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Arbuscular Mycorrhizal Fungi (AMFs) are known as a symbiotic microorganism which ameliorates growth and tolerance against stressful conditions of their host plants. It is characterized by morphological, physiological and biochemical events that are controlled by the interaction of both plants and fungus. The aim of this research was to evaluate the intensity (M%) and the Arbuscules abundance (A%) of mycorrhizal infection with Glomus intraradices in olive (Olea europaea L.) tree roots of five Tunisian local cultivars (cvs Oueslati, Meski, Jarboui, Chemlali and Chetoui). After 2 weeks of acclimatization in a greenhouse, the olive plantlets were inoculated with “G. intraradices”. The estimate of percentage of root colonization was calculated using an adequate method. This method consists of putting fragments of colored roots from each cultivar and observing them in a light microscope. These fragments were noted in a grid based on a scale class. Differences obtained in values were detected in all cultivars. This paper suggests the presence of cultivar-dependent differences in both the M% and A% that can be modified by AM fungi as well as by its interaction with olive roots. Results confirm also that oueslati cv has the best compatibility with G. intraradices. These findings open up many opportunities for mycorrhiza inoculation in the oleaster plants production in Tunisia. Key words: Olea europaea L., Glomus intraradices, arbuscules, Oueslati cv.

We evaluated the potential of sap flow values estimated from records with the heat dissipation method for irrigation in an olive orchard (Olea europaea L, cv. Meski) near Enfidha, Tunisia. Trees were cultivated at 7 × 7 m spacing. Two drip irrigation treatments were imposed using the sap flow and the FAO methods. The two treatments were irrigated by 100% of crop evaptranspiration (ETc). T1: ETc measured by the sap flow method and T2: ETc estimated by the FAO method. Sap flow, leaf and stem water potentials, leaf photosynthetic activity, stomatal conductance and transpiration rate were recorded in representative trees from both treatments, during the full irrigation season from April to August. Results showed that the irrigation dose calculated from T2, based on FAO method compared to the T1, based on sap flow decreased by about 25%. Under T1 irrigation scheduling strategy, the daily transpiration decreased by 20% and consequently the water potentials were decreased significantly. Infect, olive trees under T1 were moderately stressed and subsequently leaf gas exchange parameters were affected by about 15%. Key words: Sap flow, water potential, leaf photosynthetic activity, olive tree, Olea europaea irrigation scheduling.