Presence of antifungal compounds in the peel of mango fruits and their relation to latent infections of Alternaria alternata.
Droby S., Prusky D., Jacoby B., Goldman A.
Author Affiliation: Dep. Fruits Vegetable Storage, ARO, Volcani Cent., Bet Dagan, 50250, Israel.
Physiological and Molecular Pathology 29 : 173-183
Abstract : An antifungal agent consisting of a mixture of 5-(12-cis-heptadecenyl)- and 5-pentadecyl-resorcinol was isolated from the peel of unripe mango fruits. The ED50 of the compound for inhibition of germ-tube growth of germinated conidia of A. alternata was 120 µg/ml. The concn of the 5-substituted resorcinols in peels of unripe fruits was c. 200 µg/g fresh wt. and it decreased during ripening to c. 100 µg, the decrease being accompanied by development of previously latent A. alternata infections. Treatments of mango fruits with ethylene reduced the latency period and reduced the concn of the antifungal compound. Storage of fruits at hyperbaric pressures (20 kPa) maintained latency and delayed the reduction of the antifungal resorcinols. The concn of the 5-substituted resorcinols decreased differentially during ripening of 2 mango cultivars which also differed in the rates of the development of A. alternata symptoms. In the resistant, Kitt, the concn in the peel did not decrease to a non-fungitoxic level when the flesh had ripened. The results support the hypothesis that the mixture of the 5-substituted resorcinols is involved in the latency of A. alternata infections in unripe mango fruits.