[MONTEVIDEO] Contamination of traditional maize crops planted near genetically modified (GM) maize fields may be common in Uruguay, where the cultivation of GM maize has been permitted since 2003, scientists have said.
A study published in Environmental Biosafety Research (25 March) has found GM seedlings in three traditional maize fields. It is said to be the first report of cross-fertilisation between GM and non-GM maize in South America.
Studies on the unplanned presence of GM maize and the contamination of non-GM crops in Latin America have led to some controversial cases, such as a retracted 2001 Nature study from Mexico and a 2007 Peruvian study that led to a libel case against one of the scientists who challenged the findings and a subsequent campaign for freedom of speech for scientists.
And Monsanto's GM maize trial in Mexico has recently re-ignited the debate in the country that boasts the most diverse maize genetic resources.
But, unlike Mexico and Peru, Uruguay permits the cultivation of GM maize. The varieties MON810 and Bt11 were approved for commercial planting in 2003 and 2004, respectively.
Governmental regulations specify that GM and non-GM crop fields should be more than 250 metres apart to avoid cross-fertilisation and ensure their "regulated coexistence", and that 10 per cent of the field should be non-GM to provide a refuge area for biodiversity.
In the latest research, scientists from Uruguay's University of the Republic analysed five pairs of commercial maize ﬁelds where farmers planted GM maize at about the same time as a nearby non-GM crop.
Studying commercial fields is better than using experimental plots, which may not correspond to the real-life situation, the scientists argue.
In three cases they detected foreign genes from GM maize, the 'transgenes', in seedlings produced by seeds taken from the non-GM crops. The transgenes were presumably blown over in pollen from the GM fields.
The highest percentage of transgenic seedlings was 0.83 per cent in a field 100 metres from the GM maize field.
In one case, the cross-fertilisation occurred despite a Eucalyptus tree barrier (12 metres high, 30 metres wide) separating the fields, and another case involved cross-fertilisation between fields more than 250 metres apart.
Cross-fertilisation may therefore be "a common situation in Uruguay", the authors said, adding that the area planted with GM maize in the country is increasing.
"These results also show that the current regulation in Uruguay is insufficient and that the actual 'coexistence policy' is not well known among farmers," Pablo Galeano, the study's lead author, told SciDev.Net. "I think that to talk about 'regulated coexistence' without the necessary tools to make it viable is nothing more than rhetoric."
But Galeano cautioned that the findings may not necessarily apply to other crops or other countries.
"Cross-fertilisation depends on topography, size and orientation of fields, type of maize, wind direction during the flowering time, temperature and humidity, so it is hardly possible to generalise our results to other crops, areas or countries," he said.
Daniel Bayce, manager of Uruguay's National Seed Institute, told SciDev.Net that the findings were not representative because cross-fertilisation was detected mostly where the fields were too close, and even then "the frequency of GM contamination was very low".
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Environmental Biosafety Research doi: 10.1051/ebr/2011100 (2011)