Embryogenic competence of calli and embryos regeneration from various explants of Dahbia cv, a Moroccan olive tree (Olea europaea L.)

The olive (Olea europaea L.) is an economically important species in the Mediterranean basin. Studies on the improvement of the olive using biotechnological techniques as somatic embryogenesis were always hampered by the recalcitrant aspect of its explants to regeneration in vitro. Thus, we carried out this investigation in order to test the embryogenic capacity of different types of explants of the Moroccan olive cultivar Dahbia: ovaries and stamens (taken from unpollinated flowers), radicles and cotyledons (excised from zygotic embryos) and leaves and petioles (taken from micropropagated plantlets which were maintained in vitro for four years) were cultured for three weeks on an induction medium (OMi) consisting of a basal olive medium (OM), supplemented with 25 mu M indole-3-butyric acid (IBA) and 2.5 mu M 2-isopentenyladenine (2iP), transferred to OM medium devoid of growth regulators for four weeks, and then to an olive cyclic embryogenesis medium (ECO) supplemented with 0.25 mu M (IBA), 0.44 mu M 6-benzylaminopurine (BAP) and 0.5 mu M 2iP. All the obtained calli were morphologically identical on ECO supplemented with growth regulators; they were compact and brownish and exhibited nodules on their periphery. The histological observation showed cells with embryogenic characteristics. Although, acquisition of embryogenic competence was shown on all the calli, the expression of embryogenic cells into somatic embryos were observed on the sole zygotic origin (radicles and cotyledons), indicating that, within the same cultivar and the same culture conditions, the expression capacity varies according to the explants nature.