For years, debates have raged over the use of genetically modified crops in commercial agriculture. Many believe that GM crops will spread their altered genes to weeds and other unintended targets. The fear persists that many undesirable plants could become resistant to certain herbicides because they have altered genes. To that end, new findings, published today in the journal Science, may alleviate some concerns while fueling others. Recent studies headed by Mary A. Rieger of the Cooperative Research Center for Australian Weed Management Systems and the University of Adelaide in Australia tested how far pollen of herbicide-resistant canola traveled from the area in which it was planted. The researchers found that while pollen from resistant plants spread widely, the extent to which it populated adjacent fields remained low. (The tests were conducted on plants that were bred to exhibit herbicide resistance, but the results are applicable to GM canola as well.)

Australia was an ideal place to perform these experiments because until 2000, no herbicide-resistant canola had been planted there. Rieger and a team of researchers collected seeds from three states with varying climates, sampling 63 nearby fields containing conventional canola plants. They found that the herbicide-resistance trait had spread to 63 percent of the conventional fields--some up to three kilometers from the source. Within the contaminated fields, however, the percentage of resistance averaged no more than 0.07 percent. The levels are below the standards set in Europe to judge the contamination of non-genetically-modified foods. Still, the studies also reveal that, although the levels of gene flow were low, the spreading of the altered genes to non-GM plants is impossible to prevent, which could pose problems for organic crops. This marks the first time experiments of this type have been done on such a large scale.