Bluprins® as Alternative Bud Break Promoter for ‘Maxi Gala’ and ‘Fuji Suprema’ Apple Trees

Aims: The effect of Bluprins® at different concentrations combined with calcium nitrate and ammonium nitrate on phenology, bud break induction and fruit production of 'Maxi Gala 'and' Fuji Suprema' apple tree cultivars was evaluated in mild winter conditions.

Study Design: The experiment was designed in randomised block and replicated five times.

Place and Duration of Study: The experiment was carried out in the municipality of Caçador, Brazil, during the growing seasons of 2013/2014, 2014/2015, 2015/2016 and 2016/2017.

Methodology: The study considered ‘Maxi Gala’ and ‘Fuji Suprema’ apple trees. The treatments evaluated were as follows: 1. Control (untreated); 2. Mineral oil 3.5% + hydrogen cyanamide 0.35%; 3. Bluprins® 3.0% + calcium nitrate 3.0%; 4. Bluprins® 5.0% + calcium nitrate 3.0%; 5. Bluprins® 3.0% + calcium nitrate 5.0%; 6. Bluprins® 5.0% + calcium nitrate 5.0%; 7. Bluprins® 3.0% + calcium nitrate 3.0% + ammonium nitrate 3.0%; 8. Bluprins® 5.0% + calcium nitrate 4.0% + ammonium nitrate 4.0%. Phenology, axillary and terminal bud break, fruit set, fruit production and average fruit weight were evaluated. The phenological stage of green tip (C-C3) and the beginning of bud break and flowering were anticipated by the application of Bluprins® and hydrogen cyanamide in compared to the control. The axillary and terminal bud break was increased by the application of bud break promoters for both cultivars considering the four growing seasons studied. The average fruit weight did not show significant differences between treatments in the growing seasons of 2013/2014 and 2015/2016. Bluprins®, in combination with calcium nitrate and ammonium nitrate, proved effective in inducing bud break of ‘Maxi Gala’ and ‘Fuji Suprema’ apple tree cultivars under mild winter conditions. The phenomenon is less effective with mineral oil in combination with hydrogen cyanamide. Bluprins® in combination with calcium nitrate and ammonium nitrate anticipates the bud break and flowering period and reduces the flowering period for ‘Maxi Gala’ and ‘Fuji Suprema’ apple tree cultivars in compared to plants without application of bud break promoters. Bluprins® does not affect considerably the fruit set and fruit production of ‘Maxi Gala’ and ‘Fuji Suprema’ apple tree cultivars.