Efficient plant regeneration from seedling explants of two commercially important temperate eucalypt species -: Eucalyptus nitens and E-globulus

A reliable and reproducible method for plant regeneration in vitro of two important temperate eucalypts, Eucalyptus nitens and E. globulus, has been developed which utilises seedling explants. Highly regenerative callus was obtained from individual cotyledon and hypocotyledon explants of both species following cultivation on Murashige and Skoog's (MS) basal nutrient medium supplemented with 30 g l(-1) sucrose, 5-10% (v/v) coconut water, 0.8% agar, 1 mg l(-1) alpha-naphthalene-acetic acid (NAA) and 0.5 mg l(-1) N-6 benzylaminopurine (BAP). Shoot differentiation was observed 7-8 weeks after transfer of callus onto regeneration medium containing 0.5 mg l(-1) NAA and 1 mg l(-1) BAP. In a few instances, direct shoot regeneration occurred without an intervening callus phase in both species. The frequency of plans regeneration was higher for callus derived from hypocotyl segments (30-35%) compared to cotyledonary explants (20-25%) though the average number of shoots per cotyledonary explant was generally higher than for hypocotyl explants. Somatic embryos were observed occasionally in E. nitens, arising from the surface of organogenic callus. Organised structures closely resembling somatic embryos were also observed in E. globulus. Regenerated shoots (30-40%) of both species could be rooted in modified MS media containing indole-3-butyric acid (IBA) and plantlets were successfully transferred to soil. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.