Cryopreservation of dormant buds can be a feasible method for long term preservation of clonally propagated woody plants. In the present study, dormant buds of blackcurrant (Ribes nigrum L) cultivar Mortti were cryopreserved. Twig segments from greenhouse and field grown plants were cooled at their natural moisture content at the rate of 0.17 °C min⁻¹ from zero to −38 °C, immersed in liquid nitrogen and stored in liquid nitrogen vapor. The post-cryopreservation regrowth of buds was evaluated in vitro and viability of recovered plants was tested in vivo. The estimated recovery rate for buds thawed after 1–6 days in cryostorage was 86% and 66% for outdoor and greenhouse grown buds, respectively. Microplants adequate in size and quality grew successfully in vivo and plants produced berries in field. After 4 years in cryostorage, the estimated recovery rate for outdoor buds was 58%. According to results from 1 to 6 days cryostorage, the tested dormant bud protocol turned to be applicable for cryopreservation of the blackcurrant cultivar Mortti. However, concerning the long-term preservation the decline of recovery is important to consider in the future experiments. The cryopreservation of dormant buds combined with in vitro recovery provides a feasible tool for conservation of plant genetic resources of blackcurrant.

The aim of plant gene banks is to preserve genetic resources selected based on their phenotypic, agronomic, historical or other cultural values for future utilization. In the present study the modified PVS2 droplet vitrification technique was tested and optimized for cryopreservation of a large diversity of blackcurrant (R. nigrum L.) accessions propagated in vitro and selected into a national gene bank core collection. Out of four accessions tested to optimize the method, three recovered and regenerated by 89–97% on average, but one recalcitrant in vitro line only by 25%. The tested post-cryopreservation recovery media with different macronutrient and growth regulator levels showed no generalized effect on regenerated shoots, but the effect of recovery media was different between cultivars. When the whole regeneration chain from cryopreservation via micropropagation to greenhouse conditions was tested, shoots at least 1 cm in length were found necessary for successful transfer ex vitro. The long-term cryopreservation of 22 blackcurrant accessions was finally conducted, with practices slightly modified from the tested protocol. The estimated recovery of shoot tips after 9 weeks in vitro was 17–94% with at least 75% recovery in seven accessions and at least 40% recovery in 19 out of 22 accessions. Only one accession had no cryopreservation success. The results demonstrated that the modified droplet vitrification technique is appropriate for a large diversity of blackcurrant accessions. However, cultivar-related differences and recovery procedures are to be considered for success in regeneration and ex vitro adaptation.

The cryopreservation of dormant buds can be a feasible method for preserving germplasm of cold-tolerant woody plants. In the present study, we evaluated the effects of pre-desiccation, thawing method, and the rehydration of bud sections on the post-cryopreservation recovery of dormant blackcurrant buds in vitro. The estimated recovery of small- and medium-sized buds was 80.1 and 62.7% respectively for desiccated buds and 67.8 and 72.3% respectively for non-desiccated buds. The pre-desiccation of bud sections enhanced the number of the shoots regenerated from vegetative buds (2.3 vs. 4.7). The estimated recovery of fast-thawed buds was better after 14-day than after 7-day rehydration (85 vs. 59%). In slowly thawed buds the difference between 14-day and 7-day rehydration was not significant (73 vs. 62%). The estimated recovery of vegetative and flower buds was 77.7 and 41.1% respectively after 7-day rehydration, and 95.2 and 43.6% respectively after a 14-day rehydration period. The rehydration of bud sections was not necessary for the in vitro recovery of non-desiccated, fast-thawed buds. Of the 23 blackcurrant cultivars cryopreserved using non-desiccated dormant buds collected from a greenhouse, the estimated recovery of 22 cultivars ranged between 42 and 90%.