Cryopreservation of Orchid Genetic Resources by Desiccation: A Case Study of Bletilla formosana

Abstract

Many native orchid populations declined yearly due to economic development and climate change. This resulted in some wild orchids being threatened. In order to maintain the orchid genetic resources, development of proper methods for the long-term preservation is urgent. Low temperature or dry storage methods for the preservation of orchid genetic resources have been implemented but are not effective in maintaining high viability of certain orchids for long periods. Cryopreservation is one of the most acceptable methods for long-term conservation of plant germplasm. Orchid seeds and pollens are ideal materials for long-term preservation (seed banking) in liquid nitrogen (LN) as the seeds and pollens are minute, enabling the storage of many hundreds of thousands of seeds or pollens in a small vial, and as most species germinate readily, making the technique very economical. This article describes cryopreservation of orchid genetic resources by desiccation and a case study of Bletilla formosana. We hope to provide a more practical potential cryopreservation method for future research needs.

Advances in Orchid Biology: Biotechnological Achievements, Translational Success, and Commercial Outcomes

“…However, this low temperature and dry storage-based method is successful for 1 to 6 months of germplasm preservation but fails to provide high viability of germplasm under preservation for longer durations [80,81]. Cryopreservation is the best germplasm preservation approach as all the metabolic and physiological processes cease at the temperature −196 • C [82]. The pretreatment of orchid seeds and pollens germplasm through vitrification, desiccation, and encapsulation-dehydration methods of removing the cell water content before cryopreserving in liquid nitrogen are employed [83,84].…”

“…Vitrification has helped in the conservation through cryopreservation of immature and high-water-content seeds of several orchid genera, viz. Bletilla, Cymbidium, Dendrobium, Encyclia, Phaius, and Vanda [82].…”

“…Desiccation-based cryopreservation is found to be more suitable for mature orchid seeds. The process of desiccation includes the slow drying of seeds under a controlled desiccation rate under constant relative humidity or drying with silica gel or with CaCl 2 .6H 2 O salt solution to reduce the water content of the seeds before preserving them in liquid nitrogen [82]. Several orchids, viz.…”

“…Several orchids, viz. Bletilla formosana, Caladenia flava, Dactylorhiza fuchsii, Diuris fragrantissima, Eulophia gonychlia, Gymnadenia conopsea, Orchis coriophora, Paphiopedilum rothschildianum, Pterostylis sanguinea, Thelymitra macrophylla, and Dendrobium candidum, were successively cryopreserved using the desiccation technique [82,87].…”