Herbicide Tolerant – Glyphosate

Weeds are a genuinely serious agricultural problem, and not just because they compete directly with the crop for sunlight, water, nutrients and physical space - they also act as a reservoir and carrier for insect pests and plant diseases, so an uncontrolled weed problem can drag crop yield down significantly on both fronts at once. Glyphosate, sold commercially by Monsanto (USA) under the trade name 'Roundup', kills plants by blocking a specific enzyme, EPSPS (5-enolpyruvylshikimate-3-phosphate synthase), which plants need to biosynthesise aromatic amino acids, vitamins and various other secondary metabolites - block that one enzyme, and the plant simply cannot make several classes of molecule essential to its own survival. The genetic-engineering trick, then, is to make the crop itself immune to this mechanism while still killing every surrounding weed. There are two distinct strategies for doing this: incorporating a soil-bacterium gene that produces a version of EPSPS which glyphosate cannot effectively block, or incorporating a different soil-bacterium gene that instead produces an enzyme able to actively degrade glyphosate itself before it can do any damage. Either way, the resulting glyphosate-tolerant crop delivers several concrete benefits: higher yield through more effective weed control, less herbicide needing to be sprayed overall, reduced direct competition between the crop and surrounding …