Location: Horticultural Crops Production and Genetic Improvement Research Unit
Project Number: 2072-21000-057-034-G
Project Type: Grant
Start Date: May 1, 2022
End Date: Oct 31, 2025
Objective:
1. Investigate the irrigation initiation timing on grape quality, including volatile and precursor.
2. Investigate the irrigation initiation timing on wine quality, focusing on aroma and flavor quality.
3. Establish optimum irrigation management for grape growers in Southern Oregon.
Approach:
Three vineyards in three sub-regions of the Rogue Valley will be used. These regions represent different soil types and climates. Irrigation treatments will be characterized by varying the initiation timing based on normalized vine water status thresholds. Five treatments will be applied once plot-averaged ASWP are within the described treatment ranges. Vines will be irrigated at 70% ETc and weekly totals of daily ETo will be obtained. Weekly crop coefficients will be calculated from accumulated growing degree-days. Applied water will be measured using an inline water meter connected to a data logger. Crop data will be collected at harvest to characterize yield and quality in response to treatments. Individual vines will be harvested, clusters counted, and fruit weighed. Berry samples will be analyzed for soluble solids. Additional subsets will be sent to the flavor chemistry lab for aroma and precursor analysis. About 100g grapes will be ground under liquid nitrogen. The C6 alcohols and aldehydes, and other major volatiles will be analyzed using SPME-GC-MS methods. The bound aroma precursors will be isolated with a C18 SPE column. Twenty ml of 0.2 M citrate buffer and 100 µl of Macer8TM FJ enzyme solution will be added. The mixture will be incubated to hydrolyze the aroma glycosides. The liberated aroma compounds and total C13-norisoprenoids will be analyzed using SPME–GC-MS. Methoxypyrazine will be analyzed by SPME-GC-MS with stable-isotope internal standards. Separation will be performed on a DB-WAX capillary column. Sixty g of grape berries will be blended with 300 ml of methanol/water/formic acid with the seeds kept intact. The samples will be analyzed by HPLC-DAD. Chromatographic separations will be carried out on a Prodigy C18 column. Wines will be made at SOREC and analyzed for aroma composition using standard protocols. Headspace gas chromatography method will be used to analyze higher alcohols and acetates. A standard curve will be prepared with known concentrations of the analytes in 12% ethanol. Compounds analysis will be done using GC-with a flame ionization detector. SPME-GC-MS method will be used to analyze fermentation and grape-derived volatile compounds. Free-form volatile compounds will be analyzed directly after dilution. The volatiles will be extracted with a pre-conditioned SPME fiber analyzed with GC-MS. A stir bar sorptive extraction coupled with SBSE-GC-MS method will be used to analyze volatile phenolics and lactones. Winemakers and researchers will be utilized for evaluations. MANOVA will be used to analyze aroma compounds. Sensory evaluation data will be collected and analyzed. The sensory data will be correlated with results from instrumental results. Time-series plots of applied water and SWP will be constructed to verify differing amounts of water and treatments were successfully imposed. Canopy and crop data collected will be analyzed by one-way ANOVA. Simultaneous pairwise comparisons between each treatment and control will be made for each response variable tested, and p-values adjusted for multiplicity. Trend analyses will be conducted to identify the nature of responses.
