Identity and Activity of 2,4-Dichlorophenoxyacetic Acid Metabolites in Wild Radish (Raphanus raphanistrum)

Synthetic auxin herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D), are widely used for selective control of broadleaf weeds in cereals and transgenic crops.

Although the troublesome weed wild radish (Raphanus raphanistrum) has developed resistance to 2,4-D, no populations have yet displayed an enhanced capacity for metabolic detoxification of the herbicide, with both susceptible and resistant wild radish plants readily metabolizing 2,4-D.

Using mass spectrometry and nuclear magnetic resonance, the major 2,4-D metabolite was identified as the glucose ester, and its structure was confirmed by synthesis. As expected, both the endogenous and synthetic compounds retained auxin activity in a bioassay.

The lack of detectable 2,4-D hydroxylation in wild radish and the lability of the glucose ester suggest that metabolic 2,4-D resistance is unlikely to develop in this species.

If you’ve got questions about this paper, you can email Dr Danica Goggin: danica.goggin@uwa.edu.au