LAUSR

Abstract Grapevine red blotch virus (GRBV) infection was recently identified in an Idaho commercial vineyard. Fruit quality from healthy vines (no viruses detected), and GRBV positive (infected) vines was determined for ‘Syrah’ grapes from this vineyard. GRBV infected vines produced grapes with significantly lower total sugars (2.7 g/100 g difference) and lower total anthocyanins (34 mg/100 g difference). They were also lower in a single free amino acid (tryptophan, 0.4 mg of N/kg difference), yet higher in malic acid (0.13 g/100 g difference) compared to grapes from healthy vines. No significant differences were seen in total organic acids, yeast assimilable nitrogen content, total free amino acids, total phenolics, or total tannins between the grapes of healthy vines versus those of GRBV infected vines. Overall, GRBV negatively influenced grape quality by reducing total sugars and total anthocyanins, which may indicate GRBV infection delayed grape ripening and could adversely affect wine quality.