Use your BACK button to return to article index.
There is now so much evidence of harmful toxic effects associated
with BT varieties that all past approvals by the EC must be
revisited. The approvals procedures for GM varieties "in the pi
[peline" must also be stopped instantly. If they are not, that
would be interpreted by any reasonable person as criminal negligence
by EFSA and by Commissioners Dimas and Kyprianou in particular.
Note the cases of "toxic shock" leading to animal deaths:
Cows ate GM maize and died (BT176)
http://www.i-sis.org.uk/CAGMMAD.php
25% death rate among sheep which grazed on Bt cotton plants in India
http://www.gmwatch.org/archive2.asp?arcid=6499
http://www.gmwatch.org/archive2.asp?arcid=6494
Note also the effects on human health arising from contact with Bt
varieties:
http://www.i-sis.org.uk/full/MILTBTFull.php
http://www.gmwatch.org/archive2.asp?arcid=6472
Some Australian research not widely reported.......... It refers to
Cry1Ac toxin and backs up the findings of the Hungarian team
including Bela Darvas, whose findings for MON810 maize are appended
at the base of the page.
From Gupta and Watson:
Quote: " ..... We have shown that different plant parts of Bt cotton
(leaves, stubble and roots) contain large concentrations of Bt toxin
and therefore have the potential to be a reservoir of Bt toxin in
agricultural fields of Australia."
Quote: "............ our results suggest that Bt toxin has the
potential to enter the soil system throughout the Bt cotton growing
season, through both a root release process and root turnover. Levels
of Bt toxin entering the soil system could therefore be significantly
higher than previously suggested ......."
Quote: " ..... roots with Bt toxin are in constant contact with the
soil system (including soil biota) and Bt toxin levels in fine roots
were found to be as high as that in younger leaves. In view of the
results reported above (large concentrations of Bt toxin in Bt cotton
roots and demonstrated root release), more detailed investigations on
the environmental fate of the root-derived Bt toxin, binding to soil
components and build up, and movement beyond the rhizosphere and root
zone, are warranted."
The concerns of the authors shine through, although they are careful
(so as to keep their paymasters happy) not to flag up "harm" or even
the potential for harm. We can see the heavy hand of CSIRO here, in
playing down the significance of the findings. But this research is
very relevant, given the new revelations about sheep deaths in India
among animals grazing on Bt cotton plants.
=============
Ecological impacts of GM cotton on soil biodiversity
Below ground production of Bt by GM cotton and Bt cotton impacts on
soil biological processes
Dr Vadakattu VSR Gupta and Dr Stephanie Watson
Consultancy report by CSIRO Land and Water, August 2004
http://www.deh.gov.au/settlements/publications/biotechnology/gm-
cotton/summary.html
Summary
This research programme focuses on the impacts of genetically
modified (GM) cotton crops (Bacillus thuringiensis cotton; Bt cotton
for short) on soil biodiversity and ecosystem function. The
experimental work was based upon the need to establish the risk of
production and release of Bt toxin by below ground plant parts of
cotton and its potential persistence in the soil where Bt cotton
crops are grown in Australia. In addition, the potential impacts of
new gene products may affect key soil biological processes essential
for a number of ecosystem functions.
Genetic modification of organisms (plants, microbes and animals) to
incorporate useful traits is a powerful technology for the future
development of sustainable agricultural systems. Transgenic cotton
varieties modified to express the Cry1Ac insecticidal toxin (Bt
cotton) that is toxic to some insect pests are now grown in
Australia. However, little experimental data (especially
quantitative) is available on the environmental consequences of
sustained expression and/or presence of Bt toxin in various parts of
Bt cotton plants. In addition very little is known about the
potential for the persistence of Bt toxin released from Bt cotton
plants in Australian cotton soils.
Soil biota mediate or regulate a variety of functions essential for
plant growth and productivity, soil resource structure, and ecosystem
health. Soil biota are diverse in terms of their physiological
nature, size and environmental requirements. The composition and
metabolic capabilities of the soil microbial and faunal communities
underpin the occurrence and rates of many soil processes. Microbial-
faunal (micro-, meso- and macrofauna) interactions play a critical
role in a variety of biological functions both in the rhizosphere
(the zone directly surrounding and influenced by roots) and the soil
near decomposing plant residues. Plant residues are the primary
source of metabolic energy (carbon) in Australian soils and the
majority of biota populations and biota-mediated processes are
concentrated in the rhizosphere and near crop residues. Therefore any
change to the quality of crop residues and rhizosphere inputs will
potentially modify the dynamics of soil biota composition and
activity (Gupta et al., 1998 and 1999). Genetically modified plants,
through (1) the products of introduced genes, (2) modified
rhizosphere chemistry, or (3) altered crop residue quality, have the
potential to significantly change the microbial dynamics, soil
biodiversity and essential ecosystem functions such as nutrient
mineralisation, disease incidence, carbon turnover and plant growth.
While reduced pesticide use associated with Bt cotton varieties is
clearly beneficial, very little is known on the potential non-target
effects of Bt cotton plants on the functional groups of soil biota
and associated biological processes that are critical for sustained
cotton productivity and essential for ecosystem health.
It is known that the Bt cotton varieties produce Bt toxin in above
ground plant parts such as leaves (particularly young leaves), flower
buds etc. but no information is available on the production of Bt
toxin in the below ground plant parts. In addition it has been
assumed that "during the life of the plant the Bt-endotoxin in Ingard
cotton is enclosed within plant cells and it would only enter the
soil environment after the above ground plant material is ploughed
in" (NRA, 1996).
In this project we measured the levels of Bt toxin production in
different plant parts of cotton, especially below ground parts, and
also evaluated the mechanisms through which the Bt toxin enters the
soil environment. We found that in controlled environments
(glasshouse and growth chamber) and field experiments, Bt cotton
varieties expressed Bt genes and produced measurable amounts of Bt
toxin in different parts of the cotton root system (tap, secondary
and fine roots, and root hairs). Our results indicate that the levels
of Bt toxin in roots are similar to those observed in leaves whereas
the levels of Bt toxin in stems were the lowest. For example, Bt
toxin levels in the leaves of cotton variety Sicot 289i ranged from
2,900 to 20,300 ppb and in the roots from 4,900 to 18,700 ppb.
The general decrease over time of Bt toxin levels in leaves is
generally accepted (especially in Ingard varieties) to be due to the
ageing of the various plant tissues and gradual breakdown of Bt toxin
within these tissues. However, we found that as the plants grew
older, the levels of Bt toxin in roots of 8-week old Bt cotton (Sicot
289i) were higher (4,900 and 7,000 ppb dry weight in taproot and fine
roots, respectively) than that in leaves (2,900 ppb dry weight). We
also found that in most situations Bt toxin levels in the fine roots
were higher than other parts of the root system and plant-related
reductions in this part of the root system were smaller compared to
other plant parts. This higher level of Bt toxin below ground can be
attributed to the continued growth of new root systems through the
later stages of the cotton season.
We observed the presence of Bt toxin in the roots of Bt cotton
varieties grown in three different soils (Avon, SA, Waikerie, SA and
Narrabri, NSW). The results show that Bt toxin was produced in every
major part of Bt cotton plants (leaves, stems, and roots), that root
Bt toxin production was comparable (or higher in the later stages of
cotton plant) to that in cotton leaves and that the above
observations held true for all three soil types. In these experiments
we did not find any detectable levels of Bt toxin in the conventional
non-Bt cotton plants.
We also found that the roots of Bt cotton varieties release Bt toxin,
both in vitro (solution culture) and by soil-grown plants, through
presumably passive release from the roots or as cell lysates, and the
levels of release (cell-free) of Bt toxin from roots were
significantly increased ( > 6-fold) following any damage to root
system (eg fine roots). The non-Bt cotton cultivars, as expected,
released no detectable Bt toxin. We found Bt toxin release from
plants that were 2 to 12 weeks old and found no evidence for the
presence of Bt toxin from roots of non-Bt cotton varieties.
Root hairs and sloughed epidermal cells contribute a significant
amount of root material in the rhizosphere of actively growing
plants. We found that the sloughed epidermal cells and fine-root hair
fragments from Bt cotton (Sicot 289i) plants contained large
concentrations of Bt toxin (eg 1317 ppb/g wet weight) whereas non-Bt
control (Sicot 189) cells/fine-root hairs showed no Bt toxin. Thus,
our results suggest that Bt toxin has the potential to enter the soil
system throughout the Bt cotton growing season, through both a root
release process and root turnover. Levels of Bt toxin entering the
soil system could therefore be significantly higher than previously
suggested on the basis of contributions of Bt toxin to soil from
above-ground cotton material only (NRA, 1996)*.
* A more recent assessment by the Australian Pesticides and
Veterinary Medicines Authority, for Bollgard II cotton, does consider
the contribution of Bt toxin from root sources (APVMA 2003).
Unlike the Bt toxin from leaves and other above ground plant parts,
which may enter soil only after defoliation (leaves) and cotton
harvest (stems), roots with Bt toxin are in constant contact with the
soil system (including soil biota) and Bt toxin levels in fine roots
were found to be as high as that in younger leaves. In view of the
results reported above (large concentrations of Bt toxin in Bt cotton
roots and demonstrated root release), more detailed investigations on
the environmental fate of the root-derived Bt toxin, binding to soil
components and build up, and movement beyond the rhizosphere and root
zone, are warranted. Results from our initial work found detectable
levels of Bt toxin in the rhizosphere of Bt cotton varieties by using
both immunological tests and insect bioassays.
Leaf material, in general, constitutes a major component of the
easily decomposable part of crop residues and therefore supports
larger populations of soil biota and higher levels of biological
activity. Results from leaf decomposition experiment have shown that
detectable levels of Bt toxin were observed in decomposing leaves
throughout an 8-week field incubation experiment. The implications of
the presence of Bt toxin for the composition of soil biota (soil
fauna and microflora) during the main period of leaf material
decomposition are unknown. Therefore, there is a clear need for
further detailed investigations on the impacts of both leaf- and root-
derived Bt toxins on soil biodiversity and associated biological
functions.
Microbial growth indicators measured in this study (decomposition
rates, substrate induced respiration, and respiration quotients)
suggest that microbial population growth on Bt cotton leaf litter
might be different than for non-Bt varieties. Microscopic examination
revealed an apparent increase in fungi and fungal spores on the Bt
cotton residues compared to the non-Bt residues. Experiments did not
indicate whether these changes were likely to be detrimental, neutral
or beneficial in an agricultural situation. These experiments need to
be repeated over multiple seasons before firm conclusions can be drawn.
In summary, our work clearly demonstrates the evidence for avenues,
other than through leaves, for Bt toxin to enter the soil system
throughout the cotton growing season. This is contrary to the
previous assumption that "it only enters after the above ground plant
material is ploughed in" (NRA 1996). Our results indicate that
rhizosphere-inhabiting soil biota are continuously exposed to Bt
toxin produced in the roots (through root releases and root turnover)
throughout the growing season and then further exposed as crop
residues decompose after harvest.
In Australian soils, the rhizosphere environment is one of two key
zones where the majority of soil biota reside, the other zone being
the soil around decomposing crop residues. Populations of different
groups of microbiota are generally higher (>10-fold) in rhizosphere
soils compared to that in bulk soil, and rhizosphere biological
activity accounts for >60% of overall soil biological activity.
Implications of our results on Bt toxin production and release below
ground by Bt cotton varieties are that the input from Bt cotton roots
has previously been significantly underestimated and the impacts of
this hitherto unknown, toxin input are yet to be fully investigated.
We have shown that different plant parts of Bt cotton (leaves,
stubble and roots) contain large concentrations of Bt toxin and
therefore have the potential to be a reservoir of Bt toxin in
agricultural fields of Australia. Our findings showing large
concentrations of Bt toxin (above soil background) in decomposing Bt
cotton leaf residues even after the decomposition of >40% of leaf
residue indicate that Bt toxin from dead leaves is not easily
degraded by soil microorganisms, which one would expect for such a
protein substance. If more Bt toxin enters the soil environment than
is degraded by microbes, eaten by insect larvae or inactivated by
sunlight there is potential for the toxin to accumulate if it is
bound and protected by soil particles (clays, minerals and humic
acids). Could accumulation of active Bt toxin constitute a hazard to
non-target organisms and impact the biodiversity and functionality of
the organisms inhabiting the soil?
Soil fungi associated with decomposing crop residues could be either
non-pathogenic species or species that cause soilborne plant
diseases. Crop residues are the primary source of carbon for soil
biota populations in Australian soils hence the composition of biota
associated has a great significance in regulating the essential
biological functions in the ecosystem. Observations on differences in
microbial populations, including a possible increase of fungi on
decomposing Bt-cotton, require further investigation over more than
one season before differences can be confirmed. If the observed trend
is real, its significance is not yet clear since the changes to soil
biota could be detrimental, neutral or beneficial to agricultural
soil ecosystems.
Finally, consideration of the environmental fate of Bt toxin from Bt
crops has sometimes focussed only on the expression of the Bt gene in
above-ground plant parts, but our results suggest further
investigation into the environmental fate of the root-released Bt
toxin in soil is required, both during the cotton season and
following the harvest of the cotton crop.
This project is based with the CSIRO Land and Water group in Adelaide
with collaborative links for fieldwork with researchers at Australian
Cotton Research Institute (ACRI) research farm in Narrabri, NSW (Mr.
Grant Roberts, CSIRO Plant Industry).
Australian Government, Department of Environment and Heritage. 2005.
Summary of the Ecological Impacts of GM Cotton on soil biodiversity
report.
Note: the material presented in this document is in preparation for
publication in the scientific literature.
========================
The Hungarian team found the following for MON810 maize:
"The Bt maize produces 1500-2000 times as much Bt-toxin as is
released through
a single treatment in conventional crop protection, with the chemical
called DIPEL,
which contains Bt toxin."
II. "Other experiments have found that the residues of Bt plants are
slower to
decompose than their isogenic lines. Some 8% of the toxin produced by
the plant
remained in the field after harvesting. Indeed, a substantial share
of this active
toxin quantity could be identified in the soil 11 months later."
III. "In the soil of the field under the transgenic plant, the entire
biological activity was
lower than in the control field."
IV. "The caterpillars thriving on herbs in and on the edges of maize
fields, hatching
during the pollination period, are the most substantially affected by
the Bt toxin
produced by MON 810.. Shades of Bt176 maize and dead cows etc, and
now the news of a 25% death rate among sheep consuming the foliage of
Bt cotton in India??