How Many Foods Are Genetically Engineered?Response:
Estimates suggest that as much as 80% of U.S. processed food may contain an ingredient from aGE crop, such as corn starch, highfructose corn syrup, corn oil, canola oil, soybean oil, soy flour, soy lecithin, or cottonseed oil (1). Despite this percentage in processed foods, there are very few commercially available whole GE foods. The first commercial GE whole food was the FlavrSavrTM tomato, engineered to have a longer shelf life (2) so tomatoes could be kept on the vine longer to ripen, develop more flavor, and allow later shipments to stores. Although grown in California, the tomatoes were made into tomato paste, clearly labeled, and sold in the U.K. The paste gained an estimated 60% share of the canned tomato market by 1999, but left the market shortly thereafter owing to market concerns (3). Endless SummerTM tomatoes, also engineered to control ripening and introduced at approximately the same time, were commercially available for only a short time.
GE papaya is the only engineered fruit commercially available in the U.S. today. This occurred because in Hawaii, where most papayas for the U.S. are grown, production fell owing to losses to papaya ringspot virus, PRSV (4). PRSV, discovered in Hawaii in the 1940s, virtually eliminated large-scale production on Oahu in the 1950s, forcing the industry to relocate in the early 1960s to the island of Hawaii. There it thrived, which led to 95% of Hawaii’s papaya being produced there by the 1980s. Delay in spread of the disease gave researchers time to look at possibilities to protect against the virus. Infecting papaya with milder virus strains (5) met with limited success owing to a more aggressive PRSV, but a GE papaya containing a viral coat protein gene was successful (6, 7). In 2006 the GE varieties “Rainbow” and “SunUp” accounted for >50% of papaya production in Hawaii, although much of the papaya consumed in the U.S. is from Brazil, Mexico, and the Caribbean, where PRSV is not a serious problem.
Another commercial whole food available in the U.S. is GE squash (yellow crookneck, straightneck, and zucchini). The first variety of GE yellow squash, termed Freedom II, was the second GE crop to be cleared by U.S. regulators. Freedom II was engineered with viral coat protein genes to be resistant to two viruses—Watermelon Mosaic Virus 2 (WMV2) and Zucchini Yellow Mosaic Virus (ZYMV) (8). Freedom II reached the market in 1995 but was not labeled like the FlavrSavrTM tomato. Viral resistance was transferred to zucchini by breeding and, because squash is usually infected with a third virus, Cucumber Mosaic Virus (CMV), a GE squash resistant to all three viruses was developed. Six varieties of GE yellow squash and zucchini, bearing various names, e.g., Independence II, Liberator III, Freedom III, and Destiny III, are currently being sold. U.S. acreage is limited in part because of the negative effects of other viruses against which the GE varieties are not protected, but resistance to the original three viruses remains strong (9).
The last whole GE food available in the U.S. is GE sweet corn, engineered with a Bt gene to protect against earworms (Helicoverpa zea), one of the most costly crop pests in North America. Earworm damage results in subsequent fungal and bacterial attack and quality loss (10). Expressing Bt in corn results in reductions in insect attack. By reducing insect damage, mycotoxigenic fungi numbers are decreased and this results in lower levels of mycotoxins, such as fumonisins, which have toxic effects on humans such as elevated rates of liver and/or esophageal cancer (11). Comparing fumonisin levels in corn from Bt hybrids versus control hybrids, Bt hybrids give higher percentages of grain suitable for human and animal use (12).
1. Hallman WK, Hebden WC, Aquino HL, Cutie CL, Lang JT. 2003. Public Perceptions of Genetically Modified Foods: A National Study of American Knowledge and Opinion. Food Policy Inst. Publ. RR-1003-004. New Brunswick, NJ: Rutgers Univ.
2. Kramer MG, Redenbaugh K. 1994. Commercialization of a tomato with an antisense polygalacturonase gene—the Flavr SavrTM story. Euphytica 9:293–97
3. Martineau B. 2001. First Fruit: The Creation of the Flavr Savr Tomato and the Birth of Biotech Foods. New York: McGraw-Hill
4. Gonsalves D, Ferriera S, Manshardt R, Fitch M, Slightom J. 2000. Transgenic virus resistant Papaya: New hope for controlling Papaya RingspotVirus in Hawaii. Plant Health Progress. (plant Health Reviews), 21 June
5. Sheen TF, Wang HL, Wang DN. 1998. Control of papaya ringspot virus by cross protection and cultivation techniques. J. Jpn. Soc. Horticult. Sci. 67:1232–35
6. Gonsalves D. 1998. Control of papaya ringspot virus in papaya: A case study. Annu. Rev. Phytopathol. 36:165–205
7. Lius S, Manshardt RM, Fitch MMM, Slightom JL, Sanford JC, Gonsalves D. 1997. Pathogen-derived resistance provides papaya with effective protection against papaya ringspot virus. Mol. Breed. 3:161–68
8. TricoliDM,Carney KJ, Russell PF, McMaster JR, GroffDW,et al. 1995. Field evaluation of transgenic squash containing single or multiple virus coat protein gene constructs for resistance to cucumber mosaic virus, watermelon mosaic virus 2 and zucchini yellow mosaic virus. Bio/Technology 13:1458–65
9. Gaba V, Zelcer A, Gal-On A. 2004. Cucurbit biotechnology—the importance of virus resistance. In Vitro Cell. Dev. Biol. Plant 40:346–58
10. Horvath Z. 2003. Damage in corn production and in hybrid multiplication caused by species of Coleoptera. Cereal Res. Commun. 31:421–27
11. Van derWesthuizen L, Shephard GS, Scussel VM, Costa LLF, Vismer HF, et al. 2003. Fumonisin contamination and Fusarium incidence in corn from Santa Carina, Brazil. J. Agric. Food Chem. 51:5574–78
12. Hammond BG, Campbell KW, Pilcher CD, Degooyer TA, Robinson AE, et al. 2004. Lower fumonisin mycotoxin levels in the grain of Bt-corn grown in the United States in 2000–2002. J. Agric. Food Chem. 52:1390–97