Résumé
Phenolic compounds are associated with the olive tree resistance to the leaf-spot disease caused by Spilocaea oleaginea were studied in different resistant, susceptible and intermediate cultivars. The HPLC analysis highlights 33 phenolic compounds distinguished according to their chromatographic and spectral characteristics into five phenolic families (hydroxycinnamic derivatives, flavonoids, verbascoside derivatives, tyrosol derivatives, oleuropein derivatives). The phenolic extract of the olive-tree is dominated by ten major compounds identified as rutin, luteolin-7-glucoside, oleuropein, versbacoside, tyrosol, apigenin and four other phenolic compounds not completely identified (oleuropein derivative, hydroxycinnamic derivative and two flavonol monoglucosides). No qualitative difference was observed between cultivars. However, the principal components analysis highlights two multifactorial components distinguishing the various cultivars according to their behaviour to the disease. The first component, identified as oleuropein aglycone, a hydroxycinnamic derivative and a flavonol monoglucoside contents, clearly distinguished the resistant cultivars from the susceptible and intermediately resistant cultivars. The resistant cultivars contain higher contents. The second component, identified as tyrosol derivative and an oleuropein derivative contents, distinguished the susceptible cultivars from the intermediately resistant cultivar which presents the highest contents. The role of these phenolic compounds in the defense and their use as biochemical markers in olive-tree resistance to S. oleaginea is discussed