Cryopreservation of genetic resources of plum and apple

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.

XV EUCARPIA Symposium on Fruit Breeding and Genetics

P. Brandova, J. Sedlak, F. Paprstein

fruit, Malus, Pyrus, freezing, cooling, survival, evaluation

https://doi.org/10.17660/ActaHortic.2021.1307.22