Brussels, 22 March 2002
Further research is needed on GM (genetically modified) gene transfer in the light of recommendations from the EU on thresholds for the contamination of non-GM crops, according to a new report from the European Environment Agency (EEA).
The report examined gene flow through pollen transfer from six crops that have been genetically modified and are close to commercial release in the European Union: oilseed rape, sugar beet, potatoes, maize, wheat and barley. Each crop revealed varying degrees of gene flow as a result of differing mechanisms for pollen production and dispersal.
The report calls for further research into biological and physical barriers to gene transfer through cross-pollination, in the light of a recommendation from the European Commission of a one per cent threshold for GM contamination for crops to be accorded 'GM free' status. The report also recommends further studies on gene flow through the contamination of crops with 'spilled' seed from GM crops grown on the same site in previous years, and on actual levels of gene transfer into wild populations.
Oilseed rape emerged as a high-risk crop for gene flow from crop to crop and from crop to wild relatives. During farming, the report warns, 'low levels of gene flow will occur at long distances and thus complete genetic isolation will be difficult to maintain.' It predicts that multiple herbicide resistance in oilseed rape 'will become common post-GM release' through the process of 'gene stacking,' where genes from separate GM varieties accumulate in plants that grow from seed spilled at harvest (volunteer plants).This can lead to the creation of plants with accumulated genetic traits from different GM varieties.
Sugar beet is described as a medium to high risk crop for gene flow from crop to crop and crop to wild relatives. Pollen from sugar beet has been recorded at distances of over 1 km. While cross-pollination is not considered a problem in root crops, which are harvested before flowering, stray plants from crops may lead to transgene movement. Maize is described as a medium to high risk crop for gene flow from crop to crop only. The report states that while 'evidence suggests that GM maize plants would cross-pollinate non-GM maize plants up to and beyond their recommended isolation distance of 200 m,' there are no known wild relatives in Europe with which GM maize can hybridise.
The report finds that wheat, barley and potatoes all pose a low risk for gene flow from crop to crop and from crop to wild relatives, due to low levels of wheat cross-pollination under field conditions, the fact that barley reproduces through self-fertilisation and the resistance of harvested potatoes to pollen contamination.
The report stresses, however, that 'none of these crops has pollen which can be entirely contained.' It explains that while isolation zones and crop or other vegetation barriers can reduce pollen dispersal, 'changing weather and environmental conditions mean that some long distance pollen dispersal will occur.' Furthermore, the report's authors warn that 'the possible implications of hybridisation and introgression between crops and wild plant species are so far unclear because it is difficult to predict how the genetically engineered genes will be expressed in related wild species.'
For further information and to view the report, please consult the following web address: http://www.eea.eu.int
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