Crop pollen spreads further than expected

New Scientist
19:00 27 June 02

Fred Pearce

 

Pollen from genetically modified crops can travel at least three kilometres to contaminate neighbouring crops, according to a new study in commercial fields. The findings pose a serious problem for organic farmers, and will strengthen calls for tougher controls on planting GM crops.

The study followed the spread of genes from a new herbicide-resistant variety of oilseed rape, or canola, introduced into Australia two years ago. It found that the genes travelled much further than expected.

The rape variety was not itself genetically modified. But, says the team led by Mary Rieger at the University of Adelaide, the gene flow through cross-pollination mimics that from a GM crop.

Rieger says this is the first investigation of potential GM contamination from large commercial fields. It suggests, she says, that "real world" genetic contamination from GM crops could be more widespread and less predictable than suggested by small-scale trials. "Laboratory and small-scale experiments may not necessarily predict pollination under commercial conditions," she warns.

Patrick Mulvany of the Intermediate Technology Development Group says: "The reality is that we cannot stop genes from GM crops spreading across the landscape. To suggest otherwise flies in the face of the evidence," says.


No gradient

The researchers collected seeds from 63 conventional canola fields near fields planted with the new variety in three states. In all, almost 50 million seeds were tested.

They found that the contamination -- through insects and the wind spreading pollen -- was not large. No more than 0.2 per cent of seeds taken from one traditional field contained genes from the new fields. But it did spread a long way. The furthest gene uncovered was three kilometres from its source.

Equally surprising, says Rieger, there was no obvious gradient of contamination according to distance from the source. The genes turned up almost randomly in the study area, she says.

This was different from the pattern found in previous small-scale trials, where contamination dropped off exponentially with distance. Rieger guesses that this could result from insects ranging far and wide in search of pollen, particularly early or late in the season when flowers are scarce.


Import moratorium

Other crops may not spread their genes so widely. The flowers of wheat and barley, for instance, can self-fertilise. This could make them less likely to pick up foreign genes.

But campaigners against GM crops will seize on the findings about the ability of oilseed rape to spread its genes. They fear the pollution of both traditional crop varieties and their wild ancestors and want a moratorium on imports of GM crops to the major centres of their natural biological diversity.

The new findings follow warnings from scientists from the UK government's wildlife agency, English Nature, last year that cross-pollination could result in genes from genetically modified oilseed rape accumulating in plants, creating "superweeds" resistant to a range of herbicides.

 
19:00 27 June 02
 

 

 

  Copyright Reed Business Information Ltd.