Performance of ‘Maxi Gala’ apple trees as affected by budbreak promoters, in São Joaquim-SC

Abstract

Abstract The application of rest breaking agents to compensate the lack of chilling is a common practice in apple orchards in Southern Brazil. However, its necessity in areas of greater chilling accumulation has been questioned over the years. The aim of this study was to investigate the performance of ‘Maxi Gala’ apple in response to different budbreak promoters in São Joaquim, SC. The study was performed in the growing seasons of 2013/2014, 2014/2015, and 2015/2016. Plant material consisted of 10-year-old ‘Maxi Gala’ apple trees grafted on the rootstock ‘M.9’, arranged in a randomized complete block design with five replicates in the 2013/2014 and 2014/2015 growing seasons and six replicates in the 2015/2016 season. Treatments consisted of Erger®, combined with either calcium nitrate or mineral oil, at different rates; and hydrogen cyanamide combined with mineral oil. Treatments were applied when buds were between the stages A (dormant bud) and B (swollen bud; silver tip). The influence of treatments on flowering, budbreak, yield components, and fruit quality was assessed. Flowering was little affected by treatments, while axillary budbreak was consistently improved in the year of insufficient chilling accumulation. Besides, the combination Erger® (2% and 3%) + calcium nitrate (2% and 3%) and Erger® (1%) + mineral oil (3%) induced similar axillary budbreak as hydrogen cyanamide + mineral oil. Fruit quality attributes were not affected by treatments.