GC–MS Analysis of Cell Wall-Bound Phenolic Compounds and Lignin Quantification in Date Palm Cultivars that are Resistant or Susceptible to Fusarium oxysporum f. sp. albedinis

Abstract

This study aimed to collect data about the interactions that occur between the date palm (Phoenix dactylifera L.) and Fusarium oxysporum f. sp. albedinis (F.o.a), the causal agent of bayoud disease. Alkaline hydrolysis was carried out using the root parietal residue of three cultivars of date palm, among which two are susceptible (Deglet Nour (DN) and Tggaza (TG)) and one is resistant (Takerbucht (TK)) to bayoud disease. Gas chromatography coupled with mass spectrometry (GC–MS) analysis revealed that p-hydroxybenzoic acid is the major phenolic compound of cell wall-bound phenolics. In uninfected palm groves, the resistant date palm cultivar contained a high level of p-hydroxybenzoic acid; however, in palm groves infested with F.o.a, a significant decrease in p-hydroxybenzoic acid was observed. In the roots of susceptible cultivars with bayoud symptoms, we noted a qualitative and quantitative increase in phenolic compounds, with a remarkable increase inp-hydroxybenzoic acid content during the infection of susceptible cultivars. We investigated lignin content in roots. An increase in total lignin content was observed in both cultivars collected from palm groves infested by F.o.a, but more accumulated in the roots of the resistant cultivar than in those of the susceptible cultivars. Our findings indicate that p-hydroxybenzoic acid plays an important role in date palm defense mechanisms against F.o.a. However, its accumulation in susceptible cultivars as a response to pathogens did not block the progression of the parasite and thus was not an effective mode of resistance. Susceptible cultivars used phenolic compounds from the benzoic series for their defense, while resistant cultivars used lignification that reinforced the cell wall.