A new and rapid micropropagation protocol for Eucalyptus grandis Hill ex Maiden

We developed a faster micropropagation protocol specifically designed for Eucalyptus grandis. Eucalyptus breeding programs use micropropagation protocols to obtain high quality cloned seedlings, but current protocols are excessively time consuming.The protocol has been developed in Argentina, but it can be applied in anywhere. We used nodal segments as initial explants to obtain micropropagated shoots, which were then simultaneously rooted ex vitro and acclimated in a hydroponic system. Nodal segments were cultured in a MS medium supplemented with 1 mg l-1 6-benzylaminopurine, 30 g l-1 sucrose, 1 g l-1 active charcoal and 8 g l-1 agar and incubated for four weeks at 25 ± 2°C under 16 h day photoperiod. Then, micropropagated shoots were exposed 15 seconds to 5000 ppm indol-butyric acid prior to being transferred to a hydroponic system, allowing simultaneous ex vitro rooting and acclimatization. 73 ± 9% of nodal segments grew to generate 1.73 ± 1.03 shoots per explant (length: 0.76 ± 0.44 cm). After four weeks in hydroponic system, 46 ± 4 % of micropropagated shoots developed roots, which represents an acceptable and intermediate rate of success, compared to the reported in vitro rooting rates. Our protocol allowed to obtain micropropagated seedlings in a total timespan of 8 weeks. Our results show that, by utilizing a hydroponic system, traditional protocols to micropropagate Eucalyptus can be substantially enhanced, allowing for improved production dynamics and potentially resulting in better organized seedling manufacturing facilities.