YIELD POTENTIAL AND FRUIT QUALITY OF APPLE TREES TREATED WITH GIBBERRELLIN AND INHIBITOR OF GIBBERELLINS BIOSYNTHESIS

Recently published study has shown the apple trees treated with inhibitor of gibberellins biosynthesis have reduced vegetative growth and improved fruit quality. The aim of this study was to evaluate effects of spraying apple trees with prohexadione-calcium (ProCa) (an inhibitor of gibberellins biosynthesis) and gibberellin (GA(3)) on yield potential and fruit quality. The experiment was conducted in an orchard located in Sao Joaquim, State of Santa Catarina (Southern Brazil) in 2009/2010. 'Catarina' and 'Fuji' apple trees were treated with water (control), ProCa and GA(3) [both products at the dose of 319 g (a.i.) ha(-1)], when shoots were 5-10 cm long, with treatments repeated after 20 days. The number of flower buds and fruits in the plants was assessed in October and November, respectively, in 2009 and 2010. Fruit quality was assessed at harvest and after four months of cold storage (0 +/- 0.5 degrees C/90-95% RH), followed by seven days of simulated marketing (20 +/- 4 degrees C / 60-70% RH). In the year following the treatment of the trees (2010), 'Fuji' apples treated with ProCa had lower fruit set than the control. ProCa increased the red color in 'Catarina' apples. At harvest, the force for flesh penetration in the red side of the fruit was increased in apple trees of both cultivars treated with ProCa. After cold storage, 'Fuji' apples of trees treated with GA(3) had lowest flesh firmness, while 'Catarina' apples of trees treated with ProCa had highest flesh firmness. The GA(3) sprayed after full bloom (two treatments, each one at 319 g ha(-1)) might reduce the bloom of the following season and cause some changes in fruit quality attributes, leading to advanced maturity. The treatment with ProCa may increase the flesh firmness and red color in the 'Catarina' apples, and reduce return bloom and fruit set in the year following the treatment in 'Fuji' apples.