PROSSER Grapevine leaf roll disease has plagued vineyards for centuries, but little is known about how this virus impacts the fruit quality and actual wine produced from grapes of effected plants.
Washington State University researchers examined virus impacts from “vine to wine.”
Their study involved making wines from red grapes from vines with disease and from healthy plants.
“In most studies we do, we use a limited number of grapes for data collection,” virologist and associate professor of plant pathology Naidu Rayapati said. “This time, we harvested 750 to 800 pounds from infected vines and an equal number from healthy vines, all donated by a generous grower.”
The grapes were harvested at different points in the season to measure whether early or late harvesting made the virus more of a factor in finished wine. They replicated the tests over three years to allow for changes from warm years versus cooler years.
In the final results, wines from virus-affected grapes had significantly lower alcohol and less color compared to wines from grapes of healthy vines.
The impacts were more pronounced during cooler growing seasons than in warmer seasons.
“We think that’s because grapes mature much faster in warmer seasons and don’t have as much time to be affected by the virus,” Rayapati said.
That’s just a hypothesis at this point, he said.
He hopes to do more research into seasonal influences for a deeper understanding of how the virus impacts vine health and fruit and wine quality.
Those assisting with the Prosser research project included Jim Harbertson with the university’s wine program in Richland.
Harbertson cautioned that it’s unlikely a vintner would ever make a wine with grapes from 100 percent virus-affected vines.
The research helps show that a virus can impact more than just the amount of grapes produced and harvested.