The use of 6-benzyladenine to increase same-season branching on one-year-old lateral extension growth of third-leaf apple trees
In regions with inadequate winter chilling, apple trees are often trunk renewed (removal through a heading cut of all lateral one-year-old shoots on the trunk (leader), leaving a stub) to increase leader growth. Insufficient reproductive buds are therefore developed on such trees, and the subsequent crop is limited to lateral and terminal buds on new one-year-old shoots - thus limiting the crop potential. Plant growth regulators are used as summer foliar applications to induce sylleptic development of tree leaders in nurseries, but not on one-year-old shoots in orchards to increase crop potential. Field trials were conducted on 3rd leaf 'Brookfield Gala' and 'Golden Delicious' on MM109 in 2014 and repeated on a similar orchard in 2015. Trials were conducted in the Elgin region, South Africa (34.1486°S; 19.0428°E). Both seasons, the effect of a single foliar application of 950 mg L-1 6-benzyladenine to the lower tree canopy on December 16 was evaluated. The number and length of lateral spurs or short shoots branching from the new shoots as well as the percentage lateral shoots with spurs/short shoots increased significantly during both seasons. In 2016, the subsequent crop increased significantly although the number and length of lateral shoots, leader length, leader diameter and trunk diameter did not differ in the two seasons.
Müller, A.M. and Theron, K.I. (2018). The use of 6-benzyladenine to increase same-season branching on one-year-old lateral extension growth of third-leaf apple trees. Acta Hortic. 1206, 63-68
Malus domestica (Borkh.), 6-BA, bearing positions, MaxCel