Our study aims to evaluate the physicochemical mechanism involved in the adhesion of Fusarium oxysporum f. sp. albedinis (Foa) on date palm root of resistant (Aziza M) and susceptible (Boufegouss) varieties by determining their surface properties. Hydrophobicity of Date palm root and Foa was evaluated by contact angle measurement (θ_w) and free energy of interaction determination (∆Giwi). Our results showed that Foa surface is hydrophilic (θ_w = 30.57° and ΔG_iwi = 15.51 mj/m²) and has an important electron donor character (γ^- = 53,99mj/m²), whereas its electron acceptor property is low (γ⁺ = 8.95 mj/m²). Regarding date palm, the surface of sensitive variety’s root is hydrophilic (θ_w = 62.97°), while that of resistant variety is hydrophobic (θ_w = 69.50°). This character was confirmed by quantitative approach (ΔG_iwi = 6.84 mj/m² for sensitive variety and ΔG_{iwi =} -20.61 mj/m² for resistant variety). Also, it was noted that both resistant and sensitive varieties are weak electron acceptors (γ ⁺ = 0.15 mj/m² and γ ⁺ = 0.08 mj/m² for resistant and sensitive varieties respectively). The two varieties are relatively important electron donors, but the sensitive variety is more donor (γ^- = 30.5 mj/m²) than the resistant one (γ^- = 16.57 mj/m²). These results suggest that hydrophilic character and electron donor/acceptor character may be responsible for the adhesion of Foa on sensitive date palm root and therefore causes its susceptibility to bayoud disease. In contrast, the hydrophobic character of the resistant variety could explain its resistance.

Keywords: Fusarium, Date Palm, Physicochemical, Adhesion, Resistance, Sensitivity

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