The effect of chilling, defoliation and hydrogen cyanamide on dormancy release, bud break and fruiting of Anna apple cultivar

Abstract

The effect of defoliation (DEF) alone or combined with hydrogen cyanamide (HC) on dormancy state, fruit quality and yield of Anna apple cultivar was studied. Trees were manually defoliated on three successive dates, November 15th, December 1st and December 15th. The flower buds (FB) entered the endodormancy synchronized with vegetative buds (VB) for most of the treatments. Most of the treatments terminated endodormancy between January 27th and February 8th during the season 2004/2005 and between January 18th and February 8th during the season 2005/2006. The treatments were effective in dormancy release of FB and somewhat with VB. Defoliation on November 15th + HC recorded the lowest chilling accumulation needed to reach 50% bud break. All the treatments exceeded the control considering the percentage of flower (FBB) and vegetative bud break (VBB) either in the lab or at the field. Growing degree hours and the number of days required to reach each stage of fruiting were differed between the two studied seasons. The control and DEF on December 15th exceeded all the treatments regarding initial fruit set percentage (IFS). The defoliation treatments alone gave the highest yield (kg/tree). Defoliation + HC treatments gave the best fruit quality, while the control gave the least values.