By Clint Thompson
Grape cultivars released by UC Davis that are currently being researched by specialists at Auburn University could provide hope for farmers looking for a sustainable option in overcoming Pierce’s Disease.
Elina Coneva, an Extension specialist in the Horticulture Department at Auburn University, said UC Davis’ grape breeding program recently developed European (Vitis vinifera) grape selections with resistance to Pierce’s Disease. Studies conducted by Coneva in Alabama focus on determining the development and production potential of four of those varieties.
Three red wine grape selections were planted at the Chilton Research and Extension Center (CREC) in Clanton in 2010 and are showing promising results. One white wine selection was planted in 2017. So far, the research team has not lost one plant to Pierce’s Disease.
“From the new cultivars that have just been released, one is 94% vinifera and four are 97% vinifera. I think these will give the industry in the Southeast another boost,” Coneva said. “Our commercial growers call these cultivars game changers for Alabama and the Southeast. We can see that they open a new window of opportunities for commercial production. Our wineries can produce based off locally-sourced grapes.”
The experimental cultivars at the CREC are being monitored to determine vine phenology, cropping potential, yield efficiency, and fruit quality when trained to various trellis systems and planted at different densities.
The resistant cultivars are needed to overcome the devastating effect of Pierce’s Disease to vineyards anywhere in the U.S.
Pierce’s Disease is caused by a bacterium that is transmitted by numerous sharpshooter insects, such as the glassy-winged sharpshooters. The bacterium clogs the grape xylem and cuts off nutrient and water flow to the vines. Once infected with Pierce’s disease, vines will die within one to two years.
“We actually have pretty high populations of glassy-winged sharpshooters with the highest pressure in the southern part of the state,” Elina said. “But we have different species that are prevailing in the southern part and in central Alabama and in the north.”
Coneva said Pierce’s Disease has been devastating vinifera grapes in the Southeast for a long time. Research funds increased in the 1980s when the disease started impacting vineyards in California.
Colder winter temperatures can reduce the number of insects present as well as bacterial concentration in the plant, but recent weather data show a warming climate pattern in the southeast. This places Alabama-grown vinifera grapes under high risk for Pierce’s Disease infection.
But grape producers may not have to worry about the disease very much longer if these new cultivars continue producing promising results.
“I’m getting a lot of calls from viticulturists or vineyard owners who would like to grow those new grapes and produce higher quality of wine that’s associated with vinifera type of grapes,” Coneva said. “Currently this is the most sustainable option for the industry.”