<b>HRAC Group 2</b> <font size='2'> (Legacy B) </font> resistant Picris hieracioides from Russia

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 2 (LEGACY B) RESISTANT HAWKWEED OXTONGUE
(Picris hieracioides)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

Russia

INTRODUCTION		HAWKWEED OXTONGUE
Hawkweed Oxtongue (Picris hieracioides) is a dicot weed in the Asteraceae family. In Russia this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2000 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 amidosulfuron, chlorsulfuron, triasulfuron, and tribenuron-methyl 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 Mar 06, 2004 )
Common Name	Hawkweed Oxtongue
Species	Picris hieracioides
Group	Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicides	amidosulfuron, chlorsulfuron, triasulfuron, and tribenuron-methyl
Location	Russia
Year	2000
Situation(s)	Wheat
Contributors - (Alphabetically)	Peter Solymosi
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NOTES ABOUT THIS BIOTYPE

GENERAL

Solymosi, P.; Nagy, P. 2000. Sulfonylurea resistance in Picris hieracioides L. Növényvédelem 2000 Vol. 36 No. 12 pp. 619-624
A keserűgyökér (Picris hieracioides L.) taxonómiailag is azonosítható szulfonilkarbamidellenálló biotípusának jellemzése.

We have found a sulfonylurea resistant Picris hieracioides biotype in Russia. This is a new case of sulfonylurea resistance. The degree of resistance varies with the biotype and herbicide. For chlorsulfuron, triasulfuron, tribenuron-methyl and amidosulfuron, the herbicide concentration required to reduce enzyme activity 50% (I50) was 6 to 22-fold greater using ALS [acetolactate synthase] isolated from the resistant biotype compared to ALS from the susceptible biotype. The imidazolinone herbicide imazapyr was less inhibitory (1.4-fold) to resistant P. hieracioides ALS. Lontrel 300 [clopyralid] (0.5 l/ha) and Mustang [florasulam + 2,4-D] (0.6 l/ha) herbicides were effective against the sulfonylurea resistant biotype of P. hieracioides.

Hungarian Academy of Sciences, 1245 Budapest, P.O. Box 1000, Hungary.

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Hawkweed Oxtongue biotype with this Hawkweed Oxtongue 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 Hawkweed Oxtongue 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 2 (Legacy B) resistant Hawkweed Oxtongue from Russia please update the database.

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CONTRIBUTING WEED SCIENTISTS

PETER SOLYMOSI

Hungarian Academy Of Sciences Dept of Horticulture 164 Plant Science Bldg, Budapest, H-1525 Hungary

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

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Herbicide Resistant Hawkweed Oxtongue Globally
(Picris hieracioides)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Russia

2000

Wheat

amidosulfuron, chlorsulfuron, triasulfuron, and tribenuron-methyl

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

Literature about Similar Cases

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Solymosi, P. ; Nagy, P.. 2000. Sulfonylurea resistance in Picris hieracioides L. Növényvédelem 36 : 619 - 624.

We have found a sulfonylurea resistant Picris hieracioides biotype in Russia. This is a new case of sulfonylurea resistance. The degree of resistance varies with the biotype and herbicide. For chlorsulfuron, triasulfuron, tribenuron-methyl and amidosulfuron, the herbicide concentration required to reduce enzyme activity 50% (I₅₀) was 6 to 22-fold greater using ALS [acetolactate synthase] isolated from the resistant biotype compared to ALS from the susceptible biotype. The imidazolinone herbicide imazapyr was less inhibitory (1.4-fold) to resistant P. hieracioides ALS. Lontrel 300 [clopyralid] (0.5 l/ha) and Mustang [florasulam + 2,4-D] (0.6 l/ha) herbicides were effective against the sulfonylurea resistant biotype of P. hieracioides..

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