Seed cryopreservation of selected Florida native orchid species

Abstract

Florida is a biodiversity hotspot for native orchids, containing half the species diversity of North America. Unfortunately, many populations of Florida native orchids are imperiled, accentuating the need for germplasm conservation. We aimed to optimise cryopreservation procedures for the conservation of Florida native orchid seeds. Germination of directly cryopreserved seeds was not significantly different from unfrozen controls for Bletia purpurea, Encyclia tampensis, Epidendrum amphytomum, E. nocturnum, E. rigidum, Eulophia alta and Prosthechea cochleata. Interspecific variation was observed as cryopreserved seeds of Calopogon tuberosus germinated at a higher rate (41%) than the unfrozen control (35%), whereas cryopreserved seeds of Cyrtopodium punctatum germinated at a lower rate (57%) than the unfrozen control (76%). Scanning electron microscopy confirmed immersion in liquid nitrogen did not cause seed coat damage in any of the nine species. Additionally, we equilibrated Bletia purpurea and Epidendrum nocturnum seeds to seven relative humidity levels prior to direct cryopreservation and found equilibration at RH ≤ 55% had no negative impact for either species. These studies represent initial procedures for the efficient conservation of Florida native orchids.