In vitro cold storage of cork oak shoot cultures

A simple system for in vitro conservation of cork oak shoot cultures (Quercus suber L.) is described. Cultures were stored in vitro on multiplication medium at 5 +/- 1 degrees C without an intervening subculture for two years. The viability, multiplication rate and shoot elongation were evaluated after storage under dark and light conditions. Culture viability was negatively affected by light. In contrast, 50% of cultures survived after two years of cold storage in the dark. Multiplication rate of dark-stored cultures was similar to the controls, and shoot elongation was significantly higher. Although the assessment of multiplication rate/shoot elongation is done at the end of the first multiplication cycle, we observed that at least in some species such as Quercus suber, it is advisable to study the responsiveness of cultures during the first three multiplication cycles following storage. The rooting capacity of shoots produced from dark-stored cultures was similar to non-stored controls. Cultures stored for 6, 12 or 24 months without subculture have similar responsiveness as the ones subcultured monthly. The storage of cultures at 5 degrees C in the dark appears to be a promising technique for medium-term conservation of cork oak germplasm.