Propagation and seed viability of the endangered orchid Prasophyllum correctum D.L. Jones (Gaping Leek Orchid).
Tien Huynh1 and Fiona Coates2.
1Department of Applied Biology and Biotechnology, RMIT University, Melbourne, Victoria
2School of Botany, La Trobe University, Bundoora, Victoria.
December 1999 Grant details Final Report
Summary. The Gaping leek orchid, Prasophyllum correctum D.L. Jones, is a Critically Endangered (lUCN 1994) taxon with a total population in Victoria of approximately 130 plants. P. correctum regenerates from seed, and occasionally by tuber division, but little recruitment has been observed in the wild.
Seed viability, isolation of fungal symbiont, and germinability of seed at 5 days, 90 days, 150 days, 270 days and 365 days after collection, using symbiotic and asymbiotic methods, were investigated. Future efforts to increase population size in Victoria may rely on ex situ cultivation and translocation, so that methods to evaluate the propagation potential of the taxon are required.
Results from viability tests using flurorescein diacetate (FDA) were lower overall than germinability. Triphenol tetrazolium chloride (TTC) tests were difficult to prepare and interpret, and the method was abandoned. Mycorrhizal fungus (Basidiomycetes) was isolated from P. correctum roots and effectively promoted germination of fresh (5 days old) seed (38%). However, it was not effective using 90, 150 or 270 day old seed. Germination trials using 365 day old seed were destroyed by mites. Sporulation could not be induced in culture and the fungus remained unidentified.
Asymbiotic methods were more successful overall in germinating stored seed. Although not effective on fresh seed, there was significantly higher germination compared to media inoculated with fungal culture, at 90, 150 and 270 days. However, percentage germination was relatively low (<20%). Mites also destroyed 365 day old seed used in trials.
Overall, seed viability appears to be highest immediately after collection (38%) but is significantly lower at 90 days (19%). However results were variable, and are likely to have been influenced by storage conditions of both seed and fungal culture. The literature suggests that symbiotic methods are more likely to be appropriate if plants are to be translocated. Future efforts to propagate P. correctum should use either fresh seed and cultures, or biological material stored in liquid nitrogen, to maximise viability and effectiveness.