GENETIC pollution in the field is very unlikely. as far as i
know, european scientists are debating a tolerance level of about
3 percent for the impurities. every value below is ignored as
impurity, because the analytical tools (chromatography, sds-page
and isozyme electrophoresis) are not that exact as many might
expect (for seed certification we do it on 400 single seeds for %
evaluation, but i have not the slightest idea, how institutes for
food control analyse foodmixtures or processed food, it's certainly
more difficult). add the statistical error 1. order and you should
be somewhere near these 3 percent as analytical limit. polymerase
chain reaction is out of question, because it is MUCH TOO sensitive
for this kind of analysis and more a qualitative than a
quantitative tool (and because of the high number of replicates
needed also too expensive).
it is MUCH more probably, that somewhere in the production chain
someone (either the farmer hinself or the manufactorer of the
chips) tried to make some "extra" money by mixing up the higher
priced organic bulk with some cheap GM corn, hoping, that noone will
find out. once trapped and being forced to carry it back you
would expect them to confess their cheap trick ?? it is easier to
shift it to genetic pollution in the field.. no ! 3 % (that is
the smallest number to be rejected) pollution from a neighbor
field are VERY unlikely for corn. from time to time i myself am
confronted with these tricks. you ask the owner of the analytical
sample, as it is evident and the first thing you hear, is a
indignant denial. ask further and tell him, that you are no
regulatory institute or the executive, and you'll hear a
confession. really, i'm quite used to that and as our work as
consultants depends on the confidence between us and the farmer,
over time they learned, that none of them is sacked by our
institute ! so they are quite frankly telling practical tricks.
i'm sure, every consultant knows this problem very well. tell the
police that a farmer told you, he is using an illegal
antibioticum and next time you visit his farm, you are driven
away with the fork...
it would be interesting to see the analytical certificate (which
would not give an exact number, but a range of pollution
percentages like: "between x and y % impurity").
i found values for rape seed and they are quite low :
lefol e. danielou v. darmency h.
predicting hybridization between transgenic oilseed rape and
field crops research. 45(1-3):153-161, 1996 may.
overlap between flowering of oilseed rape (brassica napus var.
oleifera metzger)an wild mustard (sinapis arvensis l.),
artificial hybridization between the two species, spontaneous
crosses, and backcrossing were assessed to estimate the risk of
escape of genes from transgenic crops towards the wild species.
in the burgundy-ion of france, wild mustard flowers later than
oilseed rape. exposure to cross pollination was two to five
times greater with late-flowering cultivars than with early
cultivars. artificial hybridizations using in vitro ovary
culture produced up to 1 seed per 100 pollinated flowers. no
hybrid was found among 2.9 million seeds produced by wild
mustard grown in a garden in presence of a herbicide-resistant
transgenic cultivar. no more than six hybrids were obtained
from 50000 flowers of a male-sterile oilseed rape grown in
presence of wild mustard. artificial hybrids grown in presence
of wild mustard, or hand-crossed, produced a few aborted seeds.
thus, in similar ''normal conditions'', it may be concluded
that a flower of these two species has a probability smaller
than 10(-10) of having an interspecific hybrid progeny.
if the farmer is an organic farmer it may be unlikely, that he is
the source of contamination, if he ONLY grows organic corn. (but
not impossible: cheap bulk from neighbor, contamination by a
hired harvester aso. the last one happens quite often at "our"
seed multipliers, but certainly not in the range of percents)
which brings me to a question: is it allowed in america to
separate his farm organisation and the fields into an organic
part and and a conventional one under the obligation to separate
the two parts and the grown fruit strictly ?
>We don't know the pollination distances with certainty, although
>they are known to be in km rather than meters for field-scale
i'm sure, a breeder of hybrid corn will know these distances very
well (in fact for seed certification he needs to know them and
the possible cross pollination rate, because western europe seed
law requires a maximum number of impurities for other varieties
in certified seed) and the distances for seed production are
certainly not in the range of more than 250 m for corn. pioneer
multiplies a lot of corn in austria and hungary and i know the
analyst from the neigbour institute, who some years ago did most of
the crosspollination analyses for the hungarian seed multipliers.
i'll try to ask him for more info.
>know much of anything about allelic frequencies,
>relations, or many of the key parameters in the Bt resistance
>question. Check out 1998 or 1999 refereed publications on the
do you expect another pollination rate for gm corn than for
conventional corn ? if so, why ?
for rape it seems to be the same:
lefol e. fleury a. darmency h.
gene dispersal from transgenic crops .2. hybridization between
oilseed rape and the wild heavy mustard
sexual plant reproduction. 9(4):189-196, 1996 jul.
the risk of release of genetically modified oilseed rape
(brassica napus) was investigated in relation to interspecific
gene flow with hoary mustard (hirschfeldia incana). microscopic
studies showed polymorphism within the population of hoary
mustard for pollen germination on oilseed rape flowers. the
transgenic herbicide-resistant and a commercial cultivar of
oilseed rape were not different for pollen behaviour and ovule
fertilization. pollen tube growth was slow and erratic in
interspecific crosses. fertilization efficiency of oilseed rape
and hoary mustard pollen [..]
>unreliably, unpredictably, and unrepeatably. According to my
>colleagues, there is still no method of knowing in advance where
>given chromosome, or even on which chromosome, a presumptive
>transgene will land.
>What this means, is that pollination distances would have to be
>tested for each commercial GE event - not generalized over the
pollination is influenced by weight, number, fertility, maturity
and "stickyness" of the pollen, by self incompatibility, size of
the pistil and form of the petals and the "willingness" of the
antheres to open, also by wind and by air humidity, by density of
the plant stand and by the time from opening of the flower to
pollen contact, color of corolla, extension of stamens and
carpels and availablity of pollinators, but i do not believe it
to be a factor of the position of the gm proteins in the genome..
so i'do not understand, what you want to explain with the sentence
above. would you please explain ?
some corn breeders reading here, who might share their
Landwirtschaftl. Untersuchungs- u. Forschungsanstalt (LUFA)
(Governm. Inst. for Agricult. & Environm. Res.)
67346 Speyer, Obere Langgasse 40 (GERMANY)
Dept. of Seed Sci., Microscop. Analysis & Plant Pathol.
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