Effects of drip irrigation regime, rootstock, and cultivar on yield and bioactive composition of pear (Pyrus communis L.) under semi-arid conditions

Water scarcity is becoming an increasingly limiting factor for fruit production in Mediterranean semi-arid regions. However, the combined effects of irrigation regime, rootstock, and cultivar on the biochemical quality of pear fruit have not been sufficiently investigated. This study examines the combined effects of irrigation regime, rootstock, and cultivar on detailed phenolic and organic acid profiles, antioxidant activity, and yield across two seasons, providing practical insights for pear production under semi-arid conditions. In this study, the effects of four drip irrigation regimes — deficit (X/2, 50% ETc), control (X, 100% ETc), moderate excess (3X/2, 150% ETc), and excess (2X, 200% ETc) — on yield, physicochemical quality, sugar and organic acid composition, phenolic profile, and antioxidant activity were examined over two consecutive growing seasons (2022–2023) in ‘Carmen’ and ‘Etrusca’ pear cultivars grafted onto Fox 11 and BA-29 rootstocks under semi-arid conditions (Denizli, Türkiye). Rootstock, cultivar, and irrigation regime all significantly influenced yield and biochemical quality. Fox 11 outperformed BA-29 in bioactive compound content across all regimes, whereas BA-29 showed higher yield potential. ‘Carmen’ surpassed ‘Etrusca’ in titratable acidity (TA), vitamin C, antioxidant activity, and malic acid. The deficit regime (X/2) maximized quality — TSS (up to 17.40%), TA (0.39%), vitamin C (13.56 mg/100 g), chlorogenic acid (345.89 mg/100 g), malic acid (3496.16 mg/100 g), and DPPH inhibition (69.24%) — but reduced yield by 35.6% versus the control. Excess irrigation (2X) lowered yield by 11.5% and decreased chlorogenic acid, vitamin C, and antioxidant activity by more than 20%. Water-use efficiency declined with increasing water supply, from 4.96 kg/m 3 (X/2) to 3.86, 2.82, and 1.71 kg/m 3 under X, 3X/2, and 2X, respectively. The moderate-excess regime (3X/2) increased yield by 9.8% over the control while retaining high bioactive content, providing the best yield–quality balance. For phenolic compounds and antioxidant activity, PC1 explained 89.5% of the variance in ‘Etrusca’ and 89.0% in ‘Carmen’; corresponding PC1 values were 67.6% and 67.0% for organic acids, and 63.4% and 57.9% for overall fruit quality. Yield was consistently negatively correlated with quality, most strongly with SSC, TA, and antioxidant activity. The ‘Carmen’/Fox 11/3X/2 combination is recommended for quality-priority production systems, and the ‘Carmen’/BA-29/3X/2 combination for yield-priority systems.