Bt Cotton

Bt cotton is a genetically modified (GM) variety of cotton that contains a gene from the bacterium Bacillus thuringiensis (Bt), which enables the plant to produce an insecticidal protein toxic to specific pests, particularly the cotton bollworm complex. It represents one of the most significant advances in agricultural biotechnology and has transformed cotton cultivation across many countries, including India. The introduction of Bt cotton aimed to reduce pesticide use, improve crop yields, and enhance farmers’ income.

Origin and Development

The bacterium Bacillus thuringiensis, first identified in 1901, produces crystalline (Cry) proteins during sporulation. These Cry proteins act as natural insecticides against certain lepidopteran (caterpillar) pests. Scientists isolated and inserted the Bt gene (notably Cry1Ac and Cry2Ab) into cotton plants using genetic engineering techniques in the 1980s.
The first commercial Bt cotton variety, Bollgard I, was developed by the company Monsanto and introduced in the United States in 1996. It was later followed by Bollgard II, which contained stacked genes for broader pest resistance. India approved the commercial cultivation of Bt cotton in 2002, marking a major milestone in its agricultural biotechnology sector.

Genetic Mechanism and Mode of Action

Bt cotton contains a transgene derived from the bacterium Bacillus thuringiensis. The most common genes inserted include Cry1Ac and Cry2Ab, which encode insecticidal proteins.
Mechanism of action:

1. When larvae of target pests such as the cotton bollworm (Helicoverpa armigera) feed on Bt cotton, they ingest the Cry protein.
2. The protein becomes activated in the insect’s alkaline gut environment.
3. The activated toxin binds to specific receptors on the gut epithelial cells, creating pores in the cell membrane.
4. This disrupts the gut lining, causing leakage of internal fluids and resulting in paralysis and death of the pest within a few days.

Importantly, the Bt toxin is highly specific, affecting only certain groups of insects and not humans, animals, or beneficial pollinators.

Varieties and Gene Events in India

India’s adoption of Bt cotton began with Bollgard I (Cry1Ac), followed by Bollgard II (Cry1Ac + Cry2Ab), providing resistance to a broader spectrum of bollworms.
Bt cotton hybrids were developed both by multinational companies (such as Monsanto–Mahyco) and Indian research institutions under licences. Presently, hundreds of approved Bt cotton hybrids are cultivated across various agro-climatic zones.
Key institutions involved in Indian Bt cotton development include:

• Maharashtra Hybrid Seeds Company (Mahyco)
• Central Institute for Cotton Research (CICR), Nagpur
• Indian Council of Agricultural Research (ICAR)

Target Pests and Benefits

Bt cotton primarily targets the bollworm complex, one of the most destructive pest groups affecting cotton crops:

• Helicoverpa armigera (American bollworm)
• Pectinophora gossypiella (Pink bollworm)
• Earias vittella (Spotted bollworm)

Major Benefits:

1. Reduction in Chemical Pesticide Use: Farmers applying Bt cotton have reported a reduction of up to 40–60% in pesticide use against bollworms.
2. Higher Yields: Protection from pest damage leads to increased productivity—often 25–35% higher than conventional varieties.
3. Economic Gains: Lower input costs and higher yields have increased net farm income, benefiting millions of smallholders.
4. Environmental and Health Benefits: Decreased pesticide spraying reduces soil and water contamination and exposure risks to farmers.
5. Compatibility with IPM: Bt cotton complements Integrated Pest Management (IPM) systems by allowing targeted pest control.

Adoption in India

India has become one of the largest cultivators of Bt cotton globally. By the early 2020s, Bt cotton covered over 90% of India’s total cotton-growing area, transforming the country from a net importer to a leading global exporter of cotton. Major Bt cotton-growing states include Maharashtra, Gujarat, Andhra Pradesh, Telangana, Punjab, Haryana, and Madhya Pradesh.

Limitations and Challenges

Despite its initial success, several ecological, economic, and social concerns have emerged:

1. Pest Resistance:
   • Continuous exposure of pests to the Bt toxin has led to the evolution of resistant populations, particularly of pink bollworm (Pectinophora gossypiella) in parts of India.
   • Resistance management strategies, such as planting refuge crops (non-Bt cotton around Bt fields), are often poorly implemented.
2. Secondary Pest Outbreaks:
   • Reduction of bollworms has led to a surge in non-target pests such as whiteflies, aphids, and mealybugs, necessitating pesticide use once again.
3. High Input Costs:
   • Bt cotton seeds are costlier than conventional seeds, increasing dependency on seed companies and reducing traditional seed-saving practices.
4. Socioeconomic Disparities:
   • Small and marginal farmers with limited irrigation face financial risks due to fluctuating yields and input costs.
   • In rainfed areas, crop failure due to drought or pest resurgence has occasionally resulted in economic distress.
5. Environmental and Biodiversity Concerns:
   • Monoculture cultivation reduces agro-biodiversity.
   • There are concerns about gene flow to wild relatives and effects on soil microbial communities.

Resistance Management Strategies

To ensure the long-term efficacy of Bt cotton, several management strategies have been recommended:

• Refugia Approach: Farmers must plant at least 20% non-Bt cotton near Bt fields to provide susceptible insects and delay resistance buildup.
• Gene Stacking: Use of multiple Bt genes (Cry1Ac + Cry2Ab) reduces the likelihood of pests developing resistance to both toxins simultaneously.
• Crop Rotation: Alternating cotton with non-host crops interrupts pest life cycles.
• Integrated Pest Management (IPM): Combining Bt technology with biological control, trap crops, and judicious pesticide use enhances sustainability.

Regulatory Framework in India

Bt cotton is the only genetically modified crop approved for commercial cultivation in India under the Environment Protection Act, 1986. Its release and monitoring are overseen by the Genetic Engineering Appraisal Committee (GEAC) under the Ministry of Environment, Forest and Climate Change (MoEFCC).
Biosafety assessments ensure that Bt cotton is non-toxic to humans, animals, and beneficial insects, and does not adversely affect the environment when properly managed.

Environmental and Health Safety

Extensive studies worldwide, including those by the World Health Organization (WHO), Food and Agriculture Organization (FAO), and Indian Council of Medical Research (ICMR), have found no evidence of toxicity or allergenicity of Bt proteins to humans or livestock. However, long-term ecological monitoring is recommended to assess indirect impacts on soil fauna and non-target organisms.

Socio-Economic Impact in India

Since its introduction, Bt cotton has had transformative effects on Indian agriculture:

• Cotton production increased from around 13 million bales in 2002 to over 35 million bales by 2014–15.
• India became the second-largest cotton producer in the world.
• Farmer income rose due to reduced pest losses and higher yields.
• Employment in cotton processing and textile sectors expanded.

However, benefits have been uneven, and sustainability depends on continuous innovation, extension education, and resistance management.