Phenolic Responses to Esca-Associated Fungi in Differently Decayed Grapevine Woods from Different Trunk Parts of ‘Cabernet Sauvignon’

Alterations in phenolic contents were studied in Esca symptomatic (Sym) and asymptomatic (Asym) vines of ‘Cabernet Sauvignon’ based on wood conditions (healthy, HLT; necrotic, Nec; and rotten, Rot) and vine parts (head, trunk, and rootstock). In Asym vines, only Alternaria alternate was identified in Nec wood, while the HLT wood of Sym vines was colonized by Botryospaeriaceae sp. and Aureobasidium pullulans, Nec wood by Fomitiporia mediterranea, and Rot wood by Fomitiporia mediterranea and Phaeomoniella chlamydospora. Esca infection caused a significant accumulation of gallic acid, total flavanols, stilbenes (STB), and total analyzed phenolics (TAP) in all studied woods, especially in Nec wood. In Asym vines, TAP in the head increased with necrosis, but in Sym it decreased, while TAP in the trunk and rootstock of Sym showed an opposite response. The significantly highest contents of procyanidins (Pcys), catechin, epicatechin, epicatechin gallates, and Pcys dimers and tetramers were measured in HLT wood in the head and in Nec wood in the trunk of Sym vines. The significant increase of STB content was not caused only by Esca infection in HLT wood but also by necrosis in Asym vines, especially of ε-viniferin glucoside, resveratrol glycosides, and astringin. The obtained results suggest that the alteration in phenolics differed not only due to Esca infection but also due to the wood conditions and vine part, which might reflect the impact of the duration of the presence of the pathogen in different parts of the vine.