The transgenic maize refers to specific strains of genetically modified maize to express certain characteristics. From the point of view of agricultural production, these developed properties are, for example, resistance to pests and herbicides.
GMO corn has caused controversy regarding the potential effects on health and the ecosystem. One of the best known transgenic varieties is Bt corn. Genes have been added to it that come from a soil bacterium, Bacillus thuringiensis.
The bacteria produce insecticides; that is, it forms toxins that attack certain insects that are harmful to the plant. Hence, the Bt corn plant contains insecticides. Another transgenic characteristic added to corn is resistance to a general herbicide: glyphosate.
Glyphosate inhibits the synthesis of the EPSPS enzyme, which controls the manufacture of some aromatic amino acids necessary for the formation of the plant cell.
By introducing a modified gene into corn, the enzyme is not altered even though the plant has received the herbicide, and continues to grow. However, weeds do die.
Origin
Glyphosate resistant corn varieties were first marketed in 1996 by Monsanto, and are known as “Roundup® Ready corn” (RR corn). That same year, the first transgenic Bt corn was approved.
Bacillus thuringiensis bacteria naturally secrete up to twenty different insecticidal toxins (in the form of crystals called Cry) that specifically attack certain families of insects: Cry1 and Cry2 toxins for butterflies (Lepidopteran family), Cry3 for beetles, and Cry4 for diptera (flies), Bayer CropScience developed "Liberty Link Corn", which is resistant to glufosinate. One of the weeds that glyphosate seeks to combat is Aleppo sorghum, which retards the development of maize in intensive crops.
This weed ranks sixth among the top ten most damaging to world agriculture. Pioneer Hi-Bred has developed and markets corn hybrids with tolerance to herbicides such as imidazoline, under the trademark "Clearfield®".
Herbicide resistance in these hybrids was created by tissue culture selection and other procedures, and not by genetic engineering. Therefore, the regulatory framework governing the approval of GM crops does not apply to Clearfield®.
Since 2011, herbicide resistant and genetically modified corn has been grown in 14 countries. Since 2012, 26 varieties of herbicide-resistant transgenic corn have been authorized for import into the European Union.
In 2013 Monsanto released the first transgenic drought tolerance trait in a line of corn hybrids called DroughtGard.
The trait is provided by the insertion of a gene from the soil microorganism called Bacillus subtilis. It was approved by the USDA in 2011 and by China in 2013.
characteristics
- The transgenic corn plant produces itself the toxin that blocks the digestion of the target insect (s). This makes the entire plant protected against insect attack, unlike what happens with alternative treatments, which are usually only limited to its surface.
- The selectivity of the treatment is much higher. Each variant of the Bt molecule targets only one family of insects. However, the impact of its cumulative effects on the environment is not known.
- There is less emission of CO 2 to the environment because there are fewer fumigations, although others with fungicides are probably necessary to eliminate fungi and with other herbicides or insecticides to destroy other weeds and insects.
- Bt corn can be toxic to fauna, flora, soil microorganisms, pollinating insects and natural predators of harmful insects. If part of the plant's waste falls into rivers, it could have an effect on the fauna there. Several studies show that Bt has been found in rivers downstream of Bt corn crops.
- Prolonged exposure to Bt corn pollen affects the behavior and survival of the monarch butterfly (Danaus plexippus).
- Bt corn is harmful to important insects that naturally control corn pests. The green lacewing (Chrysoperla carnea) is affected by the toxicity of Bt corn. This transgenic corn harms the prey on which this insect feeds.
- The roots of the plant are porous. Many Bt crops secrete the toxin from the root into the soil. The residues in the field then contain the active Bt toxin. The long-term effects of this accumulation have not yet been evaluated.
Types
The types of transgenic corn are those that present:
- Tolerance to herbicides. Weeds have no commercial or nutritional value and take nutrients from the soil and sunlight from useful crops. Herbicides kill weeds, but few are selective and can affect produce. GMO corn is not affected by herbicides but weeds around it are.
- Resistance to insects. When a vulnerable insect eats the plant with Bt, the protein - which is alkaline - is activated in its gut. In an alkaline environment, the protein partially unfolds and is cut by others, forming a toxin that paralyzes the digestive system and creates holes in the intestinal wall. The insect does not eat and dies of starvation.
- Combination of both tolerances, herbicides and insect resistance.
- Resistance to drought.
- Traits to protect corn from worms.
- Tolerance to the maize streak virus (MSV). These strains have been propagated in Africa since 2014.
Consequences for health
- Transgenic corn can potentially cause more allergic reactions than crops resulting from conventional crosses.
- The presence of Bt toxin has been identified in the blood of pregnant women and their fetuses. It can then be concluded that the insecticide crosses the placenta.
- Other studies have linked the Bt toxin with cancer and the deterioration of kidney cells. This damage would be greater when the toxin is associated with glyphosate.
- Producers of genetically modified organisms (GMOs) use antibiotic resistance genes to select plant cells that have integrated the marker gene, the expression of which is to be obtained. Since these genes are in the plant to be consumed, their use could induce the development of resistance to antibiotics.
- Every living organism subjected to an external factor has a tendency to evolve due to mutation and selection. In this way, permanent contact with Bt corn has been creating resistance in some insects and weeds. This forces farmers to use other more toxic herbicides or insecticides, with the potential harmful effect on health.
- The great danger, like that of all transgenics, is the almost uncontrolled interaction of these crops for human consumption with a large, complex and not fully known ecosystem.
Advantage
- Better yields with less fertilizers, less pesticides and more nutrients. Its results are more predictable than traditional reproduction, in which the genetic transfer from each parent is made randomly to the offspring.
- Answers in a short time. The desired genotype can be instantly created in the current generation.
- Corn can be grown where the infestation previously destroyed crops or required large doses of toxic pesticides released into the environment, often killing beneficial insects in the process.
The long-term effects on the evolution of the species have not yet been determined. The impact that transgenic corn would have on evolution is speculative and has not been fully tested or verified as of yet.
References
- Bacillus thuringiensis (2018). Retrieved on April 16, 2018, at fr.wikipedia.org
- EPSP synthase (2018). Retrieved on April 16, 2018, at es.wikipedia.org
- Genetically modified maize (2018). Retrieved on April 16, 2018, at en.wikipedia.org
- What are the advantages and the inconvénients of the use of GMOs? (2014). Retrieved on April 16, 2018, at infogm.org
- Qu'est-ce qu'une planted Bt? (2014). Retrieved on April 16, 2018, at infogm.org
- Qu'est-ce qu'une plant tolerant a herbicide (Roundup Ready ou autre)? Retrieved on April 16, 2018, at infogm.org
- Lin D. (2017). The Pros and Cons of GMOs from a Vegan Perspective. Retrieved on April 17, 2018 at thoughtco.com
- Lundmark C. Genetically Modified Maize. BioScience. 2007 Dec. 57 (11) 996
- Maïs Bt (2018). Retrieved on April 16, 2018, at fr.wikipedia.org
- Pickut W (2017). What Are the Benefits of GMO Corn? Retrieved on April 17, 2018 at livestrong.com
- Pourquoi parle-t-on de nouveaux OGM? (2016). Retrieved on April 16, 2018, at infogm.org
- Pyrale du maïs (2018). Retrieved on April 16, 2018, at fr.wikipedia.org
- Sorghum halepense (2018). Retrieved on April 16, 2018, at es.wikipedia.org