The following commentary on an article published in last week’s Nature describing UK’s farmscale field trials was rejected by the correspondence editor, "following discussion with our editorial team". This is not the first time that Nature has refused to allow real scientific debate on GM crops to take place in its pages.
Sir- Your report1 states, "The scientists behind Britain’s farm-scale field trials accept that they cannot answer all the questions surrounding the ecological effects of herbicide-tolerant GM crops – much less GM technology in general." Yet, like other previous reports in Nature, it persists in giving the impression that the battle is between "environmental group and organic farming movement" on one side and "science" on the other. There are at least two problems with GM technology that have been debated among scientists, genetic instability of GMOs, and their propensity for horizontal gene transfer due to the structural instability of GM constructs and their homologies with a wide range of bacteria and viruses.2,3
We have insisted that molecular data documenting genetic stability of transgenic lines must be provided before any environmental release.4 Unless a transgenic line is stable, one might as well forget about studying its long term environmental or health impacts. Unfortunately, none of the GM crops undergoing farm-scale field trials, or indeed, in commercial release elsewhere in the world, has been documented to be stable. And no studies on horizontal gene transfer are included in UK field trials.
The instability of GMOs is now generally recognised. Even the top ‘success’, Roundup Ready soya, is showing every sign of breakdown: reduced yield, non-germination, diseases and infestation by new pests.5 Molecular genetic characterisation, the first ever done on any commercially grown GM crop so far, has failed to confirm the structure of the insert originally reported. Instead, both the GM construct and the host genome have been scrambled (rearranged), and hundreds of basepairs of unknown DNA has got in as well.6
A risk assessment study funded by the European Commission (EC) concludes:7
"Biotechnology relies to a large extent on our ability to introduce foreign genes into cells. A major problem with present day technology is the non-predictability of the integration of such transgenes. DNA introduced into plant cells mostly integrates at random, i.e. at non-predetermined positions of the genome….DNA integrated at random frequently contains multiply copies and often copies are scrambled. Multiple copies also often induce gene silencing and hence instability in the expression of the introduced genes. In addition, the DNA integrates at loci of unknown stability and capacity for expression of randomly integrated copies may induce unpredictable and undesirable mutations in the host genome….we still lack the knowledge for precision engineering of plants’ genes."
The EC also funded research evaluating horizontal gene transfer from GMOs to the microflora and in animal gut.8 It notes that the risks of "horizontal gene transfer cannot be excluded", and, "Free DNA persists in some materials for weeks, and furthermore, some bacteria develop natural/chemical competence to take up DNA from the environment. In addition, in the gastrointestinal tract of man and husbandry animals, DNA may remain stable for some time, particularly in the colon."
Finally, the new European Directive 2001/18 /EC on deliberate release of GMOs has now been agreed. Apart from the stricter requirements for long term ecological and health impact assessments, it also stipulates molecular data documenting that the GMO is genetically and phenotypically stable. These criteria, if strictly implemented, will disqualify most, if not all current GMOs, for environmental release, including those undergoing UK farm-scale field trials.
Article first published 31/08/01
Mae-Wan Ho
Angela Ryan
Institute of Science in Society
Joseph Cummins
Department of Plant Sciences
University of Western Ontario, Canada
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