Bt cotton is an insect-resistant transgenic crop designed to combat the bollworm. Bt cotton was created by genetically altering the cotton genome to express a microbial protein from the bacterium Bacillus thuringiensis. In short, the transgene inserted into the plant’s genome produces toxin crystals that the plant would not normally produce which, when ingested by a certain population of organisms, dissolves the gut lining, leading to the organism’s death.
Mechanisms of Action
Bt is a family of proteins originating from strains of the bacterium Bacillus thuringiensis. There are more than 200 different types of Bt toxins, each affecting different types of insects. The Bt cotton plants are genetically modified by the addition of genes encoding toxin crystals in the Cry group of endotoxin. When ingested by insects, the Cry toxins are dissolved and activated by the high pH environment of the animal’s gastrointestinal system. In the midgut, the activated Cry molecules bind to cadherin-like proteins on cells comprising the brush border membrane.
The epithelium of the brush border membrane has the function of maintaining separation of the body cavity from the gut while allowing absorption of nutrients from the digested food bolus. Cry toxins bind to specific locations on the cadherin-like proteins present on the epithelial cells of the midgut, and form ion channels allowing potassium ions to flow from the cells. As the control of potassium ion concentration is critical to the survival of every living cell, they are tightly regulated under normal function. With the formation of Cry ion channels and the subsequent efflux of potassium ions, the affected epithelial cells lyse and die. This creates gaps in the brush border membrane, allowing bacteria and Bt spores to enter the body cavity. Subsequently, the insect will die of internal infection after ingesting a Bt crop.
History of Bt Cotton
Cotton is a crop of very high economic value because of its widespread demand in the textile industry, representing 38% of the fiber market. The uses of the cotton fiber and its seeds are widespread, ranging from clothing, upholstery, cosmetics, packaging to cottonseed-oil, paper, electrical equipment, and livestock feed. As of 2008-2009 reports, the largest producer of cotton is China, followed by USA and India. For such an important cash crop, the loss of hundreds of acres worth of harvest due to attack by pests proves to be a big loss to farmers as well as the industry. It also leads to waste of precious resources like soil, water and labor.
1901 – Japanese biologist, Shigetane Ishiwatari first isolated the bacterium Bacillus thuringiensis (Bt) as the cause of the sotto (sudden-collapse) disease
1911 – Ernst Berliner isolated a bacteria that had killed a Mediterranean flour moth and rediscovered Bt. He named it Bacillus thuringiensis, after the German town Thuringia where the moth was found.
1915 – Berliner reported the existance of a crystal within Bt, but the activity of this crystal was not discovered until much later. Farmers started to use Bt as a pesticide in 1920
1956 – Researchers Hannay, Fitz-James and Angus found that the main insecticidal activity against lepidoteran (moth) insects was due to the parasporal crystal. With this discovery came increased interest in the crystal structure, biochemistry, and general mode of action of Bt. Research on Bt began in ernest.
Starting in 1958 – In the US, Bt was used commercially.
By 1961 – Bt was registerd as a pesticide to the EPA.
1980’s – Use of Bt increased when insects became increasingly resistant to the synthetic insecticides and scientists and environmentalists became aware that the chemicals were harming the environment. Bt is organic and it affects specific insects and does not persist in the environment. Because of this, governments and private industries started to fund research on Bt.
1995 – With the advancement in molecular biology, it soon became feasible to move the gene that encodes the toxic crystals into a plant. The first genetically engineered plant, corn, was registered with the EPA .
1996 – Bt cotton was introduced into US agriculture
Debate over Bt Cotton in India
Even though India’s total cotton production ranks 3rd internationally behind China and the U.S., the acreage under cotton cultivation in India is about 25% of all agricultural land, the highest of any country. One main reason is that the production of cotton per hectare is very low, and India ranks 70th in the world in the kg/hectare production of cotton. The reduced productivity of Indian cotton is often attributed to intense and diverse pest pressure and the lack of irrigation infrastructure. The hope was that the introduction of Bt Cotton would largely take care of the main pest problems and reduce the use of pesticides.
The use of BT cotton in India has raised a lot of controversy even before its official introduction in India. It all began when Monsanto partnered up with an Indian seed company MAHYCO in 1993 in a bid to introduce Bt cotton seeds in India. After a slow start with the Government of India’s Department of Biotechnology, a 50-50 joint venture called MAHYCO-Monsanto Biotech (MMB) was formed in 1998. They managed to acquire permission for field testing of Bt cotton seeds countrywide, and in 2001, they finally approached the GEAC (Genetic Engineering Advisory Committee) for the commercial release of Bt cotton varieties. GEAC withheld large scale cultivation and MMB was told to do more field trials for another year. In a press statement, the GEAC said, “MAHYCO may like to conduct field trials on farmer’s field in an area of about 100 hectares under close supervision of GEAC and Monitoring and Evaluation committee.” It also advised collection of the complete evidences and data pertaining to impact of transgenics on human and animal food, spread of the cry protein resistant boll worm and impact on non-target soil microflora and other fauna. However, in 2001, Gujarat faced a bad bollworm attack which devastated many acres of cotton fields. But some fields, remarkably, were mostly immune. This made MMB suspicious and they realized that the Cry1ac gene they had patented had spread out into the hands of the local seed company, Navbharat. The owner of Navbharat, D.B. Desai was taken to court by the infuriated MMB and questioned about this. D.B. Desai was later arrested and Navbharat was forbidden from selling these seeds, but the effectiveness of the Bt technology resulting in higher yields and reduced use of pesticides has nonetheless been proved.
Bt cotton has great promise as it is resistant to one of the major pests that decreases crop yield. However, the seed does come at comes at a much higher price. Seeds are purchased with loans from local money-lenders that charge very high interest rates, so farmers incur big debts to obtain the seed. Also, the seeds are resistant to the American bollworm but are not completely resistant to all pests, a fact that is not known by all farmers. If they do not have additional pest control strategies, even a Bt crop may be lost to pests. The situation is greatly worsened by counterfeit seed on the market that does not contain the Bt gene, so is susceptible to the bollworm and has no yield benefit. Even worse, if farmers do not know to spray pesticide on their counterfeit Bt fields, they may lose the entire crop to pests.
While Bt seeds have been successfully used by some farmers in India, others have been caught into vicious debt traps and low yielding harvests, as described above. This led to some poor marginal farmers committing suicide over the losses they have incurred. The farmer suicides happened in large numbers around 2004-2006 in the areas that cultivated cotton and a lot of these farmers drank the pesticides they sprayed on their crops out of despair.
Because of all the complicating socio-economic factors in a developing country like India, including trade laws, seed prices, counterfeit seeds, and high interest, as well as the high pest pressures that already exist, it is difficult to determine the role that the introduction of Bt cotton played. There are no reliable data sets available of the number of farmers that have committed suicide that were or were not using Bt seed. The low acceptance level of GM technology by the public makes it more difficult to tease out the many factors, since Bt has already been publically blamed as the cause. More thorough and unbiased ground-level research will have to be done to get a clear picture of whether Bt technology has really caused all the adverse effects on the lives of farmers or if surrounding social, political, and economic factors are responsible.
Bacillus Thuringiensis Brinjal, popularly known as Bt brinjal, is at the centre of a major controversy in India. Bt brinjal, a genetically modified strain created by India’s number one seeds company Mahyco in collaboration with American multinational Monsanto, claims to improve yields and help the agriculture sector.
FSB-resistant brinjal or Bt brinjal was developed using a transformation process similar to the one used in the development of Bt cotton, a biotech crop that was planted on 7.6 million hectares in India in 2008. Bt brinjal incorporates the cry1Ac gene expressing insecticidal protein to confer resistance against FSB. The cry1Ac gene is sourced from the soil bacterium Bacillus thuringiensis (Bt). When ingested by the FSB larvae, the Bt protein is activated in the insect’s alkaline gut and binds to the gut wall, which breaks down, allowing the Bt spores to invade the insect’s body cavity. The FSB larvae die a few days later.
Bt Brinjal was developed by the Maharashtra Hybrid Seeds Company (Mahyco). The company used a DNA construct containing the cry1Ac gene, a CaMV 35S promoter and the selectable marker genes nptII and aad, to transform young cotyledons of brinjal plants. A single copy elite event, named EE-1, was selected and introduced into hybrid brinjal in Mahyco’s breeding program. Mahyco also generously donated the Bt brinjal technology to the Tamil Nadu Agricultural University (TNAU), Coimbatore and University of Agricultural Sciences (UAS), Dharwad. The event EE-1 was backcrossed into open-pollinated brinjal varieties. Mahyco also donated the technology to public research institutions in the Philippines and Bangladesh.
Several other research institutions, both public and private have also been developing Bt brinjal using different genes. The National Center on Plant Biotechnology (NRCPB) has developed Bt brinjal varieties expressing the cryFa1 gene. The technology was subsequently transferred to companies including Bejo Sheetal, Vibha Seeds, Nath Seeds and Krishidhan Seeds. The Indian Institute of Horticultural Research (IIHR) is also developing Bt brinjal using the cry1Ab gene. Scientists are also looking for ways to develop Bt brinjal in conjunction with other multiple and beneficial traits.
Regulatory mechanism for bt brinjal in india
Bt brinjal is the first food crop under evaluation for commercial release in India. Since its development in 2000, the crop has undergone rigorous scientific evaluation to assess its food safety, environmental safety, human and animal health safety and biodiversity.
Rigorous scientific tests, including toxicity and allergenicity evaluation as well as nutritional studies on rabbits, rats, carps, goats, broiler chickens and dairy cows, have confirmed that Bt brinjal is as safe as its non-Bt counterparts. The safety of Bt brinjal was further validated by the results of the studies on pollen escape, effects on soil microflora and non-target organisms, agronomy, invasiveness and Bt protein degradation. Results of the studies demonstrated that Bt brinjal does not affect beneficial insects such as aphids, leafhoppers, spiders and lady beetles.
Bt brinjal was found to be effective against FSB, with 98% insect mortality in Bt brinjal shoots and 100% in fruits compared to less than 30% mortality in non-Bt counterparts. The Multilocation Research Trials (MLRTs) confirmed that Bt brinjal required, on average, 77% less insecticides than non-Bt counterparts for control of FSB, and 42% less for the control of all insect pests of brinjal. The benefits of Bt brinjal, translate to an average increase of 116% in marketable fruits over conventional hybrids, and 166% increase over popular open-pollinated varieties (OPVs). Furthermore, the significant decrease in insecticide usage reduced the farmers’ exposure to insecticides and results in a substantial decline in pesticide residues in brinjal fruits. Scientists have estimated that Bt brinjal will deliver farmers a net economic benefit ranging from Rs.16, 299 (US$330) to Rs.19,744 (US$397) per acre with national benefits to India exceeding $400 million per year.