Winegrapes Face Trials in Alabama
Researcher tests disease-resistant vinifera from California's UC Davis
As in every other state, interest in winemaking and grapegrowing is expanding rapidly in Alabama. The center of the Bible Belt, Alabama is one of the last places most people would expect to find wineries, but there are a dozen in the state, and more than 100 small vineyards.
Unfortunately, its climate makes Alabama hostile to vinifera grapes, so growers there depend on Muscadine (vitis rotundifolia, such as Scuppernong), other native grapes, French hybrids or other fruit other than grapes.
The problem is that Pierce’s disease is caused by Xylella fastidiosa, which clogs the xylem of many grapevines and other plants, starving them for water and killing them in a few years. Local native grapes like Muscadine are resistant to PD, but, although popular among locals, Muscadine wine is an acquired taste. Some other grapes such as Norton, which is apparently a hybrid of native Vitis aestivitis with a touch of vinifera, are also PD-resistant, and are grown by some Alabama growers as well as others in the southeast and central states.
The vines planted in Auburn by researcher Dr. Elina Coneva come from work conducted by Dr. Andy Walker at UC Davis. Walker is breeding hybrid vines that are primarily vinifera with a small element of Vitis arizonica, a native of the southwest and Mexico that is resistant to PD. These vines reportedly taste like vinifera, without the wild or foxy flavors found in hybrids of vinifera and native American labrusca grapes.
Demand for vinifera
Coneva planted vines that are 87.5% Vitis vinifera with the rest arizonica. The vines are from Chardonnay and Syrah parents. Coneva says the demand for vinifera grapes is very high among Alabama wineries, and she’s planted a number of experimental vineyards across the state.
She planted Walker’s vines at Auburn's Chilton County Research and Extension Center near Jemison in the center of the state, which she said has very high PD pressure from a number of sharpshooter leafhoppers that carry the disease. She told Wines & Vines that growing grapes in southern Alabama near the Gulf of Mexico is very challenging, while the hills and even mountains of northern Alabama are more promising.
At the experimental station on Sand Mountain, a huge 1,500-foot-high sandstone plateau in northeastern Alabama that’s the coolest part of the state, Coneva is testing other grapes including Muscadine and various French-American hybrids. She’s also testing table grapes developed by the University of Arkansas.
The Alabama Wineries and Grape Growers Association raised money to combine with funding from Auburn University to conduct the experiments. Coneva is an assistant professor in the horticulture department and an extension specialist who works with farmers on small fruit crops and berries.
Jim Kamas at Texas A & M is also testing the same set of selections.
If the vines succeed, they could lead to far more grapegrowing across the eastern and southern United States. The results should also lend validity to Walker’s work, which is primarily directed toward improving California viticulture.
Update on Walker's work
Walker reported that he made wines from the next-generation 94% vinifera (the vines Coneva received were 87.5% vinifera) last year and will be evaluating them soon.
Walker also made wines from these in 2009 and he reports that they were very good with no hybrid character (typical blue purple pigments and herbaceous aromas).
In addition, he produced about 2,000 seedlings of the generation beyond that (97% vinifera) last year; many will fruit for the first time this summer/fall. He said, “I hope to select types for commercial release from the 97% vinifera generation.”
Walker notee that although many native vines are resistant to PD, he has focused his research on the arizonica resistance, because it's controlled by a single gene. “We have genetic markers to the resistance that has allowed us to move very rapidly through the generations on a two-year cycle and have half of all the progeny with PD resistance.”
He added that the research has used other resistance sources too, including Vitis aestivalis, but their resistance is controlled by many genes and effective genetic markers for resistance are not yet known. “With multi-gene resistance, there are relatively few resistant progeny to select from each generation, so the chances of finding the ‘best’ ones are much lower.” He continued, “We are looking at several other resistance sources, but we do not have advanced (greater than 90% vinifera) generations yet.”