Simultaneous encapsulation of seed and mycorrhizal fungi for long-term storage and propagation of terrestrial orchids
Karen D. Sommerville A C , John P. Siemon A , Chris B. Wood B and Catherine A. Offord AA Botanic Gardens Trust, Mount Annan Botanic Garden, Mount Annan, NSW 2567, Australia.
B Education Enhancement Unit, University of Exeter, Exeter EX4 4QJ, United Kingdom.
C Corresponding author. Email: karen.sommerville@rbgsyd.nsw.gov.au
Australian Journal of Botany 56(7) 609-615 https://doi.org/10.1071/BT08008
Submitted: 17 January 2008 Accepted: 20 August 2008 Published: 26 November 2008
Abstract
Ex situ conservation of threatened terrestrial orchids requires the simultaneous conservation of their mycorrhizal associations. A method for encapsulating both seed and fungi in alginate beads (known as encapsulation–dehydration) was applied to the storage and propagation of two endangered orchid species in NSW, Australia—Pterostylis saxicola D.L.Jones & M.A.Clem. and Diuris arenaria D.L.Jones. We tested the effect of storage duration and temperature on fungal recovery and germination potential in vitro, and recorded survival for seedlings subsequently transferred to potting mix. Storage at 23°C significantly reduced fungal recovery and germination for both species after only 3 months (P < 0.05), whereas storage at 4°C significantly reduced fungal recovery for P. saxicola after 6 months (P < 0.05). Storage for 6 months at −18 and −196°C had no significant effect on the fungal recovery and germination percentages of either species. All beads transferred directly from in vitro culture to potting mix resulted in the establishment of at least one seedling, and production of a healthy tuberoid, when transferred near the commencement of the natural growing season. The encapsulation–dehydration method may have a practical application for use in ex situ conservation of other terrestrial orchids, as well as their mycorrhizal fungi.
Acknowledgements
This research was funded by the Hermon Slade Foundation and the Botanic Gardens Trust Orchid Fund. We thank the Plant Breeding Institute, Cobbitty, for use of their cryopreservation facilities, the Plant Disease and Diagnostic Unit of the Botanic Gardens Trust (BGT) for providing media for fungal isolation and advice on methods for storing Rhizoctonia species, and Carolyn Porter (from the Molecular Systematics Laboratory of the BGT) for extraction, amplification and sequencing of fungal DNA. We thank John Riley, Lotte von Richter, Margaret Heslewood and Amanda Rollason for their assistance in collecting, cultivating and hand-pollinating the plants used in this study. We also thank several anonymous reviewers for their helpful suggestions.
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