PLANTS: MON810 Bt maize: "The variations are within a biologicallyexplainable range."
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Dear GENET-news reader,
it is interesting to read in this reply on a recently published
Greenpeace study on wide variations of the Bt content in MON810 GE maize
that "the variations [in Bt content] were within a natural, biologically
explainable range" when at the same time neither this article nor the
original publication by Dr. Jehle provides any sound biological
explanation or mechanisms for these variations. Similar astonishingly
is, that Dr. Jehlen tries to imply that the methodology used by the
Ecostrat researchers has been developed by Greenpeace while Dr. Jehle
has used a more reliable test system: "In the DLR study we used a
standard commercial Bt detection test that had been validated again at
DLR Rheinpfalz. Greenpeace evidently used a different detection method
that they had developed themselves." The method used in the Greenpeace
study has actually been described in a peer-revied study written by
renowned experts in Bt and biosafety research: "The Bt toxin in the
maize leaf samples was quantified by the Ecostrat laboratory (in
Switzerland) by Double Antibody Sandwich ELISA (DAS-ELISA), as described
by Zwahlen et al. (2003)." [Zwahlen, C., A. Hilbeck, P. Gugerli & W.
Nentwig (2003). Degradation of the Cry1Ab protein within transgenic
Bacillus thuringiensis corn tissue in the field. Molecular Ecology 12:
765-775.] And last not least it is revealing that the article does not
say a single word about the fact that Monsanto sells a product has
contains much less Bt protein - the ingredient the farmers pay for -
than claimed. The need for quality control in GE crop seeds is apparent.
------------------------------- GENET-news -------------------------------
TITLE: "The variations are within a biologically explainable range."
SOURCE: GMO Safety, Germany
Measurements of Bt toxin concentration in Bt maize
"The variations are within a biologically explainable range."
The Bt concentration in insect-resistant maize is not the same in every
plant. Greenpeace has carried out measurements to check this and found
that the Bt levels varied considerably. Greenpeace claims that the legal
basis for the EU approval has not been fulfilled. Johannes Jehle of the
Dienstleistungszentrum ländlicher Raum (DLR) in Neustadt an der
Weinstrasse does not agree with either the results or the conclusions of
the study. He led a three-year research project in which Bt levels in
genetically modified MON810 maize were measured. GMO Safety asked him
When genetically modified Bt maize is grown, not all plants produce
exactly the same amount of the Bt toxin , a substance that is effective
against pests. Like most plant substances, the Bt concentration is
subject to certain natural variations. This has been known for a long
time. Yet last year Greenpeace took a total of 600 leaf samples from
several fields of MON810 Bt maize in Germany and Spain and asked a
laboratory in Switzerland (Ecostrat) to examine the Bt concentrations in them.
Greenpeace presented the results publicly on 11 May 2007. They claim
that the Bt content varies by a factor of as much as a 100 between
individual plants. Although even Greenpeace had to admit that the levels
of Bt in the leaves were "surprisingly low" and considerably lower than
the value given by Monsanto in the approval documentation. But since the
"reasons for such differences and the range of variation cannot be
identified", Greenpeace concludes from its research that "the commercial
cultivation of the crops should be stopped."
A project funded as part of the biological safety research programme of
the Federal Ministry of Education and Research (BMBF) also dealt in
depth with the measurement of Bt levels in MON810. In April 2007
Johannes Jehle and Hang Thu Nguyen of the DLR in Neustand/Weinstrasse
published their results in a scientific journal.
GMO Safety: In the BMBF-funded safety research project you also found
significant variations in the Bt toxin concentrations in the plants.
What do you believe was the cause of the variations?
Johannes Jehle: We were able to demonstrate that Bt expression varies
depending on the plant organ under investigation, the stage of
development, the location and therefore the weather. Many of these
differences are statistically significant. In addition, varietal
variations cannot be ruled out, although this is not something we examined.
GMO Safety: In the Greenpeace study they found variations of between 0.1
and 10 µg/g fresh weight in some cases (factor of 100). Were the
variations you found equally great? Do you view such variation ranges as
Johannes Jehle: In our three years of measurements, the maximum
variation range (ratio of maximum expression to minimum expression
depending on the development stage) was a factor of between 3 and 5; in
extreme cases as much as 14. However, the variation coefficients derived
from the ratio of standard deviation to mean value are far more
meaningful than a comparison of these extreme values. The variation
coefficients in our investigations were between 20 and 60 per cent. In
the Greenpeace study they were over 200% in some cases. This means that
over a period of three years with extreme weather differences, the
variations we measured were 3-10 times smaller overall than those in the
one-year Greenpeace measurements. This means that we are unable to
corroborate the Greenpeace measurements with our research.
A variation range such as that measured by Greenpeace in some cases
would of course have a different significance in agronomic terms than
the variability we measured. In the DLR study we used a standard
commercial Bt detection test that had been validated again at DLR
Rheinpfalz. Greenpeace evidently used a different detection method that
they had developed themselves. Because of the different measurement
methods, the DLR and Greenpeace measurements are almost certainly not
GMO Safety: In your view, do the observed variations between plant
individuals and locations present problems for the safety assessment?
Johannes Jehle: No. We saw no grounds for this based on our data, since
the variations were within a natural, biologically explainable range.
GMO Safety: As with the Greenpeace study, the average values were below
the Bt concentrations given by Monsanto in its application
documentation. How do you explain this?
Johannes Jehle: Our measurements were on average around 30 to 40 per
cent below published data from the 1990s. It would certainly be useful
to have more published comparable data from other growing regions. Our
work is an important step in this direction. As I mentioned, the
location and stage of development are the most important factors in the
level of expression, and possibly also the varietal background. Certain
differences in measurements can also arise from different extraction
methods and different protein detection standards. But we definitely see
no direct indication of genetic instability - the variability would have
to be much higher for that.
GMO Safety: What impacts could the lower Bt concentration have on the
Johannes Jehle: The safety assessment is not performed by us, although
the responsible authorities can make use of our data. However, in terms
of the Bt concentrations we observed, I see no reason to cast doubt on
the safety assessment. Despite the lower Bt concentrations and the
observed variations between plant individuals, our results largely
corroborate the known findings of earlier studies and do not tally with
the Greenpeace measurements.
GMO Safety: Thank you for talking to us!
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