Regulated deficit irrigation and partial root-zone drying irrigation impact bioactive compounds and antioxidant activity in two select tomato cultivars

• Effects of deficit irrigation treatments on two tomato cultivars were investigated.
• Antioxidant contents and activity of both cultivars were affected by irrigation.
• Influence of irrigation on fruit color and antioxidant contents was cultivar-dependent.
• Vitamin C and phenolic compounds were the main contributors to antioxidant activity.

Since drought stress and low WUE both influence fruit quality, the corresponding relationship between water supply and synthesis of bioactive compounds requires investigation. In this study, the effect of regulated deficit irrigation (RDI) and partial root-zone drying irrigation (PRD) techniques on the lycopene, β-carotene, vitamin C, and total phenolic (TPC) contents in two tomato cultivars (Matina and Cochoro) were investigated. Antioxidant activity was evaluated using DPPH, FRAP and TEAC assays. Deficit irrigation treatments affected plant growth as well as yield, quality, and antioxidant contents of fruits. However, the effects on content of antioxidants were cultivar-dependent. Vitamin C and lycopene contents in Matina significantly increased, while values decreased in Cochoro under both PRD and RDI. TPC and β-carotene contents increased in both cultivars, but a greater increment of TPC (+88.1%fw) was recorded in Cochoro. Overall, vitamin C and TPC were found to be the main contributors to the total antioxidant activity in fruits. The study suggested that choice of appropriate cultivars subjected to deficit irrigation strategies can significantly influence the bioactive compounds, particularly vitamin C, lycopene, and TPC.