A one-year study was conducted in the Central Coast of California at a commercial vineyard to evaluate the effect of supplemental irrigation on dry-farmed Vitis vinifera L. cv. Zinfandel with varying vine ages during the 2021 growing season. The experimental block was historically dry-farmed on own-rooted Zinfandel vines, older vines were replaced as production quality decreased with a genetically identical scion grafted onto St. George (Vitis vinifera Scheel) rootstock. Six total treatments were included in this study, with Young vines (5 to 12 years old), Old vines (40 to 60 years old), and Control (2:1 ratio of old to young vines, and representation of the block). Each vine age treatment included both non-irrigated and irrigated vines, the total vine sample contained half irrigated and half non-irrigated. Irrigation was manually applied at véraison and véraison + 4 weeks, based on age-specific ETc, and to replenish 95% ETc. Results indicated no significant changes in phenological progression, leaf senescence, and physical berry analysis caused by supplemental irrigation during key developmental stages. Vine age was the primary driver of significant variation observed for most parameters. However, irrigated vines had slightly higher phenological progression leading up to harvest, although not statistically significant. Due to this minor trend, irrigated vines in each vine age group were harvested before the non-irrigated vines starting with young, control, and old vines. Additionally, lower leaf water potential was found at pre-dawn during the second irrigation application at véraison + 4 weeks. Applying supplemental irrigation during the growing season resulted in no significant impacts on vine performance. Results suggest the potential for implementing a dry-farmed management in vineyards to help adapt to climate changes and water scarcity issues.

A two-year study was conducted at a commercial vineyard in California’s Templeton Gap AVA to evaluate the effect of vine age on viticultural, enological, and sensory attributes of Vitis vinifera L. cv. Zinfandel grapes and wines. The experimental block was dry farmed, conventionally managed, with own-rooted Zinfandel vines that, when determined unproductive, were replaced with new vines of genetically identical scion plant material grafted onto St. George (Vitis rupestris Scheele) rootstock. Treatments included Young vines (5 to 12 years old), Control (representative proportion of young to old vines in the block), and Old vines (40 to 60 years old). Results indicated Young vines progressed more slowly during berry formation and more rapidly during berry ripening than Old vines. Due to variation in the timing of sugar accumulation, Old vines were harvested 21 days after Young vines in 2019, and 9 days after in 2020. Old vines produced, on average between both seasons, 3.7 kg more fruit per vine than Young vines. Old vines also produced, on average between both seasons, 22.8 more clusters per vine than Young vines (5.41 tons/acre and 2.64 tons/acre, respectively). The larger vine capacity observed was attributed to Old vines having more arm, spur and dormant bud positions per vine than Young vines, in addition to larger trunk circumference and diameter. Vine age also had an effect on vine vegetative growth, with Old vines producing shorter internodes (25.5% decrease) and smaller shoot diameters (29.3% decrease) compared to Young vines. Young vines had higher mid-day stomatal conductance and tended to have higher mid-day photosynthetic rates, although no differences in corresponding pre-dawn measurements were found. While root architecture was similar between age groups, Old vines displayed greater rooting depths. Young vine wines had lower pH and titratable acidity than Old vine wines. Old vine wines were defined by a wider array and intensity of aromatics, including raisin, orange peel, black fruit and spices relative to Young vine wines which were defined by wet topsoil and pomegranate aromas. These results suggest the potential for greater yield and improved wine quality when extending the longevity of Zinfandel vineyards.

L’âge de la vigne et sa relation avec la qualité du vin sont des sujets d’intérêt récurrents, tant scientifiques qu’économiques. Les consommateurs et acteurs de la filière vitivinicole semblent s’accorder à propos de la capacité des vieilles vignes à produire des vins de caractère supérieur. Malgré les recherches en cours, la validité de ce point de vue reste débattue et les questions concernant les mécanismes à travers lesquels de vieilles vignes aboutiraient à des vins qualité supérieure restent nombreuses. Pour tenter d’y répondre, l’impact de l’âge des vignes sur la physiologie, la tolérance au stress hydrique, ainsi que la qualité des baies et du vin ont été étudiés dans un vignoble expérimental constitué de plants de Vitis vinifera L. cv. de matériel génétique identique (Riesling de clone Gm 239 greffé sur 5C Teleki) mais aux dates de plantation différentes.En 2014 et 2015, les vignes plantées en 2012 n’avaient pas encore atteint leur plein potentiel et avaient une productivité végétative et un rendement significativement inférieurs à ceux des vignes plantées en 1995 et 1971. Par ailleurs, les vignes plantées en 2012 n’ont pas été soumises au même traitement d’enherbement que les vignes plus âgées pendant cette période afin de prévenir une compétition excessive pendant leur établissement. La capacité inférieure de ces vignes et l’absence d’enherbement ont mené à une plus grande exposition des grappes à la lumière et une plus grande accumulation d’azote, ce qui s’est traduit par une plus grande concentration en acides aminés, monoterpènes, norisoprénoides, et flavonols en 2014 et 2015. Les années suivantes (2016 et 2017), le rendement et le poids des bois de taille de ces vignes, ainsi que la composition des baies, étaient comparables à ceux des vignes plus âgées. Les paramètres de maturité technologique (°Brix, l’acidité totale et le pH de moûts) n’ont pas été significativement affectés par l’âge des vignes. […]Des analyses sensorielles et chimiques ont été réalisées en 2017 sur des vins de millésimes précédents. Les vins des plus jeunes vignes ont été associés à des arômes de fruits mûrs et de l’arôme de pétrole typique du Riesling. Ces vins ont aussi été identifiés par de plus hautes concentrations de monoterpènes et norisoprénoides potentiels et de composés soufrés volatils, en 2014 et 2015 uniquement. Les profils sensoriels et chimiques de vins issus des vignes plantées en 1995 et 1971 étaient dépendants du millésime mais pas de l’âge des vignes. Les profils des vins produits en 2016 étaient en superposables pour les trois groupes d’âge.Les travaux décrits dans ce manuscrit de thèse sont uniques, du fait notamment que le vignoble dans lequel ils ont été conduits a été conçu spécifiquement pour étudier l’effet de l’âge de la vigne dans des conditions environnementales comparables. Une fois que les vignes les plus jeunes ont atteint leur potentiel fructifère et ont été conduites de la même manière que les vignes plus âgées, leur productivité, la composition de leurs baies et la qualité des vins qu’elles produisent ont convergé avec celles des deux autres groupes. Plus intéressant encore, des vignes âgées de 19 et 43 ans se sont comportées de la même façon tout au long de l’étude et ont abouti à des vins comparables en termes d’analyses sensorielles, ce qui va à l’encontre de l’idée reçue qui veut que les vignes les plus âgées produisent des vins de qualité différente.Des travaux précédents ont démontré que la productivité des vignes, quel que soit leur âge, pouvait être expliquée par les réserves de bois et par la taille du tronc. Pour avoir une meilleure idée des différences liées aux réserves, la technique dite « structure-from-motion with multi-view stereo-photogrammetry » (SfM-MVS) a été testée pour mesurer l’épaisseur des troncs et leur volume. Cette technique qui permet la création de modèles tridimensionnels géo-référencés et à l’échelle a pu générer des modèles précis de tronc de vignes plantées en champ. / Vine age and its relation to the quality of the wine are topics of recurring interest, both scientific and economic. Consumers and actors in the wine sector seem to agree on the ability of old vines to produce wines of superior character. Despite ongoing research, the validity of this point of view remains debated and questions about the mechanisms through which old vines would end up with superior quality wines remain numerous. To try to answer them, the impact vine age on physiology, tolerance to water stress, and berry and wine quality were studied in an experimental vineyard planted with Vitis vinifera L. cv. of identical genetic material (Riesling Gm 239 grafted on 5C Teleki) but planted in different years.In 2014 and 2015, the vines planted in 2012 had not yet reached their full potential and had a significantly lower vegetative productivity and yield than the vines planted in 1995 and 1971. Moreover, the vines planted in 2012 were not subjected to the same grass treatment as older vines during this period to prevent excessive competition during establishment. The lower capacity of these vines and the absence of cover crop led to greater exposure of clusters to light and greater nitrogen accumulation, which resulted in a higher concentration of amino acids, monoterpenes, norisoprenoids, and flavonols in 2014 and 2015. In the following years (2016 and 2017), the yield and pruning weight of these vines, as well as their berry composition, were comparable to those of the older vines. The parameters of technological maturity (° Brix, total acidity and must pH) were not significantly affected by vine age.Vines planted in 1995 and 1971 showed similar physiological characteristics throughout the study with the exception of a higher incidence of esca syndrome in the older group. This disease was responsible for the decline in the total yield of vines planted in 1971, but individual yield per vine was equivalent for both groups.Sensory and chemical analyzes were conducted in 2017 on wines from previous vintages. The wines of the youngest vines were associated with aromas of ripe fruit and the kerosene aroma that is typical of Riesling. These wines were also identified by higher concentrations of potential monoterpenes and norisoprenoids and volatile sulfur compounds in 2014 and 2015 only. The sensory and chemical profiles of wines from vineyards planted in 1995 and 1971 were dependent on the vintage but not on the age of the vines. The wine profiles produced in 2016 were overlapping for the three age groups.The works described in this thesis manuscript are unique, particularly because the vineyard in which they were conducted was designed specifically to study the effect of the age of the vine under comparable environmental conditions. Once the youngest vines reached their fruiting potential and were conducted in the same way as the older vines, their productivity, the composition of their berries and the quality of the wines they produce converged with those of the two other groups. More interestingly, vines aged 19 and 43 years behaved similarly throughout the study and resulted in wines comparable in terms of sensory analysis, which goes against the an idea that the older vines produce wines of a different profile.Previous studies have shown that the productivity of the vines, whatever their age, could be explained by the wood reserves and the size of the trunk. To have a better idea of differences linked to reserves, the structure-from-motion with multi-view stereo-photogrammetry (SfM-MVS) method was tested to measure trunk thickness and volume. The technique, which allows the creation of scaled, georeferenced 3D models based on photographs, was able to produce accurate models of field-grown grapevine trunks.