Pruning effects on vegetative growth and fruit quality of 'Bing'/'Gisela®5' and 'Bing'/'Gisela®6' sweet cherry trees (Prunus avium)
Annual pruning is one of the most efficient ways to regulate crop load and renew fruiting wood in highly productive sweet cherry (Prunus avium L.) combinations. Although Chilean growers did not previously prune cherry trees of more vigorous combinations, in recent years, the adoption of more dwarfing rootstocks and self-fertile cultivars has led to the inclusion of annual pruning as a practice in modern orchards. At first, this alteration in orchard management practices was not considered by growers, and thus, many of the initially established cherry orchards were not pruned as intensively as they should have been. As a consequence, many trees showed a reduction in fruit quality after 4 or 5 years of being planted, as they became overcropped and, consequently, registered reductions in their vegetative growth. There are only a few studies related to the effect of corrective pruning on dwarfing combinations that display an imbalance between reproductive and vegetative growth due to a reduction in the leaf area to fruit ratio of the tree. For this reason, the objective of this research was to study the effect of pruning in an orchard consisting of the dwarfing combinations 'Bing'/'Gisela®5' ('Bing'/'GI®5') and 'Bing'/'Gisela®6' ('Bing'/'GI®6'), which shown a reduction in vigor, fruit quality and yield. Trees of both combinations were treated with a medium intensity pruning in late winter (early September). Several vegetative (shoot length, leaf area of spurs and shoots, trunk cross sectional area) and reproductive (total yield per tree, fruit growth and quality) parameters were evaluated after pruning. One of the most important effects of pruning for both combinations was an increase in the total current season shoot (CSS) growth, which was 112.5 and 125.6% for 'Bing'/'GI®5' and 'Bing'/'GI®6', respectively. Additionally, the average shoot length increased by 820.0 and 325.4% for 'Bing'/'GI®5' and 'Bing'/'GI®6', respectively. Furthermore, CSSs developed a higher leaf number in the pruned trees. There was no change in leaf number for reproductive spurs, but these had bigger leaves in the pruned trees, demonstrating increased total leaf area per spur. Additionally, pruning allowed crop load regulation and increased fruit size by 8.5 and 6.1% for 'Bing'/'GI®5' and 'Bing'/'GI®6', respectively. However, fruits from pruned trees showed a higher susceptibility to mechanical damage compared with unpruned trees of both combinations.