<b>HRAC Group 2</b> <font size='2'> (Legacy B) </font> resistant Apera spica-venti from Germany

International Survey of Herbicide-Resistant Weeds

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Sunday, October 26, 2025

HRAC GROUP 2 (LEGACY B) RESISTANT SILKY WINDGRASS
(Apera spica-venti)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

Germany

INTRODUCTION		SILKY WINDGRASS
Silky Windgrass (Apera spica-venti) is a monocot weed in the Poaceae family. In Germany this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2005 and infests Wheat. 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 chlorsulfuron, florasulam, flupyrsulfuron-methyl-Na, iodosulfuron-methyl-Na, mesosulfuron-methyl, pyroxsulam, sulfometuron-methyl, and sulfosulfuron 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 Nov 12, 2012 )
Common Name	Silky Windgrass
Species	Apera spica-venti
Group	Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicides	chlorsulfuron, florasulam, flupyrsulfuron-methyl-Na, iodosulfuron-methyl-Na, mesosulfuron-methyl, pyroxsulam, sulfometuron-methyl, and sulfosulfuron
Location	Germany
Year	2005
Situation(s)	Wheat
Contributors - (Alphabetically)	Natalie Balgheim, Dario Massa, and Jean Wagner
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Silky Windgrass biotype with this Silky Windgrass 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 Silky Windgrass indicate that the inheritance is determined by a one gene, semi dominant, nuclear trait. 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 2 (Legacy B) resistant Silky Windgrass from Germany indicate that resistance is due to an altered target site. 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 2 (Legacy B) resistant Silky Windgrass from Germany please update the database.

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CONTRIBUTING WEED SCIENTISTS

NATALIE BALGHEIM

Phd Student University Of Hohenheim Depart. Of Weed Science P.O. Box 70 Stuttgart, 70599 Germany Email Natalie Balgheim

DARIO MASSA

Weed Scientist BASF SE Depart. Of Weed Science Speyerer Str. 2 Limburgerhof, 67117 , Rheinland-Pfalz Germany Email Dario Massa

JEAN WAGNER

Weed Scientist Plant Pathology and Crop Protection Department of Crop Sciences Grisebachstrasse 6 Göttingen, 37077, Rheinland-Pfalz Germany Email Jean Wagner Web : Web Site Link

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Germany have been instrumental in providing you this information. Particular thanks is given to Natalie Balgheim, Dario Massa, and Jean Wagner for providing detailed information.

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Herbicide Resistant Silky Windgrass Globally
(Apera spica-venti)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Austria

2009

Cereals

iodosulfuron-methyl-Na, and isoproturon

Multiple Resistance: 2 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Belgium

2019

Wheat

foramsulfuron, iodosulfuron-methyl-Na, and mesosulfuron-methyl

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Czech Republic

2005

Cereals, and Winter wheat

chlorsulfuron, iodosulfuron-methyl-Na, isoproturon, mesosulfuron-methyl, pyroxsulam, and sulfosulfuron

Multiple Resistance: 2 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Denmark

2011

Winter wheat

iodosulfuron-methyl-Na, and sulfosulfuron

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Denmark

2016

Wheat

fenoxaprop-ethyl, florasulam, iodosulfuron-methyl-Na, mesosulfuron-methyl, and pinoxaden

Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

France

2006

Wheat

iodosulfuron-methyl-Na, mesosulfuron-methyl, and pyroxsulam

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Germany

1997

Cereals, and Winter wheat

isoproturon

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Germany

2005

Wheat

chlorsulfuron, florasulam, flupyrsulfuron-methyl-Na, iodosulfuron-methyl-Na, mesosulfuron-methyl, pyroxsulam, sulfometuron-methyl, and sulfosulfuron

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Germany

2009

Spring Barley, and Winter wheat

fenoxaprop-ethyl, iodosulfuron-methyl-Na, isoproturon, mesosulfuron-methyl, pinoxaden, pyroxsulam, and sulfosulfuron

Multiple Resistance: 3 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Latvia

2015

Wheat, and Winter wheat

iodosulfuron-methyl-Na

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Lithuania

2013

Winter wheat

iodosulfuron-methyl-Na

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Poland

2005

Winter wheat

chlorsulfuron, iodosulfuron-methyl-Na, procarbazone-Na, and sulfosulfuron

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Poland

2010

Winter wheat

fenoxaprop-ethyl, and pinoxaden

Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)

Poland

2011

Winter wheat

chlorsulfuron, fenoxaprop-ethyl, pinoxaden, sulfometuron-methyl, and sulfosulfuron

Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Poland

2012

Winter wheat

isoproturon

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Sweden

2006

Winter wheat

isoproturon

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Sweden

2010

Winter wheat

iodosulfuron-methyl-Na, pyroxsulam, and sulfosulfuron

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Switzerland

1994

Wheat

isoproturon

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Specific Papers about this Case

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Massa, D. ; Krenz, B. ; Gerhards, R.. 2011. Target-site resistance to ALS-inhibiting herbicides in Apera spica-venti populations is conferred by documented and previously unknown mutations. Weed Research (Oxford) 51 : 294 - 303.

In this study, whole-plant bioassays were performed on 72 Apera spica-venti populations that have survived application of acetolactate synthase (ALS)-inhibiting herbicides in recent years. Molecular genetic analysis of the ALS gene revealed a Thr mutation at Pro₁₉₇ within 67 populations. Sequencing of the whole ALS gene from wild-type and resistant plants not carrying the above-mentioned mutation revealed the presence of a Leu mutation at Trp₅₇₄ within two populations and an Asn mutation at Pro₁₉₇ within two populations. As the Pro₁₉₇-Asn amino acid substitution is reported for the first time in a field-selected weed population, a Cleaved Amplified Polymorphic Sequences (CAPS) marker was developed for its quick detection. In addition, one novel mutation was found within a population that coded for a His substitution at Arg₃₇₇. Enzyme assays confirmed a significant reduction in inhibition of ALS activity compared with the wild type. This population showed resistance to sulfonylureas (SUs) and cross-resistance to sulfonylaminocarbonyltriazolinones (SCTs) and triazolopyrimidines (TPs) within the whole-plant bioassays. ALS protein sequence alignments from weedy and cultural plants revealed that the Arg377 is highly conserved among known wild-type enzymes. In agreement with existing literature concerning the structure and mechanisms of inhibition of plant ALS, this mutation is probably involved in target-site resistance to ALS inhibitors. Our results suggest that further single-nucleotide polymorphisms impairing proper herbicide performance might be selected within field populations in the near future, making the short- and long-range evolution of target-site resistance difficult to predict depending solely on herbicide use history..

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Literature about Similar Cases

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Katerina Hamouzová, Pavlíina Košnarová, Jaroslav Salava, Josef Soukup and Pavel Hamouza. 2013. Mechanisms of resistance to acetolactate synthase-inhibiting herbicides in populations ofApera spica-ventifrom the Czech Republic. Pest Management Science : .

BACKGROUND: This study investigates the mechanisms of resistance to acetolactate synthase-inhibiting herbicides in populations of Apera spica-venti (L.) P.B. from the Czech Republic.

RESULTS: The proportion of resistance due to mutant acetolactate synthase (ALS) alleles was estimated by genotyping individuals from each of three populations for the eight ALS mutations known to confer resistance. Four resistance-conferring ALS mutations were identified: Pro-197-Ala, Pro-197-Thr, Trp-574-Leu and previously unreported Trp-574-Met substitution. Two populations (R1, R3) have amino acid substitution at positions Pro-197 and Trp-574. Individuals from the R3 population had two different resistance alleles. In the R2 population, only the resistant Trp-574-Met substitution was detected. Ten other single point mutations were identified, but these were not related to resistance.

The cytochrome malathion decreased chlorsulfuron resistance in the resistant populations that were examined. Although malathion increased mortality, the GR50 values were too high to conclude that non-target-based mechanism was the main one for the resistance in Apera spica-venti populations tested in this study.
CONCLUSIONS: Individuals of Apera spica-venti populations tested in this study possess the target-site ALS resistance mutation and an additional so far unknown resistance mechanism(s)..

Wolber, D. ; Warnecke-Busch, G. ; Wagner, J.. 2012. Herbizidresistence at Alopecurus myosuroides und Apera spica-venti in Lower Saxony. Julius-Kühn-Archiv : 443 - 445.

Wagner, J. ; Wolber, D.. 2012. Occurence of herbicide resistance to ALS-inhibitors and of resistance alleles identified by pyrosequencing in Alopecurus myosuroides Huds. (blackgrass) und Apera spica-venti (L.) Beauv. (silky bent-grass) in agricultural areas from Lower Saxony. Julius-Kühn-Archiv : .

Rummland, J. ; Kerlen, D. ; Nordmeyer, H. ; Richter, O.. 2012. Modelling the development of herbicide resistance. Julius-Kühn-Archiv 1 : 149 - 154.

A population dynamic and genetic model was used to simulate the genetic evolution in an Apera spica-venti (L.) P. Beauv. population. The basis of the model is a life cycle of an annual weed population which is divided into five development stages. These are the seed bank, the seedlings, young plants, the seed producing plants and the produced seeds. The stages are linked through transition probabilities. The interaction between resistant and susceptible genotypes is mediated by a genetic submodel. The model supports the development of management strategies to prevent, reduce or at least retard the development of resistance. Through an embedment into a cellular automaton the dispersal of genetic information is simulated at field scale. Three simulations with different herbicide treatments are compared regarding the resistance evolution..

Petersen, J. ; Naruhn, G. ; Raffel, H.. 2012. Non target-site resistance inherent in Alopecurus myosuroides and Apera spica-venti - resistance pattern and factors. Julius-Kühn-Archiv 1 : 43 - 50.

Alopecurus myosuroides and Apera spica-venti are the most important grass weeds in German cereal cropping systems. Both species show increasing resistance problems with herbicide resistant biotypes in many regions. In many cases, non target-site resistance (TSR) mechanism can be detected. In these biotypes resistance is assumingly based on non target-site-mechanisms (NTSR) and an enhanced metabolism might be responsible in the first place. Resistance in A. spica-venti biotypes can also be found against pre-emergence herbicides like diflufenican and pendimethalin. However, untill now no resistance in A. spica-venti against the active ingredients flurtamone, flufenacet and prosulfocarb could be detected. A. myosuroides biotypes also frequently show NTSR mechanisms. Resistance patterns are variable and predictions about the efficacy of one herbicide cannot be made based on the knowledge of the effects of another ingredient even within the same mode of action group. The resistance patterns of different A. myosuroides biotypes and crosses indicate a complex, polygenetic control of NTSR mechanisms..

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