Acetaldehyde-induced condensation products in red wines affect the precipitation of salivary proteins. Will this impact astringency?

Grapevine downy mildew (GDM), caused by the oomycete Plasmopara viticola, is one of the most destructive diseases of Vitis vinifera worldwide. All V. vinifera cultivars are susceptible to P. viticola infection, and epidemics can spread across an entire vineyard within a matter of weeks. Severe outbreaks cause substantial reductions in yield and fruit quality. Tracking GDM spread by manual scouting is time-consuming and unfeasible over large spatial extents.

Lactic acid bacteria (LAB) are essential microorganisms in winemaking due to their role in malolactic fermentation (MLF) [1]. This process not only ensures the biological stabilization of wine through the decarboxylation of malic acid into lactic acid but also contributes to modifications in the chemical composition of the wine [2][3].

Climate transition with frequent heat waves and long drought periods threatens grapevine productivity and wine quality in the Mediterranean regions. Microorganisms are known to contribute to plant fitness and to stimulate plant resilience against biotic and abiotic factors.
In this work, it was assessed the impact of long-term drought on soil microbiome associated to grapevine in open field in Alentejo, renowned Portuguese wine region.
Soil and plant tissues of drought tolerant Syrah cultivar exposed to three irrigation levels (100%- FI, 50%-DI ETc; rain-fed–NI) for 5 years were sampled for two years (2022-2023). Metabarcoding analysis of soil bacteria (16S V4 rRNA) and fungi (ITS sub-region) were integrated with soil physiochemical properties and leaves´ physiological data. Pre-dawn leaf water potential and stomatal conductance confirmed the imposed drought scenarios. Even though, α- and β-diversity of prokaryotic and eukaryotic microbial communities differed more by season than water availability, samples clustered according to soil water content and pH (p<0.05). Fungal communities show higher differences in the structure across treatments than bacteria. In 2023, 16 bacterial against 61 fungal ASVs were significatively different in abundance between NI and FI. Beijerinckiaceae, Bradyrhizobiaceae (Alphaproteobacteria) and Nocardioidaceae, Streptomycetaceae (Actinobacteria) families resulted to be significatively more abundant in NI, while Ascomycota, Basidyomicota and Mortierellomycota are the most important fungal phyla in NI. With culturomics data, this study aims to gather insights into how soil microbiome is remodelled under drought and contribute to select bacterial and fungal taxa with potential to mitigate drought stress in vineyards.

In recent years, consumer awareness for consuming healthy and environmental sustainability products has considerably increased [1]. In an ever-changing and highly competitive environment such as the wine sector, production of wines without sulfites, or biodynamic, organic or vegan wines, has experienced an important increase to meet the new needs of consumers [2,3]. Beyond these categories of regulated products, a new concept has emerged: natural wines (NW), for which there is not an established definition or legal regulation. Rather, producers have a personal idea of naturalness under the premise of applying minimal intervention from grape to wine production [4]. In this context, it is hypothesized that self-defined natural wines are different from conventional wines (CW) in their sensory and chemical profile. The predicament of natural wine is based on anecdotic declarations and assumes that minimal intervention guarantees the production of wines with organoleptic properties able to express the “terroir” and thus promote wine diversity, plurality and sensory typicity against the risk of standardization of CW.

The need to classify the vineyards of an area according to the quality of its wines is not recent, but it is only in the last ten years that studies on the suitability of different areas for the cultivation of vineyard take on an integrated and interdisciplinary character (Boselli, 1991). The definition of the suitability of the environment is thus obtained by making the climatic, pedological, topographical and cultural information interact with the vegetative, productive and qualitative expression of the grape varieties.