Tree Genetics and Molecular Breeding 2024, Vol.14, No.5, 229-238 http://genbreedpublisher.com/index.php/tgmb 230 canopy. These practices aim to balance the vegetative and reproductive growth of the vine, ensuring that the canopy is neither too dense nor too sparse. An optimal canopy density, often around three leaf layers, is advocated to minimize shading and enhance the microclimate for fruit development (Dry, 2000; Smart et al., 2017). The physiological basis of canopy structure in grapevines is rooted in the plant's need to optimize photosynthesis while minimizing stress factors such as excessive shading and poor air circulation. Canopy architecture, including the arrangement and density of leaves, directly influences the vine's ability to intercept light and regulate temperature and humidity around the fruiting zone. Practices such as shoot thinning and leaf removal are employed to modify the canopy structure, enhancing light penetration and reducing the risk of diseases like bunch rot. These adjustments can lead to improved reproductive performance and berry ripening, as seen in studies on varieties like Semillon and Shiraz (Pascual et al., 2015; Silvestroni et al., 2016; Wang et al., 2019). Light interception is a critical factor in grapevine canopy management, as it directly affects photosynthesis, the process by which plants convert light energy into chemical energy. The amount and quality of light reaching the leaves and fruiting zones determine the vine's photosynthetic efficiency and, consequently, its growth and fruit quality (Wedger et al., 2019). Canopy management techniques such as shoot positioning and leaf removal are designed to optimize light distribution within the canopy, enhancing photosynthetic activity and improving grape yield and quality. For instance, increased light interception through canopy porosity adjustments has been shown to positively impact berry composition and hasten fruit maturity, although excessive exposure can lead to flavonoid degradation (Torres et al., 2020; Petoumenou and Patris, 2021; Mataffo et al., 2023). 3 Techniques in Canopy Management 3.1 Pruning strategies Pruning is a fundamental technique in canopy management that significantly influences grapevine yield and quality. It involves the selective removal of certain parts of the vine, such as shoots, leaves, or clusters, to optimize the vine's growth and fruit production. Winter pruning is a common practice that helps control vine vigor and balance the ratio of fruit to foliage, which is crucial for maintaining grape quality (Collins et al., 2020). Pruning strategies can also include shoot thinning, which reduces canopy density and improves light penetration, thereby enhancing the microclimate around the fruiting zone (Dry, 2000). These practices are essential for managing the vine's energy distribution, ensuring that resources are allocated efficiently to produce high-quality grapes. 3.2 Training systems Training systems are designed to shape the grapevine canopy to optimize sunlight exposure and air circulation, which are critical for grape development and disease prevention. Different training systems, such as the Ruakura Twin Two Tier and the Te Kauwhata Three Tier, have been shown to influence canopy architecture and microclimate, thereby affecting yield and fruit composition (Smart et al., 2017). These systems help manage the spatial arrangement of shoots and leaves, reducing shading and promoting uniform ripening of grapes. By adjusting the geometry of the vineyard, training systems can also mitigate the effects of environmental factors, such as temperature and humidity, on grape quality (Pascual et al., 2015). 3.3 Leaf removal practices Leaf removal is a canopy management practice that involves the strategic removal of leaves to improve light exposure and air flow within the canopy. This technique is particularly effective in reducing the incidence of diseases like Botrytis cinerea by decreasing humidity around the fruit clusters (Wang et al., 2019; Mataffo et al., 2023). Leaf removal can be performed at different stages of grape development, such as pre-flowering or pre-veraison, to influence berry composition and ripening (Figure 1) (Gambetta et al., 2020). The removal of leaves can also affect the photosynthetic capacity of the vine, which in turn impacts the sugar accumulation and overall quality of the grapes. By carefully managing leaf area, growers can enhance the microclimate of the canopy, leading to improved grape quality and yield.
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