3.9—Disease-resistant crops do not cause human diseases


Disease-resistant crops do not cause human diseases

See Genetic Roulette’s False Claims at Bottom of Page

Analysis of Peer-Reviewed Research:

Speculation is not science.  Science is about evidence.  Disease-protected crops are thoroughly evaluated for safety before they enter the market.  Advancing arguments against GM crops that are based on speculation that is unsupported by evidence or proof can lead to scary predictions.  Genetic Roulette incorrectly asserts that people will be exposed to more viral components through GM crops than through virus-infected crops.  This is simply not true and arguments based on this assertion cannot be supported.  Food safety experts believe that disease-protected crops are as safe as, or are safer than, conventional crops.

1. While most disease-protected crops do not produce viral proteins, in cases where they do, the safety of the protein has been established. Perhaps the best example is genetically-engineered papaya developed for farming in Hawaii.  This papaya is protected against a plant virus (Papaya ringspot virus, PRV) that was devastating the Hawaiian papaya industry before the availability of disease-protected trees that reject virus infection.  Reassuringly, we know that exposure of humans to the PRV proteins is safe because the virus is widespread and many people over many decades have eaten papaya containing PRV without ill effect. Mild variants of PRV have even been deliberately used to protect papaya against more damaging viruses, and such virus-infected fruits also have been eaten without ill effect. Similar live virus protection of citrus fruits is used in Brazil without any harm to humans. A colorful and readable history of the two decades of safe use of virus-resistant transgenic plants has been written by two developers of virus-resistant transgenic papaya, Marc Fuchs and Dennis Gonsalves (Fuchs and Gonsalves 2007). They mention how, starting 1992, the United States Department of Agriculture initiated a comprehensive and  ongoing research program of the risk assessment of transgenic plants which supported numerous safety studies on virus-resistant transgenic plants. Rigorous scientific debate and research underpin the safety assessment of virus resistant food crops.

2.  The exposure to viral proteins in disease-protected transgenic crops is many-fold lower than the exposure to viral proteins caused by eating virus-infected vegetables and fruits. Smith simply has this wrong, moreover, he presents absolutely no evidence or studies.  He supports his arguments with quotes from well-known opponents of biotechnology—but quotes without evidence are meaningless since science is based on fact and observation.  Virus infected plants can have enormously high levels of many different viral proteins.  These proteins could theoretically be harmful to human cells if they were produced inside our cells, but in the diet they are treated as proteins.  Virtually every meal that we eat which contains plant material has plant viral proteins.  These are non-toxic to humans (Fuchs and others 1998, Fuchs and Gonsalves 2007, Gonsalves 1998, Hardwick and others 1994, Hoekema and others 1989, Lawson  and others 1990, Ling and others 1991).

3.  No plant virus has ever caused any disease or known adverse effect in humans! Genetic Roulette speculates about potential harm that could come from plant viruses or components isolated from them.  There is simply no scientific reason to believe that disease-protected crops will be harmful.  They expose us to fewer viral nucleic acids and proteins than would otherwise have been the case.  They are assessed for safety prior to regulatory approval.  They have been used in agriculture for decades with no reports of adverse effects (Fuchs and Gonsalves  2007).

See also: 5.9—Plant genes don’t move to gut microbes

References: Fuchs M, Tricoli DM, Carney KJ, Schesser M, McFerson JR and Gonsalves D (1998). Comparative virus resistance and fruit yield of transgenic squash with single and multiple coat protein genes. Plant Dis. 82:1350-1356.

Fuchs M and Gonsalves D (2007). Safety of virus-resistant transgenic plants two decades after their introduction: Lessons from realistic field risk assessment studies. Annu. Rev. Phytopathol. 2007. 45:173–202

Gonsalves D (1998). Control of Papaya Ringspot Virus in papaya: a case study. Annu. Rev. Phytopathol. 1998. 36:415–37. “measured amounts of coat protein in transgenic plants were much lower than those of infected plants”.

Hardwick NV, Davies JML and Wright DM (1994). The incidence of three virus diseases of winter oilseed rape in England and Wales in the 1991/02 and 1992/93 growing season. Plant Pathol. 43:1045–49. Cauliflower mosaic virus is as common as cabbage.

Hoekema A, Huisman MJ, Molendrijk L, van den Elzen PJ and Cornelissen BJC (1989). The genetic engineering of two commercial potato cultivars for resistance to potota virus X. Bio/technology 7:273-278. Transgenic potatoes has less viral protein than do infected potatoes.

Lawson C, Kaniewski W, Haley L, Rozman R, Newell C, Sanders P and Tumer NE. (1990). Engineering resistance to mixed virus infection in a commercial potato cultivar: resistance to potato virus X and potato virus Y in transgenic Russet Burbank. Biotechnology (N Y). 8(2):127-34. Infected potato has muh more virus coat protein than do transgenic potatoes.

Ling KS, Namba S, Gonsalves C, Slightom JL, and Gonsalves D (1991). Protection against detrimental effects of potyvirus infection in transgenic tobacco plants expressing the papaya ringspot virus coat protein gene. Biotechnology. 9(8):752-8.

Genetic Roulette Falsely Claims: Disease-resistant crops may promote human viruses and other diseases
  1. Viral Genes inserted into disease-resistant crops produce viral proteins.
  2. Consuming the may suppress the body’s defense against viral infections, particularly in the gut.
  3. These proteins may be toxic and lead to disease.
  4. Viral transgens produce RNA that might influence gene expression in unpredicted ways.

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