Editing Genetically modified maize (section)

== Marketed products ==

=== Herbicide-resistant maize ===
Corn varieties resistant to [[glyphosate]] herbicides were first commercialized in 1996 by [[Monsanto]], and are known as "Roundup Ready Corn". They tolerate the use of [[Roundup (herbicide)|Roundup]].<ref>{{cite web|title=Roundup Ready System |url=http://www.monsanto.com/weedmanagement/Pages/roundup-ready-system.aspx |publisher=Monsanto |url-status=dead |archive-url=https://web.archive.org/web/20130402204619/http://www.monsanto.com/weedmanagement/Pages/roundup-ready-system.aspx |archive-date=2 April 2013 }}</ref> [[Bayer CropScience]] developed "Liberty Link Corn" that is resistant to [[glufosinate]].<ref>{{cite web |url=http://www.bayercropscience.us/products/herbicides/liberty/|title=Bayer LibertyLink official website|publisher=Bayer Crop Science|access-date=28 October 2014}}</ref> [[Pioneer Hi-Bred]] has developed and markets corn hybrids with tolerance to [[imidazoline]] herbicides under the trademark "Clearfield" – though in these hybrids, the herbicide-tolerance trait was bred using tissue culture selection and the chemical mutagen ethyl methanesulfonate, not [[genetic engineering]].<ref name="imidcorn" >{{cite journal | vauthors = Tan S, Evans RR, Dahmer ML, Singh BK, Shaner DL | title = Imidazolinone-tolerant crops: history, current status and future | journal = Pest Management Science | volume = 61 | issue = 3 | pages = 246–57 | date = March 2005 | pmid = 15627242 | doi = 10.1002/ps.993 }}</ref> Consequently, the regulatory framework governing the approval of transgenic crops does not apply for Clearfield.<ref name="imidcorn" />

As of 2011, herbicide-resistant GM corn was grown in 14 countries.<ref>{{cite web | vauthors = James C |title=ISAAA Brief 43, Global Status of Commercialized Biotech/GM Crops: 2011|work=ISAAA Briefs|publisher=International Service for the Acquisition of Agri-biotech Applications (ISAAA)|location=Ithaca, New York|year=2011|url=http://www.isaaa.org/resources/publications/briefs/43/executivesummary/default.asp|access-date=27 July 2012}}</ref> By 2012, 26 varieties of herbicide-resistant GM maize were authorised for import into the [[European Union]],<ref>{{cite web | author = Staff | url = http://ec.europa.eu/food/dyna/gm_register/index_en.cfm | title = EU register of genetically modified food and feed | work = European Commission, Health and Consumers, EU register of authorised GMOs | access-date = 26 August 2012 }}</ref> but such imports remain controversial.<ref>{{cite web | vauthors = Hogan M | date = 5 April 2012 | url = https://www.reuters.com/article/us-germany-gmo-basf-idUSBRE8340Y120120405 | title = BASF to undertake GMO potato trials in Europe | work = Reuters Edition US | access-date = 26 August 2012 }}</ref> Cultivation of herbicide-resistant corn in the EU provides substantial farm-level benefits.<ref name="Wesseler-2007">{{cite journal | vauthors = Wesseler J, Scatasta S, Nillesen E | title = The maximum incremental social tolerable irreversible costs (MISTICs) and other benefits and costs of introducing transgenic maize in the EU-15. | journal = Pedobiologia | date = August 2007 | volume = 51 | issue = 3 | pages = 261–9 | doi = 10.1016/j.pedobi.2007.04.004 | url = https://mpra.ub.uni-muenchen.de/33229/1/MPRA_paper_33229.pdf }}</ref>

=== Insect-resistant corn ===
[[Image:Corn borer.jpg|right|thumb|200px|The [[European corn borer]], ''Ostrinia nubilalis'', destroys corn crops by burrowing into the stem, causing the plant to fall over.]]

==== Bt maize/corn ====
{{visible anchor|Bt maize}}/{{visible anchor|Bt corn}} is a variant of [[maize]] that has been [[genetic engineering|genetically altered]] to express one or more [[protein]]s from the [[bacteria|bacterium]] ''[[Bacillus thuringiensis]]''<ref name="UC-history"/> including [[Delta endotoxin]]s. The protein is poisonous to certain insect pests. Spores of the bacillus are widely used in [[organic gardening]],<ref>{{cite web |url=http://www.bt.ucsd.edu/organic_farming.html|title=Bt Crop Spraying|work=ucsd.edu}}</ref> although GM corn is not considered organic. The [[European corn borer]] causes about a billion dollars in damage to corn crops each year.<ref>{{cite book | vauthors = Witkowski JF, Wedberg JL, Steffey KL, Sloderbeck PE, Siegfried BD, Rice ME, Pilcher CD, Onstad DW, Mason CE, Lewis LC, Landis DA, Keaster AK, Huang F, Higgins RA, Haas MJ, Gray ME, Giles KL, Foster JE, Davis PM, Calvin DD, Buschman LL, Bolin PC, Barry BD, Andow DA, Alstad DN | display-authors = 6 | veditors = Ostlie KR, Hutchison KR, Hellmich RL | chapter = Why manage European corn borer? | title = Bt Corn & European Corn Borer: Long-term Success Through Resistance Management | work = University of Minnesota Extension Office | publisher = North Central Region (NCR) | date = 1997 | url = http://www.extension.umn.edu/distribution/cropsystems/dc7055.html#ch1 | archive-url = https://web.archive.org/web/20130928064604/http://www.extension.umn.edu/distribution/cropsystems/dc7055.html#ch1 | archive-date=28 September 2013 }}</ref>

In recent years, traits have been added to ward off [[Helicoverpa zea|corn ear worms]] and [[Diabrotica|root worms]], the latter of which annually causes about a billion dollars in damages.<ref>{{cite journal | vauthors = Marra MC, Piggott NE, Goodwin BK | date = 2012 | url = https://agbioforum.org/the-impact-of-corn-rootworm-protected-biotechnology-traits-in-the-united-states/ | title = The impact of corn rootworm protected biotechnology traits in the United States | journal = AgBioForum | volume = 15 | issue = 2 | pages = 217–230 }}</ref><ref>{{cite web | vauthors = Hodgson EW | work = Utah State University Extension and Utah Plant Pest Diagnostic Laboratory | url = http://extension.usu.edu/files/publications/factsheet/western-corn-rootworm.pdf | title = Western corn rootworm }}</ref>

The Bt protein is expressed throughout the plant. When a vulnerable insect eats the Bt-containing plant, the protein is activated in its [[gut (anatomy)|gut]], which is [[alkaline]]. In the alkaline environment, the protein partially unfolds and is cut by other proteins, forming a [[toxin]] that paralyzes the insect's digestive system and forms holes in the gut wall. The insect stops eating within a few hours and eventually starves.<ref name="Grochulski_1995">{{cite journal | vauthors = Grochulski P, Masson L, Borisova S, Pusztai-Carey M, Schwartz JL, Brousseau R, Cygler M | title = Bacillus thuringiensis CryIA(a) insecticidal toxin: crystal structure and channel formation | journal = Journal of Molecular Biology | volume = 254 | issue = 3 | pages = 447–64 | date = December 1995 | pmid = 7490762 | doi = 10.1006/jmbi.1995.0630 }}</ref><ref name=ColoSt>{{cite web| vauthors = Peairs FB |publisher=Colorado State University Extension Office|year= 2013|url=http://extension.colostate.edu/docs/pubs/crops/00707.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://extension.colostate.edu/docs/pubs/crops/00707.pdf |archive-date=2022-10-09 |url-status=live|title=Bt Corn: Health and the Environment – 0.707}}</ref>

In 1996, the first GM maize producing a Bt Cry protein was approved, which killed the European corn borer and related species; subsequent Bt genes were introduced that killed corn rootworm larvae.<ref name=NatureEd>{{cite journal | vauthors = Hellmich RL, Hellmich KA | title = Use and impact of Bt maize. | journal = Nature Education Knowledge | date = 2012 | volume = 3 | issue = 10 | pages = 4 | url = http://www.nature.com/scitable/knowledge/library/use-and-impact-of-bt-maize-46975413 }}</ref>

The [[Government of the Philippines|Philippine Government]] has promoted Bt corn, hoping for insect resistance and higher yields.<ref name="Freedman-2013">{{cite journal | vauthors = Freedman A | title=Rice security in Southeast Asia: beggar thy neighbor or cooperation? | journal=[[The Pacific Review]] | publisher=[[Taylor & Francis]] | volume=26 | issue=5 | year=2013 | issn=0951-2748 | doi=10.1080/09512748.2013.842303 | pages=433–454| s2cid=153573639 }} p.{{spaces}}443</ref>

Approved Bt genes include single and stacked (event names bracketed) configurations of: Cry1A.105 (MON89034), CryIAb ([[MON 810|MON810]]), CryIF (1507), Cry2Ab (MON89034), [[Cry3Bb1]] ([[MON 863|MON863]] and MON88017), Cry34Ab1 (59122), Cry35Ab1 (59122), mCry3A (MIR604), and Vip3A (MIR162), in both corn and cotton.<ref>{{cite web | vauthors = Bessin R | work = University of Kentucky College of Agriculture | orig-date = first published May 1996 | date = November 2010 | url = http://www2.ca.uky.edu/entomology/entfacts/ef118.asp | title = Bt-Corn for Corn Borer Control }}</ref><ref>{{cite book | vauthors = Castagnola AS, Jurat-Fuentes, JL | chapter = Bt Crops: Past and Future. Chapter 15 | title = ''Bacillus Thuringiensis'' Biotechnology | veditors = Sansinenea E | publisher = Springer | date = 2 March 2012 }}</ref>{{rp|285ff}} Corn genetically modified to produce VIP was first approved in the US in 2010.<ref>{{cite web | vauthors = Hodgson E, Gassmann A | work = Iowa State Extension, Department of Entomology | date = May 2010 | url = http://www.extension.iastate.edu/CropNews/2010/0510hodgsongassman.htm | title = New Corn Trait Deregulated in the U.S. }}</ref>

A 2018 study found that Bt-corn protected nearby fields of non-Bt corn and nearby vegetable crops, reducing the use of pesticides on those crops. Data from 1976 to 1996 (before Bt corn was widespread) was compared to data after it was adopted (1996–2016). They examined levels of the [[European corn borer]] and [[Helicoverpa zea|corn earworm]]. Their larvae eat a variety of crops, including peppers and green beans. Between 1992 and 2016, the amount of insecticide applied to New Jersey pepper fields decreased by 85 percent. Another factor was the introduction of more effective pesticides that were applied less often.<ref>{{Cite news|url=https://arstechnica.com/science/2018/03/planting-gmos-kills-so-many-bugs-that-it-helps-non-gmo-crops/|title=Planting GMOs kills so many bugs that it helps non-GMO crops| vauthors = Gittig D |date=15 March 2018|work=Ars Technica|access-date=13 April 2018|language=en-us}}</ref>

==== Sweet Corn ====
GM sweet corn varieties include "Attribute", the brand name for insect-resistant sweet corn developed by [[Syngenta]]<ref>{{cite web|url=http://www.syngenta-us.com/seeds/vegetables/sweet_corn/Sweet_Corn_Crop_Guide.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.syngenta-us.com/seeds/vegetables/sweet_corn/Sweet_Corn_Crop_Guide.pdf |archive-date=2022-10-09 |url-status=live|title=Syngenta Sweet Corn Products|website=syngenta-us.com|access-date=8 April 2018}}</ref> and ''Performance Series'' insect-resistant sweet corn developed by Monsanto.<ref>{{cite web|url=https://www.seminis.com/global/us/SiteCollectionDocuments/Stewardship/2013_Sweet%20Corn_TUG_.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.seminis.com/global/us/SiteCollectionDocuments/Stewardship/2013_Sweet%20Corn_TUG_.pdf |archive-date=2022-10-09 |url-status=live|title=U.S. Technology Use Guide|publisher=Monsanto|year=2013}}</ref>

==== Cuba ====
While Cuba's agriculture is largely focused on organic production, as of 2010, the country had developed a variety of genetically modified corn that is resistant to the [[palomilla moth]].<ref name=Commission>Anna Glayzer for The Food Commission. 19 July 2010 [http://www.foodcomm.org.uk/articles/cubas_food_production_revolution/ Cuba's food production revolution]</ref>

===Drought-resistant maize ===
In 2013 [[Monsanto]] launched the first transgenic drought tolerance trait in a line of corn hybrids called DroughtGard.<ref>{{cite web | work = OECD BioTrack Database | url = http://www2.oecd.org/biotech/Product.aspx?id=MON-8746%C3%98-4 | title = MON87460 | access-date = 15 March 2014 | archive-date = 1 July 2017 | archive-url = https://web.archive.org/web/20170701140407/http://www2.oecd.org/biotech/Product.aspx?id=MON-8746%C3%98-4 | url-status = dead }}</ref> The MON 87460 trait is provided by the insertion of the cspB gene from the soil microbe ''[[Bacillus subtilis]]''; it was approved by the USDA in 2011<ref>{{cite journal | url = http://www.aphis.usda.gov/brs/fedregister/BRS_20111227c.pdf | author = Department of Agriculture, Animal and Plant Health Inspection Service | id = APHIS–2011–0023 | title = Monsanto Co.; Determination of Nonregulated Status of Corn Genetically Engineered for Drought Tolerance | journal = Federal Register | volume = 76 | issue = 248 | date = 27 December 2011 }}</ref> and by China in 2013.<ref name="pmid24067764">{{cite journal | vauthors = Eisenstein M | title = Plant breeding: Discovery in a dry spell | journal = Nature | volume = 501 | issue = 7468 | pages = S7–9 | date = September 2013 | pmid = 24067764 | doi = 10.1038/501S7a | bibcode = 2013Natur.501S...7E | doi-access = free }}</ref>

==== Health Safety ====
In regular corn crops, insects promote [[Fungus|fungal]] colonization by creating "wounds," or holes, in corn kernels. These wounds are favored by fungal [[spore]]s for [[germination]], which subsequently leads to [[mycotoxin]] accumulation in the crop that can be carcinogenic and toxic to humans and other animals. This can prove to be especially devastating in developing countries with drastic climate patterns such as high temperatures, which favor the development of toxic fungi. In addition, higher mycotoxin levels leads to market rejection or reduced market prices for the grain. GM corn crops encounter fewer insect attacks, and thus, have lower concentrations of mycotoxins. Fewer insect attacks also keep corn ears from being damaged, which increases overall yields.<ref>{{cite journal | vauthors = Pellegrino E, Bedini S, Nuti M, Ercoli L | title = Impact of genetically engineered maize on agronomic, environmental and toxicological traits: a meta-analysis of 21 years of field data | journal = Scientific Reports | volume = 8 | issue = 1 | pages = 3113 | date = February 2018 | pmid = 29449686 | pmc = 5814441 | doi = 10.1038/s41598-018-21284-2 | bibcode = 2018NatSR...8.3113P }}</ref>