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Daily News Archive
From February 7, 2002


Genetically Modified Super-Weeds "Not Uncommon"


According to English Nature, the UK government's advisory body on conservation, an extensive study of genetically modified (GM) herbicide tolerant oilseed rape crops in Canada has revealed that genes from separate GM varieties can accumulate ('gene stacking') in plants that grow from seed spilled at harvest (volunteer plants). This happens because different varieties cross-pollinate, and their offspring may contain the accumulated genes from GM varieties with different genetic traits. In Canada these plants are now resistant to several widely used herbicides, with farmers regularly resorting to old herbicides to control them. In effect, they are on the road to becoming nuisance weeds.

The Canadian system of voluntary guidelines advising farmers to leave a separation distance of 175 m between different GM varieties seems to have broken down, and 'gene stacking' is now widespread in Canada. A code of practice for farmers growing GM crops in the UK has already been developed by the industry body SCIMAC.

Dr Brian Johnson, English Nature's biotechnology advisor said, "Our report shows that the SCIMAC code is probably inadequate to prevent gene stacking happening in Britain, if these crops were commercialized. The consequences for farmers could be that volunteer crops would be harder to control and they might have to use different, and more environmentally damaging, herbicides to control them."

English Nature are concerned that attempts to eliminate GM volunteers with multiple herbicide tolerance in 'weedy' crops like oilseed rape could lead to more intensive herbicide use in field margins and uncropped habitats, which can be important refuges for wildlife.

Dr. Johnson said, "We do not yet know how 'stacked gene' plants would behave either in farmers' fields or in the wild. The European regulatory system has not yet approved GM herbicide tolerant oilseeds for general release. English Nature will be working with DEFRA and ACRE to ensure that risks from possible gene stacking are properly addressed, and that we avoid the mistakes that have been made in Canada."

The European Commission has recently proposed that a threshold of up to 0.7% GM seed should be allowed in batches of conventional crop seed. English Nature are deeply concerned that if this proposal were to be adopted, it might be a recipe for gene stacking, because the GM plants from a seed batch could be made up of several varieties that would inevitably hybridise, giving 'volunteer' plants next season with multiple GM traits. It will be difficult to police seed batches to ensure that this does not happen.

English Nature has been pressing the GM industry to explain how to deal with these issues before GM crops are released widely, rather than wait for stacking to emerge and then try to control the rogue crop plants.