Research Results

Click a title below to view a research summary or narrow your search by entering a specific search term or topic.  You can find research summaries keyword, funding year, primary investigator or category using the search boxes at right. Project summaries are available for every year since 1991.

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Wine Compound Interactions That Cause Perceived Smoke Taint in Red Wines.

As detailed in the previous years report more than 120 wines were collected that have various levels of smoke taint. The majority of wines (~100) were Cabernet Sauvignon and Pinot noir, but a few other varietals were also included such as Petit Verdot, Merlot and Syrah. Sensory analysis for these wines were completed in August 2023.

Achieving tropical fruit aroma in white wines: from winemaking to consumer acceptance.

The overall goal of this project is to produce Chardonnay wines with increased tropical fruit aroma perception.  In a previous study developed by Dr. Elizabeth Tomasino’s research group, we found that wines with higher concentrations of fermentation esters and volatile thiols imparted more intense tropical fruit aroma nuances.

Effector-assisted breeding against powdery mildew in grapes.

In last three decades, a great deal of effort and resources have been placed by the grape breeding community on the identification of resistance (R) loci against the grape powdery mildew (GPM) pathogen Erysiphe necator, and their introgression in grapevine varieties of interest.

Highly Selective Enzymatic Degradation of Undesirable Phenols in Brettanomyces and Smoke Taint Contaminated Wines.

This is the first-year progress report on a multi-year project divided into two-phases with the first (current) phase focusing on discovery and design of enzymes with exclusive degradation of 4-ethylguaiacol (4EG) and 4-ethylphenol (4EP), the main sensory-active components in wine contaminated with Brettanomyces and responsible for a portion of the ‘taint’ phenols found in smoke-tainted wine (Licker 1998, Mirabelli-Montan 2021).

Rapid evaluation of smoke exposure in grapes and wine by Raman spectroscopy and machine learning.

We have evaluated 10 different smoke compounds in synthetic wine using a 785 nm Wavelength Raman setup using defined parameters to gain spectra. Individual compounds, as well as different combinations, were tested to provide us with initial results showing the various Raman fingerprints of the smoke compounds and help determine any potential interferences between them.

Impact of malolactic fermentation timing and the use of non-Saccharomyces yeast during cold soaking on Pinot noir wine color and sensory properties. (2024-2704

The malolactic fermentation (MLF) is a key process in the production of red wines and some white wines.  While it is commonly conducted after the completion of the alcoholic fermentation (sequential), it can also be induced at the same time where Oenococcus oeni is inoculated shortly after the beginning of alcoholic fermentation (AF).

Evaluating alternative nursery practices to reduce graft union failure.

Graft failure can be caused by factors such as the poor formation of the graft union (due to problems with anatomical mismatching, poor grafting technique, adverse weather conditions, and poor hygiene), mechanical damage, and graft incompatibility.

From the Lab to the Field: Using Endophytic Bacteria as Biocontrol Agents Against Trunk Diseases in Vineyards.

Bacterial isolates selected from previous AVF grants (2019-2332 and 2021-2573) alongside other beneficial fungal isolates were investigated as potential biocontrol agents against grapevine trunk diseases pathogens. The biocontrol agents were applied as pruning wound protectants (i), as dipping treatments of propagation material prior grafting in nurseries (ii), and as soil drench applications (iii).

Baseline Levels of Smoke-related Volatiles and their Glycosidic Precursors in California Grapes and Wines

The increasing incidence of wildfires in grape growing regions of California and the West Coast has highlighted the need for enhanced understanding of the levels of volatile phenols and their non-volatile glycoside precursors that contribute to smoke taint off-flavors in grapes and wines.

Building community resilience, coordination, and collaboration for individual and regional red blotch disease management.

The goal of this project is to increase the adoption of grapevine red blotch disease (GRBD) management practices at the individual and regional scale. To accomplish the goal, this outreach project supported and empowered viticulture specialists with the educational resources and technical skills to advocate for adoption of practices within their organizations and when attempting collective action with neighboring vineyards.

Variable rate irrigation scheduling based on high-resolution short-wave infrared sensing and internet-of-things.

Vineyards face climate change, increasing temperatures, and drought affecting vine water status. Water deficit affects plant physiology and can ultimately decrease yield and grape quality when it is not well managed. Monitoring vine water status and irrigation can help growers better manage their vineyards.

Extension and Outreach through UC Davis Viticulture and Enology On the Road Events

By the end of the 2022-2023 funding cycle, we completed three of the four On the Road (OTR) educational events originally proposed in the 2022 AVF Extension and Outreach proposal (Tulare, Mendocino, and Lodi) plus the in-person program in Shasta County (twice postponed due to COVID circumstances).


Summary: Warm, dry conditions can exacerbate late-season berry shrivel, reducing yield and altering berry sensory properties. Late-season shrivel occurs when the berries undergo programmed cell death, and the water released from the ruptured cells is drawn from the fruit to the canopy by a water potential gradient.

Sudden Vine Collapse

This project was planned to determine if co-infections of grapevine…

Furthering Elite Grape Rootstocks With Reduced Nematode Susceptibility

The long-time plantings of vineyards are continuously at risk…

Grape Powdery Mildew Reduction

SUMMARY Spray-Induced Silencing of Grape Powdery Mildew Genes…

Tropical Fruit Aroma in Wine

Summary The overall goal of this project is to produce Chardonnay…

Smoke Taint Sensory Interactions

Evaluate and select Pinot noir and Cabernet Sauvignon wines that…

Raman for Smoke Exposure

During the 2022-2023 funding cycle, we have finished the volatile…

Malolactic Fermentation Timing and Color

The malolactic fermentation (MLF) is a key process in the production…

Field Trials of Biocontrol for Grapevine Trunk Disease

Three bacterial isolates selected from previous AVF grants (2019-2332…

Baseline Smoke-Taint Volatiles and Glycosides

Summary The increasing incidence of wildfires in grape growing…

VRI Scheduling System

Summary: Vineyards face climate change, increasing temperatures,…

Reducing Late Season Berry Dehydration

Summary: Warm, dry conditions can exacerbate late-season berry…

Botrytis Bunch Rot: Who, Where, When, and What to Use

In the 2021 field season, eleven field sites from nine different…

Online Guide to Grapevine Varieties and Rootstocks in the United States

A webpage called Grape Varieties in the USA (…