Long and short of it

Pollens of GM crops spread further than expected

Published: Wednesday 31 July 2002

Pollen from genetically modified (gm) crops can travel at least three kilometres to contaminate neighbouring crops, according to a study. The study, by researchers from Australia-based University of Adelaide, followed the spread of genes from a new herbicide-resistant variety of GM oilseed rape introduced in Australia two years ago. It found that the genes travelled much further than expected. The rape variety was not itself modified, but its gene flow was similar to that of a GM crop. Mary Rieger, the lead author of the study, says that this is the first investigation of potential GM contamination from large commercial fields.

The researchers collected seeds from 63 conventional canola fields located near fields planted with the new GMvariety. 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, the researchers found no obvious gradient of contamination according to distance from the source. The genes were found randomly in the study area. This was different from the pattern found in small-scale trials, where contamination levels decreased exponentially with distance. The researchers speculate that the difference could be due to insects travelling far in search of pollen, particularly during the season when flowers are scarce.

Rieger says that the study suggests that real genetic contamination from GM crops could be more widespread and less predictable than suggested by small-scale trials.

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