CONVERSION OF 4-(2,4-DICHLOROPHENOXY)BUTYRIC ACID TO HOMOLOGS BY ALFALFA - MECHANISM OF RESISTANCE TO THIS HERBICIDE

After the application of 2,4-DB[4-(2,4-dichloro-phenoxy)butyric acid] to alfalfa (Medicago sativa L.), the authors detected 2,4-dichlorophenoxycaproic and 2,4-dichlorophenoxydecanoic acids as well as limited amounts of 2,4-dichlorophenoxycrotonic and 2,4-dichlorophenoxyacetic acids (2,4-D). Similarly applied methyl ester of 2,4-dichlorophenoxycrotonic acid was both reduced to the methyl ester of 2,4-DB and de-esterifled and reduced to 2,4-DB. All other metabolites mentioned were formed. The mechanism of the resistance of alfalfa to 2,4-DB may result from the synthesis of herbicidally inactive chlorophenoxy compounds having longer side chains than the parent herbicide. Thus, production of 2,4-D in lethal quantity by /3-oxidation and subsequent translocation to sites of action may be prevented. © 1968, American Chemical Society. All rights reserved.