A group of Italian and French scientists have produced a high-quality draft of the genome sequence for the pinot noir grapevine, the first sequence made for a fruit crop.
The research group, called the French-Italian Public Consortium for Grapevine Genome Characterization, has made the genetic code available to the public to speed up the process of identifying the genes underlying particular traits, such as those involved in disease resistance. The group’s findings were published in this week’s issue of Nature.
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“Now people have the tools to identify the genes of importance in the grapevine,” says Jean Weissenbach, a geneticist who was part of the sequencing effort at Genoscope, in France. “They will be able to find the specific genes which confer resistance to diseases, and, in time, to understand the differences among the various types of vines.”
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The team’s analysis of the sequence shows that the genes involved in the metabolizing of tannins and terpenes–the molecules that contribute to a wine’s aroma, texture, and taste–have been selectively amplified by breeding over thousands of years.
“Mankind has selected varieties that were more interesting from their point of view, with more copies of those terpene and tannin genes appearing in successive generations,” Weissenbach says.
The researchers also found that the number of genes responsible for producing resveratrol had increased over thousands of years. Resveratrol is a compound known to extend the life span of mice and other organisms.
The information contained in the genome sequence makes the grapevine ripe for genetic engineering. Grapevines are highly susceptible to a variety of pathogens, including powdery mildew, oidium, and Pierce disease. But some varieties of grapevine resist these diseases.
Once the genes related to these diseases are identified, and disease-resistant grapevines are sequenced, the susceptible grapevine could potentially be modified by breeding or gene transfer.
“I think having the sequence of a grapevine genome is extremely useful,” says Peggy Lemaux, a microbiologist at the University of California, Berkeley. Lemaux is involved in similar research, focusing on using genetic engineering to understand and improve cereals and grasses. The grapevine project is going to require some time and work, she says, “not only identifying the disease-related genes in the grapevine, but also sequencing the pathogens to find what it is that allows them to attack.”
Vintners currently incur large costs fighting diseases like powdery mildew, mainly by using an array of chemical sprays. If a disease-resistant grape could be engineered without diminishing its quality, some vintners would welcome it.
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“We spend a fair amount of dollars … [and] time fighting powdery mildew in the vineyard through a spray schedule,” says Stephen Reustle, owner and wine maker at Reustle Prayer Rock Vineyards, in Oregon, a region known for its pinot noir. “From a general point of view, a disease-resistant pinot noir grape would be a real economic benefit to the vineyard owner.”
Still, there is reluctance among many wine farmers to use genetically modified organisms. In 2005, a proposed ban on planting or cultivating genetically altered crops divided Sonoma County, CA. Ultimately, voters rejected the ban, but similar prohibitions have been passed in Marin and Mendocino, CA.
“It’ll be a long time before we can use this,” says Steve Smit, head of vineyard operations for Constellation Wines, the purveyor of the Robert Mondavi label. “There are a lot of good arguments on both sides: you no longer have to use chemicals, but maybe you’re changing something that’s important elsewhere in the ecosystem.”
