Glyphosate-Resistant Kochia (Kochia scoparia) in Kansas: EPSPS Gene Copy Number in Relation to Resistance Levels

Weed Science ◽  
2015 ◽  
Vol 63 (3) ◽  
pp. 587-595 ◽  
Author(s):  
Amar S. Godar ◽  
Phillip W. Stahlman ◽  
Mithila Jugulam ◽  
J. Anita Dille
Keyword(s):  
Copy Number ◽  
Gene Copy Number ◽  
Acetolactate Synthase ◽  
Outdoor Environment ◽  
Gene Copy ◽  
Geographically Dispersed ◽  
Epsps Gene ◽  
Whole Plant ◽  
Outdoor Environments ◽  
Control Failure

Reports of kochia control failure with glyphosate in western Kansas increased dramatically in the years following confirmed presence of glyphosate-resistant (GR) populations in 2007. In this study, progeny from 8 of 16 geographically dispersed kochia populations in western Kansas (seed collected in 2010) were confirmed to be resistant to glyphosate by conducting whole-plant dose-response (in greenhouse and/or outdoor environments) and shikimate-accumulation assays. Additionally, the relationship between 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene copy number and glyphosate resistance levels was investigated. A known glyphosate-susceptible (GS) kochia population from Ellis County, Kansas was used for comparison in all studies. Based on the herbicide rate that caused 50% reduction in biomass compared to untreated control (GR50) values, the 8 GR kochia populations were 4 to 11 times more resistant to glyphosate compared to the GS population. The GR50values of kochia populations were 1.58 to 1.85 times higher under an outdoor environment compared to when grown in the greenhouse. Glyphosate-treated leaf discs of the GS kochia plants accumulated consistently higher amounts of shikimate than those of the GR plants. Additionally, the GR plants with higher levels of resistance to glyphosate had higher EPSPS : acetolactate synthase (ALS) relative gene copy number compared to those with low levels of resistance.

scholarly journals EPSPS Gene Copy Number and Whole-Plant Glyphosate Resistance Level in Kochia scoparia

PLoS ONE ◽  
2016 ◽  
Vol 11 (12) ◽  
pp. e0168295 ◽  
Author(s):  
Todd A. Gaines ◽  
Abigail L. Barker ◽  
Eric L. Patterson ◽  
Philip Westra ◽  
Eric P. Westra ◽  
...  
Keyword(s):  
Copy Number ◽  
Gene Copy Number ◽  
Glyphosate Resistance ◽  
Gene Copy ◽  
Kochia Scoparia ◽  
Resistance Level ◽  
Epsps Gene ◽  
Whole Plant

scholarly journals Effect of EPSPS Gene Copy Number and Glyphosate Selection on Fitness of Glyphosate-Resistant Bassia Scoparia in The Field

2021 ◽  
Author(s):  
Charlemagne Ajoc Lim ◽  
Prashant Jha ◽  
Vipan Kumar ◽  
Alan T. Dyer
Keyword(s):  
Sugar Beet ◽  
Seed Production ◽  
Great Plains ◽  
Copy Number ◽  
Gene Copy Number ◽  
Reproductive Traits ◽  
Gene Copy ◽  
Epsps Gene ◽  
Gene Copies

Abstract The widespread evolution of glyphosate-resistant (GR) Bassia scoparia in the U.S. Great Plains poses a serious threat to the long-term sustainability of GR sugar beet. Glyphosate resistance in B. scoparia is due to an increase in the EPSPS (5-enolpyruvyl-shikimate-3-phosphate) gene copy number. The variation in EPSPS gene copies among individuals from within a single GR B. scoparia population indicated a differential response to glyphosate selection. We tested the hypothesis of reduced GR B. scoparia fitness (reproductive traits) to increasing glyphosate rates (applied as single or sequential applications) potentially experienced within a GR sugar beet field. The variation in EPSPS gene copy number and total glyphosate rate (single or sequential applications) did not influence any of the reproductive traits of GR B. scoparia, except seed production. Sequential applications of glyphosate with a total rate of 2,214 g ae ha− 1 or higher prevented seed production in B. scoparia plants with 2–4 (low levels of resistance) and 5–6 (moderate levels of resistance) EPSPS gene copies. Timely sequential applications of glyphosate (full recommended rates) can potentially slow down the evolution of GR B. scoparia with low to moderate levels of resistance (2–6 EPSPS gene copies), but any survivors (highly-resistant individuals with ≥ 8 EPSPS gene copies) need to be mechanically removed before flowering from GR sugar beet fields. This research warrants the need to adopt ecologically based, multi-tactic strategies to reduce exposure of B. scoparia to glyphosate in GR sugar beet.

scholarly journals Prediction of glyphosate resistance level based on EPSPS gene copy number in Kochia scoparia

2016 ◽  
Author(s):  
Todd A. Gaines ◽  
Abigail L. Barker ◽  
Eric L. Patterson ◽  
Philip Westra ◽  
Eric P. Westra ◽  
...  
Keyword(s):  
Gene Duplication ◽  
Empirical Model ◽  
Copy Number ◽  
Gene Copy Number ◽  
Glyphosate Resistance ◽  
Gene Copy ◽  
Kochia Scoparia ◽  
Resistance Level ◽  
Epsps Gene ◽  
Fallow Systems

AbstractGlyphosate-resistant (GR) Kochia scoparia has evolved in dryland chemical fallow systems throughout North America and the mechanism involves 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene duplication. Sugarbeet fields in four states were surveyed for K. scoparia in 2013 and tested for glyphosate-resistance level and EPSPS gene copy number. Glyphosate resistance was confirmed in K. scoparia populations collected from sugarbeet fields in Colorado, Wyoming, and Nebraska. The GR samples all had increased EPSPS gene copy number, with median population values up to 11. An empirical model was developed to estimate the level of glyphosate-resistance in K. scoparia based on EPSPS gene copy number. The results suggested that glyphosate susceptibility can be accurately diagnosed using EPSPS gene copy number, and further increases in EPSPS gene copy number could increase resistance levels up to 8-fold relative to susceptible K. scoparia. These trends suggest that continued glyphosate selection pressure is selecting for higher EPSPS copy number and higher resistance levels in K. scoparia. By including multiple K. scoparia samples lacking EPSPS gene duplication, our empirical model provides a more realistic estimate of fold-resistance due to EPSPS gene copy number compared to methods that do not account for normal variation of herbicide response in susceptible biotypes.

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

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.

scholarly journals Effect of EPSPS gene copy number and glyphosate selection on fitness of glyphosate-resistant Bassia scoparia in the field

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Charlemagne Ajoc Lim ◽  
Prashant Jha ◽  
Vipan Kumar ◽  
Alan T. Dyer
Keyword(s):  
Sugar Beet ◽  
Seed Production ◽  
Great Plains ◽  
Copy Number ◽  
Gene Copy Number ◽  
Reproductive Traits ◽  
Gene Copy ◽  
Epsps Gene ◽  
Gene Copies

AbstractThe widespread evolution of glyphosate-resistant (GR) Bassia scoparia in the U.S. Great Plains poses a serious threat to the long-term sustainability of GR sugar beet. Glyphosate resistance in B. scoparia is due to an increase in the EPSPS (5-enolpyruvyl-shikimate-3-phosphate) gene copy number. The variation in EPSPS gene copies among individuals from within a single GR B. scoparia population indicated a differential response to glyphosate selection. With the continued use of glyphosate in GR sugar beet, the effect of increasing glyphosate rates (applied as single or sequential applications) on the fitness of GR B. scoparia individuals with variable EPSPS gene copies was tested under field conditions. The variation in EPSPS gene copy number and total glyphosate rate (single or sequential applications) did not influence any of the reproductive traits of GR B. scoparia, except seed production. Sequential applications of glyphosate with a total rate of 2214 g ae ha−1 or higher prevented seed production in B. scoparia plants with 2–4 (low levels of resistance) and 5–6 (moderate levels of resistance) EPSPS gene copies. Timely sequential applications of glyphosate (full recommended rates) can potentially slow down the evolution of GR B. scoparia with low to moderate levels of resistance (2–6 EPSPS gene copies), but any survivors (highly-resistant individuals with ≥ 8 EPSPS gene copies) need to be mechanically removed before flowering from GR sugar beet fields. This research warrants the need to adopt ecologically based, multi-tactic strategies to reduce exposure of B. scoparia to glyphosate in GR sugar beet.

Multiple Resistance to Glyphosate and Acetolactate Synthase Inhibitors in Palmer Amaranth (Amaranthus palmeri) Identified in Brazil

Weed Science ◽  
2017 ◽  
Vol 65 (3) ◽  
pp. 317-326 ◽  
Author(s):  
Anita Küpper ◽  
Ednaldo A. Borgato ◽  
Eric L. Patterson ◽  
Acácio Gonçalves Netto ◽  
Marcelo Nicolai ◽  
...  
Keyword(s):  
Copy Number ◽  
Management Practices ◽  
Gene Copy Number ◽  
Acetolactate Synthase ◽  
The United States ◽  
Palmer Amaranth ◽  
Brazilian Population ◽  
Gene Copy ◽  
Response Curves ◽  
Mato Grosso

Palmer amaranth is native to the United States, but was discovered in 2015 in Brazil. Palmer amaranth populations in Brazil were very difficult to control using glyphosate, which resulted in many changes to standard weed management practices. A genotyping assay was used to confirm that the population detected in Mato Grosso State, Brazil, was correctly identified as Palmer amaranth and that it was not tall waterhemp. Greenhouse dose–response curves and shikimate accumulation assays showed that the Brazilian population was highly resistant to glyphosate, with an LD50 value (3,982 g glyphosate ha−1) more than twice the typical use rates and very little shikimate accumulation at 1 mM glyphosate concentrations in a leaf-disk assay. The Brazilian population was also resistant to sulfonylurea and imidazolinone acetolactate synthase (ALS) inhibitor herbicides. The resistance mechanisms in the Brazilian population were identified as increasedEPSPSgene copy number for glyphosate resistance (between 50- and 179-fold relativeEPSPSgene copy number increase) and two different alleles for target-site mutations in theALSgene (W574L and S653N). These results confirm the introduction of Palmer amaranth to Brazil using a genetic marker for species identification, as well as resistance to glyphosate and ALS inhibitors.

scholarly journals No Impact of Increased EPSPS Gene Copy Number on Growth and Fecundity of Glyphosate-Resistant Kochia (Bassia scoparia)

Weed Science ◽  
2018 ◽  
Vol 67 (1) ◽  
pp. 22-28 ◽  
Author(s):  
O. Adewale Osipitan ◽  
J. Anita Dille
Keyword(s):  
Weed Management ◽  
Copy Number ◽  
Plant Biomass ◽  
Management Strategies ◽  
Gene Copy Number ◽  
Glyphosate Resistance ◽  
Gene Copy ◽  
Competitive Response ◽  
Epsps Gene

AbstractThe level of glyphosate resistance in kochia [Bassia scoparia(L.) A. J. Scott] was reported to be due to an increase in 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene copy number. A field study was conducted near Manhattan, KS, in 2014 and 2015 to evaluate the relationship between EPSPS gene copy number and growth and fecundity variables ofB. scopariaindividuals within suspected glyphosate-resistant (GR) populations from western Kansas. Initial assays of EPSPS gene copy and in vivo shikimate accumulation showed thatB. scopariapopulations from Finney (FN-R), Scott (SC-R), and Thomas (TH-R) counties were segregating for glyphosate resistance, with some individuals still being glyphosate susceptible (GS). A target-neighborhood competition approach was used to evaluate the competitive response of individual target plants with relatively low (classified as GS) and high (classified as GR) EPSPS gene copy number within the populations. There was no relationship observed between EPSPS gene copy number and vegetative or fecundity variables. There was no differential competitive response of target plant biomass to increasing neighbor density between individuals with low and high EPSPS gene copy number within each population. Lack of associated vegetative growth and fecundity cost to the increased EPSPS gene copy in the GRB. scopariaplants suggests that the plants are likely to persist in field populations, except when effective weed management strategies are adopted that would prevent their growth and seed production.

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