Translocation and Metabolism of Benazolin in Wild Mustard and Rape Species

Abstract

The fate of 4-chloro-2-oxobenzothiazolin-3-ylacetic acid (benazolin) in wild mustard [Brassica kaber(DC.) L.C. Wheeler var.pinnatifida(Stokes) L.C. Wheeler], turnip rape (Brassica campestrisL. ‘Echo’), and rape (Brassica napusL. ‘Target’) was investigated with the aid of14C-benazolin. The label was more mobile in wild mustard than the rape species following leaf treatment and accumulated in young leaves, stem, and stem apex. The label was also found in foliage after root treatment. In both cases, the translocated label was primarily that of14C-benazolin, implying phloem and xylem transport. The susceptibility of wild mustard and tolerance of the rape species to foliar-applied benazolin can be partly explained by different rates of transport to susceptible meristematic sites. Root exudation of the label following leaf treatment was greater in wild mustard than in the rape species and was not correlated with selectivity. Labeled benazolin was rapidly metabolized by theBrassicaspecies to four derivatives which appear to be less toxic than benazolin. Specific differences in metabolism were not sufficient to explain selectivity. Negligible amounts of14CO2were released by the three species following treatment with14C-benazolin.