Group G/9 resistant Salsola tragus from United States, Oregon

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

GROUP G/9 RESISTANT RUSSIAN-THISTLE
(Salsola tragus)

EPSP synthase inhibitors (G/9)

United States, Oregon

INTRODUCTION		RUSSIAN-THISTLE
Russian-thistle (Salsola tragus) is a dicot weed in the Chenopodiaceae family. In Oregon this weed first evolved resistance to Group G/9 herbicides in 2016 and infests Fallow. Group G/9 herbicides are known as EPSP synthase inhibitors (Inhibition of EPSP synthase). Research has shown that these particular biotypes are resistant to glyphosate and they may be cross-resistant to other Group G/9 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 Oct 23, 2016 )
Common Name	Russian-thistle
Species	Salsola tragus
Group	EPSP synthase inhibitors (G/9)
Herbicides	glyphosate
Location	United States, Oregon
Year	2016
Situation(s)	Fallow
Contributors - (Alphabetically)	Carol Mallory-Smith
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Russian-thistle biotype with this Russian-thistle 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 Group G/9 resistant Russian-thistle 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 G/9 resistant Russian-thistle from Oregon please update the database.

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CONTRIBUTING WEED SCIENTISTS

CAROL MALLORY-SMITH

Professor Oregon State University Department of Crop And Soil Science 331B Crop Science Bldg Corvallis, 97331, Oregon United States Email Carol Mallory-Smith Web : Web Site Link

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Oregon have been instrumental in providing you this information. Particular thanks is given to Carol Mallory-Smith for providing detailed information.

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Herbicide Resistant Russian-thistle Globally
(Salsola tragus)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Canada (Saskatchewan)

1989

Wheat

chlorsulfuron

ALS inhibitors (B/2)

Canada (Alberta)

2007

Spring Barley, and Wheat

thifensulfuron-methyl, and tribenuron-methyl

ALS inhibitors (B/2)

United States (Washington)

1987

Wheat

chlorsulfuron

ALS inhibitors (B/2)

United States (Montana)

1987

Cropland, and Wheat

chlorsulfuron

ALS inhibitors (B/2)

United States (Idaho)

1990

Wheat

chlorsulfuron

ALS inhibitors (B/2)

United States (Oregon)

1993

Wheat

chlorsulfuron, metsulfuron-methyl, and triasulfuron

ALS inhibitors (B/2)

United States (California)

1994

Roadsides

chlorsulfuron, and sulfometuron-methyl

ALS inhibitors (B/2)

United States (Montana)

2015

Fallow, and Wheat

glyphosate

EPSP synthase inhibitors (G/9)

United States (Washington)

2015

Fallow

glyphosate

EPSP synthase inhibitors (G/9)

United States (Oregon)

2016

Fallow

glyphosate

EPSP synthase inhibitors (G/9)

Literature about Similar Cases

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Warwick, S. I. ; Sauder, C. A. ; Beckie, H. J.. 2010. Acetolactate synthase (ALS) target-site mutations in ALS inhibitor-resistant Russian thistle (Salsola tragus). Weed Science 58 : 244 - 251.

ALS inhibitor-resistant biotypes are the fastest growing class of herbicide-resistant (HR) weeds. A Canadian ALS inhibitor-resistant biotype of Russian thistle was first reported in 1989. The molecular basis for ALS-inhibitor resistance is unknown for Canadian populations of this polyploid weed species, and was determined in this study for one Alberta and two Saskatchewan HR Russian thistle populations. HR plants survived spray application of the ALS-inhibitor mixture thifensulfuron:tribenuron in the greenhouse. All three HR Russian thistle populations were heterogeneous and contained both HR and herbicide-susceptible (HS) individuals. The molecular basis for resistance was determined by sequencing the ALS gene and/or conducting a TaqMan genotyping assay for single nucleotide polymorphism (SNP) for the Trp₅₇₄Leu mutation. Two target-site mutations were observed: Trp₅₇₄Leu in all three biotypes (554 individuals) and Pro₁₉₇Gln in one biotype (one individual), suggesting multiple-founding events for Russian thistle HR populations in western Canada. Segregation patterns among F1 and F2 progeny arrays of HR lines sprayed under greenhouse conditions varied; some segregated (i.e., had HR and HS progeny), whereas other lines were exclusively HR. In contrast, no segregation of molecular types, i.e., Trp₅₇₄, Trp/Leu₅₇₄ and Leu₅₇₄, as would be expected with heterozygosity at a single locus Trp/Leu₅₇₄, was observed. Such lack of segregation is consistent with the polyploid genome structure of Russian thistle and the presence of two copies of the ALS gene. The presence of more than one ALS gene confounded the ability of the molecular techniques to accurately identify "true" heterozygotes in this study..

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