In Vitro Rooting and Subsequent Survival of Two Clones of a Cold-tolerant Eucalyptus grandis × E. nitens Hybrid

Abstract

Multiple shoots of two Eucalyptus grandis Hill ex Maid. × E. nitens (Deane & Maid.) Maid. clones (GN121 and GN107) generated from axillary buds were used for in vitro rooting studies. The highest rooting rates in clones GN121 (75%) and GN107 (65%) were achieved on modified 1/4-strength Murashige and Skoog (MS) (1962) medium (Ca2+ and Mg2+ levels as for 3/4-strength MS), 0.5 μm IBA, 0.4 μm biotin, 0.2 μm calcium pantothenate, 0.04 m sucrose and 0.4% (w/v) Gelrite®. The optimal culture conditions were an initial 72-h dark incubation period followed by a 16-hour photoperiod at a photosynthetic photon flux density (PPFD) of 37 μmol·m-2·s-1 and 23 °C day/21 °C night for 7 days, after which the PPFD and temperature were increased to 66 μmol·m-2·s-1 and 27 °C day/21 °C night for 18 days. Plantlets were acclimatized with survival rates of 78% for GN121 and 58% for GN107 after 28 days. Chemical name used: indole-3-butyric acid (IBA).