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 critically endangered Western Australian shrub, Symonanthus bancroftii. It was necessary to screen antioxidant treatments to prevent the occurrence of lethal 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 the untreated control or other antioxidant treatments tested. Half strength Murashige and Skoog (MS) medium containing 0.5 muM kinetin and 0.25 muM benzyladenine 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 and half strength MS with no plant growth regulators, over 4 weeks. Root production was achieved with indole-3-butyric acid (IBA) and alpha -naphthaleneacetic acid (NAA) at 0.5/0.5 muM (31% rooting) and 1.0/1.0 muM (36% rooting), after four weeks. Paclobutrazol (PBZ) at 0, 3.4 (1 mg 1(-1)), 10.2 (3 mg 1(-1)), or 17 muM (5 mg 1(-1)) improved tolerance to desiccation after transfer of in vitro rooted shoots to soil. PBZ at 10.2 muM increased survival to 90% compared to 50% for those plantlets not treated with PBZ. The acclimatisation period from the glasshouse to the shadehouse was 1 week for plantlets 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 untreated controls.