PREFORMED ANTIFUNGAL COMPOUNDS OF CITRUS-FRUIT - EFFECT OF POSTHARVEST TREATMENTS WITH HEAT AND GROWTH-REGULATORS

Heat treatment (36 degrees C, 3 days) of lemon fruit Citrus Limon (L.) Burm. inhibited both the decline of antifungal activity in the flavedo tissue and the loss of the preformed antifungal material citral and drastically reduced the decay percentage. Dips in gibberellic acid (50 and 100 ppm) or in 2,4-dichlorophenoxyacetic acid (200 ppm) inhibited the decay development of stored fruit and slowed the decline of citral content and of the antifungal activity in the flavedo. On the contrary, ethylene treatment (25 or 50 ppm for 3 days at 25 degrees C) reduced the citral content and antifungal activity in the flavedo of both lemon and grapefruit(Citrus paradisi Macf.). The effect of postharvest heat treatment and plant growth regulators on citrus decay might be related to the modulation of endogenous disease resistance of fruit via influence on the changes of preformed antifungal materials such as citral.