35 The Concept of Centrifugal Training in Apple Aimed at Optimizing the Relationship between Growth and Fruiting P.-É. Lauri and M. Willaume* Équipe Architecture et Fonctionnement des Espèces Fruitières (AFEF), UMR 1098 INRA, 2, Place Pierre Viala 34060 Montpellier Cedex 1 France Tel: +33 4 99 61 24 14 Fax: +33 4 99 61 26 16 E-mail: lauri@ensam.inra.fr * student G. Larrive and J.-M. Lespinasse Centre expérimental CIREA 24130 Prigonrieux France Tel: +33 5 53 73 07 32 Fax: +33 5 53 61 66 45 E-mail: cirea-franchemont@wanadoo.fr Keywords: apple, extinction, regularity of bearing, fruit size, centrifugal training concept, LITE planting system Abstract Manipulation of vegetative growth-fruiting relationships to ensure high quality fruits and regular cropping is the objective of all apple production systems. For several decades, the use of intensive orchards has been proposed to improve yield, notably early cropping, and profitability. The example of developments towards the Solaxe system in France shows that training concepts have evolved from a two-step vision to a more integrated vision of fruit tree management. In the former case, the aim is to establish a solid framework leading to non-bearing years and then, maintenance pruning is done to ensure cropping. In the latter case, tree structure is de-emphasized and greater importance is given to the control of fruiting as part of training procedures. Based on deeper knowledge of tree biology and genetic varia- tion, the main objective is to orient overall tree vigor towards fruiting laterals for improving fruit quality and return bloom, rather than to influence vegetative vigor by means of dwarfing rootstocks or pruning. On the bearing tree, crop regulation is achieved by artificial extinction or, in short form, extinction, i.e. the complete and definitive removal of fruiting laterals (spurs and brindles), with chemical- and hand- thinning of remaining fruit buds if necessary. We recommend extinction more specifically in the center of the tree and on the underside of branches, first, to remove potentially poor-quality fruits and second, to improve light distribution within the tree. This training procedure favoring the peripheral layer of the tree canopy is known as centrifugal training (conduite centrifuge) and is now included in the LITE planting system. For 3 years, experiments have been carried out to assess the effects of these training concepts on fruit quality attributes and regular cropping. Results showed that centrifugal training increased fruit size and uniformity. Return bloom was also significantly enhanced with a tendency to increase lateral fruiting autonomy (bourse over bourse phenomenon). INTRODUCTION After several decades of extensive research on new production systems, specifically on apple, it has been determined that there is no single best planting system for every grower (Hoying and Robinson, 2000). The orchard system in itself does not resolve major problems such as regularity of bearing and fruit quality (Lauri and Lespinasse, 1999). Regardless of the planting system, the various components of the “Orchard System Puzzle” (Barritt, 1992) initially designed for a specific system are always adapted to integrate not only new economic constraints but also improvements in tree growth and fruiting knowledge (e.g. Vertical Axis to Solaxe system in France; Lauri and Lespinasse, 2000). Proc. XXVI IHC – Deciduous Fruit and Nut Trees Ed. A.D. Webster Acta Hort. 636, ISHS 2004 Publication supported by Can. Int. Dev. Agency (CIDA)