The effect of different bioregulators on lateral shoot formation in maiden apple trees

One-year-old Malus domestica Borkh. ‘Boskoop’ and ‘Mutsu’ nursery trees on M.9 rootstock were treated with foliar sprays of different BA + GA3 mixtures (450 + 450 mg dm-3 or 780 + 120 mg dm-3) or BA + GA4+7 combinations (450 + 450 or 330 + 570 mg dm-3). Both cultivars showed strong apical dominance; however, increased branching potential was observed following the use of exogenous growth regulators. All of the investigated branching agents revealed a high effectiveness, yet only after one treatment. Environmental factors played a major role in the induction of sylleptic shoot formation, especially in the case of ‘Boskoop’. In the case of ‘Boskoop’, the branching effect was correlated with several vegetative growth properties (tree height, trunk diameter), while for ‘Mutsu’, a different branching pattern was found with no correlations ascertained. No tree injuries were observed following the use of a chemical branching agent.