Cryopreservation of Dendrobium heterocarpum Lindl. via encapsulation-dehydration method

The species Dendrobium heterocarpum Lindl., a wild orchid native to north and northeast Thailand, creates an aura of mystique and grandeur with their intricate flower appearance which enthralls many collectors within the country. An increase in collection for trade or any orther purposes may lead to a dramatic decrase in the population of this species, thus becoming rare or endangered species in the near future. Cryopreservation is an alternative means for conservation of plant genetic resources which can be applied to this species. This study, therefore, was aimed to optimize the conditions for encapsulation-dehydration method in D. heterocarpum. The protocorms were successfully cryopreserved as the following protocol. The protocorms were encapsulated with Ca-alginate, precultured on solid ND medium supplemented with 0.25 M sucrose for 1 week in the dark at 0°C and subsequently precultured in liquid ND medium supplemented with 0.25 M sucrose for 2 days in the dark at 0°C. Then, they were dehydrated by air-drying for 12 hours and plunged into LN for 1 day. Recovery percentage was 8.33% after 2 weeks of regrowth. However, preculture with ABA was found to insufficiently enhance freezing and thawing tolerance. TTC staining was negative and further regrowth on solid ND medium confirmed no survival of the cryopreserved protocorms.