Distribution of target site PPO-inhibiting herbicide resistance mutations in waterhemp and Palmer amaranth and association of epyrifenacil efficacy with PPX2 target site variants

During the 2019 growing season, seeds of Palmer amaranth and common waterhemp were collected from 141 and 133 agricultural sites, respectively, from across the southeastern and midwestern United States. These accessions were screened with a new protoporphyrinogen oxidase (PPO) inhibitor, epyrifenaci...

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Main Authors: Jacob Montgomery, Daljit Singh, Andrew Tyre, Jaishree Chittoor, Clifford Wollam, Brandi Chiapelli, John Pawlak, Chandrashekar Aradhya, Alejandro Perez-Jones
Format: Article
Language:English
Published: Cambridge University Press 2025-01-01
Series:Weed Technology
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Online Access:https://www.cambridge.org/core/product/identifier/S0890037X25000405/type/journal_article
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author Jacob Montgomery
Daljit Singh
Andrew Tyre
Jaishree Chittoor
Clifford Wollam
Brandi Chiapelli
John Pawlak
Chandrashekar Aradhya
Alejandro Perez-Jones
author_facet Jacob Montgomery
Daljit Singh
Andrew Tyre
Jaishree Chittoor
Clifford Wollam
Brandi Chiapelli
John Pawlak
Chandrashekar Aradhya
Alejandro Perez-Jones
author_sort Jacob Montgomery
collection DOAJ
description During the 2019 growing season, seeds of Palmer amaranth and common waterhemp were collected from 141 and 133 agricultural sites, respectively, from across the southeastern and midwestern United States. These accessions were screened with a new protoporphyrinogen oxidase (PPO) inhibitor, epyrifenacil, using a whole-plant bioassay at 20 g ai ha−1 in controlled environmental conditions to estimate its efficacy on these two agronomically important weeds. In addition, the coding sequence of the PPX2 gene was determined for plants from each accession through short-read sequencing of cDNA fragments amplified via polymerase chain reaction. Results showed that nearly all accessions were completely controlled by epyrifenacil, with average survival rates of less than 2% for both species. Target site resistance mutations toward PPO inhibitors were lower in Palmer amaranth (<20%) compared to waterhemp, with nearly half of all waterhemp samples (42%) possessing the ΔG210 allele, which is shown to cause high-level resistance to other commercially available PPO-inhibiting herbicides. Follow-up testing of accessions with high frequency (≥50%) of the ΔG210 allele of PPX2 compared the efficacy of epyrifenacil, saflufenacil, and saflufenacil + trifludimoxazin and showed that of the herbicides tested, epyrifenacil at 20 g ha−1 provided the best control, averaging 85% mortality across these accessions. Same-plant association study of molecular data and whole-plant assay correlated all detected variants of PPX2 with visual injury following epyrifenacil treatment and found that the ΔG210 mutation was associated with a reduction in relative efficacy of epyrifenacil in some accessions. All other known target site resistance mutations appeared to have no significant effect on epyrifenacil efficacy.
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spelling doaj-art-6aba7ecf2c1a443c91495ae34fae6a9c2025-08-20T03:58:40ZengCambridge University PressWeed Technology0890-037X1550-27402025-01-013910.1017/wet.2025.40Distribution of target site PPO-inhibiting herbicide resistance mutations in waterhemp and Palmer amaranth and association of epyrifenacil efficacy with PPX2 target site variantsJacob Montgomery0Daljit Singh1Andrew Tyre2Jaishree Chittoor3Clifford Wollam4Brandi Chiapelli5John Pawlak6Chandrashekar Aradhya7Alejandro Perez-Jones8https://orcid.org/0009-0002-3705-5331Ph.D Candidate, Department of Agricultural Biology, Colorado State University, Fort Collins, CO, USASr. Regulatory Affairs Manager, Crop Protection Regulatory Affairs, Bayer CropScience, Chesterfield, MO, USAResistance Modeller, Regulatory Affairs - Seeds and Traits, Bayer CropScience, Chesterfield, MO, USASr. Computational Biologist, Analytics and Data Science, Bayer CropScience, Chesterfield, MO, USASr. Computational Biologist, Analytics and Data Science, Bayer CropScience, Chesterfield, MO, USAScientist I, Genomics and Sequencing, Bayer CropScience, Chesterfield, MO, USAProduct Development Manager, Herbicides, Valent USA, Fresno, CA, USAHerbicide Resistance Management Lead, Regulatory Affairs - Seeds and Traits, BayerCrop Science, Chesterfield, MO, USAPrincipal Scientist, Controlled Environment Testing, Bayer CropScience, Chesterfield, MO, USADuring the 2019 growing season, seeds of Palmer amaranth and common waterhemp were collected from 141 and 133 agricultural sites, respectively, from across the southeastern and midwestern United States. These accessions were screened with a new protoporphyrinogen oxidase (PPO) inhibitor, epyrifenacil, using a whole-plant bioassay at 20 g ai ha−1 in controlled environmental conditions to estimate its efficacy on these two agronomically important weeds. In addition, the coding sequence of the PPX2 gene was determined for plants from each accession through short-read sequencing of cDNA fragments amplified via polymerase chain reaction. Results showed that nearly all accessions were completely controlled by epyrifenacil, with average survival rates of less than 2% for both species. Target site resistance mutations toward PPO inhibitors were lower in Palmer amaranth (<20%) compared to waterhemp, with nearly half of all waterhemp samples (42%) possessing the ΔG210 allele, which is shown to cause high-level resistance to other commercially available PPO-inhibiting herbicides. Follow-up testing of accessions with high frequency (≥50%) of the ΔG210 allele of PPX2 compared the efficacy of epyrifenacil, saflufenacil, and saflufenacil + trifludimoxazin and showed that of the herbicides tested, epyrifenacil at 20 g ha−1 provided the best control, averaging 85% mortality across these accessions. Same-plant association study of molecular data and whole-plant assay correlated all detected variants of PPX2 with visual injury following epyrifenacil treatment and found that the ΔG210 mutation was associated with a reduction in relative efficacy of epyrifenacil in some accessions. All other known target site resistance mutations appeared to have no significant effect on epyrifenacil efficacy.https://www.cambridge.org/core/product/identifier/S0890037X25000405/type/journal_articleEpyrifenacilPalmer amaranth Amaranthus palmeri S. Watson AMAPAcommon waterhemp Amaranthus tuberculatus (Moq) J.D. Sauer AMATASequencingherbicidePPOresistancesurvey
spellingShingle Jacob Montgomery
Daljit Singh
Andrew Tyre
Jaishree Chittoor
Clifford Wollam
Brandi Chiapelli
John Pawlak
Chandrashekar Aradhya
Alejandro Perez-Jones
Distribution of target site PPO-inhibiting herbicide resistance mutations in waterhemp and Palmer amaranth and association of epyrifenacil efficacy with PPX2 target site variants
Weed Technology
Epyrifenacil
Palmer amaranth
Amaranthus palmeri S. Watson AMAPA
common waterhemp
Amaranthus tuberculatus (Moq) J.D. Sauer AMATA
Sequencing
herbicide
PPO
resistance
survey
title Distribution of target site PPO-inhibiting herbicide resistance mutations in waterhemp and Palmer amaranth and association of epyrifenacil efficacy with PPX2 target site variants
title_full Distribution of target site PPO-inhibiting herbicide resistance mutations in waterhemp and Palmer amaranth and association of epyrifenacil efficacy with PPX2 target site variants
title_fullStr Distribution of target site PPO-inhibiting herbicide resistance mutations in waterhemp and Palmer amaranth and association of epyrifenacil efficacy with PPX2 target site variants
title_full_unstemmed Distribution of target site PPO-inhibiting herbicide resistance mutations in waterhemp and Palmer amaranth and association of epyrifenacil efficacy with PPX2 target site variants
title_short Distribution of target site PPO-inhibiting herbicide resistance mutations in waterhemp and Palmer amaranth and association of epyrifenacil efficacy with PPX2 target site variants
title_sort distribution of target site ppo inhibiting herbicide resistance mutations in waterhemp and palmer amaranth and association of epyrifenacil efficacy with ppx2 target site variants
topic Epyrifenacil
Palmer amaranth
Amaranthus palmeri S. Watson AMAPA
common waterhemp
Amaranthus tuberculatus (Moq) J.D. Sauer AMATA
Sequencing
herbicide
PPO
resistance
survey
url https://www.cambridge.org/core/product/identifier/S0890037X25000405/type/journal_article
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