Effects of exogenous gibberellic acid on chlorophyll metabolism of Sudachi (Citrus sudachi Hort.) after harvest

Sudachi (Citrus sudachi Hort.), cultivated in Japan, is a type of sour citrus fruit. Sudachi fruit is preferred by consumers for its rich flavor during the green period of the peel. As the Sudachi fruit ripens, the flavedo color changes from green to yellow and the fruit loses its flavor. In the present study, to inhibit the color development in the flavedo of Sudachi, the fruit were dipped in 500 μM of gibberellic acid (GA) solution for 1 h, and the effects on chlorophyll metabolism were investigated in Sudachi fruit. The results indicated that the GA treatment delayed the degreening, and inhibited the decrease in chlorophyll contents in the flavedo of Sudachi. With GA treatment, the expression levels of chlorophyll biosynthetic genes (CitGUN4, CitCHLH, CitPORA, CitCHL27, and CitGGDR) were upregulated and chlorophyll catabolic genes (CitNYC, CitPPH, CitSGR, and CitPAO) were downregulated, which led to preserving a high levels of chlorophyll contents. The results of this study elucidated the molecular mechanism of the GA effect on citrus fruit, which suggested that GA effectively inhibited the yellowing of citrus flavedo.