Degradation of fluometuron by Rhizoctonia solani

Abstract

Degradation studies of fluometuron [Cotoran, 1,1-dimethyl-3-(α,α,α-trifluoro- m-tolyl)urea] by Rhizoctonia solani have been conducted to elucidate further the pathway of degradation. Analysis by thin-layer chromatography and autoradiography demonstrated that R. solani degraded 88% of fluometuron ( 14CF 3 − ) into seven nonpolar metabolites after 35 days of incubation. Trace amounts of polar, water-soluble products were detected, but no 14CO 2 or radioactive volatile products were detected. Two of the major metabolites were identified by thin-layer chromatography and ultraviolet spectroscopy as 1-methyl-3-(α,α,α-trifluorotolyl)urea and (3-trifluoromethylphenyl)urea, which indicated a stepwise demethylation of fluometuron. The remaining five metabolites have not been identified and have not been previously reported in the literature. Time course experiments and metabolite degradative studies indicated that the sequence of degradation involved a multibranched pathway which did not include CO 2 evolution. The proposed pathway does not include the conversion of fluometuron to the aniline derivative as has been reported for other urea herbicides. All of the data from this study indicate the incomplete degradation of fluometuron which suggests a cometabolic degradative pathway.