GiESCO 2019 banner
IVES 9 IVES Conference Series 9 GiESCO 9 GiESCO 2019 9 Impact of crop load management on terpene content in gewürztraminer grapes

Impact of crop load management on terpene content in gewürztraminer grapes

Abstract

Context and purpose of the study ‐ Crop load management by cluster thinning can improve ripening and the concentration of key metabolites for grape and wine quality. However, little work has been done on testing the impact of crop load management on terpene content of white grapes. The goal of the study was to assess if by reducing crop load via cluster thinning growers can increase terpene concentration of grapes, as well as to test if the timing of thinning application affects terpene concentration.

Material and methods ‐ This study was performed in 2016, 2017, and 2018 in Oliver, British Columbia. Field‐grown Gewürztraminer vines were cluster‐thinned at two developmental stages, just after fruit‐set (Early Thinning) and at veraison (Late Thinning), in order to target three crop levels: Light Crop (7 tons/ha), Moderate Crop (10.5 tons/ha), and High Crop (14 tons/ha). Treatments were replicated on five plots arranged in a randomized block design. The effect of treatments on leaf gas exchanges, vine leaf area, and berry sugar (total soluble solid, TSS), acid (titratable acidity, TA), and terpene concentration was analyzed during ripening and at harvest. Free and glycosylated terpenes were identified and quantified using a SPME‐GC‐MS and a LI‐GC‐MS, respectively.

Results ‐ Crop level treatmentsdid not affect leaf gas exchanges and vine leaf area. TSS concentration during ripening and at harvest was higher in Light Crop and Moderate Crop treatments than in High Crop, particularly for Early Thinning treatments. High Crop and Light Crop‐Early Thinning determined the highest free terpene concentration at harvest; however, a significant interaction between treatment and year effects was observed. Total glycosylated terpenes at harvest were marginally affected by treatments (P = 0.063), and Light Crop‐Early Thinning determined the highest total glycosylated terpene concentration. Interestingly, total free terpenes were significantly affected by the treatments at the sampling before harvest (20‐21 Brix), when Light Crop‐Early Thinning determined a higher concentration of total free terpenes than High Crop. This result was consistently among the three years. Our study suggests that crop load management can be used as a tool to improve grape terpenes in scenarios (regions and/or seasons) where ripening is impaired and grapes cannot reach relatively high sugar levels. 

DOI:

Publication date: June 19, 2020

Issue: GIESCO 2019

Type: Article

Authors

Yevgen KOVALENKO, Ricco TINDJAU, Simone Diego CASTELLARIN

Wine Research Centre, The University of British Columbia, 2205 East Mall, Vancouver, BC, V6T0C1,Canada

Contact the author

Keywords

Aroma, Grapevine, Ripening, Thinning, Yield

Tags

GiESCO 2019 | IVES Conference Series

Citation

Related articles…

Use of a new, miniaturized, low-cost spectral sensor to estimate and map the vineyard water status from a mobile 

Optimizing the use of water and improving irrigation strategies has become increasingly important in most winegrowing countries due to the consequences of climate change, which are leading to more frequent droughts, heat waves, or alteration of precipitation patterns. Optimized irrigation scheduling can only be based on a reliable knowledge of the vineyard water status.

In this context, this work aims at the development of a novel methodology, using a contactless, miniaturized, low-cost NIR spectral tool to monitor (on-the-go) the vineyard water status variability. On-the-go spectral measurements were acquired in the vineyard using a NIR micro spectrometer, operating in the 900–1900 nm spectral range, from a ground vehicle moving at 3 km/h. Spectral measurements were collected on the northeast side of the canopy across four different dates (July 8th, 14th, 21st and August 12th) during 2021 season in a commercial vineyard (3 ha). Grapevines of Vitis vinifera L. Graciano planted on a VSP trellis were monitored at solar noon using stem water potential (Ψs) as reference indicators of plant water status. In total, 108 measurements of Ψs were taken (27 vines per date).

Calibration and prediction models were performed using Partial Least Squares (PLS) regression. The best prediction models for grapevine water status yielded a determination coefficient of cross-validation (r2cv) of 0.67 and a root mean square error of cross-validation (RMSEcv) of 0.131 MPa. This predictive model was employed to map the spatial variability of the vineyard water status and provided useful, practical information towards the implementation of appropriate irrigation strategies. The outcomes presented in this work show the great potential of this low-cost methodology to assess the vineyard stem water potential and its spatial variability in a commercial vineyard.

Exploring diversity of grapevine responses to Flavescence dorée infection

Flavescence dorée, a serious threat to grapevine cultivation in several European Countries, is caused by phytoplasmas in the 16Sr-V ribosomal group, classified as quarantine organisms in the EU and transmitted mainly by the insect vector Scaphoideus titanus. The disease is controlled only by indirect and preventive measures, with important economic and environmental concerns. Genetic resources from the great variety of Vitis vinifera germplasm together with application of new genomic techniques could be applied to produce resistant/tolerant plants, once the genetic bases of susceptibility are elucidated. In a current Italian project (BIORES*) we are evaluating different international and local grapevine cvs. as well as microvine plants for their response to FD transmission and multiplication in controlled conditions.

Effect of terroir and winemaking protocol on the chemical and sensory profiles of Pinot Blanc wine

Wine research in the past years has mainly been focused on laboratory scale due to the possibility of controlling winemaking variables. Conversely, studies on wine quality in relation to the winemaking variables at the winery scale may be able to better account for the actual challenges encountered during wine production. Winemaking problems are recently arising from progressive changes in environmental conditions in relation to the terroir. It is important to realize that each wine region may have specific winemaking protocols and that winemakers often base their decisions on subjective, emotional, and empirical opinions. Due to all the above-mentioned issues, taking the correct decision in winemaking to achieve the desired goals may become even more challenging.

TCA – A status report on South African cork closures

Cork taint decreases the commercial value of wine as tainted wines are rejected by consumers. Although other compounds in wine and cork can also be responsible for causing a taint, 2,4,6-trichloroanisole (TCA) is regarded as the primary cause of cork taint. As cork taint is often used in marketing campaigns against natural cork closures,

Measurement of synthetic solutions imitating alcoholic fermentation by dielectric spectroscopy

Having the possibility to use a wide spectrum of elecromagnetic waves, dielectric spectroscopy is a technique commonly used for electrical characterization of dielectrics or that of materials with high energy storage capacity, just to name a few. Based on the electrical excitation of dipoles (polymer chains or molecules) or ions in relation to the characteristics of a weak external electric field, this method allows the measurement of the complex permittivity or impedance of polarizable materials, each component having a characteristic dipole moment.In recent years, the food industry has also benefited from the potential offered by this technique, whether for the evaluation of fruit quality or during the pasteurization of apple juice [1-3]. As the tests are fast and do not destroy the products, dielectric spectroscopy proved to be an experimental tool suitable for online measurements as well as long-term monitoring.