<b>HRAC Group 9</b> <font size='2'> (Legacy G) </font> resistant Aster squamatus from Mexico

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 9 (LEGACY G) RESISTANT SALTMARSH ASTER
(Aster squamatus)

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G)

Mexico

INTRODUCTION		SALTMARSH ASTER
Saltmarsh Aster (Aster squamatus) is a dicot weed in the Asteraceae family. In Mexico this weed first evolved resistance to Group 9 (Legacy G) herbicides in 2021 and infests Oranges. Group 9 (Legacy G) herbicides are known as Inhibition of Enolpyruvyl Shikimate Phosphate Synthase (Inhibition of EPSP synthase). Research has shown that these particular biotypes are resistant to glyphosate and they may be cross-resistant to other Group 9 (Legacy G) 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 Sep 27, 2021 )
Common Name	Saltmarsh Aster
Species	Aster squamatus
Group	Inhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G)
Herbicides	glyphosate
Location	Mexico
Year	2021
Situation(s)	Oranges
Contributors - (Alphabetically)	Hugo Cruz-Hipólito, Rafael De Prado, Ja Dominguez Valenzuela, Candelario Palma-Bautista, and José G. Vázquez-García
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Saltmarsh Aster biotype with this Saltmarsh Aster 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 9 resistant Saltmarsh Aster 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

Studies on the mechanism of resistance of Group 9 (Legacy G) resistant Saltmarsh Aster from Mexico indicate that resistance is due to enhanced metabolism, and altered translocation. There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature

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 9 (Legacy G) resistant Saltmarsh Aster 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

CANDELARIO PALMA-BAUTISTA

Research Associate University of Cordoba Department of Agricultural Chemistry and Edaphology Rabanales University Campus Building C-3 3rd Floor Cordoba, 14071, Cordoba Spain Email Candelario Palma-Bautista

JOSÉ G. VÁZQUEZ-GARCÍA

Research Associate University of Cordoba Agricultural Chemistry and Edaphology Campus of Rabanales Cordoba, 14071, Province Spain Email José G. Vázquez-García

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, Ja Dominguez Valenzuela, Candelario Palma-Bautista, and José G. Vázquez-García for providing detailed information.

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Herbicide Resistant Saltmarsh Aster Globally
(Aster squamatus)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Mexico

2021

Oranges

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Literature about Similar Cases

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Calha, Im; Rocha, F; Ruiz-Santaella, Jr; Cruz-Hipolito, He. 2008. Two decades of herbicide resistance in the Iberian Peninsula. Journal Of Plant Diseases And Protection : 79 - 84.

About 20 years ago the first case of herbicide resistance in the Iberian Peninsula was reported: Amaranthus spp. R to atrazine in Spanish orchards. Since then, herbicide resistance has evolved in many weed species. Changes on agricultural practices namely new tillage systems, new rotational programmes, combined with the increased use of herbicides led to the selection of weed biotypes resistant to a wide range of herbicides. Nowadays such a problem affects the most important crops of this Peninsula (maize, wheat, rice, citrus and olive orchards), a spectrum of 26 weed species (14 dicotyledonous and 12 monocotyledonous) with biotypes resistant to several herbicides, namely to ALS inhibitors (Alisma plantago-aquatica, Cyperus difformis, Conyza albida, Aster squamatus, Avena sterilis and Papaver rhoeas), to ACCase inhibitors (Lolium rigidum), to PS II inhibitors (Amaranthus albus, A. blitoides, A. cruentus, A. hybridus, A. retroflexus, Bromus tectorum, Chenopodium album, Conyza bonariensis, C. canadensis, Echinochloa crus-galli, Polygonum lapathifolium, Setaria faberi, S. glauca, S. verticillata, S. viridis and Solanum nigrum), to ureas and amides (B. tectorum and Alopecurus myosuroides), to synthetic auxins (E. crus-galli) and more recently to the herbicide glyphosate (C. bonariensis; L. rigidum and L. multiflorum). Diversity of resistance mechanisms responsible for resistance in this Region involved target site resistance, enhanced rates of herbicide metabolism and multiple resistance. This paper reviews the actual situation in Iberian Peninsula and gives a perspective of adequate strategies for weed management considering the resistance mechanism, the availability of alternative herbicides and other cultural practices.

Osuna, M. D. ; Fischer, A. J. ; Prado, R. de. 2003. Herbicide resistance in Aster squamatus conferred by a less sensitive form of acetolactate synthase. Pest Management Science 59 : 1210 - 1216.

A biotype of Aster squamatus (Sprengel) Hieronymus with suspected resistance to the ALS-inhibiting herbicide imazapyr was detected in a chicken farm in the province of Seville, Spain, which had been treated once a year with imazapyr for 10 years. Resistance to imazapyr in this biotype was studied using dose-response experiments, absorption and translocation assays, metabolism studies and ALS activity assays. The rate of imazapyr required to inhibit A. squamatus growth by 50% (ED₅₀) was 15 times higher for the R (resistant) than for the S (susceptible) biotype. Cross-resistance existed for the ALS-inhibitors imazamox, imazethapyr, amidosulfuron, nicosulfuron, rimsulfuron, triasulfuron and tribenuron, but not for bensulfuron. Control of A. squamatus using alternative herbicides was poor with clopyralid, intermediate with quinclorac, amitrole and MCPA, and excellent with 2,4-D, glufosinate and glyphosate. Absorption of [¹⁴C]imazapyr increased over time for both the R and S biotypes, and translocation from the treated leaf to shoots and roots was similar in both biotypes, with most of the radioactivity remaining in the treated leaf. No metabolites of imazapyr were detected in either biotype. Sensitivity of the ALS enzyme (target site) to imazapyr was lower for the R biotype (I₅₀(R)=4.28 × I₅₀ (S)). The mechanism of imazapyr resistance in this R biotype appears to be an altered ALS conferring decreased sensitivity to imazapyr at the whole-plant level..

Gonzalez-Gutierrez, J. ; Osuna, M. D. ; Prado, R. de. 1999. Chemical control of two biotypes of Aster squamatus tolerants to herbicides inhibiting ALS. : 429 - 433.

The effectiveness of herbicides inhibiting ALS and of other chemical families was studied in two biotypes of Aster squamatus. One biotype came from a field continuously treated with imazapyr (T) whereas the other came from a marginal area untreated with herbicides. Different efficacies in several herbicides inhibiting ALS were observed, although the NT biotype also showed tolerance to these herbicides. Resistance factors were not excessively high and the imazapyr treatment had the highest resistance factor (2.89). There were no differences when using herbicides from other chemical families, with the exception of triclopyr and fluroxypyr. Glyphosate, glufosinate and 2,4-D gave a good level of control of Aster squamatus..

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