosate [N-(phosphonomethyl) glycine] resistance—accounts for most of the success of transgenic crops at this time. Wide-spread adoption of GR crops and glyphosate has had significant economic effects in agriculture, from replacement of previous herbicide markets (Gianessi, 2008; Nelson & Bullock, 2003) to cost savings for farmers in weed management (Brookes & Barfoot, 2008; Gianessi, 2008). Furthermore, GR crop technology has generally reduced the adverse environmental and health impacts of weed management (e.g., Cerdeira & Duke, 2006, 2007; Gardner & Nelson, 2008). GR crops have been a boon to farmers who have adopted them, but overuse of this single weed management technology is jeopardizing this safe, highly effective, and economical tool due to the emergence of new weed species that are only poorly controlled by glyphosate (Owen, 2008) and the evolution of GR weeds. Many factors are at play in this global scenario, including further adoption of GR crops, new GR crops being introduced, other types of herbicide-resistant crops now available or that will soon be introduced, introduction of new herbicides for use in conventional crops, and the spread of current and future GR weeds. This short review will build on earlier papers (Duke, 2005; Duke & Powles, 2008) in which we reviewed the status of GR crops, other herbicide-resistant crops, and GR weeds. Green’s (2009) review focused on the technical aspects of GR crops and transgenes that will be stacked with GR transgenes.