Bt cotton is a genetically modified cotton variety that produces an insecticidal crystal protein called Cry protein derived from the soil bacterium Bacillus thuringiensis. The Cry protein is toxic only to certain insect pests like cotton bollworm and pink bollworm when they ingest it, causing them to stop feeding within a few days. Bt cotton was first commercialized in India in 2002 and its adoption has significantly increased cotton yields while decreasing insecticide use and costs for Indian farmers. However, Bt cotton also requires higher investment in seeds and irrigation. Ongoing research is developing new Bt cotton hybrids with additional traits like drought tolerance and disease resistance.

1. Technology of Bt cotton
Ditipriya Hazra
13BT60R18

2. What is Bt cotton ?
•Genetically modified variety of cotton that
produces an insecticide.
•Marketed by Monsanto, USA.

3. What is Bt ?
•Bacillus thuringiensis discovered by
Ishiwatari in 1901.
•Bacterium produces insecticidal crystal
protein (ICP) also known as Cry protein
•They are a class of endotoxin – δ endotoxins.

4. Structure of Cry protein
Domain I •7 α-helix
•Helps in membrane insertion
Domain II • β-prism of 3 antiparallel β-
sheets
•Helps in receptor recognition
Domain
III
• β-sandwich of antiparallel β -
sheeets
Crystal structure of Cry protein

5. Timeline
1901 Shigetane Ishiwatari first isolated the bacterium Bacillus thuringiensis as
the cause of the sotto disease
1915 Berliner reported the existance of a crystal within Bt, but the activity of
this crystal was not discovered until much later
1956 Researchers Hannay, Fitz-James and Angus found that the main
insecticidal activity against lepidoteran (moth) insects was due to the
parasporal crystal
1958 In the US, Bt was used commercially
1961 Bt was registerd as a pesticide to the EPA
1996 Bt cotton was introduced into US agriculture

6. Trade name Bt protein crop Company Insect pests
Bollgard Cry1Ac Cotton Monsanto Tobacco
budworm, cotton
bollworm, pink
bollworm
Bollgard II Cry1Ac+Cry2Ab Cotton Monsanto Tobacco
budworm, cotton
bollworm, pink
bollworm
Widestrike Cry1Ac+Cry1Fa cotton Dow Tobacco
budworm, cotton
bollworm, pink
bollworm
List of transgenic cotton (Bt cotton)

7. Objective
•To understand the general mode of action of
Cry toxin
•To understand the technology behind Bt
cotton production.
•To comprehend the current scenario of Bt
cotton in India.

8. How Bt works ?
1. Ingestion
2. Solublization & proteolytic activation
3. Binding to target site
4. Formation of toxic lesions

9. Mode of action of Cry toxin

10. Technology of production
Main steps for developing transgenic crops :
1. Identification of effective gene(s).
2. Gene transfer
3. Regeneration from protoplast/callus/tissue
4. Gene expression to the desired level
5. Back cross to produce varieties
6. Field test
7. Approval for commercialization

11. Methods of gene transfer
•Agrobacterium
mediated gene
transfer
•Bombardment of
cells with particle
coated with gene of
interest
Two routes of gene transfer

12. Transformation with Agrobacterium
Agrobacterium
contains a circle of
DNA (Ti plasmid)
that carries the
desired genes
Co-cultivation of the
Agrobacterium with
plant pieces
transfers the DNA
Bacterial
chromosomeTi Plasmid
Petri dish with leaf pieces & Agrobacterium

13. Agrobacterium mediated gene transfer

14. 14
‘Particle Gun’
DNA coated on pellets is
forced down the barrel
of a ‘Particle Gun’ by an
explosive charge
The particles are forced
through the cell wall
where the DNA is
released
Barrel
Explosive
Charge
Vent
Stop plate
Petri Dish
with cultures
Projectile
DNA coated
pellets

15. Production of Bollgard®
•Agrobacterium mediated transfer
• CaMV35S promoter
•Somatic embryogenesis.

16. Advantages of Bt-cotton
•Yield superiority
•More profit
•Lesser need of pesticide
•Better quality
•Suitability for early sowing

17. Disadvantages
•Higher cost of seeds
•Higher fertilizer and irrigation cost
•Higher harvest cost

18. 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.

19. •For 11th year Bt cotton was planted in India in
10.8 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.

20. Commercial release of different Bt cotton events in India, 2002 to 2009
No. Event Developer Status Date of approval
1 MON-531 Mahyco/Monsanto commercialized 2002
2 MON-15985 Mahyco/Monsanto commercialized 2006
3 Event-1 JK Agri-Genetics commercialized 2006
4 GFM Event Nath Seeds commercialized 2006
5 BNLA-601 CICR (ICAR) & UAS,
Dharwad
commercialized 2008
6 MLS-9124 Metahelix Life Sciences commercialized 2009

21. Future prospects of Bt cotton in
India
•5 new hybrid cottons are under biosafety
assessment which will be considered for
commercial approval between 2013-15.
•. Other traits include drought and salinity
tolerance, disease resistance, sucking insect
resistance, leaf curl virus resistance and other
traits related to cotton fiber quality.

22. Reference
• Aronson, A. (2002). Sporulation and δ-endotoxin synthesis by Bacillus thuringiensis. Cellular and Molecular Life
Sciences CMLS, 59(3), 417-425.
• Bravo A., Gill S. S., & Soberon M. (2007). Mode of action of Bacillus thuringiensis Cry and Cyt toxins and their
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 control.
In Microbial Control of Pests and Plant Diseases 1970-80 (Burgess, H.D., ed.). New York, NY: Academic Press, pp.
193-222.
• English, L. and Slatin, S.L. (1992) Mode of action of deltaendotoxin from Bacillus thuringiensis: a comparison with
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. (1990)
Insect resistant cotton plants. Bio/Technol. 8, 939-943