Research Results

The goal of this project was to increase the adoption of grapevine red blotch disease (GRBD) management practices at both an individual and regional scale.  To accomplish the goal, this outreach project supported and empowered viticulture professionals to successfully advocate for the adoption of GRBD management practices within their organizations and outside their organizations when engaged in collective action with neighboring vineyards. 

The principal goal of this project is to optimize control of vine mealybug (VMB) by identifying and then manipulating factors that impact natural enemies of VMB.  Severe VMB infestations can reduce grape vine vigor and fruit marketability.

This project was planned to determine if co-infections of grapevine leafroll associated virus-3 (GLRaV-3) and grapevine virus A (GVA) lead to sudden vine collapse (SVC) on Freedom rootstock and to identify rootstocks that might be more resistant. 

Wine astringency is a major driver of red wine style and consumer experience, yet it remains hard to predict when wines appear similar by routine tests.  Phenolic compounds are chemically diverse, and their effects depend on molecular structure and interactions with the wine matrix and saliva, so wines with similar pH, ethanol, and conventional total phenolic measurements can still feel meaningfully different.

In Years 1 and 2, we tested whether short (2-week) pulses of increased irrigation before or at the expected onset of cell death would reduce water stress-induced oxidative damage and delay or reduce the rate of cell death, reducing shrivel at harvest.  We found that the irrigation pulse at onset significantly reduced the rate of cell death and shrivel at harvest, providing irrigation guidelines to reduce late-season dehydration. 

Vineyards suffer from infestations with plant-parasitic nematodes.  Owed to the extended years of cropping vineyards, the soil-dwelling parasites have ample opportunities to build up and cause damage.  Thus plant-parasitic nematodes can become major yield constraints.  A single location is often infested by multiple species including Meloidogyne spp. (root-knot nematodes), Mescocriconema xenoplax (ring nematode), Xiphinema americanum or X. index (dagger nematode), and Tylenchulus semipenetrans (citrus nematode).

The goal of our project is to use genetic engineering to generate plant material with water-saving stomatal traits, while leaving the rest of the genome intact, to experimentally test the effects of these traits on yield and ripening in economically important grape cultivars

Adoption of sustainable soil management practices is becoming common in winegrape production in response to an increased awareness of the value of soil health to maintain environmental quality.  Soil health is characterized by the functions it provides to the vineyard (i.e water retention, nutrient supply, carbon sequestration etc.) and is often impacted by vineyard soil management practices (i.e., compost application, no till, cover crops).  However, the magnitude of the effect of these practices on soil organic matter and other soil health indicators is difficult to predict.  A major impediment for the diagnosis and establishment of target values of soil health in vineyards is the large diversity of soils and physiographic conditions across and within growing regions.

Our efforts during the 2024 field season focused on Objective #1 using a combination of existing datasets, continuation of data collection in various GRAPEX sites, and installation of new sensors in an experimental vineyard in Davis.  In 2025, we will also utilize large, mature vines growing in harvest collecting bins that are sitting on load cells.  This system will allow us to track water use continuously and compare ET measured with the IRT wavelet sensor.

This is the second year of the project focused on evaluating alternative nursery practices to reduce graft union failure in grapevine propagation.  This study examined how nursery practices influence graft union success and disease management in grapevine propagation. 

This project aimed to develop a non-invasive, real-time method for assessing grape composition in vineyards using hyperspectral imaging technology. This innovative approach helps viticulturists monitor grape quality and make informed decisions about vineyard management and harvesting.

Climate change is expected to increase irrigation demand at the same time as reducing irrigation supply, and developing plant material with lower irrigation needs is crucial to adapt the grape industry to future conditions. Previous work suggests that altering stomatal traits to reduce maximum gas exchange rates or reduce gas exchange more strongly in response to water stress would increase grapevine water-use efficiency without compromising the carbon supply for growth and ripening.

This project was planned to determine if co-infections of grapevine leafroll associated virus-3 (GLRaV-3) and grapevine virus A (GVA) lead to sudden vine collapse (SVC) on Freedom rootstock and to identify rootstocks that might be more resistant. 

Vineyards are continuously at risk for infections by soil-borne pests and pathogens which have ample time and opportunity to establish, build-up in population densities, and cause damage.  Depending on the severity of infection, plant-parasitic nematodes can become major yield constraints.

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.

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.

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.

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.