Herbicide resistance: NewLeaf^TM Roundup Ready (under development)

Roundup (glyphosate) is a broad-spectrum herbicide used for the postemergence control of annual and perennial weeds in major crop systems. It is rapidly degraded by naturally occurring soil microbes and is not a threat to groundwater or surface water. Nor will it accumulate in the food chain. It promotes environmentally favourable tillage methods, which allow farmers to protect soil from erosion and degradation.

Several glyphosate-resistant crop species have been produced including cotton, maize and wheat. Glyphosate operates by inhibiting the action of the plant enzyme 5-enoyl-pyruvalshikimate-3-phosphate synthase (EPSPS) involved in the shikimic acid pathway which is responsible for the production of aromatic amino acids. Tolerance to glyphosate in GM crops is generated by expressing an EPSPS gene isolated from a strain Agro of bacteriun tumefaciens. The gene encodes an EPSPS enzyme with reduced sensitivity to glyphosate compared with the plant enzyme. The enzyme therefore functions in essential aromatic amino acid biosynthesis in the presence of glyphosate. Glyphosateresistant potato has not reached the marketplace but, as with other glyphosateresistant crops, could be expected to deliver more effective and precise weed control.