Physiological and productive response of table grapes cv. Red Globe to pre- and post-harvest regulated deficit irrigation

Abstract

Physiological and productive responses of table grape cv. Red Globe to different regulated deficit irrigation schedules were studied as strategy for facing the increasing water scarcity which affects Chilean table grape producing areas. Treatments, in a factorial layout with two irrigation levels of 50% (T50) and 30% (T30) ETc x two periods corresponding to stage three of berry growth (S3) and postharvest (PH), were compared to a fully irrigated control treatment (T100). Measurements were performed on cv. Red Globe table grapes trained on an overhead trellis in a commercial orchard located in Ovalle, Chile. Gas exchange and stem water potential were measured throughout the season; berry diameter and weight along with overall cluster color and soluble sugar concentration (SS) were measured at harvest. Prior to harvest, T30S3 plants showed the lowest values of both physiological and agronomical traits and failed to meet commercial color requirements. For all traits, T50S3 had intermediate values, often non-significantly different from T100. The most responsive variable was SS with statistical differences between T100, T50S3 and T30S3: 18.24, 16.88 and 15.90 °Bx, respectively. During S3 SS was first positively correlated to stem water potential and then to carbon assimilation (last month before harvest). Post-harvest water deficit treatments did not affect physiology but reduced water saving as compared to T50S3 and T30S3. Although some quality traits were affected, during seasons with water shortage T50S3 appears as the best strategy for saving water while preserving commercial fruit quality.