Pinto Gold, a potato variety developed by the University of Maine’s potato breeding and variety development program, made its debut in May 2018.
Named for its alternating patches of red and yellow skin colors, the yellow-fleshed tubers range from oval to fingerling shapes, said Gregory Porter, professor of crop ecology and management at the university. He leads the potato breeding and development program at the Aroostook Farm, a research farm in the heart of Maine potato country.
Pinto Gold is the fourth potato variety released by the university, in cooperation with the Maine Potato Board, since 2014.
In 2015, the Caribou Russet, a cross of the Silverton Russet potato and the Reeves Kingpin, was developed as a dual-purpose potato (baked or mashed) for fresh-market consumers and also for potato processing markets, Porter said.
The Easton (a french-fry variety) and Sebec (a high-yield potato chip variety), both released in February 2014, were primarily developed for the processing industry, but are suitable for fresh market sales as well.
Located on Houlton Road in Presque Isle, the largest city in Aroostook County, the 425-acre research facility features a barn, a four-laboratory-office complex, a main office, two machine storage buildings, a potato storage research facility, and a 2,800-square-foot, year-round greenhouse, along with other office areas. It is the largest of the university’s five experimental farms and its research focuses on a wide range of concerns related to the state’s potato industry.
Aroostook County produces 90 percent of all potatoes grown in Maine.
While speaking to potato farmers attending the annual Maine Potato Field Day tour, Porter stopped in one of the research potato plots and held up a small jar filled with seeds.
“I’ve been carrying around these pretty, little, green berries so I can tell you a little bit about one of our major activities,” Porter said, passing the container to one member of the group. “The variety trials here (the seeds in the jar) you are looking at are the most advanced material we are trying to screen and isolate to select which ones might have potential for the industry. But, before we can get down to a handful of varieties to evaluate, our breeding program has to create new varieties.”
Beth Plummer, the greenhouse crop technician, spends the winter crossing female and male “parents” that she “thinks have good characteristics,” Porter said. The goal is to get a potato plant that combines the best complementary characteristics of both parent plants and extract seeds from the hybrid plants.
“That’s the starting point,” Porter said. “You have a year of crossing in the greenhouse to produce two potato seeds. Each seed in that jar is a unique potato variety from that cross. Virtually all those individual offspring will be different from each other and represent a complexity of genetics. There’s a lot of research moving forward to try to simplify the genetics of potatoes so that the crosses are more predictable and more true to type. That may bear fruit over the next 10 or 12 years.”
Each year, two greenhouses at the farm are filled with hybrids that produce about 35,000 unique offspring, Porter said. Those offspring, plus 50,000 or more from other breeding programs in North America, are planted in fields for the seed farm breeding program.
“From the 50,000, I’ll select 1,500 to go into year two,” Porter said. “Then we select 300 or so for third-year material. We go through six to 10 years of variety trials and one in 10 will actually make it into production.”
A new potato variety released for commercial production represents a significant investment, Porter said. It typically takes about eight years or more before a new potato variety is selected for potential commercial production.
“In order to get it out on commercial seed farms, you have to put it through a laboratory procedure to make sure that you get all of the soil-borne diseases and plant viruses out of the plant material,” Porter said. “That cleanup period takes about a year and costs us about $1,500 to $2,000 to do that for each clone. Then, it takes a number of years to build up actual seed tubers from that clean material.”
“About 10% of the program each year is red skin and yellow flesh material. It’s a small segment for our industry, but it’s an important one,” he said.
Red-skinned potato varieties grown in other parts of the country do not thrive in Maine. Cold conditions and sandy soil in the state inhibit tubers from attaining maturity, Porter said.
“By selecting for them here, we anticipate, eventually, we will find some reds that allow large-scale production reds,” Porter said. “We can already access the small-scale specialty market as we did with the Pinto Golds, because we have such a vibrant farmer market (and) roadside stand diversified farming community in Maine.”
When the Pinto Golds were selected, the scientists said: “Wow! This is really different,” according to Porter.
It has very small tubers, and a bright red and yellow skin patterning with mixed colors on each tuber. In addition, Porter said, the potato’s creamy texture when baked, boiled or mashed appeals to niche specialty and gourmet markets.
In the test fields of the Aroostook seed farm, Mother Nature selects the hybrid that best adapts to soil and climate conditions, and that is genetically resistant to common soil-borne diseases, Porter said. There’s no irrigation, no pest management, no fertilization ... it’s survival of the fittest tuber.
“That way, we know quite early — after the third year of screening — whether a variety has late blight resistance, pink rot resistance, scab resistance, potato virus resistance and early die resistance ... those are our four top targets for increasing pest resistance,” Porter said. “So, we don’t specifically do IPM work, but we’re trying to cross and develop material with this tolerance, which is important to growers in the East.”
A three-year crop rotation plan is practiced on the seed farm, Porter said. A field that was dedicated to potatoes the previous year is seeded to grain; and, a rye-grass under-seeding that grows to rye grass the next year. The oats and rye grass “provide a break from the diseases to which potatoes are susceptible,” he said. Clover or alfalfa is used in the rotation to furnish nitrogen to the soil.
For more information on the potato breeding and variety development program at the Aroostook Research Farm, visit umaine.edu/aroostookfarm/home/about/.