Influence of the agronomic management on the aroma of Riesling wines

Over the next 25 years, the Intergovernmental Panel on Climate Change (IPCC 2013) predicts a ~20% increase in atmospheric carbon dioxide (CO2) concentration compared to the current level. Concurrently, temperatures are steadily rising. Grapevines, known for their climate sensitivity, will show changes in phenology, physiological processes and grape compositions in response. Investigating eco-physiological processes provides insights into the response of field-grown grapevines to elevated CO2 conditions. A Free Air Carbon Dioxide Enrichment (FACE) facility was established in the Rheingau region of Germany. Two grapevine varieties (Vitis vinifera L., cvs. Riesling and Cabernet Sauvignon) were planted, with the VineyardFACE comprising three rings with ambient atmospheric CO2 (approx. 400 – 420 ppm from 2014 to 2023, aCO2) and three rings with elevated CO2 concentration (+20% to ambient; eCO2).

Nowadays biodiversity loss is considered as a prior environmental issue. Agricultural landscapes are particularly concerned, mainly through the specialization and intensification of farming activities which lead, at a larger scale, to landscape simplification. Landscape management would be a good means to halt biodiversity loss, but large-scale studies remain rare. The life+ project BioDiVine aims to understand biodiversity dynamics and promote sustainable conservation actions at this scale in viticulture.

Grapevine yield is a key indicator to assess the impacts of climate change and the relevance of adaptation strategies in a vineyard landscape. At this scale, a yield model should use a number of parameters and input data in relation to the information available and be able to reproduce vineyard management decisions (e.g. soil and canopy management, irrigation). In this study, we used data from six experimental sites in Southern France (cv. Syrah) to calibrate a model of grapevine yield limited by water constraint (GraY). Each yield component (bud fertility, number of berries per bunch, berry weight) was calculated as a function of the soil water availability simulated by the WaLIS water balance model at critical phenological phases. The model was then evaluated in 10 grapegrowers’ plots, covering a diversity of biophysical and technical contexts (soil type, canopy size, irrigation, cover crop). We identified three critical periods for yield formation: after flowering on the previous year for the number of bunches and berries, around pre-veraison and post-veraison of the same year for mean berry weight. Yields were simulated with a model efficiency (EF) of 0.62 (NRMSE = 0.28). Bud fertility and number of berries per bunch were more accurately simulated (EF = 0.90 and 0.77, NRMSE = 0.06 and 0.10, respectively) than berry weight (EF = -0.31, NRMSE = 0.17). Model efficiency on the on-farm plots reached 0.71 (NRMSE = 0.37) simulating yields from 1 to 8 kg/plant. The GraY model is an original model estimating grapevine yield evolution on the basis of water availability under future climatic conditions.  It allows to evaluate the effects of various adaptation levers such as planting density, cover crop management, fruit/leaf ratio, shading and irrigation, in various production contexts.

After the onset of grape berry ripening, phloem unloading follows an apoplasmic route into the mesocarp tissue. In the apoplast, most of the unloaded sucrose is cleaved by cell wall invertases

Color is one of the key elements for the marketing of rosé wines due to their packaging in transparent bottles. Their broad color range is due to the presence of pigments belonging to phenolic compounds extracted from grapes or formed during the wine-making process. However, the mechanisms responsible for such diversity are poorly understood. The few investigations performed on rosé wines showed that their phenolic composition is highly variable, close to that of red wines for the darkest rosés but very different for light ones [1]. Moreover, large variations in the extent of color loss taking place during fermentation have been reported but the mechanisms involved and causes of such variability are unknown.