Synergistic potential of deficit irrigation and grafted eggplant on wild rootstocks for enhanced growth, yield, and water productivity

As climate change intensifies water scarcity, sustainable strategies are essential for vegetable production under water-limited conditions. This study evaluates the potential of grafted eggplant onto wild rootstocks under deficit irrigation (DI) to enhance growth, yield, and water productivity (WP). A two-year field experiment in semi-arid regions of India investigated the effects of three DI levels (100, 80, and 60% ETc) in the main plot and five graft combinations (SUR/GIL, SUR/IND, SUR/MAC, SUR/SIS, and SUR/TOR), along with a non-grafted variety Suraj in the subplot, with three replications. The data were analysed using individual and pooled analysis of variance based on a split-plot design. The results showed that fruit yield declined with reduced irrigation across all graft combinations, including the non-grafted control. However, graft combinations with drought-tolerant wild rootstocks, particularly SUR/SIS and SUR/TOR, consistently outperformed non-grafted Suraj under optimal (100% ETc) and deficit irrigation (60% ETc). Under 60% ETc, SUR/SIS recorded the highest yield, with only a 14% reduction compared to 100% ETc, followed by SUR/TOR with a 19% reduction, while non-grafted Suraj showed the highest reduction of up to 25%. WP was highest at 60% ETc, with SUR/SIS achieving 9.47 kg m⁻³ (41% higher) and SUR/TOR reaching 8.22 kg m⁻³ (22% higher) than non-grafted Suraj (6.72 kg m⁻³). The enhanced yield and WP under DI in grafted plants were attributed to superior growth, improved soil–plant water balance, sustained PSII efficiency, and enhanced antioxidative defence mechanisms. Grafting also enhanced fruit quality traits such as length, diameter, total soluble solids, and firmness. Therefore, integrating DI with grafting onto S. sisymbriifolium and S. torvum rootstocks offers a sustainable strategy to enhance yield and WP of eggplant in semi-arid regions. This strategy can be adapted to other fruiting vegetable crops in semi-arid regions to broaden its applicability under changing climatic conditions.