Notes

The advantages of genetically modified crops over the weeds

Herbicide resistance might provide advantages to plants in the wild.

Credit Xiao Yang
A common technique for the genetic modification of plants that make them herbicide-resistant has been found to give advantages to the weedy varieties of rice even when the herbicide is not present. The finding suggests that the benefits of such modification have the potential to extend beyond the confines of farms out into the wild.

ラウンドアップ Many varieties of crops are genetically engineered to resist the glyphosate. The herbicide, originally known as Roundup and then introduced to the market in 1996 under the trade name Roundup. The resistance to glyphosate permits farmers to get rid of plants without doing any harm to their crops.

ラウンドアップ Glyphosate slows the growth of plants by blocking EPSP synthase (an enzyme that is involved in the formation of amino acids, and various other molecules). This enzyme could be as large as 35% or more of a plant's total mass. Genetic modification, such as the Roundup Ready crops manufactured by Monsanto in St. Louis, Missouri, involves inserting genes into a plant's genetic code in order to increase EPSP production. The genes are often derived from bacteria that has caused the infection of plants.

The plant is able to resist the effects glyphosate thanks to the additional EPSP synthase. Biotechnology labs have also tried to use genes from plants rather than bacteria to boost EPSP-synthase production, in part to exploit a loophole within US law that facilitates the approval of regulatory agencies for organisms that carry transgenes that are not derived from bacterial pests.

Few studies have looked into the possibility that transgenes, like those that confer resistance to glyphosate, can help plants to be more resilient in survival and reproduction once they cross-pollinate with wild or weedy species. Norman Ellstrand of University of California Riverside states, "The conventional expectation is that any transgene found in the wild could cause disadvantages if there is no selection pressure because the additional machinery may lower the fitness."

Lu Baorong is an ecologist in Fudan University Shanghai. His study shows that resistance to glyphosate is a major fitness benefit even when it's not applied.

ラウンドアップ Lu and his colleagues genetically modified the rice species to express the EPSP synthase. Then, they crossed-bred it to the marijuana-producing parent.

ラウンドアップ The group then permitted breeding offspring that were cross-bred with each other to produce second-generation hybrids. They were genetically identical with the exception of the copy count and number of the EPSP synthase gene. The team found that those with greater copies of the gene that encodes EPSP synthase had more enzyme expression and produced more tryptophan in line with what was expected.

ラウンドアップ Researchers also discovered that transgenic plants had higher rates for photosynthesis, produced more flowers, and produced 48 to 125 percent fewer seeds per plant than the nontransgenic hybrids. This was in spite of the fact that glyphosate was not present.

ラウンドアップ 業務用 Making weedy rice more competitive may increase the issues it creates for farmers all over the world whose plots are invaded by pests, Lu says.

Brian Ford-Lloyd (a UK plant geneticist) claims that if the EPSP-synthase genes gets into wild rice, then their genetic diversity that is essential to protect could be threatened. The transgene could surpass the regular species. "This is an illustration of the most plausible and damaging negative effects of GM crops on the environment."

The public has a perception that genetically engineered crops with additional copies of microorganisms' genes are less risky than those that only contain their own genes. Lu states, "Our study shows this is not the case."

ラウンドアップ Certain researchers believe that this finding needs to be reviewed in light of future regulation of crops that have been genetically modified. "Some individuals are saying that biosafety regulation can be relaxed since we've achieved a high level of comfort with two years of genetic engineering" says Ellstrand. The study does not prove that new products are safe.

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