Staff members are receiving training from the University of Idaho’s (U of I) Seed Potato Germplasm Program to operate a new cryopreservation machine that uses liquid nitrogen vapor to freeze seed potato tissue at a temperature of – 195 degrees Celsius for extended storage.

The state-of-the-art Seed Potato Germplasm laboratory at U of I, which opened in March 2022, is further modernized by the technology. For the benefit of seed potato growers and researchers both domestically and abroad, the facility generates disease-free potato germplasm.

Vapor-phase units are more efficient and less prone to sample contamination than cryopreservation units that freeze samples directly in liquid nitrogen.

“The vapor-phase cryopreservation unit will have the capacity to store meristems for up to 1,800 varieties of potato and important breeding clones. Meristematic tissue is the actively growing part of a plant, located at the very tip of the shoot, and can be used to reproduce an entire plant. A droplet containing 10 meristems, which are each about a millimeter long, will be vitrified on a foil strip and placed within a 2-milliliter vial. Boxes each containing 100 vials will be stored on racks above liquid nitrogen, inside of a 495-pound tank that is 61 inches tall and 31 inches in diameter,” according to a recent press release.

The laboratory is run by eight undergraduate plant sciences students. By the end of September, they will have completed their training and will be freezing their first samples for long-term storage. Within the first year of operation, they plan to cryogenically preserve and test 20 lines for viability.

The facility will be sponsored by a USD50,000 contribution from the Atchley Foundation Charitable Trust, which was founded by Ashton seed potato growers Clen and Emma Atchley, who met while studying at the University of Illinois.

The university bought its new unit for USD24,000 from a California-based distributor, Pacific Science. The remainder of the Atchley Foundation’s grant covered vials, boxes, hoses, and other necessary equipment and supplies.

Maintaining the Highest Quality Genetics

Both the new facility and the cryopreservation technology will help U of I maintain the highest quality genetics. The cryopreservation unit will enable researchers to more efficiently store a library of potato breeding clones and cultivars, helping breeding programs address future challenges such as climate change, pests, and diseases.

“It’s important because it allows us to store large amounts of genetically diverse material for future breeding purposes,” Shannon Kuhl, interim director of the Seed Potato Germplasm laboratory, mentioned.

After attending training on cryopreserving potato germplasm at Peru’s International Potato Center (CIP) last autumn, Kuhl made several equipment decisions based on her experience there. The center in Peru is one of the few establishments that now store potato germplasm in units comparable to this one. In the future, Kuhl plans to grow and run more units at the laboratory on the Moscow site.

The lab will preserve 100 to 150 meristems per cultivar and will periodically thaw a sampling of meristems from a grouping to test for viability. CIP reports an average survival rate per meristem of 60%.

To date, Kuhl and her staff have preserved potato germplasm by growing plants and creating clones using stem cuttings every four to six weeks. That process is time-consuming and can also occasionally lead to genetic mutations.

“The qualities of plants can change. We have had leaf color change and flower color change over time. With cryopreservation, chances of mutations in potato germplasm are reduced which will provide long-term, stable storage,” Kuhl added, explaining her lab must bring in replacement germplasm from other programs when that happens.

The laboratory will also utilize cryopreservation technology to remove viruses from newly submitted potato clones before storing and distributing them. Currently, cutting and regrowing plant stems multiple times while using a combination of heat exposure and chemotherapy is the procedure used to clean fresh clones. A year and a half is needed to guarantee that a clone is free of viruses and diseases. In contrast, a few months are needed to clean a clone at a cryopreservation facility. Meristematic tissue is frozen for a week, after which it is thawed and grows again into a viable plantlet.

“I think with our new building we need to step up our game a little bit. With the Atchley Foundation funding, we will be able to do just that. We are very appreciative,” Kuhl declared.

Paying Great Dividends for Both Early-generation Seed Farmers

Emma Atchley is confident that the investment will benefit potato variety development initiatives as well as early-generation seed farmers. To propagate early generation seed, she and her husband first began with seed planted in isolated areas, but they weren’t happy with the quality of the seed that was produced. The quality of their farm has significantly improved since U of I began supplying their germplasm.

According to Emma Atchley, the industry no longer worries about the potato leafroll virus, and the prevalence of some diseases has significantly decreased as seed production can begin with entirely disease-free material.

“We felt we wanted to support the university. We’ve had terrific quality. For 30-plus years we’ve never had a disease problem. We can’t say enough about having that facility at the University of Idaho. It’s a worldwide industry, we have worldwide recognition, and the state should have world-class research and world-class facilities to support that research,” Atchley mentioned, according to the press release.

Every year, the U of I distributes more than 300,000 disease-free potato plantlets and around 2,500 pounds of mini-tubers to seed producers and researchers around the globe. The process of growing lab-grown, clean in-vitro plantlets in a greenhouse yields mini-tubers, which seed manufacturers plant in the field the following year. U of I, which began its germplasm program in 1983, is the source of about 90% of potatoes grown in Idaho and 60% of potatoes raised nationwide.