Metabolism and Residues of 2,4-Dichlorophenoxyacetic Acid in DAS-40278‑9 Maize (Zea mays) Transformed with Aryloxyalkanoate Dioxygenase‑1 Gene

• Published in: Journal of agricultural and food chemistry 2016-10, Vol.64 (40), p.7438-7444
• Main Authors: Zhou, Xiao, Rotondaro, Sandra L., Ma, Mingming, Rosser, Steve W., Olberding, Ed L., Wendelburg, Brian M., Adelfinskaya, Yelena A., Balcer, Jesse L., Blewett, T. Craig, Clements, Bruce
• Format: Article
• Language: English
• Subjects: 2,4-Dichlorophenoxyacetic Acid - metabolism; 2,4-Dichlorophenoxyacetic Acid - pharmacokinetics; Canada; Chlorophenols - metabolism; Chlorophenols - pharmacokinetics; Dioxygenases - genetics; Herbicides - metabolism; Herbicides - pharmacokinetics; Limit of Detection; Pesticide Residues - metabolism; Pesticide Residues - pharmacokinetics; Plants, Genetically Modified - metabolism; Seasons; United States; Zea mays - drug effects; Zea mays - genetics; Zea mays - metabolism
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/acs.jafc.6b03104

DAS-40278-9 maize, which is developed by Dow AgroSciences, has been genetically modified to express the aryloxyalkanoate dioxygenase-1 (AAD-1) protein and is tolerant to phenoxy auxin herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D). To understand the metabolic route and residue distribution of 2,4-D in DAS-40278-9 maize, a metabolism study was conducted with 14C-radiolabeled 2,4-D applied at the maximum seasonal rate. Plants were grown in boxes outdoors. Forage and mature grain, cobs, and stover were collected for analysis. The metabolism study showed that 2,4-D was metabolized to 2,4-dichlorophenol (2,4-DCP), which was then rapidly conjugated with glucose. Field-scale residue studies with 2,4-D applied at the maximum seasonal rate were conducted at 25 sites in the U.S. and Canada to measure the residues of 2,4-D and free and conjugated 2,4-DCP in mature forage, grain, and stover. Residues of 2,4-D were not detectable in the majority of the grain samples and averaged