Effect of Sunred metabolic promoter and deficit irrigation on fruit quality of 'Valencia' oranges

Abstract

This study evaluated the effect of deficit irrigation and Sunred foliar metabolic promoter on fruit quality of adult 'Valencia' orange trees. Three irrigation strategies were imposed in spring 2011: Irrigation with volumes corresponding to 100% of crop evapotranspiration applied to entire root-zone (CI), partial root-zone drying (PRD) with 50% of CI water applied to one alternated side of the root-zone, and continuous deficit irrigation (DI) with 50% of CI water applied to both sides of the root-zone. Four trees in each irrigation treatment were sprayed 30 and 20 days before harvest with Sunred metabolic promoter containing phenylalanine, methionine, mono-saccharides and oxylipins from plant extracts. Climate and soil parameters were monitored continuously in the field; crop load and fruit quality were measured at harvest in May 2012. Fruit peel color was determined by digital image analysis. After adjusting for crop load, fruits of PRD and DI trees tended to be smaller but sweeter than those of CI trees. Regardless of irrigation, Sunred increased mainly TSS:acid ratio by lowering acidity. Average fruit peel color was similar in sprayed and control trees, but a smaller coefficient of variation indicated greater uniformity in the former. These preliminary results suggest that Sunred foliar sprays in pre-harvest may improve internal fruit quality of 'Valencia' oranges by advancing and uniforming fruit maturity and regardless of irrigation strategy.