Mathematic model for simulating anthocyanin composition during grape ripening: another way of phenotyping

Zhanwu Dai, G. Hilbert, E. Gome?s, N. Bobeica, S. Poni, M. Ge?nard and S.Derlot

Proc. X Int. Symp. on Modelling in Fruit Research and Orchard Management.

Anthocyanins are responsible for grape color, an important quality factor for market acceptance. The relative proportion of cyanidin-based (cyanidin- and peonidin-derivatives) and delphinidin-based (delphinidin-, malvidin- and petunidinderivatives) anthocyanins largely determines the color variation among red/purple/blue colored grape varieties. Anthocyanin biosynthesis is under complex regulation by nutrients, hormones, and environmental cues sensed by the berry. However, the physiological mechanisms underlying these regulations are poorly understood. A dynamic model was developed to simulate the developmental anthocyanin composition in two genotypes and different carbon and nitrogen conditions. This model describes the flux partitioning by basic chemical reaction rules with total anthocyanin as input and reaction rates as parameters. Data were gathered from two experiments, which studied the developmental changes in anthocyanin composition. The model was calibrated for two cultivars under a given growth condition and then validated by applying the model to other conditions for the same cultivar. The model can successfully simulate all the observed modifications in anthocyanin composition throughout berry ripening. This provides an alternative way of phenotyping by dissecting a complicated trait (anthocyanin content and composition) into developmentally stable traits (model parameters).

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Combining innovation in vineyard management and genetic diversity for a sustainable European viticulture

Adam-Blondon Anne-Françoise

Impact, Volume 2017, Number 1, January 2014, pp 28-30 (3)


InnoVine is a European collaborative project funded through the Knowledge Based Bio-Economy (KBBE) program, launched in January 2013. During 4 years, it will involve 27 different partners from 7 European countries. The wine industry is a major economic sector through the European Union where wine production represented in 2010/2011 about 60% of the whole amount elaborated on the planet. Nowadays, European wine producers must face several key issues and challenges. Within few years, climate change will affect the balance between the area of production and grape varieties and will change the impact of pests and diseases in vineyards. Winegrowers also have to respect the environment while competing with other new producing countries on a globalized market. In this context, the strategic goal of the InnoVine project is to support the European wine industry by matching consumers' demands for top quality wines and food safety, citizen's requests for eco-friendly production methods and winegrowers technical needs in a climate change background.

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Water deficit effects on grapevine woody tissue pigmentations

D. Grossi, L. Rustioni, G. Simone Di Lorenzo, O. Failla, L. Brancadoro
Università degli Studi di Milano, DISAA – Dipartimento di Scienze Agrarie e Ambientali, Milano, Italy

Résumé: Water availability is an important environmental factor in viticulture. In a climate change context, vineyard management should be adapted to the new conditions. Drought-resistant rootstocks need to be selected. In this paper, reflectance spectroscopy is proposed as a new method to characterize the water stress effects on woody section pigmentations. Cabernet Sauvignon grafted on 4 different rootstocks (140Ru, 420A, M2 and M3) represented the plant material. Greenhouse controlled conditions allowed the comparison of well-watered (WW) and water-stressed (WS) plants. The physiological responses were characterized concerning daily water consumption, stem water potential, gas exchange, and plant growth. The water use efficiency was calculated and discussed as well. Spectroscopy analyses of woody sections indicated a major absorption band probably related to phenolic derivatives. Water stress produced characteristic spectrum modifications both in the Cabernet Sauvignon stem and in the rootstock xylem. These preliminary results encourage further studies addressed at the evaluation of drought-resistant genotypes, to distinguish their stress responses and to characterize the compositional aspects linked to drought tolerance.

Mots clés: Cabernet Sauvignon; Vitis; reflectance spectroscopy; rootstock; water stress

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Sensitivity of grapevine phenology to water availability, temperature and CO2 concentration

J. Martínez-Lüscher, T. Kizildeniz, V. Vu?eti?, Z. Dai, E. Luedeling, C. van Leeuwen, E. Gomès, I. Pascual,
J. Irigoyen, F. Morales, S. Delrot

Publié en juillet 2016 dans Frontiers in Environmental Science.

Résumé : In recent decades, mean global temperatures have increased in parallel with a sharp rise in atmospheric carbon dioxide (CO2) levels, with apparent implications for precipitation patterns. The aim of the present work is to assess the sensitivity of different phenological stages of grapevine to temperature and to study the influence of other factors related to climate change (water availability and CO2 concentration) on this relationship. Grapevine phenological records from 9 plantings between 42.75°N and 46.03°N consisting of dates for budburst, flowering and fruit maturity were used. In addition, we used phenological data collected from 2 years of experiments with grapevine fruit-bearing cuttings with two grapevine varieties under two levels of water availability, two temperature regimes and two levels of CO2. Dormancy breaking and flowering were strongly dependent on spring temperature, while neither variation in temperature during the chilling period nor precipitation significantly affected budburst date. The time needed to reach fruit maturity diminished with increasing temperature and decreasing precipitation. Experiments under semi-controlled conditions revealed great sensitivity of berry development to both temperature and CO2. Water availability had significant interactions with both temperature and CO2; however, in general, water deficit delayed maturity when combined with other factors. Sensitivities to temperature and CO2 varied widely, but higher sensitivities appeared in the coolest year, particularly for the late ripening variety, ‘White Tempranillo’. The knowledge gained in whole plant physiology and multi stress approaches is crucial to predict the effects of climate change and to design mitigation and adaptation strategies allowing viticulture to cope with climate change.

Mots-clés : climate change, viticulture, fruit development, ripening, chilling, dormancy, partial least squares regression.

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Stem xylem characterization for Vitis drought tolerance

L. Rustioni, A. Ciacciulli, D. Grossi, L. Brancadoro, O. Failla

Publié en juin 2016 dans le Journal of Agricultural and Food Chemistry.

Résumé : Together with stomatal conductance and root conductivity, the stem water reserve and transport systems could be regulatory mechanisms able to participate in the regulation of the plant water status. Lianas, such as Vitis spp., minimize the trunk support role, and stems have evolved to improve their ability in water transport. In this work, stems of 10 different Vitis species were studied in relation to their expected drought tolerance using reflectance spectroscopy. Spectra were measured before (T0) and after coloration with Sudan IV dye. The T0 spectral signature showed characteristic species features. The partial least squares (PLS) regression and the self-organizing map (SOM) neural network analysis were able to predict the expected drought tolerance score; thus, reflectance spectroscopy was demonstrated to be a useful technique for drought tolerance phenotyping. These methods could be applied for the preliminary selection of new rootstocks/cultivars. Wood composition variation appeared to be correlated with the water stress susceptibility. To clarify this relationship, the attention was focused on the wood hydrophobicity. Sudan IV is a microscopy dye traditionally used to underline suberin, waxes, and, in general, hydrophobic substances. Differences between rough and colored spectra evidenced the absorption band of Sudan IV with a maximum at 539 nm. The coloration intensity was used to develop a hydrophobicity index. The obtained values were correlated with the expected drought tolerance score. Therefore, hydrophobic compounds seem to play an important role in water use efficiency, and an hydrophobic barrier in the xylem tissue appears to be a protective mechanism against water stress.

Mots-clés : grapevine, water stress, rootstock, phenotyping, reflectance spectroscopy, suberin.

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Effect of anthocyanin absence on white berry grape (Vitis vinifera L.)

L. Rustioni, L. Rocchi, O. Failla

Publié en 2015 dans Vitis.

Résumé : In grapevines, white berried cultivars are characterized by the absence of anthocyanins, which are the main pigments in V. vinifera fruits. These varieties produce berries with a yellowish color. The pigments responsible of this hue are still not well defined. In this paper, spectrophotometric analyzes were carried out using non-invasive methods (reflectance spectra) and destructive quantifications (chlorophyll and carotenoid quantifications) to describe the variation in color of three white grape varieties during ripening. A decrease in chlorophylls and carotenoids was found. Changes in the proportion of blue (450-500 nm) and red (630?700 nm) absorption bands were underlined. The contribution of melanin-like pigments (oxidation products) is also discussed. In general, our results indicate that the yellow color of white cultivars is not related to the activation of specific biosynthetic pathways. It is most likely due to a series of catabolic processes (and to their relative intensity), which become visible and that are possibly stimulated by the anthocyanin absence.

Mots-clés : Vitis vinifera; grapevine; reflectance spectroscopy; pigments; melanin-like pigments

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Chlorophyll and carotenoid quantifications in white grape (Vitis vinifera L.) skins by reflectance spectroscopy

L. Rocchi, L. Rustioni, O. Failla

Publié en 2016 dans Vitis.

Résumé : In white grapes, chlorophylls and carotenoids play important roles in berry color and environmental interactions (e.g. radiative stresses). In this paper, easy, fast and low cost non-invasive reflectance methods have been tested and developed. Previously published indexes showed good performances for chlorophyll quantifications. However, in this work, new formulas able to discriminate chlorophylls a and b were also proposed. The wavelengths of major interest for the absorption detection were identified. Formulas based on the Gaussians half heights were proposed. In general, chlorophyll quantifications were obtained directly from reflectance spectra, while carotenoid absorption bands did not allow good reflectance correlations. However, the chlorophyll/carotenoid ratio (due to the pigments physiological linked roles) could be used to estimate carotenoid concentration. Their proportion changes during berry development, thus the index coefficients should be adapted in relation to the BBCH phenological phase. The obtained indexes demonstrated good correlations with the destructive quantifications. These methods could support further researches concerning cultivar classification and physiological studies

Mots-clés : photosynthetic pigments; non-invasive quantification; indexes; optical properties; grapevine.

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Adaptation of a plant pathogen to partial host resistance: selection for greater aggressiveness in grapevine downy mildew

Delmas C.E.L., Fabre F., Jolivet J., Mazet I.D., Richart Cervera S., Delière L. Delmotte F.

Publié en février 2016 dans Evolutionary Applications

Résumé : An understanding of the evolution of pathogen quantitative traits in response to host selective pressures is essential for the development of durable management strategies for resistant crops. However, we still lack experimental data on the effects of partial host resistance on multiple phenotypic traits (aggressiveness) and evolutionary strategies in pathogens. We performed a cross-inoculation experiment with four grapevine hosts and 103 isolates of grapevine downy mildew (Plasmopara viticola) sampled from susceptible and partially resistant grapevine varieties. We analysed the neutral and adaptive genetic differentiation of five quantitative traits relating to pathogen transmission. Isolates from resistant hosts were more aggressive than isolates from susceptible hosts, as they had a shorter latency period and higher levels of spore production. This pattern of adaptation contrasted with the lack of neutral genetic differentiation, providing evidence for directional selection. No specificity for a particular host variety was detected. Adapted isolates had traits that were advantageous on all resistant varieties. There was no fitness cost associated with this genetic adaptation, but several trade-offs between pathogen traits were observed. These results should improve the accuracy of prediction of fitness trajectories for this biotrophic pathogen, an essential element for the modelling of durable deployment strategies for resistant varieties.

Mots-clés: erosion; evolvability; fitness cost; host specificity; obligate plant pathogen; quantitative resistance; virulence;  Vitis vinifera

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Manipulation of ripening via antitranspirants in cv. Barbera (Vitis vinifera?L.)

Gatti M., Galbignani, M., Garavani, A., Bernizzoni, F., Tombesi, S., Palliotti, A., Poni, S.

Publié en janvier 2016 dans le Journal of Grape and Wine Research

Contexte et objectif : Accelerated berry sugar accumulation resulting in wines of excessive alcohol concentration, sub-optimal colour and atypical flavour has become increasingly frequent in warm growing districts, a trend induced by factors that include global warming. The application of a film-forming antitranspirant may be an effective way of reducing early sugar accumulation without affecting colour development.
Matériels et Méthodes : An antitranspirant emulsion was applied in 2013 and in 2014 on field-grown cv. Barbera vines at pre-flowering (PF), pre-veraison (PV) and at both dates (PFPV), and compared with the unsprayed control. Post-treatment assessment included seasonal gas exchange, yield components, growth of berry organs and must composition. Although all treatments were effective in reducing gas exchange by as much as 46% compared with that of the control, berry growth was not affected. Conversely, whereas PF slightly modified the ripening pattern, PV and PFPV markedly delayed accumulation of sugar in the warm 2013 season (?2.4 and ?3.7° Brix, respectively, vs control) without detriment to colour development because the onset of anthocyanins occurred at lower TSS. In the cooler, wet 2014 season, PV and PFPV were again able to delay sugar accumulation without affecting colour development.
Conclusions : Pre-veraison application of the antitranspirant alone or in combination with a PF spray proved effective in slowing sugar accumulation while avoiding concurrent delay of colour development.
Importance de l'étude: The use of antitranspirants is a practical and flexible way of regulating the sugar : anthocyanin ratio under conditions of excessively fast ripening.

Mots-clés : antitranspirant, berry growth, grape composition, source–sink management, sugar accumulation rate

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Estimation of total soluble solids in grape berries using a hand-held NIR spectrometer under field conditions

Urraca R., Sanz-Garcia A., Tardaguilac J., Diagoc M.P.

Publiié en septembre 2015 dans le Journal of the Science of Food and Agriculture

Contexte : Recent studies have reported the potential of near infrared (NIR) spectral analysers formonitoring the ripeness of grape berries as an alternative to wet chemistry methods. This study covers various aspects regarding the calibration and implementation of predictive models of total soluble solids (TSS) in grape berries using laboratory and in-field collected NIR spectra.
Resultats : The performance of the calibration models obtained under laboratory conditions indicated that at least 700 berry samples are required to assure enough prediction accuracy.Astatistically significant error reduction with P<0.001 was observed when measuring berries without epicuticular wax, which was negligible from a practical point of view. Under field conditions, the prediction errors (RMSEP=1.68?Brix, and SEP=1.67?Brix) were close to those obtained with the laboratory dataset (RMSEP=1.42?Brix, SEP=1.40?Brix).
Conclusion: Thiswork clarifies several methodological factors to develop a protocol for in-field assessing TSS in grape berries using an affordable, non-invasive, portable NIR spectral analyser.

Mots-clés : NIR spectroscopy; precision viticulture; non-invasive sensor; chemometrics; total soluble solids content

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First detection of the presence of naturally occurring grapevine downy mildew in the field by a fluorescence-based method

Latouche G., Debord C., Raynal M., Milhadec C., Cerovic Z.G.

Publié en Août 2015 idans Photochemical & Photobiological Sciences

Résumé : Early detection of fungal pathogen presence in the field would help to better time or avoid some of the fungicide treatments used to prevent crop production losses. We recently introduced a new phytoalexin-based method for a non-invasive detection of crop diseases using their fluorescence. The causal agent of grapevine downy mildew, Plasmopara viticola, induces the synthesis of stilbenoid phytoalexins by the host, Vitis vinifera, early upon infection. These stilbenoids emit violet-blue fluorescence under UV light. A hand-held solid-state UV-LED-based field fluorimeter, named Multiplex 330, was used to measure stilbenoid phytoalexins in a vineyard. It allowed us to non-destructively detect and monitor the naturally occurring downy mildew infections on leaves in the field.

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Differential responses of sugar, organic acids and anthocyanins to source-sink modulation in Cabernet Sauvignon and Sangiovese grapevines

Bobeica N., Poni S., Hilbert G., Renaud C., Gomès E., Delrot S., Dai Z.

Publié en Mai 2015 dans Frontiers in Plant Science

Résumé : Grape berry composition mainly consists of primary and secondary metabolites. Both are sensitive to environment and viticultural management. As a consequence, climate change can affect berry composition and modify wine quality and typicity. Leaf removal techniques can impact berry composition by modulating the source-to-sink balance and, in turn, may mitigate some undesired effects due to climate change. The present study investigated the balance between technological maturity parameters such as sugars and organic acids, and phenolic maturity parameters such as anthocyanins in response to source-sink modulation. Sugar, organic acid, and anthocyanin profiles were compared under two contrasting carbon supply levels in berries of cv. Cabernet Sauvignon and Sangiovese collected at 9 and 14 developmental stages respectively. In addition, whole-canopy net carbon exchange rate was monitored for Sangiovese vines and a mathematic model was used to calculate the balance between carbon fixation and berry sugar accumulation. Carbon limitation affected neither berry size nor the concentration of organic acids at harvest. However, it significantly reduced the accumulation of sugars and total anthocyanins in both cultivars. Most interestingly, carbon limitation decreased total anthocyanin concentration by 84.3% as compared to the non source-limited control, whereas it decreased sugar concentration only by 27.1%. This suggests that carbon limitation led to a strong imbalance between sugars and anthocyanins. Moreover, carbon limitation affected anthocyanin profiles in a cultivar dependent manner. Mathematical analysis of carbon-balance indicated that berries used a higher proportion of fixed carbon for sugar accumulation under carbon limitation (76.9%) than under carbon sufficiency (48%). Thus, under carbon limitation, the grape berry can manage the metabolic fate of carbon in such a way that sugar accumulation is maintained at the expense of secondary metabolites.

Mots-clés : Vitis vinifera L, wine alcohol content, wine color, climate change, leaf-to-fruit ratio, berry composition

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Comparison of whole-canopy water use efficiency and vineperformance of cv. Sangiovese (Vitis vinifera L.) vines subjected to a post-veraison water deficit

Merli M.C., Gatti M., Galbignani M., Bernizzoni F., Magnanini E., Poni S.

Publié en mars 2015 dans Scientia Horticulturae

Résumé: In the present paper a series of WUE expressions, including the physiological and agronomical, werecompared in potted cv. Sangiovese (Vitis vinifera L.) grapevines which were either well watered (WW) orsubjected to progressive post-veraison water stress (WS) by supplying decreasing fractions (i.e. 70%, 50%and 30%) of daily canopy transpiration (Tc) concurrently recorded via a plant-enclosure gas exchangesystem. While single-leaf intrinsic water-use efficiency (WUEi) increased with water stress severity,seasonal whole-canopy WUE were similar at pre-stress, 70% Tc, and upon rewatering but dropped duringsevere water stress. WUE calculated as mass of dry weight stored in annual biomass (leaves, canes andclusters) per liter of water used, did not differ on a seasonal basis, whereas WW and WS showed similargrape composition despite the latter suffered a 25% yield reduction. Results confirm that whole-canopyWUE is a much better index than single-leaf based WUE parameter for extrapolation to agronomic WUEand actual grape composition. Under our specific case study, due to high reactivity of Sangiovese toearly yellowing and shedding of basal leaves, it can be recommended that post-veraison water supply toSangiovese vines should not be lower than 70% of daily vine water use.

Mots-clés: Gas-exchange, Assimilation rate, Transpiration rate, Grape composition, Leaf-to-fruit ratio

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Chlorophyll role in berry sunburn symptoms studied in different grape (Vitis vinifera L.) cultivars

Rustioni L., Milani C., Parisi S., Failla O.

Publié en mars 2015 dans Scientia Horticulturae

Résumé : In grape berries, extreme oxidative stress results in skin tissue bleaching and brownish areas appearance.Thus, these damages could negatively affect the fruit quality and the commercial value. The paper focuseson the chlorophyll roles in sunburn symptoms appearance in white skinned grape berries. In the presentwork, 20 cultivars were studied in three phenological stages. Berries were kept under temperature andlight controlled conditions. Chlorophyll content and symptom appearance were quantified by reflectancespectroscopy indexes. The central role of radiation (and, thus, photo-oxidative damages) in berry sunburninjuries was underlined. Cultivars were classified, based on their susceptible or tolerant responses toradiation excess.

Mots-clés : abiotic stress, grapevine, optical properties, pigments, photo-oxidation, reflectance spectroscopya

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The isohydric cv. Montepulciano (Vitis vinifera L.) does not improveits whole-plant water use efficiency when subjected to pre-veraisonwater stress

Poni S., Galbignani M., Magnanini E., Bernizzoni F., Vercesi A., Gatti M., Merli M.C.

Publié en novembre 2014 dans Scientia Horticulturae

Résumé: Understanding how water use efficiency (WUE) changes under drought is crucial for interpreting adap-tive responses of species and cultivars to such abiotic stress. Several recent papers have concluded thatin grapevine these responses and the guidelines stemming therefrom can differ, depending upon theparameter chosen to express WUE. In the present paper a complete set of WUE expressions, includingthe physiological and agronomical, were compared in potted, fruiting cv. Montepulciano (Vitis viniferaL.) grapevines which were either well watered (WW) or subjected to progressive pre-veraison drought(WS) by supplying decreasing fractions (i.e. 70%, 50% and 30% of daily vine transpiration, Tg) determinedgravimetrically before vines were fully rewatered. While single-leaf intrinsic water-use efficiency (WUEi)increased with water stress severity, seasonal and diurnal whole-canopy WUE were similar at pre-stress,70% Tg, and upon rewatering but dropped in WS during severe water stress. Agronomic WUE calculatedas mass of dry weight stored in annual biomass (leaves, canes and bunches) per L of water used, wasalso lower in WS, whereas WS had similar must composition with WW despite a 37% reduction in theyield per vine. Results warn that whole-canopy WUE is a much better index than any single-leaf basedWUE parameter for extrapolation to agronomic WUE and actual grape composition. Under our specificcase study, it can be recommended that, to avoid significant profit loss, water supply to drought stressed Montepulciano at pre-veraison should not be lower than 70% of daily vine water use.

Mots-clés: Gas-exchange, Assimilation rate, Transpiration rate, Grape composition, Leaf-to-fruit ratio

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Water use efficiency in Sangiovese grapes (Vitis vinifera L.) subjected to water stress before veraison: different levels of assessment lead to different conclusions

Merli M.C., Gatt M., Galbignani M., Bernizzoni F., Magnanini E., Poni S.

Publié en septembre 2014 dans Functional Plant Biology

Résumé : Several recent papers have shown that in grapevine (Vitis vinifera L.), interpretation of responses to drought can differ depending upon the parameter chosen to express water use efficiency (WUE). In the present paper, a series of WUE expressions, including physiological and agronomical, were compared in potted grapevines (Vitis vinifera L. cv. Sangiovese) that were either well-watered (WW) or subjected to progressive drought before veraison (WS) by supplying decreasing fractions (i.e. 70%, 50% and 30% of daily vine transpiration (Trd) determined gravimetrically before vines were fully rewatered. Although single-leaf intrinsic and instantaneous WUE increased with water stress severity, seasonal and whole-canopy WUE were similar to that before stress, at 70% Trd and upon rewatering, but dropped during severe water stress. WUE calculated as mass of DW stored in annual biomass (leaves, canes and bunches) per litre of water used did not differ on a seasonal basis, whereas WS plants showed lower must soluble solids at harvest, and unchanged colour and phenolic concentration in spite of smaller berries with higher relative skin growth. Results confirm that wholecanopy WUE is a much better index than any single-leaf based WUE parameter for extrapolation to agronomic WUE and actual grape composition. In our specific case study, it can be recommended that water supply to drought-stressed Sangiovese grapevines before veraison should not be lower than 70% of daily vine water use.

Mots-clés: assimilation rate, gas exchange, grape composition, leaf-to-fruit ratio, transpiration rate

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Interactions of summer pruning techniques and vine performance in the white Vitis vinifera cv. Ortrugo

Gatti M., Garavani A., Cantatore A., Parisi M.G., Bobeica N., Merli M.C., Vercesi A., Poni S.

Publié le 18 octobre 2014 dans l'Australian Journal of Grape and Wine Research.

Résumé : The increasing interest by the wine market in sparkling white wines challenges how the desired grape composition can be achieved under the pressure of global warming. The aim of the present study was to assess the viability of summer pruning as a tool to pilot ripening towards desired compositional patterns. Ortrugo was subjected to basal leaf removal applied either at pre-flowering (ELR) or in lag-phase (LLR) and to bunch thinning (BT; removal of 50% of crop at lag-phase) in comparison with untreated control (C). Treatments induced large variation in bunch mass (30% less in ELR vs BT), yield per vine (37 and 21% less in BT and ELR vs C) and total soluble solids at harvest (BT scored 2.9°Brix higher than that of C). Conversely, given the same harvest date, all practices failed to maintain titratable acidity (TA) at the threshold of 6.5?g/L. The data suggest that crop regulation achieved in the high yielding Ortrugo, through either BT or ELR, increases sugar accumulation rate so that concurrent optimal TA level (?6.5?g/L) can be easily achieved by slightly anticipating harvest date. Under conditions of thermal or light stress, or weather conducive to bunch rot, preference should be given to ELR. Suitable summer pruning techniques might be used as flexible and powerful tools to direct ripening towards the desired crop composition.

Mots-clés : bunch thinning, grape composition, leaf area, leaf removal, yield

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Characterization of Grape (Vitis vinifera L.) Berry Sunburn Symptoms by Reflectance

Rustioni L., Rocchi L., Guffanti E., Cola G., Failla O.

Publié le 27 mars 2014 dans le Journal of Agricultural and Food Chemistry.

Résumé : Sunburn can affect grape quality both for chemical modifications and by visual impact of the browning. Optical properties of 17 white grape accessions were investigated in the visible region using a noninvasive instrument. Reflectance spectra were obtained using a Jaz System spectrometer. Browning was induced by exposing grape bunches to direct sunlight at 12:30 p.m. for 5 h. During the experiment, the global solar radiation ranged from 2.6 to 2.7 MJ m?2 h?1 and the air temperature from 24.3 to 29.2 °C; the exposed berries reached a temperature of 34.2 °C in comparison to the 30.4 °C of the shaded ones. Differences between the spectra of controlled and exposed berries mainly emphasized the loss in chlorophyll and the formation of brown compounds. A positive correlation between the chlorophyll concentration and berry browning was proposed. Developing rapid, noninvasive, and low-cost methods based on reflectance spectroscopy could support grapevine variety characterization with respect to sunburn susceptibility as well as study of the physiological processes involved in the symptoms’ appearance.

Mots-clés : Vitis vinifera, white grapes, browning symptoms, melanin-like pigments, sun exposure

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CUBA: An internet-based software application for berry anthocyanins units’ conversion for viticulturists, oenologists and physiologists

Cerovic Z.G., Latouche G, Nguyen H.K., Fadaili E.M., Le Moigne M., Ben Ghozlen N.

Publié en Avril 2014 dans Computers and Electronics in Agriculture

Résumé : In viticulture and especially for red wine production it is important to know the grape quality. Anthocyanins, the red pigments of berry skins that define the colour of wines, are good indicators of the so-called phenolic maturity of grapes. We provided an easily accessible mean to convert anthocyanins units acquired by different analytical methods. It is available as a free internet-based tool accessible from all supports, computers, tablets and smartphones. The usefulness of this software tool was illustrated by simulation of the influence of berry mass and skin mass per area on the anthocyanin content of the must.

Mots-clés : Viticulture, grapes, wine colour, phenolic maturity, fruits, Vitis vinifera

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The grape aquaporin VvSIP1 transports water across the ER membrane

Noronha H, Agasse A, Martins AP, Berny MC, Gomes D, Zarrouk O, Thiebaud P, Delrot S, Soveral G, Chaumont F, Gerós H.

Publié le 27 décembre 2013 dans le Journal of Experimental Botany

Résumé : Water diffusion through biological membranes is facilitated by aquaporins, members of the widespread major intrinsic proteins (MIPs). In the present study, the localization, expression, and functional characterization of a small basic intrinsic protein (SIP) from the grapevine were assessed. VvSIP1 was expressed in leaves and berries from field-grown vines, and in leaves and stems from in vitro plantlets, but not in roots. When expressed in tobacco mesophyll cells and in Saccharomyces cerevisiae, fluorescent-tagged VvSIP1 was localized at the endoplasmic reticulum (ER). Stopped-flow spectroscopy showed that VvSIP1-enriched ER membrane vesicles from yeast exhibited higher water permeability and lower activation energy for water transport than control vesicles, indicating the involvement of protein-mediated water diffusion. This aquaporin was able to transport water but not glycerol, urea, sorbitol, glucose, or inositol. VvSIP1 expression in Xenopus oocytes failed to increase the water permeability of the plasma membrane. VvSIP1-His-tag was solubilized and purified to homogeneity from yeast ER membranes and the reconstitution of the purified protein in phosphatidylethanolamine liposomes confirmed its water channel activity. To provide further insights into gene function, the expression of VvSIP1 in mature grapes was studied when vines were cultivated in different field conditions, but its transcript levels did not increase significantly in water-stressed plants and western-exposed berries. However, the expression of the aquaporin genes VvSIP1, VvPIP2;2, and VvTIP1;1 was up-regulated by heat in cultured cells.

Mots-clés : Aquaporin, protein purification, proteoliposomes, Vitis vinifera, VvSIP1, water transport

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Berry Phenolics of Grapevine under Challenging Environments

Teixeira A, Eiras-Dias J, D. Castellarin S, Gerós H.

Publié le 11 septembre 2013 dans l'International Journal of Molecular Sciences

Résumé : Plant phenolics have been for many years a theme of major scientific and applied interest. Grape berry phenolics contribute to organoleptic properties, color and protection against environmental challenges. Climate change has already caused significant warming in most grape-growing areas of the world, and the climatic conditions determine, to a large degree, the grape varieties that can be cultivated as well as wine quality. In particular, heat, drought and light/UV intensity severely affect phenolic metabolism and, thus, grape composition and development. In the variety Chardonnay, water stress increases the content of flavonols and decreases the expression of genes involved in biosynthesis of stilbene precursors. Also, polyphenolic profile is greatly dependent on genotype and environmental interactions. This review deals with the diversity and biosynthesis of phenolic compounds in the grape berry, from a general overview to a more detailed level, where the influence of environmental challenges on key phenolic metabolism pathways is approached. The full understanding of how and when specific phenolic compounds accumulate in the berry, and how the varietal grape berry metabolism responds to the environment is of utmost importance to adjust agricultural practices and thus, modify wine profile.

Mots-clés : agricultural practices; environmental challenges; genotype and environment interactions; grape berry phenolics; varietal diversity; Vitis vinifera

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