Fruit Quality of Tomato Plants Grown under Deficit Irrigation and Treated with Nano-Oxides, Mineral Salts, and Bioinoculants

Abstract Tomato (Solanum lycopersicum L.) fruit quality may be affected by deficit irrigation and by Fe, Zn, and microbial inputs. This study evaluated fruit-quality attributes at harvest in HM 2798 tomato under full and deficit irrigation. The experiment was conducted in a 6 × 2 factorial arrangement in a randomized complete block design with four blocks, comprising six treatments and two irrigation regimes, for a total of 48 experimental units. The treatments consisted of a control, ZnO and Fe2O3 nano-oxides, ZnSO4·7H2O and FeSO4·7H2O conventional salts, and a combined commercial bioinoculant treatment (Azokop + No-Nema) applied to the root zone, evaluated under full irrigation (100% crop evapotranspiration, ETc) and deficit irrigation (50% ETc). The Fe and Zn sources were sprayed on the foliage at nonequivalent elemental doses, with the conventional salts supplying approximately five times more Fe or Zn than the nano-oxides. Fruits were harvested once at the USDA Red stage (>90% red surface), and physicochemical attributes, soluble sugars, ascorbic acid, pigments, flavonoids, anthocyanins, and phenolic compounds were evaluated. Under 50% ETc, FeSO4·7H2O resulted in the highest total soluble, reducing, and nonreducing sugar contents, reaching 7.04, 1.23, and 5.81 g 100 g–1 FW, respectively, corresponding to increases of 64.4, 163.2, and 52.3% relative to the control. NPZnO resulted in the highest flavonoid content under 100% ETc (2.47 mg 100 g–1 FW; +27.7% relative to the control). The combined commercial bioinoculant treatment resulted in carotenoid contents of 13.09 and 12.28 mg 100 g–1 FW under 100% and 50% ETc, respectively, with no significant difference between irrigation regimes. ZnSO4·7H2O resulted in the highest phenolic compound content under 100% ETc (32.50 mg GAE 100 g–1 FW; +70.0% relative to the control). Overall, the responses depended on both treatment and irrigation regime, demonstrating specific changes in tomato fruit composition at harvest rather than a uniform mitigation effect of nano-oxides, conventional salts, or bioinoculants. Because dose, formulation, and, for the bioinoculants, application route differed among treatments, these results characterize the specific treatment programs tested rather than the intrinsic efficiency of nano or conventional formulations.