EFFECT OF TRYPTOPHAN, SALICYLIC AND ASCORBIC ACIDS ON PRODUCTIVITY AND FRUIT QUALITY OF NAVEL ORANGE TREES

Abstract

A field experiment was carried out during the 2019 and 2020 seasons on 12-year-old Navel orange trees grown in El Bustan district, El Behera Governorate, Egypt. Three concentrations (25, 50 and 75 ppm) of tryptophan, (100, 200 and 300 ppm) of salicylic, and (500, 750 and 1000 ppm) of ascorbic as well as the control (tape water) were foliar application three times a year, i.e., at full bloom stage and the second one was performed just after fruit setting and the third was sprayed four weeks later. The results showed that, tryptophan treatment at 75 ppm improved shoot length, tree height, tree canopy volume, fruit weight, fruit length, fruit diameter, and fruit volume. Moreover, salicylic as foliar application at 300 ppm increased fruit set percentage, fruit retention percentage, numbers of fruits/ tree, yield, yield efficiency, peel thickness, juice weight, fruit juice percentage, TSS, ascorbic acid content, and total sugars content.