CHANGINS - Haute école de viticulture et œnologie

BACKGROUND: The increasing temperature associated with climate change impacts grapevine phenology and development with critical effects on grape yield and composition. Plant breeding has the potential to deliver new cultivars with stable yield and quality under warmer climate conditions, but this requires the identification of stable genetic determinants. This study tested the potentialities of the microvine to boost genetics in grapevine. A mapping population of 129 microvines derived from Picovine x Ugni Blanc flb, was genotyped with the Illumina® 18 K SNP (Single Nucleotide Polymorphism) chip. Forty-three vegetative and reproductive traits were phenotyped outdoors over four cropping cycles, and a subset of 22 traits over two cropping cycles in growth rooms with two contrasted temperatures, in order to map stable QTLs (Quantitative Trait Loci). RESULTS: Ten stable QTLs for berry development and quality or leaf area were identified on the parental maps. A new major QTL explaining up to 44 % of total variance of berry weight was identified on chromosome 7 in Ugni Blanc flb, and co-localized with QTLs for seed number (up to 76 % total variance), major berry acids at green lag phase (up to 35 %), and other yield components (up to 25 %). In addition, a minor QTL for leaf area was found on chromosome 4 of the same parent. In contrast, only minor QTLs for berry acidity and leaf area could be found as moderately stable in Picovine. None of the transporters recently identified as mutated in low acidity apples or Cucurbits were included in the several hundreds of candidate genes underlying the above berry QTLs, which could be reduced to a few dozen candidate genes when a priori pertinent biological functions and organ specific expression were considered. CONCLUSIONS: This study combining the use of microvine and a high throughput genotyping technology was innovative for grapevine genetics. It allowed the identification of 10 stable QTLs, including the first berry acidity QTLs reported so far in a Vitis vinifera intra-specific cross. Robustness of a set of QTLs was assessed with respect to temperature variation.

Background and Aims: Grape berries are dried to concentrate sugar and aroma compounds to produce specific wine styles. This work aimed to characterise biochemical changes during drying of two different cultivars, considering in particular tartaric acid and malic acid evolution. Methods and Results: Shiraz and Merlot grapes were dried at nine, 15, 21 and 27 C and berries were sampled every 2 to 3 days and sorted by density using NaCl solutions to account for berry heterogeneity. Mass loss of up to 45%, increase in sugar concentration of 71% and decrease in malic acid concentration of 64% were observed. The TA declined by up to 49%.

The oak barrel maturation step is nowadays strongly rooted in the production of quality wines. Two main physico‑chemical phenomena contribute to the modification and improvement of wine: the solubilisation of volatile and non-volatile wood compounds concomitant with the dissolution of oxygen from the air into the wine. Indeed, wood is a porous material and gas transfer (especially oxygen transfer, expressed as oxygen transfer rate or OTR) through oak barrels, is an intrinsic parameter which ensures wine oxygen supply during maturation. Due to its oenological impact, it has been actively studied over recent decades using several approaches based on the same principle: the monitoring of oxygen in a model wine solution in the barrel. This project aimed at assaying barrel OTR by using a new tool based on the theoretical knowledge of gas transfer through porous materials. An oxygen concentration gradient was created on each side of a barrel kept in an airtight stainless-steel tank. The concentration of the oxygen in the atmosphere around the barrel was monitored in order to quantify oxygen transfer, thus the avoiding common drawbacks of interactions between dissolved oxygen ingress kinetics and the consumption of oxygen in the liquid phase by wood components. This study reports for the first time, the diffusion coefficient of entire oak barrels (Q. sessilis) to be between 10-10 and 10-9 m²/s, and it contributes to increasing knowledge on the complex phenomena driving oxygen ingress during the maturation of wine in barrels kept in cellar conditions. The results highlight the important role of wood moisture content in oxygen transfer, and provides a simple and reliable parameter to monitor it: the weight of the barrel. Following methodology developed by the authors, the OTR of a new oak barrel was found to be 11.4 mg/L per year. Taking into account the oxygen released through the wood pores, a new barrel will contribute 14.4 mg/L per year of oxygen to the wine, of which 46 % in the first three months of aging.

Aim: High sugar concentrations in musts cause a hyperosmotic stress response in Saccharomyces cerevisiae increasing the risk of sluggish and stuck alcoholic fermentations and/or causing high acetic acid levels. Applying a fed-batch technique where sugar levels are kept at a constant, low rate throughout fermentations reduces this stress but requires in-situ quantification of sugars and process automation for practicability. The aim of this work was to develop and validate a near-infrared (NIR) spectroscopy method allowing for the continuous in-situ quantification of total fermentable sugars in fully turbid alcoholic fermentations of grape musts. Calibration models for glucose, fructose and the fermentation product ethanol were also established.Methods and results: A research Fourier-transform NIR spectrophotometer equipped with a transflectance probe was used to acquire spectra from 240 natural and semisynthetic standards from fermentations conducted using varying concentrations of yeast and yeast nutrients. Using chemometric software, calibration models for total sugars, glucose, fructose and ethanol demonstrated R2 values >0.93 and prediction error (RMSEP) values of 11.6 g l-1, 12.3 g l-1, 10.2 g l-1, and 0.328 % v/v, respectively. The method was integrated with modern process automation technology and was able to maintain sugar concentrations within 5 g l-1 of the 45 g l-1 setpoint adjusted during alcoholic fermentations.Conclusions: The NIR calibration models generated allow prediction of total sugar levels accurately enough to conduct fully automated fed-batch grape must fermentations at constant substrate concentrations. Application of a transflectance probe measuring a high proportion of back-scattered radiation proved useful and necessary considering the high degree of turbidity during fermentations. Placement of the measurement probe in a recirculation loop decreased interference from biomass sedimentation and adherence of CO2 bubbles.Significance and impact of the study: This study presents a fully automated system to carry out fed-batch fermentations which allow circumventing the hyperosmotic stress response of S. cerevisiae during alcoholic fermentations. Calibrated for other substrates, the system may be used in other food and non-food fermentations, too.

Grapevine winter hardiness is governed by several factors besides extreme weather conditions, such as site-specific soil factors (texture, composition, moisture, drainage), vine water status, and yield. It was hypothesized that winter hardiness would be influenced by specific vineyard terroir-driven factors and that zones in vineyards with low water status (leaf water potential [Ψ]) would likewise be more winter hardy than vines with high water status (less negative leaf Ψ). Six Riesling vineyards were chosen throughout the Niagara region in Ontario. Data were collected at fruit set, lag phase, and veraison (soil water content [SWC], leaf Ψ), at harvest (yield components, berry composition), and three times during the winter (LT₅₀; the temperature at which 50% of buds die) in 2010 to 2012. Interpolation and mapping of variables was completed using kriging, and statistical analyses (linear correlation, <i>k</i>-means clustering, principal components analysis, multilinear regression) were performed. SWC, leaf Ψ, yield components, berry composition, and LT₅₀ were spatially clustered in each vineyard. GIS and multilinear regression revealed that leaf Ψ could predict the LT₅₀ value, with strong correlations observed between LT₅₀ and leaf Ψ values in most of the vineyard blocks in 2010 to 2011 (4/6 and 5/6, respectively). In the extremely dry 2012 season, leaf Ψ (range across sites at veraison 0.9 to 1.4 MPa) was positively correlated to LT₅₀, yield, titratable acidity, pH, and Brix and inversely correlated to SWC and monoterpene concentration. Results suggest that there is a spatial component to winter hardiness, as with other aspects of terroir. This study allows a method to compare winter hardiness to other critical variables to better understand terroir-based factors of the Niagara region.

Grapevine yield sustainability under global warming is a major issue. A hypothesis is that long-term elevated temperatures may cause the failure of key phases of reproductive development, through their negative impact on carbon balance. However, testing the specific role of plant carbon status on yield elaboration under elevated temperatures is difficult on perennial crops, such as grapevine, and when environment fluctuates. To overcome these difficulties, the present work was conducted under fully controlled environment using Microvine, a new model for grapevine genetics and physiological studies. Five experiments were performed ingrowth chambers, applying contrasted day/night temperature over a one- to two-month period. Plant phenology, vegetative development and yield components were assessed before and after temperature treatments. In addition, the biomass growth and sugar contents of all individual above-ground organs and of roots were determined at harvest. High temperatures caused inflorescence abscission, but did not change flower and berry numbers on the remaining bunches. Flowering and véraison were also delayed by warm temperatures, on a thermal time basis. In contrast, plant phyllochron and biomass accumulation were unchanged. Carbon status in roots was altered under high temperatures, thus indicating carbon gain was impaired with sink demand. These results suggest that dynamics of carbohydrate pool within perennial organs act as an adjusting variable to buffer changes in carbon balance. This study provides the first basis for a modelling approach of yield responses to carbon balance under climate changes

The aim of this ongoing study is to establish a vine physiology, berry quality - based methodology to analyze small scale differences between plots in a sub-region of the AOC Lavaux, in Switzerland. The production area Villette is almost to 100% planted with the cultivar Chasselas L. covering a total of 140 ha of steep slope terraced vineyards and offers an excellent site for terroir studies. A representative network of 23 plots covering the entire Villette production area was established in 2016 and 2017. Important differences in budburst and flowering were observed between plots whereas altitude was the main driver of precociousness. Expectedly most precious plots had highest sugar and lowest malic acid concentrations at final sampling date. Individual berry weight variation was up to 35 % at the last sampling (2.4 to 3.3 g) with variation in sugar concentration of 13 % (70-84° Oechsle). Sugar quantity per berry variation was however twice as high (26%), illustrating important differences in the sugar accumulation pattern between plots. Interestingly the latest plots accumulated highest sugar per berry with lowest concentration. The preliminary results of this ongoing study provide valuable information of the ripening potential of Chasselas in a small mesoclimate and illustrates the possibilities to characterize viticultural terroirs based on vine physiology measurements.

La vigne est une plante pérenne à cycle reproducteur annuel. Ce fait signifie qu’en climat tempéré, chaque stade de développement de la baie ne peut être observé qu’une fois par an. Comme d’autres plantes pérennes, un autre inconvénient de la vigne est qu’après germination, greffage ou bouturage, elle passe par une phase juvénile d’environ trois ans où elle ne produit pas de raisins. Par ailleurs, la vigne adulte occupe un espace important qui la rend difficilement cultivable en grand nombre en serre ou en chambre de culture en conditions contrôlées. Ces caractéristiques desservent les études scientifiques où les paramètres environnementaux doivent être maîtrisés afin de limiter les biais induits par des conditions mal contrôlées. Dans l’enseignement, les travaux pratiques sur le cycle reproducteur sont soumis aux contraintes du calendrier scolaire, ce qui complique leur mise en place et leur suivi en fonction des saisons.

International audience

Due to global warming, agricultural production systems are exposed to increasing abiotic stresses, which threaten an economically and environmentally sustainable food production. Innovative environmentally friendly solutions are needed to cope with climate-related risks and to reduce the use of high amounts of synthetic agrochemicals. A promising solution to foster sustainable agriculture involves the use of biostimulants. This strategy, however, is not adopted by the industry to a great degree due to the scarce number of reproducible effects observed in published studies as well as the lack of fundamental knowledge about their mode of action. Biostimulants are substances that positively impact plant physiology by enhancing growth, improving fruit quality, and increasing stress resilience. Among these, protein hydrolysates stand out as a particularly promising category. However, their precise mechanisms of action and the optimal conditions for their application are still not fully understood. This project aims to develop peptide-based biostimulants in a reproducible manner, ensuring their availability for use in plant model systems under strictly controlled conditions. To achieve this, various protein hydrolysates will be produced through the enzymatic hydrolysis of whey, a by-product of cheese production. These hydrolysates will be employed in subsequent studies within plant model systems.

No abstract.

UMR AGAP - équipe DAAV (Diversité, adaptation et amélioration de la vigne)<br/>UMR AGAP - équipe DAAV (Diversité, adaptation et amélioration de la vigne)

International audience

Sulphur dioxide (SO 2 ) antiseptic and antioxidant role allows it to preserve the wine from oxygen's negative effects. However, its use is increasingly challenged by the concerns of consumers and producers who want to limit the chemical inputs in wines. During winemaking, many stages can lead to a transfer of oxygen to the wine. Bottling is crucial. In order to limit oxygen addition to the wine, various inerting devices have been developed by manufacturers. The first part of this work aims to understand the influence of bottle inerting sequence, rate work and pressure of inert gas, on the amount of oxygen in the bottle before filling. The results indicate that the level of oxygen brought to the wine depends on the settings implying to adapt them specifically to each bottling setup. Once inerted, the bottles are filled and corked. The influence of the filling nozzle and of the inerting devices on the oxygen addition was studied. The amount of oxygen brought to the wine during bottling was significantly reduced by the use of inerting devices. The influence of the filling nozzle and the setting conditions used was also highlighted. Thus, good management of oxygen addition requires the mastery of the bottling chain.

Le terme minéralité a fait son apparition dans le discours des professionnels et des consommateurs de vins, sans qu'en existe une définition précise et consensuelle. Cette étude de trois sous-corpus parallèles (trois questions), constitués des réponses de 1 697 consommateurs, met en évidence ce que la minéralité évoque (ou non), comment les consommateurs la définissent et quels termes peuvent être considérés comme synonymes. On y compare les résultats obtenus par deux méthodes, l'Analyse des Correspondances d'une part, soulignant les saillances textuelles dans chacun des sous-corpus, et le partitionnement des réseaux textuels générés par les Associativités Markoviennes renormalisées d'autre part, basées sur les associations entre termes. Les deux analyses, complémentaires, distinguent et identifient les différentes représentations que les consommateurs peuvent avoir du concept de minéralité dans les vins.

Le projet «Minéralité des vins : étude et valorisation d’un concept en vogue mais méconnu» a été sélectionné dans le cadre du programme de coopération territoriale européenne Interreg IV A France-Suisse 2007–2013.

L'évaluation de l'état hydrique de la vigne est cruciale pour optimiser les pratiques culturales et les stratégies d'irrigation afin de garantir une viticulture durable sur le plan environnemental et économique, compte tenu des pénuries d'eau croissantes causées par le réchauffement climatique. L'état hydrique de la vigne peut être évalué par des méthodes indirectes, basées sur le sol ou l'atmosphère, ou par des méthodes directes basées sur les plantes, chacune ayant des avantages et des inconvénients différents selon l'application. Ce bref examen vise à donner une perspective sur les résultats les plus importants et récents de la littérature traitant des méthodes directes basées sur les plantes. Les récents progrès scientifiques en matière de régulation hydraulique et stomatale de la vigne mettent en évidence les limites des techniques traditionnelles telles que la mesure du potentiel hydrique des feuilles, notamment dans le contexte de la sécheresse et du déficit de pression de vapeur (VPD) élevé.