Induction of Budbreak in Apple Trees that Received Insufficient Chilling by Hydrogen Cyanamide

Abstract

Various concentrations of hydrogen cyanamide were applied to “Anna” apple to induce budbreak at the time when the trees were in dormant stage. The optimum concentration of hydrogen cyanamide to induce good budbreak was 2.5% High concentrations of hydrogen cyanamide were noticed to be toxic by dried dead shoots. ‘Tsugaru’ appli trees at different dormant stages kept in the heated glasshouse (minimum temperature was 15^oC) were treated with 2.5% hydrogen cyanamide plus 50% ‘Merit’, a foliar fertilizer. It was found that the mixer of hydrogen cyanamide and ‘Merit’ could relatively induce budbreak even when buds were in the deepest dormant stage, when compared with the buds in lesser dormant stage. Buds from ‘Tsugaru’ apple trees treated or not treated with 2.5% hydrogen cyanamide were analyzed for abscisic acid (ABA) content. It was found that three days after treatment, ABA content in buds treated with hydrogen cyanamide was two times lower than that in the untreated buds. This result suggested that hydrogen cyanamide may induce budbreak by decreasing ABA content.