THE EFFECTIVENESS OF PREHARVEST FOLIAR SPRAY OF SOME BIOLOGICAL MATERIALS ON KEEPING QUALITY OF VALENCIA ORANGE FRUITS DURING COLD STORAGE

this experiment was conducted during two successive seasons, 2012 and 2013, on 15 years old ″Valencia″ orange trees at a private orchard. Two plant bio stimulants (Lena tonik, Licorice extracts) and GA3 were sprayed during different fruit growth stages. Five separate treatments, GA3 at 100 ppm, Lena tonik at 0.50 and 0.75 cm / L and Licorice extract at 0.2 and 0.4 % plus distilled water as control were applied, monthly from June till September. Fruits were picked at maturity stage and all fruit quality parameters were determined at harvest and at two weeks interval during storage for 6 weeks at 4ºC and 90% to 95 % relative humidity. Measured fruit quality parameters included weight loss percentage, firmness; peel color, eating quality, total soluble solids contents, titratable acidity content and Vitamin C content. GA3 treatment caused an obvious delay in fruit ripening processes compared to other treatments and control. Fruits treated with GA3 had the highest value of firmness and TSS content least values of color development at harvest. Moreover, these fruits in addition to those treated with Lena tonik had the lowest weight loss incidence and the less firmness deterioration rate and delaying senescence incidence during cold storage. After 6 weeks of cold storage, Licorice treated fruits had the best taste followed by Lena tonik, while GA3 treatment had the lowest one, but with acceptable note of taste. All treatments of biostimulants proved their usefulness in keeping ″Valencia″ orange fruit quality during cold storage. Licorice extract can be used for its effectiveness in keeping fruit quality and its cheap price in case other materials are unavailable.