Enhancing feathering of one- and two-year-old nursery trees of 'Granny Smith' apple cultivar using benzyladenine and gibberellins

Synthetic cytokinin 6-benzyladenine (BA), when applied either alone or in combination with gibberellins (GA₄₊₇), plays an important role in the production of well-feathered apple nursery trees and in overcoming apical dominance. This paper presents the effects of BA and BA+GA₄₊₇ on the feather formation on one- and two-year-old 'knip-boom' nursery trees of apple cultivar 'Granny Smith'. In one-year-old trees, the solutions of BA and BA+GA₄₊₇ corresponding to the concentrations of 250, 350 and 450 µL L^-1 of active ingredient (BA) were applied three times at 7-day intervals during the growing season. In two-year-old 'knip-boom' trees application of 300 µL L^-1 BA, followed by 400 µL L^-1 of GA₄₊₇, were applied once, two or three times at 7-day intervals during growing season. Our findings indicate that increasing the BA concentrations (250-450 µL L^-1) leads to a decrease in the total number of feathers. On the other hand, GA₄₊₇ applications eliminate these negative effects. In addition, in one-year-old trees BA+GA₄₊₇ at the rate of 450 µL L^-1 induced the occurrence of longer feathers compared to BA applied alone. The positive influence of GA resulted in greater feather length. This effect was especially pronounced in two-year-old trees when GA₄₊₇ was applied two or three times. The treatments did not have any negative effects on tree height and trunk diameter.