No abstract

We investigated ex situ conservation options for two Australian rainforest species severely affected by myrtle rust in the wild -Rhodamnia rubescens (Benth.) Miq. and Rhodomyrtus psidioides (G.Don) Benth. Both species were successfully initiated into tissue culture though the rate of contamination was high and not significantly improved by the disinfection techniques tested. Explants surviving initiation grew well on Murashige and Skoog medium (MS; pH 6.0) with 30 g L À1 sucrose, 1 mM benzyl adenine and 0.2 mM indole-3-butyric acid. Culture of R. rubescens for eight weeks on MS with 0, 5, 10 or 20 mM indole-3-butyric acid resulted in root production for some plantlets, and successful transfer to potting mix; no significant differences in root production among treatments were detected. Both species were successfully propagated by semi-hardwood cuttings with strike rates of 0-67% for R. rubescens and 0-75% for R. psidioides. For R. rubescens, pretreatment of cuttings with Zaleton Ò and incubation in Preforma Ò plugs reduced the time to root development and significantly improved the strike rate (P ¼ 0.001). R. rubescens seed proved to be orthodox and suitable for standard seedbanking; R. psidioides seed proved to be freezing sensitive but suitable for storage at 48C. As the two species now produce few viable seeds in the wild, however, conservation by seedbanking will first require the establishment of a seed orchard from vegetatively propagated plants. We recommend swift action to conserve species in the Pacific similarly affected by myrtle rust before their growth and reproductive capacity are seriously diminished.

The identity of a population of eucalypts from Howes Swamp Creek in the eastern part of Wollemi National Park in New South Wales has remained unresolved for over 35 years. Despite several workers inspecting both the site and the trees growing there over this period, little consensus has been achieved on its taxonomic status. Various suggestions have been made that the entity was a new species with affinities to Eucalyptus dalrympleana, E. viminalis or E. bridgesiana, and at one time the unpublished manuscript name E. ‘wollemiensis’ was used. Because of the perceived small population size and threats posed by wildfire and other factors, the entity phrase name E. sp. Howes Swamp Creek (M.Doherty 26) was listed as an endangered taxon in both Commonwealth and State threatened species legislation. Our investigations over the last few years, involving field, seedling, and herbarium studies, have determined the original reference specimen designated for the phrase name is E. bridgesiana, and that the population from which the specimen was gathered comprises a hybrid swarm of E. bridgesiana × E. viminalis. Both parent species are present at the site, although the former species is seemingly very rare there. We recommend that E. sp. Howes Swamp Creek be removed from threatened species legislation, and that the names E. sp. Howes Swamp Creek (M.Doherty 26) and E. ‘wollemiensis’ ms be considered nomenclatural synonyms of E. bridgesiana.