The 2012 ASHS Annual Conference

In cryopreservation, using dormant winter buds (DB) as source plant materials is economically advantageous over tissue culture options (TC). Processing DB does not require aseptic conditions and elaborate cryopreservation procedures. However, the DB approach is only feasible for cryopreserving a select number of temperate tree species. The objective of our study was to evaluate cryotolerance of 14 Salix germplasm accessions that represent seven different species in the USDA-ARS National Plant Germplasm System.  One-year old twigs harvested in December or January, were cut into either seven (7) or 10 cm segments. A part of the twig segments was slow cooled to –35 °C and exposed to the vapor phase of liquid nitrogen (LNV) for at least seven days and the other part was stored in –4 °C. After cryoexposure, LNV exposed and –4 °C twigs were warmed and direct-rooted in plastic containers (sterile peat moss, vermiculate, sand) in a cold greenhouse. Six weeks later, the material was evaluated for shoot and root development. Twig segments that developed a shoot were considered viable.  For the 7 cm long budwood segments, between 50% and 100% of the –4 °C and 0% to 100% of the LNV treated materials were viable.  The 10-cm long segments had viability that ranged from 68.5% to 100%.  The higher survival of the 10-cm long segments indicates that longer twig segments may be better suited for cryopreservation of Salix DB.