Cryopreservation of raspberry cultivar accessions bred in Russia from the VIR in vitro collection

Cryobanks use plant cryocollections for long-term preservation of crops which cannot be preserved in seed collections. These are vegetatively propagated crops, accessions of species which form either a small amount of seeds, or recalcitrant seeds. Shoot tips (apexes) of in vitro plants are used for cryopreservation for most berry crops, therefore maintenance of in vitro collections is very important. The VIR in vitro collection includes 150 accessions of Rubus L. species, 85 of them are raspberry cultivars, 59 of which were bred in Russia. These cultivars reflect a wide ecogeographic diversity. Among them, there are raspberry cultivars created at the end of the 19th – first half of the 20th centuries, including cultivars bred by I.V. Michurin and by the pioneer of northern horticulture V.V. Spirin. More than half of national raspberry varieties (33) are listed in the State Register for Selection Achievements Admitted for Usage. Raspberry cultivars from Russian breeding programs have a very limited representation in foreign genebanks. The first aim of the present work was cryopreservation of mostly folk and old Russian raspberry cultivars received by VIR from 1925 till 1950 and their transfer into the cryobank. The second aim of the work was to monitor post-cryogenic regeneration of raspberry cultivars transferred to the cryobank earlier. A modified protocol of the droplet vitrification method by “DV-biotech” was used for cryopreservation of shoot tips of in vitro plants of 10 raspberry cultivars (7 of which are folk and old Russian ones) from the VIR in vitro collection. Post-cryogenic regeneration was evaluated for 17 raspberry cultivars preserved in the cryobank from one to five years. Ten raspberry cultivars (900 apexes) with an average mean post-cryoregenic regeneration value of 38.2±3.0% determined in control tests, were placed in the cryobank for long-term storage. A statistically significant effect of the genotype on the viability of explants after cryopreservation was noted, while the post-cryogenic regeneration was genotype insensitive. Additionally, levels of post-cryogenic regeneration were evaluated for 17 raspberry cultivars (296 apexes) preserved in the cryobank from one to five years. Post-cryogenic regeneration within the 20-70% range was displayed by four raspberry cultivars preserved in the cryobank for one year, and for 8 cultivars conserved there from three to five years post-cryogenic regeneration was within the 10-50% range. According to the results of monitoring, regeneration displayed by 12 raspberry cultivars was within the 10-70% range, which can be considered as a reliable rate of apex preservation in liquid nitrogen vapors in the VIR cryobank. Monitoring of the post-cryogenic regeneration of the raspberry accessions preserved in the VIR cryobank and cryopreservation of new raspberry cultivars will be continued.