Improvement of Fruit Set of Some Citrus Varieties Using Naphthalene Acetic Acid and Gibberellic Acid Concentrations

The effects of Naphthalene acetic acid (NAA) with the concentrations of 0, 2.5, 5 and 10 ppm and Gibberellic Acid (GA3) with 0, 25, 50 and 100 ppm were used objectively improving (fruit set) initial fruit set and horticultural fruit set. Each growth regulator (NAA or GA3) concentrations were applied on 5 different citrus cultivars. These varieties were Valencia, Hamlin, Temple and Navel orange and Dancy tangerine. The study showed significant variation among studied cultivars in their response to hormonal applications. Moreover, the 2 tested growth regulators at the different concentration were found to influence differently. Gibberellic acid applications, in general were found to improve initial fruit set (IFS) percentage in most studied cultivars particularly Hamlin and Naval orange. On the other hand, Temple orange trees responded negatively. Horticultural fruit set (HFS) significantly increased, in general, from 39% (average of all cultivars-control) to 109%. Overall mean of the cultivars were treated with NAA, they had (179.49% increase) and increased from 0.39 to 1.69% under the treating with GA3 (333.33% increase).