Fluazifop-P Inhibits Terbacil Metabolism in Strawberry (Fragaria×ananassa)1

Abstract

We examined the effect of a postemergence application of fluazifop-P on root uptake, translocation, and metabolism of 14C-terbacil in ‘Kent’ strawberry. Fluazifop-P had no effect on uptake of 14C-terbacil from a nutrient solution over 48 h, nor did it affect the proportional distribution of 14C-label in the plants. The 14C-label was readily translocated to the foliage where it tended to accumulate in vascular tissue. Fluazifop-P reduced the overall conversion of 14C-terbacil to metabolites by about 50%. Thin layer chromatography of methanol extracts of leaflets, petioles, crowns, and roots separated the 6-hydroxymethyl derivative, and several unidentified metabolites, including a major water-soluble metabolite at the origin. At least 50% of the latter could be converted to the 6-hydroxymethyl metabolite by β-glucosidase, but other metabolites could be separated in other solvent systems. The levels of metabolites were generally two- to threefold higher in plants treated with terbacil alone than in those pretreated with fluazifop-P. Therefore, we conclude that the interaction observed between these herbicides in the field results from fluazifop-P inhibiting detoxification of terbacil by strawberry.Nomenclature: Fluazifop-P; terbacil; strawberry, Fragaria × ananassa Duchensne ‘Kent’.Additional index words: Herbicide interaction, synergism, root uptake.Abbreviations: GC-ECD, gas chromatography electron capture detection; GC-MSD, gas chromatography mass spectrum detection; HPLC, high-performance liquid chromatography; LSS, liquid scintillation spectrometry; PPFD, photosynthetic photon flux density; SEM, standard error of the mean; TLC, thin layer chromatography.