How grape position on the vine impacts the quality parameters of grapes and must of <i>Vitis vinifera</i> L. cv. Agiorgitiko

Abstract Several factors can cause heterogeneity in the qualitative characteristics of grapes within the vine. There is little literature that identifies the changes caused by the position of the grapes relative to the points of the horizon. The purpose of this study was to evaluate the effect of grape position on the vine on the quantitative and qualitative characteristics of the grapes of grape cultivar Agiorgitiko ( Vitis vinifera L.), during the cultivation periods of 2021–2022. The experimental vineyard is located in Kouchi Nemea (Greece), where the vines are bilaterally cordon-trained (bilateral Royat) and the density of the vines is 4000 vines/hectare. The study was conducted in a Mediterranean climate, which is characterized by hot, dry summers and mild, wet winters. The sampling involved collecting samples from the side of the vine that receives the most sunlight during the day and the side that receives less. The results showed that the exposure of the grapes to sunlight in the morning (east side of the vine) or in the afternoon (west side of the vine) has a significant impact on the concentration and levels of many compounds such as phenolic compounds, acids and sugars, which could favour selecting harvesting, depending on the desired type of wine based on different phenolic profile. Evidently, the results of the study could very well vary in other climates and with the use of different grapevine cultivars. Significance of the study What is already known on this subject? The qualitative characters of the berries are influenced by many factors, such as environmental conditions, vegetation management and sun exposure. Sunlight exposure affects the composition of sugars, organic acids and phenolic compounds in the berries and grapes, which are key factors of their quality. However, the specific effects of the orientation of the canopy of the vines (east versus west side) in Mediterranean conditions, particularly amidst climate change remain unexplored, especially for cv Agiorgitiko. What are the new findings? The orientation of the canopy of the vines significantly affects both the physical and chemical properties of grapes and berries of cv Agiorgitiko. Grapes on the east side (exposed to the morning sun) had higher sugar content, lower acidity and increased anthocyanin concentrations, making them suitable to produce potential wines consumed fresh. Grapes on the west side (exposed to the afternoon sun) had higher levels of phenolics, flavonoids and antioxidant activity, indicating suitability for structured wines with ageing potential. What is the expected impact on horticulture? This study highlights the importance of grape position in defining the composition of grapes. Vineyard management strategies can exploit the orientation of the canopy of the vine for selective harvesting to produce different wine profiles from the same vineyard. This has implications for precision viticulture, promoting higher wine quality and market diversification through micro-harvest strategies.