Cryopreservation of Cymbidium finlaysonianum Lindl. by encapsulation-dehydration method

Thailand is home to a variety of wild orchids, most of which grow on trees in the forests. However, overexploitation of wild populations along with loss of habitat has accounted for the threatened status of wild orchids. Hence, conservation of wild orchids is urgently needed in the country. The specific purpose of this study was to establish a simple and reproducible protocol for the encapsulation-dehydration based cryopreservation of the orchid species Cymbidium finlaysonianum, which represents one of the threatened orchid species in Thailand. In this study, protocorms (2-3 mm in diameter) of the orchid were precultured for 24 h in liquid New Dogashima (ND) medium containing 0-1 M sucrose, encapsulated in 3% w/v Ca-alginate, pretreated for 24 h in liquid ND medium supplemented with 1.5 M sucrose and dehydrated for 0-12 h before plunging into liquid nitrogen for 48 h. The results showed that preculture of the protocorms with 0.75 M sucrose before encapsulation, followed by pretreatment with 1.5 M sucrose and dehydration for 12 h yielded the highest viability and regrowth (65.56%) of the protocorms determined following a 48 h cryopreservation process. Random amplified polymorphic DNA analysis employed for comparison of the polymorphic bands between plantlets raised from non-cryopreserved and cryopreserved protocorms revealed a similar index value of 0.998 indicating the genetic stability of the cryopreserved protocorms