Inducing sylleptic branching in the interspecific pear ‘PremP109’

Abstract

Use of well-feathered trees when establishing an orchard promotes early cropping; however, many pear cultivars do not readily form sylleptic branches in commercial nurseries. Observations of young trees of the interspecific pear ‘PremP109’ suggest it has an upright habit with minimal natural branching, which leads to slow canopy establishment. Plant growth regulators with cytokinin-like activity have been applied to a range of fruit trees in nurseries to induce sylleptic branching, resulting in well-feathered trees. This investigation compared the efficacy of cyclanilide (CYC) at 5, 10, 50, 100, or 1,000 ppm and 6-benzylaminopurine (BA) at 1000, or 3000 ppm treatments and two controls, on feathering of two-year-old headed ‘Premp109’ nursery trees. All treatments except one control were subsequently sprayed with four weekly applications of gibberellic acid (GA(3)) at 200 ppm, to encourage extension of any sylleptic branches that formed. The control and GA(3) only treatment produced no branches and averaged about four spurs tree(-1). Application of BA or CYC increased the number of spurs and shoots produced, with the lower concentrations of CYC being more effective than higher concentrations. The number of spurs produced doubled for the BA 3,000 ppm, CYC 5 and CYC10 ppm treatments, when compared with the controls. However, the number of extended shoots produced were low, ranging between 0.2 and 2.2 shoots tree(-1). The length of the shoots produced were longest for the BA1000 treatment averaging 203 mm, while the shoot lengths produced by the remaining effective treatments ranged between 27 and 86 mm. These results highlight the difficulty in inducing sylleptic branching in ‘PremP109’, and reinforce the need for tree training systems that utilize the natural non-branching growth habits of fruit trees such as these.