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GMOs: Growing Herbicide-Resistant Crops

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  • 0:05 Genetically Modified…
  • 1:55 What is Glyphosate,…
  • 2:56 How Were the Crops…
  • 4:18 Benefits and Risks of…
  • 5:56 Lesson Summary
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Lesson Transcript
Instructor: Betsy Chesnutt

Betsy teaches college physics, biology, and engineering and has a Ph.D. in Biomedical Engineering

Crops resistant to herbicides have revolutionized farming. In this lesson, learn how these crops were created and some of the benefits and risks of using them.

Genetically-Modified Herbicide-Resistant Crops

Imagine you are a farmer who planted many hundreds of acres of soybeans. Keeping weeds from taking over your fields and destroying your crop would probably be really important to you!

Herbicides are chemicals that are used to kill weeds, which sounds like a great solution. However, the problem is that they can also kill the crops that farmers are trying to protect. In the 1970s, some farmers noticed that certain weeds were resistant to the effects of herbicides. That means that they were able to survive despite being sprayed with herbicides that killed other nearby plants. The farmers realized they might be able to recreate this resistance in their own crops. By the 1980s, the first herbicide-resistant soybeans had been created by traditional breeding methods. Then, in 1996, the first soybeans genetically engineered to be herbicide resistant began to be sold commercially in the United States.

Today, scientists have used genetic engineering to create many more types of herbicide-resistant crops, including soybeans, cotton, and maize. Most herbicide-resistant crops have been developed to be resistant to only one type of broad-spectrum herbicide, glyphosate, which is sold commercially as Roundup. These herbicide-resistant crops, which are also known as Roundup Ready, allow farmers to apply glyphosate to kill many types of weeds without risking damage to their crops.

Although herbicide-resistant crops have been very commercially successful in the United States and more than 90% of all the soybeans grown today are glyphosate resistant, there is controversy over the safety of genetically engineered food, and these crops are still banned in many countries.

What Is Glyphosate, and How Does It Work?

Glyphosate is a very popular type of herbicide that's made by the biotech company Monsanto and sold commercially as Roundup. It prevents plants from producing certain essential amino acids, and without those amino acids, the affected plants usually die. In order to work, glyphosate must be absorbed by the leaves of a plant, so it usually must be applied repeatedly over a growing season as new weeds sprout.

Glyphosate is considered to be a relatively safe herbicide because it's rapidly degraded by bacteria in the soil. This means that it doesn't last very long once it's on the ground, or easily get into the water supply. Farmers prefer to use it because it's safe and kills many types of plants at once, but until crops resistant to glyphosate were developed, it would also kill the crops, so it wasn't practical. Today, glyphosate is the most widely used herbicide in the United States, mainly due to the prevalence of genetically modified glyphosate-resistant crops.

How Were the Crops Genetically Modified?

A genetically modified organism (GMO) is any organism whose DNA has been altered using genetic engineering techniques. GMOs are used in research and to produce food crops that are disease, pest, and herbicide-resistant, as well as crops that have increased nutritional value. Crops resistant to the herbicide glyphosate were developed in the 1980s and were first sold commercially in 1996.

Glyphosate works by inhibiting an enzyme in plants called EPSPS that is important in amino acid synthesis. The first genetically modified plants were soybeans that produced a modified form of EPSPS that was not affected by glyphosate. So, unlike many other GMOs, no new genes are present in herbicide-resistant plants, and no new proteins are expressed. The protein is just slightly changed so that it is no longer affected by glyphosate. This means that herbicide-resistant plants have very little genetic modification, and many people believe this makes them safer than other GMOs.

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