Stopping Potato Greening


[deck]A cure may be in the works for sunburned potatoes — which is music to the industry’s ears.[/deck]

Prince Edward Island research scientist Bourlaye Fofana is confident that potato greening could become be a thing of the past. Research began last year at Agriculture and Agri-Food Canada’s Crops and Livestock Research Centre in Charlottetown, P.E.I., to create a potato that will not turn green when exposed to light.

Fofana’s research team, which includes a breeder, pathologists and chemists based in New Brunswick, Alberta and P.E.I., are working on a solution to potato greening and associated toxicity that they believe lies in potato genetics. New genetic tools available in the lab allow researchers to go through thousands of potato seeds to find the genetics they need to bypass toxic compounds that are highest with potato greening and which will help accelerate the breeding process of new potato lines.

Fofana’s team has chemically treated true seed harvested from potato fruits, which look like a tomato fruit. They are currently growing 2,500 lines of potatoes in a greenhouse in Charlottetown, expecting to produce a non-greening, non-toxic potato. The initial target was 10,000 lines, but “I am getting confident we will have most of our outcome from the first batch,” says Fofana.


While too much sunlight can result in sunburned potatoes, artificial light in grocery stores can also cause greening.

He adds that because the program is based on selective breeding and does not involve genetic modification, the resulting potato tubers could be grown anywhere in the world, and therefore likely wouldn’t face restrictions from GMO-free countries. “[Our goal is simply] to generate a germplasm for breeders, and the breeder will be looking at that for development and what qualities they want in the tuber,” says Fofana.

Greening has always been a problem for the potato industry, and according to P.E.I. Potato Board General Manager Greg Donald, is responsible for both losses in the field and also consumer complaints at the retail level. The board represents the Island’s 330 or so potato growers, and lobbies government on their behalf. It also communicates directly with consumers as part of its extensive marketing efforts.

“It’s not a secret in the industry that consumption of fresh potatoes has been on the decline quite significantly. The figures in Canada show the per capita consumption of fresh potatoes has decreased 48 per cent in the last 15 years. I’m not going to say that greening is the reason, but I would say it’s a contributing factor,” says Donald. “We take very seriously all feedback we get from consumers. We have a consumer response line that we manage, and greening is one of the more common concerns for people calling. The majority of the time, that greening occurs on the store shelf. It’s not from the [field].”

Effect of Artificial Light

Greening can occur on the store shelf when potatoes are exposed to artificial light. It’s becoming even more of a problem in the 21st century, Donald notes. “Grocery stores are now open 24/7. So there’s artificial lighting in all the time, and the potatoes are further subject to it there.”

But greening also occurs in the field when potatoes are exposed to sunlight, often referred to as “potato sunburn.” Donald notes that producers do everything they can to prevent sunburn, but some green potatoes always get through. “They do the best they can to have a good hill formed and carry out other practices to reduce sunburn in the field, including tarping their loads during transportation, but despite their best efforts, there are still losses,” he says.

Fofana’s seeds have been treated with ethyl methanesulfonate, a compound that produces random mutations in genetic material. He expects to pinpoint about 100 candidates for the breeding program that will be free of compounds known as glycoalkaloids, which occur naturally in potatoes but at higher levels in greening potatoes.

Green-skinned potatoes in the lab at Agriculture and Agri-Food Canada’s Crops and Livestock Research Centre in P.E.I.

The glycoalkaloids can cause bitterness, and can also have a toxic effect in high doses, although actual cases of glycoalkaloid toxicity in humans as a result of potato consumption are virtually unheard of. Fofana says glycoalkaloids, if consumed in high doses over a long period of time, could have a cumulative effect on the body. According to its website, Health Canada has established a maximum level of 20 milligrams of glycoalkaloids per 100 grams (fresh weight) of potato tuber. This maximum level is applicable to all potatoes that are commercially sold in Canada, the website states.

Concerns about toxicity aside, greening is primarily a flavour and aesthetic defect in potatoes, the severity of which fluctuates widely depending on the variety of potato and growing and storage conditions. It’s not just an issue in P.E.I. and Canada, but internationally as well, adds Donald.

“I would speculate on the production side of things, it’s probably not unreasonable to say at least two per cent or so [of the total P.E.I. potato crop] is being lost every year, or culled if you will, due to sunburn,” he says. After you consider all the growers in Canada at large, it really adds up, Donald goes on to say. “After that, you see losses on the retail end of things. If a potato is in a package and is exposed to light in the store, there’s a potential for loss all along the process. Generally speaking, right from field to fork, there are challenges with greening.”

A non-greening potato would give Canadian potato farmers a new marketing edge, says Donald. “If they can eliminate that problem, then their saleable product is going to increase.”

That’s music to Darryl Wallace’s ears. He’s an Island potato grower and also sits on the P.E.I. Potato Board as a director. He grows about 500 acres of potatoes every year, and says he’d save at least two per cent of his crop each season if he could grow a potato variety that wasn’t susceptible to sunburn. Mother Nature largely determines how much of his annual crop he’ll have to cull due to greening caused by sun exposure.

“Sometimes you’ll get a great big rain in the spring that will wash some of your hills off, and then of course you’re going to get more sunburn,” says Wallace, who grows both processing and table potatoes. “It’s quite a concern in the table market, more than anything.”

Eliminating greening on store shelves will also make consumers happy, Donald says, and could help consumption of fresh potatoes to increase. “If [greening] can be removed as an issue or complaint from consumers, then that’s better for everybody,” he says.

Boon to Retailers

Eliminating greening at the store level would be a major boon to retailers, says Peter Chapman. He’s the owner of GPS Business Solutions, an independent consulting firm in Atlantic Canada focused on increasing produce sales for growers, food processors and retailers. Chapman has assisted with produce marketing for Loblaws stores on the East Coast, and says if greening is eliminated, potato retailers will be able to promote the vegetable to consumers in a whole new way.

“As [potato] consumption changes, we’ve seen people switch from a 10-pound bag to a smaller one, or even bulk,” says Chapman. “Some stores are great for selling bulk potatoes simply because they’re in the right marketplace. If you’re in downtown Toronto and people want to buy one potato, you can do it that way. But in a lot of stores, you really have to manage the size of the display for bulk potatoes. If we can prevent greening, that would be a big win on the retail side.”

Without having to worry about greening, retailers can commit themselves to far more attractive potato displays, he adds. “They can be a lot more confident that they’ll get a good shelf life out of it and give the consumer ample time to get in and buy it.” Chapman estimates that on the retail side, shrink on bulk potatoes is “significantly higher” than the two per cent loss that Donald estimates happens at the producer level. “Retailers are very conscious of the amount we’re putting out versus what we’re selling,” says Chapman.

Fofana’s research wraps up in 2016, at which point the best non-greening potato varieties produced during the study will be unveiled. After that, he says two to three more years will be required to address other performance tests in the field. “It’s not only about selecting good genetics — it’s basically to make sure the genetics we are selecting are safe, high-yielding, resistant to pathogens and also have other characteristics the industry is looking for,” says Fofana.

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