Abstract: The colonisation process of olive by an enhanced yellow fluorescent protein (EYFP)-tagged Verticillium dahliae defoliating (D) pathotype derivative (VDAT-36I), and its in plantainteraction with an enhanced green fluorescent protein (EGFP)-tagged derivative of Pseudomonasfluorescens PICF7 have been monitored on/in olive tissues using a nongnotobiotic system,vibratome-tissue sectioning, and confocal laser scanning microscopy (CLSM). Isolate VDAT-36Iinvaded root cortex and vascular tissues via macro- and micro-breakages, and progressed to theaerial parts of the plant through xylem vessel cells. Strain PICF7 used root hairs as preferredpenetration site. Early and localised root surface and root endophytic colonisation byP. fluorescens PICF7 is needed to impair full progress of Verticillium wilt in olive.