Induction of antifungal resorcinols in flesh of unripe mango fruits and its relation to latent infection by Alternaria alternata.
Droby S., Prusky D., Jacoby B., Goldman A.
Author Affiliation: Dep. Fruit Veg. Storage, ARO, Volcani Cent., PO Box 6, Bet Dagan, 50250, Israel.
Physiological and Molecular Plant Pathology 30 : 285-292
Abstract : A mixture of antifungal compounds (mainly 5-(12-cis-heptadecenyl)-resorcinol and 5-pentadecylresorcinol) was found at fungitoxic concn in the peel, but not in the flesh of unripe mango fruit. The unpeeled fruits were resistant to A. alternata, but freshly peeled fruits were susceptible. The flesh of peeled mango fruits became resistant to A. alternata infections within 24 h after peeling. During this period the concn of the 5-substituted resorcinols increased from 30 to 80 µg/g fresh wt. and continued to increase to reach a concn of 160 µg 96 h after peeling. A browning reaction, accompanied by increased activity of phenylalanine ammonia lyase (PAL), also occurred in the flesh as a result of peeling. Cycloheximide inhibited browning and PAL activity in the fruit flesh, but not the synthesis of 5-substituted resorcinols and the development of resistance to A. alternata. Anaerobiosis prevented flesh browning, the development of resistance in peeled fruits, and the increase in concn of the antifungal 5-substituted resorcinols. This work provides further evidence for the involvement of antifungal resorcinols in the latency of A. alternata in unripe mango fruits.