Cryopreservation of Dormant In Vivo- Buds of Hybrid Aspen: Timing as Critical Factor

BACKGROUND: For the conservation of hybrid aspen germplasm, cryostorage of dormant in vivo buds is a convenient back-up method for field collections. In practice in Finland, bud collection is performed from February to March. OBJECTIVE: The aim of this study was to assess how this time schedule can be extended without compromising regeneration. In addition, an easily measurable marker for successful cryopreservation was examined. MATERIALS AND METHODS: Timing of cryopreservation was tested from August to February, using dormant buds from both outdoor and indoor plants. To find a marker, water content and gene expression of hydrid aspens, as well as environmental factors such as temperature, temperature sum, and light period were followed. RESULTS: Cryopreservation was successful from October to February, when, on an average, at least 75% of the buds regenerated through micropropagation, and there was no difference to non-frozen controls. Significant genotypic variation was observed in October and February, with regeneration rates of 61-100% and 37-98%, respectively. No marker for successful cryopreservation was found among the studied factors. CONCLUSION: The results provide flexibility for the undertaking of practical work, with a recommendation that cryopreservation can be carried out from November to January – earlier than the current practice.