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The characterization of proteins isolated from skin tissue is apparently an essential parameter for understanding grape ripening as this tissue contains the key compounds for wine quality. It has been particularly difficult to extract proteins from skins for analysis by two-dimensional electrophoresis gels and, therefore, a protocol for this purpose has been adapted. The focus was on the evolution of the proteome profile of grape skin during maturation. Proteome maps obtained at three stages of ripening were compared to assess the extent to which protein distribution differs in grape skin during ripening. The comparative analysis shows that numerous soluble skin proteins evolve during ripening and reveal specific distributions at different stages. Proteins involved in photosynthesis, carbohydrate metabolisms, and stress response are identified as being over-expressed at the beginning of colour-change. The end of colour-change is characterized by the over-expression of proteins involved in anthocyanin synthesis and, at harvest, the dominant proteins are involved in defence mechanisms. In particular, increases in the abundance of different chitinase and beta-1,3-glucanase isoforms were found as the berry ripens. This observation can be correlated with the increase of the activities of both of these enzymes during skin ripening. The differences observed in proteome maps clearly show that significant metabolic changes occur in grape skin during this crucial phase of ripening. This comparative analysis provides more detailed characterization of the fruit ripening process.

This work investigated the structural and biochemical changes during grape berry development which account potentially for the onset and increase in susceptibility to Botrytis cinerea. Using the cv. Sauvignon blanc, we quantified at seven developmental growth stages from herbaceous to over-mature berries: (1) fruit ontogenic resistance using three strains (II-transposa), (2) the morphological and maturity fruit characteristics and (3) preformed biochemical compounds located in the berry skin. From the mid-colour change stage onwards, susceptibility of unwounded fruit increased sigmoidally in both rot and sporulation severities at the berry surface. A principal component analysis identified a very close connection between fruit susceptibility and the level of fruit maturity. Berry susceptibility was significantly and positively correlated with the phenolic compounds in the skin cell walls and negatively correlated with the total tannin content in the skin and with water activity (Aw) at the fruit surface. On the berry, Aw decreased from 0.94 at bunch closure to 0.89 at berry maturity, with a relatively low value (0.90) at the stage of mid-colour change. Using artificial media, different Aw levels led to significant differences in mycelial growth (Aw ≤0.95 resulted in the lowest growth rate ≤0.34 mm day −1 ). Thus, besides the level of fruit maturity, both water activity on the fruit and the total tannin content in the skin may affect fungal growth and berry colonisation. The potential of these variables for use as indicators of grape berry susceptibility as well as associated mechanisms for the development of disease are discussed.

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.

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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 phytopathogenic fungus Botrytis cinerea produces a set of polygalacturonases (PGs) which are involved in the enzymatic degradation of pectin during plant tissue infection. Two polygalacturonases secreted by B. cinerea in seven-day-old liquid culture were purified to apparent homogeneity by chromatography. PG I was an exopolygalacturonase of molecular weight 65 kDa and pI 8.0 and PG II was an endopolygalacturonase of 52 kDa and pI 7.8. Enzymatic activity of PG I and PG II was partially inhibited by 1 mM CaCl2, probably by calcium chelation of polygalacturonic acid, the substrate of the enzyme.

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.Key words: abscisic acid, indol-acetic acid, hormonal balance, grape berry ripening, Vitis vinifera L.Objectif : L'objectif est de mieux appréhender les mécanismes impliqués dans la maturation de la baie de raisin, qui provoquent de profonds changements physiologiques et chimiques du fruit. Ainsi, nous nous sommes intéressés à l'implication de deux régulateurs de croissance : l'acide abscissique (ABA) et l'acide indole acétique (AIA) dans le contrôle du processus de maturation des baies.Méthodes and résultats : L'évolution de ces deux régulateurs de croissance a été suivi au cours du développement de baies de cépage Merlot (Vitis vinifera L.). Pour mieux comprendre le rôle de l'ABA et de l'AIA dans le processus de maturation, ces deux régulateurs de croissances ont été appliqués sur les baies au moment du déclenchement de la véraison. Le profil hormonal a été établi sur les baies traitées et différents paramètres physiologiques ont été testés afin d'évaluer les effets de ces deux applications. La répartition des deux régulateurs de croissance dans les baies non traitées montre que l'ABA et l'AIA s'accumulent au début de la véraison. De plus, il apparaît que les teneurs en ABA endogène diminuent progressivement dans la pulpe alors qu'elles s'accumulent dans la pellicule du début vérais...