Expert response from GMOAnswers Admin_1
Tuesday, 11/19/2013 15:23
Good question, and let me explain to you why a genetically modified plant that does not die when sprayed with glyphosate (the active ingredient in Roundup) is as safe as a non-modified plant. There are actually several reasons.
First, conventional plants naturally contain a protein/enzyme, EPSPS, that produces the aromatic amino acids that are essential for plant growth. Glyphosate works to block this enzyme. That is how glyphosate-based herbicides can kill most non-modified plants. Plants modified to withstand glyphosate contain a gene that produces a similar EPSPS from bacteria called Agrobacterium strain CP4, and this EPSPS is tolerant to glyphosate. In other words, plants to which this variant of EPSPS is introduced can continue to produce the normal essential amino acids and survive. It was the discovery of the variant of the EPSPS from the bacteria that allowed scientists to introduce this variant of EPSPS into the conventional plants to make them tolerant to glyphosate.
Next, after establishing that the plants modified with the CP4 EPSPS enzyme were able to withstand the spray of glyphosate, these plants were grown and treated with glyphosate in multiple regions all across the United States. All edible plant parts produced from these plants were extensively analyzed to show that the composition of the modified plants was compositionally equivalent to conventional plants grown at the same locations.
Lastly, there are limits on how much herbicide can be used and the intervals at which the herbicide can be sprayed on the plants. These limits are established by the U.S. EPA and other agencies across the world and are based on scientific data that determine the breakdown of the herbicide on the plant material itself, as well as degradation rates in the soil. Also, early in the development of these technologies, developers of such plants are required to actually measure the residue of glyphosate—in this case, on the plant at various stages of plant development and at the end of the season. It is on the basis of these data that levels of glyphosate that can be sprayed early in the season were established. (Note: this has been described in more detail here.)
Thus, use of innovative technologies allows scientists to safely introduce a gene that in turn becomes part of the plant’s genome and produces food as safe as conventional crops. This technology allows for an effective weed-control system that improves yields. In addition, please note that weeds are the most persistent pests that cause extensive yield losses in agriculture. In addition, it is also important to point out that farmers have been using various herbicides in U.S. agriculture to control weeds for over 50 years and the use of herbicide-tolerant crops for the last 18 years has allowed farmers to improve yields and prevent extensive soil loss through use of low-till farming.
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