International Journal of Horticulture, 2025, Vol.15, No.1, 8-20 http://hortherbpublisher.com/index.php/ijh 12 Consumer preference for pitaya is largely influenced by the sensory perception of its flavor, which is determined by the balance of sugars and acids. Studies have shown that consumers tend to prefer pitaya varieties with higher sugar content and moderate acidity, as these attributes contribute to a more pleasant and palatable taste (Wei et al., 2019; Constantino et al., 2021). The sensory attributes of pitaya, including sweetness, tartness, and overall flavor intensity, are key factors in determining its market acceptance and consumer satisfaction. 4.3 Regulatory mechanisms involved in sugar-acid interactions The metabolism of sugars and organic acids in pitaya is regulated by a complex interplay of genetic and environmental factors. Specific genes, such as those encoding for sugar transporters and metabolic enzymes, play crucial roles in the accumulation and distribution of sugars and acids during fruit development (Wei et al., 2019; Mou et al., 2022; Jiang et al., 2023). Environmental conditions, including temperature and storage conditions, also significantly impact the sugar-acid balance in pitaya. For example, fruits stored at lower temperatures tend to have lower sugar concentrations and higher acidity, affecting their taste quality. Hormonal regulation is another critical aspect of sugar and organic acid metabolism in pitaya. Hormones such as ethylene, auxins, and abscisic acid are known to influence fruit ripening and the associated metabolic pathways (Durán-Soria et al., 2020). These hormones interact with sugar signaling mechanisms to modulate the expression of genes involved in sugar and acid metabolism, thereby affecting the overall flavor and nutritional quality of the fruit (Li et al., 2018; Durán-Soria et al., 2020). For instance, methyl jasmonate (MeJA) treatment has been shown to enhance sugar metabolism and phenolic accumulation in pitaya, contributing to improved flavor and quality. 5 Factors Influencing Sugar and Organic Acid Metabolism 5.1 Genetic factors influencing metabolism Genetic variability plays a crucial role in determining the sugar and organic acid profiles in pitaya. Different pitaya species exhibit distinct sugar and acid compositions, which are influenced by the expression of specific genes. For instance, in yellow-peel pitayas, glucose is the dominant sugar in 'WCHL' pitaya, while sucrose, fructose, and glucose are prevalent in ‘YCHL’ pitaya. Malic and citric acids are the main organic acids in 'WCHL' and 'YCHL' pitayas, respectively (Xie et al., 2022). This genetic diversity underscores the importance of genetic factors in shaping the metabolic profiles of pitaya fruits. Several key genes have been identified that regulate sugar and organic acid metabolism in pitaya. The Dof transcription factors HpDof1.7 and HpDof5.4 are known to enhance the expression of sugar metabolism-related genes such as HpSuSy1 and HpINV2, as well as sugar transporter genes HpTMT2 and HpSWEET14, thereby facilitating sugar accumulation (Mou et al., 2022). Additionally, the WRKY transcription factor HpWRKY3 has been shown to activate the expression of HpINV2 and HpSuSy1, further contributing to sugar accumulation during fruit maturation (Wei et al., 2019). The SWEET family genes, particularly HuSWEET12a and HuSWEET13d, also play significant roles in sugar accumulation in pitaya fruits (Figure 2) (Jiang et al., 2023). 5.2 Environmental conditions and cultivation practices Environmental conditions such as temperature, light, and soil quality significantly influence the metabolism of sugars and organic acids in pitaya. Optimal temperature and light conditions are essential for the proper functioning of metabolic pathways that govern sugar and acid synthesis. Soil conditions, including nutrient availability and pH, also affect the metabolic processes. For example, the accumulation of betalains, which are associated with sugar and organic acid metabolism, is influenced by these environmental factors (Wu et al., 2019). Irrigation and fertilization practices are critical in maintaining the balance between sugars and organic acids in pitaya fruits. Adequate irrigation ensures the proper hydration of the plant, which is necessary for the efficient transport and metabolism of sugars and acids. Fertilization provides essential nutrients that support the metabolic pathways involved in sugar and acid synthesis (Diógenes et al., 2022; Oliveira et al., 2022). The balance between these practices can significantly impact the flavor and nutritional quality of the fruit.
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