Herbicide-Resistant Transgenic Crops
Herbicide resistance is one of the fi rst traits engineered into plants. Generally, there are two approaches in transgenic engineering for herbicide resistance. One is the modifi cation of a plant enzyme or other sensitive biochemical target of herbicide action to render it insensitive to the herbicide, or to induce the overproduction of the unmodifi ed target protein permitting normal metabolism to occur. The other approach is the introduction of an enzyme or enzyme system that degrades or detoxifi es the compound in the plant before the herbicide reaches the site of action. Plants modifi ed by both approaches may be obtained either by selection for resistance against a specifi c herbicide or by applying gene transfer techniques utilizing genes encoding herbicide resistance determinants.