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Title:Characterization of HPPD-inhibitor resistance in waterhemp (Amaranthus tuberculatus)
Author(s):Hausman, Nicholas
Advisor(s):Hager, Aaron G.
Department / Program:Crop Sciences
Discipline:Crop Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Waterhemp (Amaranthus tuberculatus)
4-hydroxyphenylpyruvate dioxygenase (HPPD)
Abstract:Waterhemp, a summer annual species native to much of the Midwest, has proven to be one of the toughest weeds for Illinois producers to control. Several characteristics of waterhemp make this species ideally suited to thrive in Illinois agricultural fields, including but not limited to high seed production, extended emergence, and seed dormancy. The evolution of herbicide resistance in waterhemp has introduced an additional obstacle producers must face when trying to manage this troublesome weed. In the summer of 2009, a waterhemp population in a seed corn production field in McLean Co., IL was not adequately controlled following foliar applications of 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides. Chapter 1 of this thesis includes a review of the literature pertaining to HPPD inhibitors, namely their discovery and uses as herbicides, as well as a section on waterhemp biology. Chapter 2 discusses the initial greenhouse research used to determine if the waterhemp population from McLean Co. (designated MCR) had indeed evolved a novel form of resistance to HPPD inhibitors. Plants grown from seed collected at the suspected resistance site demonstrated reduced sensitivity to foliar applications of the HPPD inhibitors mesotrione, tembotrione, and topramezone. Furthermore, a mesotrione dose response comparing MCR with two known HPPD inhibitor-sensitive waterhemp populations revealed the level of resistance to be 10-to 35-fold. The efficacy of foliar-applied HPPD inhibitors at the McLean Co. location is addressed in Chapter 3. Similar to findings of the previous greenhouse experiments, HPPD inhibitors did not provide adequate control of this population, and mortality data indicate a high percentage of plant survival when these herbicides were applied at their recommended field use rates. Additional field and greenhouse research presented in Chapter 3 indicates that MCR also demonstrates resistance to acetolactate synthase (ALS) inhibitors and photosystem II (PSII) inhibitors, while glyphosate, glufosinate, and protoporphyrinogen oxidase (PPO) inhibitors generally provide the greatest control of this population. Chapter 4 discusses the efficacy of various soil-applied residual herbicides to determine appropriate control options for the McLean Co. waterhemp population. Under field conditions, acetochlor, sulfentrazone, flumioxazin, metribuzin, and pyroxasulfone generally provided the highest levels of waterhemp control and greatest reduction in waterhemp density. Chapter 4 also includes a soil-applied mesotrione dose response comparing HPPD inhibitor-resistant waterhemp (MCR) and RxR progeny (derived from greenhouse crosses of HPPD-resistant waterhemp) with an HPPD inhibitor-sensitive biotype. Subsequent resistant-to-sensitive (R/S) ratios revealed a 9-to 13-fold level of resistance. Finally, Chapter 5 includes a summary of experiments, as well as implications of the research presented herein.
Issue Date:2012-05-22
Rights Information:Copyright 2012 Nicholas Hausman
Date Available in IDEALS:2012-05-22
Date Deposited:2012-05

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