International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Arabidopsis thaliana)

PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)

United Kingdom, Cambridgeshire
Mouse-ear Cress (Arabidopsis thaliana) is a dicot weed in the Brassicaceae family.  In United Kingdom this weed first evolved resistance to Group 5 (Legacy C1 C2) herbicides in 1988 and infests Railways.   Group 5 (Legacy C1 C2) herbicides are known as PSII inhibitors - Serine 264 Binders (Inhbition of Photosynthesis at PSll - Serine 264 Binders ).  Research has shown that these particular biotypes are resistant to atrazine and they may be cross-resistant to other Group 5 (Legacy C1 C2) 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 Dec 15, 2013 )

Common NameMouse-ear Cress
SpeciesArabidopsis thaliana
GroupPSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
LocationUnited Kingdom, Cambridgeshire
Contributors - (Alphabetically)Pádraic Flood 
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Pádraic Flood
The original accession was collected from a railway line in England in 1988 by a Prof Paul Williams. Atrazine stopped being sprayed by British rail back in 1992, last year (2012) I happened to be passing by and decided to check if the resistant population was still there. And indeed it was, I was quite excited that even with such a photosynthetic cost the resistance has persisted in the absence of the herbicide for 20 years. I have since returned and sampled more extensively and have found that the resistance has spread over a 60km radius along railway lines. Right now I am writing this up as a chapter in my thesis but plan to return this June and continue sampling with the aim being to identify the source population and chart the spread of the mutation along the railway lines. 

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Pádraic Flood
Follow up research on this particular case of resistance has shown that it had a single origin and has spread in excess of 400km along railway tracks and is still abundant in the population in spite of triazines being discontinued since 1992. This shows the lasting potential of herbicide resistance and its potential to have long term effects on genetic diversity in wild populations. Further information can be found here: Flood Pádraic J, van Heerwaarden J, Becker F, de Snoo CB, Harbinson J, Aarts Mark GM (2016) Whole-Genome Hitchhiking on an Organelle Mutation. Current Biology 26: 1306-1311

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Pádraic Flood
Mohamed E.E., G.C. Rodrigues, J.J.S. van Rensen, J.F.H. Snel, Hans J.H.A. Dassen, M. Koornneef, M.A.K. Jansen, M.G.M. Aarts and D. Vreugdenhil. 2005.  Altered photosynthetic performance of a natural Arabidopsis accession is associated with atrazine resistance. Journal of Experimental Botany, Vol. 56, No. 416, pp. 1625–1634.
Natural variation for photosynthetic traits was studied by determining chlorophyll fluorescence parameters in a collection of Arabidopsis accessions. This screen revealed only one single accession(Ely),exhibiting photosynthetic characteristics markedly different from all others, while a few lines showed small but significant variation. Detailed genetic and physiological analyses showed reduced fitness for Ely compared with the standard laboratory strain Ler for various growth parameters. At low temperature (15 8C), Ely had a higher electron transport rate than Ler, indicating increased photosystem II efficiency under this condition, while at high temperature (30 8C) the opposite was observed.  Ely had a high sensitivity to UV-B radiation compared with Ler and was atrazine resistant. This atrazine-resistance and related chlorophyll fluorescence traits were maternally inherited, pointing towards chloroplast-located gene(s). Definite proof that Ely is atrazine-resistant was obtained by sequencing the psbA gene, encoding the D1 protein of photosystem II, revealing a point mutation causing the same amino acid change as found in other atrazine-resistant species. Additional nuclear encoded genetic variation was also present, as was concluded from the small but significant differences in phenotype between Ely and its reciprocal crosses with Ler. It was concluded that the photosynthetic yield is highly conserved and that only severe selection pressure results in marked variations in photosynthetic performance.

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Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Mouse-ear Cress biotype with this Mouse-ear Cress 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 5 resistant Mouse-ear Cress indicate that the inheritance is determined by a one gene, dominant, cytoplasmic 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 5 (Legacy C1 C2) resistant Mouse-ear Cress from United Kingdom 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

Researchers have indicated that Group 5/C1 C2 resistant Mouse-ear Cress is ecologically less fit than normal susceptible Mouse-ear Cress.  There may be a note below or an article discussing the fitness of this biotype in the Fact Sheets and Other Literature
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Postdoctoral researcher
Max Planck Institute for Plant Breeding Research
Carl-von-linne-weg 10
Cologne, 50823, Rhein
Email Pádraic Flood


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in United Kingdom have been instrumental in providing you this information. Particular thanks is given to Pádraic Flood for providing detailed information.
Herbicide Resistant Mouse-ear Cress Globally
(Arabidopsis thaliana)
Herbicide Resistant Mouse-ear Cress Globally
(Arabidopsis thaliana)
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Herbicide Resistant Mouse-ear Cress Globally
(Arabidopsis thaliana)
#CountryFirstYearSituationActive IngredientsSite of Action
1 United KingdomUnited Kingdom 1988 Railways atrazine 44 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
292Arabidopsis thalianaMouse-ear Cress7762
2 United States (Virginia) United StatesVirginia2015 Wheat flucarbazone-Na, mesosulfuron-methyl, pyroxsulam, thifensulfuron-methyl, and tribenuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
292Arabidopsis thalianaMouse-ear Cress21232
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