Storage of rare and threatened NSW orchid species and their associated mycorrhizae

A project undertaken at The Botanic Gardens Trust, Sydney at Mount Annan Botanic Garden, and supervised by John Siemon and Cathy Offord.

Introduction and general aim:
The propagation and storage of terrestrial orchids is a complex area of research. Orchid seeds are tiny and contain no endosperm and an embryo consisting of only a few cells. Consequently orchids require a host specific mycorrhizal association for orchid seed to germinate. A further complication is that orchid seed viability is poor and consequently the seed is not easily amenable to long-term storage. Increasing urban and industrial expansion in NSW is causing substantial habitat destruction for a large range of plant and animal species. A number of NSW terrestiral orchids are listed as rare or endangered, many of which are yet to have recovery plans established for them. Of concern is that terrestrial orchids spend considerable time dormant underground and therefore floral surveys may inadvertently miss these valuable species. Under the NSW Threatened Species Act, the Orchidaceae family is considered a high priority. The development of a suitable long-term storage technique for rare and threatened NSW orchids species is critical for their long-term future.
Background:
The NSW National Parks & Wildlife Service (NPWS) has identified at least 20 species of orchids that will be part of a recovery process over the next few years. To date, NPWS has developed recovery plans for three terrestrial orchids species with several more recovery plans in draft form. Currently there are 19 species of NSW orchids listed as vulnerable and 28 species threatened. The Botanic Gardens Trust, Sydney (BGT) is the lead agency in NSW in ex situ conservation (http://www.rbgsyd.nsw.gov.au/). The BGT and Royal Botanic Gardens Kew (RBGK) have recently developed a partnership agreement to collect and store over the next three years at least 750 species of seed from plants across NSW. This initiative is known as ‘SeedQuest NSW’
(http://www.rbgsyd.nsw.gov.au/conservation_research/plant_conservation/nsw_seedbank/seedquest_nsw). Some of the NSW orchids will be part of this collection but without storing the specific mycorrhiza the value of the seed is questionable. Scientific studies to gain a better understanding of orchid seed biology have been conducted on a range of Western Australian species. However, little research has been conducted on species from the east coast of Australia and only a few studies have been conducted on NSW species, with most of the work remaining unpublished. Currently Elizabeth Darley, from the University of Western Sydney, in conjunction with researchers from Mount Annan Botanic Garden (http://www.rbgsyd.nsw.gov.au/conservation_research/horticulture_research), is studying a range of NSW species to identify, isolate and document the mycorrhizal associations of local orchid species. In addition studies at Mount Annan Botanic Garden have successfully isolated fungal isolates for two orchid species. These studies have been funded by several Slade Orchid Grants over the past few years. Although work has progressed in many areas of orchid biology there have been no studies in the long-term storage of orchid seed and their mycorrhizal partners. Studies by Wood et. al. (2000) highlight the need for additional research into encapsulation – dehydration – cryopreservation of orchid seed. In particular the force required for a germinating orchid seed to rupture the alginate beads can limit development. Hence a mechanism for destabilizing the alginate coating would be valuable when removing seeds from long-term storage. Further, the alginate coating may restrict oxygen levels prohibiting germination of seeds. An evaluation of the encapsulation process in relation to reintroduction schemes, in conjunction with NPWS recovery plans, would enhance the success rate of such conservation activities.
Objectives:
  1. Understand the seed biology of a range of NSW terrestrial orchid species.
  2. Develop techniques for the long-term storage of orchid seed and the mycorrhizal partner.
  3. Provide an alternate conservation tools for the survival of rare and threatened orchid species.
  4. Develop research links between local and international partners.
  5. Enable orchid seed to be included in the Millennium Seedbank programme to be banked at Kew Botanic Gardens, Wakehurst Place, UK as part of our commitment under the SeedQuest NSW project.
  6. Develop the capacity of the NSW Seedbank to effectively store NSW orchid species, through techniques such as encapsulation.
  7. Provide advice to NPWS on orchid seed biology issues in relation to recovery planning.
Collaborators:
Lotte von Richter & Faye Cairncross (Mount Annan Botanic Garden), Dr Chris Wood (Millennium Seedbank, RBG, Kew), Elizabeth Darley (University of Western Sydney), Prof. Rob Park & Dr Collin Wellings (The University of Sydney)
References:
Wood, C. B. Pritchard, H. W. Miller, A. P (2000) Simultaneous preservation of orchid seed and its fungal symbiont using encapsulation-dehydration is dependent on moisture content and storage temperature. CryoLetters. 21: 2, 125-136. 34

Figures 1 to 4 – Some of the terrestrial orchid species studied at Mount Annan Botanic Garden.

 
Figure 1. Caladenia catenata

Figure 2. Caleana major

Figure 3. Calochilus campestris

Figure 4. Diuris arenaria