Title: Investigations of the mycorrhizal associations of Australian Bulbophyllum orchids.
Applicants: Jed Calvert & John D.W. Dearnaley
Institution: Centre for Crop Health, University of Southern Queensland, Queensland.
This study was aimed at elucidating aspects of the mycorrhizal associations of Australian Bulbophyllum orchids, of which little is currently known. The first component of the project, to isolate and identify the mycorrhizal fungi of Bulbophyllum exiguum, elisae, bracteatum, minutissimum and shepherdii, showed that these species were colonised by a variety of ascomycete and basidiomycete fungi (the latter including species of Ceratobasidium, Tulasnella and Serendipita). The main mycorrhizal fungus of Bulbophyllum exiguum, bracteatum and elisae appears to be a new species of Tulasnella mycobiont which colonised plants occurring over a range of 220km in south east Queensland. Such narrow fungal specificity may be reflective of the need for these orchids to form efficient physiological relationships with their fungal partners to accommodate the stressful abiotic conditions of the epiphytic lifestyle. Germination experiments with the Tulasnella and Serendipita isolates and seed of B. exiguum confirmed the mycorrhizal status of the mycobionts and suggested that Bulbophyllum orchids do not display developmental mycorrhizal shifts ie. the same fungi stay associated with the plants throughout their life cycles. This research has added further understanding to the field of orchid mycorrhizas, revealed novel features of the biology of Australian Bulbophyllum orchids and will contribute to their conservation.