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The wild plants could have the advantage of resistance to herbicides.

Credit Xiao Yang
A genetic-modification technique used widely to make crops herbicide resistant has been shown to provide advantages to an invasive form of rice, even in absence of herbicide. This suggests that the genetic modifications could also have the potential to impact wild animals.

A wide range of crops has been genetically modified so that they are resistant to Roundup herbicide glyphosate. Farmers are able to eliminate weeds in their fields using glyphosate, without harming their crops because of this resistance.

Glyphosate prevents plant growth by inhibiting EPSP synthase (an enzyme that plays a role in the formation of amino acids as well as various other molecules). The enzyme can be as large as 35% or more of the plant’s total mass. The genetic-modification technique — employed, for example, in Roundup Ready crops made by the biotechnology giant Monsanto which is headquartered in St Louis, Missouri — typically includes inserting genes into the crop’s genome to increase the production of EPSP synthase. Genes are typically obtained from bacteria that cause disease to crops.

The plant is able to withstand the effects caused by glyphosate because it has an additional EPSP-synthase. Biotechnology labs also tried to use plants’ genes to increase the EPSP synthase enzyme, in part to take advantage of a loophole in the American system which permits the approval of regulatory authorities of transgenes not derived bacterial pests.

There aren’t many studies that have looked into whether transgenes like those which confer glyphosate resistance can help plants compete in reproduction and survival once they’re introduced to wild or weedy relatives through cross-pollination. “The conventional belief is that any sort of transgene will confer disadvantage in the wild, in the absence of selection pressure, due to the fact that any additional machinery will decrease the fitness of the plant,” says Norman Ellstrand, a plant geneticist at the University of California in Riverside.

Lu Baorong (an ecologist at Fudan University, Shanghai) has now challenged that view. It shows that resistance to glyphosate provides significant benefits to fitness for the weedy rice crop called Oryza sativa even when not being used.

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

The researchers allowed offspring from cross-breeding to breed with each other, resulting in second-generation hybrids genetically identical to each other , with the exception of the amount of copies of the gene encodes EPSP synase. As expected, the hybrids with more copies were more likely to produce more tryptophan and have greater levels of enzymes over their counterparts that were not modified.

Researchers also found that transgenics have higher rates of flowering, more flowers and 48-125percent more seeds/plant than nontransgenics.

ラウンドアップ Lu says that making the weedy grain more competitive may cause more problems for farmers across the world who have crops infected by the insect.

Brian Ford-Lloyd (a UK plant geneticist) says that if the EPSP-synthase genes are introduced into wild rice, then their genetic diversity which is so important to conserve could be endangered. The transgene would be more competitive than natural species. “This is among the most clear examples of extremely plausible damaging effects (of GM crops on the environment.”

ラウンドアップ The study also challenges the perception that crops with genetically modified genes containing additional copies of their genes are safer than crops that have microorganism genes. Lu says that “our study is not proving this to be the case.”

The finding calls for a reconsideration of the future regulations for the genetically altered crops, scientists claim. Ellstrand states that “some people are now of the opinion that biosafety regulations could be relaxed because we have the most comfort with genetic engineering for the past two decades.” “But the study proved that new products require careful analysis.”