Micropropagation of Eucalyptus grandis × E. urophyUa AEC 224 clone

Genetic transformation systems require protocols that allow regenerating transgenic plants from transformed tissues. This study aimed to establish a protocol for indirect organogenesis in leaf explants of a Eucalyptus grandis x E. urophylla AEC 224 clone. During callogenesis stage, several concentrations of NAA and then NAA or 2,4-D combined with TDZ were tested in JADS culture medium for 30 days, followed by subculture of the explants in the regeneration medium, containing 5.0 μM BA and 0.5 μM NAA for another 30 days. In these media, the explant oxidation rate was high （95 %）. Thus, in order to reduce oxidation, different ;culture media were compared： WPM, MS, JADS and modified QL, followed by explant transfer onto regeneration medium. The highest percentage of regeneration and the lowest oxidation rate were achieved on WPM medium. Then, NAA and 2,4-D were tested in combination with TDZ and also TDZ and BA combined with NAA in WPM medium. The most efficient culture media in terms of shoot regeneration were WPM supplemented with 0.25 μM TDZ and 0.1μM NAA during 30 days for callus induction and then with 5.0 μM BA and 0.5 μM NAA for another 30 days. This protocol yielded a regeneration rate of 43 %, with a low oxidation of tissues. A rooting experiment was conducted using half strength MS medium and comparing three concentrations of IBA （2.46, 4.90 and 7.35μM）. The highest rooting percentage （35 %） was obtained on medium containing 2.46μM IBA. Once the shoots were rooted, acclimatization in a greenhouse was not challenging and plant survival reached 100 %.