Cryopreservation of strawberry genetic resources in Germany

The National German Strawberry Genebank has 369 cultivars and 318 accessions of wild Fragaria species maintained in a field collection at Dresden-Pillnitz. Conservation of clonal crops requires safety duplication. A calculation of the efforts required to establish and maintain a safety backup of the whole collection with in vitro cold storage indicated that it is too labour intensive to maintain the collection in such form. The development of an effective method for cryopreservation is required for a cost effective long-term storage. Four distinct cryopreservation protocols were tested: two protocols using Plant Vitrification Solution 2 (PVS2), encapsulation dehydration and controlled rate cooling. All four methods were equally effective for the cultivars tested, however the Fragaria wild species had significantly better regrowth with the PVS2 vitrification protocol that included 14 d alternating-temperature cold acclimation (16 h at -1°C and 8 h at 22°C). The PVS2 vitrification protocol with cold acclimation will be applied as the standard method for cryopreservation of Fragaria cultivars and wild species. Currently, the Dresden-Pillnitz Institute has 23 different Fragaria accessions in cryopreservation.