Are you growing, buying, or eating "GMO" sweet potatoes? How would you know?
Over the past few decades, advances in the field of genetic engineering have occurred alongside increasing public awareness of, and a variety of reactions to, the presence of genetically engineered crops and ingredients in our food systems.
If you’re someone who grows or sells sweet potatoes, some of your customers might be asking, “Are these sweet potatoes GMO?” Even if you’re just someone who buys and eats sweet potatoes, you might be asking this question too.
Before this question can be answered, however, a few terms need to be cleared up.
What does "GMO" mean, anyway?
Many people are familiar with the popular acronym “GMO”, which stands for “genetically modified organism.” The more scientifically accurate term is “genetically engineered organism.”
This term refers to any organism (such as a plant or animal) whose genome (DNA) has been altered through the use of genetic engineering techniques, in which an undesired gene is removed, or a desired gene is isolated, copied, or synthesized, before it is prepared and then inserted into the host genome. In plants, the most common techniques for inserting a gene are:
- Agrobacterium-mediated recombination (using a type of bacteria known for its ability to transfer DNA between itself and plants)
- Biolistics, also known as microparticle bombardment (using a biolistic particle delivery system, also known as a “gene gun,” to insert DNA)
- Electroporation (applying an electrical field to cells, in order to increase the permeability of their cell membranes, so that DNA can be introduced into the cell)
Once a cell has been transformed by using one of these methods, a new plant is grown from that cell via tissue culture. Then, tests are performed to make sure the plant contains the DNA that was added to the original cell.
There are a few different types of genetically engineered organisms. Transgenic organisms have been modified to contain gene(s) obtained from an unrelated or sexually incompatible species. Cisgenic organisms contain gene(s) from another organism of the same species, or from a sexually compatible species.
So, what about sweet potatoes? Fascinatingly, researchers discovered that sweet potatoes already contain DNA sequences from Agrobacterium within their own genome. Not only that, but sweet potato plants actively express some of these genes. In light of this discovery, sweet potatoes serve as the first known example of a naturally transgenic food crop.
“Okay,” you might ask, “But have they been genetically modified by humans?” The answer, as you might expect by now, takes the form of a “Yes, but…”
How do we genetically alter sweet potatoes?
Like any cultivated crop, sweet potatoes have been genetically modified by humans over a very long period of time, through selective breeding, to produce improved varieties with desirable traits for flavor, texture, color, shape, pest and disease resistance, drought tolerance, and so on.
Different varieties are crossed with each other via cross-pollination. Next, the offspring of these new crosses are planted and grown in field trials, in which they are observed and tested for desirable traits. Additional tests (such as bake tests and fry tests) are conducted as well. Varieties which have potential for the market (or potential for crossing with other varieties) are kept for further research, with the ultimate goal of delivering impressive, new varieties that growers and producers will want to buy.
People have also been researching how sweet potatoes may be genetically engineered in the future, but the sweet potato varieties which are commercially available today (at least in the United States) are not the product of such technology.
To answer the original the question: yes, sweet potatoes are “GMOs” – or “transgenic,” to be more precise. But at least in this case, humans can’t take all the credit.
Edmisten, K. “What Is the Difference Between Genetically Modified Organisms and Genetically Engineered Organisms?” North Carolina Cooperative Extension. Web. Accessed 22 December 2018 at agbiotech.ces.ncsu.edu.
Kyndt, T., Quispe, D., Zhai, H., Jarret, R., Ghislain, M., Liu, Q., Gheysen, G. and Kreuze, J. “Sweet Potato: A Naturally Transgenic Food Crop.” Proceedings of the National Academy of Sciences 112 (18) 5844-5849. 2015. Web. Accessed 22 December 2018 at pnas.org.
National Research Council (US) Committee on Identifying and Assessing Unintended Effects of Genetically Engineered Foods on Human Health. “Methods and Mechanisms for Genetic Manipulation of Plants, Animals, and Microorganisms.” Safety of Genetically Engineered Foods: Approaches to Assessing Unintended Health Effects. 2004. Web. Accessed 22 December 2018 at ncbi.nlm.nih.gov.