ENHANCED METABOLISM OF FLUAZIFOP ACID IN A BIOTYPE OF DIGITARIA-SANGUINALIS RESISTANT TO THE HERBICIDE FLUAZIFOP-P-BUTYL

A population of Digitaria sanguinalis has evolved resistance to the he rbicide fluazifop-P-butyl following selection with six applications of this herbicide over 4 years. The resistant population is also resista nt to the chemically similar aryloxyphenoxypropanoate (APP) herbicides haloxyfop-methyl and quizalofop-P-ethyl, shows a lower level of resis tance to the cyclohexanedione (CHD) herbicide sethoxydim, but is not r esistant to clethodim. Acetyl-coenzyme A carboxylase isolated from pla nts of both resistant and susceptible populations was equally sensitiv e to APP and CHD herbicides. Absorption of [C-14]fluazifop-butyl and t ranslocation of C-14 from [C-14]fluazifop-butyl were similar in plants from both populations. Plants of both resistant and susceptible popul ations rapidly hydrolyzed [C-14]fluazifop-butyl to [C-14]fluazifop aci d in leaves; however, [C-14]fluazifop acid was metabolised to other co mpounds at a more rapid rate in the resistant plants. Enhanced metabol ism of the toxophore fluazifop acid is a likely mechanism of resistanc e in this population. (C) 1997 Academic Press.