Secondary flowering is the phenomenon in which a tree blooms twice or more times a year. Along with the development of blueberry (Vaccinium corymbosum L.) fruits in spring, a large number of secondary flowers on the strong upright spring shoots were noticed in blueberries planted in the greenhouse. To reveal the cause and possible regulatory mechanism of the phenomenon, we clarified the phenological characteristics of flower bud differentiation and development on the spring shoots by combining phenological phenotype with anatomical observation. Furthermore, the changes in carbohydrates, trehalose-6-phosphate (Tre6P), and the relationship among the key enzyme regulatory genes for Tre6P metabolism and the key regulatory genes for flower formation during the differentiation process of apical buds and axillary buds were investigated. The results showed that the process of flower bud differentiation and flowering of apical and axillary buds was consistent, accompanied by a large amount of carbohydrate consumption. This process was positively correlated with the expression trends of VcTPS1/2, VcSnRK1, VcFT, VcLFY2, VcSPL43, VcAP1, and VcDAM in general, and negatively correlated with that of VcTPP. In addition, there is a certain difference in the differentiation progress of flower buds between the apical and axillary buds. Compared with axillary buds, apical buds had higher contents of sucrose, fructose, glucose, Tre6P, and higher expression levels of VcTPS2, VcFT, VcSPL43, and VcAP1. Moreover, VcTPS1 and VcTPS2 were more closely related to the physiological substances (sucrose and Tre6P) in axillary bud and apical bud differentiation, respectively. It was suggested that sucrose and trehalose-6-phosphate play a crucial role in promoting flower bud differentiation in strong upright spring shoots, and VcTPS1 and VcTPS2 might play a central role in these activities. Our study provided substantial sight for further study on the mechanism of multiple flowering of blueberries and laid a foundation for the regulation and utilization of the phenomenon of multiple flowering in a growing season of perennial woody plants.

The efficient utilization of light energy is a powerful guarantee to improve the production efficiency of agricultural and forestry facilities. This study investigated the effects of early-morning supplemental lighting on the yield and fruit quality of greenhouse-grown blueberry and examined the physiological and transcriptional responses associated with anthocyanin accumulation. The findings indicate that supplemental lighting significantly promoted fruit development, accelerated maturation, and increased fruit size, weight, sugar, vitamin C content and the antioxidant capacity of the fruits, especially the anthocyanin content. Transcriptomic analysis revealed that, during fruit ripening, the differentially up-regulated genes activated by supplemental lighting primarily involved transmembrane transport functions, membrane components, and redox enzyme activity. Conversely, the down-regulated genes were mainly involved in organic acid metabolism, photosynthesis and photosystem functions. Pathways associated with the up-regulated genes were largely connected to anthocyanin biosynthesis and galactose metabolism. Furthermore, the anthocyanin biosynthesis showed affiliations with several distinct genes (such as 4CL and UFGT) that were differentially up-regulated, along with the MYB transcription factor. Notably, in blueberries exposed to supplemental lighting, VcMYBPA1 showed a strong positive correlation with UFGT. Further investigations demonstrated that VcMYBPA1 was mainly localized in the nucleus, and its overexpression significantly increased the expression levels of AtDFR, AtANS, and AtUFGT in Arabidopsis. This study highlights the crucial role of supplemental lighting in enhancing blueberry yield and quality and provides an effective way to further improve the utilization of light-assisted agricultural technologies.