Editing Genetically modified maize (section)

==== 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>