No fitness cost of glyphosate resistance endowed by massive EPSPS gene amplification in Amaranthus palmeri

Waterhemp is an increasingly problematic weed in the U.S. Midwest, having now evolved resistances to herbicides from six different site-of-action groups. Glyphosate-resistant waterhemp in the Midwest is especially concerning given the economic importance of glyphosate in corn and soybean production. Amplification of the target-site gene, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) was found to be the mechanism of glyphosate resistance in Palmer amaranth, a species closely related to waterhemp. Here, the relationship between glyphosate resistance and EPSPS gene amplification in waterhemp was investigated. Glyphosate dose response studies were performed at field sites with glyphosate-resistant waterhemp in Illinois, Kansas, Kentucky, Missouri, and Nebraska, and relative EPSPS copy number of survivors was determined via quantitative real-time polymerase chain reaction (qPCR). Waterhemp control increased with increasing glyphosate rate at all locations, but no population was completely controlled even at the highest rate (3,360 g ae ha−1). EPSPS gene amplification was present in plants from four of five locations (Illinois, Kansas, Missouri, and Nebraska) and the proportion of plants with elevated copy number was generally higher in survivors from glyphosate-treated plots than in plants from the untreated control plots. Copy number magnitude varied by site, but an overall trend of increasing copy number with increasing rate was observed in populations with gene amplification, suggesting that waterhemp plants with more EPSPS copies are more resistant. Survivors from the Kentucky population did not have elevated EPSPS copy number. Instead, resistance in this population was attributed to the EPSPS Pro106Ser mutation. Results herein show a quantitative relationship between glyphosate resistance and EPSPS gene amplification in some waterhemp populations, while highlighting that other mechanisms also confer glyphosate resistance in waterhemp.

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EPSPS Gene Amplification is Present in the Majority of Glyphosate-Resistant Illinois Waterhemp (Amaranthus tuberculatus) Populations

Weed Technology ◽

10.1614/wt-d-14-00064.1 ◽

2015 ◽

Vol 29 (1) ◽

pp. 48-55 ◽

Cited By ~ 31

Author(s):

Laura A. Chatham ◽

Chenxi Wu ◽

Chance W. Riggins ◽

Aaron G. Hager ◽

Bryan G. Young ◽

...

Keyword(s):

Gene Amplification ◽

High Throughput Screening ◽

Glyphosate Resistance ◽

The State ◽

Molecular Test ◽

Molecular Assay ◽

Epsps Gene ◽

Whole Plant ◽

Alternative Means ◽

Amaranthus Tuberculatus

With the frequency of glyphosate-resistant waterhemp increasing throughout the Midwest, the identification of resistant populations has become important for managing this species. However, high-throughput screening for glyphosate resistance in the greenhouse is tedious and inefficient. Research was conducted to document the occurrence of glyphosate-resistant waterhemp throughout the state of Illinois, and to determine whether a molecular assay for 5-enolypyruvyl-shikimate-3-phosphate synthase (EPSPS) gene amplification can be used as an alternative means to detect resistant populations. Populations throughout the state of Illinois were collected in 2010 and screened for glyphosate resistance using a whole-plant assay in a greenhouse, and survivors were examined for EPSPS gene amplification. Of 80 populations investigated, 22 were glyphosate resistant based on the greenhouse screen, and gene amplification was identified in 20 (91%) of the resistant populations. Although there are multiple mechanisms for glyphosate resistance in waterhemp, a molecular test for EPSPS gene amplification provides a rapid alternative for identification of glyphosate resistance in most populations.

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Involvement of facultative apomixis in inheritance of EPSPS gene amplification in glyphosate-resistant Amaranthus palmeri

Planta ◽

10.1007/s00425-013-1972-3 ◽

2013 ◽

Vol 239 (1) ◽

pp. 199-212 ◽

Cited By ~ 30

Author(s):

Daniela N. Ribeiro ◽

Zhiqiang Pan ◽

Stephen O. Duke ◽

Vijay K. Nandula ◽

Brian S. Baldwin ◽

...

Keyword(s):

Gene Amplification ◽

Amaranthus Palmeri ◽

Epsps Gene ◽

Facultative Apomixis

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Fitness Cost Associated With Enhanced EPSPS Gene Copy Number and Glyphosate Resistance in an Amaranthus tuberculatus Population

Frontiers in Plant Science ◽

10.3389/fpls.2021.651381 ◽

2021 ◽

Vol 12 ◽

Author(s):

Helen M. Cockerton ◽

Shiv S. Kaundun ◽

Lieselot Nguyen ◽

Sarah Jane Hutchings ◽

Richard P. Dale ◽

...

Keyword(s):

Interspecific Competition ◽

Gene Amplification ◽

Copy Number ◽

Gene Copy Number ◽

Glyphosate Resistance ◽

Gene Copy ◽

Competitive Response ◽

Trade Off ◽

Epsps Gene ◽

Amaranthus Tuberculatus

The evolution of resistance to pesticides in agricultural systems provides an opportunity to study the fitness costs and benefits of novel adaptive traits. Here, we studied a population of Amaranthus tuberculatus (common waterhemp), which has evolved resistance to glyphosate. The growth and fitness of seed families with contrasting levels of glyphosate resistance was assessed in the absence of glyphosate to determine their ability to compete for resources under intra- and interspecific competition. We identified a positive correlation between the level of glyphosate resistance and gene copy number for the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) glyphosate target, thus identifying gene amplification as the mechanism of resistance within the population. Resistant A. tuberculatus plants were found to have a lower competitive response when compared to the susceptible phenotypes with 2.76 glyphosate resistant plants being required to have an equal competitive effect as a single susceptible plant. A growth trade-off was associated with the gene amplification mechanism under intra-phenotypic competition where 20 extra gene copies were associated with a 26.5 % reduction in dry biomass. Interestingly, this growth trade-off was mitigated when assessed under interspecific competition from maize.

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The EccDNA Replicon: A Heritable, Extranuclear Vehicle That Enables Gene Amplification and Glyphosate Resistance in Amaranthus palmeri

The Plant Cell ◽

10.1105/tpc.20.00099 ◽

2020 ◽

Vol 32 (7) ◽

pp. 2132-2140 ◽

Cited By ~ 3

Author(s):

William T. Molin ◽

Allison Yaguchi ◽

Mark Blenner ◽

Christopher A. Saski

Keyword(s):

Gene Amplification ◽

Glyphosate Resistance ◽

Amaranthus Palmeri

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Faculty Opinions recommendation of The eccDNA Replicon: A Heritable, Extra-Nuclear Vehicle that Enables Gene Amplification and Glyphosate Resistance in Amaranthus palmeri.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.737817148.793574347 ◽

2020 ◽

Author(s):

Veena Veena

Keyword(s):

Gene Amplification ◽

Glyphosate Resistance ◽

Amaranthus Palmeri

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Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) in Nebraska: Confirmation, EPSPS Gene Amplification, and Response to POST Corn and Soybean Herbicides

Weed Technology ◽

10.1614/wt-d-16-00109.1 ◽

2017 ◽

Vol 31 (1) ◽

pp. 80-93 ◽

Cited By ~ 29

Author(s):

Parminder S. Chahal ◽

Vijay K. Varanasi ◽

Mithila Jugulam ◽

Amit J. Jhala

Keyword(s):

Gene Amplification ◽

Crop Production ◽

Acetolactate Synthase ◽

The United States ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Epsps Gene ◽

South Central ◽

Whole Plant ◽

Herbicide Programs

Palmer amaranth is the most problematic weed in agronomic crop production fields in the United States. A Palmer amaranth biotype was not controlled with sequential applications of glyphosate in glyphosate-resistant (GR) soybean production field in south-central Nebraska. The seeds of the putative GR Palmer amaranth biotype were collected in the fall of 2015. The objectives of this study were to (1) confirm GR Palmer amaranth and determine the level of resistance in a whole-plant dose-response bioassay, (2) determine the copy number of 5-enolpyruvylshikimate-3-phosphate (EPSPS) gene, the molecular target of glyphosate, and (3) evaluate the response of GR Palmer amaranth biotype to POST corn and soybean herbicides with different modes-of-action. Based on the effective dose required to control 90% of plants (ED90), the putative GR Palmer amaranth biotype was 37- to 40-fold resistant to glyphosate depending on the glyphosate-susceptible (GS) used as a baseline population.EPSPSgene amplification was present in the GR Palmer amaranth biotype with up to 32 to 105 EPSPS copies compared to the known GS biotypes. Response of GR Palmer amaranth to POST corn and soybean herbicides suggest reduced sensitivity to atrazine, hydroxyphenylpyruvate dioxygenase (HPPD)- (mesotrione, tembotrione, and topramezone), acetolactate synthase (ALS)- (halosulfuron-methyl), and protoporphyrinogen oxidase (PPO)- (carfentrazone and lactofen) inhibitors. GR Palmer amaranth was effectively controlled (>90%) with glufosinate applied at 593 g ai ha−1with ≥95% reduction in biomass. More research is needed to determine whether this biotype exhibits multiple resistant to other group of herbicides and evaluate herbicide programs for effective management in corn and soybean.

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