Development of in vitro methods for ex situ conservation of Eucalyptus impensa, an endangered mallee from southwest Western Australia

A method is described for in vitro propagation of the critically endangered 'Eneabba mallee' (Eucalyptus impensa) from southwest Western Australia. Half-strength MS medium supplemented with 0.25 mu M 6-benzylaminopurine and 2.5 mu M kinetin resulted in the best combination of shoot multiplication and shoot quality compared to other treatments. Shoots of this species tended to be very compact under in vitro conditions. Shoot length was significantly enhanced with the addition of 0.5 or 1.0 mu M gibberellic acid (A(4) isomer) when compared to basal medium (no hormone supplements) or basal medium containing only cytokinin (0.5 mu M zeatin). Up to 97.0 +/- 3.0% of shoots produced roots on 1/2 MS medium supplemented with a combination of 5 mu M indolebutyric acid and 0.5 mu M alpha-naphthaleneacetic acid. Over 70% of shoots transferred to potting mixture remained viable after 3 months. This study has significantly progressed ex situ conservation initiatives for Eucalyptus impensa.