HRAC GROUP 2 (LEGACY B) RESISTANT RICE FLATSEDGE
(Cyperus iria)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

Brazil, Rio Grande do Sul

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INTRODUCTION RICE FLATSEDGE Rice Flatsedge (Cyperus iria) is a monocot weed in the Cyperaceae family.  In Brazil this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2014 and infests Rice.   Group 2 (Legacy B) herbicides are known as Inhibition of Acetolactate Synthase (Inhibition of Acetolactate Synthase ).  Research has shown that these particular biotypes are resistant to bispyribac-sodium, imazapic, imazethapyr, penoxsulam, and pyrazosulfuron-ethyl and they may be cross-resistant to other Group 2 (Legacy B) herbicides. The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

QUIK STATS (last updated Jul 04, 2016 ) Common Name Rice Flatsedge Species Cyperus iria Group Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B) Herbicides bispyribac-sodium, imazapic, imazethapyr, penoxsulam, and pyrazosulfuron-ethyl Location Brazil, Rio Grande do Sul Year 2014 Situation(s) Rice Contributors - (Alphabetically) Diego Martins Chiapinotto, and Carlos Eduardo Schaedler  Edit this Case  |  Add New Case of Resistance  |  Add Note

ACADEMIC ASPECTS Confirmation Tests Field, Greenhouse, and Laboratory trials comparing a known susceptible Rice Flatsedge biotype with this Rice Flatsedge biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.   Genetics Genetic studies on HRAC Group 2 resistant Rice Flatsedge have not been reported to the site.  There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature   Mechanism of Resistance The mechanism of resistance for this biotype is either unknown or has not been entered in the database.  If you know anything about the mechanism of resistance for this biotype then please update the database.   Relative Fitness There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes.  If you have any information pertaining to the fitness of Group 2 (Legacy B) resistant Rice Flatsedge from Brazil please update the database.   Edit Case  |  Add Note  |  Add Article  |  Add New Case  |  Help

CONTRIBUTING WEED SCIENTISTS DIEGO MARTINS CHIAPINOTTO Undergrad Student - Scholarship Of Scientific Initiation Universidade Federal do Pampa Weed Science (Grupo de Herbologia Pampa) Street Luiz Joaquim de Sá Britto Itaqui, 97650-000, Rio Grande do Sul Brazil Email Diego Martins Chiapinotto CARLOS EDUARDO SCHAEDLER Assistant Professor Universidade Federal do Pampa Weed Science and Crop (Grupo de Herbologia Pampa) Promorar Itaqui, 97650-000, Rio Grande do Sul Brazil Email Carlos Eduardo Schaedler

ACKNOWLEDGEMENTS The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Brazil have been instrumental in providing you this information. Particular thanks is given to Diego Martins Chiapinotto, and Carlos Eduardo Schaedler for providing detailed information.

Herbicide Resistant Rice Flatsedge Globally (Cyperus iria) Herbicide Resistant Rice Flatsedge Globally (Cyperus iria) Drag a column header and drop it here to group by that column Herbicide Resistant Rice Flatsedge Globally (Cyperus iria) # Country Country StateName FirstYear Situation Active Ingredients CountryID Site of Action WeedID Species CommonName ResistID 1 Brazil Brazil   2014 Rice bispyribac-sodium, imazapic, imazethapyr, penoxsulam, and pyrazosulfuron-ethyl 5 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B) 266 Cyperus iria Rice Flatsedge 13040 2 United States (Arkansas) United States Arkansas 2010 Rice bispyribac-sodium, halosulfuron-methyl, imazamox, imazethapyr, and penoxsulam 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B) 266 Cyperus iria Rice Flatsedge 5560 3 United States (Louisiana) United States Louisiana 2013 Rice halosulfuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B) 266 Cyperus iria Rice Flatsedge 7785 4 Venezuela Venezuela   2015 Rice pyrazosulfuron-ethyl 80 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B) 266 Cyperus iria Rice Flatsedge 11015

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Riar, D. S., P. Tehranchian, J. K. Norsworthy, V. Nandula, S. McElroy, V. Srivastava, S. Chen, J. A. Bond, and R. C. Scott. 2015. Acetolactate synthase–inhibiting, herbicide-​resistant Rice ​flatsedge (Cyperus iria): ​cross-​resistance and ​molecular ​mechanism of resistance.. Weed Science 63 : 748 - 757.

Overuse of acetolactate synthase (ALS)–inhibiting herbicides in rice has led to the evolution of halosulfuron-resistant rice flatsedge in Arkansas and Mississippi. Resistant accessions were cross-resistant to labeled field rates of ALS-inhibiting herbicides from four different families, in comparison to a susceptible (SUS) biotype. Resistance index of Arkansas and Mississippi accessions based on an R/S ratio of the lethal dose required for 50% plant mortality (LD₅₀) to bispyribac-sodium, halosulfuron, imazamox, and penoxsulam was ≥ 21-fold. Control of Arkansas, Mississippi, and SUS accessions with labeled field rates of 2,4-D, bentazon, and propanil was ≥ 93%. An enzyme assay revealed that an R/S ratio for 50% inhibition (I₅₀) of ALS for halosulfuron was 2,600 and 200 in Arkansas and Mississippi, respectively. Malathion studies did not reveal enhanced herbicide metabolism in resistant plants. The ALS enzyme assay and cross-resistance studies point toward altered a target site as the potential mechanism of resistance. Trp₅₇₄–Leu amino acid substitution within the ALS gene was found in both Arkansas and Mississippi rice flatsedge accessions using the Illumina HiSeq platform, which corresponds to the mechanism of resistance found in many weed species. Field-rate applications of 2,4-D, bentazon, and propanil can be used to control these ALS-resistant rice flatsedge accessions..

Lanclos, D. Y. ; Webster, E. P. ; Zhang, W.. 2002. Glufosinate tank-mix combinations in glufosinate-resistant rice (Oryza sativa). Weed Technology 16 : 659 - 663.

At 14 days after treatment (DAT), glufosinate at 0.42 kg ai/ha controlled barnyard grass (Echinochloa crus-galli) and broadleaf signalgrass (Brachiaria platyphylla) 85 and 86%, respectively, in Louisiana, USA, during 1998 and 1999. Antagonism occurred for barnyard grass control with all mixtures of glufosinate at 0.42 kg/ha. At 14 DAT, no herbicide was superior to glufosinate at either rate when applied in mixture for the control of broadleaf signalgrass. Rice flatsedge (Cyperus iria) control 7 DAT was 68 and 82% with glufosinate at 0.42 and 0.84 kg/ha alone, respectively. The addition of propanil and triclopyr enhanced rice flatsedge control over that with glufosinate alone at 0.42 or 0.84 kg/ha. At 7 DAT, all herbicide mixtures increased spreading dayflower (Commelina diffusa) control compared with a single treatment of glufosinate at 0.42 kg/ha. By 28 DAT, spreading dayflower control was less than 80% with all treatments. Rice (cultivars BNGL HC-11 and BNGL-62) injury was less than 15% with all treatments..

Burgos, N. R. ; Anders, M. ; Oliver, L. R. ; Wheeler, C. C. ; Payne, S. ; Mobley, M. S.. 2000. Weed shift in cropping systems involving transgenic cultivars. Research Series - Arkansas Agricultural Experiment Station : 60 - 65.

The adoption of herbicide-resistant crops may foster the continuous use or multiple applications of one herbicide and may favour the proliferation of weed species that are more difficult to control. A study was initiated in 1999 at the Rice Research and Extension Centner, Stuttgart, Germany, to assess the change in weed composition in response to a weed control program for herbicide-resistant crops and various crop rotation schemes. Glufosinate-resistant or Liberty Link (LL) cultivars of rice and soyabean were used. Dominant weed species, before postemergence herbicide application, were Sida spinosa (prickly sida), Echinochloa crus-galli (barnyardgrass), Cyperus iria (rice flatsedge), Sesbania exaltata (hemp sesbania), Amaranthus palmeri (Palmer amaranth), Mollugo verticillata (carpetweed), and Portulaca oleracea (common purslane). Visual ratings 50 days after planting showed >90% control of all weeds in nontransgenic rice. Glufosinate (Liberty) provided excellent weed control except for barnyardgrass in LL rice (74%). For LL soyabean, glufosinate did not provide sufficient control of prickly sida (65%) and had escapes of barnyardgrass and Palmer amaranth. The conventional herbicide program for soyabean provided excellent control of prickly sida (95%) but was poor on Palmer amaranth (39%). Differential weed tolerance to glufosinate was apparent. Nontransgenic rice yielded 5947 kg/ha; the transgenic rice yielded 14% less. There was no significant difference in yield between transgenic and nontransgenic soyabean..

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PERMISSION MUST BE OBTAINED FIRST if you intend to base a significant portion of a scientific paper on data derived from this site.
Cite this site as: Heap, I.  The International Survey of Herbicide Resistant Weeds.  Online.  Internet.  Tuesday, April 16, 2024 .  Available  www.weedscience.org
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