FRUIT SET RESPONSES TO GIBBERELLIC ACID, NITROGEN AND GIRDLING ON ´HASS´ AVOCADO

The objectives of this study were to increase the initial fruit set with applications of GA₃+N+girdling; reduce the presence of floral abnormalities in winter bloom (Nov-Dec, 2003-2004), and evaluate the effect of the treatments on the quality of developing fruit corresponding to the winter-bloom of the previous year (2002-2003). GA₃ and N were applied to inflorescences at stage 8 of development (cauliflower stage, November) and girdling was performed in full bloom (January 3 2004). Flower abnormalities and initial fruit set were measured in January and February 2004 (0.5 cm diameter fruits), respectively. No interactions were recorded during initial fruit set; however, N and girdling increased fruit set by 49.6% and 79.8%, respectively; whereas the GA₃ application had no effect whatsoever. In spite of the treatments affecting the numbers in each evaluated floral structure, these differences were not reflected on the total percentage of abnormalities. Fruit weight increased with treatments of N (225 g), girdling (228 g), GA₃+girdling (238 g) and N+GA₃+girdling (254 g). Firmness and weight loss were not affected by the treatments, except for N+girdling, which favored weight loss (16%). The color components were differentially affected by the treatments; N, N+GA₃, and N + girdling treatments reduced L; while GA₃ maintained C and N + GA₃ delayed a decrease in hue angle values.