Comparison of quality and flavor between on-tree storage and cold storage of Satsuma 'Youliang'.

This study investigates the effects of on-tree storage (OTS) on the quality and flavor of Satsuma 'Youliang' compared with cold storage (COS). Fruit quality was assessed based on sugar-acid ratio and juice flavor profiles. Comparative analysis revealed a progressive decline in soluble sugar content under COS, while OTS effectively preserved sugars, resulting in a higher sugar-acid ratio than COS-treated fruits. During storage, OTS fruits maintained significantly higher levels of sucrose, fructose, and malic acid than COS fruits. Additionally, OTS fruits exhibited a greater variety and higher concentrations of volatile organic compounds (VOCs), contributing to enhanced flavor. Transcriptome analysis indicated that OTS reduced sugar loss by upregulating soluble sugar metabolism-related genes (SUS, SPS). Furthermore, OTS upregulated tricarboxylic acid cycle-related genes (SSADH, NAD-MDH), accelerating malic acid synthesis. Additionally, OTS activated the expression of ACAT, GPS, and GPPS, promoting the production of terpenoid precursors GPP and GGPP. These findings suggest that OTS improves fruit acceptability and is more effective than COS for maintaining fruit quality.