Morgan Rosenberg, Cristina Medina-Plaza, Lik Xian Lim, Cristian Olaya, Hazel Scully, Mysore Sudarshana, and Anita Oberholster*
*University of California, Davis, 595 N Hilgard Ln, Davis, CA, 95616 (aoberholster@ucdavis.edu)

Grapevine red blotch virus (GRBV), the causal agent of grapevine red blotch disease, is of huge concern in the winegrape industry. When a laboratory test confirms that a vine has GRBV, the only solution for grapegrowers is to remove the vine and replant. Furthermore, the virus is spread by an insect vector. This leads to a massive financial burden without completely eliminating the problem. To understand the extent of the impact of GRBV in California, data was captured for two consecutive vintages, 2020 and 2021, from three vineyards in Northern and Central California. These included Cabernet Sauvignon from two sites in Napa and Merlot from one site in Paso Robles. Grapes from both healthy RB (-) (tested GRBV negative by qPCR and asymptomatic) and diseased RB (+) (tested GRBV positive by qPCR and symptomatic) were harvested concurrently when the RB (-) grapes reached 27 Brix. Basic chemical parameters, phenolic composition by RP-HPLC and volatile composition by HS-SPME-GC-MS were determined for the grapes and wines. Results showed that sugar accumulation and total phenolic, anthocyanin, and tannin concentrations were significantly reduced in RB (+) grapes and wines for both vintages, which is consistent with previous research. Additionally, sensory data has shown that RB (-) wines possess a strong alcohol hotness mouthfeel, which is directly correlated with the higher sugar content at harvest. Panelists also attributed aromas related to greater fruit ripeness, such as dark and dried fruits, to the RB (-) wines. On the other hand, RB (+) wines tended to be more bitter and had aromas related to red fruits and greenness. Most importantly, panelists could distinguish wines based on virus status, suggesting significant differences based on organoleptic characteristics.

Funding Support: USDA NIFA SCRI