S16 - Session P2 - Understanding source-sink relationships in sweet cherry (Prunus avium L.) using the Kym Green Bush training system

Authors: Marlene Ayala *, María Paz Quiróz, Victor Blanco, Juan Pablo Zoffoli

In recent years, new training systems for sweet cherry intensive orchards have been implemented to facilitate management and reduce costs. Among them, the Kym Green Bush (KGB) promotes a pedestrian orchard with multiple vertical branches. Little knowledge about source n sink relationships is available for KGB, limiting horticultural practices such as crop load regulation, branch renewal and pruning. Accordingly, a preliminary experiment using phloem girdling (8 DAFB) on individual branches of the combination 'Lapins'/Colt (San Francisco de Mostazal, Chile), trained as KGB was established during spring 2019. Treatments included: TR1 - CTL = Control, branch without vascular restrictions, TR2 - G = girdling at the base of it, TR3 n 2G = girdling at the base and further up at the change of year between the second and the third years of growth. The vegetative and reproductive growth were monitored. At harvest, fruit quality (i.e., size, mass, soluble solid content, color, titratable acidity and firmness) and yield were measured. Significant differences (p < 0.05) in the harvest date, current season shoot (CSS) growth and fruit quality were observed among treatments. The upper half of TR3 n 2G branches was harvested 10 d before the lower half and 5 d before the branches of TR1 - CTL. The fruit from the upper half of TR3 n 2G was significantly larger (p < 0.0001), sweeter (p = 0.04) and softer (p = 0.04) compared to the other treatments. The upper half of TR3 n 2G developed a higher number of lateral CSS, but retained fewer fruits. We hypothesize that a higher CSS growth reduced fruit retention, which in turn increased fruit size and SSC. Additional efforts to improve source n sink manipulation are required to achieve high quality fruit in KGB trees, without affecting the delicate balance between reproductive and vegetative in this training system.