The frequency of wildfires has significantly increased in recent years, posing concerns for many grapegrowers and winemakers. Exposure of grapes to smoke can result in wines with notable smoky notes, which in severe cases are described as "smoke tainted". However, smoky aromas in wine are not a priori quality defects but may be considered desirable in some styles of wines, as also widely found and appreciated in many spirits. In this perspective, we summarize recent research on sources and assessment of smoky sensory attributes in wine and provide an outlook on opportunities for managing excessive smoky characters.

The sulfur compound phenylmethanethiol (PMT) has been associated with ’flinty’ and ’struck-match’ aromas in wine, and it is considered to be an important contributor to the flavour of certain white wine styles. Little is known about the factors driving the formation of this potent sulfur aroma compound during winemaking conditions, as well as the precursors/pathways that might be involved in its formation. In this study, we demonstrate that a range of practical winemaking strategies may have significant implications on the final concentration of PMT in wine. Specifically, the choice of yeast strain used to perform alcoholic fermentation was shown to modulate the formation of this ‘flinty’ compound under laboratory-scale conditions, and in the absence of oak. The nutritional level of the fermentation media was also found to significantly impact PMT formation by yeast, as nitrogen additions in the form of inorganic nitrogen promoted the formation of PMT. Finally, the potential role of both benzaldehyde and hydrogen sulfide as precursors to PMT formation was also explored, as well as the contribution of other alternative pathways.

This work investigated Syrah producers' conceptualisation of peppery wines from two different wine regions. For the study, a long-term memory approach was used; in addition, the effects of the region of origin, as well as the sensitivity of the participants to detect rotundone, were evaluated. A total of 101 winemakers from the Northern Rhone Valley (NRV) and Languedoc-Roussillon (LR) were interviewed face-to-face after they had participated in two 3-alternative forced tests to assess their ability to detect rotundone. As part of the interview, participants were asked to remember the last peppery red wine they had tasted, to provide technical information about that wine and, more generally, about practices enhancing this character in wine, and to give their overall appreciation of such peppery notes. Only minor differences were observed between participants with either low or high sensitivity to rotundone; in contrast, an important regional effect on the conceptualisation of peppery notes was observed. Experts from the NRV recognised this character as a marker of wines made from under-ripe grapes. Overall, they perceived this flavour as a positive attribute, notably at a moderate level, but some experts also perceived it negatively. For LR participants, peppery notes were associated with powerful, full-bodied wines from very ripe grapes produced in the South of France and were notably perceived as a positive character. Our results are particularly relevant for the wine community as they show that the conceptualisation of a given wine aroma characteristic by winemakers can strongly differ according to their region of origin.

Background and goals Grapes exposed to wildfire smoke and wine produced from contaminated grapes can be robustly identified through quantitative analysis of smoke exposure markers, volatile phenols, and phenolic glycosides (PGs). This assessment is based on comparison of data from suspect samples to concentrations of phenolic compounds typically found in non-smoke-exposed grapes and unoaked wines. Oak products for winemaking are typically heat treated and represent a major source of guaiacol and other volatile phenols in wine. Although contact with oak products is thought to contribute negligible concentrations of PGs, the lack of data from oaked wines confounds the identification of a potential risk of smoke taint development in wine when assessing commercially produced, oaked wine. Therefore, this study aimed to determine the typical concentrations of smoke exposure markers in commercially produced, oaked wine. Methods and key findings Commercially produced wines (20 to 30 each) of Cabernet Sauvignon, Chardonnay, Pinot noir, and Shiraz cultivars were sourced from Australian regions and vintages free from known wildfire smoke exposure. Gas chromatography-mass spectrometry and high-performance liquid chromatography-mass spectrometry demonstrated that syringol and guaiacol were relatively abundant in oaked wine, reaching concentrations of 200 mu g/L. In contrast, most PGs were <10 mu g/L, and trace concentrations of cresols were infrequently found. Conclusions and significance The concentrations of established wildfire smoke marker compounds (guaiacol, 4-methylguaiacol, syringol, 4-methylsyringol, o-cresol, m-cresol, p-cresol, syringol gentiobioside, 4-methylsyringol gentiobioside, cresol rutinoside, phenol rutinoside, guaiacol rutinoside, and 4-methylguaiacol rutinoside) were determined in oaked Australian Cabernet Sauvignon, Chardonnay, Pinot noir, and Shiraz wines. The data enable confident identification of smoke-affected wine that has been in contact with oak.

Proline has recently been found to direct several sensory attributes in red wine, including viscosity, fruit flavour and sweetness. We sought to investigate whether a red wine, deemed ‘flavour deficient’ by a producer, from a warm inland region could be improved by blending with a high proline wine from the same region, compared to a high colour and flavour wine, linking consumer acceptance with sensory properties and chemical composition. Three dry red wines (two Cabernet-Sauvignon wines from a warm region and one Lagrein wine from a cooler region) were blended in a constrained mixture design. Several blends were uncovered with improved sensory properties and consumer liking scores. Increased liking scores were related to heightened perceived Viscosity (unrelated to physical viscosity), Sweetness and Berry flavours, connected to proline-rich wines with small proportions of Lagrein. PLS-R models relating blend chemical composition, sensory properties and consumer acceptance associated Astringency and Bitterness to polyphenolics and organic acids and lower liking scores. Vegetal and Leather aromas in blends also reduced consumer acceptance and were related to the concentration of the thiols 3SH, 3SHA, PMT, 2FMT and MeSH, as well as guaiacol and isobutyl methoxypyrazine. Multiple blends successfully improved consumer acceptance of the ‘flavour deficient’ wine, particularly those with an increased proportion of the proline-rich wine. Non-linear effects resulting from blending were also assessed, with most variables modelled best by linear averaging. This study demonstrates the practical application of a design of experiment approach using sensory properties, proline and polyphenolic concentrations to guide wine blending and improve wine flavour and acceptability.

Background and Aims. A wide range of Chardonnay styles exist on the market, from fruit-forward examples to wines displaying "empyreumatic" aromas such as flint, smoky, mineral, and struck-match. The thiols 2-furylmethanethiol and phenylmethanethiol have been linked to these aromas, and this study aimed to determine the contribution of these compounds to specific sensory properties in Chardonnay wines, as well as the consumer acceptance of wine displaying "empyreumatic" aromas. Methods and Results. Twenty-four Australian and New Zealand Chardonnay wines were selected for volatile analysis and quantitative sensory descriptive analysis. Consumer liking of a subset of six wines was also determined, and a further sensory study involving additions of the thiols to a base wine was conducted. Partial least squares regression showed that flint/struck-match/mineral aromas were related to 2-furylmethanethiol concentration with phenylmethanethiol less well associated. The odorant addition study confirmed that 2-furylmethanethiol directed flint/struck-match/mineral aromas and exerted strong suppression of other aromas while phenylmethanethiol played a lesser role. Consumer acceptance (n = 92) was overall lower for wines displaying high flint/struck-match/mineral aromas, although cluster analysis of the liking scores identified a sizeable consumer group (33%) who preferred wines with this attribute. Conclusions. The potent thiol 2-furylmethanethiol was indicated to be the primary contributor to flint/struck-match/mineral aromas in Chardonnay wines, with phenylmethanethiol playing a subordinate role. Significance of the Study. Increased concentration of 2-furylmethanethiol and the conferred "empyreumatic" odours should be carefully considered when producing wine styles to appeal to consumers.

The winemaking by-product grape marc (syn. pomace) contains significant quantities of latent flavour in the form of flavour precursors which can be extracted and used to modulate the volatile composition of wine via chemical hydrolysis. Varietal differences in grapes are widely known with respect to their monoterpene content, and this work aimed to extend this knowledge into differences due to cultivar in volatiles derived from marc precursors following wine-like storage conditions. Marc extracts were produced from floral and non-floral grape lots on a laboratory-scale and from Muscat Gordo Blanco marc on a winery -scale, added to a base white wine for storage over five to six months, before being assessed using a newly developed membrane-assisted solvent extraction gas chromatography-mass spectrometry (GC-MS) method. The geraniol glucoside content of the marc extracts was higher than that of juices produced from each grape lot. In all wines with added marc extract from a floral variety, geraniol glucoside concentration increased by around 150–200%, with increases also observed for non-floral varieties. The relative volatile profile from extracts of the floral varieties was similar but had varied absolute concentrations. In summary, while varietally pure extracts would provide the greatest control over flavour outcomes when used in winemaking, aggregated marc parcels from floral cultivars may provide a mechanism to simplify the production logistics of latent flavour extracts for use in the wine sector.

Gas chromatography-olfactometry-mass spectrometry (GC-O-MS) has been very useful in identifying aroma compounds from within the complex matrix of wine. Supplementary separation can be required to overcome co-elution of volatiles or other sensory-directed chromatographic strategies are needed, including multidimensional chromatography and preparative fraction collection coupled to GC. Studies investigating ‘overripe orange’ aroma in sweet Sauternes wine and the similar ‘apricot’ aroma in Viognier wine were conducted. Wines with the targeted aroma attributes were selected and concentrated wine extracts prepared. GC-O found no individual aroma compounds with the targeted aroma attribute. Semi-preparative HPLC was used to obtain less complex fractions of the wine extracts. The fractions were eluted in water/ethanol and, therefore, could be smelled directly. Fractions with the targeted aroma character were further resolved by GC-preparative fraction collection (GC-PFC). Recombinational GC-PFC demonstrated the importance of the components within a 4 min preparative GC fraction to the ‘overripe orange’ aroma of typical Bordeaux dessert wine. In Viognier wine, monoterpenes linalool, α-terpineol and geraniol as well as benzaldehyde were found to be associated with the ‘apricot’ character. Thus, several wine aroma compounds interact for these specific aromas to be perceived. This sensory-led combination of separation techniques is a powerful tool for the identification of key compounds responsible for specific aromas across the wine and beverage industries.

(Z)-6-Dodeceno-gamma-lactone is a potent aroma compound that has been little studied and its prevalence in wines is unknown. An efficient stable isotope dilution assay was developed using a simple, direct immersion solid-phase microextraction and gas chromatography-tandem mass spectrometry method suitable for routine use with a low ng/L limit of quantitation. Using this method, 99 out of 104 young white wines analysed were found to contain detectable (Z)-6-dodeceno-gamma-lactone. The highest concentrations were found in Riesling and Viognier wines. (Z)-6-Dodeceno-gamma-lactone was found to have an aroma detection threshold of 700 ng/L in a neutral white wine. This study established that (Z)-6-dodeceno-gamma-lactone is widely present in Australia's most popular white wine varieties, but generally at concentrations below its aroma detection threshold.

The compounds in white wine that give rise to varietal ‘stone fruit’ aroma characters are not well understood. Relating the compositional differences among wines to their sensory attributes can help uncover the cause of specific sensory differences. Viognier and Chardonnay wines with differing levels of ‘stone fruit’ character, ranging from low to high intensity, were characterised by sensory descriptive analysis and comprehensive quantitative chemical analysis. Several aroma compounds were positively associated with the ‘apricot’ aroma attribute notable in some of the Viognier wines, including γ-lactones, monoterpenes and aldehydes. Sensory reconstitution experiments verified that a mixture of three monoterpenes, linalool, geraniol and nerol, was the most important group for the model to be perceived as having an ‘apricot’ attribute. Introduction ‘Stone fruit’ aroma attributes are important to many varieties of white wine, such as Chardonnay and Viognier. Some γ-lactones, monoterpenes and aldehydes have been reported as important aroma compounds in fresh stone fruits [1]. However, very little is known about the chemical basis of ‘stone fruit' aromas in wine. Previous Chardonnay wine sensory studies have included a ‘stone fruit’ descriptor but these studies did not focus on wines with clear ‘stone fruit’ aroma attributes. Little has been reported about aroma compounds in Viognier wine. Multivariate statistical techniques can be used to find relationships between compositional differences among wines to their sensory attributes [2]. Using an appropriate set of wines, highlighting the sensory attribute of interest, is more likely to provide well modelled predictions of the aroma compounds responsible for that attribute and to help determine if sensory difference is due to variation in concentrations of aroma compounds, an absence/presence of certain aroma compounds or an additive effect of several aroma compounds. To confirm or dismiss these predictions, reconstitution, addition and omission experiments in a realistic model are required [3]. Experimental Materials A set of 18 commercially available wines (six wines each: Australian Chardonnay; Australian Viognier; and French Viognier) were selected by a small group of experienced wine tasters from 75 potential wines to encompass a wide range of ‘stone fruit’ intensities. Sensory evaluation Descriptive sensory analysis was carried out on the wines using similar methodology to Mayr et al. 2014 [4]. A sensory panel, consisting of 10 trained panellists, rated the intensity of sensory attributes of the wines in triplicate under controlled conditions. Tracey E. Siebert et al. 246 Analysis of the volatile compounds Wines were characterised by comprehensive quantitative chemical analysis, targeting over 100 volatile aroma compounds using previously published methods [5-13] with stable isotope dilution analysis (SIDA-MS) and basic wine chemical composition. Statistical analysis Sensory panel performance was evaluated using Fizz, Senstools and PanelCheck software. Analysis of variance (ANOVA) was carried out using Minitab 17.1.0. Following ANOVA, Fisher’s least significant difference (LSD) value was calculated (P = 0.05). The sensory attribute ratings were related to chemical composition by partial least squares regression (PLSR) using The Unscrambler X software. Aroma reconstitution Preliminary model reconstitutions were promising for ‘apricot’ but not for ‘peach’. Therefore, only apricot was further investigated. Addition and omission descriptive sensory studies were conducted in a wine-like base model wine: ethanol (13.3 %v/v), tartrate (2 g/L), glucose/fructose (2 g/L), glycerol (4.6 g/L), citric acid (0.4 g/L), malic acid (2.6 g/L), succinic acid (0.6 g/L), SO2 (20 mg/L), pH 3.33 and food colouring. All models contained a mixture of 55 aroma compounds (mean concentrations of the 18 wines from the wine sensory study, Table 1). The aroma compounds predicted from the PLSR to be important to apricot were added as groups at the mean concentrations measured in the three wines with the highest intensity rating of apricot (Table 1). Sensory assessments were performed by a panel of eight in the same manner as for the wines, but only aroma attributes were assessed not palate. Table 1: Volatile compounds included in Control model reconstitution and concentrations of compounds that were included in the reconstitution study for ‘apricot’ aroma Compounds in Control model Addition to Control model μg/L 14 ethyl and acetate esters Lactones γ-nonalactone 5.9 5 alcohols γ-decalactone 1.2 8 fatty acids (Z)-6-dodeceno-γ-lactone 0.05 3 sulphur compounds Monoterpenes linalool 83 3-mercaptohexanol geraniol 27 8 oak-derived volatiles nerol 5.3 10 oxidation-related volatiles Aldehydes benzaldehyde 206 2,3-butanediol (E)-2-hexenal 0.37 α-terpineol, β-damascenone (E)-2-nonenal 1.8 γ-octa and γ-decalactone (E)-2-hexenol 3.2 6-amyl-α-pyrone Results and discussion Relationships between the sensory and chemical data The sensory descriptive analysis data established that the selected 18 wines had distinct descriptors of stone fruit aroma attributes, ‘apricot’ (tinned apricots) and ‘peach’ (fresh white peach), with widely differing intensity ratings. Notably, the two stone fruit attributes were not closely correlated. Why does this wine smell like apricots? 247 Of the 104 targeted wine aroma compounds, 79 were detectable and quantified in the 18 wines. The odour activity values (OAVs) of many of the aroma compounds were below 0.5. However, OAVs do not account for additive, synergic, antagonistic or perceptual interactions that might be occurring. Hence, all compositional measurements were used in the multivariate analysis. From the PLSR analysis, several aroma compounds were positively associated with the ‘apricot’ aroma attribute notable in some of the Viognier wines (Figure 1). γ-Nonalactone, γ-decalactone and the previously little studied and potent aroma compound (Z)6-dodeceno-γ-lactone were associated with the apricot sensory attribute, together with the monoterpenes linalool, geraniol and nerol, several aldehydes and (E)-2-hexenol. 3Mercaptohexyl acetate and trans-ethyl cinnamate were negatively correlated. In contrast, other wine aroma studies have generally reported monoterpenes to imbue ‘floral’, ‘citrus’ and ‘pine-like’ characters [14]. The ‘peach’ aroma attribute was associated with a range of fermentation-derived ethyl and acetate esters, fatty acids and monoterpenes (Figure 1). However, the association with monoterpenes was strongly influenced by a few Viognier wines rated highly in both ‘apricot’ and ‘peach’, thus confounding the ‘peach’ reconstitution model. Figure 1: PLSR of chemical composition and sensory data loadings plot: volatile aroma compounds that explain apricot and peach aroma attributes. Aroma reconstitution All models containing the monoterpenes were rated higher in ‘apricot’ than the Control model (Figure 2). However, the lactones did not increase the intensity of ‘apricot’. Aldehyde additions did not enhance ‘apricot’ scores (data not shown). ‘Peach’ aroma attribute intensities were not significantly different across the models. Tracey E. Siebert et al. 248 Figure 2: Mean ratings of ‘apricot’ aroma attribute in white wine reconstitution models. Compounds in the reconstitution models are listed in Table 1. Error bars are plus half LSD (P = 0.05). ‘Tropical’, ‘confection/floral’, and ‘cardboard’ aroma attribute intensities were significantly different across the models (p < 0.05) and the effects of the additions and omissions for these attributes were varied (data not shown). To our knowledge, this is the first time that this comprehensive approach has been used to identify the aroma compound(s) responsible for a particular wine aroma attribute from a set of wines specifically selected with that attribute. Subsequently, reconstitution studies confirmed that the mixture of the three monoterpenes linalool, geraniol and nerol, in the presence of ubiquitous wine compounds, was the most important group for the model to be perceived as having an ‘apricot’ attribute.

A 'stone fruit' aroma is important in many white wine varieties and styles, but little is known about the chemical basis of this wine aroma attribute. A set of Viognier and Chardonnay wines that featured 'stone fruit' aroma attributes were selected by a panel of wine experts. The selected wines were characterized by sensory descriptive analysis and detailed volatile chemical composition analyses. This comprehensive data also allowed Viognier wine to be profiled for the first time. By partial least-squares regression, several esters and fatty acids and benzaldehyde were indicated as contributing to the 'peach' attribute; however, a reconstitution sensory study was unsuccessful in mimicking this attribute. A mixture of γ-lactones, monoterpenes, and aldehydes were positively correlated to the 'apricot' aroma, which were generally higher in the Viognier wines. Reconstitution studies confirmed that the monoterpenes linalool, geraniol, and nerol were the most important compounds for the mixture being perceived as having an 'apricot' aroma.

Despite numerous studies, the identity of the compounds that are responsible for 'stone fruit' aroma in wine has not been conclusively established. This study focussed on wine varieties that often display peach and apricot characters, such as Chardonnay, Viognier and botrytis-affected sweet Semillon wines. Wines with high and low 'stone fruit' aroma were evaluated by gas chromatography-olfactometry-mass spectrometry (GC-O-MS) using extracts representative of the aroma of the wine in a glass. No aroma-active zone was described as 'stone fruit' aroma across all three wine varietals. However, for the individual varieties, terpenes, such as linalool and geraniol, in the Viognier wines, several esters in the Chardonnay wines, and γ-nonalactone in the botrytis Semillon were associated with 'stone fruit' aroma. Notably, this is the first study assessing the aroma profile of Viognier wine by GC-O. In addition, an extension study of Viognier grape monoterpene profiles clarified its classification as an aromatic variety.

The impact of fermentation variables (time and temperature of maceration, yeast species, addition of pectolytic enzymes) and winemaking techniques (cold soak, thermovinification, carbonic maceration, and rose vinification) on rotundone and classical enological parameters was investigated in triplicate in red wine made from Duras at the laboratory scale. Rotundone was poorly correlated to anthocyanins and to total phenolic index, some variables reflecting the extraction of skin compounds, which suggests that the solubility of rotundone or its ability to bind to other materials may differ from anthocyanins and most of the grape proanthocyanidins. Compared with control wine, wines made from a rose and a thermovinification treatment differed largely in their enological parameters. These two treatments involving a preferment removal of skins resulted in the lowest wine rotundone concentrations of similar to 20% and 13%, respectively. The other treatments had a weak impact on the studied parameters, and none of them, including the use of macerating enzymes and the increase in temperature or time of maceration, resulted in enhanced rotundone concentrations. Semicarbonic maceration, fermentation with Saccharomyces uvarum, or longer skin contact during postfermentation maceration resulted in wine with a significant decrease of similar to 20% in rotundone concentration, indicating practical opportunities for reducing pepper aroma in wine.

Rotundone, the compound responsible for peppery aroma in red wines is positively correlated with the absence of water deficit during ripening which can make it problematic to produce red wines combining both superior concentrations in rotundone and phenolic compounds. To reach, this double objective, on-vine drying with cutting of the fruit bearing cane or "Passerillage Eclaircissage sur Souche" (PES), a technique that consists in cutting the cane 2-3 weeks prior to harvest on a Guyot-trained vineyard was investigated combined or not with irrigation. We showed that PES had a limited impact on rotundone in wine. As the PES technique leads to an interruption of the sap flow, our results suggest that rotundone is synthesized in the berries and not translocated. A viticultural system combining irrigation and then PES induced significant gains in rotundone, in sugar concentration, in anthocyanins and in Total Phenolic Index in wine, and in skin to juice ratio. Measurements of bunch surface temperature indicate that the enhancement of totundone production induced by irrigation is likely to be due to a direct rather than to an indirect effect through an increase in leaf area leading to a cooler bunch microclimate. (C) 2016 Elsevier B.V. All rights reserved.

Terpenoids were extracted from grape vine bunches during plant development and analysed by GC-MSD. The grapevines analysed were from a commercial harvest of Vitis vinifera cv. Shiraz. The terpenoids were analysed from 4 weeks post flowering (wpf) to harvest in one season. The data are presented with the structure of the compound and aroma profile and semi-quantified. The sub-class of sesquiterpenes was given special attention, and this data set describes the first analysis of these compounds during ripening of this important economic crop. Sesquiterpenes may have a hitherto described contribution to wine aroma. This data set may provide insight into biosynthetic pathways and aroma chemistry. Interpretation of our data and further discussion can be found in "Terpene evolution during the development of Vitis vinifera L. cv. Shiraz grapes" (Zhang et al., 2016) [1].

The flavour of wine is derived, in part, from the flavour compounds present in the grape, which change as the grapes accumulate sugar and ripen. Grape berry terpene concentrations may vary at different stages of berry development. This study aimed to investigate terpene evolution in grape berries from four weeks post-flowering to maturity. Grape bunches were sampled at fortnightly intervals over two vintages (2012-13 and 2013-14). In total, five monoterpenoids, 24 sesquiterpenes, and four norisoprenoids were detected in grape samples. The highest concentrations of total monoterpenoids, total sesquiterpenes, and total norisoprenoids in grapes were all observed at pre-veraison. Terpenes derived from the same biosynthetic pathway had a similar production pattern during berry development. Terpenes in grapes at harvest might not necessarily be synthesised at post-veraison, since the compounds or their precursors may already exist in grapes at pre-veraison, with the veraison to harvest period functioning to convert these precursors into final products.

Recent studies concerning the aroma of noble rot dessert wines revealed the importance of a well-known phenomenon in perfumery, the perceptual blending, to create the perception of “overripe orange” nuances. Thus, compounds associated with both oak wood aging (3-methyl-4-octanolide and eugenol) and Botrytis cinerea development under the form of noble rot (2-nonen-4-olide and γ-nonalactone) contribute to a specific aroma of great noble rot dessert wines through perceptual interaction phenomena. This synthetic perception phenomenon was established from reconstitution, addition, and omission sensory experiments, using wine extract fractions supplemented with the volatile compounds previously mentioned. To better understand the sensory impact of these compounds, the goal of this research was to study the contributions of enantiomeric forms of 2-nonen-4-olide and γ-nonalactone and the diastereoisomers of 3-methyl-4-octanolide. After multidimensional chiral chromatography analysis, the relative proportions of enantiomers or diastereomeric forms were first established and then sensory experiments were carried out using the reference compounds with isolated fractions from dessert wines. A dominance of the R form was established for 2-nonen-4-olide, which was correlated with wine aging, while the S form is more dominant in young dessert wines. Furthermore, the reconstitution experiments confirmed perceptual interaction phenomena and revealed the sensory contribution of (R)-2-nonen-4-olide and cis-3-methyl-4-octanolide concerning the “overripe orange” nuances, whereas no sensory impact for the γ-nonalactone isomers was observed.

Lists of the volatile and non-volatile annotated metabolites, classified according to the ANOVA analysis. The metabolites that significantly varied according to the vintage or the year (p-value

Aim: Few recent studies have been investigating the effect of clone on aroma compounds. The aim of this research work was to study the impact of certified clones from Vitis vinifera L. cv. Duras N on grape quality and rotundone, a sesquiterpene responsible for peppery aroma which has been reported recently in red wines made from this cultivar. Methods and results: The experimental site consisted of four consecutive rows, each row planted with one of the four certified clones of Duras N (554, 555, 627 and 654). For each clone, measurements were replicated on three experimental units per row. Each experimental unit consisted of twelve continuous vines. Rotundone concentration was measured in wines prepared by microvinification techniques (1-L Erlenmeyer flasks). For both vintages of study, rotundone concentrations were significantly higher in wines from clones 554 and 654 in comparison with clone 555, while clone 627 showed an intermediate level. In 2014, differences in powdery mildew (PM) severity on clusters were identified between the four clones and a positive logarithmic correlation (r2 = 0.58) was reported on the experimental site between rotundone in wines and PM severity on grapes. Conclusion: Our results found differences in rotundone concentrations in wines made from the four Duras N certified clones. The results also suggested that grapevine defence response to PM could enhance rotundone production in berries. Clonal differences in susceptibility to biotic stress, such as PM, might explain the differences observed in rotundone concentrations between the four studied clones. Significance and impact of the study: Our results may assist grape growers to produce high quality wines with a desired aroma attribute made from Duras N. One should consider planting clone 554 in order to promote high levels of rotundone in wines made from this cultivar.

BACKGROUND:The definition of the terroir concept is one of the most debated issues in oenology and viticulture. The dynamic interaction among diverse factors including the environment, the grapevine plant and the imposed viticultural techniques means that the wine produced in a given terroir is unique. However, there is an increasing interest to define and quantify the contribution of individual factors to a specific terroir objectively. Here, we characterized the metabolome and transcriptome of berries from a single clone of the Corvina variety cultivated in seven different vineyards, located in three macrozones, over a 3-year trial period.RESULTS:To overcome the anticipated strong vintage effect, we developed statistical tools that allowed us to identify distinct terroir signatures in the metabolic composition of berries from each macrozone, and from different vineyards within each macrozone. We also identified non-volatile and volatile components of the metabolome which are more plastic and therefore respond differently to terroir diversity. We observed some relationships between the plasticity of the metabolome and transcriptome, allowing a multifaceted scientific interpretation of the terroir concept.CONCLUSIONS:Our experiments with a single Corvina clone in different vineyards have revealed the existence of a clear terroir-specific effect on the transcriptome and metabolome which persists over several vintages and allows each vineyard to be characterized by the unique profile of specific metabolites.