Pomological and physiological characteristics of Slender Pyramid central leader apple (Malus domestica) planting systems grown on intermediate vigour, semi-dwarfing, and dwarfing rootstocks

Abstract

Three apple (Malus domestica Borkh.) planting systems utilising medium vigour (MM.106, 5.0 × 3.0 m), semi-dwarf (M.26, 4.0 × 2.0 m), or dwarf (Mark, 4.0 × 2.0 m) rootstocks were compared using pomological and physiological attributes affecting productivity and fruit quality of the cultivar ’Fuji’. All planting systems were grown using Slender Pyramid tree management. Individual tree size increased with rootstock vigour, but canopy development per unit land area was similar for planting systems on MM.106 and M.26. Light interception was up to 50% less in the Mark dwarf tree system which corresponded to small tree size and limited canopy growth once cropping began. Leaf area index of the dwarf tree system on Mark was 1.9, half that of systems on MM.106 and M.26, whereas leaf area density of 3.7, was more than 50% higher than for the other systems. Irradiance reaching the lower inner canopy region of trees was most affected by canopy aspect with highest irradiance in the eastern sector and lowest in the southern sector for all planting systems. Floral precocity of trees on all rootstocks was not limiting to production but was proportionally higher on trees grown on Mark rootstock. Yield in the first cropping year (third season) was greatest for planting systems with highest tree density although the Mark dwarf tree system had the highest initial production. Continued canopy growth in the systems on MM.106 and M.26 resulted in higher yields than from the Mark planting system from the fourth year onwards. Peak yields within 6 or 7 years reached 110 t/ha. Highest cumulative yields occurred with the M.26 semi-dwarf planting system. The proportion of fruit achieving export quality standard was lowest from the intermediate vigour MM.106 planting system. Inadequate fruit red colour was the most common quality defect. Performance of these alternative planting systems is discussed in relation to the physiological requirements for optimising the efficiency of apple planting systems.