Infection of Grapevines by Some Fungi Associated with Esca. I. «Fomitiporia punctata» as a Wood-Rot Inducer

Abstract

Inoculation experiments with three strains of Fomitiporia punctata on grapevine cv. Sangiovese and on
grafted ‘Italia’ rootstocks were carried out in southern Italy in 1992-1993. Inoculations were performed on fresh
wounds made on the spurs, branches and trunks of vines showing no symptoms of esca. The fungus developed in the
discoloured wood around the inoculation site, and caused white rot within two years. No symptoms were induced on
foliage or fruit of the infected vines, nor was there any significant difference in virulence of the strains of F. punctata.
After 2 years, re-isolation of F. punctata from the diseased woody tissues was successful, whereas no other species of
fungi suspected to act as a “precursor” of wood decay were isolated. In 1999, further experiments were carried out
with one strain of F. punctata on standing vines cv. Italia and Matilde free of any sign of wood deterioration. The
development of internal symptoms was recorded monthly. The results indicated that the cv. Matilde was less susceptible
than the cv. Italia. The first signs of spongy wood decay appeared 6 months after inoculation on both cultivars.
F. punctata was re-isolated from the infected vines, whereas no species of Phaeoacremonium or other wood-decaying
fungi were isolated from either inoculated or non-inoculated vines. These findings suggest that F. punctata behaves
as a primary pathogen, being able to cause wood deterioration and spongy decay both on adult and young grapevines
in a relatively short time, without the prior or concurrent action of other fungi.