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

Stackhousia tryonii Bailey, a rare species which hyperaccumulates nickel and with a potential to be exploited in phytoremediation/phytomining, is difficult to propagate via seeds. This study investigated the development of a micropropagation protocol for the production of large stocks of S. tryonii. Disinfested shoot tips and nodal buds were precultured on Gamborg's (B-s) basal medium to obtain aseptic shoots for the optimisation of the protocol. 6-Benzyl aminopurine (BAP) at 1.0 mg l(-1) produced the highest number of shoots per explant in B-5 medium. Comparison between B-5 and MS media showed similar responses, but with marked influence of 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, indicated that a combination of IAA and IBA (0.75 mg l(-1) each) is required to produce roots on young shoots (75%) compared to IBA (15-45%) or IAA (0-10%) alone. This study demonstrated that by using this protocol, a high multiplication rate (up to 18 shoots per explant) could be produced within 4 weeks, and they can be readily hardened (98% survival) in a glasshouse by transplanting them into a potting mixture of sand and perlite (4: 1).