Micropropagation of the critically endangered western australian species, Symonanthus bancroftii (F. Muell.) L. Haegi (Solanaceae)

A micropropagation protocol was developed for the conservation of the criti cally endangered Western Australian shrub, Symonanthus bancroftii. It was n ecessary to screen antioxidant treatments to prevent the occurrence of leth al browning of explants upon excision. Potassium citrate and citric acid (0 .1% w/v in a 4:1 ratio) prevented oxidative browning and was superior to th e untreated control or other antioxidant treatments tested. Half strength M urashige and Skoog (MS) medium containing 0.5 muM kinetin and 0.25 muM benz yladenine produced three-fold multiplication compared to 1.75x, 1.5x, 1.8x and 1x multiplication for 2.5 muM kinetin + 0.25 muM benzyladenine, 0.5 muM kinetin + 5 muM gibberellic acid, 1 muM kinetin + 3 muM gibberellic acid a nd half strength MS with no plant growth regulators, over 4 weeks. Root pro duction was achieved with indole-3-butyric acid (IBA) and alpha -naphthalen eacetic acid (NAA) at 0.5/0.5 muM (31% rooting) and 1.0/1.0 muM (36% rootin g), after four weeks. Paclobutrazol (PBZ) at 0, 3.4 (1 mg 1(-1)), 10.2 (3 m g 1(-1)), or 17 muM (5 mg 1(-1)) improved tolerance to desiccation after tr ansfer of in vitro rooted shoots to soil. PBZ at 10.2 muM increased surviva l to 90% compared to 50% for those plantlets not treated with PBZ. The accl imatisation period from the glasshouse to the shadehouse was 1 week for pla ntlets treated with PBZ compared to 4 weeks for plantlets without any PBZ. PBZ at 3.4 muM increased the number of roots per shoot compared to untreate d controls.