Abstract
The relevance of Eucalyptus dunnii has been evidenced mainly for its wood quality and cold tolerance among cultivated subtropical eucalypts. However, rooting is a challenge for its propagation, particularly when adult material is involved. This study aimed to assess the mixotrophism on the in vitro elongation and adventitious rooting phases in Eucalyptus dunnii microcutting. The experimental material used was obtained from a ministumps of Eucalyptus dunnii clones. In order to evaluate gas exchange and sucrose supplementation on in vitro elongation and adventitious rooting, the experiment was prepared in a 3×4 factorial arrangements with three forms of sealing (rigid polypropylene caps with no membrane (0/M), with a membrane (1/M), with three membranes (3/M) and four sucrose concentrations (0, 10, 20 and 30 g.L-1). At 30 days in the elongation phase it was evaluated (length, number of shoots per explant, oxidation, bud vigor, pigment content, leaf area and anatomy) and rooting (length, root diameter and rooting). Results show that sucrose should be added in the culture medium for in vitro elongation and can be reduced to concentrations between 10 and 20 g.L-1. In vitro rooting requires the use of 30 g.L-1 of sucrose. The use of flasks with membranes that allow gas exchange is an effective alternative to promote the in vitro elongation and adventitious rooting of Eucalyptus dunnii microcutting.
Highlights
Eucalyptus dunnii is a subtropical climate of great importance due to its wood quality and cold tolerance among cultivated subtropical eucalyptus (Smith and Henson, 2007)
Microcuttings were inoculated under aseptic conditions, cultured for 30 days in glass vials (250 mL) containing 50 mL of MS medium, with the addition of 6 g.L-1 agar, 1 mg.L-1 indole-3-butyric acid (IBA) and 0.5 mg.L-1 of naphthalene acetic acid (NAA)
Variations according to studied characteristics, different types of sealing and sucrose concentrations used on in vitro elongation were observed at 30 days of culture with the clone of Eucalyptus dunnii (Figure 3)
Summary
Eucalyptus dunnii is a subtropical climate of great importance due to its wood quality and cold tolerance among cultivated subtropical eucalyptus (Smith and Henson, 2007). Investigation on the Eucalyptus dunnii species has increased significantly in relation to in vitro vegetative propagation (Oberschelp et al, 2015), as well as in vitro elongation (Navroski et al, 2015) and adventitious rooting (Oberschelp et al, 2015; Brondani et al, 2018). Research for improvements in the in vitro elongation phase has been intensified, aiming to obtain microstumps. Scientific studies on this field have focused on the adequacy of protocols, on the reduction of the carbon source in the culture medium, as well as knowledge of the most efficient environment for the system (Bianchetti et al, 2017)
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