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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
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