Study reveals first evidence that GM superweeds exist

[Mike Friedman <mikedf@xxxxxxxx>]

Most of the critiques of genetically modified organisms that I've read have
dealt with potential direct side-effects of genetic modification, such as
the production of toxic substances, or ecological imbalances, or
unforseeable genetic-environmental interactions. However, this article
brings up another potentially disasterous consequence of GM crops. Any
plant systematist will tell you that horizontal gene transfer between
unrelated species of plants (unlike animals, for the most part) may account
for a large percentage of existing plant species. Think about the
consequences if such transfers incorporated genes coding for pesticide
resistance in unrelated species.

Mike
---------------

http://news.independent.co.uk/uk/environment/story.jsp?story=451733


Study reveals first evidence that GM superweeds exist


By Steve Connor Science Editor


10 October 2003


Cross-pollination between GM plants and their wild relatives is
inevitable and could create hybrid superweeds resistant to the most
powerful weedkillers, according to the first national study of how
genes pass from crops to weeds.


Its findings will raise concerns about the impact of GM crops. Next
week the results will be published of farm-scale trials which have
studied the impact on the countryside of three types of crop.


The government-funded scientists said the latest findings "contrast"
with previous assessments of gene flow between farm crops and weeds.
They had suggested that the danger of hybridisation - where two types
of plant cross-pollinate to create another, for example a superweed -
was limited. Superweeds are considered to be a threat because, in
some cases, they might absorb resistance to weedkillers from GM crops
engineered to be herbicide-tolerant.


But the results of the research, which involved analysing satellite
images of the British countryside and patrolling 180 miles of river
banks, reveal that hybridisation is both more widespread and frequent
than previously anticipated.


Mike Wilkinson of Reading University, who led the study published
today in the journal Science, said physical barriers such as
isolation distances - buffer zones designed to stop pollen spreading
from GM crops into the wild - would have only a limited impact on
preventing hybridisation.


"This [study] shows that isolation distances will reduce hybrid
numbers but not prevent hybridisation. It depends on what level of
hybridisation you deem acceptable but if you want to absolutely
prevent hybrids then isolation distances will not do so," Dr
Wilkinson said. "Hybridisation is more or less inevitable in the UK
context," he added.


The study concentrated on non-GM oilseed rape and assessed how easily
it cross-bred with a near-relative in the wild called bargeman's
cabbage, also known as wild turnip, which typically grows along river
banks. Although the research was based on conventional oilseed rape,
Dr Wilkinson said the conclusions applied to any flow of genes that
could be expected from the GM varieties of oilseed rape that were
undergoing farm-scale trials.


"Our findings are directly transferable to almost all sorts of
genetically modified oilseed rape," he said. "The only exceptions
will be ones where there is male sterility introduced into the crop."


Researchers scoured the countryside for sites where bargeman's
cabbage grew near to oilseed rape fields and they used DNA techniques
to assess whether any hybrids between the crop and the wildflower had
been produced as a result of pollen transfer.


The scientists, from the Natural Environment Research Council and the
Centre for Ecology and Hydrology in Dorset, calculated the frequency
of hybridisation and used it to estimate the number of hybrids that
would form each year across the UK.


They concluded that typically there would be 32,000 hybrids produced
annually in wild riverside populations of bargeman's cabbage, and a
further 17,000 hybrids growing among a weedier variety of the
wildflower which tends to infest farmland. This represents a
relatively small fraction of the 88 million wild bargeman's cabbage
plants estimated to grow along British riverbanks, but if the
hybridisation involved a GM gene that conferred a significant
advantage on the weed, the hybrid could quickly spread to pose a
superweed threat.


An important outcome of the work is that it will allow scientists to
assess what needs to be done to limit the spread of genes and pollen
from GM crops. One possibility is to make the male plants sterile so
they do not produce pollen.


"If we know how many hybrids to expect then we can test methods that
people put forward hoping to prevent hybrid formation. In order to
prevent hybrid formation you need to know how many to expect in the
first place," Dr Wilkinson said.


"One of the main reasons for doing the work is that this sort of data
represents a starting point for us to do predictive modelling, to
predict how particular different sorts of genes will behave across
the country.


"It's important to know how many hybrids to expect, to know how
efficient it has to be to prevent hybrids. The key question is
whether the gene that they contain is going to cause a change [to the
countryside] or not," he said.


Although the latest study stands in contrast to previous work
attempting to predict gene flow between farm crops and wild flowers,
Dr Wilkinson said the findings were not totally surprising. "The
level of hybrid formation is more or less in keeping with what we
expected on a national level," he said. "What's surprised us slightly
is the variability between the regions."


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