Notes

Genetically modified crops offer greater benefits than herbicides

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

Credit Xiao Yang
A common method of genetic modification employed to make crops resistant to herbicides was found to have advantages over weedy forms of rice. This indicates that these changes could have an impact on the environment beyond farms.

There are many kinds of crops are genetically modified to resist glyphosate. Roundup was the first herbicide to be marketed. ラウンドアップ 撒き方 Farmers can eradicate most weeds from their fields with this glyphosate-resistant crop without causing damage to their crops.

Glyphosate can inhibit plant growth by inhibiting EPSP synase which is an enzyme that plays a role in the production of amino acids and other chemicals that comprise about 35% of the plant's mass. The genetic-modification technique -- employed, for example in Roundup Ready crops made by the biotech giant Monsanto which is headquartered in St Louis, Missouri -usually involves inserting genes into the crop's genome to increase EPSP-synthase's production. Genes typically come from bacteria that cause disease to plants.

The plant is able to resist the adverse effects of glyphosate since it has an additional EPSP-synthase. Biotechnology labs have also attempted to create EPSP synthase with more plant-based components than bacteria, using genes derived taken from plants. This was partially used to take advantage of a loophole found in US law, which permits regulatory approval for species which aren't the result of bacteria or parasites.

ラウンドアップ There aren't many studies that have examined whether transgenes such glyphosate-resistant genes could -- after introduction to wild or weedy plants by cross-pollination -- increase the competitiveness of these plants in survival, reproduction and growth. ラウンドアップ Norman Ellstrand of University of California Riverside declares, "The conventional expectation is that any transgene in the wild will be detrimental if there's no pressure to select because the additional machinery may reduce the fitness."

Lu Baorong (an ecologist at Fudan University, Shanghai) has now questioned that opinion. It has proven that glyphosate resistance can give an impressive fitness boost to a weedy rice crop called Oryza sativa even when it is not used.

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

ラウンドアップ The team allowed the offspring of cross-breeding to mix with each other, creating second-generation hybrids genetically identical to each other except for the number of copies of the gene that encodes EPSP synase. As was expected, those with more copies had more enzyme activity and an increased amount of amino acid tryptophan compared to their counterparts that were not modified.

Researchers also found that transgenic hybrids produced between 48 to 125 percent more seeds per plant, had higher photosynthesis rates and produced more shoots than those that were not transgenic.

Lu suggests that making weedy Rice more competitive could cause more problems for the farmers around the world who's fields are being ravaged by the pest.

ラウンドアップ Brian Ford-Lloyd of Brian Ford-Lloyd from the University of Birmingham, UK Brian Ford-Lloyd from the University of Birmingham, UK "If the EPSP synthase gene is introduced to wild rice species their genetic diversity, which was really important in conserving it, could be at risk because it could outcompete the normal varieties." "This is among the most obvious instances of extremely plausible negative consequences [of GM crops] upon the environment."

ラウンドアップ This study challenges public notion that genetically modified plants that carry extra copies of their genes are safer than the ones that have genes from microorganisms. "Our study proves that this isn't necessarily the case" Lu says. Lu.

The finding calls for a rethinking of future regulations for the genetically altered crops, scientists suggest. "Some individuals are saying that biosafety regulation can be relaxed because we have a high level of comfort in the last two years of genetic engineering" says Ellstrand. ラウンドアップ "But the research still indicates that innovative products require careful evaluation."


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