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In the wild, herbicide resistance might confer an advantage to plants.

Credit Xiao Yang
A well-known method of the genetic modification of plants to make them resistant to herbicides is found to confer advantages to weedy varieties of rice even when herbicide is not present. These findings suggest that these modifications can have a broad variety of impacts that extend beyond farms, and possibly into the wild.

A range of crops has been modified genetically so that they are resistant to Roundup herbicide glyphosate. This resistance to glyphosate permits farmers to eradicate most plants without doing any harm to their crop.

ラウンドアップ Glyphosate slows the growth of plants by blocking an enzyme referred to as EPSP synthase. ラウンドアップ This enzyme is responsible for the production of certain amino acids and other molecules that comprise about 35% of a plant’s mass. Genetic modification that is employed by Monsanto’s Roundup Ready crops, which are based in St Louis (Missouri), typically involves inserting genes in a crop’s DNA to increase EPSP synthase production. The genes typically come from bacteria that cause disease in plants.

The plant can endure the negative effects of glyphosate due to its extra EPSP-synthase. Biotechnology labs have also tried to make EPSP-synthase more plant-based than bacteria, using genes derived that come from plants. This was done to exploit an inconsistency found in US law, which permits the approval of regulatory authorities for organisms which aren’t the result of bacteria or parasites.

There aren’t many studies that have looked into whether transgenes which confer glyphosate resistance can increase the competitiveness of plants for reproduction and even survival after they are introduced to wild or weedy relatives by cross-pollination. “The conventional belief is that any sort of transgene can cause disadvantages in the wild in absence of selection pressure, because the additional machinery could lower the fitness,” says Norman Ellstrand who is a plant geneticist at the University of California in Riverside.

A new study, led by Lu Baorong, an ecologist from Fudan University in Shanghai, disproves that belief It reveals that a weedy form of the common rice plant, Oryza sativa, gets an impressive fitness boost due to glyphosate resistance, even when glyphosate has not been applied.

Lu and his colleagues genetically modified the cultivated Rice species to express its EPSP synthase. Then, they crossed-bred it with the weedy parent.

The group then permitted the offspring from cross-breeding to cross-breed with each other to create second generation hybrids. They were identical genetically with the exception of the amount of EPSP synthase genes they had. It was expected that those with more copies had higher enzyme levels and produced more amino acid tryptophan when compared to the unmodified counterparts.

Researchers also discovered that transgenic hybrids are more photogenic, had more seeds per plant, and produced 48 to 125 percent higher yields of seeds than varieties that were not transgenic.

Lu believes making weedy, invasive rice more competitive may make it harder for farmers to repair the damage caused by this pest.

Brian Ford-Lloyd (a UK plant geneticist) states that if the EPSP synthase genes gets into wild rice species, their genetic diversity, which is vital to preserve could be endangered. The transgene will surpass the regular species. This is one of the clearest examples of extremely likely negative effects of GM crop on the environment.”

This study challenges popular belief that crops modified genetically that carry additional copies of their own genes are less dangerous than those containing the genes of microorganisms. Lu states that his research does not contradict this belief.

ラウンドアップ Some researchers believe this finding requires a review of the future regulation of crops that have been genetically modified. Ellstrand claims that “some people believe that biosafety regulation could be relaxed since we have a a high degree of comfort with genetic engineering over the last two decades.” “But the study shows that novel products still need careful assessment.”