Conservation in the wake of myrtle rust – a case study on two critically endangered Australian rainforest plants
K. D. Sommerville
A D , P. Cuneo A , G. Errington A , R. O. Makinson B , S. Pederson C , G. Phillips A , A. Rollason A , V. Viler A and C. A. Offord A
+ Author Affiliations
- Author Affiliations
A The Australian PlantBank, The Royal Botanic Gardens and Domain Trust, Mount Annan, NSW 2567, Australia.
B Australian Network for Plant Conservation, Canberra, ACT 2601, Australia.
C Botanic Gardens, Booderee National Park, Parks Australia, Jervis Bay, NSW 2540, Australia.
D Corresponding author. E-mail: karen.sommerville@rbgsyd.nsw.gov.au
Pacific Conservation Biology 26(3) 218-229 https://doi.org/10.1071/PC19026
Submitted: 27 June 2019 Accepted: 1 December 2019 Published: 23 December 2019
Journal Compilation © CSIRO 2020 Open Access CC BY-NC-ND
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−1 sucrose, 1 µm benzyl adenine and 0.2 µm indole-3-butyric acid. Culture of R. rubescens for eight weeks on MS with 0, 5, 10 or 20 µm 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® and incubation in Preforma® plugs reduced the time to root development and significantly improved the strike rate (P = 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 4°C. 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.
Additional keywords: Austropuccinia psidii, ex situ conservation, propagation, Rhodamnia, Rhodomyrtus, seed banking, tissue culture.
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