Influence of propagation techniques on growth and yield of olive trees cultivars ‘Carolea’ and ‘Nocellara Etnea’ Caterina Briccoli Bati a , Gianluca Godino a , Donatella Monardo a , Vitale Nuzzo b, * a Istituto Sperimentale di Olivicoltura, C.da Vermicelli Li Rocchi, Rende, Italy b Dipartimento di Scienze dei Sistemi Colturali, Forestali e dell’Ambiente, Universita ` degli Studi della Basilicata, Viale dell’Ateneo Lucano, 10, 85100 Potenza, Italy Received 25 February 2005; received in revised form 9 February 2006; accepted 31 March 2006 Abstract 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 6m  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. # 2006 Elsevier B.V. All rights reserved. Keywords: Olea europaea L.; In vitro propagation; Own-rooted plants; Grafted plants; Oil content 1. Introduction Over the last years, the Italian olive growing has been experiencing deep changes in its production system. In the nursery sector, own-rooted plants of most cultivars are now available together with the traditional grafted plants. At present, about 60% of marketed olive plants come from own-rooted cuttings. Own-rooted plants have some advantages over the grafted ones, i.e, they: (i) provide genetically homogeneous material; (ii) require shorter stay in the nursery; (iii) have lower production costs. Thanks to the intense research activity of these last years, micro-propagated plants have been obtained also for olive (Rugini, 1984; Rama and Pontikis, 1990; Cozza et al., 1997; Leita ˜o et al., 1997; Briccoli Bati et al., 1999; Chaari-Rkhis et al., 1999; Dimassi, 1999; Roussos and Pontikis, 2002; Zuccherelli and Zuccherelli, 2002; Santos et al., 2003). Micro-propagation has a number of advantages over grafting and own-rooting: (i) the production of genetically uniform and pathogen-free plant material in a short time; (ii) the possibility of propagating cultivars difficult to obtain through own-rooted cutting; (iii) the possibility of exporting in vitro material more rapidly with no obligation to have a long quarantine period; (iv) the possibility of scheduling plantlet production closer to the market demand. Though successfully applied in different public laboratories and on various cultivars this technique is not widely diffused in nurseries yet, especially because of the high cost of some products required during the in vitro maintenance phase of explants. Notwithstanding, Zuccherelli and Zuccherelli (2002) have recently reported that different olive cultivars can be mass in vitro-propagated. Knowledge on the behaviour of micro-propagated olive plants in the field is still scarce if compared to that on plants www.elsevier.com/locate/scihorti Scientia Horticulturae 109 (2006) 173–182 * Corresponding author. Tel.: +39 0971 205263; fax: +39 0971 205378. E-mail address: nuzzo@unibas.it (V. Nuzzo). 0304-4238/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.scienta.2006.03.013