Oxidative browning in 'Koroneiki' olive explants as influenced by oxidative enzyme activities and endogenous phenolic compounds

Shoot tips and single-node explants from glasshouse and field growing 'Koro neiki' olive trees were assayed for their browning potential at the establi shment stage in vitro, during the growing season. Measurements of the total phenol content, the total o-diphenol content, polyphenoloxidase and peroxi dase activity were conducted, to determine the relationship of these factor s to the browning of explants. High positive correlation coefficients were found between total phenol, o-diphenol content and polyphenoloxidase activi ty with the browning percentage of olive explants. Shoot tips from both sou rces of plant material exhibited higher browning rates together with higher total phenol, o-diphenol content and polyphenoloxidase activity than singl e node explants. Explants deriving from trees growing in the glasshouse pre sented higher survival rates and lower values of the three factors mentione d before, than the corresponding explants from field growing trees. Single nodes from glasshouse olive shoots proved to be superior to all other expla nts during the establishment stage, concerning the survival rate, as they p resented the minimum phenol content and polyphenoloxidase activity.