Three-Year Observation of Grapevines Cross-Inoculated with Esca-Associated Fungi

Abstract

Cross-inoculation experiments were carried out in southern Italy (Apulia) on grapevines cv. Italia and
Matilde in order to study interactions among the white rot fungus Fomitiporia punctata (Fop) and two tracheiphilous
hyphomycetes, Phaeoacremonium aleophilum (Pal) and Phaeomoniella chlamydospora (Pch), commonly associated
with esca and brown wood-streaking of grapevine. In January 1999 the three fungi were inoculated through wounds
on the trunks and spurs of cv. Italia, and branches and spurs of cv. Matilde. Pch, Pal and Fop were inoculated singly
or in groups of two or three in all possible combinations. From the results so far obtained, the following conclusions
can be drawn: 1. all three fungi are pathogenic; 2. inoculation of the above fungi on standing grapevines produces
symptoms on trunks, shoots, leaves and berries that are reminiscent of those shown by esca-affected vines in the
vineyard. In particular, symptoms in the wood (brown streaking, gummosis or “black goo”, and wood decay or white
rot), and on the leaves (various forms of chlorosis, reddening and necrosis, distortion of the lamina) and berries (black
measles) were reproduced; 3. severity of internal symptoms, assessed as length of brown streaks and intensity of
colour change of the infected wood, varied with the growth and interactions between the inoculated fungi; 4. the wood
streaking which developed after inoculation with Pal or Pch on the spurs extended to the supporting shoot or branch,
and even to the stem; 5. a non-synergistic, competitive association of the two hyphomycetes, and an inhibition of Fop
growth by Pal was observed in planta. A similar marked antagonistic effect of Pal against Fop was previously shown
to occur when examining interactions between the three fungi in vitro; 6. the wood discolouration caused by Fop was
not hampered by Pch, but it is always limited by Pal; 7. on the basis of internal symptoms, grapevines cv. Italia were
more susceptible to the esca fungi than grapevines cv. Matilde.