Individual upright physiological traits in an apple “Guyot” training system

Light intercepted by the tree drives photosynthesis, and seasonal light integrals have been correlated to yields. Innovative training systems have recently been proposed that share the concept of shifting, from current 3D, to 2D ultra-thin canopy shapes. This shift allows making the orchard better suited for robotisation while increasing light interception to further boost yields. Examples of such innovative training systems are the “UFO”, the “Planar Cordon”, and the “Double-Guyot”. The latter two are based on 2 horizontal permanent cordons from which semipermanent shoots (uprights) are grown vertically to form a very thin, 2D fruiting wall. For the precise management of such trees, it would be useful to know whether the uprights are physiologically independent of each other or not. We report results from a 4-year-old ‘Rosy Glow’ apple orchard trained as “Guyot”, grafted on ‘Pajam 2’, at 1,443 trees ha-1, growing in the Po’ Valley - Italy. Fruit number and quality, upright dimensions, and leaf gas exchanges were measured on uprights with contrasting, naturally occurring crop loads (high and low); a number of uprights with different crop loads were girdled. Initial results indicate that the uprights are physiologically connected since in the girdled ones, photosynthesis is lower; crop load appears to stimulate photosynthesis in both types of uprights. For girdled uprights, fruit skin color had better intensity and extension, as well as °Brix values, despite higher flesh firmness. Correlations between yield and upright size (length, cross sectional area), leaf area (LA), and crop load are under investigation. Preliminary results indicate interesting relations between some of these parameters and yield and fruit quality. We conclude that the uprights should not be considered independent of each other and that accurate crop load control for each upright is necessary for precision orchard management of these novel training systems.