Infection of Grapevines by Some Fungi Associated with Esca. II. Interaction among «Phaeoacremonium chlamydosporum, P. aleophilum» and «Fomitiporia punctata

Cross-inoculation experiments were designed to study the interaction among the three fungi, Phaeoacremonium chlamydosporum (Pch), P. aleophilum (Pal) and Fomitiporia punctata (Fop) most commonly associated with esca of grapevine. The experiments were carried out in southern Italy on grapevines cv. Italia and Matilde, and the inoculations were performed in January 1999 by infecting trunks (cv. Italia) and branches (cv. Matilde) through wounds. Fop, Pch and Pal were inoculated singly or in groups of two or three in all possible combinations. Pch, Pal or both were inoculated above or below the inoculation site of Fop. From the results obtained in the first eight months of experiments planned for three years, the following conclusions can be drawn. All fungi inoculated singly spread along the woody tissue and caused brown streaking downward and upward along the trunk and branches of inoculated vines. On the basis of internal symptoms, vines cv. Italia were more susceptible than those cv. Matilde; in particular, the brown wood-streaking induced by P. aleophilum was much more severe on cv. Italia. Co-infection with the two tracheiphilous species of Phaeoacremonium caused wood gummosis and discoloration, whereas the lignicolous basidiomycete F. punctata alone caused wood deterioration and decay (white rot). Severity of internal symptoms, assessed as extent and colour of the discoloured wood, varied with the growth and interaction of the inoculated fungi. The wood discoloration caused by F. punctata was not hampered by P. chlamydosporum, but it was always limited by P. aleophilum. A similar interaction was observed in vitro with cultures of the three fungi together, which showed a marked antagonistic effect of P. aleophilum against F. punctata. Although not consistent, foliar symptoms (interveinal and marginal chlorotic areas) developed within six months on ‘Matilde’ vines co-inoculated with either species of Phaeoacremonium, or within three months after a syringe containing a liquid culture of P. chlamydosporum was inserted into current-season ‘Italia’ shoots.