Innovative protocol for "ex vitro rooting" on olive micropropagation

The commercial micropropagation of olive trees is currently limited by the production cost. An ex vitro method for olive microshoot rooting could reduce both the production cost per plant and the propagation time. In this study a successful ex vitro rooting protocol tested on seven olive cultivars is reported. The explants of cv. Maurino were collected from fifth, sixth, and seventh proliferative subcultures carried out on MSM medium, while for the other cultivars the explants were collected from only seventh proliferative subculture. Continuous light during the rooting phase was a prerequisite for the success of the ex vitro protocol. The best source of microshoots for a high rooting percentage was the seventh proliferative subculture. Cvs. Coratina, Maremmano, Maurino, Picholine, and S. Francesco showed high rooting percentages with a range of 62-76%; whereas for cvs. Correggiolo and Frantoio the experimental conditions need to be optimised. Up to 90% of the rooted microplants survived, and continuous growth of shoots was subsequently observed. The proposed protocol can be easily applied to several different olive cultivars to produce microplants by commercial laboratories. The approach makes olive micropropagation in the nursery industry both possible and profitable.