Light interception characteristics estimated from three-dimensional virtual plants for two apple cultivas and influenced by combinations of rootstocks and tree architecture in loess plateau of China

Communication orale + résumé Communication orale + résuméCommunication orale + résuméThe agronomic efficiency of dwarf interstock use is presently under debate in China where almost 90% of apple orchards use vigorous rootstock, even in high density orchards. This study aimed at comparing two apple cultivars ('Fuji' and 'Gala') performance when grafted on a vigorous rootstock but associated either with a dwarf interstock (DT) or with a vigorous interstock (VF). Both orchards were trained with the spindle training system, in the conditions of Loess Plateau of China. For each cultivar and rootstock-interstock combination, 2 or 3 trees were digitized on which we estimated light interception and distribution at the tree scale. All trees were digitized at the current-year shoot scale, before harvest in 2011 and 2012. Shoots were distinguished according to length (long and short) and type (fruiting or vegetative). Virtual canopies were reconstructed based on allometric relationships and leaf angle distributions sampled at shoot and leaf scale in each year. Total leaf area (TLA), direct and diffuse projected leaf area (PLA) and silhouette to total leaf area (STAR) were estimated at the tree scale with the VegeSTAR software. TLA was affected by both cultivars and combinations, but PLA was only affected by combinations, for both diffuse and direct PLA. Moreover, STAR was affected by combinations, cultivars and years. The DT-trees compared to VF-trees and 'Gala' compared to 'Fuji' trees had higher STAR at tree scale and had higher number of voxels with higher STAR. In order to improve our understanding of rootstock - scion combination, we will use the RATP model to further study inter- and intra- tree microclimate and leaf functions (photosynthesis and transpiration)