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QUIK STATS (last updated Mar 04, 2026 )
NOTES ABOUT THIS BIOTYPE
Cite this article: Lindell HC, Prostko EP, McElroy S, Patel JD, Blankenship JD, Grey TL, Basinger NT (2025). Evaluation of ALS-resistant yellow nutsedge (Cyperus esculentus) in Georgia peanut. Weed Sci. 73(e19), 1–7. doi: 10.1017/wsc.2024.87
Evaluation of ALS-resistant yellow nutsedge (Cyperus esculentus) in Georgia peanut Hannah C. Lindell1 , Eric P. Prostko2 , Scott McElroy3 , Jinesh D. Patel4 , Jason D. Blankenship5, Timothy L. Grey6 and Nicholas T. Basinger7
1Graduate Research Assistant, Department of Crop and Soil Sciences, University of Georgia, Athens, GA, USA; 2Professor and Extension Weed Specialist, Department of Crop and Soil Sciences, University of Georgia, Tifton, GA, USA; 3Professor in Weed Science and Turf, Department of Crop, Soil and Environmental Sciences, Auburn University, Auburn, AL, USA; 4Research Associate, Department of Crop, Soil and Environmental Sciences, Auburn University, Auburn, AL, USA; 5Former Randolph County Extension Agent, University of Georgia Cooperative Extension, Cuthbert, GA, USA; 6Professor, Department of Crop and Soil Sciences, University of Georgia, Tifton GA, USA and 7Associate Professor, Department of Crop and Soil Sciences, University of Georgia, Athens, GA, USA
Abstract
Accounting for 53% of U.S. peanuts (Arachis hypogaea L.), Georgia is the top peanut-producing state, with approximately 1.42 billion kg produced in 2023. Peanut producers often use the acetolactate synthase (ALS) imidazolinone herbicide imazapic, but reduced yellow nutsedge (CyperusesculentusL.)controlwasreportedinGeorgiapeanutsafter4yrofcontinuousimazapic use. This study aimed to determine the level of resistance (LD50, I50, and GR50) and potential cross-resistance for the suspected resistant population and to identify the associated genetic mutations conferring resistance. A susceptible biotype was treated with 0, 0.0088, 0.0175, 0.035, 0.07, 0.14, 0.28, and 0.56 kg ai ha−1, and a resistant biotype was sprayed with 0, 0.07, 0.14, 0.28, 0.56, 1.13, 2.26, and 4.5 kg ai ha−1 of imazapic. To determine whether the suspected resistant biotype was cross-resistant to halosulfuron-methyl, an ALS herbicide used to control Cyperus spp.,both biotypesweretreatedwith0,0.0117, 0.0233,0.0466,0.0933,0.187,0.373,and0.746gai ha−1 of halosulfuron-methyl. Plants were rated for injury at 7, 14, and 28 d after treatment (DAT), and aboveground biomass was harvested at 28 DAT. For imazapic, LD50 was 0.041 and 1.503 kg ai ha−1 and the GR50 was estimated to be 0.0128 and 1.853 kg ha−1 for Sus and Res biotypes, respectively, indicating 36- and 145-fold increase in resistance of the Res biotype for I50 and GR50, respectively. Both biotypes responded similarly to applications of halosulfuron-methyl, with biomass reduction at rates greater than 0.023 kg ai ha−1. Transcriptome profiles revealed a mutation in the target-site gene of the resistant biotype causing an amino acid substitution from alanine to valine at position 205 (Ala-205-Val). Growers should continue to rotate chemistries and implement integrated weed management approaches for control of C. esculentus, as the use of imazapic over consecutive years has led to resistance in C. esculentus.
ACADEMIC ASPECTS
CONTRIBUTING WEED SCIENTISTS
ACKNOWLEDGEMENTS
BACKGROUND: Yellow nutsedge is one of the most problematic sedges in Arkansas rice, requiring the frequent use of halosulfuron (sulfonylurea) for its control. In the summer of 2012, halosulfuron at 53 g ha−1 (labeled field rate) failed to control yellow nutsedge. The level of resistance to halosulfuron was determined in the putative resistant biotype, and its cross-resistance to other acetolactate synthase (ALS) inhibitors from four different herbicide families. ALS enzyme assays and analysis of the ALS gene were used to ascertain the resistance mechanism.
RESULTS: None of the resistant plants was killed by halosulfuron at a dose of 13 568 g ha−1 (256× the field dose), indicating a high level of resistance. Based on the whole-plant bioassay, the resistant biotype was not controlled by any of the ALS-inhibiting herbicides (imazamox, imazethapyr, penoxsulam, bispyribac, pyrithiobac-sodium, bensulfuron and halosulfuron) tested at the labeled field rate. The ALS enzyme from the resistant biotype was 2540 times less responsive to halosulfuron than the susceptible biotype, and a Trp574-to-Leu substitution was detected by ALS gene sequencing using the Illumina HiSeq.
CONCLUSION: The results suggest a target-site alteration as the mechanism of resistance in yellow nutsedge, which accounts for the cross-resistance to other ALS-inhibiting herbicide families.