In Vitro Establishment and Maintenance of Culture Lines with Differentiated Somatic Embryogenesis Capacity in Olive (Olea europaea L.)

Somatic embryogenesis (SE) is a powerful biotechnological tool for large-scale clonal plant propagation. However, most woody species exhibit a recalcitrant response. Olea europaea L., a highly valuable tree crop, is among these recalcitrant species. Unravelling the molecular mechanisms underlying SE efficiency in O. europaea is, therefore, essential. Access to embryogenic lines with contrasting capacities for somatic embryo differentiation is a key requirement for such studies. Mature fruits of olive cultivars ‘Galega Vulgar’ and ‘Arbequina’ were collected from open-pollinated orchard-grown plants, and various explants taken from zygotic embryos were used to establish SE. A differentiated response was observed both within each cultivar and between cultivars, with cv. ‘Arbequina’ showing the highest embryogenic induction, particularly when radicles were used. Secondary SE was successfully established for both high- and low-efficiency lines, providing valuable material for future molecular studies. Somatic embryo conversion into plants, a key indicator of embryo quality, was successfully achieved in both cultivars. Flow cytometry analysis revealed a high degree of chromosomal stability. This study presents a reliable procedure to obtain and maintain distinct embryogenic responses in O. europaea, identifying lines with both high and low embryogenic efficiency that can serve as model systems for future molecular investigations.