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1 November 2017 Frequency of Gly-210 Deletion Mutation among Protoporphyrinogen Oxidase Inhibitor-Resistant Palmer Amaranth (Amaranthus palmeri) Populations
Reiofeli A. Salas-Perez, Nilda R. Burgos, Gulab Rangani, Shilpa Singh, Joao Paulo Refatti, Leonard Piveta, Patrick J. Tranel, Andy Mauromoustakos, Robert C. Scott
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Abstract

The widespread occurrence of Palmer amaranth resistant to acetolactate synthase inhibitors and/or glyphosate led to the increased use of protoporphyrinogen oxidase (PPO)-inhibiting herbicides. This research aimed to: (1) evaluate the efficacy of foliar-applied fomesafen to Palmer amaranth, (2) evaluate cross-resistance to foliar PPO inhibitors and efficacy of foliar herbicides with different mechanisms of action, (3) survey the occurrence of the PPO Gly-210 deletion mutation among PPO inhibitor-resistant Palmer amaranth, (4) identify other PPO target-site mutations in resistant individuals, and (5) determine the resistance level in resistant accessions with or without the PPO Gly-210 deletion. Seedlings were sprayed with fomesafen (263 g ai ha-1), dicamba (280 g ai ha-1), glyphosate (870 g ai ha-1), glufosinate (549 g ai ha-1), and trifloxysulfuron (7.84 g ai ha-1). Selected fomesafen-resistant accessions were sprayed with other foliar-applied PPO herbicides. Mortality and injury were evaluated 21 d after treatment (DAT). The PPX2L gene of resistant and susceptible plants from a selected accession was sequenced. The majority (70%) of samples from putative PPO-resistant populations in 2015 were confirmed resistant to foliar-applied fomesafen. The efficacy of other foliar PPO herbicides on fomesafen-resistant accessions was saflufenacil > acifluorfen = flumioxazin > carfentrazone = lactofen > pyraflufen-ethyl > fomesafen > fluthiacet-methyl. With small seedlings, cross-resistance occurred with all foliar-applied PPO herbicides except saflufenacil (i.e., 25% with acifluorfen, 42% with flumioxazin). Thirty-two percent of PPO-resistant accessions were multiple resistant to glyphosate and trifloxysulfuron. Resistance to PPO herbicides in Palmer amaranth occurred in at least 13 counties in Arkansas. Of 316 fomesafen survivors tested, 55% carried the PPO Gly-210 deletion reported previously in common waterhemp. The PPO gene (PPX2L) in one accession (15CRI-B), which did not encode the Gly-210 deletion, encoded an Arg-128-Gly substitution. The 50% growth reduction values for fomesafen in accessions with Gly-210 deletion were 8- to 15-fold higher than that of a susceptible population, and 3- to 10-fold higher in accessions without the Gly-210 deletion.

Nomenclature: Acifluorfen; carfentrazone; dicamba; flumioxazin; fluthiacet-methyl; fomesafen; lactofen; glufosinate; glyphosate; pyraflufen-ethyl; saflufenacil; trifloxysulfuron; common waterhemp, Amaranthus rudis Sauer, AMATA; Palmer amaranth, Amaranthus palmeri S. Wats, AMAPA.

© Weed Science Society of America, 2017
Reiofeli A. Salas-Perez, Nilda R. Burgos, Gulab Rangani, Shilpa Singh, Joao Paulo Refatti, Leonard Piveta, Patrick J. Tranel, Andy Mauromoustakos, and Robert C. Scott "Frequency of Gly-210 Deletion Mutation among Protoporphyrinogen Oxidase Inhibitor-Resistant Palmer Amaranth (Amaranthus palmeri) Populations," Weed Science 65(6), 718-731, (1 November 2017). https://doi.org/10.1017/wsc.2017.41
Received: 14 February 2017; Accepted: 1 June 2017; Published: 1 November 2017
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