Various fungal communities colonise the functional wood tissues of old grapevines externally free from grapevine trunk disease symptoms

Background and Aims: The objective of this study was to analyse the various fungal communities that colonise functional wood tissues of old vines that did not express symptoms of grapevine trunk diseases (i.e. Esca and Eutypa dieback) in the year of sampling. Plants of the cultivar Baco Blanc a grapevine hybrid of Folle Blanche and Noah used to produce Armagnac in France were sampled. Methods and Results: Forty-two and 58-year-old vines, planted in the same vineyard, were uprooted, cut longitudinally and their functional wood tissues sampled. Culture-dependent and single-strand conformational polymorphism methods were used to compare the fungal communities colonising these wood tissues. It was shown that the fungal communities were significantly different depending on the age of the grapevines. A total of 421 fungal strains were isolated and identified by internal transcribed spacer region sequencing. Conclusions: Many grapevine trunk diseases fungal pathogens, particularly the causal agents of Esca (42-year-old vines) and Eutypa dieback (58-year-old vines), as well as numerous potentially plant-beneficial mycoparasites (e.g. Trichoderma spp.), were isolated from the functional wood tissues of old grapevines. Significance of the Study: The lack of foliar symptoms among older grapevines may reflect an 'equilibrium' among trunk fungal pathogens, mycoparasites and saprobes in the functional wood tissues of trunks.