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Title:Characterization of a novel five-way-resistant population of waterhemp (Amaranthus tuberculatus)
Author(s):Evans, Cody Matthew
Advisor(s):Hager, Aaron G.
Department / Program:Crop Sciences
Discipline:Crop Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
4-hydroxyphenylpyruvate dioxygenase (HPPD)
Protoporphyrinogen oxidase (PPO)
Acetolactate synthase (ALS)
Photosystem II (PSII)
Amaranthus tuberculatus
Synthetic Auxin
5 Way Resistance
Abstract:Waterhemp [Amaranthus tuberculatus (Moq.) Sauer] is a dioecious summer annual species native to much of the Midwest. This species exhibits many intriguing characteristics including, but not limited to, obligate outcrossing that results in a high level of genetic diversity, prolific seed production, prolonged seedling emergence, and seed dormancy, that help it thrive in contemporary agricultural fields. Waterhemp has become one of the most significant challenges growers face with respect to weed control. In the last decade, the frequency of waterhemp populations resistant to herbicides encompassing multiple sites of action has increased, adding to the difficulty and cost of controlling this species. Waterhemp has been reported to be resistant to herbicides having the following sites of action: acetolactate synthase (ALS), 5-enolpyruvyl-shikimate-3-phosphate (EPSPS), protoporphyrinogen oxidase (PPO), TIR1 auxin receptor, Photosystem II (PSII), and 4-hydroxyphenylpyruvate dioxygenase (HPPD). In 2012, a grower reported the failure to control a waterhemp population in conventional white corn with topramezone, an HPPD inhibitor. Records indicate the field had been planted with conventional corn hybrids and glyphosate-resistant soybean varieties in an annual rotation. Additionally, the grower used a rotation of different herbicides including HPPD, PPO, ALS, and PSII inhibitors for weed control. Preliminary investigation and screening suggested that the population might be resistant to herbicides from five site-of-action groups. Chapter 1 of this thesis includes a literature review of HPPD, PPO, ALS, PSII, and auxin herbicides, known resistance mechanisms in weeds, and a section on waterhemp biology. Chapter 2 discusses the original greenhouse screenings of progeny created from seed collected from the grower’s field (designated Champaign County Resistant (CHR)). To quantify the magnitude of resistance, foliar dose response experiments were conducted with mesotrione, atrazine, and 2,4-D. Molecular assays were conducted to confirm PPO inhibitor and ALS inhibitor resistance. Chapter 3 contains information about field research conducted to determine foliar herbicide options to manage CHR in corn (Zea mays L.) and soybean (Glycine max (L.) Merr.). Results from these experiments indicate control of CHR exceeding 80% 21 days after treatment (DAT) was achieved with four foliar-applied herbicides: glyphosate, glufosinate, dicamba, and paraquat. Additional field research is presented in Chapter 4 describing CHR’s response to soil-applied herbicides used in corn and soybean. Results from this research demonstrate that few options provided residual control of CHR greater than 80% 28 DAT. Chapter 4 also includes a summary of experiments, as well as future implications of this research.
Issue Date:2016-07-21
Rights Information:Copyright 2016 Cody Evans
Date Available in IDEALS:2016-11-10
Date Deposited:2016-08

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