International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
MULTIPLE RESISTANT POWELL AMARANTH
(Amaranthus powellii)


Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
Photosystem II inhibitors (C1/5)

Canada, Ontario
INTRODUCTION POWELL AMARANTH
Powell Amaranth (Amaranthus powellii) is a dicot weed in the Amaranthaceae family.  In Ontario this weed first evolved multiple resistance (to 2 herbicide sites of action) in 1998 and infests Corn (maize), Soybean, and Wheat.  Multiple resistance has evolved to herbicides in the Groups B/2, and C1/5.  These particular biotypes are known to have resistance to atrazine, imazethapyr, and metribuzin and they may be cross-resistant to other herbicides in the Groups B/2, and C1/5.

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 Dec 28, 2000 )

Common NamePowell Amaranth
SpeciesAmaranthus powellii
GroupALS inhibitors (B/2)
Photosystem II inhibitors (C1/5)
Herbicidesatrazine, imazethapyr, and metribuzin
LocationCanada, Ontario
Year1998
Situation(s)Corn (maize), Soybean, and Wheat
Contributors - (Alphabetically)Francois Tardif 
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NOTES ABOUT THIS BIOTYPE

FIELD HISTORIES

Francois Tardif
We believe this case of multiple resistance is the result of sequential selection. The grower most likely had triazine resistance in his fields in the 1980s. Reliance on ALS inhibitors (mostly imazethapyr) increased in the 1990s and it is very likely that this biotype was reselected for imazethapyr resistance.

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GENERAL

Hugh Beckie
Ferguson, G. M., R. S. Diebold, F. J. Tardif, and A. S. Hamill. 2000. Populations of green pigweed (Amaranthus powellii) and redroot pigweed (Amaranthus retroflexus) in Ontario show different patterns of resistance to ALS-inhibiting herbicides and to triazines. Weed Sci. Soc. Am. Abstr. 40:47-48.

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MECHANISM

Francois Tardif
We know that this biotype has a mutation in the psbA gene that confers triazine resistance. It also has a mutation in the ALS gene (carboxy end mutation) that causes imidazolinone resistance.

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ONGOING RESEARCH

Francois Tardif
We are working on the fitness of this biotype.

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STUDENT CONTACTS

Francois Tardif
Three grad students contributed on this biotype as part of their M. Sc. theses. Gabrielle Ferguson did the initial work on this biotype, confirming ALS resistance. Kris McNaughton was able to sequence the ALS gene and confirm the mutation. SHane Diebold preformed the screen for ttriazine resistance and confirmed the presence of the nuclear gene mutation.

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Powell Amaranth biotype with this Powell Amaranth 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 B, C1/2, 5 resistant Powell Amaranth indicate that the inheritance is determined by a two gene 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 multiple resistant Powell Amaranth from Ontario 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

Triazine resistant weeds often exhibit a lower relative fitness when compared to susceptible biotypes.  The most common mutation conferring triazine resistance (Ser 264 to Gly mutation of the psbA gene) also causes a reduction in CO2 fixation, quantum yield, and seed and biomass production.  There is no record in this database referring specifically to fitness studies on multiple resistant Powell Amaranth from Ontario.
 
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CONTRIBUTING WEED SCIENTISTS

FRANCOIS TARDIF
Associate Professor
University Of Guelph
Department Of Plant Agriculture
2055 Radatz Ave
Guelph, N1G 2W1, Ontario
Canada
Email Francois Tardif
Web   : Web Site Link

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Ontario have been instrumental in providing you this information. Particular thanks is given to Francois Tardif for providing detailed information.
Herbicide Resistant Powell Amaranth Globally
(Amaranthus powellii)
Herbicide Resistant Powell Amaranth Globally
(Amaranthus powellii)
Drag a column header and drop it here to group by that column
Herbicide Resistant Powell Amaranth Globally
(Amaranthus powellii)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Canada (Ontario) CanadaOntario1977 Corn (maize) atrazine, and metribuzin 7 Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth1158
2 Canada (Ontario) CanadaOntario1998 Corn (maize), Cropland, and Soybean imazethapyr, and thifensulfuron-methyl 7 ALS inhibitors (B/2)
15Amaranthus powelliiPowell Amaranth1159
3 Canada (Ontario) CanadaOntario1998 Corn (maize), Soybean, and Wheat atrazine, imazethapyr, and metribuzin 7 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth5049
4 Canada (Ontario) CanadaOntario1999 Carrots atrazine, linuron, monolinuron, and prometryn 7 Multiple Resistance: 2 Sites of Action
Photosystem II inhibitors (C1/5)
PSII inhibitor (Ureas and amides) (C2/7)
15Amaranthus powelliiPowell Amaranth5048
5 Canada (Manitoba) CanadaManitoba2008 Beans, and Wheat thifensulfuron-methyl, and tribenuron-methyl 7 ALS inhibitors (B/2)
15Amaranthus powelliiPowell Amaranth5631
6 Czech RepublicCzech Republic 1989 Orchards atrazine, cyanazine, prometryn, simazine, and terbutryn 12 Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth78
7 FranceFrance 1982 Corn (maize) atrazine 17 Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth452
8 SwitzerlandSwitzerland 1986 Corn (maize) atrazine 41 Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth197
9 United States (Washington) United StatesWashington1992 Mint terbacil 45 Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth331
10 United States (Ohio) United StatesOhio1996 Soybean imazaquin 45 ALS inhibitors (B/2)
15Amaranthus powelliiPowell Amaranth1100
11 United States (Michigan) United StatesMichigan2001 Asparagus, and Nurseries atrazine, and diuron 45 Multiple Resistance: 2 Sites of Action
Photosystem II inhibitors (C1/5)
PSII inhibitor (Ureas and amides) (C2/7)
15Amaranthus powelliiPowell Amaranth5176
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