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Canola fields in New South Wales

A major concern about genetically modified (GM) crops is that they might spread their genes to nearby plants. But so far regulators have had few data on pollen-mediated gene flow with which to assess the environmental impact of GM crops.

Now a comprehensive study published in this week's issue of Science provides some hard numbers on the movement of pollen between fields.

A team led by Mary A. Rieger of the Cooperative Research Center for Australian Weed Management and the University of Adelaide and colleagues report that canola pollen can travel considerable distances but that the amount of gene flow is minimal.

The researchers collected seeds from conventional canola fields growing near fields planted with herbicide-resistant varieties.

They found that the herbicide-resistance trait spread to 63 per cent of the conventional fields, including some up to three kilometres away from the source. The percentage of resistance among seed samples ranged up to nearly 0.2 per cent, but when averaged per field, the highest percentage was 0.07 per cent.

Although the findings reinforce the difficulty of growing GM-free crops, they also suggest that levels of gene diffusion are low.

Reference: Science, 28 June 2002

Photo credit: © Steve Sutherland/New South Wales Agriculture

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