> movement. But then I don't know what kind of contamination levels would be
> acceptible. In a big field, a hundred pollen grains in the wrong place
Evidence is already available to suggest that this is a problem of
commercial magnitude, and it can only get worse as mainstream
grocery stores take up the non-GMO mantle and testing for GMO
contamination becomes more commonplace and sophisticated. Consider
the plight of the Texas farmer, who as i understand the story, had
grown corn organically, processed it into tortilla chips
and sent them off to Europe. They were found to have been
contaminated, reportedly by genetic pollution according to the
farmer, and sent back - at enormous cost to the farmer.
> might multiply into some serious contamination if seed were being saved and
> the contaminated types were inadvertantly selected. Of if only a very small
> amount of contaminated grains were needed to throw off tests for BT toxins,
> or the like. Seems like it wouldn't be hard to do a fast test (fast meaning
> in a few months) by planting a field of something with an innocuous, but
> obvious marker such as colored kernals next to a field of non-colored corn.
This may, or may not, be a suitable test - and either way, the fact
that we are having this discussion at all is a clear indication of
"technology before science" mentality. As is the case with the Bt
resistance problem (see latest issue of Science), companies were in
such a rush to make a buck, that they rammed through a technology
that is nothing if not externalizing of risk, without an adequate
grounding in science.
We don't know the pollination distances with certainty, although
they are known to be in km rather than meters for field-scale canola,
corn, and potato (I cite quite a lot of these figures, with
references, in a recent paper given to the Toronto Biotechnology
Initiative, a pro-biotech lobby group - see my homepage. We don't
know much of anything about allelic frequencies, dominance:recessive
relations, or many of the key parameters in the Bt resistance
question. Check out 1998 or 1999 refereed publications on the
subject, and you will be astounded at the degree to which they still -
even today - are based on assumptions in the absence of evidence.
The idea you propose may work, but it may not be generalizable because
individual GE events can affect such critical processes as %
outcrossing. See Bergelson et al., 1998 on the effect of putting an
herbicide resistance gene into Arabadopsis - a selfing species -
which turned some transgenic lines into 10% outcrossers. Outcrossing
has nothing to do with herbicide resistance, but is illustrative of
the general phenomenon of unintentional side effects caused by the
process of breaching the carefully modulated integrity of both species
and chromosome.
Recall that, contrary to the hype, GE is far from "precise".
Regardless of the method used, transgenes are inserted at random -
unreliably, unpredictably, and unrepeatably. According to my breeder
colleagues, there is still no method of knowing in advance where in a
given chromosome, or even on which chromosome, a presumptive
transgene will land. And, as I argue in a talk given on the weekend
(The Faulty Assumptions of Field Crop GE, hopefully to be mounted on
my homepage within a week or two), "order is everything". It makes a
difference where on a chromosome, and on which chromosome, a
transgene lands, because genes interact. Arguably, the genes
themselves do not matter so much as where they are on the
chromosomes. Interaction is everything. This explains, in large
part, why unintentional traits - such as outcrossing - can be
affected by GE. See Mae-Wan Ho's most helpful book Genetic
Engineering: Dream or Nightmare (1998).
What this means, is that pollination distances would have to be
tested for each commercial GE event - not generalized over the whole
species. Or, a worst case scenario would have to be adopted which
would wreck havoc on production and commerce. And keep in mind, we
are still thinking here on sexual outcrossing, without even
introducing the risk of horizontal gene transfer. Ann
ACLARK@plant.uoguelph.ca
Dr. E. Ann Clark
Associate Professor
Crop Science
University of Guelph
Guelph, ON N1G 2W1
Phone: 519-824-4120 Ext. 2508
FAX: 519 763-8933
http://www.oac.uoguelph.ca/www/CRSC/faculty/eac.htm
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