Effects of chitosan oligosaccharides postharvest treatment on the quality and ripening related gene expression of cultivated strawberry fruits

BACKGROUND: Chitosan oligosaccharide (COS), degraded from chitosan, has been proved as an effective plant immunity elicitor, eco-friendly, easily soluble in water and influenced several secondary metabolites content to improve fruit qualities. OBJECTIVE: The effects of chitosan oligosaccharides (COS) on the quality and ripening related gene expression of strawberry (Fragariaxananassa cv. qingxiang) during storage were investigated in this study. METHODS: COS was dissolved in distilled water at a concentration of 50 and 100 mg.L-1. Then the fruits were dipped in COS solution and the control group was dipped in equal amount of distilled water for 1 minute. After that the fruits were air-dried and stored at 20 +/- 0.5 degrees C with 80 +/- 2% relative humidity. RESULTS: COS treated fruits significantly delayed the loss of hardness, total sugar and ascorbate content. In addition, COS treatments had positive effect on maintaining higher concentration of total phenol, anthocyanin content and antioxidant activity. Moreover, COS treatments also had positive effect on inhibition of relative gene expression of cell wall polysaccharides degradation pathways, including pectate lyase (FaPL), pectin esterase (FaPE) and endoglucanase (FaEG) and ethylene biosynthesis (FaACS and FaACO) pathway. These findings suggest that the use of COS 100 mg.L-1 postharvest treatment is useful for maintaining quality and storage life of strawberry fruits. CONCLUSION: COS postharvest treatment appeared to have a beneficial impact on the quality retention, maintained lower activities of cell wall degradation and the ethylene biosynthesis pathway by suppressing the gene expression during storage of strawberry.