Effect of summer pruning on some fruit quality traits in Hayward kiwifruit

Introduction. The aim of our study was to analyze the effect of various levels of light availability in the fruit microenvironment (induced by summer pruning) on some fruit quality traits. Materials and methods. Two levels of summer pruning were set: removal of either 30% or 60% of the canopy leaf area. These treatments were compared with the control (unpruned vines). Two canopy layers (upper and lower) were identified in each treatment and in the control vines. At harvest, yield per cane and per shoot was recorded in the two canopy layers; fruit fresh weight, flesh firmness, total soluble solid content and total titratable acidity were measured. Fruit Total Antioxidant Capacity (TAC) and Total Polyphenols (TPH) were determined at kiwifruit harvest and post-harvest (60 days after storage at 1 degrees C) in relation to their position within the canopy (layer) and to the pruning treatment applied. Results. Removing 60% of the canopy leaf area induced higher titratable acidity and flesh firmness of kiwifruits at harvest; it reduced fruit weight and crop yield, but increased TAC and TPH compared with kiwifruits of control. Removing 30% leaf area did not reduce mean fruit weight and crop yield; it increased TAC and TPH at harvest by 20%. Post-harvest TAC and TPH evolution did not differ among treatments. Discussion and conclusion. Pergola-trained kiwifruit vines showed good performances in terms of crop yield and fruit quality when summer pruning reduced the Leaf Area Index (LAI) to 3. More intense pruning resulted in a significant increase in fruit TAC, but reduced fruit weight and crop yield, and delayed softening of pulp.