Orchid germplasm conservation by means of cryogenic techniques

Seed Banks represent an important resource for long-term storage of germplasm, allowing to address particular attention to endemic, rare and/or threatened plant species. Seed longevity, i.e. the period of survival during the storage, can greatly vary among species and accessions, with relation to genotypes variability and provenance (Hong & Ellis, 1996). Regard orchid seeds, it is not clear which is the best approach to a long-term storage (Seaton & Pritchard, 2008). In the present study, the effectiveness of cryopreservation technique has been evaluated on seeds of Mediterranean orchids. Percentage of in vitro seed germination and increase of protocorms size, after dipping in liquid nitrogen (LN) and following fast de-freezing, were compared with the same parameters recorded for unfrozen samples. Germination percentage widely varied among the considered species, being in the range between 14.6% (± 5.7), observed in Gymnadenia conopsea samples and 92.1% (± 4.1), recorded for Anacamptis coriophora seeds. Cryogenic treatment seemed negatively affect only the germination of Anacamptis coriophora. In vitro development appeared differently influenced by previous immersion in LN, with relation to species: the growth of Ophrys exaltata and Dactylorhiza sambucina proceeded without differences in treated and untreated samples. In vitro growth of A. coriophora, A. laxiflora e G. conopsea, instead, showed little differences during some phases within the four months considered, but the trend of the protocorm growth remained unaffected. These first results suggest that cryopreservation is an effective technique to storage orchid seeds, allowing a good germination and a regular development the protocorms after the de-freezing. Hong, T.D. and R.H. Ellis. 1996. A protocol to determine seed storage behaviour. IPGRI Technical Bulletin No. 1. (J.M.M. Engels and J. Toll, vol. eds.). International Plant Genetic Resources Institute, Rome, Italy, pp. 10-20. Seaton P.T., Pritchard H.W. 2008. Life in the Freezer, Orchids, pp. 167-170