Relative importance of seed drying rate, desiccation tolerance, and cryotolerance for the conservation of ardisia elliptica, a. Brunnescens and a. Virens

BACKGROUND: The pan-Tropical genus Ardisia has more than 400 species and is of high horticultural and medicinal value. Due to overexploitation it is important to conserve the germplasm of this genus. OBJECTIVE: To investigate the feasibility and methods of cryopreservation for long-Term seed storage of three Ardisia species: A. elliptica Thunb., A. brunnescens Walker, and A. virens Kurz. METHODS:We tested whether rapid desiccation can increase desiccation tolerance and cryotolerance, and whether the thawing rate can affect cryopreservation success. Seeds were subjected to three desiccation treatments: 1) activated silica gel at 25 ± 2°C, and 4% relative humidity (RH); 2) saturated NaCl solution in closed jars in 25 ± 2°C and 75% RH; and 3) air-drying at room conditions at 27 ± 2°C and RH 60% for different desiccation durations (12h, 24h, 48h, 96h, and 196h). Seeds were then assessed for desiccation tolerance and cryotolerance after rapid thawing (direct immersion in 36°C water bath for 2 min) or slow thawing (at 27°C for 1 h). RESULTS: For all three species, desiccation method and duration significantly affected cryotolerance (P < 0.0001). Fast desiccation did not improve germination compared to slower desiccation (P < 0.01). Whereas A. elliptica germination was unaffected by desiccation duration, drying time significantly (P < 0.0001) affected germination percentage in the other two species especially after 48h. Although slow thawing improved cryotolerance of A. brunnescens seeds (P <0.05), there was no significant effect of thawing rate on A. elliptica. A. virens seed did not survive cryopreservation. CONCLUSIONS: Cryopreservation protocols of Ardisia species may be species-specific and should be established for each species in the genus so that cryopreservation can be used as a successful conservation strategy.