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A study on Sauvignon blanc (SB) cultivar in France showed that curettage had an effect on the resilience of GTD grapevines. No experiments, however, have been conducted on its effects on wine quality, particularly on white Sauvignon blanc cultivar wines. Methods and results: Grapevines from Sauvignon blanc cultivar that had expressed Esca-foliar symptoms were used for the study, with some of them having been curetted in 2014. Subsequently, bunches from Control (asymptomatic), Curetted and Esca-symptomatic vines were harvested in 2017 and 2018 in order to produce white wine. Technical and chemical results on both must and wine showed that wines from curetted plants were similar to those from asymptomatic vines. There were differences, however, for Esca-diseased vines, where the alcoholic fermentation of musts was faster than for the other modalities. Olfactometry results showed that, for the one-year-old 2017 vintage wines, no differences were detected, although they were for the 2018 vintage. Conclusion: The results of the chemical analyses and wine tasting showed that the wines from curetted and asymptomatic grapevines were similar, and that their quality was the same. Significance of the study: The quality of wines from curetted vines compared to asymptomatic ones was confirmed and validated through chemical and sensory analyses of the must and the one-year-old wines. k e y w o r d s curettage, Esca, Sauvignon blanc, musts, chemical analyses, wine quality

International audience; Methyl salicylate (MeSA) is a plant metabolite that induces plant defence resistance and an odorous volatile compound presenting green nuances. This volatile compound was shown to be present in wine samples, sometimes at concentrations above its olfactory detection threshold. MeSA is localized in grapes, particularly in the skins and stems, and is extracted during red wine vinification. It was detected at the highest concentrations in wines of several grape varieties, made from grapes affected by cryptogamic diseases, namely downy mildew caused by Plasmopara viticola, and black rot caused by Guignardia bidwellii. It has also been detected in wines from vines affected by Esca, a Grapevine Trunk Disease. MeSA can also be considered to be a chemical marker in grapes and wine indicative of the level of development of several vine cryptogamic diseases.

Grape berries host a complex microbial community that plays a predominant role in grape quality prior to harvest and in the winemaking process. Like other carpospheric habitats, the epiphytic microbial community of grape berries is influenced by several factors. Climate plays an essential role in grape composition and quality, and its impact on berry microbiota was recently demonstrated. However, there is still a lack of information about how environmental conditions influence the system in grape berries.In this study, the microbial communities of grape berries from two wine appellations characterized by specific climatological conditions were analyzed. The results revealed that the size of cultivable communities (bacteria, yeast and filamentous fungi) and the diversity and richness of the microbial community profiles were higher in vineyards found to have lower temperatures. The metabolic activity (Community-Level Physiological Profiles) of the epiphytic microbial community was lower in warm climates. Water activity (aw) had a positive effect on the cultivable population, on metabolic activity, and on microbial diversity.The results showed that the microclimate affects the microbial population associated with grape berries through the aw of grape skins.

Phenolic compounds are important constituents of red wine involved in its sensory properties. Although wine tannins can come from microbial and oak sources, the main sources of polyphenol remains grape skins and seeds. In order to better understand the grape seed and skin tannins contribution to the final wine tannins content, an original approach of winemaking has been set up. Our protocol explains a simple method to determine the percentage of skin and seed tannins extracted in wine all along the winemaking. The advantages of this method are presented below:•This method allows us to describe tannins extraction kinetics in wine according to the berry part (skins and seeds).•Additionally, our protocol allows to specifically determine the percentage of tannins extraction according to the winemaking stages (alcoholic fermentation and post-fermentative maceration) and the berry part (skins and seeds).•To sum up, this method serves to enhance the comprehension of tannins extraction process in wine according to the berry part., Graphical abstract Image, graphical abstract

International audience; The formation of 3-methyl-2,4-nonanedione (MND) during red wine aging can contribute to the premature evolution of aroma, characterized by the loss of fresh fruit and development of dried fruit flavors. The identification of two new hydroxy ketones, 2-hydroxy-3-methylnonan-4-one (syn- and anti-ketol diastereoisomers) and 3-hydroxy-3-methyl-2,4-nonanedione (HMND), prompted the investigation of the precursors and pathways through which MND is produced and evolves. An HS-SPME-GC-MS method was optimized for their quantitation in numerous must and wine samples, providing insight into the evolution of MND, HMND, and ketols through alcoholic fermentation and wine aging. Alcoholic fermentation resulted in a significant decrease in MND and HMND and the simultaneous appearance of ketol diastereoisomers. The analysis of 167 dry red wines revealed significant increases in MND and anti-ketol contents through aging and a significant positive correlation between MND and anti-ketols. Additional experiments demonstrated that ketols are precursors to MND during red wine oxidation.

International audience; Context and purpose of the study: Like in other wine producing regions around the world, Bordeaux vineyards already experience the effects of climate change. Recent trends as well as model outputs for the future strongly support an increase of average and extreme temperatures. For the maturation period, this increase will by far exceed mean atmospheric temperature increase, as the ripening period will occur earlier in hotter climatic conditions. Therefore, a detrimental secondary metabolism response is expected in grape berries, and of particular concern are the impacts on phenolics and aromas and aroma precursors. The effects of high temperatures on secondary metabolism control have been partly characterized for phenolics, however mostly in artificial growing conditions, while little is known with respect to aromas. A better understanding of how high temperatures influence grape berry secondary metabolites could help vineyard growers to adapt to climate change and maintain wine quality. Material and methods: A two-year field study was carried out in 2015 and 2016 in a vineyard in Bordeaux, France. Two treatments, heated (H) and control (C), were applied to two varieties, Cabernet-Sauvignon and Sauvignon blanc, from fruit-set to maturity. Field heating was achieved by a very local greenhouse effect applied to the bottom of the rows, by enclosing most of the underlying soil surface by polycarbonate shields. As the training system was vertically trellised, the heated volume surrounded most of the bunches but did not disturb most of the leaves in the canopy. This simple and robust setup allowed an increase of berry temperature by about +1.5 degrees C in mean value, up to +5 degrees C at times during clear sky days. This moderate increase of temperature was indicative of the predicted future climatic conditions for the mid-21st century. Berry samples were collected at 4 time points from bunch closure to maturity for each cultivar and treatment. Primary and secondary metabolites were measured in whole berries or skins. Results and conclusions: With this moderate temperature increase, primary metabolite content in berries did not change significantly. In H samples, anthocyanins were reduced and tannins increased before veraison, and both decreased thereafter. H samples also exhibited lower concentrations of some amino acids, especially alanine, serine and phenylalanine. IBMP (2-methoxy-3-isobutylpyrazine) concentrations were also reduced in H samples of Cabernet-Sauvignon, in both seasons, especially at bunch closure stage, but the differences diminished at full maturity. For thiol 3-sulfanyl hexanol precursors, H samples again exhibited much lower concentrations for both varieties, with weak differences at early stages that increased at later stages (up to -70% decline at maturity in 2015 for Sauvignon blanc). These results demonstrate the potential negative impact of elevated temperature on polyphenols and aroma quality of grape berries. Significance and impact of the study: For viticulture to adapt to new climatic conditions, the negative impacts of high temperature on secondary metabolites and aromas, and therefore on wine quality, need to be contemplated. Thus, already established or new vineyard plantings must prepare and consider practices able to mitigate these impacts, for instance practices that increase bunch shading.

International audience; Phenolic compounds are among the most important quality factors of wines. They contribute to the organoleptic characteristics of wine such as color, astringency, and bitterness. Although tannins found in wine can come from microbial and oak sources, the main sources of polyphenols are grape skins and seeds. Since the 1960s, this subject has been widely studied by a large number of researchers covering different types of wine, climate conditions, growing practices, and grape varieties. As these works have been conducted under different conditions, the data collected can be conflicting. Moreover, even though the biosynthesis of the major proanthocyanidins units (+)-catechin and (-)-epicatechin is well-known, the mechanism of their polymerization remains unexplained. This is why the question remains: what factors influence the biosynthesis, the quantity, and the distribution of tannins in grape seeds and how can winemaking processes impact the extractability of seed tannins in wine?

International audience; The extraction of seed and skin tannins in wine has been investigated at three different grape maturity stages. For that, the tannins content and composition of seeds and skins at three different maturity stages were characterized. After that, an original approach of nanovinification was conducted. At each maturity stages, three winemaking modalities have been produced: (i) a control modality, (ii) a seed modality made of exclusively with seed and (iii) a skin modality made of exclusively with skins. The aim of this work is to describe and explain the seed tannins kinetics release in wine but also the impact of grape maturity on seed tannins extractability. For that, the evolution of seed and wine tannins content have been followed during the winemaking, from alcoholic fermentation to post-fermentative maceration.

International audience; Pulsed electric field (PEF) treatment is an emerging technology that is arousing increasing interest in vinification processes for its ability to enhance polyphenol extraction performance. The aim of this study was to investigate the effects of PEF treatment on grape skin histocytological structures and on the organization of skin cell wall polysaccharides and tannins, which, until now, have been little investigated. This study relates to the effects of two PEF treatments on harvested Cabernet Sauvignon berries: PEF1 (medium strength (4 kV/cm); short duration (1 ms)) and PEF2 (low intensity (0.7 kV/cm); longer duration (200 ms)). Histocytological observations and the study of levels of polysaccharidic fractions and total amounts of tannins allowed differentiation between the two treatments. Whereas PEF1 had little effect on the polyphenol structure and pectic fraction, PEF2 profoundly modified the organization of skin cell walls. Depending on the PEF parameters, cell wall structure was differently affected, providing variable performance in terms of polyphenol extraction and wine quality.

The treatment of Cabernet Sauvignon red grapes by pulsed electric fields (PEFs) is performed prior to vinification in order to enhance the extraction of polyphenols. PEF treatments of the longest duration and of the highest energy (E = 0.7 kV/cm, t PEF = 200 ms, W = 31 Wh/kg) changed the structure of grape skins and produced a wine that was richer in tannins (34 %), while treatment of the highest strength (E = 4 kV/cm, t PEF = 1 ms, W = 4 Wh/kg) altered the visual appearance of phenolic compounds in the skins and led to greater extraction of the anthocyanins (19 %). The PEF treatments caused the depolymerization of skin tannins, improving the diffusion of these decondensed tannins which are smaller. The PEF treatment of longest duration and of the highest energy had more impact on the parietal tannins and the cell walls of the skins while treatment of the highest strength modified more the vacuolar tannins. Changes in the operating parameters of the PEF treatment (E = 0.7 to 4 kV/cm, t PEF = 1 to 200 ms, W = 4 to 31 Wh/kg) did not affect alcohol content, total acidity nor volatile acidity in finished wines compared to the values of the control wine, but seemed to cause a slight increase in pH (1–2 %).

Background and Aims: The impact of grey mould (Botrytis cinerea (B. cinerea)) was quantified on chemical, phenolic and sensory qualities of grapes, derived musts and wines. Methods and Results: Analyses were carried out by using naturally or artificially infected grape berries at ripeness or overripeness. In grape seeds, chemical analyses revealed no major differences between healthy and rotten grapes. In grape skins of Botrytis-affected berries, concentrations of all the phenolic compounds (anthocyanins and proanthocyanidin monomers, dimers and trimer) decreased drastically. Mean degree of polymerization of the proanthocyanidin polymeric fraction was also affected in skins. Chemical analyses of musts and wines made with different percentages of rotten berries showed a moderate impact of the pathogen on their phenolic composition. Nevertheless, sensory analyses underlined a loss of wine sensory quality perceptible from a threshold as low as 5% of Botrytis-affected grapes onwards. Conclusion: Phenolic variations and the associated negative impact in grapes, derived musts and wines may be related to oxidation phenomena from B. cinerea. The main effects of severity/age of grey mould and the level of berry maturity are also discussed. Significance of the Study: B. cinerea drastically affects the phenolic and organoleptic properties of grape skins and derived wines. Therefore, prophylactic actions early in the vineyard, evaluation of the sanitary status of the harvested grapes and berry sorting are primordial even under low disease pressure.

Background and Aims: The impact of Esca, a cryptogamic disease affecting woody tissues of grapevines (trunk, branches and shoots), was investigated on phenolic and sensory qualities of Cabernet Sauvignon grapes, derived musts and wines. Methods and Results: Global phenolic analyses revealed no major difference between healthy and affected grapes whereas high-performance liquid chromatography analyses showed decreases in the skin concentrations of catechin and epicatechin and of anthocyanins for the two vintages assessed. Proanthocyanidin characteristics, and particularly mean degree of polymerisation, were strongly decreased in skin proanthocyanidin polymeric fractions. Chemical analyses of wines made with different percentages of fruit from Esca infected grapevines confirmed the moderate impact of Esca on phenolic composition. Nevertheless, sensory analyses revealed a loss of wine sensory quality perceptible with as little as 5% of affected fruit in wines. Conclusions: Phenolic variations in grapes and in derived wines may be related to changes to grapevine physiology caused by Esca fungi that impact on flavonoid metabolism. The chemical and sensory variations between wines can also be related to the delayed ripening delay of fruit from Esca infected grapevines. Significance of the Study: Esca moderately affected the phenolic composition of grapes and decreased the sensory quality of wines, suggesting a dramatic increase in the economic importance of Esca if no control methods are found.

The study was carried out in order to compare the development of berries growing on fruiting cuttings and on vines from the field, and to evaIuate this experimentaI system for grapevine physiology studies. The results show that the main developmental characteristics of the berries are close to those of berries from the vineyard. Fruit set is good and berry growth follows a double sigmoid curve. Final size is smaller than usual, even if seed number is higher for fruiting cuttings. The evolution of organics acids, sugar and mineral content is classical. At maturity, the berries from fruiting cuttings reach the same sugar content, but are less acidic, because the components of acid equilibrium are slightly modified. At flowering polyamine content is higher in the cluster of fruiting cutting but the variations aIong cluster development is the same than in the vineyard. Finally the application of exogenous putrescin on fruiting cuttings at flowering time improves fruit set, as in the field. Our data allow to conclude that fruiting cuttings behave mostly as bigger vines and could be a usefull tool for grapevine physiology studies.

Aims: The objective was to better understand the mechanisms involved in grape ripening that brings about important changes in the physiology and chemistry of the fruit. So we focused on the involvement of two growth regulators: abscisic acid (ABA) and indol-acetic acid (IAA) in controlling grape berry ripening process.Methods and results: We described the evolution of the two plant growth regulators during the development of cv. Merlot grapes (Vitis vinifera L.). In order to better understand the role of ABA and IAA in the ripening control, these two growth regulators were applied on the grapes at the onset of veraison. The hormonal profile was established on treated berries and different physiological parameters were assayed to evaluate the effects of both applications. The partitioning of both plant growth regulators in nontreated berries showed that ABA and IAA accumulated at the onset of ripening. Moreover, it appeared that endogenous ABA decreased progressively in the flesh while accumulated in the skin from the beginning of the colour change to maturity. The hormonal treatments modified the hormonal profile and several physiological parameters: sugar, acidity, colour, and Botrytis sensibility.Conclusion: These findings suggest that both treatments have modified the ripening process. Exogenous ABA has induced advancement in grape ripening, while IAA application has delayed this process. These observations support the view that the grape ripening process may be influenced by the hormonal status.Significance and impact of study: This study gives new information about the ripening control of the non-climacteric fruits. In grape berries, it provides evidence of a possible co-involvement of ABA and IAA in controlling ripening process.

Grape berry ripening is characterised by numerous metabolic and physiological changes, placed under hormonal control. The phytohormone abscisic acid (ABA) is considered as a possible promoter of « véraison », since it accumulates at this time. In order to evaluate its impact, we assess the effect of ABA on several parameters of maturity: anthocyanins synthesis, phenylalanine ammonia-lyase activity, sugar contents, acidity and maturity index, both in untreated berry skin and in skin of berries submitted to applications of exogenous ABA. The maturation processes we focused on appear ABA-dependent, as they occured immediately after ABA accumulation in the skin. Treatment also shows a close relationship between ABA and the beginning of ripening. These results allow us to conclude that ABA content could modulate the triggering of « véraison ».

The effects of polyamines were examined for growth and polyamine contents in cultings, callus and primary adventitious roots of Vitis vinifera L. Variations in free, conjugated and wall-bound polyamines in cuttings were observed during rhizogenesis. The main polyamines in cuttings were conjugated polyamines while in callus and primary adventitious roots they were free polyamines. Exogenous polyamine addition did not modify the total number of roots per cutting but increased the mean size and number of long roots. Moreover, exogenous polyamines increased polyamine levels in callus and roots, particurlarly wall-bound and conjugated polyamines. The involvement of these classes of polyamines in morphogenic processes is discussed.

A method for producing fruiting cuttings of grapevine cv. Cabernet Sauvignon is described. The main developmental features of these cuttings are presented. The clusters reach maturity after 5 months and the period of cluster development is not shortened. Before flowering, a careful control of stem and leaf growth improves the partitioning of stored carbon towards the roots and the cluster. Vegetative growth occurs mainly between fruit set and veraison. During ripening, the leaf to fruit ratio is between 20 and 30 cm2 of leaf area per gram of fruit. In the cuttings as well as in grapevines from the vineyard, free polyamine content in the leafblade does not change during development. Conjugate polyamine content does not evolve in the same way. It peaks at veraison for vineyard leaves but decreases continuously for cuttings. A proper nutrient solution provides a minerai composition in accordance with viticultural requirements. The cuttings also behave like vineyard plants in response to different levels of potassium in the nutrient solution.

Nitrogen is the most important element for higher plants, and plant productivity is to a large extend determined by nitrogen nutrition. Effects of nitrogen nutrition on levels of polyamines in leaves and grappes of two vines (Semillon and Sauvignon) are studied at different stages of their development (flowering, fruit set process, veraison and maturity). Two N-fertilizations are compared : N0 (0 kgN/ha/year) and N90 (90 kgN/ha/year). Analysis concerned the total level of nitrogen and polyamines (free and conjugates). Polyamines (putrescine, spermidine, spermine and diaminopropane) were derived by dansylation and analysed by CLHP. The results show that N-nutrition induces major changes in the total level of nitrogen and polyamines in various parts of plants. In all organs, excess of N-nutrition increases the total level of nitrogen. Concerning polyamines, these changes differe according to tissue and stage of development. In flowers and green berries, N-excess increases free polyamines whereas in berries during maturation N-excess increases total level of polyamines and particularly free and wall-bound polyamines. In opposite, in leaves, total level of polyamines increases under N-deficiency. These results reflect different rates of metabolism of polyamines between tissues. They suggest that in berries a restricted polyamines synthesis induced by nitrogen deficiency; whereas in leaves, N-deprivation can induce an accumulation of putrescine as do many others stress. The roles of polyamines in berries and in leaves are discussed.

Aim: To better understand the protein composition of grape skin cell walls, we have developed a method to analyse the strongly bound cell wall proteins.Methods and results: The protocol was developed with grape skins at full maturity. The critical steps of this protocol were : (i) the elimination of cellular aggregates, (ii) the elimination of soluble proteins, and (iii) the localization of the identified proteins within the cell wall. To verify whether these three conditions were met, the decrease in the quantity of cellular aggregates was followed by optical microscopy, the removal of soluble proteins was measured by chemical assay, and the presence of proteins located in cell walls was demonstrated by extensive bioinformatic analysis. The process made it possible to obtain a four-fold reduction in the amount of cellular aggregates, a reduction in the concentration of soluble proteins below the method detection limit, and a high proportion of proteins predicted to be secreted (79 %).Conclusion: The protocol described in this paper constitutes the first method to analyse proteins strongly bound to cell walls in grape skins. However, this method excludes the identification of labile proteins or proteins weakly bound to the cell wall.Significance and impact of the study: This protocol can be used for studying the role that strongly bound cell wall proteins play in development and defense processes in grape skins.