Utility of Aryloxyalkanoate Dioxygenase Transgenes for Development of New Herbicide Resistant Crop Technologies

Introduction Widespread adoption of herbicide resistant crops, glyphosate-resistant (GR) crops in particular, is evidence of the many benefits associated with these traits. Estimates for 2010 indicated that herbicide resistant crops accounted for 70%, 78%, and 93% of US maize, upland cotton, and soybean, respectively1. A recent report by the National Research Council outlined a number of benefits that have accrued from the widespread use of GR technology, such as lower cost of production, higher yields, greater flexibility and simplicity in farm management, as well as greater adoption of conservation tillage (NRC-NAS). However, the same report also raised issues regarding the sustainability of GR weed control systems due to a growing number of weeds that have developed resistance to glyphosate. The selection pressure created by continuous use of glyphosate in the absence of other weed control measures has caused significant infestations of weed biotypes with innate mechanisms to avoid injury from glyphosate applications (www.weedscience.org). In addition, repeated use of glyphosate has produced ecological shifts to species that are inherently less susceptible to the herbicide. Most weed scientists agree that the only way to preserve the benefits of the GR weed control system is to introduce a greater diversity of tools into the system.