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 LundUniversity
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).
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