Degradation of benzoic acid by Nectria galligena Bres. in vitro and in vivo

Abstract

The concentration of benzoic acid in the diseased area of immature Bramley's Seedling apple fruits inoculated with Nectria galligena decreased as the arrested lesions expanded into progressive rots, and none was detected in natural canker rots. Benzoic acid was not degraded in healthy apple tissue, even after prolonged incubation. In in vitro experiments hyphae of N. galligena were shown to degrade radioactively labelled benzoic acid to 14CO 2. Detected intermediates in this reaction were p-hydroxybenzoic, protocatechuic and β-oxoadipic acids. Of these compounds p-hydroxybenzoic acid and trace amounts of protocatechuic acid were also detected in lesions as they expanded into progressive rots. Degradation of benzoic acid by N. galligena in vitro was most rapid at pH 6·75, and proceeded very slowly at pH 3·4, a value similar to that of the fruit sap. It is suggested that in vitro metabolism of benzoic acid by the fungus takes place with increases in pH and soluble sugars in the ripening apple.