Notes

Genetically modified crops offer benefits over weeds

Wild plants could be treated with herbicides.

Credit: Xiao Yang
A genetic-modification technique used widely to produce crops that are herbicide-resistant has been found to provide advantages to the weedy rice, even in absence of herbicide. This finding suggests that these changes could have an impact on the environment beyond farm.

Many cultivars are genetically altered so that they can resist glyphosate. This herbicide was first available under the trade name Roundup. This resistance to glyphosate allows farmers to eradicate the majority of herbicides in their fields without damaging their crop.

ラウンドアップ Glyphosate slows the growth of plants by stopping EPSP synthase (an enzyme that plays a role in the production of specific amino acids, and various other molecules). https://www.nou.co.jp/shop/g/g0203013408003/ The enzyme can be as large as 35 percent or more of a plant’s total mass. Genetic modification, like the Roundup Ready crops manufactured by Monsanto in St. Louis, Missouri, involves inserting genes to a crop's genetic code to increase EPSP production. Genes are typically obtained from bacteria that cause disease to the crops.

The plant can resist the adverse effects of glyphosate since it has an additional EPSP-synthase. Biotechnology laboratories are trying to use genes from plants rather than bacteria to boost EPSP synthase. This is partly because the US law permits regulatory approval that allows organisms that carry transgenes to get approved.

ラウンドアップ A few studies have looked into whether transgenes such as those that confer resistance to glyphosate can -- once they are wild or weedy relatives by cross-pollination -- make those plants more competitive in terms of survival and reproduction. Norman Ellstrand is a University of California Riverside plant geneticist. "The expectation is that any transgene will cause disadvantage in the wild, in absence of pressure to select, due to the fact that it reduces fitness," Ellstrand said.

Lu Baorong, an ecologist from Fudan University in Shanghai has changed the way that he views this. He has discovered that glyphosate resistance gives a significant fitness lift to the weedy variant of the standard rice plant Oryza Sativa.

In the study which was published this month in New Phytologist 1, Lu and his coworkers genetically altered the rice cultivar to overexpress the species' own EPSP synthase. They also crossed-bred the modified rice with a weedy cousin.

The researchers then allowed cross-breeding offspring to be bred with one another to create second-generation hybrids. These were genetically identical, with the exception of the number and copy count of the EPSP synthase gene. As expected, those with more copies expressed higher levels of the enzyme, and produced more amino acids tryptophan than their unmodified counterparts.

ラウンドアップ Researchers also discovered that transgenic hybrids produced between 48-125percent more seeds per plant, and had more photosynthesis, and had more shoots than the non-transgenic varieties.

Lu believes that making weedy aggressive rice more competitive could hinder farmers to repair the damage caused by this bug.

Brian Ford-Lloyd, a UK plant geneticist. He says, "If the EPSP synthase gene gets in the wild rice species, their genetic diversity would be threatened which is really significant because the genotype with transgene has a higher level of competition than the standard species." "This is among the clearest instances of the extremely damaging impacts [of GM crops on the environment."

The study also challenges the public belief that crops modified genetically carrying additional copies of their genes are more secure than those containing genes from microorganisms. Lu says that "our study doesn't prove that this is true."

According to some researchers this research suggests that future regulation of genetically engineered crops should be rethought. https://www.pref.nagano.lg.jp/nogi/sangyo/nogyo/gijutsu/fukyugijutsu/200901/documents/091h06.pdf Ellstrand saysthat "Some people believe that the biosafety regulations should be relaxed." Ellstrand addsthat "But this study has shown that novel products still need to be evaluated with care."


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