Risks of Cross Pollination by GMO Potatoes

Note: This article is focused on the USA because that is where I live.  I know less about the status of GMO potatoes in other countries, although I am under the impression that they are rare outside of the USA, Canada, and China (PRC).  If you know more about the status of GMO potatoes in your country, you are welcome to comment below.

People write fairly often to ask me what the chances are that their potatoes will be contaminated by pollen from GMO potato varieties.  Until 2015, this was a pretty easy question to answer, since there weren’t any GMO potato varieties on the market.  Since then, Simplot has introduced several varieties, which are genetically modified versions of common non-GMO potatoes.  The modified varieties are Atlantic, Ranger Russet, and Russet Burbank.  It seems safe to assume that there will be more altered varieties in the future.  Russet Burbank is male sterile, which is good news, since it cannot pollinate anything.  Unfortunately, Atlantic and Ranger Russet are male fertile, so they do have the capability to pollinate other varieties.  It is unfortunate that, with a majority of male sterile potatoes from which they could have chosen, Simplot chose to build some of their GMOs on fully fertile varieties.  They could have saved people a lot of wondering by sticking to sterile varieties.

As with most GMO varieties, these potatoes are grown pretty much exclusively by commercial growers on large acreage.  These are commodity potatoes, the sort used overwhelmingly to make processed foods.  This is another place where Simplot could have helped us by limiting the use of their potatoes to only the processed potato market.  Unfortunately, some are also grown for fresh use, which means the kind of potatoes that you can buy in a bag at the grocery store.  The potatoes for fresh use are reportly trademarked as “White Russet,” but I can’t say whether this labeling is apparent or universal.  In North America, there is no labeling requirement for GMO potatoes, which means that they could be sold without any label at all.

So, we know that there are two varieties of genetically modified potatoes that produce viable pollen and, therefore, could pollinate non-GMO potatoes, introducing the GMO traits.  Does anyone need to worry about this?  The answer, for most people, is still no.  If you only grow potatoes from tubers, which are clones, cross pollination will not alter the potatoes in any way.  Uncertainties start to creep in when you grow potatoes from true seeds (i.e. the seeds that form inside potato berries).  Very few people grow potatoes from TPS, but many of the people who read this web site do.  For there to be any risk of cross pollination in the true potato seeds that you collect, there are a few things that have to happen together:

  1. Someone must be growing a GMO potato within pollinator range
  2. The GMO potato must be male fertile
  3. Your potatoes and the GMO potatoes must be in flower at the same time

The first consideration, GMO potatoes growing within pollinator range, will exclude most people from needing to worry about this.  Almost all GMO potatoes are grown by commodity potato farmers, on large acreages in potato country.  If you are surrounded by hundreds of acres of potato fields, you might have something to worry about.  If you live outside the major potato production areas, then your odds of catching any GMO pollen are vanishingly small.  The only risk outside of potato country is that one of your neighbors decides to grow potatoes purchased at the grocery store and they happen to pick up a bag of GMO potatoes.  There is now a possibility that their plants could pollinate yours and introduce the GMO traits.  For this to happen, their plants would need to be growing within about 550 yards of your plants.  Bumblebees are the major pollinator of potatoes and they do the vast majority of their foraging within a radius of 550 yards of the nest.  So, someone would need to be growing a GMO variety pretty close to you.  They would also need to be in flower at the same time and commercial varieties tend to flower briefly and poorly, which further reduces the odds.  When you combine these factors, the odds that you will experience contamination by GMO pollen are really low, but they aren’t zero.  Unfortunately, zero probability no longer exists since 2015.

Pollinators mostly operate at short distances, so your garden is the most likely source of any pollen that lands on your plants, unless you can literally look into your neighbor’s yard and see potato plants.  Since your garden is the most likely source of pollen, the most effective thing that you can do is to avoid growing potatoes of unknown provenance.  That means no potatoes from the grocery store, your friend’s garden, the farmer’s market, or a box from the food bank.  Start with seed potatoes of known varieties.  If you do that, there is no chance of unknowingly introducing GMO potatoes to your garden.  You can also reduce the odds of cross pollination by only growing male fertile potatoes in your garden.  Because male fertile potatoes overwhelmingly self pollinate, there is less opportunity for foreign pollen to successfully pollinate them.  If you know that you have exposure to GMO potato pollen, the last resort is manual pollination.  You can make sure that your seed is uncontaminated by bagging your flowers before they open, pollinating them by hand, and then keeping them bagged until the berries begin to develop.  This excludes any possibility of unwanted pollination.

What about true potato seeds that you buy or trade for?  I think that the odds that any seeds will be contaminated with GMO genetics are really, really small.  But, the farther away the source is from commodity potato country, the better the odds against contamination.  If you are really, really concerned about the possibility of contamination, you might want to avoid TPS produced in the major potato growing states: Idaho, Washington, Wisconsin, Oregon, North Dakota, Colorado, Minnesota, Michigan, California, or Maine.  The problem is, if you exclude those states entirely, you have excluded most of the states where it is possible to produce TPS reliably.  Also, potato growing tends to be highly localized.  For example, I live in Washington, but there is about a 100 mile straight line distance between where I grow and the nearest commodity potato farming areas in this state.  There is no chance of pollination across that distance and you will find similar gaps in every state, except maybe Idaho.

Compared to a crop like corn, which is wind pollinated and of which the acreage planted is overwhelmingly genetically modified, the risk of contamination with GMO pollen in potatoes is very low and restricted to people who grow from TPS.  But, it is worth considering that GMO corn was once new and only grown in a few places.  I think that we can safely expect the number of GMO potato varieties and the acreage on which they are grown to increase over time.  There may come a time when small potato breeders will need to pay close attention to what their neighbors are growing and adapt their practices accordingly.

In this article, I have chosen not to spend a lot of time discussing whether or not GMO potato traits are worth worrying about. I have learned that my opinion on the subject angers almost everyone on both “sides” of the debate about GMOs and is not likely to change anyone’s mind.  If GMO contamination is important to you, I’m not going to try to talk you out of it or vice-versa.  The matter has a lot of complexities, both biochemically and legally, and I think you can argue successfully for just about any position as long as you do so in good faith.

4 thoughts on “Risks of Cross Pollination by GMO Potatoes

  1. Neil says:

    I assume that all the varieties discussed are tetraploid. If a person stuck to just growing diploid potatoes from true seed, could that virtually eliminate the concern of gmo contamination?

    • bill says:

      Hi Neil. It would dramatically reduce the possibility. It is possible for diploids to be pollinated by tetraploids when they produce unreduced ovules, but that’s pretty rare and we are already talking about a low probability for cross pollination. Several of the big potato breeders are working on switching to diploid breeding and releasing new diploid varieties and probably every single one of those will be derived at least from parents that were genetically modified. So, the future could be more complicated.

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