Abstract:Previous research found that post-harvest blue light irradiation can enhance the coloration of peach skin.Based on this,the present study investigated the effect of different blue light photoperiods on anthocyanin metabolism in peach skin.Zhongtao No.9 peaches were placed under conditions of （22±1） ℃ and subjected to different blue light cycles （6,12,18 h/d and 24 h/d）,with dark treatment as the control group.Phenotypic observations,color difference measurements,and detection of anthocyanin content and expression levels of related genes were conducted.The results showed that with the extension of light exposure time,peach skin color,a* value,and color index of red grape value were significantly improved.Among the treatments,the 18 h/d and 24 h/d groups had the highest anthocyanin content,reaching 149.13 mg/kg and 150.95 mg/kg on the 8th day,respectively.Measurements of the expression levels of anthocyanin biosynthesis-related genes indicated that the 18 h/d treatment group could continuously enhance the expression of these genes.In contrast,the 24 h/d treatment group showed a significant increase in gene expression only in the early and middle stages of storage,followed by a decline in the later stage.Additionally,the 18 h/d treatment delayed the decrease in fruit firmness during storage.In conclusion,18 h/d of blue light was the optimal photoperiod for post-harvest blue light treatment of peach fruits.