Effect of regulated deficit irrigation on pomegranate fruit quality at harvest and during cold storage

Abstract

The effect of regulated deficit irrigation (RDI) strategies on fruit yield and quality at harvest and during cold storage at 5 °C of Wonderful pomegranates was studied. Three irrigation strategies were tested: control strategy (C) using farm irrigation with 100% of crop evaporation (ETc), and two RDI strategies where 25% of ETc was applied during flowering and fruit set (RDI 1) and during the final phase of fruit growth and ripening (RDI 2). The RDI 1 approach reduced the pomegranate yield. Conversely, the RDI 2 allowed a similar pomegranate yield to C treatment. Fruit morphological characteristics were not affected by RDI at harvest and during cold storage. Both RDI strategies resulted in fruits with higher aril percentages. Physicochemical parameters of fruits at harvest and during cold storage were not affected by irrigation strategies, except the total soluble solids content that was higher in fruits from RDI 2 than in those from C and RDI 1. During storage, a reduction of the fruit weight and size was observed, particularly in the first 15 days of storage. The total soluble solids content and titratable acidity decrease, while pH increases with storage. At harvest and during cold storage, the total phenolic content and antioxidant activity evaluated by ABTS+ assay did not differ among irrigation treatments, whereas using a FRAP assay fruits from RDI trended to have higher antioxidant activity than those from C treatment. Total phenolic content and ABTS+ values were lower at the final of storage time than on the first day. Present results showed that RDI strategies applied in a final phase of fruit growth and ripening could be a convenient irrigation strategy for commercial Wonderful orchards in the south of Portugal, allowing improve the fruit quality with a water saving of 14.6%.