Merced County Cooperative Extension
Merced County Cooperative Extension
Merced County Cooperative Extension
University of California
Merced County Cooperative Extension

Posts Tagged: Grapes

UC Davis to build new $5.25M greenhouse to protect U.S. grapevine collection

A new greenhouse at UC Davis will be built to protect grapevines from diseases such as red blotch disease, which can cause leaves to turn red, hamper fruit ripening and reduce wine quality. Photo courtesy of Foundation Plant Services/UC Davis

Project designed to prevent red blotch and other grapevine diseases

A new, $5.25 million greenhouse is being built on the University of California, Davis, campus to safeguard an important grapevine collection from red blotch disease and other pathogens. 

The 14,400-square-foot greenhouse will have a vestibuled entry, be insect-proof and provide another level of disease protection. It is being spearheaded by Foundation Plant Services, or FPS, which provides the U.S. grape industry with high-quality, virus-tested grapevine plant material.

The program serves as the primary source for grapevine plant material distributed to nurseries under the California Department of Agriculture's Grapevine Registration and Certification Program, which provides the majority of grapevines planted in the United States. For the grape industry, it is essential to protect this material from disease-carrying insects and guarantee fast access to clean plant material.

“The program is considered the largest quarantine center for the grapevine industry in the United States,” said Maher Al Rwahnih, a plant pathologist and FPS director. “This is kind of a game changer for us.”

A history of serving the grapevine industry

FPS has maintained healthy grapevine planting stock on the UC Davis campus for more than 70 years in open fields at the Classic and Russell Ranch foundation vineyards. FPS scientists first detected grapevine red blotch virus at Russell Ranch in 2017. By 2021, an estimated 51.6% of the crop there was infected. Material from that vineyard is not being sold, and the site is now part of an epidemiological study to try to pinpoint how the disease is transmitted.

FPS pathologists have detected red blotch on less than 1% of the Classic vineyard crop. But it may not always be that way in the future.

“We don't know how long the Classic vineyard will remain clean,” Al Rwahnih said. “Every testing season, this is what keeps me up at night. We're not sure why it's happening in Russell Ranch and not the Classic vineyard.”

Once the greenhouse is operating, grapevines propagated from plant material from the Classic vineyard will be moved into the greenhouse, tested and verified as clean from disease. From there it will be sold to nurseries, which will grow additional plants to sell to growers.

Two greenhouses part of plan

Normally the foundation has 4,000 vines available, but the greenhouse will only house 2,000 vines, so inventory will be cut in half.

“This phase is just a starting phase,” Al Rwahnih said. “It's not sufficient for our needs.”

FPS plans to build another greenhouse in the next two to three years to increase capacity.

Industry groups and FPS identified greenhouses as the best way to protect the plants from red blotch and other pathogens transmitted by insects. They are also consulting with those same people on the grape varieties to include in the greenhouse.

“We have a large selection, and we need to make sure all the varieties that are important to industry are contained,” he said.

The first greenhouse is expected to be finished by the end of 2023.

Funding for the first greenhouse is coming from a variety of sources. The California Fruit Tree, Nut Tree and Grapevine Improvement Advisory Board, managed by the California Department of Food and Agriculture, contributed $4 million to the project. The California Grape Rootstock Research Foundation gave $500,000, Foundation Plant Services with UC Davis is funding $450,000, and the California Grape Rootstock Commission gave $100,000.

“This is crucial for the grapevine industry, and we are very grateful for the support,” Al Rwahnih said.

Posted on Monday, June 6, 2022 at 4:04 PM
  • Author: Emily C. Dooley, UC Davis
Focus Area Tags: Agriculture, Food, Pest Management

Grape experts give workshops on drought preparedness, red blotch

UC Cooperative Extension experts will discuss grapevine red blotch research on March 16. Photo by Evett Kilmartin

Grape growers and other industry members interested in grape production and water management in vineyards are invited to UC Cooperative Extension's Grapevine Drought Preparedness Workshops.

The workshops will be held in person on Friday, March 4, in San Luis Obispo and Friday, April 1, in Hopland.

Registration is $50 and includes a full day of live instruction from UC Cooperative Extension viticulture and grapevine experts. Lunch will be provided.

For more information and to register, visit https://ucanr.edu/sites/ShortCourse17.

UC Davis Grapevine Red Blotch Disease Symposium

On Wednesday, March 16, UC Cooperative Extension and the UC Davis Department of Viticulture and Enology will host a Grapevine Red Blotch Disease Symposium 9 a.m.-3:30 p.m.

Red blotch disease in grapevines, which can dramatically reduce the value of winegrapes, harms plants by inhibiting photosynthesis in the leaves. Infected vines are unable to conduct water effectively, leaving sugar that is created by photosynthesis stuck in the leaves instead of in the berries.

This event will be presented both in person at the UC Davis Conference Center and livestreamed for those unable to attend in person. 

Presentations will cover the role of treehoppers, treatments, mitigation strategies, the impact of the disease on the composition of wine, and more. 

Registration is $250 for the in-person symposium at UC Davis and $150 for the livestream. An application for 3.5 CCE units has been submitted to California Department of Pesticide Regulation and is pending approval.

To see the agenda and to register, visit https://wineserver.ucdavis.edu/events/uc-davis-grapevine-red-blotch-disease-symposium.

Posted on Tuesday, February 22, 2022 at 1:29 PM
Tags: drought (10), Grapes (8), red blotch disease (2)
Focus Area Tags: Agriculture

Researchers pinpoint drought-resistant traits in grape rootstocks

UC Davis researchers hope to help the wine industry by identifying traits linked to drought tolerance in grapevine rootstocks. Photo by Gregory Urquiaga

Findings could help wine industry adapt to climate change

Scientists at UC Davis have identified new root traits that help grapevines resist drought. The findings, published in the journal Annals of Botany, could speed up the development of grape rootstocks that protect vines from dry conditions, helping the grape and wine industry adapt to climate change.

The research, led by Department of Viticulture and Enology Assistant Professor Megan Bartlett, comes as 80% of California is experiencing extreme drought.

Most grapevines are not rooted directly into the ground but are instead grafted onto a rootstock, which forms the underground part of the plant and supports growth above ground.

“Rootstocks are an important tool to manage water stress,” Bartlett said. “Our goal was to identify traits that make rootstocks drought tolerant, so that grape breeders can amplify these traits in new varieties.”

Root cell traits

The study focused on traits measuring drought responses in living root cells.

The research specifically identified capacitance – which measures how much roots shrink as they dehydrate – as an important trait for drought tolerance.

“The water that enters the roots has to cross through a band of living cells to reach the xylem – the network of pipes that carries water up to the leaves,” said Bartlett. Most research has focused on xylem traits, but the living cells are often the first to be damaged during drought.

Water stress can shrink, deform, or even kill the living cells, causing the roots to shrivel away from the soil and lose access to the remaining soil water. Vines are then unable to replace water lost to evaporation and are forced to close the stomata – the small pores on the leaves that take in carbon dioxide for photosynthesis – to prevent severe dehydration. But closing the stomata stops photosynthesis and starves the vine of the sugars it needs to grow and ripen fruit.

This study is the first to test whether traits measuring root shrinkage and cell collapse can capture differences in rootstock drought tolerance.

Cell traits and drought tolerance

The researchers grafted Chardonnay onto eight commercial rootstocks. Half of the vines experienced drought conditions and half were kept well-watered in a greenhouse experiment.

The study found the eight rootstocks were surprisingly diverse and varied widely in their traits. The rootstocks also appeared to acclimate to drought by changing their traits in that the droughted vines were less susceptible to shrinkage and cell collapse than the well-watered vines.

Among the traits, capacitance was especially important for drought tolerance. The rootstocks with a lower capacitance (less root shrinkage) were better able to maintain photosynthesis during drought than other rootstocks.

“This research gives us a new trait to target for breeding more drought tolerant rootstocks,” study co-author and Ph.D. student Gabriela Sinclair said.

The research was supported by the American Vineyard Foundation, UC Davis, and by donations to the department from the Rossi family. Researchers at the University of British Columbia and the USDA-ARS Crops Pathology and Genetics Research Unit also contributed to the study.

Posted on Friday, December 17, 2021 at 1:20 PM
  • Author: Emily C. Dooley
Tags: Climate (5), Climate Change (11), drought (10), Emily C. Dooley (4), enology (2), Grapes (8), Megan Bartlett (1), viticulture (5), wine (13), Wine Grapes (4)
Focus Area Tags: Agriculture, Environment, Food

Increasing temperatures led to better-tasting wine grapes, but for how long?

A worker installs a shade film in Napa, California, to protect cabernet sauvignon grapes from overexposure to the sun. Photo by Kaan Kurtural, UC Davis

Study shows sugar, color content should be watched

Warming temperatures over the past 60 years have led to increased wine quality, but a new study looking at sugar and color content in grapes indicates the industry may be facing trouble if trends continue, according to collaborative research out of the University of California, Davis, and University of Bordeaux.

“Quality has increased steadily up to now,” said lead author Kaan Kurtural, a professor of viticulture and enology and an extension specialist at UC Davis. “We just don't know the tipping point.”

Kurtural's research, published in the journal OENO One, focuses on two renowned wine regions — Napa Valley and Bordeaux, France.

Cabernet sauvignon grapes. Photo by Jack Kelly Clark

Researchers looked at ripening, grape quality and temperature data over six decades in both regions and then confirmed the findings with a five-year trial in Napa. They also consulted wine ratings in publications like Wine Spectator to gauge consumer demand.

One key finding: As temperatures exceeded what was considered the optimal level for quality, the grapes produced better wines.

“Previous research had few field data, but a record of assumptions,” said Kurtural.

Other quality factors at play

Temperature is a factor, but the paper suggests that sugar and color content should not be discounted. The authors also identified a biomarker that affects taste, color and other factors that can be the bellwether for climate change in red-skinned wine grapes.    

“Temperature is always there,” he said. “Temperature is not your bellwether.”

Higher temperatures can harm grape composition, including color, taste and aroma. Researchers examined pigment and sugar content of five California vintages of cabernet sauvignon, finding that as the grapes got sweeter the skin and color deteriorated.

The degradation of these quality-related compounds and the observed plateaus of wine quality ratings suggests there can be too much of a good thing.

Researchers have long theorized that increasing temperatures from climate change would lead to shifts in wine-growing regions, opening up some new areas for vineyards and making others unsustainable.

That shift could be a boon to some economies and devastating to others, something the industry should watch.

“Since the 1980s, grapes got riper and they were able to make better flavor and color compounds,” Kurtural said. “Are we going to lose this or adapt more?”

Gregory A. Gambetta with the University of Bordeaux is a corresponding author on the paper.

For more information:

Posted on Monday, October 4, 2021 at 1:30 PM
  • Author: Emily C. Dooley
Focus Area Tags: Agriculture

Coastal grape growers can use less water during drought

A UC Davis graduate student measures photosynthesis on cabernet sauvignon grapevines. (Photo by Kaan Kurtural/UC Davis)

Study finds using less doesn't compromise quality

California grape growers in coastal areas can use less water during times of drought and cut irrigation levels without affecting crop yields or quality, according to a new study out of the University of California, Davis.

The findings, published today (Sept. 1) in the journal Frontiers in Plant Science, show that vineyards can use 50% of the irrigation water normally used by grape crops without compromising flavor, color and sugar content.

A new study from UC Davis researchers sheds new light on how vineyards can mitigate drought effects at a time when California is experiencing a severe water shortage. (Photo by Greg Urquiaga/UC Davis)

It sheds new light on how vineyards can mitigate drought effects at a time when California is experiencing a severe water shortage and facing more extreme weather brought on by climate change, according to lead author Kaan Kurtural, professor of viticulture and enology and an extension specialist at UC Davis.

“It is a significant finding,” Kurtural said. “We don't necessarily have to increase the amount of water supplied to grape vines.”

Growers will also be able to use this information to plan for the next growing season. “Everybody's worried about what's going to happen next year,” he said.

Kurtural and others from his lab studied irrigation and cabernet sauvignon grape quality at a research vineyard in Napa Valley over two growing seasons, a rainy one in 2019 and a hyper-arid one in 2020.

They focused on crop evapotranspiration, which was the amount of water lost to the atmosphere from the vineyard system based on canopy size. The weekly tests used irrigation to replace 25%, 50% and 100% of what had been lost by the crop to evapotranspiration.

Researchers found that replacing 50% of the water was the most beneficial in maintaining the grape's flavor profile and yield. The level of symbiotic arbuscular mycorrhizal fungi, which help grapevines overcome stresses such as water deficits, was also not compromised. And the water used to dilute nitrogen application was also reduced, making the process more environmentally friendly. 

A drip irrigation system is installed at a new vineyard at the UC Davis Oakville Station. (Photo by Kaan Kurtural/UC Davis)

The water footprint for growing grapes also decreased. For both the 25% and 50% replacement levels, water use efficiency increased between 18.6% and 29.2% in the 2019 growing season and by 29.2% and 42.9% in the following dry year. 

While focused on cabernet sauvignon, most red grapes will respond similarly, he said.  

“In the end, drought is not coming for wine,” Kurtural said. “There doesn't need to be a tremendous amount of water for grapes. If you over irrigate in times like these, you're just going to ruin quality for little gain.”

Members of Kurtural's lab — Nazareth Torres, Runze Yu, Johann Martinez-Lüscher and Evmorefia Kostaki — are also credited as authors. 

University of California Agriculture and Natural Resources provided partial funding.

For more information, contact:

Posted on Wednesday, September 1, 2021 at 9:01 AM
  • Author: Emily C. Dooley
Tags: Drought (0), Kaan Kurtural (0), viticulture (0), Water (0), wine (0), Wine Grapes (0)
Focus Area Tags: Agriculture, Environment, Food

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