(Panicum miliaceum var. ruderale Kitag.)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

China, Liaoning Province
Wild Panicgrass (Panicum miliaceum var. ruderale Kitag.) is a monocot weed in the Poaceae family.  In China this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2023 and infests Corn (maize).   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 nicosulfuron 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 Aug 05, 2023 )

Common NameWild Panicgrass
SpeciesPanicum miliaceum var. ruderale Kitag.
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
LocationChina, Liaoning Province
Situation(s)Corn (maize)
Contributors - (Alphabetically)Ian Heap 
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Enhanced metabolic ability enabled wild panicgrass (Panicum miliaceum L. var. ruderale kit.) resistance to ALS inhibitor herbicide.

 Author(s) : Guan YiDi ;  Cao ShihAn ;  Zou YiZe ;  Liu LiRu ;  Yang ChangBi ;  Ji MingShan

Author Affiliation : College of Plant Protection, Shenyang Agricultural University, No. 120 Dongling Road, Shenhe District, Shenyang City 110866, China.

Author Email :

Journal article : Pesticide Biochemistry and Physiology 2023 Vol.194 ref.23  

Abstract : Wild panicgrass (Panicummiliaceum L. var. ruderale kit.) is an annual grass weed that primarily occurs in maize fields. Nicosulfuron is a widely used selective herbicide that effectively controls gramineous weeds in maize fields. However, owing to its long-term and extensive application, the control of P. miliaceum has been substantially reduced. The objective of this study was to determine the resistance pattern to ALS inhibitors in P. miliaceum and investigate the underlying resistance mechanisms. These are important for guiding the prevention and eradication of resistant weeds. Whole plant bioassays showed P. miliaceum had evolved high levels of resistance to nicosulfuron and multiple resistance to atrazine and mesotrione. The ALS gene sequence results indicated the absence of mutations in the resistant population. Additionally, there was no significant difference found in the inhibition rate of the ALS enzyme activity (I50) between the resistant and sensitive populations. Following the application of malathion the resistant P. miliaceum population became more sensitive to nicosulfuron. At 96 h after application of nicosulfuron, glutathione-S-transferase activity in the resistant population was significantly higher than that in the susceptible population. The study reveals that the main cause of resistance to ALS inhibitor herbicide in P. miliaceum is likely increased metabolism of herbicides. These findings may assist in devising effective strategies for preventing and eliminating resistant P. miliaceum.  

ISSN : 0048-3575

DOI : 10.1016/j.pestbp.2023.105510

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Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Wild Panicgrass biotype with this Wild Panicgrass 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 Wild Panicgrass indicate that the inheritance is determined by a dominant 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 Wild Panicgrass from China indicate that resistance is due to enhanced metabolism.  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 Wild Panicgrass from China please update the database.
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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 Wild Panicgrass Globally
(Panicum miliaceum var. ruderale Kitag.)
Herbicide Resistant Wild Panicgrass Globally
(Panicum miliaceum var. ruderale Kitag.)
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Herbicide Resistant Wild Panicgrass Globally
(Panicum miliaceum var. ruderale Kitag.)
#CountryFirstYearSituationActive IngredientsSite of Action
1 ChinaChina 2023 Corn (maize) nicosulfuron 9 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
1359Panicum miliaceum var. ruderale Kitag.Wild Panicgrass27273
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