Effects of Regulated Deficit Irrigation on Tomato Quality and Key Aroma Compounds

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: 1) conventional irrigation at 24 L·m –2 per application, 2) irrigation treatment 1 at a 50% reduction of 12 L·m –2 per application), and 3) treatment 2 (T2) at a 25% reduction of 18 L·m –2 per application. The effects of RDI on tomato plant growth, yield, fruit quality, and volatile organic compounds (VOCs) were evaluated. Results showed that T2 reduced yield significantly (–26.55%), but enhanced fruit firmness (35.57% increase in shoulder hardness), soluble solids content (14.56%), vitamin C content (44.19%), and the sugar-to-acid ratio (2.25%). Volatile analysis revealed that T2 increased markedly the concentration of key aroma compounds, with odor activity values (OAVs) > 10. C 9 and C 10 volatiles comprised 55.56% of aroma-active compounds (OAV > 1) with T2, some of which may originate from the lipoxygenase (LOX) and hydroperoxide lyase (HPL) pathways, reflecting that RDI activates the LOX and HPL pathways to enrich flavor. The findings confirm that moderate RDI (25% reduction) balances yield and fruit quality effectively by improving texture, nutritional value, and aroma complexity, offering a promising strategy for water-efficient, quality-focused tomato production.