Exploring the mechanisms of Palmer amaranth resistance to protoporphyrinogen oxidase-inhibitor herbicides, dynamics of gender, and management strategies
type: CreativeWork
description: Palmer amaranth (Amaranthus palmeri S. Watson) is a C4, summer annual, dioecious broadleaf plant and is the most economically damaging and troublesome weed in major crops grown in the USA. Currently, Palmer amaranth is reported to have evolved resistance to nine herbicide sites of action, raising the importance of integrating multiple weed management strategies. The objectives of this dissertation were to 1) quantify the relative level and characterize target- and non-target-site mechanism(s) conferring resistance to protoporphyrinogen oxidase (PPO)-inhibitors (e.g., lactofen and fomesafen) in a multiple-resistant Palmer amaranth population from Kansas (KCTR), 2) compare female and male life cycles of Palmer amaranth to identify differences that could be incorporated into management decisions, and 3) understand the interactions between pre-emergence (PRE) herbicides in the absence or presence of cover crops dead (terminated two weeks prior to planting) or “green” (terminated at the planting day) as well as impacts on soybean yield. Dose-response assay confirmed resistance to PPO-inhibitors in KCTR Palmer amaranth, which was 12.7- to 34.5-times less sensitive to these herbicides compared to a known susceptible Palmer amaranth. Analysis of the PPO2 gene (the molecular target of PPO-inhibitors) revealed no known mutations nor increased expression of this gene conferring resistance in KCTR. High-pressure liquid chromatography analyses suggested more metabolism of fomesafen at 48, 72 and 96 hours after treatment in KCTR compared to susceptible plants. Additionally, in the presence of malathion, a cytochrome P450-inhibitor, there was increased sensitivity of KCTR to lactofen, suggesting that the KCTR plants metabolized PPO-inhibitors via P450 activity. Interestingly, PRE applications of the PPO-inhibitors fomesafen, flumioxazin, saflufenacil, and sulfentrazone, resulted in complete control of KCTR. A growth chamber assay of comparative emergence of female and male Palmer …
abstract: Palmer amaranth (Amaranthus palmeri S. Watson) is a C4, summer annual, dioecious broadleaf plant and is the most economically damaging and troublesome weed in major crops grown in the USA. Currently, Palmer amaranth is reported to have evolved resistance to nine herbicide sites of action, raising the importance of integrating multiple weed management strategies. The objectives of this dissertation were to 1) quantify the relative level and characterize target- and non-target-site mechanism(s) conferring resistance to protoporphyrinogen oxidase (PPO)-inhibitors (e.g., lactofen and fomesafen) in a multiple-resistant Palmer amaranth population from Kansas (KCTR), 2) compare female and male life cycles of Palmer amaranth to identify differences that could be incorporated into management decisions, and 3) understand the interactions between pre-emergence (PRE) herbicides in the absence or presence of cover crops dead (terminated two weeks prior to planting) or “green” (terminated at the planting day) as well as impacts on soybean yield. Dose-response assay confirmed resistance to PPO-inhibitors in KCTR Palmer amaranth, which was 12.7- to 34.5-times less sensitive to these herbicides compared to a known susceptible Palmer amaranth. Analysis of the PPO2 gene (the molecular target of PPO-inhibitors) revealed no known mutations nor increased expression of this gene conferring resistance in KCTR. High-pressure liquid chromatography analyses suggested more metabolism of fomesafen at 48, 72 and 96 hours after treatment in KCTR compared to susceptible plants. Additionally, in the presence of malathion, a cytochrome P450-inhibitor, there was increased sensitivity of KCTR to lactofen, suggesting that the KCTR plants metabolized PPO-inhibitors via P450 activity. Interestingly, PRE applications of the PPO-inhibitors fomesafen, flumioxazin, saflufenacil, and sulfentrazone, resulted in complete control of KCTR. A growth chamber assay of comparative emergence of female and male Palmer …
author: Borgato, Ednaldo Alexandre
language: en_US
keywords: Amaranthus palmeri S. Watson, Cover crop, Cytochrome P450, Development, Emergence, Phenology, Pre-emergence
license: http://rightsstatements.org/vocab/InC/1.0/
date published: 2023
date modified: 2026-07-27T20:01:26Z
provider: Kansas State University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Kansas State University

PropertyValue
property ID: Handle
value: https://hdl.handle.net/2097/42888