Summer Pruning of ‘Gala’ Apple: The Relationships between Pruning Time, Radiation Penetration, and Fruit Quality

Trees of apple cv. Gala ( Malus domestica Borkh.), which had previously been dormant pruned, were pruned in mid-December (early summer pruned—73 days after full bloom), mid-January (late summer pruned—108 days after full bloom), or were only dormant pruned (control). On 2 harvest dates (late February and early March) fruit from 4 different regions of the tree canopy were assessed for red blush, background color, soluble solids concentration, and fresh weight. Penetration of photosynthetic photon flux density (PPFD) to each region was measured at the summer pruning times and at the First harvest. Summer pruning increased the percentage of red blush—but not background color—for both pruning dates, decreased fresh weight of fruit from the early pruned trees, and decreased the soluble solids concentration of fruit from the late-pruned trees. The percentage of red blush and fruit fresh weight both showed a highly positive correlation with PPFD penetration, but for fruit fresh weight, the correlation also was dependent on the pruning treatment. The concentration of soluble solids also was related to PPFD penetration although, in comparison with fresh weight, the differences were reduced. Background color was relatively independent of tree position or pruning treatment.