02266naa a2200181 a 450000100080000000500110000800800410001910000170006024501390007726000090021652016830022565000260190865000240193465000240195870000200198270000140200277300680201611340732023-12-12       2023    bl uuuu     u00u1 u    #d1 aPETRI, J. L.  aThe efficiency of ACC in the fruit thinning of 'MaxiGala' apple applied in four stages and five concentrations.h[electronic resource]  c2023  aThis study aimed to evaluate the agronomic efficiency and practicality of different doses of ACC (1-aminocyclopropane-1- carboxylic acid) in the chemical thinning of apples (Malus domestica), and its effect on phytotoxicity when applied at petal fall, 8- 10 mm, 18-20 mm and more than 25 mm fruitlet diameter. The experiment was locatedin an orchard in the city of Ca??ador, SC, Brazil. A randomized complete block design wasused, with seven treatments and six replications, using ?MaxiGala?. The treatments were: 1) Control (manual thinning); 2) ACC 0.25 kg ha-1; 3) ACC 0.5 kg ha-1; 4) ACC 0.75 kg ha-1; 5) ACC 1.0 kg ha-1; 6) ACC 1.25 kg ha-1 and 7) Ethephon 0.5 mL ha-1. Application time were: end of flowering, 8-10 mm, 18-20 mm and more than 25 mm fruit. The doses of ACC 1.00 and 1.25 kg ha-1 applied to the end of flowering provided excessive thinning in the apple tree. The doses of 0.25, 0.5 and 0.75 kg ha-1 presented results similar to manual thinning (Control). For applications of ACC to 8-10 mm fruitlets, the dose of 1.25 kg ha-1 was excessive, but doses of 0.5 to 1.0 kg ha-1 were effective and superior to the Ethephon treatment. For 18-20 mm fruits, dosages of 1.0 and 1.25 kg ha-1 of ACC showed greater efficiency than lower dosages. Fruits greater than 25 mm in diameter had reduced the percentage of fruit drop compared to previous stages. As a result, we can conclude that doses of 0.5 and 0.75, 1.0, and 1.25 kg ha-1 of ACC have agronomic efficacy and recommended for thinning apple cultivar ?MaxiGala?. The dosages depend on the application stage, and doses of 1.0 and 1.25 kg ha-1 should only be applied in the stages of fruits above 18 mm in diameter.  afruit load adjustment  afruit set reduction  aincrease fruit size1 aSEZERINO, A. A.1 aCOUTO, M.  tActa Horticulturae, Leuven, Belgiumgn. 1366, p. 261-268, 2023.