In vitro propagation of Stackhousia tryonii Bailey (Stackhousiaceae): a rare and serpentine-endemic species of central Queensland, Australia

Stackhousia tryonii Bailey, a rare species whichhyperaccumulates nickel and with a potential to be exploited inphytoremediation/phytomining, is difficult to propagate via seeds. This studyinvestigated the development of a micropropagation protocol for the productionof large stocks of S. tryonii. Disinfested shoot tips andnodal buds were precultured on Gamborg's (B₅) basal medium toobtain aseptic shoots for the optimisation of the protocol. 6-Benzyl aminopurine(BAP) at 1.0 mg l^–1 produced the highest number ofshoots per explant in B₅ medium. Comparison betweenB₅ and MS media showed similar responses, but with marked influenceof BAP concentration on shoot numbers. Transfer of shoots from MS(multiplication) medium to MS medium supplemented with indole-3-acetic acid(IAA) and indole-3-butyric acid (IBA), individually or in combination, indicatedthat a combination of IAA and IBA (0.75 mg l^–1each) is required to produce roots on young shoots (75%) compared to IBA(15–45%) or IAA (0–10%) alone. This study demonstrated that by usingthis protocol, a high multiplication rate (up to 18 shoots per explant) could be produced within 4 weeks, andthey can be readily hardened (98% survival) in a glasshouse by transplantingthem into a potting mixture of sand and perlite (4:1).