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This research addresses the fundamental question of what is the genetic basis of the ripening initiation in grape berries. Compelling evidence gathered for the past three years by the Deluc’s group has led to identify one regulatory gene (Auxin-Response Factor 4) that might be involved in determining the entry of a grape berry into the ripening phase (véraison). The objectives of the research project are 1) to validate the role of Auxin-Response Factor 4 (ARF4) on the timing of ripening initiation using genetically engineered microvines, 2) to identify the ripening-related genes that are on the direct and indirect influence of ARF4 with a major focus on genes associated with Abscisic Acid (ABA) and sugar metabolisms, and 3) to determine changes in fruit composition in grape berries with delayed or advances ripening due to the over-expression or the silencing of ARF4. As a first step of the project, we are currently cloning the sequence of ARF4 gene into plasmid vectors to generate transgenic plants that will constitutively accumulate the ARF4 protein or will eliminate the presence of the protein in the transgenic lines.
This research will improve the efficiency of grape production by optimizing fungicide selection and timing to manage powdery mildew of grape berries. Data from one year of field trails indicates that using mobile fungicides chemistry and application late bloom to early set my result in better disease control. This research will determine the most effective fungicide application timing with relation to grape inflorescence development/phenological stage and how their mobility impacts disease development.
Off-flavor development is always a concern in wine industry. One of the increased concerns of wine off-flavor is related to vine stress syndrome. The off-flavor descriptors vary from winery to winery. The typical descriptors include “tequila,” “shellfish,” “peanut,” “ashtray,” “dry weed,” “herbaceous,” “flint” and other descriptors. In young wine, it smells like “bay leave,” and the wines do not age well. There were observations from wineries that vine stress syndrome could be related to compromised or nutritionally imbalanced fruits, induced by drought, nitrogen deficit, or a combination of many factors but the exact cause(s) has never been studied or documented. This research is aimed at identifying the chemical nature of these off-flavors using gas chromatography/olfactometry, GC-MS and sensory analysis. Once the chemical nature of the off-flavor is identified, viticulture and enology remedies could be further investigated.
Wine aroma is one of the most important components of wine quality and can be impacted by grape variety, viticultural practices, and winemaking procedures. One particular practice that is employed during Pinot noir production to impact wine aroma is cold soaking. In this process grapes are held at cold temperatures to prevent growth of Saccharomyces cerevisiae and delay the beginning of alcoholic fermentation. Recent research has demonstrated that yeast naturally present during the cold soak can impact wine aroma. The proposed research builds off these results and investigates how cold soak conditions could be manipulated to encourage or discourage growth of certain yeast and the consequences for wine aroma. Specifically, ways a winemaker may manage a cold soak (temperature, SO2, yeast diversity) will be investigated for their impact on yeast populations and production of volatile aromas. Results from the proposed research will further our understanding of the microbial ecology of a cold soak and how a winemaker may manipulate this in a given year to either minimize spoilage issues (volatile acidity) or encourage formation of desirable volatile aromas.
Oregon has gained great acclaim for its Pinot noir, and is this likely due to a combination of the right cultivar in the right climate, vineyard management, and winemaking practices. However, it is unclear as to which has the greatest impact. Yield has long been identified as a critical factor in premium wine production regions and it is practiced by the majority of Pinot noir producers in Oregon. It is a costly venture at $700-800/acre annually and many wonder if this practice is warranted. Furthermore, there is no understanding how yield levels may impact quality for different production goals. This funding continues a long-term project to determine the impact that yield plays on producing quality wines by conducting crop level research across 15 sites in Oregon. The goal of this research is to examine the effects of site and yield on sustained vine productivity, fruit composition at harvest, and wine quality through sensory evaluation. Researchers will also summarize industry collaborator observations from the vineyard to winery. Results will be statistically analyzed to develop crop load (vine size and fruit weight) metrics that can assist industry in efficiently managing vineyards for diverse production goals.
This research addresses the fundamental issue of whether wine quality can be enhanced more effectively by boosting vine nitrogen status via fertilization or by maintaining lower vine nitrogen status in the vineyard but boosting must nitrogen in the winery. This work will be conducted in both Pinot noir and Chardonnay, as we suspect that red wine quality and white wine quality may differ in response to nitrogen manipulation. The Oregon wine industry will benefit by understanding how to best manage nitrogen inputs to create optimal wines, maintain productivity, and reduce the environmental impact of wine production.
Following the identification in 2012 of Grapevine Red Blotch-associated Virus (GRBaV), substantial efforts have been made to investigate the occurrence and spread of the disease in Oregon vineyards. Leaf collections were made in the fall of 2013-2015, nucleic acid extracts were obtained, and PCR methodologies were applied to detect presence or absence of GRBaV in collected materials. Sticky cards and sweep net samples were collected to capture potential insect vector species. Distribution of insects and virus-infected vines were assessed using a spatial analysis statistical program and visually plotted using a contour-mapping program. Our studies have allowed us to determine: 1) baseline incidence of GRBaV in select Oregon vineyards; 2) confirm GRBaV is spread in these sites; 3) potential insect vectors that may be present in Oregon vineyards. PCR analysis showed that GRBaV is present in most surveyed vineyards and appears to be spreading rapidly in some locations. Several candidate vector species of leafhoppers were present in the sticky cards or sweep net samples. Studies are ongoing to confirm whether any of the collected insect species can transmit GRBaV.