Induction of Senescence and Foliar Abscission in Apple Trees with the Use of Abscisic Acid

Aims: Evaluate the effects of different concentrations of abscisic acid (ABA) on adult plants of productive age of ‘Daiane’ and ‘Fuji Suprema’, to follow the ecophysiological effects and their efficiency in inducing leaf senescence, sprouting and productivity, in the Midwestern region of the state of Santa Catarina.

Study Design: The experiment was arranged in a randomized block design with six replications. Place and Duration of Study: The experiment was carried out in the municipality of Caçador, Brazil (latitude 26º50’07” S, longitude 50º58’32” W, altitude 969 meters), during the growing seasons of 2013/2014 and 2014/2015.

Methodology: The apple fruit tree were submitted to the following treatments: 1) Control (without treatment), 2) abscisic acid 750 mg L-1, 3) abscisic acid 750 + 750 mg L-1, 4) abscisic acid 1500 mg L-1 and 5) abscisic acid 1500 + 1500 mg L-1. ABA applications in the first year were carried out on May 2, 2013 in treatments 2, 3, 4, and 5, and after 11 days (05/13/13) the plants of treatments 3 and 5 were sprayed again. In the second year, ABA applications were carried out on May 6 and 15, 2014, following the same application methodology described for the first year. As the source of abscisic acid (ABA) the commercial product ProTone® (20% i.a.) was used, without the use of adjuvant. The exogenous application of ABA was effective in promoting the senescence and leaf fall of the ‘Daiane’ and ‘Fuji Suprema’ cultivars. In the 2013/2014 season, the concentration of 750 mg L-1 was enough to induce 100% leaf fall in 'Daiane' plants. However, a difference was observed between the concentrations of ABA used. There was a difference between concentrations and number of applications. Lower concentrations were efficient and deflated as much as the higher concentration. The application of ABA induces the abscission of apple leaves in early autumn in 'Daiane' and 'Fuji Suprema' apple plants. The ABA does not affect shoots of axillary buds and anticipates the beginning of shoots.