Moscow, Idaho — The University of Idaho’s Seed Potato Germplasm Program is training staff to operate a new cryopreservation unit in which liquid nitrogen vapor will freeze seed potato tissue for long-term storage at negative 320 degrees.
The technology further modernizes U of I’s state-of-the art Seed Potato Germplasm laboratory, which opened in March of 2022. The laboratory produces disease-free potato germplasm for domestic and international seed potato growers and researchers.
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.
Eight undergraduate students majoring in plant sciences staff the laboratory. They will complete the training and begin freezing their first samples for long-term storage by the end of September. They anticipate cryogenically preserving and checking for viability on 20 lines within their first year of operation.
The unit will be funded with a $50,000 grant from the Atchley Foundation Charitable Trust, started by Ashton seed potato farmers Clen and Emma Atchley, who met while attending U of I.
Vapor-phase units are more efficient and less prone to sample contamination than cryopreservation units that freeze samples directly in liquid nitrogen. The university bought its new unit for $24,000 from a California-based distributor, Pacific Science. The remainder of Atchley Foundation’s grant covered vials, boxes, hoses and other necessary equipment and supplies.
U of I ships more than 300,000 disease-free potato plantlets and roughly 2,500 pounds of mini-tubers throughout the world each year to researchers and seed growers. Mini-tubers are produced by establishing lab-grown, clean in-vitro plantlets in the greenhouse, and the resulting tubers are then planted in the field the following year by seed producers. About 90% of the potatoes grown in Idaho and 60% of the spuds raised throughout the nation originate from U of I, which started its germplasm program in 1983.
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,” said Shannon Kuhl, interim director of the Seed Potato Germplasm laboratory.
Kuhl’s choice of equipment was informed by a trip she made to Peru’s International Potato Center (CIP) Last fall, where she underwent training on cryopreserving potato germplasm. The center in Peru is among a handful of facilities already using similar units for potato germplasm storage. Kuhl envisions expanding to operate additional units at the Moscow campus laboratory in the future.
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 percent.
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,” Kuhl said, explaining her lab must bring in replacement germplasm from other programs when that happens. “With cryopreservation, chances of mutations in potato germplasm are reduced which will provide long-term, stable storage.”
The cryopreservation technology will also be used to eliminate viruses in new potato clones that are submitted to the facility for storage and distribution. The current method of cleaning new clones involves a combination of chemotherapy and heat exposure, repeated over several cycles of cutting and regrowing plant stems. The process takes a year and a half to ensure a clone is virus and disease free. Cleaning a clone in a cryopreservation unit, by contrast, takes just a few months – meristematic tissue is frozen for about a week and then thawed and regrown into a viable plantlet.
“I think with our new building we need to step up our game a little bit,” Kuhl said. “With the Atchley Foundation funding we will be able to do just that. We are very appreciative.”
Emma Atchley believes the investment will pay great dividends for both early generation seed farmers and potato variety development programs. She and her husband initially started with seed raised in remote locations to propagate early generation seed, but they weren’t satisfied by the resulting quality. Their farm has had much better quality since U of I started providing their germplasm. Emma Atchley believes the ability to start seed production with completely disease-free material has considerably reduced the prevalence of certain diseases and eliminated potato leafroll virus as a disease of concern for the industry.
“We felt we wanted to support the university. We’ve had terrific quality. For 30-plus years we’ve never had a disease problem,” Emma Atchley said. “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.”