From grapes to a deep knowledge of wine production: sardinian cultivars and the case study of Cannonau

Vitis vinifera L. is largely diffused in Sardinia, where it occurs as both a spontaneous wild plant (V. vinifera subsp. silvestris) and a crop (V. vinifera subsp. vinifera). The huge number of grapevine cultivars is the result of the complex history of Sardinia. The island was part of the Spanish Empire from 1479 to 1714 when commercial and cultural exchanges between the two regions caused modifications of its agricultural products. Noticeably, in the case of viticulture, Spanish and Sardinian grapevine varieties often have similar-sounding names; for example, ‘Bobal’ and ‘Bovale’, ‘Cariñena’ and ‘Carignano’, and ‘Garnacha’, ‘Granaccia’ and ‘Granazza’. We may assume that, due to politic and economic relationships, exchanges of grape varieties could have been occurred thus improving the genetic composition of the local germplasm. At the same time, certain Sardinian cultivars, some of which derived from the domestication and cultivation of wild local grapevines, could have been introduced in Spain. The first aim of our work was to evaluate the genetic structure of grapevine germplasm of Sardinia and its relationships with Spanish cultivars. Simple Sequence Repeat (SSR) markers were analyzed to characterize each accession and to study the relationships between Sardinian and Spanish cultivars. Results suggest the occurrence of synonymies such as ‘Cannonau’ and several Spanish accessions of ‘Garnacha Tinta’. If genetic origin of cultivars is an element useful for assessing wine traceability, wine quality relies on different factors and it is largely influenced by the environmental conditions of the production area. The second goal of this study was to develop an multidisciplinary approach for the characterization of 'Cannonau' wine produced in different Sardinian localities. We conducted a high-throughput sequencing analysis of different samples to understand the relationship between wine identity and the microbiome, specifically concerning bacteria and fungi. Since microbiome depends on different conditions, we planned a sampling able give us a lot of information: different grapes of the same cultivar, cultivated with traditional and biodynamic agriculture, in different regions of the island characterized by different type of soil; musts pre-fermentation and post-fermentation in different wineries, with or without starter (S. cerevisiae). Research on wine microbiome focuses primarily on those microorganisms influencing wine quality and determining its organoleptic properties. Such properties are mainly due to secondary metabolites that are produced while grapes ripen and then due to fermentation. For this reason, each sample collected was also analyzed for metabolomic characteristics, by Nuclear Magnetic Resonance. Analyses of microbial distribution and of the interactions occurring within and between bacteria and fungi, can represent the key of identification of Sardinian wines identity. In addition, the integration of metabolomic data can permit the identification of specific characteristics of each Sardinian wine. This type of study belongs to Foodomics, a new comprehensive approach to food and nutrition. The described integrative approach could represent a valuable tool for a better characterization of other foods and beverages, even including their transformation, storage, safety and their impact on human health.