Blue LED light induces regreening in the flavedo of Valencia orange in vitro

In the present study, the effects of blue LED light on the regreening of citrus fruit were investigated in an in vitro system of Valencia orange flavedos. The results showed that blue LED light irradiation induced regreening in the flavedos. After four-week culture in vitro, the flavedos exhibited obviously green color in the blue LED light treatment, while the flavedos in the control were still in orange color. During the regreening process, the blue LED light treatment induced chlorophyll accumulation, and substantially altered the carotenoid composition in the flavedos. Compared with the control, the content of 9-cis-violaxanthin was decreased, while the contents of lutein, β-carotene, and all-trans-violaxanthin were increased by blue LED light. In addition, gene expression results showed that the up-regulation of CitLCYe and down-regulation of CitLCYb2 by blue LED light led to a shift from β,β-branch to β,ε-branch of the carotenoid biosynthetic pathway.