Impact of Grapevine Red Blotch Disease on Grape Composition of <i>Vitis vinifera</i> Cabernet Sauvignon, Merlot, and Chardonnay

Grapevine red blotch disease (GRBD) is a recently recognized viral disease that affects grapevines (Vitis vinifera L.). Currently little is known about its impact on grape composition. This study focused on the impact of GRBD on grape primary and secondary metabolites (mainly phenolic compounds) of three Vitis vinifera L. cultivars during two seasons. Grapes from symptomatic red blotch diseased vines (RB (+)) mostly had lower concentration of total soluble solids (TSS) and higher titratable acidity (TA) levels when compared to grapes from healthy vines (RB (−)) at harvest. GRBD impacted grape phenolic composition by mostly decreasing anthocyanin and increasing flavonol and proanthocyanidin (PA) contents in berry skins. No major impacts were observed on seed phenolics. RB (+) grapes contained more amino and carboxylic acids, while RB (−) grapes contained more oligosaccharides, polyols, and some specific monosaccharides at harvest. The impact of GRBD on grape composition was variable and dependent on the cultivar, site, and season