India
August 8, 2005
T. V. Padma,
SciDev.Net
A study* has found that Indian varieties of cotton that have been
genetically modified to resist an important insect pest are
"inadequate".
The findings
back farmers' claims that the pest, known as the bollworm, is
able to survive on Bt cotton varieties, modified to resist it.
Prompted by
the study, the president of an agricultural lobby group in India
is demanding an enquiry into whether the government continued to
release the "inadequate" varieties, despite knowing their
shortcomings.
The
researchers, who published their findings in the Indian journal
Current Science last week (25 July), say farmers may have
to be prepared to use additional insecticide in the later stages
of growing the crop.
Bt cotton is
genetically modified to produce a toxin lethal to bollworms,
which cause an estimated US$1 billion worth of damage in India
each year. It is patented and sold by the US firm Monsanto.
In Australia,
China, Indonesia, and South Africa farmers grow Monsanto's Bt
cotton as it is sold by the company. In India however, under a
license from Monsanto, the Bt cotton is repeatedly crossed with
Indian varieties to adapt it to the country's wide range of
growing conditions.
The Indian
government cleared the first three hybrid cotton varieties for
commercial cultivation in 2002. More were cleared for planting
in subsequent years.
In 2003,
scientists from the Indian Central Institute for Cotton Research
(CICR) tested eight commercially grown hybrids. They found that
some hybrids produced up to seven times as much toxin as others.
In addition, differing amounts of toxin were found in different
parts of individual plants.
Generally,
the ovaries of the flowers and the rinds of the cotton bolls,
which are favoured by the bollworm, contained the least amount
of toxin, while leaves contained the highest levels. The amount
of toxin declined progressively as the plants grew, and dropped
below effective levels 100 days after the seeds were sown.
The toxin
levels in the boll rind and flowers are "clearly inadequate" to
fully protect the fruiting parts of the plant against the
bollworm, the scientists report.
They say the
findings help to explain complaints from Indian farmers that
bollworms can survive on Bt cotton plants.
Several
non-government organisations, including Greenpeace, the
Dehli-based Gene Campaign
and the Rural Foundation for Science, Technology and
Environment, have reported instances of farmers complaining of
Bt crop failure, but these were dismissed by the government and
scientists as unsubstantiated.
On Wednesday
(3 August) Suman Sahai, the president of Gene Campaign, wrote to
the secretary of India's Ministry of Environment and Forests
demanding an enquiry into whether the government released more
Bt cotton hybrids for commercial cultivation despite knowing the
early trends of CICR findings.
Already in
2003, the CICR filed a report to the Genetic Engineering
Approval Committee, a body of the environment ministry,
indicating that the levels of toxin in Indian Bt cotton might be
insufficient to control the pest.
In her letter
to the ministry, Sahai says the approval committee violated
India's 1986 Environment Protection Act by not making CICR's
early findings public.
The
committee's website provides access to the 2002-2003 and
2004-2005 CICR reports, but not to the 2003-2004 report which,
according to Sahai, would have contained its preliminary results
on Indian Bt cotton.
Sahai has
sent copies of her letter to the Indian prime minister and the
minister for the environment. Neither has yet responded.
The secretary
of the environment ministry told SciDev.Net the ministry has not
yet received Sahai's letter.
Reference:
Current Science 89, 291 (2005)
* Temporal
and intra-plant variability of Cry1Ac expression in Bt-cotton
and its influence on the survival of the cotton bollworm,
Helicoverpa armigera (Hübner) (Noctuidae: Lepidoptera)
K. R. Kranthi*, S. Naidu, C. S. Dhawad, A. Tatwawadi, K.
Mate, E. Patil, A. A. Bharose, G. T. Behere, R. M. Wadaskar and
S. Kranthi
Central Institute for Cotton Research, P.B. No. 2,
Shankarnagar PO, Nagpur 440 010, India
ABSTRACT
The
quantitative levels of Cry1Ac and the seasonal decline in
expression differed significantly among the eight
commercial Bollgard hybrids tested. The Cry1Ac expression was
found to be variable among the hybrids and also between
different plant parts. The leaves of Bt-cotton plants were found
to have the highest levels of Cry1Ac expression followed by
squares, bolls and flowers. The toxin expression in the
boll-rind, square bud and ovary of flowers was clearly
inadequate to confer full protection to the fruiting parts.
Increasing levels of Helicoverpa armigera survival were
correlated with the toxin levels decreasing below 1.8 mg/g in
the plant parts. Genotype-independent seasonal decline of the
Cry1Ac toxin levels was observed in all the hybrids. Cry1Ac
expression decreased consistently as the plant aged. The decline
in Cry1Ac was more rapid in some hybrids compared to others. The
choice of parental background appeared to be crucial for
sustainable expression of the cry1Ac transgene. The implications
of variability in Cry1Ac expression and the seasonal decline on
bollworm management are discussed.
Full
paper in Current Science in PDF format:
http://www.ias.ac.in/currsci/jul252005/291.pdf
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