Chardonnay is among the most popular and recognizable wines in the world. The grape’s genes essentially have been passed down from a single plant in eastern France centuries ago. This genetic consistency can be seen as a good thing, as it keeps the grape recognizable. But its genes are also responsible for how it reacts to the environment, including the pests and diseases common to any vineyard.
One such global scourge is what’s known as “downy mildew,” a fungus-like pathogen that can rot fruit and strip a plant’s leaves so its grapes can’t produce enough sugar to ferment into good wine.
In a vine’s native region, the plant may have developed a natural resistance to downy mildew and other diseases. But when winemakers plunk ancient varieties in new wine regions, the vines may be especially vulnerable to local plagues.
One example? New Jersey. The state may not be especially known for wine, but production has ramped up in recent years. A major issue is New Jersey’s hot and humid summers, a perfect recipe for rot.
“Every vineyard in New Jersey is dealing with downy mildew,” says Peter Oudemans, a plant pathologist at Rutgers University. “It’s a common and pretty devastating disease.”
Downy mildew may get even worse as climate change alters wine regions around the world.
For now, both conventional and organic farmers keep their vines disease-free through a combination of practices like pruning and pesticides.
In New Jersey, winegrowers spray fungicides 6 to 12 times a season to control downy mildew, according to the New Jersey Center for Wine Research and Education. But a new technique, CRISPR (short for Clustered Regularly Interspaced Short Palindromic Repeats), may allow scientists to tweak the genes of Chardonnay to become resistant to downy mildew.
But there’s another option. Chardonnay fans may not like it, but why not ditch the grape and look for new local varieties?
“My hope is that we can engineer the plant internally to cut down infection,” says Rong Di, a plant pathologist and molecular biologist at Rutgers. Her team is testing CRISPR on a grape variety called Dijon Chardonnay 76. Funding the work is the National Institute of Food and Agriculture, part of the U.S. Department of Agriculture.
“The fungus will always be there,” says Di. “But if the plants can [become] resistant, we don’t have to spray so much.”
But will consumers accept a new and sometimes controversial technology to save an old tradition? If not, what’s the alternative?
A CRISPR grape
Genes are a basic blueprint of life, a code that provides instructions for how a living thing will look and function. Genes are also inheritable. In traditional grape breeding, grapes are cross-bred to take on specific characteristics.
But traditional breeding can be a slog. Breed for one intended trait, and you could lose another vital one. For example, when breeders try to improve a grape’s environmental fitness, they risk changing its flavors.
“Chardonnay is highly valued worldwide. People know and recognize what Chardonnay tastes like,” says Oudemans. “Now, if you start messing with Chardonnay in terms of conventional breeding, you’re going to change the flavor and odor profile to a point that it may no longer be a Chardonnay.”
“Growers and the market are all conditioned to accept certain popular varieties—Merlot, Chardonnay, Cabernet. [My grapes] may have qualities that could be similar to elite varieties, but these would be entirely new varieties.”—Bruce Reisch, geneticist, Cornell University
CRISPR takes a radically different approach. It’s a type of gene editing, often compared to a biological word processor. If genes are a code, then CRISPR allows scientists to add, delete or replace small pieces of that code.
Di aims to use CRISPR to edit Chardonnay genes so the vine resists downy mildew, essentially turning off specific genes to make it harder for the fungus to take hold of the plant.
Changing traditions?
Di’s first lab results are already rolling out, but these are proof-of-concept experiments on a flowering plant called Arabidopsis, which is related to mustard. Scientists use Arabidopsis as a laboratory model, in part because it is easy to grow indoors and has a quick lifecycle. According to Di, the CRISPR’d version of these plants “have shown resistance” to a type of downy mildew unique to this species.
It will take many more experiments to get CRISPR grapes working in the lab and experimental greenhouses. It will take even longer, if ever, before the grapes make it to New Jersey vineyards. In addition to technical realities and whether consumers embrace the practice, the technology may also face regulatory hurdles.
But there’s another option. Chardonnay fans may not like it, but why not ditch the grape and look for new local varieties?
Bruce Reisch, a geneticist and vine grape breeder at Cornell University, is doing just that.
Reisch’s team is examining the DNA of lesser-known wine grapes to find genes that provide natural resistance to downy mildew and other diseases. Then, the scientists crossbreed the resistant grapes with well-known counterparts to create offspring that’s both tasty and easier to grow in the region.
“Growers and the market are all conditioned to accept certain popular varieties—Merlot, Chardonnay, Cabernet,” says Reisch. His grapes are different. “They may have qualities that could be similar to elite varieties, but these would be entirely new varieties.”
Finding a market for these unknown grapes may be a challenge. Wine buyers may pass over something new. But Reisch says it’s worth it. Most of today’s popular grapes are close cousins, susceptible to disease and difficult to grow without pesticides.
More genetic diversity would make for healthier stock, says Reisch, which is beneficial for viticulture in the long run.
Is it a GMO?
Like most scientists who work with CRISPR, Di argues that her work has nothing to do with genetically modified organisms (GMOs), a term mired in controversy.
While the meaning of GMO isn’t always clear, it usually refers to a technique that takes genetic information from one species and inserts it into the DNA of a completely different one.
In some ways, CRISPR can be very different from these older GMO techniques because it allows for more refined genetic changes.
Some of the most common GMOs are modified with genes that produce bacterial toxins, which kill specific insect pests, or genes that make crops tolerant to the herbicide glyphosate, also known as Roundup.
In some ways, CRISPR can be very different from these older GMO techniques because it allows for more refined genetic changes. Instead of inserting a chunk of genetic code from another species, CRISPR can change just a small bit of code within the targeted plant.
But while CRISPR allows for smaller changes, it could still be used to make more drastic ones. This includes inserting genes from other species, says Jennifer Kuzma, a professor of science and technology policy and co-director of the Genetic Engineering and Society Center at North Carolina State University.
“I don’t think you can generalize about gene editing or CRISPR,” she says.
CRISPR proponents tend to focus on the subtler ways it can change a plant, while those opposed to biotech food underscore the more drastic possibilities.
“The truth is somewhere in between,” says Kuzma. “And it depends on the application.”
Di’s work involves relatively small tweaks, a conscious decision to avoid controversy.
“There are social concerns for GMOs,” she says. “The debate is already there.”
Discover more about how science is leading drinks into the future in our Wine & Tech issue.
Last Updated: May 4, 2023
