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KOCHIA (Kochia scoparia)
with GROUP B/2 resistance: (ALS INHIBITORS)
Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)

MUTATION: PROLINE 197 to SERINE

Kochia (Kochia scoparia) is a dicot plant in the chenopodiaceae family. A single amino acid substitution from Proline 197 to Serine has led to resistance to ALS inhibitors as indicated in the table below.

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Kochia

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

NOTES

REFERENCES

Guttieri, M. J., C. V. Eberlein, and D. C. Thill. (1995). Diverse mutations in the acetolactate synthase gene confer chlorsulfuron resistance in kochia (Kochia scoparia) biotypes. Weed Science , 43 (2) : 175-178.

The DNA sequence of an 83-base pair region of the acetolactate synthase (ALS) gene was compared for 10 chlorsulfuron-resistant (R) and 3 chlorsulfuron-susceptible (S) kochia biotypes. Point mutation in the codon for the proline residue at position 173 in Domain A of the ALS protein was observed in 7 of 10 R biotypes. Among these 7 R biotypes, mutation to threonine, serine, arginine, leucine, glutamine and alanine was identified. The mechanism of resistance was determined for the R biotypes that did not have mutation in Domain A; all were resistant due to modified ALS, which indicated that at least one non-Domain A mutation site for resistance exists in kochia. Sequence results indicated that multiple mutations for resistance have occurred and that geographically widespread ALS-inhibitor resistance in kochia is not the result of a single resistance allele.