Postveraison shoot trimming in Tannat and Merlot: preliminary results on yield components, plant balance and berry composition

REVINE is a 3 year European projected funded by PRIMA programme which proposes the adoption of regenerative agriculture practices with an innovative and original perspective, in order to improve the resilience of vineyards to climate change in the Mediterranean area. The potential for innovation lies in developing and combining new approaches that make agriculture more environmentally sustainable and enable a circular economy capable of improving farmers’ incomes. Primarily REVINE aims to improve soil health and biodiversity by promoting the multiplication of soil saprophytic microorganisms and the presence of useful microorganisms linked to the life cycle of the plant, such as rhizobacteria (PGPR) and fungi (PGPF) that promote plant growth which, in addition to increasing plant performance, increase tolerance to biotic and abiotic stresses.

Grapevine is one of the most-frequently phytosanitary treated crop systems. Consequently, restrictions have been applied by the European Commission on the number of pesticide treatments and the maximum quantity of copper fungicides allowed per year. Moreover, there is a need and an increasing demand for more ecological-sustainable agricultural products.
Seaweeds are currently used as fertilizers in viticulture, as they have been proven to be beneficial in several ways related to growth and nutrition.

The total global production of wine in 2021 was estimated at around 250 million hectoliters. The 30% of the total quantity of vinified grapes corresponds to wine by-products that represent nearly 20 million tons, of which 50% corresponds to the European Union. Wine by-products have been used for different purposes, in agriculture, cosmetics, pharmacy, biorefinery, feed, and the food

Water is the main limiting factor for yield in viticulture. Improving drought adaptation in viticulture will be an increasingly important issue under climate change. Genetic variability of water deficit responses in grapevine partly results from the rootstocks, making them an attractive and relevant mean to achieve adaptation without changing the scion genotype. The objective of this work was to characterize the rootstock effect on the diurnal regulation of scion transpiration. A large panel of 55 commercial genotypes were grafted onto Cabernet Sauvignon. Three biological repetitions per genotype were analyzed. Potted plants were phenotyped on a greenhouse balance platform capable of assessing real-time water use and maintaining a targeted water deficit intensity. After a 10 days well-watered baseline period, an increasing water deficit was applied for 10 days, followed by a stable water deficit stress for 7 days. Pruning weight, root and aerial dry weight and transpiration were recorded and the experiment was repeated during two years. Transpiration efficiency (ratio between aerial biomass and transpiration) was calculated and δ13C was measured in leaves for the baseline and stable water deficit periods. A large genetic variability was observed within the panel. The rootstock had a significant impact on nocturnal transpiration which was also strongly and positively correlated with maximum daytime transpiration. The correlations with growth and water use efficiency related traits will be discussed. Transpiration data were also related with VPD and soil water content demonstrating the influence of environmental conditions on transpiration. These results highlighted the role of the rootstock in modulating water deficit responses and give insights for rootstock breeding programs aimed at identifying drought tolerant rootstocks. It was also helpful to better define the mechanisms on which the drought tolerance in grapevine rootstocks is based on.

Context and purpose of the study. Climate change is a major challenge in wine production. It results in erratic weather conditions which may lead to a reduction in grape yield and the subsequent grape and wine quality.