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Source:- K. R. Kranthi, Ph.D, FNAAS, Director, Central Institute for Cotton Research, Nagpur
Dr. Pavan J Kundur
P C Jabin Science College
Hubballi, Karnataka, India
What is Bt-cotton?
Bt cotton is genetically modified cotton crop that expresses an
insecticidal protein whose gene has been derived from a soil bacterium
called Bacillus thuringiensis, commonly referred as Bt.
Many subspecies of B.thuringiensis are found in soils and are in general
known to be toxic to various genera of insects but safe to other living
Bt was first discovered by a Japanese scientist Ishiwata in the year 1901.
Bt has been used as an insecticide for control of stored grain pests since
1938 in France and from 1961 as a registered pesticide in the USA
later in many other countries including India as sprays in cotton IPM
programs to control insects.
Marketed by Monsanto, USA
Bt toxins thus have several decades of proven selective toxicity to insect
pests and with established safety record to non-target animals.
Currently there are 67 recognized subspecies of B. thuringiensis most of
which produce spores and insecticidal proteins.
The Bt gene cry1Ac was used to develop the first Bt-cotton variety.
The gene was transferred into the genome of cotton explants (tissue
pieces) using a bacterium called Agrobacterium tumefasciens.
The transformed cells were developed into a full GM plant now called Bt-
In general, Cry1Ac toxins are highly specific to insects at species level, and
are not known to cause any harm to non-target species such as fish, birds,
farm animals and human beings.
Currently, Cry1Ac, Cry2Ab and Cry1C have been approved for
commercial cultivation in India.
Bt cotton hybrids available in India are derived from technologies
developed by Monsanto
Dow Agro sciences are conducting field trials with Cry1Ac +
Cry1F and Bayer is introducing Cry1Ab + Cry2Ae.
There were 1128 Bt-cotton hybrids in 2012, developed by 40 seed
companies, available in the Indian markets.
Why do we need Bt-cotton?
a) Cotton is a long duration crop and is attacked by large number of insect
pests throughout its growth and development.
b) The three bollworms, American bollworm Helicoverpa armigera, Pink
bollworm Pectinophora gossypiella and the Spotted bollworms, Earias vittella
and Earias insulana are major pests and cause serious threat to cotton
production resulting in significant yield losses.
c) About 9400 M tonnes of insecticides worth Rs 747 crores were used only for
bollworm control 2011
d) insecticide quantity applied on cotton was the highest
e) Bollworms are hidden feeders and generally do not come into
direct contact with insecticide sprays.
f) 50.0% of all insecticides in India were being unsuccessfully used for
cotton pest control, until the year 2001, before Bt cotton was
G) Resistant sources are unavailable in the germplasm and resistance
has been unsuccessful.
How does Bt-cotton kill insects?
2. Solublization & proteolytic activation
3. Binding to target site
4. Formation of toxic lesions
Structure of Cry protein
Source :- Wikipedia
•Helps in membrane insertion
•β-prism of 3 antiparallel β-sheets
•Helps in receptor recognition
• β-sandwich of antiparallel β -
Dr. Juan Luis Jurat-Fuentes
Department of Entomology and Plant
The University of Tennessee
2431 Joe Johnson Drive
205 Ellington Plant Sciences Building
Knoxville, TN, 37996
Tel: (865) 974-5931
ingestion of the Cry protein by a susceptible insect, solubilization, and
procesing from a protoxin to an activated toxin core in the insect
The toxin core travels across the peritrophic matrix and binds to specific
receptors called cadherins on the brush border membrane of the gut
Toxin binding to cadherin proteins results in activation of an oncotic cell
death pathway and/or formation of toxin oligomers that bind to GPI-
anchored proteins and concentrate on regions of the cell membrane
called lipid rafts. * Glycosyl phosphate dylinositol
Accumulation of toxin oligomers results in toxin insertion in the
membrane, pore formation, osmotic cell shock, and ultimately insect
Advantages of Bt-cotton
• Yield superiority
• More profit
• Lesser need of pesticide
• Better quality
• Suitability for early sowing
• Higher cost of seeds
• Higher fertilizer and irrigation cost
• Higher harvest cost
Bt cotton in India
• India is the largest cotton producer and consumer country after China.
• In 2002 Bt cotton was introduced in India.
• India has the largest hectarage of cotton and accounts for
approximately one third of the total cotton are planted in the world.
• For 11th year Bt cotton was planted in India in10.8 mil hectares .
• Decline in insecticide use was from US$160 million in 2004 to US$25 million
in 2010 –an 85% decrease
• Cotton yield increased from 308kg/ha in 2001-02 to 500kg/ha in 2011-12.
How many Bt-hybrids are available in India?
The Bt-cotton technology was first approved in 2002 by the GEAC for
commercial cultivation in central and south Indian cotton–growing zones in
India in the form of three hybrids
(MECH-12, MECH-162, and MECH-184)
By the end of July 2008, the total number of Bt-hybrids increased to 283.
By August 2009 the number increased to 564 Bt-hybrids and one Bt-variety.
By August 2010 the total number of Bt-hybrids increased to 809
By May 2012 there were 1128 Bt cotton hybrids available in the market.
Govt keeps Bt cotton price unchanged at Rs 730 per packet for 2020-21;
scraps royalty fee to Bayer
Bayer, which in June 2018 completed the USD 63-billion deal to acquire
Monsanto, has expressed disappointment over doing away with trait value or
royalty altogether. According to a government notification, the maximum sale
price for Bollgard-II (BG-II) cotton seed for 2020-21 has been fixed at Rs 730
per packet of 450 gm. The seed value is Rs 730 and trait value zero.
Read more at:
• Aronson, A. (2002). Sporulation and δ-endotoxin synthesis by Bacillus thuringiensis. Cellular and
Sciences CMLS, 59(3), 417-425.
• Bravo A., Gill S. S., & Soberon M. (2007). Mode of action of Bacillus thuringiensis Cry and Cyt toxins
potential for insect control. Toxicon, 49(4), 423-435.
• Dulmage, H.T. (1981) Insecticidal activity of isolates of Bacillus thuringiensis and their potential for pest
Microbial Control of Pests and Plant Diseases 1970-80 (Burgess, H.D., ed.). New York, NY: Academic
• English, L. and Slatin, S.L. (1992) Mode of action of deltaendotoxin from Bacillus thuringiensis: a
other bacterial toxins. Insect Biochem. Molec. Biol. 22, 1-7.
• Perlak, F.J., Deaton, R.W., Armstrong, T.A., Fuchs, R.L., Sims, S.R., Greenplate, J.T. and Fischhoff, D.A.
Insect resistant cotton plants. Bio/Technol. 8, 939-943