Irrigation with saline water improves carotenoids content and antioxidant activity of tomato

The combined effect of increasing concentrations of NaCl in the irrigation water and fertilization with different nitrogen sources on the chemical composition of tomato (Lycopersicon esculentum Mill.) fruit was investigated. Increasing water salinity from 0.5 dS m(-1) (non-salinized control) to 15.7 dS m(-1) resulted in both reduced fruit size and fruit water content, whereas it caused an increase in soluble solids, carbohydrates, sodium and chloride concentrations. Titratable acidity increased upon irrigation with saline water, whereas the fruit redness significantly decreased. In addition, salinity reduced P, K+, Mg2+ and NO3- fruit concentrations. Total carotenoids and lycopene concentrations expressed on both fresh- and dry-weight basis gradually increased from the non-salinized control to the 4.4 dS m(-1) treatment (approximately 0.25% NaCl w/v) and they decreased at electrical conductivities of the irrigation water higher than 4.4 dS m(-1). Overall these data show that it is possible to improve carotenoid content and antioxidative activity of tomato, with an acceptable yield reduction, by irrigating with saline water containing NaCl up to 0.25% (w/v).