Grafting wild rootstocks as a climate-resilient strategy to enhance productivity, quality and tolerance in eggplant under variable water stress induced by deficit irrigation

Abstract

Grafting scion of high-yielding cultivars on wild and tolerant rootstocks is emerging as a promising climate-resilient strategy for enhancing crop productivity, especially the vegetables cultivated in water-scarce regions. Its effectiveness was evaluated by grafting eggplant scion (Solanum melongena L., cv. Ajay: AJ) onto wild rootstocks (Solanum macrocarpon: SM, Solanum gilo: SG, and Solanum torvum: ST) and comparing these with self-grafted AJ/AJ and non-grafted AJ controls, under variable water stress intensities for two-years (2021–2023). Under full irrigation (100 % ET), fruit yield was 40.4 Mg ha⁻¹ , and shoot biomass was 1.28 Mg ha⁻¹ . These values decreased by 20–75 % and 6.2–64 %, respectively, as water deficits increased with irrigation at 75–25 % ET. Enhanced canopy vigour, root proliferation, water and nutrient uptake, and photosynthesis (Q_max) in grafted plants improved fruit yield by 12.7–24.5 % and water productivity by 6.1–9.9 kg m^–3. Fruit yield losses decreased by 12–44 %. Scions grafted onto SM and SG rootstocks showed higher tolerance, as indicated by quadratic water production functions and lower fruit yield response factors (K_AJ/SM and K_AJ/SG ≤ 1). Grafting also maintained fruit quality traits, including weight per fruit, their diameter, firmness, protein content, and total soluble solids. Additionally, the fruit dry matter, rehydration quality, and phenolic constituents improved, which increased their suitability for marketing, storage, and processing. Thus, grafting onto Solanum macrocarpon and Solanum gilo rootstocks, combined with mild to medium deficit irrigation (50–75 % ET), can be an effective strategy for optimizing water resource utilization and sustaining eggplant production and fruit quality in drought-prone regions.