Blue light inhibited postharvest softening of kiwifruit by modulating the reactive oxygen species scavenging system

The content of reactive oxygen species (ROS) was closely associated with the postharvest quality and softening speed in kiwifruit. Here, the effects of blue light on postharvest softening and ROS metabolism of kiwifruit were studied. The results demonstrated that blue light with a wavelength of 420 nm resulted in a delay in the reduction of fruit firmness and accumulation of total soluble solids by augmenting 1,1- diphenyl-2-picrylhydrazyl scavenging rate and reducing the levels of malondialdehyde, hydrogen peroxide, and superoxide anion. Blue light concurrently enhanced the activity of superoxide dismutase (SOD) and catalase (CAT), as well as upregulated the expression levels of associated genes. Additionally, kiwifruit treated with blue light exhibited significantly elevated levels of ascorbic acid (AsA) and glutathione (GSH), along with reduced levels of oxidized AsA (DHA) and oxidized GSH (GSSG), in comparison to the control group. Also, blue light enhanced the activity of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), mono-DHAR (MDHAR), and GSH reductase (GR) enzymes in the AsA-GSH cycle, while it decreased the activity of AsA oxidase (AO) enzymes. Correspondingly, blue light induced the expression of genes related to AsA biosynthesis and the AsA-GSH cycle, while inhibiting the expression of the AcAO genes. Altogether, the findings of our study indicate that blue light effectively enhanced the ROS scavenging capacity of kiwifruit and preserved a high level of AsA content, then retarded its postharvest ripening and softening.