Degradation of a herbicide, Beflubutamid, in upland soils and isolation of its degrading microbes

Abstract

To clarify the degrading mechanisms of a newly synthesized herbicide, Beflubutamid ([RS]-N-benzyl-2-[4-fluoro-3-trifluoromethylphenoxy]butanamide; BFB), in soil, we started a series of studies. The results on the characteristics of degradation in soil, and on the isolation and identification of BFB-degrading microbes are summarized as follows. BFB was immediately degraded in non-sterilized soil, but degraded little in sterilized soil, indicating that soil microbes are involved in BFB degradation in soil. Results suggested that the application of sawdust and cattle manure (CM) increased the population and activities of microbes because the degrading activity was greater in CM-applied soil than in soil supplied with chemical fertilizer. According to the morphological characteristics and 18S rDNA sequences, the isolated strain MF1 was categorized as the class Ascomycota, belonging to the order Hypocleales, and closely related to Gibberella fujikuroi, Fusarium oxysporum f. sp. Vasinfeatum and Gibberella puricaris. The results suggested that BFB degrades fastest under acidic conditions because the growth of strain MF1 was at an optimum at pH 6.5 and was depressed at neutral and alkaline pHs.