Response to powdery and downy mildew of varieties with disease resistance genes (PIWI)

Climate change is leading to a rise in average temperature and in the frequency and severity of heatwaves, and is already significantly disturbing grapevine phenology and berry composition. With the evolution of the weather of Australian grape growing regions that are already warm and hot, flavonoids, for which biosynthesis depends on bunch microclimate, are expected to be impacted. These compounds include anthocyanins and tannins which contribute substantially to grape and wine quality. The goals of this project were to determine if berry tannin accumulation is sensitive to high temperature and to enhance knowledge on upper temperature limits for viable wine production, in turn informing critical timing for mitigation strategies.

The sensory definition of the aging bouquet of red Bordeaux wines has been shown to be structured around seven main aromatic nuances: “undergrowth”, “spicy” “truffle”, “fresh red- and black-berry fruits”, “liquorice”, “mint”, and “toasted” (1). Some of these descriptors are also used to describe the aromatic notes of old Champagnes (2) suggesting common volatile compounds between these two types of wine.

In red wines, anthocyanins evolve during the wine-making process and ageing. They react with other compounds (such as vinylphenols, acetaldehyde, pyruvic acid…) to form a stable family of compounds called pyranoanthocyanins. Furthermore, the oxidation process can modify the anthocyanic profile of a red wine. It is also interesting to evaluate the occurrence of the different subclasses of pyranoanthocyanins and to characterize their chemical properties. The first objective of this study is to evaluate the occurrence of the different groups of pyranoanthocyanins in an oxidised Merlot wine by a centrifugal partition chromatography strategy. The second goal is to evaluate their relative impact in red wines from Bordeaux region by measuring their concentrations.

Today, a variety of remote sensing tools are used to characterise plant performance. However, the vine is rarely studied, as a major crop specificity is canopy discontinuity. Registered images of the vineyard are anisotropic, therefore difficult to analyse.

Climate change has brought several impacts that are becoming increasingly intense during the last few years and put at risk the quality of the berries or even the plant’s sustainability. Such extreme climatic events impact the composition of the wine while modulating its quality and the consumer preferences (Tempère et al., 2019). The three most important changes that take place in the must are: 1) decrease acidity, 2) increase of the concentration of sugar, hence increase of alcohol in the wine, and 3) modification
of the sensory balance and the development for example of cooked fruit aromas.