Cryopreservation of Tetraclinis articulata (vahl.) Masters.

Tetraclinis articulata shoot tips excised from in vitro grown shoots were cryopreserved using a modified PVS2-based vitrification protocol. Preliminary experiments with noncryostored shoot tips showed that the high concentrations of sucrose in loading (LS), vitrification (PVS2) and unloading (US) solutions employed in the protocol were very toxic for the explants. Replacement of sucrose by sorbitol in equal molar concentration in all these solutions enhanced survival of shoot tips after all treatments. However, cold-hardening of donor shoots before shoot tip excision was strictly required to obtain post-rewarming survival. Therefore, the protocol was outlined as follows: pre-conditioning of explants at 4°C for 3 weeks in the dark; excision of 1 mm long shoot tips; loading for 20 min in modified LS at room temperature; dehydration in modified PVS2 at 0°C for 60 min; immersion in liquid nitrogen (LN); rewarming at 40°C for 2 min and subsequent transfer of shoot tips in modified US for 20 min.