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

Aim of the study: 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.Area of the study: The protocol has been developed in Argentina, but it can be applied in anywhere.Materials and methods: 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.Main results: 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.Research highlights: 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.Keywords: Woody plants; silviculture; nursery seedlings; rooting methods; hydroponics; acclimatization