Effect of Extracts from Phoenix dactylifera L. Rachis on Fusarium oxysporum f. sp albedinis Using Direct Bioautography

In this study, eight date palm (Phoenix dactylifera L.) cultivars were used for antifungal tests on Fusarium oxysporum f. sp. albedinis (Foa), the causal agent of Bayoud disease. The extracts were obtained from the rachis using four solvents (methanol, ethyl acetate, dichloromethane, hexane). The antifungal tests were realized using direct bioautography. The choice of cultivars was based on their character to Foa (resistant, tolerant, or sensitive). The antifungal effect was mostly represented by dichloromethanic extracts (seven out of nine inhibition zones). The best results were represented by dichloromethanic extract of the cultivar 'Bent-Cherk' rachis (6.50 +/- 1.41 mm) and ethyl acetate extract of the cultivar 'Rotbi' rachis (6.00 +/- 1.41 mm). Taking in consideration that extracts were obtained from the same species, the date palm cultivars presented some similarities concerning some inhibition zones. From the non-correlation between cultivars character (against Foa) and direct bioautography results, the natural defence mechanism, in vivo, against Foa is not specifically related to certain molecules or class of secondary metabolites (polyphenols, etc.). The difference between resistant, tolerant and sensitive cultivars is mostly related to mechanism of action (response time, compounds concentration).