Application of satellite-derived vegetation indices for frost damage detection in grapevines

Cognac vineyard is mainly dedicated to brandy production. Within the vineyard restructuring context, one part is turned over wine varieties for wine production (about 1,500 ha planted from 1999 to 2005). Today, the new wine producers need technical references about qualitative potential of the « Charentes Terroir », varieties and adapted vineyard management.
In order to answer to this professional request, an observatory of 18 plots of Merlot and 12 plots of Sauvignon have been laid out since 2003 and 2004 on various kinds of pedoclimate.

Anthocyanins and phenolic compounds play a crucial role in winemaking, contributing to the profile, flavor, color, texture, and stability of wine. Grape clusters, specifically Vitis vinifera L. cv. Grenache, were handpicked from a commercial vineyard sited in Tudelilla, La Rioja, Spain (42°18′ 52.26″, Long. -2°7′ 59.15″, Alt. 582 m) on five distinct dates from veraison to harvest during the 2015 season. Non-contact spectral measurements were conducted on intact grape berries using a VIS-NIR spectrometer operating in the 570 – 1000 nm spectral range under controlled laboratory conditions, positioned at a distance of 25 cm from the berries. The quantification of 16 anthocyanins and phenols in 120 grape clusters was performed using HPLC, established as the reference method for validating the spectral tool.

The terroir is today the most important factor of production and development in the wine sector. In a context where the commercial challenge is taking place all over the place, the distinction between traditional and “new” producing countries is not only a geographical, cultural and technical counter position but also, and above all, a legal one. Indeed, the system of standards present in the “old world” (plantation rights, production decrees, yields per hectare, etc.) which may represent, in the short term on the global market, constraints to development and product innovation must become an opportunity. But threats become opportunities, if we work, from the vine to the market, via communication, more on the elements of difference than on those of affinity.

Alcoholic fermentation is the main step for winemaking, mainly performed by the yeast Saccharomyces cerevisiae. But other wine yeasts called non-Saccharomyces may contribute to alcoholic fermentation and modulate the wine aroma complexity. The recurrent problem with the use of these non-Saccharomyces yeasts is their trend to die off prematurely during alcoholic fermentation, leading to a lack of their interesting aromatic properties searched in the desired wine. This phenomenon appears to be mainly due to interactions with S. cerevisiae. These interactions are often negatives but remain unclear because of the species and strain specific response. Among the non-Saccharomyces yeasts, Lachancea thermotolerans is a wine yeast naturally found in grape must and well known as a great L-lactic acid producer and an aromatic molecules enhancer, but its behavior during alcoholic fermentation can be completely different in co-fermentation with S. cerevisiae in function of strain used.

In a context of reducing herbicide use, the most part of French vineyards are developing permanent grass cover crops on inter-rows alleys, while under the row chemical weeding remains the general case. The setting up of a controlled grass cover crop under the vine row could be a complementary alternative to mechanical weeding – which one is very restrictive – interesting from a technical and economical point of view. The present study aimed at assessing agronomic impacts of grass cover crop under the row in different climatic conditions and production objectives.