Les micro-zones et les technologies traditionnelles de la viniculture en Géorgie

Climate change imposes increasing restrictions and risks to Mediterranean viticulture. Extreme heat and drought stress events are becoming more frequent which puts in risk sustainability of Mediterranean viticulture. Moreover row crops e.g. grapevine for wine, are increasingly prone to the impact of more intense/longer exposure time to heat stress. The amplified effects of soil surface energy reflectance and conductance on soil-atmosphere heat fluxes can be harmful for leaf and berry physiology.

The characterization of « the soil effect » in vine growing is often limited to the description of the physical components of the terroir. Many works were done in this direction and corresponded to geological, pedological or agronomical approaches. However, if the physical environment influences the vine and its grapes, its effect becomes limited at the scale of exploitation. Thus, it could be important to consider how the viticulturist « translated » the potential.

The cultivated vine (Vitis vinifera) is the main species cultivated in the world to make wine. In 2017, the world wine market represents 29 billion euros in exports, and France contributes 8.2 billion (28%) to this trade, making it a traditional market of strategic importance. Viticulture is therefore a key sector of the French agricultural economy. It is in this context that the nutritional diagnosis of the vine is of real strategic interest to winegrowers. Indeed, the fertilization of the vine is a tool for the winegrower that allows him to influence and regulate the quality of the wine.

On the market there are several wine grapes which are tolerant to the main fungal diseases. These varieties, commonly defined “resistant”, were developed in the grapevine breeding programs carried out mainly in Germany, France, Hungary and Italy. Some of these cultivars have been included in the national catalogues of wine grape varieties and have sometimes been allowed for specific kinds of wine. The VEVIR project, aimed at the enological evaluation of resistant vines, involves 33 cultivars achieved at the State Institute for Viticulture Freiburg in Germany, the Research Institute of Viticulture and Enology Pecs in Hungary and the Fondazione Edmund Mach S. Michele all’Adige (FEM) in Italy.

There is a growing trend on the transition from conventional to agroecological management of vineyards. However, the impact of practices, such as reduced-tillage, organic fertilization and cover crops, is not well-understood regarding the soil microbial diversity, and its relationship with the soil physicochemical properties in the subsurface depth near the rooting zone. Soil bacterial diversity is an important contributor towards plant health, productivity and response to environmental stresses. A field experiment was conducted by sampling subsurface soil bacterial community (NGS and qPCR) near to the root zone of Macabeu and Xarel·lo vineyards, located at the Penedes. 3 organic (ECO) and 3 conventional (CON) vineyards, with more than 10 years of respective management were sampled (n=5 each plot). ECO practices did not affect bacterial and fungal abundance but increased significantly the ammonium oxidizing bacteria and alpha-diversity (Inv.Simpson). Interestingly beta-diversity was significantly affected by the management strategy. ANOSIM-tests revealed a significative effect of the management (ecological vs conventional) and plot, on the soil microbial structure (ASV abundance). Main phyla depicted were Proteobacteria, Actinobacteria and Acidobacteria, whose relative abundances were not affected by the management. EdgeR assay revealed a significant increase of Cyanobacteria and decrease of Gemmatimonadetes and Firmicutes phyla in ECO. Interestingly, the grapevine variety was not correlated with the soil microbial community structure. Mantel-test revealed an important correlation (Spearman) of some physicochemical parameters with the soil microbiota structure, in order of importance: texture, EC, pH Ca/Mg, Mg/P, K+, Mg2+, Ca2+, SO42-, and OM. N-NH4 and NTK, which were higher in the ECO managed soils, did not correlated significantly with the soil microbiome population. The results revealed the importance of combining a deep physicochemical characterization of each replicate with the microbial diversity assessment to gain better insights on the relationship between soil microbiome and vineyard management.