Cryopreservation of genetic resources of plum and apple

P. Brandova, J. Sedlak, F. Paprstein
Genetic resources of clonally propagated fruit species cannot be stored as seed and alternative storage methods that are long-term and effective for a wide range of genotypes are important for breeding teams and genebank curators. Cryopreservation in liquid nitrogen is one of these techniques. In our study, in vitro shoot tips of 2 temperate fruit crops (plum and apple) encapsulated in sodium alginate were successfully cryopreserved using 3 different methods based on vitrification and two-step freezing. Initial in vitro shoots were previously established and multiplied on MS medium in Erlenmeyer flasks with 25 mL of MS medium. Basic shoot tip cultures were cold-hardened for 4 weeks in 4°C. Explants (3 mm) aseptically dissected from cold hardened in vitro cultures were cold treated in MS medium supplemented with 2.0 M sucrose and for 48 h at 4°C. Shoot tips encapsulated in sodium alginate were dehydrated by exposure to a sterile air flow for a period of 8 h. Two freezing methods were tested and compared: fast cooling by direct immersion in liquid nitrogen (vitrification) and two variants of two-step freezing. The best results were obtained with a two-step freezing protocol in variant b) with progressive cooling at a rate of -4°C min‑1 to -40°C followed by immersion in liquid nitrogen. In this variant, total average survival rate used for apple and plum cultivars was 71.0%. High values of survival were also observed in the case of the two-step freezing protocol in variant a) with an average survival of 65.1%. Encapsulated shoot tips immersed directly to liquid nitrogen were cryopreserved with 59.4% survival. Described cryopreservation procedures were successfully applied for 6 cultivars of plum and apple.
Brandova, P., Sedlak, J. and Paprstein, F. (2021). Cryopreservation of genetic resources of plum and apple. Acta Hortic. 1307, 141-146
DOI: 10.17660/ActaHortic.2021.1307.22
fruit, Malus, Pyrus, freezing, cooling, survival, evaluation

Acta Horticulturae