Bt Cotton: Genetically Modified Organisms and Insect Control, Study notes of Plant Biotechnology

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Bt cotton

Presented by : Dr. Ujjwal

Layek

Assistant Professor

Department of

Botany

Rampurhat College

What are Genetically modified Organisms (GMO)? A genetically modified organism contains DNA that has been altered using genetic engineering. Genetically modified animals are mainly used for research purposes, while genetically modified plants are common in today’s food supply.

Advantages of Bt Crops

• (^) It helps in improving the crop yield, thereby, raising the farmer’s income. This results in increased farm production.
• (^) They help in controlling soil pollution as the use of synthetic pesticides is reduced.
• Bt crops help in protecting beneficial insects.
• (^) It can easily feed an increasing population due to increased yields in a short time.
• (^) It leads to the production of disease-free crops owing to the reduction of pesticides.
• It leads to more productivity in a small area of land. Disadvantages of Bt Crops
• (^) Bt crops are costlier than naturally grown crops.
• (^) It can disrupt the natural process of gene flow.
• The pests might become resistant to the toxins produced by these crops and the crop production might decline.

What is Bt Cotton? Bt cotton has been genetically modified by the insertion of one or more genes from a common soil bacterium, Bacillus thuringiensis. These genes encode for the production of insecticidal proteins, and thus, genetically transformed plants produce one or more toxins as they grow. The genes that have been inserted into cotton produce toxins that are limited in activity almost exclusively to caterpillar pests (Lepidoptera). However, other strains of Bacillus thuringiensis have genes that encode for toxins with insecticidal activity on some beetles (Coleoptera) and flies (Diptera). Some of these genes are being used to control pests in other crops, such as corn. History of Bt cotton After the invention of Bt cotton, it was approved by the United States in 1993 for filed trials. In 1995, it was approved for commercial use in the United States. In 1996 , Bollgard cotton (a Trademark of Monsanto) was the first Bt cotton to be marketed in the United States. In India, it was introduced in 2002 , with a joint venture between Monsanto and Mahyco seed hybrid company. Bollgard II was introduced in 2003 , representing the next generation of Bt cottons. Bollgard II contains a second gene from the Bt bacteria which encodes the production of Cry 2Ab. WideStrike (a Trademark of Dow AgroSciences) was registered for use in the fall of 2004. Like Bollgard II, WideStrike cotton expresses two Bt toxins (Cry1Ac and Cry1F). Both Bollgard II and WideStrike have better activity on a wider range of caterpillar pests than the original Bollgard technology.

Bt has to be eaten to cause mortality. The Bt toxin dissolve in the high pH insect gut and become active. The toxins then attack the gut cells of the insect, punching holes in the lining. The Bt spores spills out of the gut and germinate in the insect causing death within a couple days. Even though the toxin does not kill the insect immediately, treated plant parts will not be damaged because the insect stops feeding within hours.

• (^) 1. Insect eats Bt crystals and spores.
• (^) 2. The toxin binds to specific receptors in the gut and the insects stops eating.
• (^) 3. The crystals cause the gut wall to break down, allowing spores and normal gut bacteria to enter the body.
• (^) 4. The insect dies as spores and gut bacteria proliferate in the body. How does Bt work?

Is Bt cotton safe? Bt toxins are highly specific. The toxins produced by Bt cotton and corn are toxic to a select number of arthropod species. Because cotton is primarily a fiber crop, the contamination of food with toxins from cotton is highly unlikely. However, extensive testing indicates a very low public health risk from the use, including ingestion, of food products from Bt crops. Negative impacts on non-target arthropods are potential concerns resulting from the use of Bt crops. Concerns were raised because corn pollen, containing Bt toxins, could be blown onto plants which serve as hosts to monarchs, swallowtails, and other butterflies. This is a minor issue with cotton because, unlike corn, it is not wind pollinated. It should also be considered that Bt crops often reduce the use of broad spectrum insecticides, thereby reducing the impacts of these applications on the environment and non-target organisms.

a) Higher cost Compared to standard cotton production costs, Bt cotton production is costlier. The seed can cost between 700 to 2000 rupees, i.e., three to eight times more than the cost of a conventional source. b) Disrupt the natural process of gene flow. As bt cotton is a genetically modified crop that contains one or more foreign genes derived from soil-dwelling bacterium (bacillus thuringiensis), it can't be produced naturally and disrupt the process of gene flow. c) Not adequate for all insects Bt cotton is toxic to pollinating insects and ineffective against pests such as plants, bugs, stink bugs, whitefly, and aphids. Disadvantages of Bt cotton

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