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LOW FALSE PIMPERNEL (MAJOR) (Lindernia dubia var. major)
with GROUP B/2 resistance: (ALS INHIBITORS)
Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)

MUTATION: PROLINE 197 to SERINE

Low False Pimpernel (major) (Lindernia dubia var. major) is a dicot plant in the scrophulariaceae 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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Low False Pimpernel (major)

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

Uchino, A., and H. Watanabe (2002). Mutations in the acetolactate synthase genes of sulfonylurea-resistant biotypes of Lindernia spp. Weed Biology and Management , 2 () : 104-109.

Acetolactate synthase (ALS) is a key enzyme in the biosynthetic pathway of branched-chain amino acids. A mutation of the ALS gene causing amino acid substitution at the position of proline in Domain A makes ALS less sensitive to sulfonylureas, which are ALS-inhibiting herbicides. We cloned partial ALS genes from four Lindernia plants, L. dubia var. dubia, L. dubia var. major, L. micrantha and L. procumbens, for which biotypes resistant to sulfonylureas have been found in paddy fields. The clones were classified into two groups in each Lindernia plant: Als1 and Als2. Sequencing of the clones and alignment of deduced amino acid sequences with previously reported ALS of other species suggested that the cloned region contains an intron in both Als1 and Als2. Comparison of Als1 between resistant and susceptible biotypes showed that the proline of Domain A was replaced by alanine, serine or glutamine in all resistant biotypes of Lindernia plants, while it was conserved in all susceptible biotypes. This amino acid substitution in ALS encoded by Als1 is involved in the resistant mechanism of ALS to sulfonylurea in the four Lindernia plants.