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Transgenic crops can persist for ten years

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April 2, 2008

Source: Nature via Checkbiotech
http://www.nature.com/news/2008/080401/full/news.2008.729.html
By Michael Hopkin

Transgenic oilseed rape can survive and produce plants as much as a decade after it was sown, according to a study done in Sweden.

The discovery that transgenic seeds can survive and germinate on farmland for this length of time raises fresh questions about how to monitor genetically modified (GM) crops. The crops need to be controlled to ensure that genes designed to pump out pharmaceuticals, for example, don't wind up in food, and that crops labelled as 'organic' are pure enough to satisfy consumers and regulators.

Plant ecologists led by Tina D'Hertefeldt of Lund University made the discovery after studying seedlings found growing at Lönnstorp Experimental Farm. The biotech firm Plant Genetic Systems sowed a plot of various transgenic oilseed rape strains, including a herbicide-resistant variety, in the farm in 1995 as part of a trial. Since 1996, the plot has been used to grow wheat, barley and sugar beet instead.

D'Hertefeldt and her colleagues collected seedlings from the plot in 2005, and unexpectedly found 38 oilseed rape plants growing amongst the modern crops. When they tested the plants with herbicides, they found that 15 were resistant and so came from seeds left by the transgenic plants. They report their findings in the journal Biology Letters 1.

Label-friendly

Oilseed rape strains, both transgenic and non-transgenic, are known to be persistent. This study confirms that "some of the seeds will remain viable for an awfully long time", says Les Firbank, head of North Wyke Research in Devon, UK.

With no proven health dangers of herbicide-resistant crops, the issue here is one of living up to labelling standards, Firbank says.

The European Union, for instance, rules that food labelled as 'organic' should contain no more than 0.9% of its material from genetically modified sources. The persistence of transgenic seeds may now make this limit difficult to adhere to, particularly if new crops are planted in the same field where GM crops were once grown.

D'Hertefeldt says that there is no way to tell whether the level of contamination they found would exceed the European Union's limits in fields sown with GM oilseed rape and then used for food production. "We found quite a low number of plants," she says.

Some farmers favour herbicide-resistant oilseed rape because it allows them to easily wipe out weeds before sowing other crops. Some seed companies, such as the multinational giant Monsanto, have suggested that transgenic crops could be grown in between seasons of non-GM crops to help manage weeds.

Getting into the food chain

The persistence of oilseed rape may be an important consideration not just for transgenic crops, but also for non-transgenic oilseed rape strains, such as those grown for use as biofuels. The persistence of these seeds may lead to contamination of food crops, making them unfit for human consumption. "This is an important issue for all crops that have persistent seeds — it's not only about GM," Firbank says.

Other strains of oilseed rape are being engineered as potential 'pharma' crops, producing chemicals that may pose a danger if they enter the public food chain. "There are potential issues for food safety," Firbank says.

Persistence might not be such an issue with other transgenic crops, especially those that can be prevented from producing seeds, such as the high-starch potatoes being trialled in Germany, D'Hertefeldt says. But engineering oilseed rape not to produce flowers is out of the question. "With oilseed rape the crop you're after is the oil, and the oil is in the seeds," D'Hertefeldt says.

References
1. D'Hertefeldt, T ., Jørgensen, R. B. & Petterson, L. B. Biol. Lett. doi:10.1098/rsbl.2008.0123 (2008).

® 2008 Nature Publishing Group

 

 

 

 

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