Abstract:

The effects of postharvest riboflavin dipping at different concentrations on lesion development of muskmelon
fruits artificially wounded and inoculated with Trichothecium roseum and Alternaria alternata were examined. The
metabolisms of phenylpropanoid pathway and the effects of riboflavin at different concentrations on mycelia growth and
spore germination of T. roseum and A. alternata were also studied. The results indicated that riboflavin at 1.0 mmol/L
effectively decreased the lesion diameter of muskmelon fruits inoculated with T. roseum and A. alternata. In vitro test also
indicated that riboflavin at 1.0 mmol/L effectively inhibited mycelia growth and spore germination of both pathogens. It was
also shown that postharvest riboflavin treatment significantly enhanced the activities of peroxidase (POD) and phenylalanine
ammonia lyase (PAL), and increased the contents of total phenolic compounds, flavonoids and lignin in muskmelon fruits.
These results suggest that postharvest riboflavin treatment strengthens the cell wall through activating the phenylpropanoid
pathway and enhancing the activities of defense-related enzymes and the accumulation of antifungal compounds to control
postharvest diseases in fruits.

Key words: muskmelon, riboflavin, phenylpropanoid pathway, postharvest diseases