APPLICATION OF 3,5,6-TPA UNDER COMMERCIAL CONDITIONS TO CONTROL CALYX SENESCENCE ASSOCIATED TO DEGREENING TREATMENT

Postharvest degreening treatment with exogenous ethylene application is widely used in Mediterranean growth area to improve the external coloration of the early-season citrus varieties in which internal maturity is achieved when the peel is still green. Nevertheless this treatment can induce physiological disorders overall related to calyx senescence. In previous studies it has been reported that the application of 3,5,6-trichloro-2-pyridyloxyacetic acid (TPA) reduces calyx senescence associated to ethylene exposure. However it is important to know the effect of this auxin under commercial industrial conditions. The purpose of this study was to evaluate the effect of postharvest application of TPA on the reduction of disorders associated to degreening in clementines in different commercial post-harvest applications (by drencher and by low volume spraying in the handling line). The application of TPA by drencher significantly reduced the disorders of calyx senescence associated to degreening treatment in clementines, recommending 40 ppm of TPA as the most effective dose. The application of TPA by low volume spraying in the handling line treatments was effective on the reduction of calyx disorders, obtaining the best results with 100 ppm of TPA; nevertheless in the trials clementines exhibited low susceptibility to calyx disorders after degreening process. The results suggest that this auxin could be a good option to control disorders of citrus fruit during degreening treatment.