Timing of leaf removal effects on vitis vinifera L. Cv. Grenache differed on two contrasting seasons

Abstract

Context and purpose of the study – Warming trends over the winegrowing regions lead to an advance of grapevine phenology, diminution of yield and increased sugar content and must pH with a lower polyphenol content, especially anthocyanins. Canopy management practices are applied to control the source sink balance and improve the cluster microclimate to enhance berry composition. We hyphothesized that an early leaf removal might promote a delayed ripening through severe defoliation after fruitset; whereas, a late leaf removal at mid-ripening would reduce sugar accumulation.

Material and methods – The experiment was conducted with Vitis vinifera L. Grenache cultivar over the 2021 and 2022 seasons in a commercial vineyard in Alfaro, La Rioja, Spain. Grapevines were trained in a Globet system with three arms and 5 two-bud spurs. Experimental design was conducted as a complete block design with two leaf removal treatments differing in the moment of manipulation: i) severe leaf removal treatment conducted after fruit set (ELR); and ii) severe leaf removal after veraison (LLR) compared to an untreated control (UNT). Both leaf removal treatments consisted in the elimination of the basal leaves before the second internode. Each treatment had five replicates of 10 grapevines. Harvest commenced when berries reached commercial maturity (approximately, 26°Bx) and yield components were studied. At harvest, sample of berries were collected for berry mass and chemistry, color development and polyphenol profile determinations by UHPLC-MS/MS.