GENET archive


2-Plants: American Bollworm resistance to Bt cotton can be delayed up to 40 years

                                  PART I
-------------------------------- GENET-news -------------------------------

SOURCE: Public Information Bureau, Government of India
DATE:   29 Jul 2005

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The Minister of State for Agriculture, Dr. Akhilesh Prasad Singh
informed, in reply to a question in Rajya Sabha today that, the study
conducted by Central Institute for Cotton Research (CICR) showed that the
American bollworm will develop resistance to Bt-cotton after a few years
depending mainly on the extent of area under Bt-cotton in the country.

With the current rate of increase in the area under Bt-cotton, it is
likely to take about 11-12 years for the pest to develop resistance to

However, with implementation of proper strategies as suggested by CICR,
it is possible to delay resistance by at least 30-40 year, if not more.

A stochastic model 'Bt-Adapt' was developed to simulate the rate of
resistance development of H. armigera to Cry1Ac under Indian farming
conditions. The model integrates genetic and ecological parameters of H.
armigera in relation to its response to the Cry1Ac expressing Bt cotton.
The model can predict the time that would take for bollworm to develop
resistance in different cotton-growing districts of the country based on
the input statistics of area under Bt-cotton in each of the districts, or
even the proposed area to be cultivated under Bt cotton.

Simulation analysis showed that relative survival rate of the Cry1 Ac
resistant homozygous (RR), heterozygous (RS) and homozygous susceptible
(SS) H. armigera genotypes on Bt cotton, was the most important factor
influencing resistance development. In the order of significance, the
other factors that had the greatest impact on resistance development
were, the relative proportion of area under Bt cotton, dominance of the
resistant allele and initial frequency of resistant alleles in field
populations. The extent of population reduction in Bt cotton and non-Bt
crops due to pest control, was found to have a significant impact on the
rate of resistance development.

The Indian Council of Agricultural Research (ICAR) has initiated a net-
working project in 2004, to carefully monitor resistance development in
all the 9 cotton growing states of the country and also to scientifically
analyze all factors that contribute to resistance development. The
national net-working group has been given the task of developing
resistance management strategies from time to time every year and
disseminate them to all the stakeholders, including the Genetic
Engineering Approval Committee (GEAC), the state agricultural
Universities, Government institutions, farmers, Non-Governmental
Organisation (NGO), etc. Based on the simulation analysis, using the 'Bt-
Adapt' model, and scientific data available so for, CICR has proposed
some important resistance management strategies to the GEAC.

The strategies place emphasis on reducing populations of H. armigera that
survive Bt cotton and enhancement of area of alternate host crops that
are as attractive as cotton to H. armigera, to be used as trap crop or
intercrop refuges. If proper pest management measures are followed to
ensure that at least 90 per cent of the surviving larvae of the American
bollworms in Bt-cotton fields, are killed with biopesticides, resistance
can be delayed to 45 years even with 40 per cent area under Bt cotton.

The strategies, that would enable extending the usefulness of Bt
technology would be:

(i) Use eco-friendly methods such as cultural control or hand-picking of
surviving bollworms in Bt cotton fields. Deep-ploughing of fields
immediately after Bt-cotton harvest to destroy resistant pupae.

(ii) Biopesticides that are neem based or HaNPV (virus) were found to be
more effective on larvae surviving on Bt-cotton because of their slower
growth as compared to those on the conventional non-Bt cotton. Hence
these would be useful to manage younger larvae on 60-90 days old crop.
Alternatively, eco-friendly insecticides such as spinosad, emamectin
benzoate, novaluron or Indoxacarb can be used on 90 and 120 days old crop
to reduce populations of resistant insect genotypes.

(iii) Use of attractive synchronous alternate host crops such as
marigold, sunflower, chillies etc. for H. armigera which could be used as
intercrop or trap crop refuges.

(iv) Use alternate genes that do not share common resistance mechanisms
as that of Cry1Ac, in transgenic plants either in rotation or alternation
or mixtures such as the dual-gene based Bt-cotton varieties.

                                  PART II
-------------------------------- GENET-news -------------------------------

TITLE:  Bt cotton ineffective against bollworm: research
SOURCE: The Financial Express, India, by Ashok B. Sharma
DATE:   1 Aug 2005

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Bt cotton ineffective against bollworm: research

Recent research findings on Bt cotton have placed the country's
regulatory authority, Genetic Engineering Approval Committee (GEAC) in
the dock. Based on a series of experiments, a team of scientists from
Nagpur-based Central Institute of Cotton Research (CICR), have proved
that the Bt cotton becomes ineffective in its resistance to bollworm
after 110 days.

GEAC is slated to meet on August 10 and take up the matter. The civil
society organisations, who have claimed that Bt cotton has failed to
produce the desired results, are now up in arms demanding a review of the

Bollworms cause extensive damage to the cotton crop. With a view to make
the cotton plant resistant to bollworms, transgenic technology was
applied by inserting the gene from a soil bacteria, Bacillus thurigiensis
(Bt). This inserted gene allows the plant to produce Cry1Ab protein which
is toxic to bollworms.

However, a team of scientists from CICR, led by Keshav R Kranthi, have
recently found that the resistant power in cotton plant remains only for
110 days, after which the crop can be exposed to bollworm attacks. The
Cry1Ac level declines as the plant grows and is found to drop below its
"lethal level" of 1.9 mg within 110 days after sowing.

"In our next meeting, we may discuss the findings of the paper published
in Current Science," said a senior GEAC member. The study further said
that toxin expression were lowest in the ovary of flowers and rinds of
green bolls which are the most favoured sites of bollworm attack.

The study was published in the July 25 edition of Current Science.
Current Science also published in May 25, 2003, a similar study conducted
by a team of scientists in the University of Agricultural Sciences, Dharwad.

"The decline in resistant power means that the farmer has to apply more
chemical pesticides to save his crop. Already, the cost of Bt cotton
seeds are high and added to this, he incurs additional costs on
pesticides. Eventually, he lands up in heavy debts," a researcher said.

Those farmers, who hope that Bt cotton can be a miracle and, therefore,
do not apply heavy doses of chemical pesticides, are at a loss," said the
director of Secunderabad-based Centre for Sustainable Agriculture (CSA),
Dr GV Ramanjaneyulu. "The very fact that scientists do not have control
over toxin expression in plants shows that transgenic technology is
imprecise and unpredictable," he said.

He said that CSA conducted studies on each of the three years of
commercial cultivation of Bt cotton in India. All the results proved that
Bt cotton growers incurred losses. In contrast, the farmers growing non-
Bt cotton, following the procedures of organic farming and applying bio-
pesticides, reaped good profits, he said. u

In the past three years of commercial cultivation of Bt cotton, several
other NGOs like Gene Campaign, Research Foundation for Science,
Technology and Ecology, and Deccan Development Society, conducted studies
and came out with similar results. These NGOs and farmers' organisations
like Bharat Krishak Samaj had cautioned GEAC to withdraw approval to Bt

However, GEAC, this year, approved 13 new varieties of Bt cotton for
different regions of the country. At the same time, it banned cultivation
of Mech-12 Bt in the entire south Indian region and Mech-162 Bt and Mech-
184 Bt in Andhra Pradesh on receiving adverse reports from the concerned
state government.


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