title: Resistance to PPO-inhibiting herbicide in Palmer amaranth from Arkansas.
abstract: BACKGROUND
  The widespread occurrence of ALS inhibitor- and glyphosate-resistant Amaranthus palmeri has led to increasing use of protoporphyrinogen oxidase (PPO)-inhibiting herbicides in cotton and soybean. Studies were conducted to confirm resistance to fomesafen (a PPO inhibitor), determine the resistance frequency, examine the resistance profile to other foliar-applied herbicides and investigate the resistance mechanism of resistant plants in a population collected in 2011 (AR11-LAW B) and its progenies from two cycles of fomesafen selection (C1 and C2).
  
  
  RESULTS
  The frequency of fomesafen-resistant plants increased from 5% in the original AR11-LAW-B to 17% in the C2 population. The amounts of fomesafen that caused 50% growth reduction were 6-, 13- and 21-fold greater in AR11-LAW-B, C1 and C2 populations, respectively, than in the sensitive ecotype. The AR11-LAW-B population was sensitive to atrazine, dicamba, glufosinate, glyphosate and mesotrione but resistant to ALS-inhibiting herbicides pyrithiobac and trifloxysulfuron. Fomesafen survivors from C1 and C2 populations tested positive for the PPO glycine 210 deletion previously reported in waterhemp (Amaranthus tuberculatus).
  
  
  CONCLUSIONS
  These studies confirmed that Palmer amaranth in Arkansas has evolved resistance to foliar-applied PPO-inhibiting herbicide.
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA.
authors.forename: Reiofeli A
authors.initials: RA
authors.lastname: Salas
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA.
authors.forename: Nilda R
authors.initials: NR
authors.lastname: Burgos
authors.affiliation: Department of Crop Sciences, University of Illinois, Urbana, IL, USA.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Tranel
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Singh
authors.affiliation: Syngenta Crop Protection Inc., Greensboro, NC, USA.
authors.forename: Les
authors.initials: L
authors.lastname: Glasgow
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Scott
authors.affiliation: Cotton Inc., Cary, NC, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Nichols
mesh_terms: D027721:Amaranthus / Q000187:drug effects*; D001131:Arkansas; D001549:Benzamides / Q000494:pharmacology*; D053209:Herbicide Resistance; D006540:Herbicides / Q000494:pharmacology*; D057685:Plant Weeds / Q000187:drug effects; D050768:Protoporphyrinogen Oxidase / Q000037:antagonists & inhibitors*; D012641:Selection, Genetic
chemical_list: D001549:Benzamides; D006540:Herbicides; D050768:Protoporphyrinogen Oxidase; C088563:fomesafen
keywords: ALS inhibitors; Amaranthus palmeri; diphenyl ether resistance; fomesafen; multiple resistance; resistance evolution
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