Micropropagation and in vitro rejuvenation of Eucalyptus cloeziana F. Muell.

Micropropagation is an important tool for the propagation for recalcitrant species, like Eucalyptus cloeziana. This is a first reported about a complete study of the E. cloeziana, it includes the vegetative rescue protocol of mature trees, its micropropagation up to the implementation of a mini-garden and clonal micro-garden and evaluation of adventitious rooting of their propagules. The in vitro rejuvenation of E. cloeziana genotypes (03, 05, 06, 13 and 15), over 21 successive subcultures, was evaluated by comparing minicutting and microcutting techniques and the efficiency of this biotechnological tool for cloning of the mature trees. The results provide evidence of the in vitro rejuvenation occurring in the mature E. cloeziana trees during micropropagation, leading to increases in the multiplication ratios of the microstumps of three genotypes (03, 05 and 15). The survival and callogenesis percentages of the mini and microcuttings of E. cloeziana were higher than 80% upon exiting of the greenhouse (30-days old) in the three cutting times. The results suggesting that factors beyond tissue maturity influence the adventitious rooting of the E. cloeziana because minicuttings and microcuttings of the 05 and 13 elite genotypes exhibited rooting percentages lower than 20%. These findings provided a theoretical basis for realizing the micropropagation of the epicormic shoots of the mature trees and, subsequently, its in vitro rejuvenation by axillary bud proliferation.