<b>HRAC Group 9</b> <font size='2'> (Legacy G) </font> resistant Chloris truncata from Spain

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 9 (LEGACY G) RESISTANT WINDMILL GRASS
(Chloris truncata)

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

Spain, Extremadura

INTRODUCTION		WINDMILL GRASS
Windmill Grass (Chloris truncata) is a monocot weed in the Poaceae family. In Spain this weed first evolved resistance to Group 9 (Legacy G) herbicides in 2023 and infests Roadsides. 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 Mar 25, 2024 )
Common Name	Windmill Grass
Species	Chloris truncata
Group	Inhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G)
Herbicides	glyphosate
Location	Spain, Extremadura
Year	2023
Situation(s)	Roadsides
Contributors - (Alphabetically)	GERMAN MORA MARIN, Maria D. Osuna, and Joel Torra
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NOTES ABOUT THIS BIOTYPE

GENERAL

Characterization of herbicide resistance of Spanish populations of Chloris truncata versus glyphosate Characterization of herbicide resistance of Spanish populations of Chloris truncata against glyphosate

German Mora_,, Jordi Recasens, María Dolores Osuna, Miriam Gil Monreal & Joel Torra

Spain (E-mail: german.mora@udl.cat ) https://doi.org/10.19084/rca.35026

ABSTRACT Chloris truncatais a perennial grass with a C4 photosynthetic pathway. It is native to Australia, but it is currently distributed in other subtropical regions of the world. In Spain, it is considered a naturalized allochthonous species, mainly in Extremadura and Catalonia. Currently, there have been reported failures in its control with glyphosate. Previous studies report that herbicide resistance is based onEPSPSgene amplification. In 2022, seeds were collected from field plant survivors of glyphosate treatments in Talayuela – Extremadura (CTT-R); a population from Australia (CTA-S) was used as sensitive reference material. Preliminary tests (greenhouse) were carried out on seedlings with four leaves (BBCH 14), with doses of (1.5 and 3 L ha-1) 540 and 1080 g ai ha-1of glyphosate, with 100% survival. In the same year, dose-response trials were carried out with a dose range between 270 and 8,640 g ai ha-1. At 28 days after treatment (DAT), the survival percentage was evaluated and values of: 1,146.7 and 321.34 g ai ha-1were determined with a Resistance Factor (RF) of 3.7 times according to GRfifty; for LDfifty, 1,882.9 and 712.5 g ai ha-1with RF of 2.6 for the CTT-R and CTA-S populations, respectively. Complementary dose-response experiments are currently being carried out with new populations collected in Extremadura and Catalonia, to confirm or not, the presence of other glyphosateresistant biotypes and to elucidate the resistance mechanism involved.

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Windmill Grass biotype with this Windmill Grass 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 Windmill Grass 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 9 (Legacy G) resistant Windmill Grass from Spain please update the database.

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CONTRIBUTING WEED SCIENTISTS

GERMAN MORA MARIN

PhD student Universitat de Lleida HBJ - Maleherbologia Carrer ROCA LABRADOR 12. Piso 5, puerta 3A Lleida, 25003, Cataluña Spain Email GERMAN MORA MARIN Web : Web Site Link

MARIA D. OSUNA

Researcher CICYTEX Crop Protection Finca La Orden Crta AV, km 372 Guadajira, 06187, Badajoz Spain Email Maria D. Osuna Web : Web Site Link

JOEL TORRA

Research Assistant University Of Lleida Depart. Hortofructicultura Botànica I Jardineria Rovira Roure 191, Etsea, Ed. 1 Lleida, 25198, Badajoz Spain Email Joel Torra Web : Web Site Link

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Spain have been instrumental in providing you this information. Particular thanks is given to GERMAN MORA MARIN, Maria D. Osuna, and Joel Torra for providing detailed information.

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Herbicide Resistant Windmill Grass Globally
(Chloris truncata)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Australia (New South Wales )

2010

Fallow

glyphosate

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

Australia (Victoria)

2015

Roadsides

glyphosate

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

Spain

2023

Roadsides

glyphosate

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

Literature about Similar Cases

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Cook, T.. 2013. How widespread is resistance?. Australian Cottongrower 34 : 34, 35 - 39.

This paper presents the results of surveys conducted on the distribution (regardless of herbicide resistance status) in Australia of wild oats [Avena fatua], fleabane [Erigeron], awnless barnyard grass [Echinochloa colona], annual ryegrass [Lolium multiflorum] and windmill grass [Chloris truncata], and their management. The most widespread resistant species are wild oats and fleabane. Awnless barnyard grass and annual rygrass, both resistant to glyphosate, are found mainly in the north and south of the northern cropping region, respectively. The glyphosate-resistant windmill grass is in the infancy of its spread, mainly confined to the central west plains..

Widderick, M. J. ; McLean, A. R. ; Walker, S. R.. 2012. Non-chemical options for managing the seed bank of glyphosate resistant weeds. : 279 - 280.

Glyphosate resistance is becoming a common problem in farming systems of the subtropical cropping region of Australia. Glyphosateresistance has been confirmed in awnless barnyard grass (Echinochloa colona L. (Link)), liverseed grass (Urochloa panicoides P.Beauv.), flaxleaf fleabane (Conyza bonariensis (L.) Cronquist), windmill grass (Chloris truncata R.Br.) and annual ryegrass (Lolium rigidum (Gaud.)) (Preston 2012). As well, common sowthistle (Sonchus oleraceus L.) was identified at high risk of developing glyphosate resistance. To prevent further glyphosate resistance and to improve management of existing glyphosate resistant populations, alternative management tactics for these key weeds are required. This paper reports on the impact of different tillage and stubble treatments on emergence and persistence of awnless barnyard grass and common sowthistle in two experiments located in southern Darling Downs, Queensland..

Malone, J. ; Cook, A. ; Wu HanWen ; Hashem, A. ; Preston, C.. 2012. Management of glyphosate resistant weeds in non-agricultural areas. : 184 - 186.

A survey of non-agricultural areas including roadsides, railway right-of-ways and irrigation channels was conducted across Australia to investigate the extent of glyphosate resistance in four weed species. A total of 150 windmill grass (Chloris truncata R.Br.) and 84 fleabane (Conyza bonariensis (L.) Cronquist) populations were collected from QLD, NSW, VIC, SA and WA. A total of 7% of the windmill grass and 52% of the fleabane populations contained individuals resistant to glyphosate. Of 186 populations of annual ryegrass (Lolium rigidum Gaudin) collected from SA, NSW and WA, 50% were found to contain high numbers of resistant individuals. Nine barnyard grass (Echinochloa colona (L.) Link) populations were collected from northern NSW and three of these were resistant. Glyphosate resistance in these non-agricultural areas has the ability to spread into other areas, such as crops, and cause management difficulties elsewhere. Therefore, the high degree of resistance found in this study highlights the importance for the development and application of management strategies for these areas..

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