IN VITRO PROPAGATION OF EUCALYPTUS PHYLACIS L. JOHNSON AND K. HILL., A CRITICALLY ENDANGERED RELICT FROM WESTERN AUSTRALIA

In vitro methods were applied to the only remaining plant of the Meelup Mallee (Eucalyptus phylacis), a critically endangered species from the southwest of Western Australia. Shoot explants were initiated into culture using a 1/2 MS [Murashige and Skoog basal medium (BM) for all experiments] liquid medium supplemented with 1% (w/v) activated charcoal, which was replenished twice daily, followed by transfer of explants to agar medium supplemented with 0.5 mu M zeatin. Explants were cultured under low intensity lighting (PPFD of 5-10 mu mol m(-2) s(-1)) to minimize blackening of tissues, and some explants were induced to produce nodular green calluses in response to BM supplemented with 5 mu M thidiazuron. Nodular green calluses were induced to form adventitious shoots following transfer to medium supplemented with 0.5 mu M zeatin and 1 mu M gibberellic acid, A(4) isomer (GA(4)). Development of shoots was completed on 1 mu M zeatin+0.1 mu M 6-benzylaminopurine (BA) in vented culture tubes. Regenerated shoots were sequentially cultured on medium containing 0.5 mu M zeatin+0.2 mu M indoleacetic acid (IAA) followed by either 0.5 mu M zeatin+1 mu M GA(4) for shoot elongation or 1 mu M zeatin+0.5 mu M IAA to optimize shoot growth. Rooted microshoots were produced after 4 weeks on 5 mu M indolebutyric acid (IBA) and survived acclimatization and transfer to potting mixture.