Monday, October 26, 2009

Ag Extension Research News


Steve Ritter photo
Scientists Use Genetic Markers to Develop Potatoes
That Fry Up Light Even After Cold Storage
by Marlene Fritz

KIMBERLY, Idaho—In Idaho and across the nation, freshly harvested potatoes are in the early days of a storage season that—for some varieties—could continue through next August. When held at temperatures of 45 degrees Fahrenheit or higher, they won’t develop cold-induced “sweetening”—an undesirable process in which sugars within spuds produce dark fries that are unacceptable to consumers—but they’re more likely to sprout, lose moisture and develop storage-related diseases.

At the University of Idaho, postharvest physiologist Sanjay Gupta suspects we could have cold-stored potatoes and enjoy eating them, too. “That would be a very significant improvement,” he said. “Cold sweetening has been a problem for the potato industry for a very long time.”

Gupta has teamed with Richard Novy, Aberdeen-based USDA Agricultural Research Service potato breeder, and two Midwestern scientists to select breeding lines for their resistance to cold-induced sweetening. Potatoes that could be stored at or below 42 degrees Fahrenheit and still fry up light wouldn’t need as many sprout inhibition treatments, Gupta said. As living seed, they would respire less at colder temperatures, thereby retaining moisture and weight, and would be less prone to plant diseases.

While at the University of Minnesota, Gupta began developing two biochemical markers that reveal a potato’s propensity to tolerate cold storage. One of the biochemical markers is a protein called UDP-Glucose pyrophosphorylase that controls the formation of sucrose from the potatoes’ starches; the other, acid invertase, controls the formation of the reducing sugars glucose and fructose from sucrose. Together, they indicate not only how well a variety can be stored at lower temperatures but for how long.

Gupta refined the markers at the University of Idaho’s Kimberly Research and Extension Center. Along with Martin Glynn of the USDA-ARS in East Grand Forks and Joe Sowokinos of the University of Minnesota, he then used the markers to screen about 300 experimental clones and commercial varieties from a dozen North American breeding programs. The markers predicted with about 90 percent accuracy a potato’s response to storage temperatures.

“Understanding the underlying mechanism of cold-sweetening is a big benefit to breeders,” said Novy. “We can intercross parents having divergent cold-induced sweetening resistance and make greater gains, because many of their offspring will be more resistant than either parent.”

By choosing the right parents, breeders could significantly accelerate the development of potatoes with the level of cold-sweetening resistance the market seeks, Gupta said.

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