Clonal microplant production of <i>Corymbia maculata</i>: effect of chemical sterilisation, plant growth regulator, gas exchange, activated charcoal and lighting

Abstract

Corymbia maculata stands out for its resistance to biotic and abiotic stress and for its high-density wood, which is ideal for sawmills, sleepers, posts,  firewood and charcoal. In vitro culture techniques can be used for large-scale clonal microplant production, given the difficulty in adventitious rooting via  cutting or mini-cutting techniques. The aim of the work was to evaluate the in vitro multiplication, elongation and adventitious rooting stages of  Corymbia maculata based on chemical sterilisation of the culture medium, plant growth regulators, gaseous exchange, activated charcoal and growth  room lighting. Supplementation of active chlorine in culture medium reduced fungal and bacterial contamination. The best result for the in vitro  multiplication stage was observed in the absence of active chlorine and 0.5 mg l −1 benzylaminopurine (BAP). In vitro shoot elongation in culture medium  supplemented with 0.5 mg l −1 α-naphthaleneacetic acid (NAA), 0.001% or 0.003% active chlorine, and vessels sealed with a rigid polypropylene lid with one or three membranes was the most suitable. Glass flasks with porous membrane lids allowed gaseous exchange and favoured elongation and  adventitious rooting. Microshoots treated with indole-3-butyric acid (IBA) for 48 h (pulse effect) in the absence of light and activated charcoal in the  culture medium is recommended for in vitro adventitious rooting of Corymbia maculata.