Keep your distance
New Scientist; November 24, 2001
STRAY pollen and seed from genetically modified oilseed rape, or canola, is now so widespread in Canada that it is difficult to grow conventional or organic strains without them being contaminated. That is the stark message from Hugh Beckie of the agriculture ministry's Saskatoon Research Center, which has been monitoring GM crops since commercial farming began six years ago. Canada's experience provides valuable lessons for other parts of the world, such as Europe, that don't yet allow commercial production. It suggests that GM and non-GM varieties of some crops might have to be kept far apart or even grown in separate, designated zones. "If we move towards quite a lot of GM growing, there would have to be some sort of zoning," says Jeremy Sweet of the National Institute of Agricultural Botany in Cambridge.This is already done to prevent contamination of elite conventional strains of sugar beet and potatoes, he says.
Beckie, who spoke at the Weeds 2001 conference in Britain last week, stresses that much depends on the particular crop. Plants such as wheat and soybeans are relatively safe from contamination because they usually pollinate themselves. But oilseed rape accepts pollen from neighbours. Experiments show that pollen from GM oilseed rape travels much further than expected, Beckie says. "Our studies have shown that pollen can travel at least 800 metres." That's eight times further than the official Canadian "safe" separation of 100 metres for rape grown to supply pedigree seed. And it's four times further than the country's 175-metre separation for rape grown to supply oil or food.
Only 0.07 per cent of plants at 800 metres were pollinated, but there was a long "plateau" between 50 and 400 metres where contamination was about 0.2 per cent, dangerously close to the accepted 0.25 per cent contamination limit for elite seed. Beckie says that there's "a good chance" he will recommend extending separation distances. What's more, some GM plants are surviving in fields from year to year because they have acquired resistance to more than one weedkiller by crossing with other GM strains. Such "stacked" resistance is easily managed with other herbicides, but only if farmers know the problem exists.
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