An operational model for capturing grape ripening dynamics to support harvest decisions

Grape ripening is a critical phenological phase during which many metabolites that impact wine quality accumulate in the berries. Major changes in berry composition include a rapid increase in sugar and a decrease in malic acid content and concentration. Its duration is highly variable depending on grapevine variety, climatic parameters, soil type and management practices. Together with the timing of mid-veraison, this duration determines when grapes can be harvested. Viticulturists and winemakers monitor the sugar-to-total acidity ratio (S/TA) during grape ripening and start harvesting grapes when this ratio reaches the optimum value for the desired wine style. The S/TA ratio evolves linearly as a function of thermal summation during the first four weeks following the onset of ripening. The linearity of the evolution of the S/TA ratio as a function of thermal time during the first four weeks following mid-veraison is applied in this study on two large data sets encompassing (1) 53 varieties studied during 10 years with two to four replicates for each combination of year and cultivar and (2) two varieties, cultivated on three soil types over 13 years. Grape ripening speed is highly variable. The effects of the year impact ripening speed more than the effects of the soil or the variety, although all three effects are highly significant. Grape ripening speed decreases with berry weight and also varies with vine water status. By using this approach, viticulturists and winemakers can assess four weeks after mid-veraison, for each individual vineyard parcel, at what speed grape ripening progresses. Combined with precise mid-veraison scoring, expertise from previous vintages and complementary approaches like sensory assessment of berries, it allows harvest date estimates to be fine-tuned. The results of this study can also be used to identify slow ripening varies, which are better performing in warm climates and, thus, better adapted to climate change

Variety-specific response of bulk stomatal conductance of grapevine canopies to changes in net radiation, atmospheric demand, and drought stress

In wine growing regions around the world, climate change has the potential to affect vine transpiration and overall vineyard water use due to related changes in daily atmospheric conditions and soil water deficits. Grapevines control their transpiration in response to such changes by regulating conductance of water through the soil-plant-atmosphere continuum. The response of bulk stomatal conductance, the vine canopy equivalent of stomatal conductance, to such changes were studied on Cabernet-Sauvignon, Merlot, Tempranillo, Ugni blanc, and Semillon vines in a non-irrigated vineyard in Bordeaux France. Whole-vine sap flow, temperature and humidity in the vine canopy, and net radiation absorbed by the vine canopy were measured on 15-minute intervals from early July through mid-September 2020, together with periodic measurements of leaf area, canopy porosity, and predawn leaf water potential. From these data, bulk stomatal conductance was calculated on 15-minute intervals, and multiple linear regression analysis was performed to identify key variables and their relative effect on conductance. For the regression analysis, attention was focused on addressing non-linearity and collinearity in the explanatory variables and developing a model that was readily interpretable.Variability of vapour pressure deficit in the vine canopy over the day and predawn water potential over the season explained much of the variability in bulk stomatal conductance overall, with relative differences between varieties appearing to be driven in large part by differences in conductance response to predawn water potential between the varieties. Transpiration simulations based on the regression equations found similar differences between varieties in terms of daily and seasonal transpiration. These simulations also compared well with those from an accepted vineyard water balance model, although there appeared to be differences between the two approaches in the rate at which conductance, and hence transpiration is reduced as a function of decreasing soil water content (i.e., increasing water deficit stress). By better characterizing the response of bulk stomatal conductance, the dynamics of vine transpiration can be better parameterized in vineyard water use modeling of current and future climate scenarios.COntinental To coastal Ecosystems: evolution, adaptability and governanc

Phenological model intercomparison for estimating grapevine budbreak date (Vitis vinifera L.) in Europe

Budbreak date in grapevine is strictly dependent on temperature, and the correct simulation of its occurrence is of great interest since it may have major consequences on the final yield and quality. In this study, we evaluated the reliability for budbreak simulation of two modeling approaches, the chilling-forcing (CF), which describes the entire dormancy period (endo-and eco-dormancy) and the forcing approach (F), which only describes the eco-dormancy. For this, we selected six phenological models that apply CF and F in dierent ways, which were tested on budbreak simulation of eight grapevine varieties cultivated at dierent latitudes in Europe. Although none of the compared models showed a clear supremacy over the others, models based on CF showed a generally higher estimation accuracy than F where fixed starting dates were adopted. In the latter models, the accurate simulation of budbreak was dependent on the selection of the starting date for forcing accumulation that changes according to the latitude, whereas CF models were independent. Indeed, distinct thermal requirements were found for the grapevine varieties cultivated in Northern and Southern Europe. This implies the need to improve modeling of the dormancy period to avoid under-or over-estimations of budbreak date under dierent environmental conditions. © 2020 by the authors

Phenological Model Intercomparison for Estimating Grapevine Budbreak Date (Vitis vinifera L.) in Europe

Budbreak date in grapevine is strictly dependent on temperature, and the correct simulation of its occurrence is of great interest since it may have major consequences on the final yield and quality. In this study, we evaluated the reliability for budbreak simulation of two modeling approaches, the chilling-forcing (CF), which describes the entire dormancy period (endo- and eco-dormancy) and the forcing approach (F), which only describes the eco-dormancy. For this, we selected six phenological models that apply CF and F in different ways, which were tested on budbreak simulation of eight grapevine varieties cultivated at different latitudes in Europe. Although none of the compared models showed a clear supremacy over the others, models based on CF showed a generally higher estimation accuracy than F where fixed starting dates were adopted. In the latter models, the accurate simulation of budbreak was dependent on the selection of the starting date for forcing accumulation that changes according to the latitude, whereas CF models were independent. Indeed, distinct thermal requirements were found for the grapevine varieties cultivated in Northern and Southern Europe. This implies the need to improve modeling of the dormancy period to avoid under- or over-estimations of budbreak date under different environmental conditions.This research was funded by the European Union’s Horizon 2020 Research and Innovation Programme, under the Clim4Vitis project: “Climate change impact mitigation for European viticulture: knowledge transfer for an integrated approach”, grant agreement no. 810176. It was also supported by FCT-Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020 and the French National Research Agency (ANR) in the frame of the Investments for the Future Program, within the cluster of excellence COTE (ANR-10-LABX-45)

Uncovering the role of berry maturity stage and grape genotype on wine characteristics: insights from chemical characteristics and volatile compounds analysis

In a climate change context and aiming for sustainable, high-quality Bordeaux wine production, this project examines the impact of grape maturity levels in various cultivars chosen for their adaptability, genetic diversity, and potential to enhance wine quality. The study explores the effects on wine composition and quality through sensory and molecular methods. We studied eight 14-year-old Vitis vinifera cv. grape varieties from the same area (VITADAPT plots 1 and 5): Cabernet Franc, Cabernet Sauvignon, Carmenère, Castets, Cot, Merlot, Petit Verdot, and Touriga Nacional. We examined three berry maturity stages from the 2022 vintage: mid-veraison (MV), mid-maturity (MM), 7 days before maturity (M-7), at maturity (M), and 10 days post-maturity (M+10). Classical composition parameters were monitored during maturation. Fine volatile compounds, including lactones, furanones, norisoprenoids, and carbonyls as ripening and over-ripening markers, were quantified in grapes and wines using SPME-GC-MS, while thiols were analyzed in wines by SPE-GC-MS/MS. For example, according to the maturity stages, a significant increase in alcohol content was observed, which varied depending on the grape genotype. The highest concentrations were found in Petit Verdot (13.78 g/L in M-7), Cabernet Sauvignon, Merlot, and Petit Verdot (15.21, 15.30, and 15.75 g/L in M) and Merlot (16.68 g/L in M+10). These values were directly related to the higher sugar concentrations found in their must during the evaluated periods. Total acidity and pH levels vary among cultivars and are also influenced by different maturation stages. Some cultivars show more significant changes over time, while others display more modest fluctuations. As expected, the pH values and total acidity in wines from different cultivars were inversely related. Concerning the analyzed volatile compounds, surprisingly, Petit Verdot exhibited the highest concentrations of γ-nonalactone, followed by Cabernet Sauvignon and Cot, at all maturity stages including M-7 (6.39, 3.90, 3.61 µg/L), M (20.98, 8.98, 6.05 µg/L), and M+10 (13.93, 12.40, 8.48 µg/L), respectively. Overall, this study offers a new method to assess varieties’ sensitivity to overripening and vital insights into the impact of berry maturity stage and cultivar on wine physicochemical traits and volatile compound profiles. These findings can be a foundation for future research aiming to predict or model wine’s chemical and sensory properties

J-Sci-Food-Agric

BACKGROUND: The accurate characterization of grapevine cultivars (Vitis vinifera) is crucial for grape growers, winemakers, wine sellers, consumers and authorities, considering that mistakes could involve significant damage to the wine economic system. To avoid any misunderstanding, morphological, molecular and chemical tools are developed to positively identify grape varieties. RESULTS: E-ε-viniferin is a stilbene dimer mainly present in the woody part of grapevine and present as a mixture of two enantiomers: (7aR, 8aR)-(−)-E-ε-viniferin (1) and (7aS, 8aS)-(+)-E-ε-viniferin (2). In addition to phenotypic and genotypic approaches, a chemotaxonomic method using E-ε-viniferin enantiomers as chemical markers of grapevine cultivars was investigated. The isolation and purification of E-ε-viniferin enantiomers by preparative high-performance liquid chromatography (HPLC) and chiral HPLC from 14 red and eight white grapevine cane cultivars enabled us to determine the proportion of each enantiomer and therefore to calculate the enantiomeric excess for each variety. The relative abundance of each E-ε-viniferin enantiomer permitted us to distinguish grape varieties, as well as to establish cultivar relationships and patterns through statistical analysis. CONCLUSION: This pioneering work highlighting the enantiomeric excess of E-ε-viniferin as a chemical marker of grapevine paves the way for further studies to understand what mechanisms are involved in the production of these enantiomers in grapevine

Varietal responses to soil water deficit: first results from a common-garden vineyard near Bordeaux France

In wine producing regions around the world, climate change has the potential to decrease the frequency and amount of precipitation and increase average and extreme temperatures. This will both lower soil water availability and increase evaporative demand in vineyards, thereby increasing soil water deficits and associated vine stress. Grapevines control their water status by regulating stomatal closure and other changes to internal plant hydraulics. These responses are complex and have not been clearly characterized across a wide range of different Vitis vinifera varieties. Understanding how vine water status responds to changes in soil water deficits and other variables will help growers modify vineyard design and management practices to meet their quality and yield objectives. Carbon isotope discrimination measurements of certain plant tissues have been shown to provide effective characterization of stomatal closure, while water potential measurements provide a well-proven measure of overall vine water status. Using replicated data collected from an experimental common-garden vineyard at the Institut des Sciences de la Vigne et du Vin (ISVV) near Bordeaux, France, this project will analyze the effects on carbon isotope discrimination across 39 varieties and water potential across eight varieties against estimates of soil water deficits made using a water balance model running on local meteorology and considering the phenology of each variety. Similar to the literature, preliminary analysis finds as soil water deficit increases, carbon isotope data suggests greater stomatal closure and water potential measurements indicate greater vine stress. For both parameters, analysis will be performed to distinguish any difference in these responses between varieties

Varietal responses to soil water deficit: first results from a common-garden vineyard near Bordeaux France

In wine producing regions around the world, climate change has the potential to decrease the frequency and amount of precipitation and increase average and extreme temperatures. This will both lower soil water availability and increase evaporative demand in vineyards, thereby increasing soil water deficits and associated vine stress. Grapevines control their water status by regulating stomatal closure and other changes to internal plant hydraulics. These responses are complex and have not been clearly characterized across a wide range of different Vitis vinifera varieties. Understanding how vine water status responds to changes in soil water deficits and other variables will help growers modify vineyard design and management practices to meet their quality and yield objectives. Carbon isotope discrimination measurements of certain plant tissues have been shown to provide effective characterization of stomatal closure, while water potential measurements provide a well-proven measure of overall vine water status. Using replicated data collected from an experimental common-garden vineyard at the Institut des Sciences de la Vigne et du Vin (ISVV) near Bordeaux, France, this project will analyze the effects on carbon isotope discrimination across 39 varieties and water potential across eight varieties against estimates of soil water deficits made using a water balance model running on local meteorology and considering the phenology of each variety. Similar to the literature, preliminary analysis finds as soil water deficit increases, carbon isotope data suggests greater stomatal closure and water potential measurements indicate greater vine stress. For both parameters, analysis will be performed to distinguish any difference in these responses between varieties

Large gradient of susceptibility to esca disease revealed by long-term monitoring of 46 grapevine cultivars in a common garden vineyard

International audienceGrapevine (Vitis vinifera L.) is prone to many fungal diseases, including esca, a severe vascular disease threatening the wine sector and for which there is no cost-effective cure. Susceptibility to esca varies between cultivars in different infection conditions. It may therefore be possible to use the genetic diversity of grapevine cultivars to mitigate disease impact. However, the genetic component of esca susceptibility has rarely been investigated in the vineyard, and the specific mechanisms and varietal traits underlying esca susceptibility remain unknown. In this study, we monitored the incidence and severity of esca foliar symptoms and plant dieback (apoplexy and mortality) at plant level for seven years, on 46 cultivars planted in an experimental common garden, to separate the genetic component of esca susceptibility from the effects of environment and cropping practices. We observed a broad gradient of varietal susceptibility, with a mean incidence of 0 to 26 % of vines expressing esca foliar symptoms depending on the variety. This gradient remained similar across years and, unlike the severity of foliar symptoms, the incidence of grapevine dieback was significantly correlated with that of foliar symptoms. We detected a significant but weak and very localised phylogenetic signal for the incidence of esca foliar symptoms in this panel of cultivars. We then explored the relationships between epidemiological metrics and ecophysiological and phenological traits phenotyped on the same plot. Esca disease incidence was negatively correlated with δ 13 C across cultivars, suggesting that varieties with higher water use efficiency are less prone to the expression of esca symptoms on leaves. Moreover, the least vigorous cultivars were among the least susceptible, although this relationship was not significant. By contrast, neither phenological stages nor nitrogen status were significantly predictive of cultivar susceptibility to the disease. Together, these results provide new insight into the potential of genetic resources for use in the sustainable management of grapevine trunk diseases and open up new perspectives for studying the pathological and physiological determinants of their incidence