Vegetative response to Verticillium dahliae of italian varieties of olive (Olea europaea L.)

Verticillium dahliae, the causal agent of vascular wilt, is a cosmopolitan pathogen of olive (Olea europaea L.). Italy is a traditional oil-producing country and its olive growing system is characterized by hundreds of regional varieties. They are widely employed for yielding oils protected by geographical indication systems of the European Union. The aim of this study was to evaluate the influence of V. dahliae on the vegetative growth of young, own-rooted olive plants under natural environmental conditions. Specifically, we analyzed differences in stem elongation, number of leaves and stem diameters in eight local varieties of the Campania region of Italy, plus a reference national cultivar, following artificially infection with a non-defoliating pathotype. Multivariate analysis indicated that a distinction in vulnerability among cultivar can be made considering the inhibitory effect of the fungus on stem extension growth, while the other parameters are less influential. Our work also illustrated the variability in some vegetative parameters among the Campanian germplasm and its influence on the inhibitory effect of the pathogen. Further studies will have to analyze the mechanisms connecting the morpho-physiological alterations with the pathogen invasion of the host tissue.