Estratégias para conservação in vitro de Eucalyptus grandis x Eucalyptus urophylla

Abstract

In this work, it was evaluated the efficiency of different in vitro conservation techniques for shoots and caulinar apices from Eucalyptus grandis x Eucalyptus urophylla hybrid, a species with great economic relevance to the commercial forestry. The slow growth was the first technique used at which the shoots were submitted to two temperatures (4 °C and 8 °C) while cultured in MS medium supplemented with plant growth regulators and sucrose (0.09 M; 0.13 M and 0.18 M), under light and dark conditions. However, there was no plant regeneration coming from shoots after these treatments. Another technique tested was the cryopreservation by using two methodologies: the Droplet -vitrification and the Cryo-plate (used for the first time in eucalyptus genotype) with different exposure times to the cryoprotectant PVS2. The most effective treatment for cryopreservation of apices was the aluminium cryo-plate exposed for 60 minutes to PVS2, exhibiting 47.4% efficiency on the regeneration of cryopreserved apices. The treatments undergone to Dropletvitrification technique presented inferior results with regeneration rate up to 25%. For the shoot multiplication, both methodologies led to normal multiplication patterns after the cryopreservation. In addition to the cryopreservation methodologies, other two types of cryoprotectants were applied: PVS2 and VSL in Cryo-plate. They presented similar regeneration rates (41.8% PVS2 and 45.7% VSL), but at different times (60 minutes for PVS2 and 75 minutes for VSL). Taking these results into account is possible to conclude all treatments carried out to conserve the shoots through slow growth were inefficient in a medium-term. On the other hand, the conservation of caulinar apices by using Cryo -plates during cryopreservation process is more efficient than Droplet-vitrification in a long-term. Lastly, the Cryo-plate use with the cryoprotectants PVS2 for 60 minutes or VSL for 75 minutes is the most efficacious methodology for the studied -genotype cryopreservation.