Crop load and plant water status influence the ripening rate and aroma development in berries of grapevine (Vitis vinifera L.) cv. Cabernet Sauvignon

Published: June 30, 2021Wine made from grapes subjected to accelerated ripening, an increasingly frequent phenomenon occurring in many wine regions due to peaks of heat and water stress, displays higher alcohol levels and lacks balance with color and flavor compounds. Herein, the rate of sugar accumulation of grapes was manipulated by varying the crop load and irrigation regime and the development of secondary metabolites was monitored by gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). A 3-week delay in ripening correlated to an increase in the concentration of some monoterpenes and norisoprenoids and a greater decrease of green aroma compounds. Delayed ripening had a positive impact on the phenolic composition of grapes, displaying higher contents of total anthocyanins, total phenolics, quercetin glycosides, and polymeric pigments. A map of the chemical composition of grapes close to harvest allowed discrimination of compounds mainly responsive to delayed ripening from those driven by crop load or irrigation.Pietro Previtali, Nick K. Dokoozlian, Bruce S. Pan, Kerry L. Wilkinson, and Christopher M. For

The effect of ripening rates on the composition of Cabernet Sauvignon and Riesling wines: Further insights into the sugar/flavor nexus

Available online 14 October 2021Grape ripening accelerates under warmer and drier conditions, resulting in the accumulation of sugars (‘technological’ maturity) being decoupled from phenolic and aromatic composition. This study investigated the effect of different rates of ripening on the composition of Cabernet Sauvignon and Riesling wines. Manipulating crop load and irrigation led to distinct rates of berry ripening. In the resulting wines, reduced crop load affected the aroma composition, altering the profile and abundance of grape-derived compounds and fermentative esters. Phenolic composition was impacted by the irrigation regime, with color and tannin increased by late season irrigation. In Cabernet Sauvignon, the combination of treatments led to the largest ripening delay (3 weeks), resulting in less green and more fruity compounds, and improved phenolic composition. By mapping grape and wine metabolites and exploring their relationship, the outcomes of this study demonstrate the importance of ripening rates in determining wine quality.Pietro Previtali, Nick K. Dokoozlian, Bruce S. Pan, Kerry L. Wilkinson, Christopher M. For

Degree of correlation between total light interception and whole-canopy net CO 2

This paper shows the degree of precision by which measurement of total canopy light interception (TCLI) can estimate whole-canopy net CO2 exchange rate (NCER). The test vines comprised a single 35° NE-SW oriented hedgerow, with vertically shoot positioned grapevine canopies at either a low shoot density (10 shoots/metre of row) or a high shoot density (20 shoots/metre of row). TCLI was measured on different dates and at various times on each date (during the 2001 growing season) by a multiple line sensor equipped with 64 phototransistors (35 mm spacing). Each sensor had a spectral sensitivity in the 300-1100 nm waveband and the line of sensors was moved horizontally in steps of 10 cm. Whole-canopy NCER was recorded over successive clear days using an enclosure method. TCLI and canopy NCER were highly correlated on a seasonal basis for both the low shoot density treatment (R2 = 0.97) and the high shoot density treatment (R2 = 0.94). The correlation became less precise (R2 = 0.80 and 0.79 for low and high, respectively), when data taken at various times of day were treated separately. Canopy NCER derived from single TCLI readings taken at solar noon tended to be under-estimated, while NCER derived from single TCLI readings taken later in the afternoon tended to be over-estimated. Nevertheless, for a given training system, our method was sufficiently precise to predict seasonal increase of canopy NCER as well as the total leaf area at which NCER approached a maximum thus setting a value above which additional leaf area resulted in mutual shading without enhancing carbon assimilation

Indices of light microclimate and canopy structure of grapevines determined by 3D digitising and image analysis, and their relationship to grape quality

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