Agronomy and Horticulture, Department of
Date of this Version
Fall 10-10-2015
Document Type
Project
Citation
Crespo, R.J. 2015. Assessing Multiple-Herbicide Resistance in a 2,4-D Resistant Waterhemp (Amaranthus tuberculatus) Biotype from Nebraska – Student Research. University of Nebraska-Lincoln. Lincoln, NE, US.
Abstract
A waterhemp biotype was recently reported resistant to 2,4-D in Nebraska. In addition to the repeated use of 2,4-D, atrazine and imazathapyr were reported to be frequently used to control broadleaf weeds. Greenhouse experiments were conducted to confirm 2,4-D resistance and test for resistance to growth regulator herbicides and other herbicide modes-of-action (MoA). A single dose-response experiment showed reduced sensitivity in all three waterhemp biotypes to atrazine, imazethapyr and lactofen; therefore, they were generally considered resistant to those three herbicide MoA. None of the biotypes contained the Ser264 target-site mutation. Since the ametryn dose-response experiment resulted in all susceptible biotypes, atrazine resistance is suspected to be metabolism based. Trp574Leu mutation conferring broad cross-resistance to ALS-inhibiting herbicides including imidazolinones and sulfonylureas was identified in the two 2,4-D susceptible waterhemp biotypes. Trp574Leu mutation was not found in the 2,4-D resistant biotype, but Ser653 mutation conferring resistance to imidazolinones was identified. However, dose-response experiments showed reduced sensitivity of the 2,4-D resistant biotype to chlorimuron-ethyl. Despite the 50% survival rate or higher of plants treated with lactofen, results from sequencing the PPX2L gene conferring resistance to PPO-inhibitor herbicides were not quite clear. The present manuscript confirms that the 2,4-D resistant biotype found in Nebraska is also resistant to herbicides belonging to PSII- and ALS-inhibitors. Additionally, the 2,4-D resistant biotype is resistant and has reduced susceptibility to some other growth regulator herbicides.
Comments
This publication contains results from Student Research carried out at the Department of Agronomy and Horticulture of the University of Nebraska-Lincoln in the 2011-2012 academic year. The results presented here was obtained as part of the Graduate Research Assistantship held by Mr. Crespo under the supervision of Dr. Greg Kruger (University of Nebraska-Lincoln) and Dr. Roch Gaussoin (University of Nebraska-Lincoln). I also acknowledge the intellectual contributions of Dr. Mark Bernards (Western Illinois University), Dr. Pat Tranel (University of Illinois) and Dr. Chance Riggins (University of Illinois). E-mail: rojacre@yahoo.com.ar