Effect of Regulated Deficit Irrigation on Quality and Key Aroma-Active Compounds of Tomato (<em>Solanum lycopersicum L.</em>) Fruit

To investigate the effects of regulated deficit irrigation (RDI) on tomato fruit quality and flavor, a study was conducted using the tomato cultivar 'Gaotang No. 1' under three irrigation treatments: CK (conventional irrigation, 16 m&sup3;/mu per session), T1 (50% reduction, 8 m&sup3;/mu), and T2 (25% reduction, 12 m&sup3;/mu). The impact on plant growth, yield, fruit quality, and volatile organic compounds (VOCs) was evaluated. Results showed that the T2 treatment significantly reduced yield (&minus;26.55%) but enhanced fruit firmness (35.57% increase in shoulder hardness), soluble solids (14.56%), vitamin C content (44.19%), and the sugar-to-acid ratio (2.25%). Volatile analysis revealed that T2 markedly increased the concentration of key aroma compounds with odor activity values (OAV) &gt;10, including 2-pentyl furan (24.71%), (Z)-3,7-dimethyl-1,3,6-octadecatriene (128.49%) contributing to floral aroma, 2-ethyl-5-methylpyrazine (204.10%) associated with fruity aroma, and 4- isopropyltoluene (125.79%) contributing to citrus aroma. These compounds significantly shaped the overall aroma profile, resulting in a richer flavor. The findings confirm that moderate RDI (25% reduction) effectively balances yield and fruit quality by improving texture, nutritional value, and aroma complexity, offering a promising strategy for water-efficient, quality-focused tomato production.