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Question

Have GMO crops been modified in order that the plants are resistant to poisonous pesticides being sprayed on them? And how exactly is this resistance bred?

Submitted by: deavonlea


Answer

Expert response from Community Manager

Thursday, 21/08/2014 20:19

Thank you very much for your question. I assume your use of the word “pesticide” is in its most common sense, which means it can be any type of plant-protection product that shields plants from damaging influences from weeds, pathogens or insects. Thus, for crops the term “pesticide” generally comprises three types of products: herbicide to control weeds, insecticides to control insects and fungicide to control plant diseases.
 
“GMO” is short for “genetically modified organism,” so I prefer to use the phrase “genetically engineered (GE) crops,” or “biotechnology crops,” instead. Genetic engineering is a biotechnology that introduces desired traits into an organism through DNA recombination. This technology can help plants to increase yields, combat different stresses (drought, high salinity, diseases) or make them more nutritious. Pesticide resistance, or pesticide tolerance, to be more accurate, is one of the reasons genetic engineering is used.
 
Let me use herbicide resistance as an example to illustrate why this trait is desirable and how it was incorporated into plants. Roundup is a nonselective, wide-spectrum herbicide (it kills many different types of weeds). Its active ingredient, glyphosate, impairs one enzyme, called 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), in the plants that is involved in synthesis of essential amino acids that animals cannot produce.


While Roundup kills weeds, it can kill the crops as well, when it comes in contact with them. So we need a mechanism to protect the crops from the herbicide. A version of EPSPS from the CP4 strain of the bacteria, Agrobacterium tumefaciens, was shown to be resistant to glyphosate. By incorporating this DNA fragment into soybean through genetic engineering, you will have soybean plants that are resistant to Roundup. This means you can spray Roundup in-crop from emergence through flowering for unsurpassed weed control. This expands growers’ weed-management options and allows for more environmentally benign farming practices.
 
Although relatively simple in theory, trait development is a complex process in a commercial setting. It may take about four to five years to find a desirable gene (the special version of EPSPS, in this case) and have it tested in model plants (Arabidopsis most of the time), and another two years for the proof of concept in the targeted crop. Then a large number (usually between five hundred and two thousand) of transgenic events (the unique DNA recombination event that took place in one plant cell, which is then used to generate entire transgenic plants) is produced and selected at both a molecular and a field level. Normally, only one or two events will be advanced to the next phase. This step takes an additional two to three years. Then it is time to integrate this trait into a variety of commercial germplasms through conventional breeding methods to meet the requirements of different geographical growing regions. This process, often referred to as conversion, will take about another four to five years.
 
In parallel, these GE crops are tested for their safety as food, feed and environment to be able to pass regulatory assessment. Altogether, it may take about 13 years and $136 million from gene discovery to launch of a commercial product.

Answer

Expert response from Community Manager

Thursday, 21/08/2014 20:19

Thank you very much for your question. I assume your use of the word “pesticide” is in its most common sense, which means it can be any type of plant-protection product that shields plants from damaging influences from weeds, pathogens or insects. Thus, for crops the term “pesticide” generally comprises three types of products: herbicide to control weeds, insecticides to control insects and fungicide to control plant diseases.
 
“GMO” is short for “genetically modified organism,” so I prefer to use the phrase “genetically engineered (GE) crops,” or “biotechnology crops,” instead. Genetic engineering is a biotechnology that introduces desired traits into an organism through DNA recombination. This technology can help plants to increase yields, combat different stresses (drought, high salinity, diseases) or make them more nutritious. Pesticide resistance, or pesticide tolerance, to be more accurate, is one of the reasons genetic engineering is used.
 
Let me use herbicide resistance as an example to illustrate why this trait is desirable and how it was incorporated into plants. Roundup is a nonselective, wide-spectrum herbicide (it kills many different types of weeds). Its active ingredient, glyphosate, impairs one enzyme, called 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), in the plants that is involved in synthesis of essential amino acids that animals cannot produce.


While Roundup kills weeds, it can kill the crops as well, when it comes in contact with them. So we need a mechanism to protect the crops from the herbicide. A version of EPSPS from the CP4 strain of the bacteria, Agrobacterium tumefaciens, was shown to be resistant to glyphosate. By incorporating this DNA fragment into soybean through genetic engineering, you will have soybean plants that are resistant to Roundup. This means you can spray Roundup in-crop from emergence through flowering for unsurpassed weed control. This expands growers’ weed-management options and allows for more environmentally benign farming practices.
 
Although relatively simple in theory, trait development is a complex process in a commercial setting. It may take about four to five years to find a desirable gene (the special version of EPSPS, in this case) and have it tested in model plants (Arabidopsis most of the time), and another two years for the proof of concept in the targeted crop. Then a large number (usually between five hundred and two thousand) of transgenic events (the unique DNA recombination event that took place in one plant cell, which is then used to generate entire transgenic plants) is produced and selected at both a molecular and a field level. Normally, only one or two events will be advanced to the next phase. This step takes an additional two to three years. Then it is time to integrate this trait into a variety of commercial germplasms through conventional breeding methods to meet the requirements of different geographical growing regions. This process, often referred to as conversion, will take about another four to five years.
 
In parallel, these GE crops are tested for their safety as food, feed and environment to be able to pass regulatory assessment. Altogether, it may take about 13 years and $136 million from gene discovery to launch of a commercial product.