Amaranthus palmeri (carelessweed)
Amaranthus palmeri glomeratus
Common Names: Palmer's amaranth, Palmer amaranth, carelessweed
1. Defence by duplication: The relation between phenotypic glyphosate resistance and EPSPS gene copy number variation in Amaranthus palmeri.
Yakimowski SB, Teitel Z, Caruso CM
Molecular ecologyMol EcolDefence by duplication: The relation between phenotypic glyphosate resistance and EPSPS gene copy number variation in Amaranthus palmeri.5328-534210.1111/mec.16231Gene copy number variation (CNV) has been increasingly associated with organismal responses to environmental stress, but we know little about the quantitative relation between CNV and phenotypic variation. In this study we quantify the relation between variation in EPSPS (5-enolpyruvylshikimate-3-phosphate synthase) copy number using digital drop PCR and variation in phenotypic glyphosate resistance in 22 populations of Amaranthus palmeri (Palmer Amaranth), a range-expanding agricultural weed. Overall, we detected a significant positive relation between population mean copy number and resistance. The majority of populations exhibited high glyphosate resistance yet maintained low-resistance individuals, resulting in bimodality in many populations. We also investigated threshold models for the relation between copy number and resistance, and found evidence for a threshold of ~15 EPSPS copies: there was a steep increase in resistance below the threshold, followed by a much shallower increase. Across 924 individuals, as copy number increased the range of variation in resistance decreased, yielding an increasing frequency of high phenotypic resistance individuals. Among populations we detected a decline in variation (s.d.) as mean phenotypic resistance increased from moderate to high, consistent with the prediction that as phenotypic resistance increases in populations, stabilizing selection decreases variation in the trait. Our study demonstrates that populations of A. palmeri can harbour wide variation in EPSPS copy number and phenotypic glyphosate resistance, reflecting the history of, and template for future, resistance evolution.© 2021 John Wiley & Sons Ltd.YakimowskiSarah BSBhttps://orcid.org/0000-0002-2465-5314Department of Biology, Queen's University, Kingston, Ontario, Canada.TeitelZacharyZhttps://orcid.org/0000-0002-6163-810XDepartment of Integrative Biology, University of Guelph, Guelph, Ontario, Canada.CarusoChristina MCMhttps://orcid.org/0000-0001-7069-9572Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada.engNatural Sciences and Engineering Research Council of CanadaJournal Article20211101EnglandMol Ecol92144780962-1083IMAmaranthus palmericopy number variation (CNV)digital droplet PCRgene duplicationglyphosate resistancetarget and nontarget site loci20210817202103222021090820211019602021101960202110181730ppublish3466247910.1111/mec.16231REFERENCES, 2021
2. Investigating the origins and evolution of a glyphosate-resistant weed invasion in South America.
Gaines TA, Slavov GT, Hughes D, Küpper A, Sparks CD, Oliva J, Vila-Aiub MM, Garcia MA, Merotto A, Neve P
Molecular ecologyMol EcolInvestigating the origins and evolution of a glyphosate-resistant weed invasion in South America.5360-537210.1111/mec.16221The global invasion, and subsequent spread and evolution of weeds provides unique opportunities to address fundamental questions in evolutionary and invasion ecology. Amaranthus palmeri is a widespread glyphosate-resistant (GR) weed in the USA. Since 2015, GR populations of A. palmeri have been confirmed in South America, raising questions about introduction pathways and the importance of pre- vs. post-invasion evolution of GR traits. We used RAD-sequencing genotyping to characterize genetic structure of populations from Brazil, Argentina, Uruguay and the USA. We also quantified gene copy number of the glyphosate target, 5-enolpyruvyl-3-shikimate phosphate synthase (EPSPS), and the presence of an extrachromosomal circular DNA (eccDNA) replicon known to confer glyphosate resistance in USA populations. Populations in Brazil, Argentina and Uruguay were only weakly differentiated (pairwise FST ?0.043) in comparison to USA populations (mean pairwise FST =0.161, range =0.068-0.258), suggesting a single major invasion event. However, elevated EPSPS copy number and the EPSPS replicon were identified in all populations from Brazil and Uruguay, but only in a single Argentinean population. These observations are consistent with independent in situ evolution of glyphosate resistance in Argentina, followed by some limited recent migration of the eccDNA-based mechanism from Brazil to Argentina. Taken together, our results are consistent with an initial introduction of A. palmeri into South America sometime before the 1980s, and local evolution of GR in Argentina, followed by a secondary invasion of GR A. palmeri with the unique eccDNA-based mechanism from the USA into Brazil and Uruguay during the 2010s.© 2021 John Wiley & Sons Ltd.GainesTodd ATAhttps://orcid.org/0000-0003-1485-7665Department of Agricultural Biology, Colorado State University, Fort Collins, Colorado, USA.SlavovGancho TGThttps://orcid.org/0000-0001-8565-9098Rothamsted Research, West Common, Harpenden, Hertfordshire, UK.Scion, Rotorua, New Zealand.HughesDavidDRothamsted Research, West Common, Harpenden, Hertfordshire, UK.KüpperAnitaADepartment of Agricultural Biology, Colorado State University, Fort Collins, Colorado, USA.Crop Science Division, Weed Control, Bayer AG, Frankfurt am Main, Germany.SparksCrystal DCDhttps://orcid.org/0000-0002-6674-8447Department of Agricultural Biology, Colorado State University, Fort Collins, Colorado, USA.OlivaJulianJProtección Vegetal-FCA, Universidad Católica de Córdoba (UCC), Córdoba, Argentina.Vila-AiubMartin MMMhttps://orcid.org/0000-0003-2118-290XIFEVA - CONICET - Faculty of Agronomy, Department of Ecology, University of Buenos Aires (UBA), Buenos Aires, Argentina.GarciaM AlejandroMAInstituto Nacional de Investigación Agropecuaria (INIA), Estación Experimental INIA La Estanzuela, Colonia, Uruguay.MerottoAldoAJrDepartment of Crop Science, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.NevePaulPhttps://orcid.org/0000-0002-3136-5286Rothamsted Research, West Common, Harpenden, Hertfordshire, UK.Plant & Environmental Sciences Department, University of Copenhagen, Tåstrup, Denmark.engBB/N022319/1BB_Biotechnology and Biological Sciences Research CouncilUnited KingdomBBS/OS/CP/000001BB_Biotechnology and Biological Sciences Research CouncilUnited KingdomJournal Article20211102EnglandMol Ecol92144780962-1083IMAmaranthus palmeriPalmer amaranthRAD-seqherbicide resistancepopulation genomics2021080420201102202109152021101360202110136020211012137ppublish3463717410.1111/mec.16221REFERENCES, 2021
3. A122S, A205V, D376E, W574L and S653N substitutions in acetolactate synthase (ALS) from Amaranthus palmeri show different functional impacts on herbicide resistance.
Palmieri VE, Alvarez CE, Permingeat HR, Perotti VE
Pest management sciencePest Manag SciA122S, A205V, D376E, W574L and S653N substitutions in acetolactate synthase (ALS) from Amaranthus palmeri show different functional impacts on herbicide resistance.10.1002/ps.6688Amaranthus palmeri S. Watson, a problematic weed infesting summer crops in Argentina, has developed multiple herbicide resistance. Resistance to acetolactate synthase (ALS)-inhibiting herbicides is particularly common, with high-level resistance mostly caused by different mutations in the ALS enzyme. Six versions of the enzyme were identified from a resistant A. palmeri population, carrying substitutions D376E, A205V, A122S, A282D, W574L and S653N. This work aims to provide a comparative analysis of these mutants and the wild-type (WT) enzyme to fully understand the herbicide resistance. Thus, all the versions of the ALS gene from A. palmeri were heterologously expressed and purified to evaluate their kinetics and inhibitory response against imazethapyr, diclosulam, chlorimuron-ethyl, flucarbazone-sodium and bispyribac-sodium.A decrease in catalytic efficiency was detected in the A205V, A122S-A282D, W574L and S653N ApALS enzymes, whereas only A205V and W574L substitutions also produced a decrease in the substrate affinity. In vitro ALS inhibition assays confirmed cross-resistance to almost all the herbicides tested, with the exception of A282D ApALS, which was as susceptible as WT ApALS. Moreover, the results confirmed that the novel substitution A122S provides cross-resistance to at least one herbicide within each of the five families of ALS inhibitors, and this property could be explained by a lower number of hydrophobic interactions between the herbicides and the mutant enzyme.This is the first report to compare various mutations in vitro from A. palmeri ALS. Our data contribute to understanding the impacts of herbicide resistance in this species.© 2021 Society of Chemical Industry.PalmieriValeria EVEInstituto de Investigaciones en Ciencias Agrarias de Rosario (IICAR-CONICET-UNR), Universidad Nacional de Rosario, Campo Experimental Villarino, Zavalla, Argentina.AlvarezClarisa ECECentro de Estudios Fotosintéticos y Bioquímicos, Universidad Nacional de Rosario, Rosario, Argentina.PermingeatHugo RHRhttps://orcid.org/0000-0002-2029-7097Instituto de Investigaciones en Ciencias Agrarias de Rosario (IICAR-CONICET-UNR), Universidad Nacional de Rosario, Campo Experimental Villarino, Zavalla, Argentina.Laboratorio de Biología Molecular, Universidad Nacional de Rosario, Campo Experimental Villarino, Zavalla, Argentina.PerottiValeria EVEhttps://orcid.org/0000-0003-1147-9902Laboratorio de Biología Molecular, Universidad Nacional de Rosario, Campo Experimental Villarino, Zavalla, Argentina.engAgencia Nacional de Promoción Científica y TecnológicaSECTEI- Santa Fe ProvinceJournal Article20211025EnglandPest Manag Sci1008987441526-498XIMA122S substitutionALS-inhibiting herbicidesAmaranthus palmeriacetolactate synthase2021081920211025202110266020211026602021102575aheadofprint3469363710.1002/ps.6688REFERENCES, 2021
4. Biochemical Basis for the Time-of-Day Effect on Glufosinate Efficacy against Amaranthus palmeri.
Takano HK, Dayan FE
Plants (Basel, Switzerland), 2021
5. Understanding Resistance Mechanisms to Trifluralin in an Arkansas Palmer Amaranth Population.
González-Torralva F, Norsworthy JK
6. Can new herbicide discovery allow weed management to outpace resistance evolution?
Gaines TA, Busi R, Küpper A
Pest management sciencePest Manag SciCan new herbicide discovery allow weed management to outpace resistance evolution?3036-304110.1002/ps.6457While herbicides are the most effective and widely adopted weed management approach, the evolution of multiple herbicide resistance in damaging weed species threatens the yield and profitability of many crops. Weeds accumulate multiple resistance mechanisms through sequential selection and/or gene flow, with long-range and international transport of herbicide-resistant weeds proving to be a serious issue. Metabolic resistance mechanisms can confer resistance across multiple sites of action and even to herbicides not yet discovered. When a new site of action herbicide is introduced to control a key driver weed, it likely will be one of very few effective available herbicide options for that weed in a specific crop due to the continuous use of herbicides over the years and the resulting accumulation of resistance mechanisms, placing it at even higher risk to be rapidly lost to resistance due to the high selection pressure it will experience. The number of available, effective herbicides for certain driver weeds is decreasing over time because the rate of resistance evolution is faster than the rate of new herbicide discovery. Effective monitoring for species movement and diagnostics for resistance should be deployed to rapidly identify emerging resistance to any new site of action. While innovation in herbicide discovery is urgently needed to combat the pressing issue of resistance in weeds, the rate of selection for herbicide resistance in weeds must be slowed through changes in the patterns of how herbicides are used. © 2021 Society of Chemical Industry. © 2021 Society of Chemical Industry.© 2021 Society of Chemical Industry.GainesTodd ATAhttps://orcid.org/0000-0003-1485-7665Department of Agricultural Biology, Colorado State University, Fort Collins, CO, USA.BusiRobertoRhttps://orcid.org/0000-0002-9022-2111Australian Herbicide Resistance Initiative, School of Agriculture and Environment, University of Western Australia, Perth, WA, Australia.KüpperAnitaAhttps://orcid.org/0000-0001-5122-1514Bayer AG, Industriepark Höchst, Frankfurt am Main, Germany.engJournal Article20210520EnglandPest Manag Sci1008987441526-498X0HerbicidesIMCrops, AgriculturalgeneticsHerbicide ResistancegeneticsHerbicidespharmacologyPlant WeedsgeneticsWeed ControlAmaranthus palmeriLolium rigidumherbicide discoveryherbicide resistanceintegrated weed managementresistance evolution20210429202103032021050420215560202161660202154851ppublish3394296310.1002/ps.6457REFERENCES, 2021
7. Sex dimorphism in dioecious Palmer amaranth (Amaranthus palmeri) in response to water stress.
Mesgaran MB, Matzrafi M, Ohadi S
8. Recurrent Selection with Sub-Lethal Doses of Mesotrione Reduces Sensitivity in Amaranthus palmeri.
Norsworthy JK, Varanasi VK, Bagavathiannan M, Brabham C
Plants (Basel, Switzerland), 2021
9. Raman Spectroscopy Can Distinguish Glyphosate-Susceptible and -Resistant Palmer Amaranth (Amaranthus palmeri).
Singh V, Dou T, Krimmer M, Singh S, Humpal D, Payne WZ, Sanchez L, Voronine DV, Prosvirin A, Scully M, Kurouski D, Bagavathiannan M
Frontiers in plant science, 2021
10. Corrigendum: Predominance of Metabolic Resistance in a Six-Way-Resistant Palmer Amaranth (Amaranthus palmeri) Population.
Shyam C, Borgato EA, Peterson DE, Dille JA, Jugulam M
Frontiers in plant science, 2021