RENO, NV., Oct. 14, 2002 - Grapes are tough. So tough they can handle stress — lots of it, even heavy-duty Nevada stress, according to Grant Cramer, associate professor of biochemistry in the College of Agriculture, Biology and Natural Resources and principal investigator in a four-year, $3.6 million study that seeks to determine which varieties of wine grapes will grow best in the state.
“Grapes grow like weeds,” says Cramer, and Nevada, with its dry climate, cool nights and clear sunny days, may be an untapped haven for the hardy plants. To become superior wine grapes, vines need just the right amount of sun and season to produce a perfect balance of acids and sugars, Cramer explains.
“Acids decline with hot temperatures. In California’s Central Valley, the acids decline too rapidly and you get what are called flaccid wines: sweet, but no acid to balance it out.” In contrast, New York wines have too much acid because their season is too short for the grapes to build up sugars prior to harvest, he adds.
“A region that is well suited for grapes has the right balance of sugars and acids at harvest – the acids are disappearing and the sugars are accumulating and they cross at just the right spot. As it turns out, we have a good climate for that here” Cramer notes.
But climate is not the only factor in growing great grapes. The flavor components, which determine that highly subjective human preference for a particular vintage, are a product, ultimately, of the vines’ genetic makeup. Genes code for the proteins that are involved in making plants’ cells and in making the metabolites in the cells. Lipids, sugars, amino acids and many of grapes’ flavor components are produced by the cells’ metabolism.
While several studies have shown that grapes grown in drought conditions produce superior wine, scientists still do not understand the genetic and chemical basis for this phenomenon.
Enter the gene “profilers”: Cramer and co-investigators David Schooley, professor of biochemistry; John Cushman, associate professor of biochemistry; and Pedro Mendes of the Virginia Bioinformatics Institute at Virginia Polytechnic Institute and State University are looking at the effects of drought, salinity and cold on grape production and quality by using a new, computerized technology to catalog and analyze the genes of stressed plants. During the four-year grant period, they plan to build on previous work begun in 1995 and generate 70,000 additional “expressed sequence tags” — partial sequences in a gene, not the full-length DNA gene. These tags can be used to uniquely identify a gene.
The team is using high-tech equipment at the Nevada Genomics Center, housed in the Fleischmann Agriculture Building to create “microarrays” of a set of genes. “It’s a cheaper, faster way of getting information that we can use to identify novel genes and look at gene regulation,” Cramer explains. In contrast, the U.S. Human Genome Project, being coordinated by the Department of Energy and the National Institutes of Health, is mapping the full-length gene, a more time-consuming process.
Cramer’s team will also generate new data on grapes’ proteins and metabolites. The team is testing about 4,000 plants, totaling 16 varieties of Vitis vinifera — red and white wine grapes that originated in the Mediterranean, such as Chardonnay and Cabernet Sauvignon.
Cramer hopes to reduce the risk potential Nevada grape growers will face when choosing to plant a commercial vineyard, which would use far less water than other crops such as alfalfa. Vitis vinifera, a species that produces some of the best wine grapes in the world, dies at minus 10 degrees F. Grapes that are native to Nevada, on the other hand, can survive temperatures as low as minus 25-30 F. Once his team can determine which sequences of genes affect cold resistance, it is possible that those genes could be “turned on” by genetic engineering. “This will be the work of biologists and breeders for the next century,” Cramer states. “This is the new era of functional genomics.”
October 13, 2002