Effect of Upright Shoot Removal on Fruit Size and Maturity of Four-year-old `Braeburn' Apple Trees

Abstract

The effect of upright shoot removal on the progress of maturity and fruit size around the normal picking time were evaluated for apple fruits cv. `Braeburn' at the Experimental Farm of the Comahue National Univ., Rio Negro, Argentina, during the 1996–97 growing season. The experiment was conducted on 4-year-old trees, spaced 4.0 × 2.3 m and trained to palmette leader. Average fruit load was 80 fruits per tree. Five trees per treatment were randomly selected; they were: 1) select cuts: water sprouts were eliminated entirely at 78 days after full bloom (DAFB) and additional removal of newly formed shoots arising from the scaffolds was performed at 120 DAFB; 2) control: trees received no cuts. From 158 to 184 DAFB, a sample of four fruits was taken from each tree at weekly intervals. Fruit size and internal quality were measured. Loss of leaf surface by shoot removal significantly decreased fruit mass by 4.74%, for all data combined (P < 0.05). There was no treament effect on maturity, although the rate of firmness decline was lower for fruit from treated trees. At 172 DAFB, pressure, starch index (iodine test) and soluble solids concentration values for control fruits were 80.55 N, 3.72 and 12.35%, respectively. In the treated trees, fruit mass was 201.03 g at final harvest. It was concluded that reduction in photoassimilates following severe upright shoot removal may be a key factor in the negative effect of this practice on final fruit size. These results suggest some goals of pruning and training for optimizing apple yield.