Chitosan oligosaccharide treatment improves quality attributes of tomato fruit stored under room temperature

Effect of chitosan oligosaccharide (COS), a natural product of low-cost and non-toxic with high biological activities, on quality attributes of tomato during post-harvest storage was investigated. Mature green tomato fruit were treated with 0.5 g L−1 COS and stored under room temperature. The results showed that COS was effective in improving fruit quality as revealed by redder color skin, higher content of nutrients such as carotenoids (lycopene and β-carotene) and vitamin C, and increased emissionb of flavor-associated volatiles (1-penten-3-one, heptanal, (E)-2-heptenal, 2-phenylacetaldehyde, 2-phenylethanol, 2-isobutylthiazole and β-ionone). The increased content of carotenoids upon COS treatment was correlated with the elevated expression levels of carotenogenic genes such as SlDXS, SlGGPS, SlPSY1, SlPDS, SlZDS, and SlLCY-B2. Moreover, COS-treated fruit exhibited accelerated occurrence of climacteric ethylene peak, enhanced ethylene production, and elevated expression of genes involved in ethylene biosynthesis (SlACS2, SlACS4, and SlACO1), perception (SlETR3), and response (E4 and E8), implying that COS might regulate fruit ripening and quality by enhancing ethylene biosynthesis and signaling. These findings help to extend our understanding of the function of COS in fruit ripening and provide a new strategy to improve tomato fruit quality during room temperature storage.