How GM Plants Conquered the World
Genetically modified organisms (GMOs) are widely used in agriculture to give plants beneficial traits such as herbicide and pesticide resistance as well as quality traits that optimize growth and nutritional content. First trialed in the 1980s, GMO use is now widespread with over 185 million hectares of GM crops planted in 2016.
This article was published in Spot On #6
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What are GMOs?
Organisms that are genetically modified have undergone alterations to their genetic material in a process known as genetic engineering. These alterations result in the organism expressing a trait or traits that would not naturally occur in that organism. GMOs currently exist in bacteria, animals and plants, and are used in a wide range of applications including biological and medical research, the production of pharmaceuticals, and agriculture.
One of the most widely adopted uses of GMOs is in agriculturally important crops. In these plants, alterations to the genetic material are often accomplished by inserting DNA material from a different organism into the target organism. This results in the plant (and any seeds harvested from the plant) expressing novel traits, such as herbicide or insect resistance, or quality traits such as drought tolerance. For example, genetic modifications have been made so that plants are resistant to herbicides such as glyphosate or glufosinate, allowing a field to be sprayed with the herbicide to kill off weeds without harming the crop.
Genetic modification can also involve the transfer of a trait or traits that allow the plant to produce endotoxins originating from the soil bacterium Bacillus thuringiensis, known as “Bt”. This confers insect resistance. These endotoxin proteins have been used as spray-on insecticides since the 1920s. They target certain insect species while having no effect on non-target species such as humans, wildlife, and beneficial insects. When ingested, these proteins form pores in the midgut epithelium of the larvae of susceptible insect species (which feed on the crops, causing damage). This causes paralysis of the gut, and the affected insect stops feeding and succumbs to starvation. Non-target species have no receptors in the gut for the protein, and thus the protein has no effect on them. In addition, GMO plants may express quality traits that allow them to be tolerant to environmental conditions such as drought, or to improve their nutritional content.
GMO naming conventions
GMOs may be referred to in one of three ways. First, they may be identified by their event name, which is the name of the unique DNA recombination experiment that occurred in the laboratory in which one plant cell successfully incorporated a desired gene. That cell is subsequently used to regenerate whole plants and is the “foundation” of a GMO strain. For example, one event name for herbicide-tolerant corn is NK603. Second, GMOs may also be identified by the unique protein they express. In the case of event NK603, the protein expressed is CP4 EPSPS. Thirdly, the GMO may be identified by the trade name under which it is sold commercially.
GM crops around the world – then and now
Current GMO production mainly comprises four crops: soybeans, maize, cotton, and rapeseed/canola. Global trade of these crops and their main derivatives is dominated by material of GMO origin. In addition, global planting of these four crops includes a very high percentage of biotech seed (78% of soybean, 64% of cottonseed, 33% of maize, and 24% of canola globally; ISAAA 2016). Within these crops, there are several GMO proteins currently important to the grain and seed trade. The cultivation of GM plants is increasing globally, as is the utilization of stacked traits - including two or more novel traits in the same plant.
The first field trials of GM plants began in the United States and France in 1986, with herbicide-resistant tobacco. The first country to allow commercialized GMO plants was China, which introduced a virus-resistant tobacco in 1992. The first GM crop approved for sale in the US was the FlavrSavr tomato in 1994. In that year, the European Union also approved its first GM plant for sale, which was a herbicide-tolerant tobacco. Commercialized cultivation of GM plants such as corn and cotton began in 1996. In 2016, 11 different types of GM crops were commercially grown on 457 million acres (185 million hectares) in 26 different countries around the world.
The leading cultivators of GM crops
Table 1 shows the global cultivation of GMOs in 2016. Adoption rates of GM crops in the countries where they are planted is often high. USDA survey data from 2016 shows that herbicide-tolerant soybeans comprised 94% of the planted acreage in the United States, herbicide- tolerant cotton comprised 93% of the planted acreage, and herbicide-tolerant corn comprised 92% of the planted acreage. The corn plantings comprised 3% insect-resistant, 13% herbicide-tolerant, and 76% stacked insect-resistant/herbicide-tolerant varieties. The cottonseed plantings comprised 4% insect-resistant, 9% herbicide-tolerant, and 80% stacked insect-resistant/ herbicide-tolerant varieties. The US also planted biotech soybean (herbicide-tolerant), canola, sugarbeet, alfalfa, and others.
In Brazil, approximately 96.5% of soybean acreage was biotech. 36.7% of the acreage was herbicide-tolerant, and 59.8% was stacked insect-resistant/herbicide- tolerant. Approximately 88.4% of maize in Brazil is biotech, with the majority containing stacked traits. Approximately 79% of the cottonseed crop there was biotech. In Canada, approximately 93% of rapeseed/canola acreage is herbicide-tolerant. 94% of the soybean, 92% of the corn, and nearly 100% of the sugar beet is biotech. In India, approximately 96% of cotton planted is Bt. In China, biotech cotton comprised 95% of the acreage in 2016. In Paraguay, biotech resistant corn was first commercialized in 2013, and the adoption rate was already 44% by 2016. In Pakistan, 97% of cotton acreage was biotech.
GMO Proteins Important to the Grain and Seed Industry
- CP4 EPSPS
The expression of CP4 EPSPS transgenic protein in plants results in glyphosate herbicide tolerance. This protein is expressed in commercial varieties of creeping bentgrass, sugarbeet, rapeseed/canola, soybean, cotton, alfalfa, potato, wheat, and corn.
The expression of Bt-Cry1F transgenic protein results in insect resistance. This protein is effective against the larvae of lepidopteran pests such as the tobacco budworm, beet armyworm, soybean looper, cotton bollworm/ corn earworm, European corn borer, southwestern corn borer, fall armyworm, and black cutworm. This protein is expressed in commercial varieties of corn and cotton.
The expression of Bt-Cry34Ab1 transgenic protein in plants results in insect resistance. This protein is effective against the larvae of coleopteran pests such as the corn rootworm. This protein is expressed in commercial varieties of corn.
- Bt-Cry1Ab, 1Ac, & 1A.105
The expression of Bt-Cry1Ab, Cry1Ac, and/or 1A.105 transgenic protein results in insect resistance. The proteins are effective against the larvae of lepidopteran pests such as the European corn borer, tobacco budworm, cotton bollworm/corn earworm, pink bollworm, beet armyworm and soybean looper. These proteins are expressed in commercial varieties of corn, cotton, and tomato.
The expression Bt-Cry3Bb1 transgenic protein results in insect resistance. The protein is effective against the larvae of coleopteran pests such as the corn rootworm. This protein is expressed in commercial varieties of corn.
The expression of eCry3.1Ab transgenic protein results in insect resistance. The protein is effective against coleopteran and lepidopteran insects. This protein is expressed in commercial varieties of corn.
The expression of Bt-Cry2Ab transgenic protein results in insect resistance. The protein is effective against the larvae of lepidopteran pests such as the cotton bollworm, pink bollworm and tobacco budworm. This protein is expressed in commercial varieties of cotton.
The expression of PAT transgenic protein in plants results in Phosphinothricin (PPT) herbicide tolerance, specifically glufosinate ammonium. It is also often used as a selectable marker for genetic transformation. This protein is expressed in commercial varieties of corn, rapeseed/canola, cotton, chicory, sugarbeet, and rice.
The expression of VIP3A transgenic protein in plants results in insect resistance. This protein is effective against the larvae of lepidopteran pests such as the cotton bollworm/ corn earworm, tobacco budworm, pink bollworm, fall armyworm, beet armyworm, soybean looper, cabbage looper, cotton leaf perforator, black cutworm, and the western bean cutworm. This protein is expressed in commercial varieties of corn and cotton.
The PMI protein (phosphomannose isomerase) is expressed by a gene derived from E. coli. This protein allows growth on mannose and is often used as a selectable marker in GMO corn.
The NPTII protein (neomycin phosphotransferase) is expressed by a gene derived from E. coli. This protein allows resistance to aminoglycoside antibiotics such as kanamycin, neomycin, paromomycin, and geneticin (G418). It is a commonly used selectable marker.
The cspB (cold shock protein B) protein is expressed by a gene derived from Bacillus subtilis. This protein allows for improved performance under water stress conditions.
The expression of the DMO protein (dicamba monooxygenase) results in dicamba herbicide tolerance. This protein is expressed in commercial varieties of soybeans and cottonseed.
The expression of the aad-12 (aryloxyalkanoate dioxygenase 12) protein results in 2,4-D herbicide tolerance. This protein is expressed in commercial varieties of cotton and soybeans.
Many other countries do not cultivate GM crops, but have approved them for import as food and feed. In 2016, there were 115 food approvals, 87 feed approvals, and 49 cultivation approvals, for a total of 251 approvals. These approvals are divided among 87 events from seven crops. The most commonly approved GMOs are herbicide- tolerant traits. Since 2007, the number of approvals for stacked events has been more than for single events, and in 2016, 82.6% of the approved events were stacked. The trait distribution of approved events in 2016 was as follows: 14% insect-resistant, 15% product quality, 19% herbicide-tolerant, 6% herbicide-tolerant + pollination control, 3% herbicide-tolerant + product quality, 3% disease-resistant, 3% insect-resistant + disease-resistant, 31% herbicide-tolerant + insect-resistant, and 6% others.
The global use of biotech crops is increasing. These technologies can help provide new crops with higher yields, higher disease resistance, resistance to adverse environmental conditions and increased nutritional value. World opinion about the value of GMOs, however, is divided. Yet it is indisputable that GM crops have become a component of a strategy for many countries and companies looking to feed rapidly growing populations.