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New potato breeds: The fruit of much time and effort

The Yukon Gold potato has become a favourite of Canadian consumers, and small wonder: Its golden flesh, rich flavour and excellent appearance hit all the right marks. However, what makes the Yukon Gold a Canadian scientific triumph is the fact it was developed by the University of Guelph’s potato breeding program.

The Yukon Gold potato has become a favourite of Canadian consumers, and small wonder: Its golden flesh, rich flavour and excellent appearance hit all the right marks. However, what makes the Yukon Gold a Canadian scientific triumph is the fact it was developed by the University of Guelph’s potato breeding program.

The effort was spearheaded by potato breeder Dr. Gary Johnston, with support from Agriculture and Agri-food Canada (AAFC). One of his graduate students told Dr. Johnston about a Peruvian yellow-fleshed potato that was considered to be a local delicacy.

“On his next trip back to Guelph, he brought me a few tubers,” Dr. Johnston wrote in a 1998 letter. “They were indeed quite ‘tasty’ when cooked.”

The only downside is that the Peruvian potatoes were rough and small in size. No problem: “Why not try to create a potato variety with normal size, shallow eyes, globular shape and yellow flesh,” Dr. Johnston thought. To do this, the University of Guelph team crossed W5289-4 (a 2x cross between Yema de huevo and 2x Katahdin Pervuian breeds) and “Norgleam potatoes from North Dakota which had excellent shape and size, very early and had attractive appearance,” he wrote. “This cross was made in 1966. To my surprise true seed was produced and G6666 [the first of what would be called the Yukon Gold potato] was born.”

It took many more trials and growing, but the resulting Yukon Gold potato was eventually licensed – in 1980.

The time it took to develop the Yukon Gold comes as no surprise to Eugenia Banks.

“Breeding potatoes is a long process,” says Banks, a potato specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). “It takes about 14 years to develop a potato variety with traits that growers and consumers wish.”

Good looks matter – but they’re not everything

Thanks to modern genetic and cloning techniques, it is possible to create potatoes that are resistant to specific pests and bacteria, plus have the ability to better survive droughts and the other hazards that Mother Nature throws at them. But although breeds are being developed with these traits, “good looks” are driving the market these days.

“We are making tremendous progress in creating new strains of potatoes that are tougher than their predecessors,” says Dr. Walter De Jong, an associate professor and director of graduate studies in the field of plant breeding at Cornell University in Ithaca, N.Y. “But what are the top three things that the fresh produce market want most in new potato varieties? It’s simple: Appearance, appearance and appearance.”

In the world of potatoes, good looks means a tuber “with yellow flesh that is round to slightly oval,” says Keith Kuhl, president and CEO of the Southern Manitoba Potato Company in Winkler, Man. “Whatever eyes there are should be very shallow, such that you can remove them cleanly with just a pass of the potato peeler.”

Given the public’s preference for yellow-fleshed potatoes, the phrase “beauty is only skin deep” doesn’t apply here. But there are other qualities that define popular potatoes beyond appearance.

“A good ‘baker’ should have flesh that stays firm and doesn’t fall apart,” Kuhl says. “A good masher should stay moist for easy mashing without being mushy.”

From a potato farmer’s perspective, “the traits being sought for table potato varieties (white and yellow flesh) are consistent performance, early maturity, plus resistance to scab and to bruising,” says Banks.

And that’s not all: Besides the necessary good looks, great taste and reliable consistency, new breeds have to deliver high yields, have low nitrogen requirements and be easy to store for long time periods.

“They also require resistance to Verticillium [fungus], pink rot, leak, early and late blight, common mosaic,” says Banks. “For red-skinned varieties, the above traits apply but minimum skinning at harvest and a deep red skin colour that does not fade in storage are a must. For the table market, resistance to common scab is a priority these days because of the lack of reliable control methods for this soil borne bacterial disease.”

Then there’s the potato chip and French fry market. Potatoes grown for this sector must be low in sugar and high in starch. Otherwise, they will tend to turn brown when deep-fried, which doesn’t look as good to consumers as – you guessed it – golden brown.

“Colour turn is also an issue when potatoes are stored in cold,” Kuhl notes. “Again, potatoes with low sugar tend to retain their original colour at colder temperatures.”

That’s not all: Chipping potatoes must be at least medium-sized with average to above average yields, resist pitted scab, pink rot, leak and late blight, and tolerate being stored from harvest right to June of the following year – all without compromising their flavour.

The process

With all of these demands, it is not surprising that developing new potato varieties takes a lot of time. The process traditionally begins with researchers crossbreeding different breeds of potatoes, trying to come up with hybrids (like the Yukon Gold) that capture the best qualities of their parents.

However, it is now possible to identify genetic markers (specific known genes or DNA sequences) with specific parent breeds to improve the odds of successful hybridization. Genetic transplantation also offers opportunities for making better breeds of potato.

“The transgenic method – where you take desirable genes from other species and insert them into the potato plant – is not used these days due to negative public perceptions,” says Dr. De Jong. “There may be less hostility to inserting DNA from other potato species, so this may be one way that we can speed up the hybridization process.”

Whatever method is used, the bulk of the development process lies in planting the new breeds and in seeing what grows. Cloned plantings are often used, to ensure consistency among samples. Then they are bred, and bred again for a number of generations. The goal is to get to know each new breed’s characteristics and potential, in a range of growing conditions.

“The OMAFRA potato program evaluates about 600 new clones from university breeding programs each season,” says Banks.

These programs use seeds developed by the University of Wisconsin, Michigan State University, North Dakota State University, and the Tri-State Breeding Program (Idaho, Oregon and Washington states). Potato clones from European breeding programs, such as HZPC, Europlant and Solana, are included in OMAFRA’s annual evaluation.

“I usually walk plots after harvest, searching for clones that catch my attention,” Banks says. “In 2009, of 275 clones tested, only one caught my attention. I asked some growers to walk the same plot and let me know which, in their opinion, was the best. They all stopped at Clone 30, the same one I selected.”

Besides growing consistently during both the wet, cool year of 2009 and the hot summer of 2010, Clone 30 has other important attributes, she says. “Clone 30 is tasty, resistant to scab, and has smooth skin and white flesh.”

Besides Clone 30, “the North Dakota State University is very close to releasing a new red-skinned potato with high yield and excellent flavour,” Banks says. “For processing varieties, I have evaluated 180 clones from the University of Wisconsin. After five years, there are four clones that look promising.”

Better potatoes for all

The years spent in developing the Yukon Gold and newer promising potato breeds is time well spent. Table potatoes that are tasty and eye catching are better sellers, especially in an age when consumers’ cooking skills end at putting tubers in the microwave oven. Meanwhile, chipping potatoes that can go the distance in storage, low temperatures and high yields help keep manufacturing costs down and producer profits up.

For potato farmers, all this progress can be a bit bewildering. After all, there used to be only a handful of potato varieties being grown; now there are thousands to choose from. And they are better looking than ever.