**4. Materials and Methods**

#### *4.1. Plant Material*

Healthy 6-month-old rooted cuttings of three olive cultivars representative of different degrees of susceptibility to *V. dahliae* were used: 'Frantoio' (tolerant), 'Arbequina' (moderately susceptible), and 'Picual' (highly susceptible) [11,12]. The plants were obtained from a commercial nursery and were grown in peat moss in plastic pots (0.5 L). They were pre-conditioned in a controlled growth chamber (22 ± 2 ◦C, with a 14:10 h (light:dark) photoperiod of white fluorescent light (10,000 lux) and 60% relative humidity (RH)) for 1 month to induce active growth. During this month, plants were irrigated three times per week with 350 mL of water per plant.
