Effect of GA3 and NAA on growth, yield and fruit quality of Washington navel orange

Fruit drop and fruit quality are the most values in Washington navel orange since they are playing the main role in production and exporting potential. The present study was carried out during the two successive seasons of 2014 and 2015 on thirteen years Washington navel orange trees grown in sandy soil in a private orchard located at Housh Eisa, El- Behera Governorate, Egypt. The effect of GA3 and NAA applied one week after fruit set on Washington navel orange trees was studied. The results showed that foliar spraying of trees with GA3 at 20 ppm+ NAA at 25 ppm at one week after fruit set increased significantly vegetative growth parameters such as (shoot length (cm), leaves number per shoot at the three growth cycles, as well as leaf area (cm2) compared the other treatments and control. Spraying trees with GA3 at 20 ppm+ NAA at 25ppm decreased fruit drop percentage and increased significantly yield (kg/ tree), fruit physical parameters such as fruit weight (g), fruit size (cm3) fruit length, fruit diameter (cm) and fruit juice in comparison to other treatments and control. Fruit biochemical characteristics such as TSS, total acidity, TSS/acid ratio and V.C were also positively affected by using this treatment compared with other treatments and control. It could be recommended that spraying “Washington” navel orange trees with 20 ppm GA3 and 25 ppm of NAA one week after fruit set gave the highest values of yield (kg) /tree, fruit physical and chemical properties.