Acetic acid and n-butyric acid as causal agents of fungicidal activity of glucose-amended flooded soil.

Abstract

Volatile fungicidal substances, which affect the survival of Fusarium oxysporum f. sp. raphani in soil flooded with 3% glucose solution in vitro, were analysed by using a cryogenic trap, by bioassay, gas chromatography and gas chromatography-mass spectrometry. The an tifungal volatile substances collected consisted of two components: acetic acid and n-butyric acid. Their concentrations in the centrifuged supernatant of the soil were 3,407 and 2,944 ppm, respectively, when the fungicidal activity in the soil reached maximum values on the 6th day after flooding. The concentrations were high enough to kill the chlamydospores of the fungus. Other volatile substances including hydrogen sulfide were not related to the fungicidal activity of the soil. These results suggest that the fungicidal activity of glucose amended flooded soil was associated with the production of acetic acid and n-butyric acid in the soil.