<b>HRAC Group 27</b> <font size='2'> (Legacy F2) </font> resistant Setaria adhaerens from Mexico

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 27 (LEGACY F2) RESISTANT BUR BRISTLEGRASS
(Setaria adhaerens)

Inhibition of Hydroxyphenyl Pyruvate Dioxygenase HRAC Group 27 (Legacy F2)

Mexico, Guanajuato, El Bajío region

INTRODUCTION		BUR BRISTLEGRASS
Bur Bristlegrass (Setaria adhaerens) is a monocot weed in the Poaceae family. In Mexico this weed first evolved resistance to Group 27 (Legacy F2) herbicides in 2020 and infests Corn (maize). Group 27 (Legacy F2) herbicides are known as Inhibition of Hydroxyphenyl Pyruvate Dioxygenase (Inhibition of Hydroxyphenyl Pyruvate Dioxygenase ). Research has shown that these particular biotypes are resistant to tembotrione and they may be cross-resistant to other Group 27 (Legacy F2) 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 May 21, 2026 )
Common Name	Bur Bristlegrass
Species	Setaria adhaerens
Group	Inhibition of Hydroxyphenyl Pyruvate Dioxygenase HRAC Group 27 (Legacy F2)
Herbicides	tembotrione
Location	Mexico, Guanajuato, El Bajío region
Year	2020
Situation(s)	Corn (maize)
Contributors - (Alphabetically)	Hugo Cruz-Hipólito, Rafael De Prado, and Ja Dominguez Valenzuela
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Bur Bristlegrass biotype with this Bur Bristlegrass 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 27 resistant Bur Bristlegrass 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 27 (Legacy F2) resistant Bur Bristlegrass from Mexico please update the database.

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CONTRIBUTING WEED SCIENTISTS

HUGO CRUZ-HIPÓLITO

Research Asociate Universidad De Córdoba Química Agrícola Y Edafología Campus Universitario De Rabanales Edif. C-3 3ª Planta Córdoba, 14002 Spain Email Hugo Cruz-Hipólito

RAFAEL DE PRADO

Research Asociate Universidad De Cordoba Qvimica Agricola Y Edafologa E T S Ingenieros Agronomos PO Box 119 Cordoba, E-14080, Andalusia Spain Email Rafael De Prado

JA DOMINGUEZ VALENZUELA

Phd Universidad Autónoma Chapingo Parasitología Agrícola Area De Malezas Departamento De Parasitología Agricola Texcoco, 56230, Andalusia Mexico Email Ja Dominguez Valenzuela

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Mexico have been instrumental in providing you this information. Particular thanks is given to Hugo Cruz-Hipólito, Rafael De Prado, and Ja Dominguez Valenzuela for providing detailed information.

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Herbicide Resistant Bur Bristlegrass Globally
(Setaria adhaerens)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Mexico

2020

Corn (maize)

tembotrione

Inhibition of Hydroxyphenyl Pyruvate Dioxygenase ( HRAC Group 27 (Legacy F2)

Literature about Similar Cases

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Prado, R. de ; Lopez-Martinez, N. ; Gonzalez-Gutierrez, J.. 2000. Identification of two mechanisms of atrazine resistance in Setaria faberi and Setaria viridis biotypes. Pesticide Biochemistry and Physiology 67 : 114 - 124.

The effects of atrazine and other triazine herbicides were compared on two biotypes of Setaria faberi and S. viridis that were not controlled by atrazine in maize fields in Spain. S. faberi and S. viridis biotypes from treated maize fields had no significant inhibition of photosynthetic activity following incubation with atrazine (100 µM). The R biotypes of S. faberi and S. viridis were 10.0 and 6.96 times less sensitive to atrazine than the S biotypes, respectively. Results from ED50, absorption and translocation, and fast fluorescence assays showed that S. faberi and S. viridis could have 2 mechanisms of resistance: a detoxification mechanism and a target site mutation in the R biotypes of both species. Hill reaction assays suggested that resistance was due to a mutation in the D1 protein. R and S biotypes detoxified atrazine to a similar extent, but R biotypes metabolized atrazine to conjugate atrazine faster than the S biotypes. Atrazine metabolism analysis was carried out with 5 species of Setaria. The hierarchy of tolerance level to atrazine was: S. verticillata = S. adherens [?S. adhaerens = S. verticilliata] > S. faberi = S. viridis >> S. glauca [S. pumila]. The R biotypes of S. faberi and S. viridis were cross-resistant to all the triazine herbicides used..

Giménez-Espinosa, R. ; Romera, E. ; Tena, M. ; Prado, R. de. 1996. Fate of atrazine in treated and pristine accessions of three Setaria species. Pesticide Biochemistry and Physiology 56 : 196 - 207.

Experiments were conducted to compare the effects of atrazine on Setaria adherens [S. adhaerens], S. glauca [S. pumila] and S. verticillata from populations not controlled by previous exposure to triazines and from populations without a history of exposure. Results of bioassays indicated that there was no difference in the susceptibility of the S. adherens and S. verticillata populations, but the S. glauca exposed population was 5 times less susceptible than the other species, while its unexposed population was 6 times more susceptible. No differences were found between populations in atrazine uptake or translocation. Chlorophyll fluorescence analysis of isolated plastids indicated that those from the exposed S. glauca population had less affinity for atrazine than those from the unexposed population. No differences were found between populations of the other species. The exposed S. glauca population was resistant to a wide range of triazines and photosystem II inhibitors, while both populations of the other 2 species showed resistance to chloro-s-triazines and conjugated >80% atrazine. Atrazine-specific glutathione transferase had a higher activity in S. verticillata than S. glauca..

Prado, R. de ; Romera, E. ; Menéndez, J. ; Tena, M.. 1992. Differential mechanism of resistance to atrazine in Setaria adhaerens and Setaria glauca.. Mededelingen van de Faculteit Landbouwwetenschappen, Universiteit Gent 57 : 1067 - 1074.

Setaria adhaerens and S. glauca [S. pumila] populations resistant to atrazine have become an important problem in maize in NE and S. Spain. In S. adhaerens the resistance to atrazine seems to be due to a detoxification mechanism by conjugation of the herbicide with glutathione, while in S. pumila it was associated with a lower affinity of the herbicide for the target site in D1 protein. This dual mechanism could explain the different rate of tolerance to the herbicide among the 2 species. While the tolerance to atrazine of S. adhaerens is a constitutive character, the mechanism of resistance in S. pumila has evolved after several years of continuous application of the herbicide..

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