Effects of chemical sterilization of the culture media, porous membranes and luminosity on in vitro culture of Eucalyptus grandis × Eucalyptus urophylla

Hybrid combinations of Eucalyptus have increased due to expansion of plantations into unconventional areas and to the search for higher quality timber. However, most of these species have difficulties surviving in vitro cultivation. Active chlorine and sealing systems are often used to reduce contamination and increase gas exchange. The aim of the present study is to evaluate the establishment, multiplication, elongation and adventitious rooting of E. grandis × E. urophylla. Two clones (C1 and C2) and four active chlorine concentrations (0.000%, 0.001%, 0.003%, and 0.005%) were tested in the establishment and multiplication phases. Three sealing forms (W/M, 1/M and 3/M) and the same four active chlorine concentrations were applied to the elongation phase. Two luminosities (dark and light) and three sealings (W/M, 1/M and 3/M) were tested during adventitious rooting. Active chlorine concentration of 0.005% led to the lowest fungal contamination rate and to the highest in vitro establishment. Active chlorine concentration of 0.003% resulted in the greatest length and highest number of shoots per explant in the multiplication phase. There were no phytotoxicity problems and the quality of plants grown in an environment with active chlorine was maintained in comparison with those grown in an autoclave. The increase in gas exchange in ventilation systems had a positive impact on the in vitro growth and development of plants.