The transgenic corn refers to specific strains of corn genetically modified 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 potential health and ecosystem effects. One of the best known transgenic varieties is Bt corn. Genes that come from a soil bacterium have been added to it., 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 GMO 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 it continues to grow. However, weeds do die.
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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..
The bacteria Bacillus thuringiensis naturally secretes 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.
- The transgenic corn plant itself produces the toxin that blocks the digestion of the target insect (s). This means that the entire plant is 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 CO emissiontwo to the environment because there is less spraying, 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 a part of the plant's waste falls into the rivers, it could have effects on the fauna there. Several studies show that Bt has been found in rivers downstream of Bt maize crops..
- Long-term exposure to pollen from Bt maize affects the behavior and survival of the monarch butterfly (Danaus plexippus).
- Bt corn is detrimental to important insects that naturally control corn pests. The green lacewingChrysoperla carnea) It is affected by the toxicity of Bt corn. This transgenic corn harms the prey that this insect feeds on..
- 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..
The types of transgenic corn are those that present:
- Herbicide tolerance. 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 the weeds around it.
- 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 herbicide and insect resistance tolerances.
- Drought resistance.
- Traits to protect corn from worms.
- Tolerance to the maize streak virus (MSV). These strains have been propagated in Africa since 2014.
- GMO corn can potentially cause more allergic reactions than crops that result 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 to 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 desired. As 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..
- Better yields with less fertilizers, less pesticides and more nutrients. Its results are more predictable than traditional reproduction, in which the gene 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..
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