Simultaneous preservation of orchid seed and its fungal symbiont using encapsulation-dehydration is dependent on moisture content and storage temperature.

Seeds of Dactylorhiza fuchsii (common spotted orchid) and Anacamptis morio (green-winged orchid) were encapsulated in alginate beads with hyphae of the basidomycete fungus Ceratobasidium cornigerum. Pre-treatment of beads for 18 h with sucrose at an optimum concentration of 0.75 M decreased the desiccation rate in a flow of sterile air (c. 23 degree C, 30% RH) and increased seed and fungal survival after up to 16 h drying. Pre-treated and 16-h dried beads were transferred to cryo-vials and subsequently stored at a range of low temperatures for up to 30 d. Neither embryo growth of both orchids nor fungal development was detrimentally affected by 1 d storage at -196 degree C when the beads were pre-dried to c. 20% moisture content. Encapsulated D. fuchsii seed and compatible fungus had < 5% and < 45% viability when beads of the same moisture content were stored for 1 d at -20 degree C and -70 degree C respectively. In contrast, viability of the seed and the fungus remained unchanged during 30 days storage at -196 degree C but was progressively lost at 16 degree C over the same interval. The results indicate opportunities for the use of simultaneous cryopreservation as a conservation tool for diverse taxa.