Springfield, Mo.--Researchers at Missouri State University and the Donald Danforth Plant Science Center are working to find and suppress the genes that make grapevines susceptible to fungal diseases.

The majority of the scientists' research has surrounded two grape varieties: Norton, a hardy grapevine native to the United States that is largely resistant to powdery mildew; and Cabernet Sauvignon, a vinifera winemaking grape that is susceptible to fungal disease.

Using the two varieties, combined with existing knowledge about the genetic makeup of other plants, researchers already have been able to identify a handful of candidate genes they believe contribute to a grapevine's susceptibility to powdery mildew.

Now, the scientists are using two strategies to try and create a Cabernet Sauvignon grape that is as resistant to the fungal disease as the Norton. The first strategy, plant breeding, involves setting DNA markers that are easily spotted during genetic testing of hybrid populations. Employing this method allows researchers to quickly discern whether or not a hybrid plant has the gene that makes it susceptible to powdery mildew.

"The advantage is we don't have to wait until the plant grows up in several years," Dr. Kaszlo Kovacs, co-director for the Center for Grapevine Biotechnology at Missouri State University, told Wines & Vines. "Right away, when the plant is a seedling, we extract some DNA and know if the gene is there."

Kovacs said that when he first started studying the two grape varieties, he expected their genetic makeups to be markedly different, given that one of the strains is from France and the other from the U.S. But the DNA of plants in general, he said, is more similar than their varied exteriors would lead you to believe.

Once the research team, funded by the Missouri Life Sciences Trust Fund, mapped the plants' genetic structures, Kovacs said the grapes' genetic skeletons were nearly identical, but the two plants expressed those genes in different ways. "Certain genes are expressed much higher in Norton," he said.

The other route to achieve a more fungus-resistant Cabernet Sauvignon is achieved through gene silencing, or suppressing the expression of a gene required for powdery mildew to take hold. If just one candidate gene is altered, however, pathogens like powdery mildew often find a way to overcome that barrier.

"The approach we are trying to use is gene pyramiding, adding one upon the other, building them up, so it is much, much harder for the pathogen to break the resistance," Kovacs said. "We try to combine resistance from different sources; all this is called gain of function."

Researchers from the Donald Danforth Plant Science Center in St. Louis have been collaborating with Kovacs and his partner, Dr. Wenping Qui. The Danforth Center's principal investigator on the project, Dr. Daniel Schachtman, says grapegrowers and consumers stand to benefit from reductions in fungicide if his team's research is successful.

"There is a process of making plants naturally resistant to pathogens," Schactman said. "And this would reduce pesticides, which would be cost savings for the growers and also reduce the impact of these chemicals on the environment."

At this point, he said, the team of scientists is identifying genes that might confer resistance to the powdery mildew pathogen. The next step would be testing them to determine which gene modifications work, putting them into the grapevine for further testing and then beginning the regulatory process with grower support.

Farming of genetically modified cotton, corn and soybeans already is widespread in the U.S. and other nations. However, Dr. Schactman notes that regulatory approval for the Missouri State-Danforth Center project is at least 10 to 15 years away, assuming it is successful.

"This is basic, fundamental research," he said, "with an eye at important applications."

According to Bill Freese, a science policy analyst at the Center for Food Safety, the USDA hasn't approved a crop genetically engineered to be fungal disease resistant. "There are a lot of real stiff technical obstacles," he explained.

For now, however, Kovacs is focusing on what makes Norton so good at defending itself against disease.

"We think the resistant plant, Norton, seems to be in a state of readiness," Kovacs said. "So when the pathogen comes, it's ready to defend itself."