Differential Metabolism of Metribuzin by Two Soybean (Glycine max) Cultivars

Abstract

Metribuzin-3-14C [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] was absorbed, translocated, and metabolized by both metribuzin-tolerant ‘Essex’ and metribuzin-sensitive ‘Coker 102’ soybean cultivars [Glycine max(L.) Merr.]. After 48 h Coker 102 accumulated 40% greater metribuzin equivalents in the shoots than Essex, but Essex shoots contained only 29% as much unaltered metribuzin as Coker 102, 1.08 and 3.68 μg per g dry weight, respectively. Essex is resistant to metribuzin primarily owing to a capacity to rapidly detoxify metribuzin to DA [6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one], to at least seven unidentified metabolites which remained in the aqueous fraction, and to an insoluble fraction. The unidentified metabolites in the aqueous fraction constituted the major detoxified breakdown products in both cultivars.