Bioscience Evidence 2026, Vol.16, No.4, 291-303 http://bioscipublisher.com/index.php/be 294 3.2 Light conditions Light is not only the energy source for blueberry photosynthesis but also an important environmental signal regulating the synthesis of anthocyanins and other bioactive compounds. Light intensity, spectral composition, and duration can influence related metabolic pathways, thereby affecting the accumulation of anthocyanins, phenolics, and vitamin C in blueberry fruit. Wei et al. (2023) investigated the effects of different LED light qualities on blueberry fruit and found that blue light significantly promoted the expression of anthocyanin biosynthesis-related genes and increased anthocyanin content (Figure 1). Yellow light, however, was more effective in enhancing ascorbic acid (vitamin C), glutathione, and total phenolic contents. In addition, blue and white light treatments promoted fruit enlargement and increased single fruit weight, suggesting that different light qualities regulate blueberry fruit development and nutritional quality through different mechanisms. Besides visible light, ultraviolet-B (UV-B) radiation is also an important environmental factor promoting anthocyanin accumulation. Recent studies have shown that UV-B acts as a developmental signal and activates anthocyanin biosynthesis through the UVR8-COP1-HY5-MYB regulatory pathway. Song et al. (2023) identified several MYB transcription factors involved in UV-B-induced anthocyanin accumulation in blueberry, while Li et al. (2021) reported that long-term preharvest UV-B exposure not only promoted fruit ripening and sugar accumulation but also regulated anthocyanin metabolism at different developmental stages. Therefore, shading nets, greenhouse films, or excessively dense canopies in modern production systems may reduce UV-B penetration or canopy light availability, potentially limiting anthocyanin accumulation and nutritional quality development. Figure 1 Possible mechanism of regulating fruit quality and anthocyanin content in blueberry via different light wavelengths. The green up-arrow indicates a significant increase, and the black down-arrow indicates a significant decrease. FAI, fruit appearance indexes; SOD, superoxide dismutase; POD, peroxidase; SS, soluble solids; TA, total acid; ABG, anthocyanin biosynthesis genes; AsA, ascorbic acid; GSH, glutathione; TP, total phenol (Adopted from Wei et al., 2023) 3.3 Temperature and climate conditions Temperature is a major climatic factor affecting blueberry fruit quality formation. It regulates bioactive compound accumulation through its effects on sugar accumulation, organic acid metabolism, enzyme activity, and plant stress responses. Prolonged high temperatures during summer can accelerate fruit respiration, increase carbon consumption, and reduce anthocyanin accumulation and fruit coloration. In contrast, environments with moderate daytime temperatures and cooler nights generally favor sugar accumulation, acid retention, and anthocyanin biosynthesis. Temperature and light are among the most important environmental factors controlling anthocyanin formation, and they can interact with plant hormone pathways to influence fruit quality. Field observations from different production regions further demonstrate the importance of climate conditions. Blueberries grown at higher altitudes generally show higher soluble solids content, total flavonoids, total phenolics, proanthocyanidins, and anthocyanins, together with higher sweetness scores compared with fruit produced at lower altitudes. Altitude is positively associated with flavonoid content, total phenolics, proanthocyanidins, anthocyanins, and fruit sweetness. These results suggest that low temperatures, larger day–night temperature differences, and unique light conditions associated with high-altitude environments jointly promote bioactive compound accumulation, making climate an important determinant of final blueberry fruit quality.
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