Reducing the incidence of calyx cracking in ‘Pink Lady’ apple using a combination of cytokinin (6-benzyladenine) and gibberellins (GA4+7)

Abstract

SummaryCalyx cracking in ‘Pink Lady’ apple (Malus × domestica Borkh.) results in substantial economic losses. ‘Pink Lady’ apple trees were sprayed with various rates and combinations of synthetic gibberellins (GA3, or GA4 plus GA7) and a synthetic cytokinin (6-benzyladenine; BA) at different phenological stages, starting at 60 d after full bloom (DAFB) until 150 DAFB, to determine if the incidence of cracking could be reduced. The experiments were conducted in Northern Israel between 2008 – 2011. The percentages of fruit with calyx cracking decreased following three applications of 0.2% (v/v) Superlon™ (i.e., 40 mg l–1 BA plus 40 mg l–1 GA4+7) at 14 d intervals, starting at 60 DAFB. GA3 or GA4+7 alone had no effect on cracking. In addition, the Superlon™ treatments resulted in increases in epidermal cell density at the calyx end, which may have contributed to the increased elasticity of the peel, thus preventing crack formation. No change was observed in cuticle thickness. Fruit quality was not affected by 0.2% (v/v) Superlon™ at harvest, or after 5 months of controlled atmosphere (CA) storage. However, fruit size increased, probably due to the effect of BA. The results from semi-commercial multiple applications of 0.2% (v/v) Superlon™ supported its use in orchards of ‘Pink Lady’ that tend to suffer from calyx cracking.