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Vitrification-based cryopreservation of protocorm-like bodies of an endangered lady's slipper orchid: Paphiopedilum niveum (Rchb.f.) Stein.

BACKGROUND
Paphiopedilum niveum (Rchb.f.) Stein, an endangered lady's slipper orchid, is listed in CITES Appendix I and thus requires conserving.


OBJECTIVE
The study aimed to cryopreserve protocorm-like bodies (PLBs) by a vitrification technique.


MATERIALS AND METHODS
Four-month-old PLBs were precultured in modified Vacin and Went liquid medium with various sucrose concentrations for 24 h and 5 d with daily increasing sucrose concentrations followed by different exposure times to plant vitrification solution 2 (PVS2).


RESULTS
Precultured PLBs in 0.75 M sucrose for 5 d with stepwise increase of sucrose and PVS2 for 90 min provided the highest viability after drying to low moisture content. The cryopreserved PLBs exhibited fewer dark stained nuclei and accumulated starch grains than those of the control. Cryopreserved PLBs had some shrunken epidermal cells, no change in ploidy level, a survival level of 22 % and the regenerated plantlets grew well.


CONCLUSION
This study is the first report evaluating the success of cryopreserved PLBs of P. niveum via a vitrification protocol.