2024 Viticulture Sessions

  • Viticulture – Climate and Environment Research Reports

    June 19, 2024 – 8:15am – 9:35am

    Research Reports

    Location: Marriott Portland Downtown Waterfront

    Moderator:

    Jean Dodson-Peterson, Washington State University, Tri-Cities

    Speakers:

    8:15 am – 8:35 amSimplifying Environmental Sustainability Assessment for Grapegrowers: A Parsimonious Model Approach
    Franca Carlotta Foerster, Hochschule Geisenheim University, Germany
    8:35 am – 8:55 amMapping Global Future Potential for Pinot noir Cultivation under Climate Uncertainty using Generative AI
    Joel Harms, McGill University, Canada
    8:55 am – 9:15 amRole of Grapegrowers in Pollinator Conservation: Protecting and Promoting Bees within Vineyards
    Briann Dorin, York University, Canada
    9:15 am – 9:35 amTrans-Resveratrol Derived from Cabernet Sauvignon Pruning Waste: An Additional Revenue Source for Grapegrowers
    David Garcia, California State University, Fresno

    Franca Carlotta Foerster | Moritz Wagner

    Simplifying Environmental Sustainability Assessment for Grapegrowers: A Parsimonious Model Approach

    Franca Carlotta Foerster* and Moritz Wagner
    Hochschule Geisenheim University, Von-Lade-Straße 1, Geisenheim, 65366, Germany (carlotta.foerster@hs-gm.de)

    Environmental sustainability has become a key factor in production and consumption of many goods and services. Compulsory requirements from organizations, governments, markets, and society push industries like agriculture to assess and lower their environmental impact. The wine industry, especially the viticulture sector, faces several challenges. Vineyards are often managed intensively with herbicides, systemic fungicides, and insecticides with a high application frequency. An adequate strategy to improve sustainability of the wine industry must start with an accurate and objective quantification of its sustainability performance. Life cycle assessment (LCA) is a widely accepted tool for this. Grape production processes can vary considerably between wineries. Consequently, conducting LCA to identify potentials to improve environmental sustainability is highly context-specific, labor-intensive, and requires expertise in LCA. Therefore, it is not yet a hands-on tool for many wineries to assess sustainability of production processes. Simplifying LCA models could increase its use as a management and decision tool in the wine industry. Simplified models must consider specific regional aspects and individual management decisions, but require just a few key parameters to obtain representative results. For the remaining input data, necessary to build models with high predictive power, fixed generic data can be used. This study sought to distinguish input parameters that can be set to a fixed value from those that must be case-specific. Average input data for vineyard management and its probabilistic distribution was collected from the literature and from research and practice experts. The resulting inventory was analyzed in Brightway2 using Monte Carlo simulation and global sensitivity analysis to establish a parametrized inventory. Based on this knowledge, a simplified LCA model was developed by fixing input parameters with low relevance at their median impact values.

    Funding Support: This project is funded by the European Regional Development Fund as part of the Union’s response to the COVID-19 pandemic

    Joel Harms | Jan Adamowski | Viacheslav Adamchuk | Nathaniel Newlands | Simone Castellarin

    Mapping Global Future Potential for Pinot noir Cultivation under Climate Uncertainty using Generative AI

    Joel Harms,* Jan Adamowski, Viacheslav Adamchuk, Nathaniel Newlands, and Simone Castellarin
    *McGill University, 21111 Lakeshore Road, Sainte-Anne-de-Bellevue, Quebec H9X 3V9, Canada (joel.harms@mail.mcgill.ca)

    This study addresses the effect of climate change on the global wine industry, specifically focusing on the suitability of regions for cultivating major international grape varieties. With the increasing challenges posed by climate change, understanding how shifts in climate may affect the quality and production of single-varietal wines is crucial. We propose using a climate-based wine variety recommendation system, using deep-coupled autoencoder networks, to predict regions that will likely undergo improvements or declines for key grape varieties. We tested this approach by predicting possible future Pinot noir regions globally. The system was fine-tuned and evaluated using vintage scorings from representative regions over the past ~30 years, using scorings from multiple respected wine critics. Future predictions are mapped using existing climate models under +2C and +4C scenarios from the TerraClimate Dataset. We use derived climate indicators to identify regions with the greatest potential for Pinot noir. Our findings indicate significant shifts in the suitability of regions, particularly in areas previously considered too cold. This study demonstrates the practical application of wine-recommendation systems in adapting to changing climate conditions and provides valuable insights for the wine industry. By fine-tuning these systems for specific tasks, such as predicting suitable regions for a specific varietal, the wine industry can proactively address the challenges posed by climate change and make informed decisions for sustainable viticulture. This research highlights the wide-ranging possibilities of wine-recommendation systems, showcasing their potential to enhance decision-making processes within the wine industry amid evolving climate conditions.

    Funding Support: This research was supported by funds from the Canada Graduate Scholarships-Master’s (CGS M) Program by the Natural Sciences and Engineering Research Council of Canada held by JH.
     

    Briann Dorin | Sheila Colla

    Role of Grapegrowers in Pollinator Conservation: Protecting and Promoting Bees within Vineyards

    Briann Dorin* and Sheila Colla
    *York University, 4700 Keele St. Toronto, ON, M3J 1P3, Canada 
    (briann.dorin@gmail.com)

    Bees are essential pollinators of many crops and wild plants, thus holding great economic and environmental importance. However, research has shown declines in various bee taxa due to several threats including habitat loss, climate change, pesticide exposure, and interactions with non-native species. Successful pollinator conservation actions must be determined in lands where threats are likely to occur. This research should be done through collaboration with the land managers responsible for their implementation. This is especially needed in crops that are understudied and underused for their potential pollinator conservation capacity, such as those that are pollinator-independent like the winegrape, Vitis vinifera. This research project aims to determine how wild bees can be best supported in Canadian vineyards. Twenty-four commercial vineyards across the Niagara Region, ON, were surveyed to determine the effects of various vineyard management practices and surrounding landscape factors on wild bee abundance and diversity. Bee communities were sampled monthly throughout the spring and summer using pan traps and netting for two years. The vineyard management practices under investigation included cover cropping, mowing frequencies, and organic versus conventional versus certified sustainable management. Surrounding landscape factors included proximity to and percentage of natural lands, impervious surfaces, and different crop types. Bee responses to these variables will be discussed, as well as future directions including engaging grapegrowers in pollinator conservation and important policy implications.

    Funding Support: York University, Entomological Society of Canada

    David Garcia

    Trans-Resveratrol Derived from Cabernet Sauvignon Pruning Waste: An Additional Revenue Source for Grapegrowers

    David Garcia*
    *California State University, Fresno, 5469 North Cedar Ave, Fresno, CA, 93710 (soledadkd@mail.fresnostate.edu)

    This study explores the use of trans-resveratrol from Cabernet Sauvignon grape cane waste in California as an innovative and sustainable income stream for vineyard growers. Employing high-pressure liquid chromatography, we quantified trans-resveratrol concentrations to assess the efficacy of different ethanol extraction concentrations, vineyard location, and soil composition to optimize yield. This process has a twofold advantage: enhancing profitability by converting pruning waste into valuable antioxidants and promoting environmental sustainability by decreasing agricultural waste. The investigation determined that using 50% ABV ethanol significantly surpasses alternative methods for extracting maximum trans-resveratrol yields, demonstrating the economic and environmental benefits of this sustainable practice.

    Comparative analysis of five distinct vineyards in California reinforced the necessity of careful site selection and the adjustment of extraction parameters to boost trans-resveratrol extraction. This approach provides not only a method to increase vineyard revenue, but also to advance sustainable agricultural practices by transforming waste into a resource.

    Converting agricultural waste into antioxidants like trans-resveratrol provides a viable pathway for vineyards to enhance their economic model while contributing to ecological conservation. Ethanol extraction of 50% ABV was the superior technique, providing a practical framework to reduce environmental footprint and advance waste to wealth strategies in agriculture, promising notable gains for the economy and the environment.

    Funding Support: Dr. Qun Sun

    Read more: Viticulture – Climate and Environment Research Reports
  • Viticulture – Irrigation Management Session Research Reports

    June 19, 2024 – 1:30pm – 3:10pm

    Research Reports

    Location: Marriott Portland Downtown Waterfront

    Moderator:

    Alexander Levin, Oregon State University, Central Point

    Speakers:

    1:30 pm – 1:50 pmResponse of Riesling Grapes to Temporally and Spatially Heterogeneous Soil Water Availability
    Geraldine Diverres, Washington State University, Prosser
    1:50 pm – 2:10 pmMetabolomic Response of Vitis vinifera and Interspecific Hybrids to Water Deficit and Heat Stress
    Karine Pedneault, Université du Québec, Canada
    2:10 pm – 2:30 pmEffect of Irrigation Timing and Intensity for Heatwave Mitigation in Cabernet Sauvignon Grapes and Wines
    Pietro Previtali, E. & J. Gallo Winery, California
    2:30 pm – 2:50 pmPrecisely-Timed Irrigation Pulses can Reduce Berry Cell Death and Late-Season Dehydration
    Megan Bartlett, University of California, Davis
    2:50 pm – 3:10 pmExtreme Drought Depresses Vine Growth and Yield Regardless of Fruit Removal
    Charles Obiero, Washington State University, Prosser

    Geraldine Diverres | Danielle Fox | James Harbertson | Manoj Karkee | Markus Keller

    Response of Riesling Grapes to Temporally and Spatially Heterogeneous Soil Water Availability

    Geraldine Diverres, Danielle Fox, James Harbertson, Manoj Karkee, and Markus Keller*
    *Washington State University, 24106 N Bunn Road, Prosser, WA, 99350 (mkeller@wsu.edu)

    Regulated deficit irrigation (RDI) and partial rootzone drying (PRD) have produced diverse viticultural and enological outcomes when implemented in vineyard settings around the world. Most research on deficit irrigation strategies has focused on red wine grape cultivars, optimizing attributes important for red wine production, which differ from white winemaking. A three-year field trial was conducted in southeastern Washington with Riesling winegrapes to compare the effect of RDI and PRD with a no-stress control and test their suitability for premium white wine grape production in arid climates. Irrigation scheduling was based on soil moisture thresholds according to vine phenological stage, rather than adhering to specific time intervals. Irrigation water supply, soil and plant water status, canopy size, yield components, and fruit and wine composition data were collected. Midday leaf water potential (Ψleaf) remained stable near -0.7 MPa until the extractable soil water content declined to ~35% (field capacity is at 100%). Beyond this point, Ψleaf declined as soil moisture decreased further, dropping to values as low as -1.5 MPa. Both RDI and PRD conserved irrigation water compared to the control, but both deficit practices also reduced yield. Seasonal variation had a more pronounced effect on basic fruit composition than irrigation practices. Preveraison water deficit, even if slight, reduced canopy size and yield while significantly affecting the volatile composition of the resulting wines. The wine phenolic composition was affected to a lesser extent by irrigation. This research confirms the power of small differences in preveraison water status to manipulate wine style in the vineyard and explores the relationship between the available soil water content and vine water status, using Riesling as a model.

    Funding Support: USDA-NIFA Cyber-Physical Systems Program, Washington State Grape and, Wine Research Program, Chateau Ste. Michelle Distinguished Professorship.

    Karine Pedneault | Karine Delorme | Frédéric Pitre | Paméla Nicolle

    Metabolomic Response of Vitis vinifera and Interspecific Hybrids to Water Deficit and Heat Stress

    Karine Pedneault,* Karine Delorme, Frédéric Pitre, and Paméla Nicolle
    *Université du Québec en Outaouais, 78 rue Principale, Canada 
    (karine.pedneault@uqo.ca)

    Recent projections of increased temperatures linked to greenhouse gas emissions suggest an increased incidence of heat waves in Canada by 2100. In this context, vineyards will likely face more heat stress along with drier conditions, causing water deficit at critical periods of their development, including when new plots are established.

    Interspecific hybrids varieties are issued from complex breeding programs involving Vitis vinifera and other Vitis species such as Vitis riparia and Vitis labrusca. In the context of global changes, interspecific hybrids bred for challenging environments such as cold climates are often expected to show greater resilience to stress than V. vinifera varieties. However, this assumption has been little studied. To fill this gap, we compared the metabolic response of young V. vinifera cv. Cabernet franc and Riesling and interspecific Vitis spp. Marquette and Vidal to heat stress, mild water stress, their combination, and a control under unstressed conditions over 21 days. Leaves were sampled, extracted, and analyzed by liquid chromatography-mass spectrometry-Orbitrap.

    Over 200 metabolites were detected, including amino acids, phenolic compounds, and sugars. Depending on the variety, between 50 and 70 metabolites increased significantly in plants subjected to heat, water deficit, or combined stress treatments. Heat stress generated the strongest response, but combined stress provided mixed results among varieties. For instance, most metabolites upregulated by heat stress in Cabernet franc increased further when plants were exposed to combined stress. In Marquette and Vidal, most upregulated metabolites showed a lower response during combined stress. These results suggest that the stress mitigation mobilized fewer metabolic resources in Marquette and Vidal than in Cabernet franc, which could relate to a higher resilience in these varieties.

    Funding Support: NSERC; AAFC; CGCN

    Pietro Previtali | Thomas Giagou | Luis Sanchez | Nick Dokoozlian

    Effect of Irrigation Timing and Intensity for Heatwave Mitigation in Cabernet Sauvignon Grapes and Wines

    Pietro Previtali,* Thomas Giagou, Luis Sanchez, and Nick Dokoozlian
    *E. & J. Gallo Winery, 1541 Cummins Drive, Modesto, CA, 95358 (pietro.previtali@ejgallo.com)

    Extreme heat and drought events are becoming increasingly frequent and constitute a threat to grape production. Heatwaves are defined as two or more days with maximum temperature >38°C, and are known to negatively affect vine performance, yield, and wine quality. We conducted a meta-analysis to link historic climate, yield, and grape composition data across five ranches in the Napa region to approximate heatwave effects at the commercial scale. Cultural practices are needed to effectively mitigate heatwaves in the vineyard; in this case, increased irrigation during heatwaves was studied in Cabernet Sauvignon. Irrigation intensity (50% or 100% more than the control) and timing (zero, one, or two days prior to the heatwave) were evaluated. Experimental treatments were compared to the control: deficit-irrigated at 80% crop evapotranspiration through the heatwave. The trial was conducted in California at two sites, Lodi and Sonoma. The 2022 season was characterized by two postveraison heatwaves, one in mid August (four to five days, Tmax = 40.2°C) and one in early September (six to nine days, Tmax = 46.5°C). Across the two sites, additional irrigation effectively improved plant water status and physiological activity. Berry dehydration rates were significantly decreased by the most irrigation (9%) compared to the control (up to 22%), resulting in larger yields at harvest. Additional irrigation mitigated rapid total soluble solids increases observed in the control (up to 6 Brix/week). Incremental increases in irrigation levels during heatwaves resulted in wines with reduced levels of heat damage. The concentration of negative aroma compounds was greater in heat-affected wines, and that of positive fruity esters was less. Phenolic compounds were greatly affected by heat, which translated directly into lower color intensity, higher hue, and lower concentration of mouthfeel-related phenolics.

    Funding Support: E. & J. Gallo Winery

    Megan Bartlett | Alexander Ritter-Jenkins | Argimiro Sergio Serrano Parra | Nikita Kodjak | Dario Cantu | Andrew McElrone | Thorsten Knipfer | Ken Shackel

    Precisely-Timed Irrigation Pulses can Reduce Berry Cell Death and Late-Season Dehydration

    Megan Bartlett,* Alexander Ritter-Jenkins, Argimiro Sergio Serrano Parra, Nikita Kodjak, Dario Cantu, Andrew McElrone, Thorsten Knipfer, and Ken Shackel
    *University of California, Davis, 595 Hilgard Ln, Davis, CA, 95616 (mkbartlett@ucdavis.edu)

    Hot, dry conditions can exacerbate late-season berry dehydration, reducing yield and altering berry sensory properties. Late-season dehydration occurs when the berries undergo cell death in the mesocarp and the water released from the ruptured cells evaporates through the skin or is drawn from the fruit to the canopy by a water potential gradient (backflow). Here, we tested whether short pulses of increased irrigation would be a water-use efficient strategy to reduce late-season dehydration by interrupting stress-induced signals for berry cell death. We compared three irrigation treatments: conventional (following standard commercial practices) and an early- and a late-pulse treatment, where irrigation was increased by 40% in the two weeks immediately before or after the expected onset of cell death. We measured mature Cabernet Sauvignon vines grafted to 101-14 in an experimental vineyard at UC Davis in summer 2022 and 2023. We monitored vine water stress, berry cell death and shrivel, reactive oxygen species (H2O2) concentrations, and markers for cell oxidative damage (malonyldialdehyde, MDA). The late-pulse treatment significantly reduced the rate of cell death and the magnitude of berry shrivel at harvest over the conventional treatment. However, the early-pulse treatment did not significantly affect the rate or date of onset for cell death or shrivel. Concentrations of the reactive oxygen species H2O2 and markers for oxidative damage to cell membranes (MDA) increased at the same time as cell death, consistent with a role in programmed cell death, but were not significantly different among treatments, indicating that other mechanisms regulate irrigation effects on berry cell death. Overall, these findings show that the onset of cell death is not affected by water status, but a short pulse of irrigation soon after onset can slow the rate of cell death and reduce berry shrivel at harvest.

    Funding Support: American Vineyard Foundation

    Charles Obiero | Markus Keller

    Extreme Drought Depresses Vine Growth and Yield Regardless of Fruit Removal

    Charles Obiero* and Markus Keller
    *Washington State University, 24106 N Bunn Rd, Prosser, WA, 99350 (charles.obiero@wsu.edu)

    Frequent drought episodes during fruit development threaten sustainable production of premium winegrapes in the western United States. During an extreme drought event, the irrigation water supply to vineyards may be shut off and growers often remove fruit to ensure vine survival. This study investigated the idea that fruit removal during drought enhances vine survival in Cabernet Sauvignon and Riesling. In 2022 and 2023, irrigation water was shut off either at fruit set or at veraison, and 0, 50, or 100% fruit was removed at the start of each drought period. The outcomes were compared with standard regulated deficit irrigation (RDI), with and without fruit removal. Drought from fruit set or veraison lowered the vines’ water status alike, and the effect was greater in vines with no fruit removed in both cultivars. Canopies of vines exposed to drought stress from fruit set were up to 5.6°C warmer than the RDI vines. Drought starting at fruit set depressed yield more than drought starting at veraison in both cultivars. Vines exposed to drought from fruit set had more than 45% (Riesling) or 60% (Cabernet Sauvignon) less yield than RDI vines. Drought and fruit removal had no clear influence on fruit composition. Compared to the RDI vines, there was more than a one-third reduction in early-season shoot growth and a 40 to 50% drop in the number of flowers in vines exposed to drought stress the previous year, even if fruit had been removed from those vines. Our findings demonstrate that extreme drought will have a long-lasting effect on vine growth and productivity, regardless of fruit removal.

    Funding Support: USDA Northwest Center for Small Fruits Research

    Read more: Viticulture – Irrigation Management Session Research Reports
  • Viticulture – General Viticulture Session

    June 20, 2024 – 10:15am – 11:15am

    Research Reports

    Location: Marriott Portland Downtown Waterfront

    Moderator:

    Renee Threlfall, University of Arkansas, Fayetteville

    Speakers:

    10:15 am – 10:35 amOptimizing Nitrogen Supply for Winegrape Quality in Dry Regions
    Pierre Davadant, Washington State University, Prosser
    10:35 am – 10:55 amChanging Perceptions of Cluster Thinning in Willamette Valley Pinot noir Production
    Kiley Osterman, Oregon State University, Corvallis
    10:55 am – 11:15 amDiabetic Grapes: Motherlode of Sugary Metabolites, Yet Unsuitable for Winemaking
    Bhaskar Bondada, Washington State University, Tri-Cities

    Pierre Davadant | Nataliya Shcherbatyuk | Lee A Kalcsits | James F Harberston | Markus Keller

    Optimizing Nitrogen Supply for Winegrape Quality in Dry Regions

    Pierre Davadant,* Nataliya Shcherbatyuk, Lee A Kalcsits, James F Harberston, 
    and Markus Keller
    *Washington State University, 24106 N Bunn Road, Prosser, WA, 99350 
    (pierre.davadant@wsu.edu)

    Grapegrowers in dry regions face challenges with low nitrogen (N) in harvested grapes, affecting winemaking due to insufficient yeast assimilable nitrogen (YAN). An imbalance in N supply can decrease yield or increase vine vigor, impacting grower profits. Foliar N application at veraison may enhance grape and wine composition without inducing excessive vigor, yet its effect on phenolic compounds remains unclear. We conducted a three-year field trial and two separate pot experiments in arid eastern Washington to test whether foliar-applied N moves to the fruit and other plant organs, enhancing berry ripening and quality, and potentially replenishing the available N pool to support next year’s crop. In a field trial with own-rooted Syrah, we applied liquid urea ammonium nitrate (0, 22.5, 45, or 90 kg N/ha) to the soil at bloom and foliar urea at veraison. We also tested the effect of an extra foliar N spray at veraison (40 g urea/L) on potted Cabernet Sauvignon vines that had received four different rates of soil N at bloom (0 to 3.75g N per pot). Finally, using potted Riesling vines, we applied 15N-labeled urea at veraison on whole canopies, leaves only, or clusters only, to trace N partitioning at harvest.

    Foliar N application at veraison significantly increased YAN in field-grown Syrah and potted Cabernet Sauvignon. Foliar N supply was particularly beneficial for vines with low N status. Higher YAN in harvested berries correlated negatively with skin tannins, but not seed tannins. N applied on Riesling fruit remained in clusters, while N applied on leaves was translocated to the perennial plant organs for storage.

    Funding Support: USDA-NIFA Specialty Crop Research Initiative award number 2020-51181-32159, Washington State Grape and Wine Research Program Ste. Michelle Wine Estates (in-kind)

    Kiley Osterman | Patricia Skinkis

    Changing Perceptions of Cluster Thinning in Willamette Valley Pinot noir Production

    Kiley Osterman and Patricia Skinkis*
    *Oregon State University, 2750 SW Campus Way, Corvallis, OR, 97331 
    (patricia.skinkis@oregonstate.edu)

    Cluster thinning is common in winegrape production and was conducted historically in Oregon Pinot noir to hasten ripening and ensure quality. Industry standard yield targets in the early 2010’s were 4.5 to 6.2 t/ha, and growers questioned those thresholds. To systematically evaluate the effect of cluster thinning on fruit composition and wine sensory perception, a research project was conducted by Oregon State University and >20 vineyard and winery companies from 2012 to 2021. The impact of this research was quantified using a series of surveys, interviews, and focus group meetings to gather information about individual, company, and industry-wide changes to yield management practices. Project collaborators increased yield targets, as there were no consistent differences in berry ripeness at harvest and a lack of differences in wine quality between crop thinning treatments. There were no vine health consequences of maintaining higher yields (dormant pruning weight or vine nutrient status). By the mid-point of the study, the industry began adjusting yield targets based on season variability, rather than a constant tonnage/ha. This was due to the observation that wine quality was more influenced by vintage variation and winemaker than by vineyard crop thinning practices. Most collaborators reported little-to-no difference in wine sensory perception between crop thinning levels. Although most project collaborators felt comfortable increasing yields by 1.24 to 7.71 t/ha without compromising quality, obstacles such as winery capacity and sales limited further adoption for some. Often, target yields were set to fit winery and sales capacity, leading to target yields that did not reflect vineyard yield-quality potential. Project collaborators improved management and vineyard knowledge and expressed a desire to share findings. The project had industry-wide impact with greater yields reported at the state level and greater tolerance of increasing yield targets by growers and winemakers alike.

    Funding Support: Northwest Center for Small Fruits Research

    Bhaskar Bondada

    Diabetic Grapes: Motherlode of Sugary Metabolites, Yet Unsuitable for Winemaking

    Bhaskar Bondada*
    *Washington State University Tri-Cities, 2710 Crimson way, Richland, WA, 99354 (bbondada@wsu.edu)

    Sugars are essential to grapevine growth and development and are therefore monitored under commercial growing conditions to ensure grapes accumulate optimum sugar levels for winemaking. Leaves produce sugars, then they are translocated as sucrose via the phloem, and unloaded in berries to a maximum accumulation of 25 Brix as hexoses at veraison. Any increase or decrease in this level reflects perturbations in the ripening process. In this study, the sugar levels in four cultivars trained to vertical shoot positioning (Syrah, Cabernet franc, Sangiovese, and Petit Verdot) were much greater than 25 Brix. The sugar level in Syrah was >45 Brix, whereas in the other cultivars, it ranged from 27 to 34 Brix. This study’s objective was to determine what caused such high sugar concentrations in these varieties and to provide plausible explanations. Afflicted and healthy clusters were sampled for chemical analysis of primary and secondary metabolites. The high concentration of sugars; other primary metabolites such as acids; and secondary metabolites such as anthocyanins, flavanols, and flavonols; resulted from a physiological disorder known as bunch stem necrosis (BSN). The nutritional status of the berries and the bunch stem was altered, reflected by the levels of macro- (N, P, K, Ca, Mg, S) and micro- (Fe, Mn, Zn, Cu, Mo, B) nutrients. The necrosis typically occurs on the rachis during ripening, causing dehydrated, raisin-type berries. Although BSN caused the raisining of the berries in the 2023 season, the necrosis of pedicels dominated the rachis necrosis. Cell viability tests revealed that most cells were dead. Tylose occluded most of the xylem vessels in the necrotic rachis. Although the occurrence of BSN has been known for several years, its causal factors remain obscure. This study proposes potential causal factors gleaned from the nutritional and compositional analyses.

    Funding Support: N/A
     

    Read more: Viticulture – General Viticulture Session