Bt Crops PDF

# Bt. Crops Suraj Kumar Padhi ## Content - Introduction about Bt. - Bt. COTTON - WORKING MECHANISM OF Bt. - ADVANTAGES AND DISADVANTAGES OF Bt. COTTON - Bt. BRINJAL AND ITS PRODUCTION TECHNIQUES - ADVANTAGES AND DISADVANTAGES OF Bt. BRINJAL - Bt. CORN AND ITS BENEFITS. ## Bacillus thuringiensis -...

# Bt. Crops Suraj Kumar Padhi ## Content - Introduction about Bt. - Bt. COTTON - WORKING MECHANISM OF Bt. - ADVANTAGES AND DISADVANTAGES OF Bt. COTTON - Bt. BRINJAL AND ITS PRODUCTION TECHNIQUES - ADVANTAGES AND DISADVANTAGES OF Bt. BRINJAL - Bt. CORN AND ITS BENEFITS. ## Bacillus thuringiensis - Shigetane Ishiwatari (1901), first isolated *Bacillus thuringiensis*. - Bt is commonly abbreviated as Bacillus thuringiensis, is a gram-positive, facultative aerobic, rod-like, motile and sporulating bacterium. - Bt is a naturally-occurring soil borne bacterium that is found worldwide - Ubiquitous in nature. - Produces crystals of endotoxin (Cry protein or delta toxin) - toxic to insect mainly in their larval stage, thus they act as insecticides. ## Bt, a Biological Insecticide - These crystal proteins (Cry proteins) are insect stomach poisons. - Insects stop feeding within two hours of a first bite and, if enough toxin is eaten, die within two or three days. - Important biological insect control agent. - Bt crystals, sometimes referred as insecticidal crystal proteins (ICP), are protein crystals formed during sporulation in some Bt strains coded by cry genes. ## What is Bt cotton? - Genetically modified variety of cotton that produces an insecticide. - Marketed by Monsanto, USA. ## How Bt Works? 1. Ingestion 2. Solubilization & proteolytic activation 3. Binding to target site 4. Formation of toxic lesions ## The Mechanism of Action of Bt - A diagram that shows Bacillus thuringiensis (Bt) toxin crystal being ingested by an insect, followed by solubilization and activation, binding to the insect's midgut cells, and ultimately causing cell death. ## Mode of Action of Bt Toxin in Insect Gut A diagram that illustrates the steps involved in the insecticidal action of Bt toxin. It shows: - Dissolving of crystals and activation of toxins - Toxins bind to receptors - Perforation of gut membrane ## 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 ## Methods of Gene Transfer - **Agrobacterium mediated gene transfer:** A diagram showing the transfer of DNA from a source organism to Agrobacterium, followed by tissue culture and micropropagation, culminating in the final plant. - **Bombardment of cells with particle coated with gene of interest:** A diagram illustrating the process, starting with the source organism, utilizing gold or tungsten microparticles for DNA transfer, and resulting in a final plant through micropropagation. ## 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. A depiction of the process showcasing the integration of a gene into the Ti plasmid and the co-cultivation of the modified bacterium with plant pieces. ## 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. - Cotton yield increased from 308kg/ha in 2001-02 to 550kg/ha in 2014-15. ## Advantages of Bt-cotton - Yield superiority - More profit - Lesser need of pesticide - Better quality - Suitability for early sowing ## Disadvantages - Higher cost of seeds - Higher fertilizer and irrigation cost ## List of transgenic cotton (Bt cotton) | 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 | ## 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 | ΜΟΝ-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 | ## Bt. BRINJAL - Brinjal is botanically known as *Solanum melongena* L. (2n =24) included under the genus *Solanum* which is one of the largest genera having more than 1,500 described plant species. - The cultivated types are fit for human consumption and are divided into three main varieties based on fruit shape. - *S. melongena var. esculentum* (Round or egg-shape) - *S. melongena var. serpentinum* (Long and slender) - *S. melongena var. depressum* (dwarf brinjal plants) ## Major Problems - Major problem in brinjal cultivation is brinjal shoot and fruit borer (*Leucinodes orbonalis*). - It is monophagous and attacks all aerial parts of plant especially shoot and fruit. - Damage the fruit and affect fruit quality badly. - It causes yield losses about 60-70% even after multiple insecticide spray. ## Life Cycle of The Fruit and Shoot Borer - A diagram showing the life cycle of the fruit and shoot borer, with stages: - Eggs - Larvae (25-43 days) - Pupae - Adult ## Symptoms of Damage - A comparison showing shoot damage and fruit damage caused by the borer. ## What is Bt Brinjal - Bt Brinjal is a transgenic brinjal created out of inserting a gene [cry IAc] from the soil bacterium Bacillus thuringiensis in to brinjal. - The insertion of the gene into the Brinjal cell in young cotyledons has been done through an Agrobacterium mediated vector, along with promoters, markers etc. - This is said to give the Brinjal plant resistance against lepidopteran insects like the Brinjal Fruit and Shoot Borer (*Leucinodes orbonalis*) and Fruit Borer (*Helicoverpa armigera*). - It is reported that upon ingestion of the Bt toxin by the insect, there would be disruption of digestive processes, ultimately resulting in the death of the insect. ## Transformation of Brinjal - A diagram visualizing the transfer of DNA from Agrobacterium to a plant cell, outlining the processes: 1. Bacterial and plant receptors interact. 2. Plant signals stimulate VirA and VirG. 3. The vir region activates VirD1/D2. 4. The virB/D4T4SS channel transfers the T-complex to the plant cell. 5. The VirF protein is transported into the plant cell. 6. The T-complex enters the plant cell. 7. The T-complex travels towards the nucleus. 8. The T-complex enters the nucleus. 9. The T-complex integrates into the plant's DNA. 10. The integrated T-DNA. ## Transformation of Brinjal (Contd.) - A series of diagrams showing the process - transforming brinjal with Agrobacterium, depicting: - (a) Intracellular transport – the T-complex moving towards the nucleus, with the VirF protein, the VirE2 protein, and microtubules. - (b) Nuclear import – the T-complex getting imported into the nucleus through a Nuclear Pore Complex (NPC), with karyopherins. - (c) Core histones – the T-complex reaching the core histones inside the nucleus. - (d) T-DNA uncoating – the T-DNA is unwrapped. - (e) T-DNA integration – the T-DNA gets integrated into the host’s DNA with the help of the KU80 protein. ## Schematic Diagram of Bt Crop Development - A diagram detailing the steps involved in developing a Bt crop, including: 1. Inoculation 2. Co-Cultivation 3. Selection & Regeneration 4. Re-growth 5. Molecular Verification of Gene Presence & Expression 6. Evaluation of Transformed Brinjal plant for Insect Protection ## Arguments in Favour of Bt Brinjal - 60% of plant protection cost for controlling fruit and shoot borer is reduced. - In spite of the extensive use of chemical pesticides, larvae lead a concealed life it is difficult to control through insecticide sprays. ## What are the Benefits of Bt Brinjal.? 1. Non-infested, undamaged and good quality brinjal fruits. 2. Bt brinjal will significantly reduced level of pesticide residues. 3. Saving on cost of insecticides and lower labor cost as a result of reduced spraying. 4. Increase in yield per unit area by saving fruits from damage caused by FSB. ## Benefits to Farmers A comparison showing the difference in appearance between brinjal plants that have not been treated with Bt and those that have. ## Bt. CORN - Why does corn need protection from corn borers? - Each year, 40 million tons of corn never reach the market due to damage. - If corn borers are not controlled, the larvae will eventually turn into moths and the cycle continues. - Bt corn produces a protein that gives Bt corn built-in resistance to the corn borer - offering protection throughout the plant where the insect attacks. ## How Does Bt. Corn Work? - Bt maize has built-in protection against corn borers, achieved through modern biotechnology, where the Cry1Ab gene has been added. - The Cry1Ab gene produces a Bt protein (Cry1Ab) which protects the plant from insect damage (*Bacillus thuringiensis*). - A comparison showing the tunneling of the borer and the stalk tunnel after infection by the borer, highlighting the damage caused by the borer. ## Mechanism of Action of Bt in Corn - A diagram depicting the process starting with *Bacillus thuringiensis*, the Bt gene being inserted into a crop, the European corn borer infecting a crop, and finally the pest dying when feeding on the crop. ## What are the benefits of Bt corn - It represents an environmentally sustainable way to control devastating insect pests and, therefore, to ensure yield. - Also, grain from Bt corn is often of better quality than grain from conventional corn hybrids, since insect damage reduces grain quality. - Studies show that there is a significant economic return from growing Bt corn, with yields protected in years when there is a heavy outbreak of corn borer. - There is also evidence that Bt corn provides a form of protection to non-Bt corn by reducing the overall population of corn borers. ## Bt Corn Control Study - Bt corn (MON810, BT11) provides 96% average control of European corn borer larvae. - Bt corn (event 176) provides 96% control of first generation corn borers and 75% control of second generation corn borers. - Insecticides provide 80% and 67% control of first and second generation borers, respectively. ## Impact of Bt Corn - Bt Cry proteins are highly selective in killing larvae of moths. - Does not affect beneficial insects including honey bees, lady beetles, green lacewing larvae, spiders, pirate bugs or parasitic wasps. - Indirect effects on natural enemies of European corn borer, however, could occur. - Predators, parasites and pathogens of the corn borer might decline as corn borer populations decline. ## Bt Corn Safety - Bt has no toxic impact in higher animals (HUMAN) because of...... - Acidic stomach - Very low pH (~1.5 in humans) - Absence of required receptors - Bt is safe to non-target organisms - HUMAN ## Reference - Hilbeck and Schmidt (2006). - Anonymous, 2009 - Choudhary & Gaur, 2009 - 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 - Aronson, A. (2002). Sporulation and δ-endotoxin synthesis by Bacillus thuringiensis. Cellular and Molecular Life Sciences CMLS, 59(3), 417-425. ## Thank You