SEASONAL CHANGES ON THE QUALITY OF `PERLETTE' TABLE GRAPES IN RESPONSE TO WATER-DEFICIT STRESS AT PARTICULAR STAGES OF DEVELOPMENT.

Abstract

The nature of yield and quality losses for many fruits is dependent upon the time when water deficits occur in relation to fruit development. We evaluated the water stress effect applied at different stages of development on the quality and harvest date of 'Perlette' table grapes. Nine treatments based on amount of water applied by the grower (100%, 80% and 60%) and their combinations at two growth stages, fruit set to vérasion (F-V) and vérasion to harvest (V-H) were compared. Weekly samples of fruit were analyzed for diameter, weight, volume, soluble solids, tritatable acidity, pH, and pectin content. Harvest percentage at each date was used as precocity index. Significant differences were found on diameter and weight among treatments at various stages of development. The earliest and highest harvest percentage was for (F-V 80% and V-H 100%) treatment. High °Brix were obtained when the water volume was reduced after vérasion, but quality was poor. Chelator soluble pectins represented > 90% of total soluble pectins and was higher on the treatment (F-V 60% and V-H 60%) at harvest.