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REDROOT PIGWEED (Amaranthus retroflexus)
with GROUP B/2 resistance: (ALS INHIBITORS)
Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)

MUTATION: SERINE 653 to THREONINE

Redroot Pigweed (Amaranthus retroflexus) is a dicot plant in the amaranthaceae family. A single amino acid substitution from Serine 653 to Threonine has led to resistance to ALS inhibitors as indicated in the table below.

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Redroot Pigweed

Chemistry	Example	Resistance
Imidazolinones	Imazethapyr	Resistant > 10 fold
Pyrimidinylthiobenzoates	Bispyribac-Na	Not Determined
Sulfonylureas	Chlorsulfuron	Susceptible
Triazolopyrimidines	Chloransulam-methyl	Not Determined
Sulfonylaminocarbonyltriazolinone	Flucarbazone-Na	Not Determined

NOTES

REFERENCES

McNaughton, K. E., E. Lee A., and F. Tardif J. (2001). Mutations in the ALS gene confering resistance to group II herbicides in redroot pigweed (Amaranthus retroflexus) and green pigweed (A. powellii). Weed Science Society of America Abstracts , 41 : 97.