Recently we were given a gift of sweet corn from somewhere warmer than central Virginia. It wasn’t Organic, so I wondered if it was genetically modified. I try to avoid eating GMOs, because I don’t support the practice of inserting bits of other organisms in existing crops. Corn varieties often have Bacillus thuriengensis (Bt) inserted in their DNA with the goal of killing caterpillars that eat corn kernels.
Anything certified USDA Organic is not allowed to have any GMOs in it, so that’s one way to avoid getting GMOs. Growing your own food is a certain way to avoid GMOs, if you don’t buy GMO varieties or suffer cross-pollination from GMO crops.
The Non-GMO Project is the U.S. organization that provides testing and labeling for absence or presence of GMO in products. The “Non-GMO Project Seal” certifies that the product contains 0.9% or less GMO ingredients.
I’m going to skip ahead to talking about which vegetable crops are available in genetically modified varieties, because there are not many, and I’m not interested in worrying people! Then I’ll go into details.
The Big Three GMO Crops in the US
Soy, canola and corn are the three food crops in the US that are most likely to be genetically modified. Starting with corn (maize): 92% of all corn grown in the US is GMO. Of corn grown, only 1% is sweet corn. Of sweet corn grown in 2018, 10% is GMO. When you see a field of corn, it is almost certainly GMO, unless you are looking at an Organic farm.
What is field corn? “Corn (such as dent corn or flint corn) with starchy kernels that are used especially as livestock feed or processed into food products (such as cornmeal, corn oil, and corn syrup) or ethanol,” (Merriam Webster). Of the field corn in the US, 40% goes to make ethanol for vehicle fuels, 40% goes to livestock feed, and 20% goes into processed foods for humans.
In 2000, GM StarLink corn was recalled, when over 300 different food products were found to contain a genetically modified corn that had not been approved for human consumption (only animal feed). It was the first recall of a genetically modified food.
What about wheat? Farmers have shown a distinct preference for not growing GMO wheat. This is because much of the wheat grown in the US is for export, and people in many other countries refuse to eat GMOs.
Which Other Vegetables Might be GM?
Here is a 2013 article published in the Journal of Food Science and Technology. “Genetically modified foods: safety, risks and public concerns—a review” by A. S. Bawa and K. R. Anilakumar
There are only a few vegetables that have any GMO varieties. Some have been tried and failed. All vegetable seed is non-GMO unless labeled, and when purchasing GMO seed, you have to sign waivers. When searching on line, try various labels: genetically modified, GM, genetically engineered, GE, transgenic.
Summer Squash and Zucchini
To avoid zucchini yellow mosaic virus and watermelon mottle virus in summer squash and zucchini, GM varieties were created, starting in 1995. When I researched GM squash varieties in July 2017 for an article I wrote, I found mention of ten summer squash and zucchini, but now there seem to be fewer. On the Bayer/Seminis website for their squash varieties, in 2017, these all helpfully had a “B” icon (Biotech). The names sound like B-movies: Conqueror III, Destiny III, Liberator III, Patriot II, Prelude II, XPT1832 III yellow squash and Judgement III, Justice III, SV0474YG, SV6009YG zucchini. The website has been updated, as have the variety offerings, and they are less prominently labeled. ZW-20 virus-resistant yellow crookneck squash is a current transgenic line.
In 2005, about 13% of the zucchini grown in the USA was genetically modified to resist three viruses; the zucchini is also grown in Canada (Johnson 2008).
Mexican researchers in 2004 wrote a paper Assessing the risk of releasing transgenic Cucurbita spp. in Mexico. Localities with native wild relatives of transgenic squash were at risk of the greatest trouble from cross pollination. The genetic legacy of ancient squash lineages was at risk. Gene flow between crops and their wild relatives was widely documented. The authors urged much caution about where and when GMO squash should be permitted.
GM squash also poses a risk that its virus genes or the proteins they produce could interact with other viruses to produce new diseases. And, as with any genetically engineered crop, the squash poses the risk that its new genes might cause it to spread and become difficult to control.
The USA extracts 90 % of its sugar “needs” from US-grown sugar beet and sugarcane. Of the domestically grown sugar, half comes from sugar beet, and half from sugarcane. After deregulation in 2005, sugar beet resistant to glyphosate (RoundUp) was extensively adopted in the USA. 95% of sugar beets grown in the US are GM. The sugar produced from GM sugar beets is highly refined and contains no DNA or protein—it is just sucrose. In 2008, the Animal and Plant Health Inspection Service (APHIS), a division of the USDA, performed a court-ordered environmental review of the modified seed and announced that there was no risk to other crops such as beets (beetroot) for fresh eating and pickling, or related crops such as Swiss chard.
Since 2010, at least 80% of papayas grown in Hawaii are GM, to get around the devastating problem of papaya ringspot virus.
The ‘Flavr Savr’ Tomato
Consumers in the northern regions of the U.S. rely on tomatoes shipped in from the South if they want fresh tomatoes beyond the summer. To survive shipping, tomatoes are picked at the “mature-green” stage. They have already absorbed all the vitamins and nutrients from the plant that they can, but have not started to ripen. To ripen the green tomatoes, they spend 3 to 4 days in rooms where ethylene gas is released, and are then shipped at temperatures not lower than 50 degrees, to preserve what flavor they have. These tomatoes are probably still a few days away from being ripe.
Calgene, a biotechnology company, developed a tomato with a gene that slows the softening process that happens with ripening. Pectin gives tomatoes their firmness. The pectin in ripening tomatoes becomes naturally degraded by an enzyme and the fruits soften, making them difficult to ship.
The scientists “reversed” the tomato softening gene and reintroduced it into the plants. Reducing that enzyme in tomatoes slows cell wall breakdown and keeps the fruit firmer for longer. In order to tell if their “Flavr Savr” gene was successfully inside the plants, scientists attached a gene that makes plants resistant to the antibiotic kanamycin. By exposing the plants to kanamycin, they could tell which plants had accepted the Flavr Savr gene. Once in a tomato plant, the Flavr Savr gene attaches itself to the gene activating the softening enzyme. When the Flavr Savr gene is there, the “softening” gene cannot give the necessary signals to produce the enzyme that destroys pectin.
Production of the Flavr Savr stopped in 1997. Production costs were too high, and consumers did not find a benefit. See Whatever Happened to the Flavr Savr Genetically-Engineered Tomato
NewLeaf (and other GM) Potatoes
The NewLeaf GM potato was brought to market by Monsanto in the late 1990s. It was developed incorporating Bacillus thuringiensis (Bt) bacteria to kill Colorado potato beetles. The target audience of fast food retailers rejected it and food processors ran into export problems. It was withdrawn from the market in 2001.
In 1998, a safety study (Ewen and Pusztai 1999) of GM potatoes with incorporated snowdrop bulb lectin (GNA) gene (Lectin acts as an insecticide), showed significant changes in the intestines of rats fed GM potatoes. The tested potatoes were not a commercial variety and not intended for human consumption, but the public were alarmed.
In 2010 Amflora was developed by BASF Plant Science for production of pure amylopectin starch for manufacturing waxy potato starch. It was approved for industrial use in the European Union in 2010, but was withdrawn in January 2012 due to rejection by farmers and consumers.
In 2011, BASF requested approval for its Fortuna potato as feed and food. The potato was made resistant to late blight by adding resistant genes that originate in the Mexican wild potato Solanum bulbocastanum. In February 2013, BASF withdrew its application.
In 2014, the USDA approved a GM potato type, Innate, developed by the J. R. Simplot Company that contained 10 genetic modifications that prevent bruising and produce less (carcinogenic) acrylamide when fried. The modification uses RNA interference (deactivating genes already present), rather than introducing genetic material from other plants or animals. Ranger Russet, Russet Burbank, and Atlantic potatoes are examples of varieties using this technology. McDonald’s announced that they have ruled out using Innate.
In 2017 scientists in Bangladesh developed a GM variety of potato resistant to late blight.
In February 2015 Arctic Apples became the first GM apple approved for sale in the US. RNA interference is used to reduce the activity of polyphenol oxidase, preventing the fruit from browning.
In April 2016, a white button mushroom (Agaricus bisporus), genetically modified using the CRISPR technique, received the go-ahead, as the USDA considers it exempt because the editing process did not involve the introduction of foreign DNA, just deletion from a gene coding for an enzyme that causes browning, reducing the level of that enzyme by 30%.
The Problems with GMOs
When GM varieties are planted on a commercial scale, resistant weeds and pests can evolve. The emergence of resistant insects can negate the effects of a Bt GMO. Also, if herbicide spraying becomes more frequent on herbicide-tolerant GMO varieties, weeds can develop resistance to the herbicide. This can cause an increase in herbicide use or an increase in the amount and types of herbicides used on crop plants. It is not a coincidence that herbicide producers are behind this research.
Further investigation is needed to learn if residues from herbicide- or pest-resistant plants could harm soil organisms. Another uncertainty is whether the pest-resistance of GE crops can cross to related weeds, creating resistant weeds. Possibly insect-resistant plants can cause increased death rates to one specific pest, decreasing competition and allowing previously minor pests to become a major problem. Also, it could cause the pests to move to another plant that had been unthreatened. A study of Bt crops showed that beneficial insects are also exposed to harmful quantities of Bt. It is possible for the effects to reach further up the food chain to affect crops and animals eaten by humans.
It is possible that virus-resistance can lead to new viruses and new diseases emerging. Naturally occurring viruses can recombine with viral fragments, forming new viruses.
The main concerns about adverse effects of GM foods on human health are the transfer of antibiotic resistance, toxicity and abnormal immune responses. A known allergen may transfer from a GM crop into a non-allergenic crop and create a new allergen. Patients allergic to Brazil nuts and not to soybeans showed an allergic response towards GM soybeans.
A Law on our Side
In January 2022 the National Bioengineered Food Disclosure Standard became mandatory. The new Standard requires food manufacturers, importers, and other entities that label foods for retail sale to disclose information about BE food and BE food ingredients. This rule is intended to provide a uniform national standard for providing information to consumers about the BE status of foods. The Final Rule was published in December 2018
The BE Food Disclosure must be placed on either the main information panel on the label, or an alternate panel “likely to be seen by a consumer under ordinary shopping conditions.” For bulk foods, retailers are responsible for displaying the BE food disclosure on or near the bulk item. Now you know what to look for!