silica particle size of 5 m (Tosoh Bioscience, Lyon, France); mobile phase was used at a flow rate of 0.7 mL min−1 and was constituted of an isocratic solvent composed of 98% H3 PO3 HPLC grade
at 0.1% in H2 O (v/v) and 2% of CH3 CN HPLC grade. Calibrations were made with standard organic acids from Sigma–Aldrich kit N◦ 47264 (Sigma–Aldrich, L’Isle d’Abeau, France). Total free thiols
were also assayed in lyophilized root exudates using Ellman’s test and reagent (DTNB) as described in Bulaj et al. (1998). Shoot and root dry biomass were measured in mg after drying plants for 72 h
at 60 ◦ C. Relative gain or loss of biomass (expressed as %) was calculated compared with controls as reported in Duponnois et al.(2011). Aliquots of dried plant tissues (shoot or root) were collected for mineral analyses, which were performed by ICP-OES as reported in Perrier et al. (2006a,b). Ergosterol is the major sterol in most fungi and is either absent or a minor component of higher