The world’s largest potato cryobank at the International Potato Center (CIP) – status quo, protocol improvement through large-scale experiments and long-term monitoring

Authors: VOLLMER, RAINER - International Potato Center; VILLAGARAY, ROSALVA - International Potato Center; CASTRO, MARIO - International Potato Center; CARDENAS, J - International Potato Center; PINEDA, S - International Potato Center; ESPIRILLA, J - International Potato Center; Anglin, Noelle; ELLIS, DAVID - International Potato Center; AZEVEDO, VANIA - International Potato Center

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2022
Publication Date: 11/29/2022
Citation: Vollmer, R., Villagaray, R., Castro, M., Cardenas, J., Pineda, S., Espirilla, J., Anglin, N.L., Ellis, D., Azevedo, V. 2022. The world’s largest potato cryobank at the International Potato Center (CIP) – status quo, protocol improvement through large-scale experiments and long-term monitoring. Frontiers in Plant Science. 13. Article 1059817. https://doi.org/10.3389/fpls.2022.1059817.
DOI: https://doi.org/10.3389/fpls.2022.1059817

Interpretive Summary: Cryopreservation or the treatment and storage of plant samples in liquid nitrogen (-321F) can theoretically allow tissue to be conserved for generations into the future. Potatoes are challenging to conserve long term by traditional means because either the tubers need to be constantly grown in a field (annually) and stored in cold rooms after harvesting of the plants or plants need to be introduced into tissue culture which require aseptic conditions and constant propagation (~ every 3 months) in order to maintain a certain set of genes in a fixed state. Potato can produce botanical seed; however, each seed is a new combination of genes different to the mother and father which does not allow breeders and researchers to work with the same variety once a seed is produced. Cryopreservation allows potatoes to be frozen in liquid nitrogen and stored indefinitely, providing valuable germplasm in a secured state for future generations and helping assure no loss of germplasm as modernization and growth occurs worldwide. This work will detail the history of the cryopreservation program at the International Potato Center (CIP), the protocol for performing cryo on potato, and demonstrate that the protocol is applicable across a wide range of potato germplasm (diverse set). Further, research has been performed to evaluate recovery of potato germplasm after removal from liquid nitrogen storage, demonstrating that potatoes can remain in "suspended animation" in liquid nitrogen for a period of time and then be "reawoken" upon defrosting to produce a normal potato plant.

Technical Abstract: Long-term conservation of Plant Genetic Resources (PGR) is a key priority for guaranteeing food security and sustainability of agricultural systems for current and future generations. The need for this secure conservation of genetic resources collections is critical today, with rapid and extreme climatic changes threatening and reducing biodiversity in their natural environments. The International Potato Center (CIP) conserves one of the most complete and diverse genetic resources collections of potato diversity, with more than 7500 accessions consisting of 4900 cultivated potato and 2600 wild relative accessions. The clonal conservation of cultivated potatoes, principally landraces, through in vitro or field collections is indispensable to maintain fixed allelic states, yet it is cost prohibitive- and labor-intensive. Cryopreservation, the conservation of biological samples in liquid nitrogen (-196C), is considered as the most reliable and cost-efficient long-term ex-situ conservation method for clonal crops. Over the last decade, CIP has built one of the largest potato cryobanks worldwide, which holds more than 4000 cultivated potato accessions. The development of an applied robust cryopreservation protocol for potato serves as a model for other crop species especially clonally maintained collections. The CIP cryobank has designed experiments with a high number of genetically diverse genotypes (70-100 accessions), to obtain reliable results that can be extrapolated over a collection as genotypes can often respond variably to the same applied conditions. Unlike most published reports on the cryopreservation of plants, these large-scale experiments on potato were unique as they looked at the acclimatization process of in vitro plants prior to, as well as during cryopreservation and following through to the post-thawing recovery cycle on up to ten times the number of genotypes conventionally reported in the published literature. As a result, an operational cryopreservation protocol was advanced that works well across diverse accessions, that not only reduced process time and costs, but also increased the average full-plant recovery rate from 59% to 71% (+LN) for routine cryopreservation. The present article describes the composition of CIP’s cryobank, the cryopreservation protocol itself, as well as the results obtained for the above-mentioned research activities.