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IVES 9 IVES Conference Series 9 Sugar loading and phenolic accumulation as affected by ripeness level of Syrah/R99 grapes

Sugar loading and phenolic accumulation as affected by ripeness level of Syrah/R99 grapes

Abstract

[English version below]

Le chargement et l’accumulation des sucres ainsi que la biosynthèse des phénols ont été étudiés sur la Syrah, dans le cadre d’un programme de recherche de paramètres qui permettraient de déterminer une ou plusieurs qualités de raisin en relation avec des styles de vins pour un terroir donné. La relation entre la dynamique d’accumulation des sucres et, en parallèle, la biosynthèse des phénols a été étudiée sur Syrah/99R plantée dans un vignoble situé sur la station expérimentale de ARC Infruitec-Nietvoorbij, Stellenbosch (Afrique du Sud). La cinétique des analyses a été réalisée depuis le stade post floraison (nouaison) jusqu’au stade sur-maturation. Les vignes sont conduites en Espalier (2,75m x 1,5m), les rangs sont orientés nord – sud, le vignoble est en pente orientée est. Une irrigation par micro aspersion est appliquée de la nouaison à la véraison. La hauteur de végétation est de 1,4 m, avec 3 hauteurs de fils de palissage. Les vignes sont ébourgeonnées, palissées et écimées. La dynamique d’accumulation des sucres par baie a été étudiée à l’aide d’un protocole développé par Deloire et al., 2004 (sous presse). La biosynthèse des phénols (tanins totaux et leur degré de polymérisation, proanthocyanidols et anthocyanes) a été étudiée par spectrophotométrie et HPLC pour les anthocyanes. Le sucre est utilisé comme indicateur des relations vigne – baie (relations source – puits).
Les tanins totaux (TT) de la baie sont synthétisés depuis l’anthèse jusqu’à la véraison. Leur concentration augmente durant la croissance herbacée des baies. Elle diminue en concentration de véraison à maturation, alors que durant cette période, la quantité de TT par baie est stable. Quand les sucres sont utilisés comme indicateur physiologique, il ressort clairement que la biosynthèse des anthocyanes évolue, par baie, jusqu’à ce que ces dernières atteignent un contenu en sucre de 20 – 21 °Brix. Après ce point, l’évolution des anthocyanes par baie est indépendante de l’évolution du contenu en sucre par baie, qui se fait alors essentiellement par concentration (perte d’eau de la baie). Le chargement actif des baies en sucre est dépendant de la photosynthèse des feuilles et la régulation du déchargement phloémien du sucre dans les baies semble en partie dépendante du microclimat des grappes et des baies elles mêmes. Le chargement actif en sucre de la baie n’est pas directement corrélé à son volume.

Sugar loading and phenolic accumulation in Syrah grapes were investigated as part of an elaborate study to determine parameters that would indicate high grape quality and different grape and wine styles on a particular terroir. The relationship between the dynamics of sugar loading and phenolic accumulation in the berries of a Syrah/R99 vineyard, situated at the ARC Infruitec-Nietvoorbij , in the Stellenbosch region (South Africa), was investigated from pea size stage (green berry) to late maturity. Vines were vertically trained and spaced 2.75 x 1.5 m in north-south orientated rows on a terroir with Glenrosa soil and a west-facing slope. Microsprinkler-irrigation was applied at pea berry size and at véraison stages. The 1.4 m high canopies were suckered, shoot-positioned and topped and accommodated by means of three sets of double wires. The dynamics of berry sugar loading were studied by a method from Deloire et al, 2004 (under publication), the berry phenolic composition (total tannins and polymerisation, proanthocyanidins, anthocyanins) was analysed by spectrophotometry and anthocyanins by HPLC. Sugar was used as physiological indicator of the plant-berry (source-sink) relationship and as bunch microclimatic indicator.
The total tannin (TT) component in the berry was synthesised from anthesis to véraison. The TT concentration increased during the green berry growth stages and decreased during ripening as the berry increased in volume. The TT per berry also increased during the green berry growth stages, but kept stable during ripening. When sugar content per berry is used as physiological indicator, it is clear that anthocyanin biosynthesis occurred until a specific berry sugar content, i.e. 20 – 21 0Brix, is reached. After this point, anthocyanin evolution per berry seemed independent of berry sugar evolution, which is at that time mainly due to concentration (berry water loss) than to loading. Thus, although berry sugar loading is dependent on photosynthetic activity of the leaves, the regulation of sugar phloem unloading in the berry sink seemed to be, in part, affected by the microclimate that the berry experienced. Berry sugar loading was not directly correlated with berry volume.

DOI:

Publication date: January 10, 2022

Issue: Terroir 2004

Type: Article

Authors

A. Deloire (1), E. Kraeva (1), M. Martin (2) et J.J. Hunter (3)

(1) Agro Montpellier, UMR 1083 « sciences pour l’œnologie et la viticulture », 2 place Viala, 34060 Montpellier cedex 1, France
(2) INRA, Unité expérimentale de Pech Rouge, 11430 Gruissan, France
(3) ARC Infruitec-Nietvoorbij, Private Bag X5026, 7599 Stellenbosch, South Africa

Contact the author

Keywords

Vitis vinifera, bunch, sugar, microclimate, indicator, vine functioning

Tags

IVES Conference Series | Terroir 2004

Citation

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