International Journal of Horticulture, 2025, Vol.15, No.6, 290-298 http://hortherbpublisher.com/index.php/ijh 294 which helps achieve improved fruit quality. The regulation of these enzymes and genes is among the main molecular mechanisms of leaf removal effects on sugar accumulation (Wang et al., 2021). 4.4 Sugar transport pathways and fruit accumulation mechanisms Sugar deposition in grape berries depends on efficient transport from source leaves to the sink tissues. Leaf removal, particularly in the cluster zone, triggers sugar transporter genes and enhances sugar transporter activity, allowing unloading and deposition of sugars in the fruit. The increased expression of genes such as VvSUC11 and VvSUC12, as well as sucrose metabolic enzymes, is conducive to the quick movement and hydrolysis of sucrose to hexoses within the berry. The sugar transport and metabolism process that is regulated organizes the delivery and storage of the assimilates effectively within the developing fruit, thus directly reaping the advantages of higher sugar content (Wang et al., 2021). 5 Key Factors Affecting the Outcomes of Leaf Removal 5.1 Genetic differences among grape cultivars Efficacy in leaf removal is, to a great extent, based on genetic difference among grape varieties. Differences in cultivar and rootstock can lead to diverse responses in yield, fruit setting, as well as factors such as sugar content and disease resistance (Yu et al., 2016; Cataldo et al., 2021). Other cultivars are also more susceptible to early defoliation, with larger yield losses or greater increases in soluble solids, while others react minimally. Genotype x management interaction is therefore a critical factor influencing the success of leaf removal practices (Lanati et al., 2021; VanderWeide et al., 2021). 5.2 Environmental conditions Environmental factors such as light, temperature, and water regime significantly impact the consequences of defoliation. Anthocyanin and flavonol production may be encouraged through higher light exposure caused by defoliation but can cause sunburn or degradation of delicate compounds under high heat. Water status also comes into play with leaf removal, as water stresses can augment or diminish the effects on yield and berry quality. Environmental stresses at various points prior to and following leaf removal will hence alter both the risks and benefits of such an operation (Cincotta et al., 2021; Yu et al., 2021; Yao et al., 2024; Verdenal et al., 2025). 5.3 Combination of timing and intensity of leaf removal When and how much to drop the leaves are critical factors that determine its impact on grapevine physiology and fruit quality. Early drop, e.g., pre-bloom or flowering, can restrict cluster compactness and disease but, in turn, reduce yield if excessive. Sooner removal nearer to veraison has lesser impact on yield but can also improve berry composition. The intensity of leaves removed must be properly controlled; moderate removal is most often optimal between enhancing quality and reducing risk, with excessive removal likely harming sugar accumulation and enhancing vulnerability to environmental stress (Aipperspach et al., 2020;Verdenal et al., 2025). 5.4 Coordination with other orchard management practices Leaf removal impacts also depend on how the practice is combined with other orchard management techniques such as cluster thinning, pruning, and irrigation. Combination of leaf removal with yield control techniques can attain an optimal leaf-to-fruit ratio, increasing fruit quality and reducing disease incidence. Alteration in canopy height or pruning levels can counterbalance removed leaf area and maintain vine equilibrium and productivity. Integrated management techniques that consider the interaction of multiple practices play a significant role in maintaining consistent and desirable results in grape quality and yield (Verdenal et al., 2024). 6 Research Progress and Regional Comparisons in Leaf Removal Studies 6.1 Major findings and case studies from international research Worldwide studies ever give evidence that leaf removal, especially pre-bloom, reduces bunch rot disease and °Brix total soluble solids in grapes and improves fruit quality. Meta-analysis of global research determined that pre-bloom leaf removal lowered bunch rot by 61% and Brix by 5.2%, and the most beneficial effects were found in cultivars and rootstocks that were sensitive to the practice. However, the impact on pH, titratable acidity,
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