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The wild plants could have an herbicide resistance advantage.

Credit Xiao Yang
One of the most common methods employed to make crops resistant to herbicides was shown to have advantages over the weedy varieties of rice. This finding suggests that the modifications could affect the environment beyond farms.

Many crops are genetically engineered to resist glyphosate. The herbicide, initially known as Roundup, was introduced to the market in 1996 under the tradename Roundup. This allows farmers to eliminate most herbicides from their fields, without causing harm to their crops.

ラウンドアップ Glyphosate acts as an inhibitor of the growth of plants. It blocks an enzyme known EPSP synthase. This enzyme plays a role in the creation of specific amino acids as well as other molecule. These compounds can account for up to 35% of the plant’s mass. Genetic modification, like the Roundup Ready crops manufactured by Monsanto in St. Louis, Missouri, involves inserting genes into the genetic code to boost EPSP production. The genes are usually derived from bacteria that cause disease in the plants. The additional EPSP synase makes it possible for plants to counter the effects of glyphosate. Biotechnology labs have also attempted to utilize plants’ genes instead of bacteria to boost EPSP-synthase production, in part to exploit the loophole that is in US law that allows the approval of regulatory agencies for organisms that carry transgenes not that are derived from bacteria.

There aren’t many studies that have examined whether transgenes such as ones that confer resistance to glyphosate could — after they are wild or weedy relatives by cross-pollination, make plants more competitive in terms of survival and reproduction. Norman Ellstrand of University of California Riverside states, “The conventional expectation is that any transgene in the wild will cause disadvantages if there is no pressure to select because the extra machinery could lower the health.”

However, a new study conducted by Lu Baorong, an ecologist at Fudan University in Shanghai, disproves that belief: it shows that the weedy version of the popular rice plant, Oryza sativa has an impressive fitness boost due to resistance to glyphosate, even when glyphosate has not been applied.

Lu and colleagues modified cultivated rice species to enhance its EPSP synthase. The modified rice was then crossed with a wild relative.

The team let the offspring of crossbreeding to cross-breed with one other to create second-generation hybrids. They were genetically identical with the exception of the amount of EPSP synthase genes they had. The ones with more copies expressed higher amounts of the enzyme and also produced more amino acids tryptophan than their unmodified counterparts.

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

Lu says that making the weedy grain more competitive may increase the difficulties it causes to farmers all over the world who have crops infected by the pest.

“If the EPSP-synthase gene gets into the wild rice plant, their genetic diversity, which is essential to protect, could be threatened because the transgene’s genotype could outcompete normal species,” says Brian Ford-Lloyd an expert in plant genetics at the University of Birmingham, UK. “This is an example of the very real negative impacts of GM plantson our environment.”

This study also challenges the perception that genetically modified crops containing extra copies of their genes are safer than those containing microorganism genes. “Our study shows that this is not necessarily the case” says Lu.

The findings call for a review of future regulation of genetically modified crops, some researchers claim. Ellstrand thinks that biosafety laws could be relaxed as we can benefit from a high degree of comfort from two decades worth of genetic engineering. “But the research still indicates that innovative products require careful evaluation.”