Effect of cytokinin and inductive treatments on the regrowth and rooting of encapsulated microcuttings for olive conservation

Germplasm preservation could be considered as one of the most significant applications of encapsulation. Synthetic seeds, which are the end product of this technology, can effectively support the conservation of plant material over short, medium, and long-term periods under various temperature conditions, ranging from frigoconservation to cryopreservation systems. Suitable protocols were already identified in several fruit species, but not in olive (Olea europaea L.). Unsatisfactory levels of regrowth and conversion of encapsulated unipolar propagules (microcuttings) seem to limit the application in this species, depending on genotype traits, different rooting ability or effectiveness of inductive treatments for the differentiation of the root primordia. This work was conducted with the aim to identify a suitable protocol for the production of synthetic seeds of “Moraiolo”, widespread in Central Italy and collected in our laboratory as a pilot olive cultivar. Compared to previous studies, these experiments allowed for highlighting the influence of the nutritive conditions prior the collection of the olive microcuttings on their sprouting (regrowth) after the encapsulation in a calcium alginate matrix and sowing in aseptic conditions. A less expensive formulation of zeatin (a natural cytokinin) added to the medium during the multiplication phase allowed the improvement of the sprouting of encapsulated propagules of olive (from 30 to 67%). In addition, the effect of two different root inductive treatments (classic and innovative) positively influenced the rhizogenic ability of synthetic seeds of olive, showing the effectiveness of the innovative protocol in terms of conversion and average length of roots. In the overall evaluation of the experiment, the well-known “genotype-dependence” should not be neglected, which may at least partly account for the reduced conversion capacity (limited to 47%) influenced by the reduced rhizogenic aptitude of the “Moraiolo” cv.