Oxidative stress in olive in vitro culture: effects of organized development and mass propagation of Biancolilla and Cerasuola cvs.

The in vitro culture of olive explants very often results in poor growth and reduced proliferation of axillary buds. Many different factors have been considered and in many cases the unusual, for this species, surrounding environment has been held responsible for the scarce results obtained. Recently oxidative stresses have also been investigated and among the different factors involved, wounding, sterilisation, nutritional components and culture environment were claimed as main stress-inducing agents. This experiment reports on a preliminary study on two important Sicilian varieties, Biancolilla and Cerasuola, aiming to find the existing relationships among olive explant growth and proliferation and the different factors of stress. A second goal was to to find the best nutritional medium and optimise the explant-surrounding environment to reduce at the minimum level the various (oxidative) stressing factors. The effects of two standard media OM and MSM, respectivey added with sucrose or mannitol, were compared. Results point out that growth parameters such as lenght, node mumber, fresh weight of shoots and basal callus-tissue production are strictly related to the carbon source present in the medium. A strong oxidative stress component is acting in olive explants cultured on sucrose and the capacity to counteract the damaging effects of oxidative stress is mainly linked to the peculiar antioxidant cellular machinery of each cultivar, In cv Biancolilla the utilization of OM media induces greater stress conditions as highlighted by strong variations in some enzyme activities and reduced growth.