An architectural-based tree training and pruning - identification of key features in the apple

High density planting systems, with their fast entrance into production and a high regular production level of high quality fruit face many challenges. In this context the development of minimal pruning strategies is crucial to reach and maintain the economic profitability along the orchard life span. A better knowledge of the cultivar-related growth, branching and fruiting habits, referred to as tree architecture, is of major importance in understanding the cultivar-dependent reactions to manipulation. This is especially true in the apple which is the first worldwide temperate fruit species with a great range of architecturally contrasted cultivars. Based on works developed at INRA during the 50s, Lespinasse’s typology established four main tree types. Type I trees have a strong disjunction between upright scaffolds and lateral fruiting spurs whereas type IV trees have a profuse tip-bearing habit leading to a more globular crown. This typology has not only a descriptive interest, it is also related to fruiting behaviour: type I cultivars have an alternate bearing pattern whereas type IV cultivars have a more regular bearing pattern. Recent work carried out on cultivars and hybrids proposed other criteria to better characterize intrinsic cultivar characteristics. Three features are observed at the tree or branch level: aptitude to reiterate, i.e. development of vigorous shoots within the tree structure; effect of branch bending on fruiting; fruiting on 1-year-old wood. Three features are observed at spur level: bourse-over-bourse, natural spur extinction, bourse volume. Based on this knowledge, practical training and pruning schemes suited to the architectural characteristics of each cultivar or group of cultivars are now proposed in the context of the improvement of Centrifugal Training system which is under development in France and some other countries. Whether these rules are valid in various environmental conditions (climate, soil) remains to be validated.