(WSU.EDU) - Grapevine leafroll disease (GLD) has plagued vineyards for centuries, but little is known about how this virus impacts the fruit quality and actual wine produced from grapes of affected plants.

Researchers from different disciplines at Washington State University teamed up to examine virus impacts from “vine to wine.” Their study, recently published in PLoS ONE, can be found at http://dx.doi.org/10.1371/journal.pone.0149666.

Three years of wine comparisons

They made wines from red grapes from vines with GLD and wines from healthy plants to learn the effects of GLD on wine chemistry.

“In most studies we do, we use a limited number of grapes for data collection,” said Naidu Rayapati, a WSU virologist and associate professor of plant pathology. “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 GLD more of a factor in the finished wine. They replicated the tests over three years to allow for changes from warm years versus cooler years.

Warm years see smaller differences

In the final results, wines from GLD-affected grapes had significantly lower alcohol, polymeric pigments and anthocyanins (both are coloring agents in wine) compared to corresponding wines from grapes of non-symptomatic vines.

The impacts wound up being 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, and he hopes to do more research into seasonal influences for a deeper understanding of how GLD impacts vine health and fruit and wine quality. He aims to translate this knowledge for practical applications in vineyards.