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

Abstract

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 twoyear- 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 oneyear- 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.