GiESCO 2015 – Session 4: Grape berry, microclimate

The aim of this study was to find a method assessing non-destructively the maturity and anthocyanin concentration of Vitis vinifera L. cv. Pinot noir providing a tool to better estimate the variability within a vineyard. Besides the CIELa*b* using the visible reflectance spectrum and hyperspectral imaging (combining short- wave-infrared (SWIR) images and vis/NIR images), a hand-held optical sensor (Multiplex3® (Force-A, Orsay, France) based on chlorophyll fluorescence screening showed promising results. Indeed, a relationship between the Multiplex3 index and the anthocyanin concentration was already shown.

Variability of grape quality traits is encountered in vineyards between individual vines, between clusters within a single vine, and between berries of single bunches. While precision viticulture addresses systematic geologic and microclimatic variance within a vineyard, the within-vine and within-bunch variability are inaccessible to targeted management or selective harvesting.

Yeast assimilable nitrogen (YAN) in the grape must is a key variable for wine quality as a source of aroma precursors. In a situation of YAN deficiency, a foliar urea application upon the vine at veraison enhances YAN concentration and facilitates must fermentation. In 2013, Agroscope investigated the impact of leaf-fruit ratio on the nitrogen (N) assimilation and partitioning in grapevine Vitis vinifera cv. Chasselas following foliar-urea application with the aim of improving its efficiency on the YAN concentration.

An analysis of total polyphenols, anthocyanins, phenolic acids, stilbenes and antioxydative properties of grape berries of Vitis vinifera silvestris referred to Vitis vinifera sativa – Pinot noir and Syrah – revealed an interesting potential in some autochthonous wild vines, in particular the first one which was authenticated in the Ariège county of Pyrénées.

Sunlight and microclimate inside the clusters zone are key factors in berry development and must composition. In Mediterranean conditions (warm and dry climate), the use of porous systems can help plants establish a better leaf distribution inside the clusters area, providing more space and enhancing certain physiological processes, both in leaves (photosynthesis, ventilation, transpiration) and berries (growth and maturation).

Environmental factors affect grape production by impacting carbon acquisition, source-sink relationships, berry ripening processes and the resultant wines. At the fruit level, it is generally accepted that high irradiance enhances the synthesis of anthocyanins and flavonols.

Polyphenols fulfil a variety of roles in plants including antioxidant and UV-protective functions, and are also known to possess beneficial human health effects. In addition to the consumption of berries and vine making, Vitis vinifera leaves are also being used as food and for treating medical disorders. Leaf polyphenols are also key components in ensuring development and growth of the whole plant even under adverse environmental conditions.

Muscat grape cultivars are known for the strong aromatic properties they confer to wines. However, the strength of the aroma depends on multiple variables including variety, environmental conditions during the growth season and cultural practices.

The timing of grape picking is a critical point for to production of high quality wines. Berry growth and major solutes are routinely measured on a mix of randomly sampled berries, in order to characterize the advancement of ripening at the vineyard scale, and optimize the date of harvest with respect to the specific conditions of the millesime.

Vitis vinifera L., is a species of Vitis, native in many geographical areas all over the world, with thousand varieties. Grape seeds “ The heart of Vitis vinifera” has nutritional and medicinal value and its history is intimately entwined with the history of wine. They are waste product of the winery and grape juice industry.

The acid component of berries is an essential criterion for the quality and preservation of distillation wines of Cognac. It must be high enough to protect wine during the storage phase, awaiting distillation. Climate change observed in the Cognac region for several years impact on the acid component of the Ugni-Blanc berries with a slight decrease in malic and tartaric acid content.

Composition of grape berries, and consequently wine characteristics, can be deeply modified by late harvest (LH) or withering techniques. Alternatively, a practice called “Double Maturation Raisoned” (DMR) has been developed, consisting in the cut of fruit-bearing vine following by the “reasoned” harvest. DMR differs from late ripening or withering (W) techniques, mainly for what concerns water loss rates and re-programming of berry metabolism especially in clusters located below the cane cutting.

Vitis vinifera L. cv. Garnacha blanca (White Grenache) is the dominant grape variety in the D.O. Terra Alta (Tarragona, Spain), where it has been irrigated during recent years. However, there are no studies about the most suitable irrigation schedule and the consequences of advancing or delaying the vintage on White Grenache grape and its wine aromatic profile.

A field trial was conducted in central California on Merlot to determine the interaction of mechanical leaf removal (control, pre-bloom, post fruit set) and water amounts [sustained deficit irrigation (SDI) at (0.8) and regulated deficit irrigation (RDI) at (0.8–0.5–0.8) of vineyard evapotranspiration (ETc)] on productivity and berry skin anthocyanin content.

Rotundone is a grape derived aroma compound responsible for peppery notes discovered in 2008 in red wines. A recent study showed the link existing within the same block between grapevine water status and rotundone concentration in wines with higher levels recorded in grapes from vines experiencing low water deficit.