Rootstock Influence on Apple Canopy Architecture Under High Radiation and Temperature

Abstract

Beside its typical and optimal area of cultivation in the central and northeast Albania, in the last decade, apple cultivation has been spread into the Western Plain, to benefit from the advantages of earliness and vicinity to the main markets. The scope of this research was to study the canopy architecture of five main cultivars grown in this region, ‘M. Gala’, ‘Gold Delicious’, ‘Starking’, ‘Fuji’ and ‘Pink Lady’ on M9 rootstock. The study was carried out from 2010-2011 in a 6-year old orchard, located at an altitude of 3 m, with 3.7 x 1.2 m distances in French axe system. The following measurements were made in 5 trees per cultivar: diameter of the rootstock, scion and two main branches at 1.5 m height, number of spurs, bourses and shoots, length of woody shoots and fruit set. Global radiation, temperature and humidity were recorded. The data shows a noticeable difference in rootstock/scion growth between the five cultivars tested. These differences are higher in the combination M9/‘M. Gala’ and ‘M9/‘Pink Lady’, with an affinity index of 0.49 and 0.52, respectively (< 0.6). The same trend is observed also with the diameter of the main branch, with partial incompatibility, which also modifies the other elements of canopy architecture, vegetation and reproductive growth. Changes are observed in ‘M. Gala’, with a small diameter of the main branch (14.7 mm), but with a higher number of fruiting shoots (18 fruiting shoots) and fruit set (45.3 fruits/ twig). It is followed by ‘Fuji’ and ‘Gold’. Although ‘Starking’ has a higher diameter (16.4 mm) of main branches, it forms more vegetation shoots and a small fruit set (20.8 fruits/ twig). There is a significant correlation between the branch diameter and the fruit set per twig. In conclusion, we can state that these cultivars show different behaviour towards M9 rootstock which has a significant effect on the elements of canopy architecture and fruit set.