June 25, 2018
By Melissa Hemken
Whether you say “potato” or “potata,” it’s still the same vegetable. For breeders, though, the makeup of this popular tuber could be changing. For some time, potato breeders have considered shape, appearance, overall size, eye depth, yield, disease resistance and other attributes when developing new potato varieties.
Yet, as the nutritional content of the potato comes under greater scrutiny, university researchers are working to meet new consumer needs. Researchers have identified which potato strains hold more nutritional value — such as a high content of vitamin B9 and low levels of branched starch (glucose). This research shift is in response to consumers who are more aware of the foods they eat, and the composition of those foods.
“We’re trying to feed people better than previously,” explains David Sands, professor of plant sciences and plant pathology at Montana State University. “Biochemistry and the medical community tell us what to breed into plants to improve our diets: more omega-3, antioxidants, lysine and straight starch. We got away from nutrition by mainly breeding crops for high yields, which is what the farmer gets paid for.”
Sands and his research team determined which potato varieties currently on the market are lowest on the glycemic index, and they are now cross-breeding 23 strains of these potatoes in his lab to create more. After testing 125 potato varieties currently available as seed potatoes, Sands determined that Huckleberry Gold — developed by the Potato Variety Management Institute Tri-State breeding team — is the potato with the lowest amount of branched starch, so far.
The more amylopectin, or branched starch, in a potato, the more glucose is released in your body an hour or two after you eat it. For a potato to rank low on the glycemic index, it needs to contain straight starch rather than branched starch.
“I think the market is starting to shift already just on hearing that Huckleberry Gold is low-glycemic,” Sands says. “The market will actually go ahead of the human testing, strangely enough. People care about their diet, and potato eaters — even if they have diabetes — like to eat potatoes."
In the U.S., 9.4% of people have diabetes or prediabetes. In China, 11.6% of the population is diabetic. This shows the market potential for low-glycemic potatoes.
Most potatoes are rich in vitamin C, which is essential to grow and repair body tissues, support the immune system, and maintain cartilage, bones and teeth. Potassium, also high in potatoes, reduces high blood pressure, benefits the heart and kidneys, and tends to reduce the effects of anxiety and stress. Minimal research has been completed on the other vitamins and nutrients in potatoes.
This is why Aymeric Goyer, associate professor in the College of Agricultural Sciences at Oregon State University, studied the levels of vitamin B9, or folate, in different potatoes. Vitamin B9 is essential for optimal brain and nerve function, and for infant development.
Goyer and his team tested more than 120 potato varieties to see which strains contain the most folate. They found that commercially available seed potatoes contain the same range of folate concentration, but they distinguished wild potato genotypes with much higher amounts of folate growing in the Andes Mountains in South America — which is where potatoes originated.
“We found that the Solanum boliviense potato contains at least three times the amount of B9 that we found in commercial varieties,” Goyer explains of the research results. “Now potato breeders can take the high-folate wild potato species and introduce vitamin B9 traits into their commercial potato varieties.”
Potatoes also need long dormancy for storage, and no cold-induced sweetening. Goyer switched his research focus from B9 to how storage influences the level of vitamins in potatoes. Most potatoes are stored at low temperature for several months. During storage, vitamin C decreases as much as 50% in current potato varieties.
“We’re trying to better understand why there is this decline in vitamin C,” Goyer explains, “and how we can stop it. At the same time, we’re looking at stability of other vitamins: B9, B1 and B6. So far, with vitamin B9, we’ve observed there’s a trend for an increase of vitamin B9 during storage in certain varieties.”
Some potatoes accumulate two times the amount of folate present at harvest after four to eight months in low-temperature storage.
“We think breeders can use plant genetic tools to increase B9 at least twofold in potatoes,” Goyer says. “Then, if you take a twofold increase after cold-temperature storage — an environmental factor — you’re at four times the amount of B9 that is currently in potatoes.”
According to the U.S. Economic Research Service, potatoes counted for 15% of farm receipt sales of vegetables in 2016. The U.S. potato market is stable, and consumption increased 32% in the 46 years between 1970 and 2016.
An increasing number of people choose their food purchases based on nutrition value. For the potato market to remain strong, it’s important that the 44 billion pounds of potatoes annually grown in the U.S. meet the nutrition needs of consumers.
“Hippocrates said, ‘Let food be thy medicine and medicine be thy food,’” Sands says. “We really need to refocus agriculture on nutrition, because — by eating more nutritious food — we could save 10 times or more money that we currently spend on medical care, and help people be happier, healthier and more productive. Agriculture science is more important than rocket science. We can grow better food.”
It’s about the starch
Branched starch fluffs up a cooked potato, pea or wheat, and is the cheapest way to make large amounts of plants. When yield is measured by the weight of the plants, as in potatoes, the branched starch (amylopectin) is increased, and the straight starch (amylose) is bred down. This is why, in the pursuit of high yields (U.S. average 46,816 pounds per acre in 2016), potatoes now mostly contain branched starch. When eaten, the branched starch converts to glucose, which is detrimental to diabetics; or it’s a strong negative when consumed in large quantities by diet-conscious consumers.
Potato breeding facts
It takes 10 to 12 years of breeding before a new potato hits the commercial market. In traditional plant breeding, two plants are crossed, and researchers select plants for yield, shape, storage, etc. During this process, thousands of genes are inherited. However, the majority is not involved in producing the traits that the breeder is selecting for, and the function of most genes is currently unknown. Nevertheless, new biotechnology tools of genome editing can vastly improve plant breeding.
“Genome editing could really help produce the ultimate potato variety,” Goyer explains. “If we can market plants developed with these biotechnology tools, I think there will be a second Green Revolution. The first one occurred between the 1930s and the late 1960s. Genome editing is like high-precision surgery, where you can precisely see what you’re doing in a plant — which is not the case in traditional breeding.”
The U.S. Food and Drug Administration has yet to decide whether plants developed using genome editing will be subject to the same regulations as GMOs.
“Even without GMOs, we’ve been able to do a lot with potatoes,” adds Sands. “Over 10,000 years ago when potatoes were first developed, the people that grew them depended on them. They probably had lower yields than we have now, but they may have had antibacterial properties. They may have had lots of things that we should look at. And that’s what we're doing.”
Sources for seed potatoes
The Northern states — Montana, Oregon, Colorado, Idaho, Washington, North Dakota and Maine — produce the best U.S. seed potatoes because of their cold climate, which decreases insect pests, nematodes, fungi and viruses. Montana State University even grows seed potatoes from carefully tested tissue culture to ensure clean stock, without pathogens, for seed potato growers in the state. In 2014, 3 million hundredweight of Montana seed potatoes were confirmed to be disease-free and sold through shipping point inspection.
Hemken writes from Lander, Wyo.
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