How Do Bt Crops Work? Mechanism & Impact in Modern Farming
For centuries, many developing as well as developed countries faced a major food scarcity because of shrinking agricultural land and low levels of harvests. In the late 20th century, this problem was addressed with Genetically Modified or GM crops.
Using transgenics, these GM crops gave rise to a new age of agriculture. One such advancement is Bt crops.
What are Bt Crops?
Bacillus thuringiensis (or Bt) crops are genetically engineered/modified plants which are resistant to insects, parasites and other pests. Bt for plants was first used in mass to grow tobacco. Eggplants, cotton and corn. Afterwards, additional cash and food crops followed.
By 2016, more than 185 million hectares across the world grew Bt crops.
These crops have the endospore or crystal toxins of Bacillus thuringiensis, which makes them immune to pests. In 1995, the United States’ Environmental Protection Agency or EPA certified the use of these crops.
The power of transgenics allows humans to implant the Bt gene inside plant seeds. Note that the crystal toxins are also referred to as cry toxins.
Bt eggplant (known as Bt brinjal) and Bt Cotton are enormously popular in India.
It must be noted that there are several experts who do not appreciate this widespread usage of GM crops, both in India and abroad.
Task for you: Want to know how are Bt crops made? Log on to the official website of EPA and learn more on this subject. It is difficult but interesting. Also, you can check more details on cry toxins and how they ward off pests.
About Bt Crops in India
Bt brinjal was one of the first genetically modified, insect-resistant plants in India. It was introduced by the Maharashtra Hybrid Seed Company, also known as MAHYCO. Monsanto, one of the world’s foremost and also controversial seed manufacturers, helped MAHYCO develop the product.
Monsanto also holds a substantial stake in this Indian entity.
The agriculture of eggplants or brinjals in India has often been hampered due to a major pest: the eggplant shoot borer or Leucinodes orbonalis.
That risk, plus the amount of insecticide needed to keep the borer at bay, have been two reasons why Bt brinjal has been pushed in India.
This brinjal seed contains a specific gene- cry1Ac – which grants it protection against pests.
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For advanced Students: Agri-ethics and the necessity of GM crops are debated throughout the world. Identify and note down a list of Bt crops grown globally. Then, find out how Monsanto has helped in the production of Bt cotton-which we will learn.
There are several documentaries for and against Monsanto and Dow AgriSciences- another giant company. You can learn more about what is Bt gene.
Interestingly, in 2010, the then-Minister of Environment, Jairam Ramesh, had asked for a moratorium on the farming of Bt eggplants/brinjals till a comprehensive report was out.
In 2020, such GM brinjals are still sowed both legally and illegally.
What is Bt Cotton?
Bt cotton, produced by Monsanto as well as Dow AgriSciences, is another genetically engineered product commonly used in India. Using cry toxins, Bt cotton can withstand attacks by mothballs, beetles and butterfly larvae.
India has, since 2014, been the world’s largest producer of Bt cotton. The product was introduced by Monsanto and MAHYCO in 2002.
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Major Benefits of Bt Crops
Able to withstand pest attacks.
Minimal insecticide and fertiliser required, lowering production costs.
Increased productivity in smaller land patches.
Profitable for marginal farmers.
Drawbacks of Bt Crops
Seeds more expensive than conventional/common variants.
Pests may grow immune to the GM seeds.
Natural gene flow between crops is fatally sidelined.
Ethical issues. You may need to study more on these issues using Vedantu’s resources.
For more details on the latest research on GM crops, advanced students of biology can visit white-papers published by the United States’ National Center for Biotechnology Information and its NIH publications.
At Vedantu, we have a team of well-versed experts to form the study materials. For a detailed insight on various chapters of Biology, take a look at our rest of the notes today. You can also access all of our course materials from Vedantu’s app as well.
FAQs on Bt Crops Explained: Advantages, Disadvantages & Applications
1. What are Bt crops, and what does 'Bt' stand for?
Bt crops are genetically modified plants that have been engineered to produce an insecticidal protein. The term 'Bt' is an abbreviation for Bacillus thuringiensis, a naturally occurring soil bacterium that produces this protein. Scientists isolate the specific gene (often called the Cry gene) from the bacterium that codes for this insect-killing protein and insert it into the plant's genome. As a result, the plant can produce its own insecticide, providing protection against specific pests.
2. How does the Cry protein from Bacillus thuringiensis kill pests without harming humans?
The Cry protein is ingenious in its mechanism. It exists as an inactive protoxin inside the plant. When a target insect, such as a cotton bollworm, ingests the plant tissue, the alkaline pH of its gut activates the protoxin into a toxic form. This active toxin then binds to the insect's midgut epithelial cells, creating pores that cause cell swelling and lysis, ultimately leading to the insect's death. In contrast, the human gut has an acidic pH, which does not activate the protoxin, rendering it harmless to us.
3. What are some key examples of Bt crops developed for agriculture?
The most widely recognised example, particularly in India, is Bt cotton, which is genetically modified to resist the devastating cotton bollworm pest. It is the only GM crop approved for commercial cultivation in India. Other significant Bt crops developed and cultivated globally include:
- Bt corn (maize): Protects against pests like the European corn borer.
- Bt brinjal (eggplant): Developed to resist the fruit and shoot borer, though its commercial release is under a moratorium in India.
- Bt potato: Engineered for resistance against the Colorado potato beetle.
- Bt soybean: Provides protection against various lepidopteran pests.
4. What is the primary importance of using Bt crops in modern agriculture?
The primary importance of Bt crops lies in their ability to offer a more sustainable and efficient method of pest control. Key benefits include:
- Reduced Pesticide Use: Since the plants produce their own protection, the need for spraying external chemical insecticides is significantly reduced, which is better for the environment and farmer health.
- Increased Crop Yield: By effectively controlling major pests, Bt crops prevent significant yield losses, leading to higher productivity and farm income.
- Specificity: The Bt toxin is specific to a narrow range of insects (e.g., lepidopteran pests like bollworms), leaving most beneficial insects unharmed, unlike broad-spectrum chemical pesticides.
5. Why did Bt brinjal face a moratorium in India despite its potential to reduce pesticide use?
Bt brinjal's commercial cultivation was put on an indefinite hold in India due to several significant concerns raised by scientists, environmentalists, and the public. The primary reasons for the moratorium include:
- Biosafety Concerns: There were apprehensions about the lack of conclusive long-term studies on the impact of consuming Bt brinjal on human health.
- Environmental Impact: Fears were raised about the potential for the gene to transfer to wild relatives of brinjal through cross-pollination, and its effect on non-target organisms and overall biodiversity.
- Socio-Economic Issues: Concerns were also voiced about giving a few multinational corporations a monopoly over seeds, potentially making farmers overly dependent on them.
6. What is the biggest long-term risk associated with growing Bt crops?
The single most significant long-term risk associated with the widespread cultivation of Bt crops is the evolution of pest resistance. Just as bacteria can become resistant to antibiotics, insect populations can develop resistance to the Bt protein over several generations. If a significant portion of the pest population becomes resistant, the technology becomes ineffective. To mitigate this, farmers are often required to plant 'refugia'—small areas of non-Bt crops near the Bt fields—to ensure that a population of non-resistant insects survives and can interbreed, slowing the spread of the resistance gene.
