Genetic Modification of Plants
New traits introduced to crop plants by genetic engineering have the potential to increase crop yields, improve agricultural practices, or add nutritional quality to products. For example, transgenic crop plants capable of degrading weed killers allow farmers to spray weeds without affecting yield. Use of herbicide-tolerant crops may also allow farmers to move away from pre-emergent herbicides and reduce tillage, thereby decreasing soil erosion and water loss. Transgenic plants that express insecticidal toxins resist attacks from insects. Crops engineered to resist insects are an alternative to sprays, which may not reach all parts of the plant. They are also cost effective, reducing the use of synthetic insecticides. Genetic engineering has also been used to increase the nutritional value of food; "golden rice" is engineered to produce beta-carotene, for example. Edible vaccines, present in the plants we eat, may be on the horizon.
The new traits expressed in such transgenic plants are derived from a variety of other organisms. Scientists have given a gene from the bacterium Salmonella to cultivars of soybeans, corn, canola, and cotton to degrade the pesticide glyphosphate (Roundup TM). The gene for the insecticidal toxin in transgenic cotton, potato, and corn plants comes from the bacterium Bacillus thuringiensis (Bt). One of the genes allowing vitamin A production in golden rice is derived from the bacterium Erwinia uredovora; others are from the daffodil.