Detoxification of the Fusarium Toxin Fusaric Acid By the Soil Fungus Aspergillus Niger

The fungal pathogen Fusarium oxysporum f. sp. vasinfectum (F.o.v.) causes cotton wilt and produces the toxin fusaric acid (FA). Previous research indicates that in the high producing strains of F.o.v., FA plays an important role in virulence.  To address the problems of emerging virulent isolates such as Australian biotype and California race 4 isolates possessing high FA production capacity, mechanisms of FA detoxification in microorganisms have been evaluated. Screening of a soil sample from a cotton field infested with Reniform nematode and Fusarium identified and isolated an Aspergillus niger strain with high tolerance to FA. HPLC analysis of culture filtrates from A. niger grown in the presence of FA showed that FA degraded and decreased, and an unknown compound appeared and increased over time.  Spectral analysis of the unknown compound and the chemical synthesis of the unknown compound identified the compound as 5-butylpyridine-2-methanol (fusarinol). The phytotoxicity of fusarinol compared to FA at different concentrations was measured by the ability of the compound to cause necrosis on cotton (Gossypium hirsutum L. cv. Coker 312) cotyledons.  The toxic effects of fusarinol are significantly less than FA, providing a novel detoxification mechanism against FA mediated disease.