Résumé
The effect of different rootstock/interstock combinations of M.9 and MM.106 on the architecture of 3-year-old branches of ‘Royal Gala’ apple was studied. Structure of the branches was described in terms of annual shoots (A, denoted A1 to A3, with the index representing the year of shoot development) consisting of growth units (GU). Three types of GU were distinguished: vegetative unit with internode extension (U), vegetative spur with minimal internode extension (S) and fruiting spur or bourse (F). A1 annual shoots in all treatments were monopodial and mostly comprised two extension units. Number of extension units per annual shoot A, dramatically decreased over subsequent years while number of fruiting and vegetative spurs per A, increased. Rootstock/interstock combinations did not affect this composition of annual shoots changing over the years. Total number of annual shoots (A2 and A3) per branch markedly decreased with decreasing vigour of the rootstock/interstock combination (MM.106/MM.106 > MM.106/M.9 > M.9/MM.106 > M.9/M.9). Number of nodes per U was similar in all treatments during the first year of development. In subsequent years this number had decreased and was affected by the vigour of the rootstock/interstock combination. Finally, the composition of annual shoots was not affected by the rootstock/interstock combinations, while the number of shoots per branch and the number of nodes per U in years 2 and 3 decreased with decreasing vigour of the rootstock/interstock combination