Notes

Genetically modified crops offer benefits over weeds

Wild plants could be given herbicide resistance.

Credit Xiao Yang
A method of genetic modification used extensively to create crops that are resistant to herbicides has been shown to provide advantages to an invasive form of rice even in absence of the herbicide. The results suggest that the benefits of such modifications could extend beyond farms and out into the wild.

A variety of varieties of crops have been created genetically to be resistant to the glyphosate. This herbicide, originally known as Roundup, was introduced to the market in 1996 under the tradename Roundup. This resistance to glyphosate permits farmers to eradicate most weeds without causing any damage to their crop.

ラウンドアップ inhibits growth of plants by stopping EPSP synthase (an enzyme involved in the production of specific amino acids and various other molecules). The enzyme can comprise as much as 35 percent or more of the plant's total mass. The technique of genetic modification is employed, for example, in Roundup Ready plants made by Monsanto Biotechnology Inc., a biotech firm located in St Louis, Missouri. It involves inserting genes into the genome of the crop to increase EPSP synthase synthase synthase production. Genes are typically obtained from bacteria that infects the crops.

The plant is able to resist the effects glyphosate thanks to the addition of EPSP synthase. Biotechnology labs have also attempted to make use of the genes of plants to increase the EPSP synthase enzyme, in part to take advantage of a loophole in the American system that permits regulatory approval of transgenes which are not derived from bacterial pests.

There aren't many studies that have examined the possibility that transgenes that confer tolerance can -- once they become weedy or wild relatives by cross-pollinatingcan boost the plant's survival and reproduction. "The common belief is that any sort of transgene will confer disadvantage in the wild, in the absence of any selection pressure because the extra machinery would lower the fitness," says Norman Ellstrand, a plant geneticist at the University of California in Riverside.

Lu Baorong is an Ecologist at Fudan University Shanghai. His study shows that glyphosate resistance provides a significant fitness benefit, even if it's not used.

In their study, published this month in New Phytologist 1, Lu and his colleagues genetically modified the cultivated rice species to enhance its own EPSP synthase. They crossed the altered rice with a weedy ancestor.

The group then let the offspring of crossbreeding to cross-breed with one other to create second generation hybrids. They were identical genetically except for the amount of EPSP synthase genes they had. Like one might expect, the higher number of copies produced higher levels of enzyme, and also more tryptophan, than the unmodified counterparts.

ラウンドアップ found that transgenic hybrids have higher rates of photosynthesis. They also grew more shoots and flowers and produced 48-125percent more seeds per plant than non-transgenic hybrids -with or without the chemical glyphosate.

Lu suggests that making weedy Rice more competitive could increase the risk for farmers across the world who's fields are being ravaged by the pest.

Brian Ford Lloyd, a UK plant scientist, has said that the EPSP Synthase gene could get into wild rice species. This would threaten their genetic diversity, which is very vital. "This is one clear example of the extremely plausible detrimental consequences [of GM plants] on our surroundings."

This study challenges perception that genetically modified crops that carry extra copies of their own genes are safer than the ones that have the genes of microorganisms. Lu declares that "our study does not prove that this is true."

ラウンドアップ say this discovery calls for a rethinking the future regulation on the use of genetically modified plants. " ラウンドアップ are now claiming that biosafety regulation can be relaxed since we've achieved an incredibly high level of confidence with the two decades of genetic engineering," Ellstrand says. "But the study proved that new products require careful evaluation."


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