Vineyard canopy management techniques to cope with climate change

The recent climate report of the Intergovernmental Panel on Climate Change is worrying: the surface temperature of the globe was 1.09 Celsious higher in the period 2011-2020 than in the period 1850-1900 (IPCC, 2023). The excess heat of recent decades, combined with intense solar radiation and high vapour pressure deficits (VPD), are affecting viticulture in the Mediterranean area especially from the pre-veraison stage. As reported by several authors, when thermo-radiative excess crosses water deficiency, an explosive mixture results and the grapevine (Vitis vinifera L.) responds to this multiple stress through stomatal regulation. This behaviour, which is intended to reduce xylem vessel embolism, influences gas exchanges depending on phenological stage and cultivar. When stress worsens, vines experience photoinhibition and a subsequent drop in yield exacerbated by sunburn. This condition may also induce an acceleration of soluble solid accumulation (TSS) coupled with a faster depletion of organic acid and a consequent high pH that could trigger microbiological instability in the resulting musts. However, the effects of global warming not only affect technological maturity but also phenolics, such as total anthocyanin. High-temperature conditions suppress anthocyanin biosynthesis at both the transcriptional and enzymatic levels. To deal with these adverse effects, some short-term agronomic techniques have been implemented at the University of Bologna. Firstly, the post-veraison shoot trimming or apical leaf removal with the aim of coupling the TSS and total anthocyanin accumulation. These approaches are based on exploitation of carbon and nutritional competition between the developing organs. Secondly a new irrigation tool and foliar application of particle materials, such as kaolin and zeolite, to reduce canopy and berry temperature enhancing yield attributes and grape colour. Therefore, the purpose of this note is to highlight the strengths and weaknesses of the canopy management techniques in a changing climatic scenario.