Antifungal compounds regulating quiescent diseases in mango.
Kobiler, I.; Reved, R.; Artez, L.; Prusky, D.;
ACIAR Proceedings Series Year: 1998 Issue: No. 80 Pages: 109-114 Ref: 9 ref.
1998
บทคัดย่อ
The most important postharvest diseases developing in mango fruit are anthracnose caused by Colletotrichum gloeosporioides [Glomerella cingulata] and black spot disease caused by Alternaria alternata. These pathogens infect mango fruit in the field and remain quiescent until harvest. To study the regulation of these quiescent fungal infections in mango fruit, endogenous antifungal compounds were examined, their effect on fungal symptom development assessed and factors affecting their activity and amount were investigated. The presence of a mixture of antifungal compounds in the mango peel is described. This consisted of substituted resorcinols: the major one being 5,12-cis heptadecenyl resorcinol, with 5-pentadecyl resorcinol secondary. This mixture of 5-substituted resorcinols is present at fungitoxic concentrations in the peel of the mango during the period of fruit growth, and decreases after the harvest and ripening of the fruit. The concentration becomes non-toxic to fungi at the time of in
itiation of the decay development. A new antifungal compound was identified recently as 5(7,12-heptadecadienyl) resorcinol. The concentration of this compound, present in the peel and the flesh of the fruit, is not reduced significantly with the fruit harvest and ripening. In order for this compound to play a functional role in delaying disease development it should be inducible to fungitoxic concentrations. Several treatments have been shown to elicit this compound. CO2 treatment applied to the harvested mango increased the concentration of the antifungal 5-(7,12-heptadecadienyl) resorcinol, concurrently with a delay of decay development. Furthermore, challenge inoculation of mango fruit with C. magna, a non-pathogenic strain on mango, increased the level of the antifungal 5-(7,12-heptadecadienyl) resorcinol in the peel of the inoculated fruits, and prevented the development of decay caused by mango pathogens. Also recently, the activity of additional antifungal compounds, still unidentified, was detected.
These antifungal compounds seem to vary between different cultivars of mango, showing differential activity toward the pathogens tested. It is concluded that a family of substituted resorcinols is present in mango fruit. Some of those compounds seem to have preformed fungitoxic activity and others are present at subtoxic concentrations and can be induced to fungitoxic levels.