Degradation of 4-Chloro-2-methylphenoxyacetic acid in top and subsoil is quantitatively linked to the class III tfdA Gene

A quantitative real-time PCR method was used to monitor the increase in the concentration of tfdA genes during degradation of the phenoxy acid herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) in sandy topsoil and subsoil over a period of 115 days. Analyses showed a shift in the dominant tfdA population structure occurred in the said period and the tfdA genes responsible for the degradation belonged to class III whereas the tfdA genes in the soil before degradation belonged to class I.