Plant Gene and Trait 2025, Vol.16, No.3, 113-122 http://genbreedpublisher.com/index.php/pgt 116 operating space, and makes it easy to touch the vines and branches and damage the fruits (Da Costa Neto et al., 2019; Keller and Mills, 2021). A study compared row spacings of 2.44 meters and 2.74 meters and found that the former had a higher yield. However, being too narrow still brought problems of inconvenient mechanical harvesting, such as incomplete harvesting or more losses (Da Costa Neto et al., 2019). In addition, different types of harvesters (such as towed or self-propelled) perform differently at different row spacings. Therefore, when designing a vineyard, it is necessary to consider how to increase the yield by using high-density planting on the premise of ensuring the smooth operation of the machines. 4.3 Canopy management for efficient fruit detachment Under high-density planting conditions, it is particularly important to manage the grape canopy well. If the branches and leaves are too dense, the middle leaves will die, ventilation will deteriorate, humidity will increase, which is not conducive to fruit ripening and will also affect the fruit drop efficiency at harvest (Keller and Mills, 2021). Adopting some effective canopy management methods, such as mechanical pruning and appropriate leaf removal, can improve ventilation and light conditions, help fruits mature more evenly, and also reduce fruit loss at harvest. In addition, some precision agriculture technologies can now be used, such as visualization tools or near-infrared spectroscopy, to detect the difficulty of fruit drop in advance and adjust the harvesting parameters, thereby further improving the harvesting efficiency and fruit quality (Bono et al., 2019). 5 Impact on Fruit Yield and Grape Quality 5.1 Effects on yield components High-density planting will have a significant impact on the yield structure of grapes. Some studies have found that in the early stage of planting, if the plant spacing is relatively small, for example, only 0.91 meters, the yield per unit area will be relatively high. But over time, if the density is too high, it will instead cause the yield of each plant to decrease. The manifestations are that each fruit cluster becomes fewer, the number of fruit grains in each fruit cluster decreases, the weight of the fruit cluster reduces, and the fruit stalks are prone to damage, ultimately leading to a decrease in the total output (Brar and Bindra, 2015; Keller and Mills, 2021; Haque and Sakimin, 2022). In contrast, a moderate density, such as 2.0×2.0 meters, can ensure the yield per plant while also providing a decent yield per mu. It is a relatively ideal planting method (Brar and Bindra, 2015; Haque and Sakimin, 2022). In addition, excessive density can also easily cause grapevines to grow overly luxuriantly. The branches and leaves are too dense, which not only blocks light but also fails to ventilate, both of which will affect fruit development (Brar and Bindra, 2015; Keller and Mills, 2021). 5.2 Influence on soluble solids, acidity, and phenolic content In terms of fruit quality, high-density cultivation has little impact on some key indicators, such as sugar content (soluble solids), total acid and color. Some studies have found that at different densities, the differences in sugar content, acidity and color of grape juice are not obvious (Brar and Bindra, 2015; Keller and Mills, 2021). However, some studies have pointed out that appropriately controlling the yield can actually increase the sugar content of the fruit, especially when the yield drops to a certain range, such as controlling the yield at around 1 000 kilograms per 667 square meters, the sugar content will be higher. Overall, excessive density is prone to reduce quality, while moderate density is more conducive to the balance of sugar-acid ratio and the accumulation of phenolic substances (Haque and Sakimin, 2022). 5.3 Post-harvest quality retention and storage behavior High-density planting may also affect the storage capacity of grapes. Due to uneven fruit ripening and overly dense canolas, the microclimate in the orchard deteriorated, making the fruit stems more prone to spoilage and the fruits more likely to rot, resulting in a reduced storage capacity of grapes (Keller and Mills, 2021; Deng et al., 2024). Long-term high-density planting may also lead to a reduction in soil nutrients and a decrease in beneficial microorganisms, which will also affect the post-harvest quality and preservation time (Deng et al., 2024). Therefore, scientifically adjusting the planting density can not only improve the fruit quality at harvest, but also be conducive to extending the storage time and maintaining the market appearance of grapes (Haque and Sakimin, 2022; Deng et al., 2024).
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