<b>HRAC Group 9</b> <font size='2'> (Legacy G) </font> resistant Chloris virgata from Australia, Queensland

International Survey of Herbicide-Resistant Weeds

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Thursday, October 31, 2024

HRAC GROUP 9 (LEGACY G) RESISTANT FEATHER FINGERGRASS
(Chloris virgata)

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

Australia, Queensland

INTRODUCTION		FEATHER FINGERGRASS
Feather Fingergrass (Chloris virgata) is a monocot weed in the Poaceae family. In Queensland this weed first evolved resistance to Group 9 (Legacy G) herbicides in 2015 and infests Fallow. 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 Feb 08, 2016 )
Common Name	Feather Fingergrass
Species	Chloris virgata
Group	Inhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G)
Herbicides	glyphosate
Location	Australia, Queensland
Year	2015
Situation(s)	Fallow
Contributors - (Alphabetically)	Christopher Preston
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NOTES ABOUT THIS BIOTYPE

GENERAL

Bhagirath Chauhan

Target-Site Resistance to Glyphosate in Chloris Virgata Biotypes and Alternative Herbicide Options for its Control

Het Samir Desai ^1,2,*, Michael Thompson ¹ and Bhagirath Singh Chauhan ^1,2

¹Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland,Gatton 4343, Australia; michael.thompson1@uq.edu.au (M.T.); b.chauhan@uq.edu.au (B.S.C.)
²School of Agriculture and Food Sciences (SAFS), The University of Queensland, Gatton 4343, Australia

* Correspondence: het.desai@student.montana.edu

Received: 31 July 2020; Accepted: 25 August 2020; Published: 27 August 2020

Abstract: Due to the overdependence on glyphosate to manage weeds in fallow conditions, glyphosate resistance has developed in various biotypes of several grass weeds, including Chloris virgata Sw. The first case of glyphosate resistance in C. virgata was found in 2015 in Australia, and since then several cases have been confirmed in several biotypes across Australia. Pot studies were conducted with 10 biotypes of C. virgata to determine glyphosate resistance levels. The biotypes were identified as either susceptible, moderately resistant or highly resistant based on the glyphosate dose required to kill 50% of plants. Two glyphosate-susceptible (GS) and two glyphosate-resistant (GR) biotypes were identified by the dose-response study and analyzed for the presence of target-site mutation in the 5–enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene. Performance of alternative herbicides to glyphosate as well as the double-knock herbicide approach was evaluated on the two GS (Ch and SGM2) and two GR (SGW2 and CP2) biotypes. Three herbicides, clethodim, haloxyfop and paraquat, were found to be effective (100% control) against all four.

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Feather Fingergrass biotype with this Feather Fingergrass 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 Feather Fingergrass 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 Feather Fingergrass from Queensland please update the database.

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CONTRIBUTING WEED SCIENTISTS

CHRISTOPHER PRESTON

University Of Adelaide - Waite Campus Crc For Australian Weed Management And School Of Agriculture Box 2146 Adelaide, 5064, South Australia Australia Email Christopher Preston

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Queensland have been instrumental in providing you this information. Particular thanks is given to Christopher Preston for providing detailed information.

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Herbicide Resistant Feather Fingergrass Globally
(Chloris virgata)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Australia (New South Wales )

2015

Fallow

glyphosate

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

Australia (Queensland)

2015

Fallow

glyphosate

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

Australia (South Australia)

2015

Roadsides

glyphosate

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

Literature about Similar Cases

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Werth, J. ; Boucher, L. ; Thornby, D. ; Walker, S. ; Charles, G.. 2013. Changes in weed species since the introduction of glyphosate-resistant cotton. Crop & Pasture Science 64 : 791 - 798.

Weed management practices in cotton systems that were based on frequent cultivation, residual herbicides, and some post-emergent herbicides have changed. The ability to use glyphosate as a knockdown before planting, in shielded sprayers, and now over-the-top in glyphosate-tolerant cotton has seen a significant reduction in the use of residual herbicides and cultivation. Glyphosate is now the dominant herbicide in both crop and fallow. This reliance increases the risk of shifts to glyphosate-tolerant species and the evolution of glyphosate-resistant weeds. Four surveys were undertaken in the 2008-09 and 2010-11 seasons. Surveys were conducted at the start of the summer cropping season (November-December) and at the end of the same season (March-April). Fifty fields previously surveyed in irrigated and non-irrigated cotton systems were re-surveyed. A major species shift towards Conyza bonariensis was observed. There was also a minor increase in the prevalence of Sonchus oleraceus. Several species were still present at the end of the season, indicating either poor control and/or late-season germinations. These included C. bonariensis, S. oleraceus, Hibiscus verdcourtii and Hibiscus tridactylites, Echinochloa colona, Convolvulus sp., Ipomea lonchophylla, Chamaesyce drummondii, Cullen sp., Amaranthus macrocarpus, and Chloris virgata. These species, with the exception of E. colona, H. verdcourtii, and H. tridactylites, have tolerance to glyphosate and therefore are likely candidates to either remain or increase in dominance in a glyphosate-based system..

Werth, J. ; Thornby, D. ; Walker, S.. 2011. Assessing weeds at risk of evolving glyphosate resistance in Australian sub-tropical glyphosate-resistant cotton systems. Crop & Pasture Science 62 : 1002 - 1009.

Glyphosate resistance will have a major impact on current cropping practices in glyphosate-resistant cotton systems. A framework for a risk assessment for weed species and management practices used in cropping systems with glyphosate-resistant cotton will aid decision making for resistance management. We developed this framework and then assessed the biological characteristics of 65 species and management practices from 50 cotton growers. This enabled us to predict the species most likely to evolve resistance, and the situations in which resistance is most likely to occur. Species with the highest resistance risk were Brachiaria eruciformis, Conyza bonariensis, Urochloa panicoides, Chloris virgata, Sonchus oleraceus and Echinochloa colona. The summer fallow and non-irrigated glyphosate-resistant cotton were the highest risk phases in the cropping system. When weed species and management practices were combined, C. bonariensis in summer fallow and other winter crops were at very high risk. S. oleraceus had very high risk in summer and winter fallow, as did C. virgata and E. colona in summer fallow. This study enables growers to identify potential resistance risks in the species present and management practices used on their farm, which will to facilitate a more targeted weed management approach to prevent development of glyphosate resistance..

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