Influence of growth stage specific water stress on the yield, physico-chemical quality and functional characteristics of tomato grown in shallow basaltic soils

Various options of deficit irrigation (DI) were tested for accumulation of functional food compounds on tomato included; (i) continuous deficit irrigation i.e. applying irrigation water equally (0.6, 0.8 and 1.0 evapotranspiration (ET)), (ii) DI at vegetative, flowering and fruiting stages (0.6 ET for 30 days), (iii) DI at vegetative and flowering, vegetative and fruiting, flowering and fruiting stage (0.6ET for 30 days at each stage) and (iv) withholding of irrigation at vegetative, flowering and fruiting stage for 15 days.Fruit quality and functional food properties improved with DI. Color (a/b* ratio) and the concentrations of vitamin C increased by 82 and 70% with irrigation of 0.6 ET continuous DI compared to control. Withholding irrigation during fruit development induced color development (52%), vitamin C content (16%) and recorded better lycopene content (10.2 mg/100 g). The total phenolics and flavonoids ranged between 16 and 42 mg gallic acid equivalent/100 g and 4-10 mg catechin equivalent/100 g respectively with higher values recorded under DI at fruiting stage. Antioxidant activity (AOA) tested with different in vitro assays revealed the positivity of DI on improvement of bioactive compounds. Superoxide dismutase activity was significantly higher in DI treatments at fruiting stage compared to catalase activity. DI or withholding irrigation at fruiting stage could improve the quality of tomato due to redox oriented homeostasis of biologically active compounds and their biosynthesis.