Bt Corn: An Example of a GMO Corn

The majority of corn grown in the United States today, and in many other parts of the world, is genetically modified. A prime example of this is Bt corn, a variety engineered to resist specific insect pests. This modification significantly reduces the need for chemical insecticide applications, offering a built-in defense mechanism against crop-damaging insects.

Quick Summary

This article explains how Bt corn, a genetically modified variety, functions to protect itself from insects. It details the process of genetic modification, contrasts Bt with conventional corn, and discusses the agricultural benefits and potential concerns surrounding its use in modern farming practices.

Key Points

• Bt corn is a specific example of GMO corn: It contains a gene from the bacterium Bacillus thuringiensis (Bt) that allows it to produce its own insecticide.

• Bt proteins target specific pests: The insecticide produced by Bt corn is toxic only to specific insect larvae, like the European corn borer, and is harmless to humans and beneficial insects.

• Reduced insecticide spraying: The built-in insect resistance of Bt corn significantly lowers the need for farmers to apply chemical insecticides to their fields.

• Lower mycotoxin risk: By minimizing insect damage, Bt corn also helps prevent fungal infections and the accumulation of harmful mycotoxins.

• GMO corn can have stacked traits: Many modern hybrids combine multiple modifications, such as Bt resistance and herbicide tolerance, to manage a wider range of agricultural challenges.

What is Bt Corn?

Bt corn is a variant of maize that has been genetically engineered to express one or more proteins from the bacterium Bacillus thuringiensis (Bt). This naturally occurring soil bacterium produces proteins, known as Cry toxins, that are poisonous to certain insect pests, particularly species of the European corn borer and the corn rootworm. By inserting the gene for this protein into the corn plant's DNA, the crop itself becomes capable of producing its own insecticide. When a vulnerable insect, such as a caterpillar, feeds on the Bt corn plant, the protein becomes activated in the insect's alkaline gut. This causes the insect to stop feeding, leading to its death within a few hours or days.

The creation of Bt corn involves several laboratory steps. First, the specific Bt gene that codes for the insecticidal protein is identified and isolated from the Bacillus thuringiensis bacterium. Next, this gene is copied and inserted into the DNA of the corn plant using techniques like gene guns or Agrobacterium-mediated transformation. Finally, the modified plant cells are grown in a lab and selected for regeneration into a full plant, which is then grown in greenhouses and field-tested. The resulting plant passes this insect-resistant trait to its offspring, providing long-lasting protection for farmers.

The Mechanism of Action

The effectiveness of Bt corn relies on a targeted mechanism of action. The Cry proteins produced by the corn plant must be ingested by the pest to be effective. The toxin is in an inactive state within the plant, but the alkaline conditions of a susceptible insect's gut trigger its activation. This activated toxin then binds to specific receptor proteins in the insect's gut wall, causing it to break down. This gut damage and eventual lysis of the cells paralyzes the insect's digestive system, causing it to stop feeding and leading to death. Critically, mammals, including humans and livestock, do not have the necessary receptors in their digestive systems for the toxin to bind, making it harmless to them.

Agricultural Impact and Benefits

The adoption of Bt corn has had significant effects on agricultural practices globally. It offers several benefits that have contributed to its widespread use in countries like the United States, Brazil, and Argentina. One of the most important advantages is the reduction in the need for external insecticide sprays, which can benefit both the environment and farm workers.

List of Advantages of Bt Corn

• Reduced Insecticide Use: By producing its own defense, Bt corn significantly lowers the amount of chemical insecticides that need to be sprayed on crops, reducing overall pesticide application.
• Targeted Pest Control: Unlike broad-spectrum pesticides that can harm beneficial insects, the Bt protein is highly specific to certain pests like the European corn borer, leaving beneficial insects like ladybugs and lacewings unharmed.
• Increased Yields: By protecting crops from destructive pests that bore into stalks and ears, Bt corn helps prevent damage and increases overall yield and crop quality.
• Reduction of Mycotoxins: Insect damage creates entry points for fungi, which can produce mycotoxins that are harmful to humans and animals. Bt corn, by reducing insect infestation, also lowers the risk of mycotoxin contamination.
• Simplified Pest Management: The built-in insect resistance simplifies pest control for farmers, providing consistent protection without the need for additional timing and application of separate insecticides.

Comparison: Bt Corn vs. Conventional Corn

To understand the full scope of Bt corn, it is helpful to compare it directly with its conventional, non-GMO counterpart. The differences lie in the genetic makeup, pest resistance, and overall management practices.

Feature	Bt Corn	Conventional Corn
Genetic Make-up	Contains a gene from Bacillus thuringiensis that produces insecticidal proteins.	Naturally occurring genetic make-up, no added genes for pest resistance.
Pest Resistance	Expresses insecticidal proteins throughout the plant, providing consistent, built-in protection against targeted pests.	Lacks built-in pest resistance; relies on external, sprayed insecticides to combat pests.
Insecticide Use	Significantly reduces the need for external insecticide applications.	Requires chemical insecticides to be sprayed to control insects, which can have broader environmental impacts.
Effect on Beneficial Insects	The specific mechanism only affects the targeted pests, making it less harmful to beneficial insect populations.	Broad-spectrum insecticides can unintentionally kill beneficial insects and pollinators.
Cost to Farmer	Seed costs are generally higher due to the embedded technology, but this can be offset by reduced pesticide and labor costs.	Seed costs are lower, but farmers must factor in the price of chemical insecticides and their application.
Mycotoxin Risk	Lower risk of mycotoxin contamination due to reduced insect damage.	Higher risk of fungal growth and mycotoxin production due to insect feeding.

Other Types of GMO Corn

Beyond insect resistance, other genetic modifications have been developed for corn. For instance, Roundup Ready Corn (RR Corn) is genetically engineered to be resistant to the herbicide glyphosate. This allows farmers to spray fields with glyphosate, killing weeds without harming the corn crop. Many modern hybrids now feature "stacked traits," combining both Bt and herbicide tolerance for comprehensive pest and weed management. Another example is DroughtGard corn, which was genetically engineered to be more tolerant of dry weather conditions.

Conclusion

Bt corn stands as a clear and widely used example of a GMO corn, demonstrating how genetic engineering can equip crops with desirable traits, such as insect resistance. By incorporating a gene from the natural soil bacterium Bacillus thuringiensis, this corn variety is able to produce a protein that is specifically toxic to pests like the European corn borer, but harmless to humans and most beneficial insects. This technology has led to reduced insecticide use, increased yields, and lower mycotoxin contamination in many agricultural regions. However, the adoption of Bt corn and other GMO crops is also part of a larger conversation about agricultural practices, pest resistance management, and environmental impact. As biotechnology continues to evolve, understanding examples like Bt corn is essential for grasping the complexities and applications of modern food production.

Citations

• U.S. Food and Drug Administration. (2024). GMO Crops, Animal Food, and Beyond. Retrieved from https://www.fda.gov/food/agricultural-biotechnology/gmo-crops-animal-food-and-beyond
• R-Biopharm AG. (2022). How to identify genetically modified corn. Retrieved from https://food.r-biopharm.com/news/how-to-identify-genetically-modified-corn/
• Abdelsalam, N.R. (2018). Genetically engineered (modified) crops (Bacillus thuringiensis crops) and the world controversy on their safety. Retrieved from https://ejbpc.springeropen.com/articles/10.1186/s41938-018-0051-2
• Manage Resistance Now. (n.d.). Bt Corn 101. Retrieved from https://manageresistancenow.ca/insects-bt-corn/ifs-bt-corn-101/
• UT Crops. (n.d.). Bt corn. Retrieved from https://utcrops.com/corn/insects/bt-corn/

Frequently Asked Questions

How does Bt corn produce its own insecticide?

Bt corn produces its own insecticide by incorporating a gene from the naturally occurring soil bacterium Bacillus thuringiensis into its DNA. This gene codes for a protein that is toxic to certain insects, and the corn plant expresses this protein throughout its tissues.

Is Bt corn safe for humans to eat?

Yes, regulatory agencies like the FDA and Health Canada have assessed Bt corn and deemed it safe for consumption. The protein produced by Bt corn only binds to specific receptors in the gut of target insect pests, which are not found in humans or other mammals.

What kind of insect pests does Bt corn protect against?

Bt corn is primarily effective against specific lepidopteran pests, such as the European corn borer, and coleopteran pests, including the corn rootworm. Different Bt genes can target different pests.

Does Bt corn affect beneficial insects, like ladybugs or honeybees?

No, the Bt proteins in corn are highly specific to certain target pests and do not harm beneficial insects such as ladybugs, lacewings, or honeybees. This is a key advantage over conventional, broad-spectrum insecticides.

Are all GMO corn varieties the same as Bt corn?

No, while Bt corn is a prominent example, there are other types of GMO corn with different traits. For example, Roundup Ready corn is engineered for herbicide tolerance, and many modern varieties have "stacked traits" combining multiple modifications.

Can insects develop resistance to Bt corn?

Yes, there is a risk of pests developing resistance to Bt toxins over time. To manage this, farmers are required to plant a portion of their fields with non-Bt corn, known as a 'refuge,' which helps slow the development of resistance.

What are stacked trait GMO corn hybrids?

Stacked trait hybrids are GMO corn varieties that have been engineered with multiple beneficial genes. For example, a single hybrid could be resistant to both insects (Bt) and herbicides (like Roundup Ready), offering combined protection.