Influence of propagation techniques on growth and yield of olive trees cultivars ‘Carolea’ and ‘Nocellara Etnea’

The vegetative and productive performance of micro-propagated olive plants in comparison with grafted and own-rooted plants was evaluated in southern Italy. Two cultivars of Olea europaea L. ‘Carolea’ and ‘Nocellara Etnea’, were planted in 1997 at two-row spacings: 6 m × 3 m and 6 m × 6 m. Percentage of flower bud differentiation, fruit weight, yield, pruning material and trunk diameter were measured on each plant of the experimental plot. Plants came into flowering the second year after planting with significant differences between cultivars. Micro-propagated ‘Nocellara Etnea’ plants came into bearing as early as the second year, whereas grafted plants had no bearing. Eight years after planting, cumulated yield of ‘Nocellara Etnea’ plants was almost double as compared to the ‘Carolea’ plants. Yield from micro-propagated plants was slightly higher with respect to grafted plants in ‘Nocellara Etnea’, but fruit weight was significantly lower. Micro-propagated ‘Carolea’ plants have shown a similar percentage of flower buds but a very low cumulated yield in the period of the trial, due to poor fruit set. In general, vegetative growth was significantly higher on plants with lower crop level. Our results have shown that micro-propagated plants did not exhibit any juvenile trait as, for instance, delay in flowering. In vitro propagation can thus be a rapid and a powerful olive propagation technique. Further investigations are however necessary to check if the main phenological differences observed (average fruit weight and poor fruit set) are somehow due to genetic modifications induced by in vitro propagation.