Transgenic Corn




General Information


Patents holders: AgrEvo, BASF, Bayer, Dow AgroSciences, DuPont, Monsanto Company, Novartis, Pioneer Hi-Bred International, Syngenta Seeds, Zeneca.
Area of Application: Agriculture

Market: more than 35 million hectares worldwide


Transgenic corn has been genetically engineered to gain certain agronomic advantages, such as herbicide tolerance and insect resistance. These two traits can also be expressed simultaneously («stacked» gene varieties).(1)


Facts and Figures

History


Genetic modified (GM) corn was grown for the first time in 1997, in USA and Canada. Since then, GM corn production has expanded to more than 35 million hectares worldwide, including South America, Africa, Asia and Europe, where it was first grown in Spain, in 1998, country that holds now the larger European production of GM corn. Other European countries that grow GM corn are Portugal, Czech Republic and Germany. GM corn is the only commercialized GM crop in EU.(1)

Herbicide Tolerant Corn


Herbicide tolerance is the most common GM trait in commercial agriculture. Plants that take advantage from it are part of a weed control system that consists of a non-selective herbicide and a corresponding herbicide tolerant crop, which is obtained by genetic engineering. This way, such herbicides can be used to kill weeds without damaging the crops.(1),(2) The method saves labor and cuts soil erosion up to 90 percent.(2)
Currently, two of the most used herbicide systems are Roundup Ready (active ingredient: glyphosate), commercialized by Monsanto, and LibertyLink (active ingredient: glufosinate), commercialized by Bayer.(1),(3)


Insect Resistant Corn


The soil bacterium Bacillus thuringiensis (Bt) expresses several proteins with toxin activity as insecticides for crop pests.(2),(4) Biotechnological agriculture allowed insect resistant crops to be engineered with Bt bacterium genes thus making the once insect food source a killer agent of the same,(4) lessening the use of chemical pesticides (2). The Bt toxins to engineer corn seeds with are selected for their toxicity toward economically significant insects. (4),(5) Only one gene or more («stacked» gene variety) can be used, protecting the corn from both corn-bor­er and corn-rootworm pests.(5) Bt toxins mode of action is still unknown, however, supposedly the toxin ingested by the larvae is activated in its own gut, leading to the formation of pores that release cellular fluids, ending in the larvae mortality.(4)
In 1996, the first Bt corn seed was approved by US Environmental Protection Agency (USEPA) as a safe pes­ticide under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). After that, approximately a dozen different Bt corn varieties were registered.(5) Bt corn is commercialized under several different trademarks such as YieldGard by Monsanto, among others.(3)

Insect Resistance Management

Nonetheless, a real threat hovers over Bt technology future: insect adaptation to Bt toxins, which has already been assessed. Insect resistance management (IRM) practices are therefore important to avoid such adverse environmental effect that would lead to larger use of higher risk chemical pesticides.(4),(5) In the light of this threat, US Environmental Protection Agency (USEPA) determined several refuge requirements and management practices to Bt corn plantations.(4),(5) In Europe, the European Food Safety Authority (EFSA) has the same responsibility.(6)

Economic and Intangible Benefits


The economic benefits of choosing GM crops are translated in US in savings of $2 billion due to increased yields and reductions in cost production and conventional pesticide use. Furthermore,
GM crops have been recognized to improve economies of people in developing countries, which is possible due to the small investing character of such technology, since it is incorporated into the crop seed itself.(2)
Intangible benefits include reduced insecticide use and therefore increased environmental safety, all-in-one product insect control and better pest control. Besides, in the Bt corn case, human safety and labor efficiency are increased since there is no need of handling an insecticide.(7)

Relevant Products

Herbicide Tolerant:
Product
Active Ingredient
Company
Roundup Ready
glyphosate
Monsanto
LibertyLink
glufosinate
Bayer
IMI (IR/IT)
imidazolinone
BASF

Insect Resistant:

Protect against
Product
Bt gene
Company
Single Bt gene
Corn borer pests
YieldGard Corn Borer
Cry 1Ab
Monsanto
Herculex I
Cry 1F
Dow Agro Sciences
Corn rootworm pests
YieldGard Rootworm
Cry 3Bb1
Monsanto
Herculex RW
Cry34/35Ab1
Dow Agro Sciences
Stacked Bt gene
Corn borer and corn rootworm pests
YieldGard Plus
Cry 1Ab and Cry 3Bb1
Monsanto
Herculex Xtra
Cry 1F and Cry34/35Ab1
Dow Agro Sciences

Both traits:

Product
Company
Stacked gene
YieldGard Plus with Roundup Ready Corn 2
Monsanto


References

(1) Genetically Modified Organisms Compass – (http://www.gmo-compass.org/eng/grocery_shopping/crops/18.genetically_modified_maize_eu.html)
(2) Guide to Biotechnology (2008), Biotechnology Industry Organization (BIO), 41-44.
(3) The Penn State Agronomy Guide 2009-2010: Field Crop Management -Section 2, Corn Pest Management, The Pennsylvania State University
- (http://agguide.agronomy.psu.edu/pm/sec2/sec21a.cfm)
(4) Glaser, J.A., Matten, S.R. (2003), Sustainability of insect resistance management strategies for transgenic Bt corn, Biotechnology Advances, 22: 45–69.
(
5) Complacency on the farm: Significant Noncompliance with EPA’s Refuge Requirements Threatens the Future Effectiveness of Genetically Engineered Pest-protected Corn (2009), Center for Science in the Public Interest, Washington DC.
(6) European Food Safety Authority (EFSA) - (
http://www.efsa.europa.eu/en/gmotopics/topic/gmo.htm)
(7) Rice, M.E. (2004), Transgenic Rootworm Corn: Assessing Potential Agronomic, Economic, and Environmental Benefits, Plant Management Network. – (http://www.plantmanagementnetwork.org/pub/php/review/2004/rootworm/)



Maria Inês Lopes

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