IMPROVING QUALITY OF "THOMPSON SEEDLESS" GRAPES BY MEANS OF CANOPY MANAGEMENT

This research was carried out for three successive seasons: (2005, 2006 and 2007) on 10-year old Thompson Seedless grapevines supported by telephone system in a private vineyard located at Namol (Kalubia Governorate).Bud load was 10 canes × 14 buds per vine.The vines were characterized by having crowded vegetative growth, considerably, low yield and inferior quality of grapes.During January 2005 weight of one year old wood was measured as an indicator for vine vigor.Sixty vines were chosen for this study, twelve vines (4 vines replicated 3 times).The treatments included bud load of (6 canes × 12 buds /vine) with summer pruning and without summer pruning, (8 canes × 12 buds /vine) with summer pruning or without and the control (10 canes × 14 buds /vine) (vineyard pruning treatments) without summer pruning.The same vines were used at the three seasons of the study.Canopy measurements were used to determine the vegetative density by inserting the point quadrant into the vegetative growth.Results of 2006 and 2007 seasons showed a higher percentage of gaps, higher chlorophyll content, greater leaf area and higher light intensity at the treatments having a low number of canes accompanied with summer pruning (disbudding, pinching and defoliation).Percentage of bud burst, percentage of fruitful buds and fertility coefficient were increased at the treatments with 6 canes × 12 buds, 8 canes × 12 buds and the control (10 canes × 14 buds /vine).Total yield/vine, bunch weight and total soluble solids % were increased at the treatment of 6 canes × 12 buds with summer pruning in comparison with the other treatments and the control.Pruning weight, and acidity of berry juice were found to decrease in these treatments.This could be due to the positive effect of canopy management on improving microclimate of the vines and decreasing number of crowded shoots as to permit aeration and light to enter in to the center of the vines.