Genetically modified maize

From Wikipedia, the free encyclopedia
  (Redirected from Transgenic maize)
Jump to: navigation, search
This article has multiple issues. Please help improve it or discuss these issues on the talk page.
This article may require cleanup to meet Wikipedia's quality standards. The specific problem is: many unverifiable/uncited assumptive claims, see: WP:NPOV and WP:V.. Please help improve this article if you can. (November 2010)
This article's lead section may not adequately summarize key points of its contents. Please consider expanding the lead to provide an accessible overview of all important aspects of the article. (May 2013)
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (May 2013)

Genetically modified maize (corn) is a recombineered corn plant with agronomically desirable traits.

Contents

Herbicide resistant corn[edit]

Corn varieties resistant to glyphosate herbicides (Liberty and Roundup) were first commercialized in 1996 by Monsanto.[1] Pioneer Hi-Bred has since marketed 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.[2] Consequently, the regulatory framework governing the approval, use, trade and consumption of transgenic crops does not apply for imidazoline-tolerant corn.[2]

Herbicide-resistant GM corn is grown in 14 countries.[3] By 2012, 26 varieties herbicide-resistant GM maize were authorised for import into the European Union,.[4] but such imports remain controversial even though in 2012 the EU was reported to import 30 million tons a year of GM crops[5] and cultivation of herbicide-resistant corn in the EU provides substantial farm-level benefits.[6]

In January 2013, the European Food Safety Authority released all data submitted by Monsanto in relation to the 2003 authorisation of maize genetically modified for glyphosate tolerance.[7]

Bt corn[edit]

The European corn borer, Ostrinia nubilalis, destroys corn crops by burrowing into the stem, causing the plant to fall over.

Bt corn is a variant of maize that has been genetically altered to express the bacterial Bt toxin, which is poisonous to certain insect pests. In the case of corn, the pest is the European corn borer. In recent years, traits have also been added to ward off Corn ear worms and Root worms.

Expressing the toxin was achieved by inserting a gene from the microorganism Bacillus thuringiensis into the corn genome. This gene codes for a toxin that causes the formation of pores in the Lepidoptera larval digestive tract. These pores allow naturally occurring enteric bacteria, such as E. coli and Enterobacter, to enter the hemocoel, where they multiply and cause sepsis.[8] This is contrary to the common misconception that Bt toxin kills the larvae by starvation.

In 2004, Bt176 varieties were voluntarily withdrawn from the list of approved varieties by the United States Environmental Protection Agency (EPA) when it was found to have little or no Bt expression in the ears and was not found to be effective against second generation corn borers.

Debate over the effects of Bt corn on nontarget insects[edit]

In May 1999, a laboratory at Cornell University submitted the results from a laboratory trial to Nature. The trial appeared to indicate the pollen of genetically modified Bt corn presented a threat to monarch caterpillars. Unlike many pesticides, the Bt-corn has been shown to have no effect on many "nontarget" organisms—pollinators such as honeybees or beneficial predators of pests like ladybugs. But the Bt-modified corn produces pollen containing crystalline endotoxin from the bacterium genes. When this corn pollen is dispersed by the wind, it lands on other plants, including milkweed, the exclusive food of monarch caterpillars and commonly found around cornfields. In the laboratory tests, monarchs fed milkweed leaves dusted with so-called transformed pollen from a Bt-corn hybrid ate less, grew more slowly and suffered a higher mortality rate, the researchers report. Nearly half of these larvae died, while all of the monarch caterpillars fed leaves dusted with nontransformed corn pollen or fed leaves without corn pollen survived the study. Several factors make monarch caterpillars particularly likely to make contact with corn pollen, Losey says. Monarch larvae feed exclusively on milkweed because it provides protection against predators. The plant contains cardenolides, which are toxic, bitter chemicals that the monarch caterpillar incorporates into its body tissues, rendering it unpalatable to predators. Milkweed grows best in "disturbed" habitats, like the edges of cornfields, Losey notes.

Greenpeace was one of the first to pick up the information and launch a campaign against Bt corn in Europe. The responses to the poor science were too late and too poorly framed to be effective.

Preventing Bt resistance in pests[edit]

By law, farmers in the United States who plant Bt corn must plant non-Bt corn nearby. These unmodified fields are to provide a location to harbor pests. The theory behind these refuges is to slow the evolution of the pests' resistance to the Bt pesticide. Doing so enables an area of the landscape where wild type pests will not be immediately killed.

It is anticipated resistance to Bt will evolve in the form of a recessive allele in the pest. Because of this, a pest that gains resistance will have an incredibly higher fitness than the wild type pest in the Bt corn fields. If the resistant pest is feeding in the non-Bt corn nearby, the resistance is neutral and offers no advantage to the pest over any nonresistant pest. Ensuring there are at least some breeding pests nearby that are not resistant increases the chance the resistant pests will choose to mate with nonresistant ones. Since the gene is recessive, all offspring will be heterozygous, and the offspring from that mating will not be resistant to Bt and therefore no longer a threat. Using this method, scientists and farmers hope to keep the number of resistant genes very low, and use genetic drift to ensure any resistance that does emerge does not spread.

Although mandated by law, compliance data from the EPA for 2008 showed, however, 25% of Bt corn growers were not in compliance. The data showed noncompliance climbed to 13.23 million acres (53,500 km2), or almost 15% of all Bt corn grown, suggesting in some areas ample acreage does not exist to support pests without resistance to mate with any resistant pests that survived the Bt corn.[9]

The European corn borer, one of the primary insects Bt is meant to target, has been shown to be capable of developing resistance to the Bt protein.[10]

Cross pollination[edit]

The non-Bt pesticide status of the refuges is being compromised by wind-borne pollen drifting into the non-Bt corn fields. Corn harvested from the supposed Bt-free zones has shown traces of Bt toxin. The levels found in the non-Bt corn decreases with distance from the Bt-corn fields, indicating the pollen is wind-borne rather than another method of transfer. The concentrations in the refuge fields were found to be low-to-moderate.

Possible solutions to the cross pollination problem are to plant a wider refuge field or plant varieties of corn that bloom at different times than the Bt fields do.[11]

Sweet corn for human consumption[edit]

"Attribute" is the brand name for a line of Bt sweet corn. Seed is available only to large professional farmers who sign a stewardship agreement. The farmer must agree to not repackage or resell Attribute seed. Growers also must grow the corn exactly as directed.

Safety issues[edit]

The French High Council of Biotechnologies Scientific Committee reviewed the 2009 Vendômois et al. study and concluded that it "..presents no admissible scientific element likely to ascribe any haematological, hepatic or renal toxicity to the three re-analysed GMOs."[12] However, French government applies a principle of precaution against GMOs. A review by Food Standards Australia New Zealand and others of the 2009 Vendômois et al. study concluded that the results were due to chance alone.[13][14]

A 2011 Canadian study looked at the presence of CryAb1 protein (BT toxin) in non-pregnant women, pregnant women and fetal blood. All groups had detectable levels of the protein in blood, including 93% of pregnant women and 80% of fetuses at concentrations of 0.19 ± 0.30 and 0.04 ± 0.04 mean ± SD ng/ml, respectively.[15] The paper did not discuss safety implications or find any health problems. The paper has been found to be unconvincing by several authors and organizations.[16][17][18] In a swine model, Cry1Ab-specific antibodies were not detected in pregnant sows or their offspring and no negative effects from feeding Bt maize to pregnant sows were observed.[19]

StarLink corn controversy[edit]

StarLink is a variety of Bt corn patented by Aventis Crop Sciences (a subdivision of Aventis, acquired by Bayer AG in 2002), intended for use in animal feed.

U.S. regulatory authorities permitted the commercial sale of StarLink seed with the stipulation that crops produced must not be used for human consumption. This restriction was based on the possibility that a small number of people might develop an allergic reaction to the Bt protein used in StarLink that is less rapidly digested than the version used in other Bt varieties.

StarLink corn was subsequently found in food destined for consumption by humans. An episode involving Taco Bell taco shells was particularly well publicized.[20] This led to a public relations disaster for Aventis and the biotechnology industry as a whole. Sales of StarLink seed were discontinued. The registration for Starlink varieties was voluntarily withdrawn by Aventis in October 2000.[21]

28 people reported apparent allergic reactions related to eating corn products that may have contained the Starlink protein. However, the US Centers for Disease Control studied the blood of these individuals and concluded there was no evidence the reactions these people experienced were associated with hypersensitivity to the Starlink Bt protein.[22]

A subsequent review of these tests by the Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel points out that while "the negative results decrease the probability that the Cry9C protein is the cause of allergic symptoms in the individuals examined ... in the absence of a positive control and questions regarding the sensitivity and specificity of the assay, it is not possible to assign a negative predictive value to this"[23]

Aid sent by the UN and the US to Central African nations also contained some StarLink corn. The nations involved[which?] refused to accept the aid.[citation needed]

The southern portion of the U.S. corn belt planted the greatest amount of StarLink corn. It is this portion of the U.S. where corn borer damage creates the greatest economic loss to farmers.

The US corn supply has been monitored for the presence of the Starlink Bt proteins since 2001. No verified positive test for the protein for dry milling have been found since 2003.[24]

Virus-resistant corn[edit]

In 2007, researchers from South Africa announced the production of transgenic maize resistant to maize streak disease (MSD), caused by maize streak virus (MSV).[25] This variety of maize is still in the research-and-development phase.

Varieties[edit]

See also[edit]

References[edit]

  1. ^ "Roundup Ready System". Monsanto. 
  2. ^ a b Tan, S.; Evans, R. R.; Dahmer, M. L.; Singh, B. K.; Shaner, D. L. (2005). "Imidazolinone-tolerant crops: History, current status and future". Pest Management Science 61 (3): 246–257. doi:10.1002/ps.993. PMID 15627242. 
  3. ^ James, C (2011). "ISAAA Brief 43, Global Status of Commercialized Biotech/GM Crops: 2011". ISAAA Briefs. Ithaca, New York: International Service for the Acquisition of Agri-biotech Applications (ISAAA). Retrieved 2012-07-27. 
  4. ^ Staff EU register of genetically modified food and feed European Commission, Health and Consumers, EU register of authorised GMOs, Retrieved 26 August 2012
  5. ^ Hogan, Michael (5 April 2012) BASF to undertake GMO potato trials in Europe Reuters Edition US, Accessed 26 August 2012
  6. ^ Wesseler, J., S. Scatasta, E. Nillesen (2007): The Maximum Incremental Social Tolerable Irreversible Costs (MISTICs) and other Benefits and Costs of Introducing Transgenic Maize in the EU-15. Pedobiologia 51(3):261-269
  7. ^ "EFSA promotes public access to data in transparency initiative" (Press release). European Food Safety Authority. January 14, 2013. 
  8. ^ Broderick, Nichole A.; Kenneth F. Raffa and Jo Handelsman (27). "Midgut bacteria required for Bacillus thuringiensis insecticidal activity". Proceedings of the National Academy of Sciences of the United States of America 103 (41): 15196–15199. Retrieved 7 January 2013. 
  9. ^ Complacency on the farm (Report). Center for Science in the Public Interest. November 2009. http://cspinet.org/new/pdf/complacencyonthefarm.pdf.
  10. ^ J.F. Witkowski; J.L. Wedberg, K.L. Steffey, P.E., et al. (2002). Bt Corn & European Corn Borer: Long-Term Success Through Resistance Management (Report). University of Minnesota. http://www.extension.umn.edu/distribution/cropsystems/dc7055.html#ch11.
  11. ^ Chilcutt, Charles; Tabashnik, BE. (18). "Contamination of refuges by Bacillus thuringiensis toxin genes from transgenic maize.". Proceedings of the National Academy of Science of the United States of America 101 (20): 7526–7529. 
  12. ^ Opinion relating to the deposition of 15 December 2009 by the Member of Parliament, François Grosdidier, as to the conclusions of the study entitled “A comparison of the effects of three GM corn varieties on mammalian health” by J. Spiroux de Vendômois, F. Roullier, D. Cellier and G.E. Séralini, Int. J. Biol. Sci, 2009: 5(7) : 706-726. (Report). High Council of Biotechnologies Scientific Committee. http://www.food.gov.uk/multimedia/pdfs/acnfp9612a2.
  13. ^ EFSA Minutes of the 55th Plenary Meeting of the Scientific Panel on Genetically Mofified Organisms Held on 27-28 January 2010 IN Parma, Italy, Annex 1, Vendemois et al 2009 European Food Safety Authority report, Retrieved 27 July 2012
  14. ^ Doull, J.; D. Gaylor, H.A. Greim, D.P. Lovell, B. Lynch, I.C. Munro (November 2007). "Report of an Expert Panel on the reanalysis by of a 90-day study conducted by Monsanto in support of the safety of a genetically modified corn variety (MON 863)." (PDF). Food and Chemical Toxicology 45 (11): 2073–2085. doi:10.1016/j.fct.2007.08.033. PMID 17900781. Retrieved 2012-07-27. "The Se´ralini et al. reanalysis does not advance any new scientific data to indicate that MON 863 caused adverse effects in the 90-day rat study." 
  15. ^ Aris A, Leblanc S (May 2011). "Maternal and fetal exposure to pesticides associated to genetically modified foods in Eastern Townships of Quebec, Canada". Reprod. Toxicol. 31 (4): 528–33. doi:10.1016/j.reprotox.2011.02.004. PMID 21338670. 
  16. ^ Alain de Weck: Une protéine pesticide OGM (Cry1ab) dans le sang de femmes gravides et de leur fœtus? Un travail bâclé et un scénario catastrophe très probablement inexistant
  17. ^ "Many Women, no Cry - OGM : environnement, santé et politique" (in English and French). Marcel-kuntz-ogm.over-blog.fr. 2012-01-16. Retrieved 2012-02-07. 
  18. ^ "FSANZ response to study linking Cry1Ab protein in blood to GM foods - Food Standards Australia New Zealand". foodstandards.gov.au. 2011-05-27. Retrieved 2012-02-07. 
  19. ^ Buzoianu, S. G.; Walsh, M. C.; Rea, M. C.; O'Donovan, O.; Gelencsér, E.; Ujhelyi, G.; Szabó, E.; Nagy, A. et al. (2012). "Effects of Feeding Bt Maize to Sows during Gestation and Lactation on Maternal and Offspring Immunity and Fate of Transgenic Material". In Bravo, Alejandra. PLoS ONE 7 (10): e47851. doi:10.1371/journal.pone.0047851. PMC 3473024. PMID 23091650. 
  20. ^ King D, Gordon A. Contaminant found in Taco Bell taco shells. Food safety coalition demands recall (press release), vol 2001. Washington, DC: Friends of the Earth, 2000. Available: http://www.foe.org/act/getacobellpr.html. 3 November 2001.
  21. ^ Agricultural Biotechnology: Updated Benefit Estimates, Janet E. Carpenter and Leonard P. Gianessi 2001, National Center for Food and Agricultural Policy
  22. ^ CDC, National Center for Environmental Health. Investigation of Human Health Effects Associated with Potential Exposure to Genetically Modified Corn: A Report to the U.S. Food and Drug Administration from the Centers for Disease Control and Prevention. Atlanta,GA:Centers for Disease Control and Prevention, 2001.
  23. ^ FIFRA Scientific Advisory Panel Report No. 2001-09, July 2001 http://www.epa.gov/scipoly/SAP/meetings/2001/july/julyfinal.pdf
  24. ^ "Starlink Corn Regulatory Information". Environmental Protection Agency (EPA). April 2008. 
  25. ^ Shepherd DN, Mangwende T, Martin DP, et al. (November 2007). "Maize streak virus-resistant transgenic maize: a first for Africa". Plant Biotechnol. J. 5 (6): 759–67. doi:10.1111/j.1467-7652.2007.00279.x. PMID 17924935. 

Further reading[edit]

External links[edit]

News[edit]
Genetically
modified
organisms
Maize
Other
Processes
Types
Uses
In agriculture
In humans and
diagnostics
In research
Related
articles
Regulation
Similar fields
Retrieved from "http://en.wikipedia.org/w/index.php?title=Genetically_modified_maize&oldid=560313224"