Effect of cryopreservation on in vitro seed germination and protocorm growth of Mediterranean orchids

BACKGROUND: Cryopreservation is an effective method for the long-term conservation of plant germplasm. OBJECTIVE: In the present study the effect of liquid nitrogen on seed structure, germination and protocorm development of eight Mediterranean orchid species was evaluated. MATERIALS AND METHODS: A scanning electron microscopy analysis was conducted to investigate the effect of the immersion in liquid nitrogen on seed integuments. Germination and protocorms growth were obtained applying in vitro cultures techniques. RESULTS: No micromorphological differences emerged between cryopreserved and untreated seeds. The effect of the treatment on the seed germination varied on the basis of the species. For Ophrys sphegodes ssp. passionis and Orchis mascula, freezing resulted in a significant increase of germination percentages. Protocorms of all species showed a positive growth trend although some significant differences of size occurred among the protocorms derived from treated and untreated seeds. CONCLUSION: Cryogenic techniques seem to have great potential in orchid germplasm conservation.