Metabolism of 2,4-dichlorophenoxyacetic acid contributes to resistance in a common waterhemp (Amaranthus tuberculatus) population

Authors

Marcelo R. A. Figueiredo, Colorado State University
Lacy J. Leibhart, University of Nebraska-Lincoln
Zachary J. Reicher, University of Nebraska-Lincoln
Patrick J. Tranel, University of Illinois
Scott J. Nissen, Colorado State University
Philip Westra, Colorado State UniversityFollow
Mark L. Bernards, Western Illinois UniversityFollow
Greg R. Kruger, University of Nebraska-LincolnFollow
Todd A. Gaines, Colorado State UniversityFollow
Mithila Jugulam, Kansas State UniversityFollow

Date of this Version

2017

Citation

Pest Management Science (2017), doi: 10.1002/ps.4811.

Comments

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Abstract

BACKGROUND: Synthetic auxins such as 2,4-D have been widely used for selective control of broadleaf weeds since the mid-1940s. In 2009, an Amaranthus tuberculatus (common waterhemp) population with 10-fold resistance to 2,4-D was found in Nebraska, USA. The 2,4-D resistance mechanism was examined by conducting [¹⁴C] 2,4-D absorption, translocation and metabolism experiments.

RESULTS: No differences were found in 2,4-D absorption or translocation between the resistant and susceptible A. tuberculatus. Resistant plants metabolized [¹⁴C] 2,4-D more rapidly than did susceptible plants. The half-life of [¹⁴C] 2,4-D in susceptible plants was 105 h, compared to 22 h in resistant plants. Pre-treatment with the cytochrome P450 inhibitor malathion inhibited [¹⁴C] 2,4-D metabolism in resistant plants and reduced the 2,4-D dose required for 50% growth inhibition (GR₅₀) of resistant plants by 7-fold to 27 g ha^-1, similar to the GR₅₀ for susceptible plants in the absence of malathion.

CONCLUSIONS: Our results demonstrate that rapid 2,4-D metabolism is a contributing factor to resistance in A. tuberculatus, potentially mediated by cytochrome P450. Metabolism-based resistance to 2,4-D could pose a serious challenge for A. tuberculatus control due to the potential for cross-resistance to other herbicides.