Tree Genetics and Molecular Breeding 2024, Vol.14, No.5, 229-238 http://genbreedpublisher.com/index.php/tgmb 231 Figure 1 Examples of the hydraulic buffering that occurs at veraison in grapevine (Adopted from Gambetta et al., 2020) Image caption: When a vine is subjected to water deficit, pre-veraison berries (i.e. green berries) are sensitive to drought-induced shriveling, and berries that are either undergoing veraison (A, B, reddish-green berries) or post-veraison (C, purple berries) are insensitive. Vines shown are under a very severe water deficit (Ψ stem<-1.5 MPa). Photos courtesy of Markus Keller (Adopted from Gambetta et al., 2020) 3.4 Shoot positioning and thinning Shoot positioning and thinning are critical components of canopy management that help control vine vigor and improve the light environment within the canopy. Proper shoot positioning ensures that shoots are evenly distributed and oriented to maximize sunlight interception, which is essential for photosynthesis and fruit development (Wang et al., 2019). Shoot thinning, on the other hand, involves the removal of excess shoots to reduce canopy density and improve air circulation, which can help prevent disease and promote uniform ripening (Silvestroni et al., 2018). These practices are particularly important in high-vigor vineyards, where excessive shoot growth can lead to shading and reduced fruit quality. By optimizing shoot density and arrangement, growers can enhance the overall performance of the grapevine, leading to better yield and grape quality (Mataffo et al., 2023). 4 Impacts of Canopy Management on Grapevine Yield 4.1 Quantitative effects on cluster and berry development Canopy management significantly influences the quantitative aspects of cluster and berry development in grapevines. Techniques such as shoot thinning, leaf removal, and cluster thinning have been shown to modify canopy architecture, which in turn affects light interception and microclimate within the canopy. For instance, shoot thinning and leaf removal can decrease the leaf area index, thereby increasing canopy porosity and enhancing light penetration, which positively influences berry ripening and cluster development (Wang et al., 2015). Additionally, the removal of lateral shoots and main leaves before flowering can lead to a reduction in yield potential, as observed in the Swiss white cultivar Petite Arvine, where intensive leaf removal resulted in a 47% decrease in yield potential (Silvestroni et al., 2016). Furthermore, the manipulation of canopy microclimate through practices like shoot number control and vigor management can optimize the balance between shading and light exposure, which is crucial for the development of clusters and berries (Smart et al., 2017). These practices not only affect the size and number of berries but also influence the rachis length, which is a key determinant of bunch compactness and overall yield (Petoumenou and Patris, 2021). 4.2 Long-term impacts on vine health and productivity The long-term impacts of canopy management on vine health and productivity are profound, as these practices can influence the physiological and structural aspects of the vine. Canopy management strategies such as shoot thinning combined with preanthesis defoliation have been shown to reduce leaf area and yield, but they also
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