International Journal of Horticulture, 2024, Vol.14, No.4, 237-249 http://hortherbpublisher.com/index.php/ijh 245 flowering, with the soluble solid content reaching up to 21% Brix (Table 2). Although sweetness gradually decreases afterward, the soluble solid content remains around 18% Brix 50 days after flowering, demonstrating a good level of sweetness. Additionally, the scales of thornless yellow dragon fruit treated with chemical spraying remain relatively intact 60 days after flowering. In contrast, untreated fruit scales begin to dry out at the tips 30 days after flowering, with the scale quality gradually declining until they completely wither 40 days after flowering (Table 2). This chemical spraying method not only enhances the sweetness of thornless yellow dragon but also significantly extends the fruit's shelf life, ensuring its competitiveness and economic benefits in the market. Table 2 Evaluation of appearance and soluble solids content after tree treatment Group Indicators Days after flowering 20 d 25 d 30 d 35 d 40 d 45 d Treatment Group Weight (g) 370 424 487 510 515 517 Sweetness (% Brix) 11 15 17 21 20.5 20 Scale integrity Intact Intact Intact Intact Intact Intact Fruit surface color Green Yellow Yellow Yellow-green Green Green Control group Weight (g) 359 410 458 472 480 473 Sweetness (% Brix) 11 15 17 18 17 15 Scale integrity Intact Intact Dry tips Withered Withered Cracked Fruit surface color Green Yellow Yellow Yellow-green Yellow-green Yellow-green 4.2.4 Grafting method Studies on various horticultural crops have shown that grafting can significantly improve fruit quality, as seen in melons, cucumbers, and tomatoes (Turhan et al., 2018; Noor et al., 2019). In the cultivation of thornless yellow dragon, either direct seedlings or grafted seedlings can be used. Typically, red-pulp dragon fruit is used as the rootstock for grafting. To analyze the impact of grafting on the sweetness of thornless yellow dragon, we measured the soluble solid content in the fruits of both direct seedlings and grafted seedlings. The results showed that the soluble solid content in different parts of the grafted seedling fruits was higher than that of the direct seedlings, with an increase ranging from 0.4% to 1.4% Brix (Figure 7). This indicates that grafting is an effective method for enhancing the sweetness of thornless yellow dragon. Figure 7 Content of soluble solids in different parts of thornless yellow dragon fruit Research has found that using different varieties of red-pulp dragon fruit as rootstock for grafting thornless yellow dragon can have varying impacts on fruit quality. For example, when using Xiangmi Dragon as the rootstock, the grafted thornless yellow dragon fruit has a dense texture with a certain degree of sandiness. In contrast, when using Fugui Red as the rootstock, this texture difference is not observed. These findings provide valuable
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