HRAC GROUP 2 (LEGACY B) RESISTANT SMALLSEED FLAXFALSE
(Camelina microcarpa)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

United States, Oregon

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INTRODUCTION SMALLSEED FLAXFALSE Smallseed Flaxfalse (Camelina microcarpa) is a dicot weed in the Brassicaceae family.  In Oregon this weed first evolved resistance to Group 2 (Legacy B) herbicides in 1999 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, and metsulfuron-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 Feb 04, 2002 ) Common Name Smallseed Flaxfalse Species Camelina microcarpa Group Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B) Herbicides chlorsulfuron, and metsulfuron-methyl Location United States, Oregon Year 1999 Situation(s) Wheat Contributors - (Alphabetically) Brad Hanson  Edit this Case  |  Add New Case of Resistance  |  Add Note

ACADEMIC ASPECTS Confirmation Tests Field, and Greenhouse trials comparing a known susceptible Smallseed Flaxfalse biotype with this Smallseed Flaxfalse 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 Smallseed Flaxfalse 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 Smallseed Flaxfalse from Oregon please update the database.   Edit Case  |  Add Note  |  Add Article  |  Add New Case  |  Help

CONTRIBUTING WEED SCIENTISTS BRAD HANSON Cooperative Extension Weed Specialist University Of California, Davis Department Of Plant Sciences MS-4, One Shields Ave 276 Robbins Hall Davis, 91616, California United States Email Brad Hanson 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 Brad Hanson for providing detailed information.

Herbicide Resistant Smallseed Flaxfalse Globally (Camelina microcarpa) Herbicide Resistant Smallseed Flaxfalse Globally (Camelina microcarpa) Drag a column header and drop it here to group by that column Herbicide Resistant Smallseed Flaxfalse Globally (Camelina microcarpa) # Country Country StateName FirstYear Situation Active Ingredients CountryID Site of Action WeedID Species CommonName ResistID 1 United States (Oregon) United States Oregon 1999 Wheat chlorsulfuron, and metsulfuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B) 207 Camelina microcarpa Smallseed Flaxfalse 5111

Literature about Similar Cases

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Francis, A. ; Warwick, S. I.. 2009. The biology of Canadian weeds. 142. Camelina alyssum (Mill.) Thell.; C. microcarpa Andrz. ex DC.; C. sativa (L.) Crantz. Canadian Journal of Plant Science 89 : 791 - 810.

This paper summarizes biological information on three cruciferous weed species: Camelina alyssum, C. microcarpa and C. sativa. Camelina sativa, which had been gathered or cultivated as an oil seed for many centuries in Europe, was the first to reach North America as a weed, towards the mid-19th century, gradually spreading across the prairies, mainly in crops, to British Columbia and the Northwest Territory. The most common of the three species in North America, C. microcarpa, arrived in the late 19th century, and subsequently appeared at numerous crop and uncultivated sites across the country, probably in cargo as the railways expanded. Camelina alyssum appeared in the early 20th century at restricted sites on the prairies, mostly in Saskatchewan. All three species have diminished in importance as crop weeds in western Canada over the past few decades. This reduction could be related to increased weed control by herbicides. Herbicide-resistant biotypes have recently been reported in C. microcarpa. Camelina sativa has attracted renewed interest as an oil crop, because of an adaptation to various climatic conditions, low nutrient requirements and resistance to disease and pests. In Europe, where it is now widely grown, it has shown considerable potential in the food, animal feed, nutraceutical, paint, dye, cosmetic and biofuel industries. In North America, it is being grown on a trial basis mainly for its potential as a biofuel in Alberta, Saskatchewan, the Maritime Provinces, and the northern United States of America..

Hanson, B. D. ; Park, K. W. ; Mallory-Smith, C. A. ; Thill, D. C.. 2004. Resistance of Camelina microcarpa to acetolactate synthase inhibiting herbicides. Weed Research (Oxford) 44 : 187 - 194.

An accession of Camelina microcarpa suspected to be resistant to sulfonylurea herbicides was identified in Oregon in 1998 field experiments. Greenhouse research confirmed that the putative resistant biotype was resistant to chlorsulfuron and metsulfuron on a whole plant level. Compared with the resistant (R) biotype, the susceptible (S) biotype was 1000 and 10 000-fold more sensitive to metsulfuron and chlorsulfuron respectively. The R biotype was also resistant to other sulfonylurea, sulfonylaminocarbonyl-triazolinone, imidazolinone and triazolopyrimidine herbicides. An in vivo enzyme assay indicated that acetolactate synthase (ALS) from the R plants required 111 times more chlorsulfuron to inhibit activity by 50% compared with the amount required to have a similar effect on ALS from S plants. Analysis of the nucleotide and amino acid sequences demonstrated that a single-point mutation from G to T in the als1 gene conferred the change from the amino acid tryptophan to leucine at position 572 in the resistant biotype. This research confirmed that ALS inhibitor resistance in an Oregon accession of C. microcarpa is based on an altered target site conferred by a single-point mutation..

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