A herbicide-resistant weed has been found in a field used for the UK鈥檚 farm-scale evaluations of genetically-modified crops but 鈥� despite the claims of several media reports 鈥� it is no GM 鈥渟uperweed鈥�, say scientists.
Researchers at the Centre for Ecology and Hydrology in Dorset, UK, tested the herbicide glufosinate ammonium on plants in fields previously sowed with oilseed rape modified to carry a gene conferring resistance to the herbicide. But a single charlock plant carried on growing happily, raising fears that the gene for herbicide resistance had crossed over to the charlock and created a herbicide-resistant strain. But this is not proof that gene transfer has taken place, says Les Firbank, head of land use systems at the CEH.
鈥淎nd even if it did occur, it鈥檚 not a superweed,鈥� stresses Firbank, 鈥渂ecause there鈥檚 no sign it can produce viable seeds.鈥�
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Gene transfer has been shown in the lab to be possible between GM oil seed rape 鈥� Brassica napus 鈥� and a closely related species, field mustard 鈥� Brassica rapa. But there is not yet proof that it occurred between oilseed rape and the more distantly related charlock, Sinapis arvensis.
Natural resistance
鈥淭here is no superweed and there never has been,鈥� echoes Brian Johnson, ecological geneticist at English Nature, the nature advisers to the British government. 鈥淚t鈥檚 more likely that herbicide resistance in charlock has evolved naturally.鈥�
But according to some media reports, genetic testing of the purported hybrid showed that it carries the same gene as the GM crop.
鈥淲e鈥檙e not at all convinced it contains the gene construct,鈥� Johnson reaffirms. 鈥淲e still remain concerned about gene transfer,鈥� he adds, 鈥渂ut not about the transfer of resistance to a single herbicide. We鈥檙e more concerned about traits that may change fitness, such as insect resistance or drought- or salt-tolerance.鈥�
In the wake of the media attention 鈥� which followed publication of the CEH鈥檚 study by the UK鈥檚 Department for Environment, Food and Rural Affairs 鈥� the German biotech company Bayer has withdrawn its application to grow GM oilseed rape in the EU. Bayer was the only company to have applied for permission to grow GM oilseed rape commercially in Europe.
