(Ammannia multiflora)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

China, Yangzhou
Many Flowered Ammannia (Ammannia multiflora) is a dicot weed in the Lythraceae family.  In China this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2022 and infests Rice.   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 bensulfuron-methyl, and penoxsulam 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.

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QUIK STATS (last updated Jun 23, 2023 )

Common NameMany Flowered Ammannia
SpeciesAmmannia multiflora
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicidesbensulfuron-methyl, and penoxsulam
LocationChina, Yangzhou
Contributors - (Alphabetically)Ian Heap 
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Characterization of target-site resistance to ALS-inhibiting herbicides in Ammannia multiflora populations.

 Author(s) : Deng Wei ;  Duan ZhiWen ;  Li Yang ;  Cui HanWen ;  Peng Cheng ;  Yuan ShuZhong

Author Affiliation : Lecturer, College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China.

Author Email :

Journal article : Weed Science 2022 Vol.70 No.3 pp.292-297 ref.36  

Abstract : Ammannia multiflora Roxb. is a dominant broadleaf weed that is a serious problem in southern China rice fields, and acetolactate synthase (ALS)-inhibiting herbicides have been used for its control for more than 20 years. Excessive reliance on ALS-inhibiting herbicides has led to herbicide resistance in A. multiflora. In this study, 10 A. multiflora populations from the Jiangsu Province of China were collected, and the resistance levels and target site-resistance mechanisms to ALS-inhibiting herbicides bensulfuron-methyl and penoxsulam were investigated. The dose-response assays showed that eight populations evolved resistance to bensulfuron-methyl (9.1- to 90.9-fold) and penoxsulam (5.0- to 103.1-fold). Amplification of ALS genes indicated that there were three ALS genes (AmALS1AmALS2, and AmALS3) in A. multiflora. Sequence analysis revealed amino acid mutations at Pro-197 in either AmALS1 (Pro-197-Ala, Pro-197-Ser, and Pro-197-His) or AmALS2 (Pro-197-Ser and Pro-197-Arg) in resistant populations, and no mutations were found in AmALS3. Moreover, two independent mutations (Pro-197-Ala in AmALS1 and Pro-197-Ser in AmALS2 or Pro-197-Ala in AmALS1 and Pro-197-Arg in AmALS2) coexisted in two resistant populations, respectively. In addition, the auxin mimic herbicides MCPA and florpyrauxifen-benzyl, the photosystem II inhibitor bentazon, and the protoporphyrinogen oxidase inhibitor carfentrazone-ethyl can effectively control the resistant A. multiflora populations. Our study demonstrates the wide prevalence of ALS inhibitor-resistant A. multiflora populations in Jiangsu Province and the diversity of Pro-197 mutations in ALS genes and provides alternative herbicide options for controlling resistant A. multiflora populations.

ISSN : 0043-1745

DOI : 10.1017/wsc.2022.22  

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Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Many Flowered Ammannia biotype with this Many Flowered Ammannia biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetic studies on HRAC Group 2 resistant Many Flowered Ammannia 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

Studies on the mechanism of resistance of Group 2 (Legacy B) resistant Many Flowered Ammannia from China 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 Many Flowered Ammannia from China please update the database.
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International Survey of Herbicide-Resistant Weeds
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The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in China have been instrumental in providing you this information. Particular thanks is given to Ian Heap for providing detailed information.
Herbicide Resistant Many Flowered Ammannia Globally
(Ammannia multiflora)
Herbicide Resistant Many Flowered Ammannia Globally
(Ammannia multiflora)
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Herbicide Resistant Many Flowered Ammannia Globally
(Ammannia multiflora)
#CountryFirstYearSituationActive IngredientsSite of Action
1 ChinaChina 2022 Rice bensulfuron-methyl, and penoxsulam 9 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
1360Ammannia multifloraMany Flowered Ammannia27279
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