FLIXWEED (Descurainia sophia) with GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE ) Inhibition of Acetolactate Synthase
MUTATION: PROLINE 197 to ALANINE
Flixweed (Descurainia sophia) is a dicot plant in the brassicaceae family. A single amino acid substitution from Proline 197 to Alanine has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.		Flixweed

Chemical Family	Example Herbicide	Resistance Level
Imidazolinones	Imazethapyr	Not Determined
Pyrimidinyl benzoates	Bispyribac-Na	Not Determined
Sulfonylureas	Chlorsulfuron	Resistant > 10 fold
Triazolopyrimidine - Type 1	Chloransulam-methyl	Not Determined
Triazolinones	Flucarbazone-Na	Not Determined

REFERENCES

Cui HaiLan ; Zhang ChaoXian ; Wei ShouHui ; Zhang HongJun ; Li XiangJu ; Zhang YanQiu ; Wang GuiQi. 2011. Acetolactate synthase gene proline (197) mutations confer tribenuron-methyl resistance in flixweed (Descurainia sophia) populations from China. Weed Science 59 : 376 - 379.

The molecular basis of resistance to tribenuron-methyl, an acetolactate synthase (ALS) - inhibiting herbicide was investigated in four resistant (R) and three susceptible (S) flixweed populations. The resistance level in the R populations was assessed in whole-plant pot experiments in a greenhouse, and resistance indices ranged from 723 to 1422. The ALS genes of the three S populations and four R populations were cloned and sequenced, and the full coding sequence of the ALS gene of flixweed was 2,004 bp. The sequences of the ALS genes of the three S populations collected from Shaanxi, Gansu, and Tianjin were identical. Comparison of the ALS gene sequences of the S and R populations with Arabidopsis revealed that proline at position 197 of the ALS gene was substituted by leucine in R population SSX-2, by alanine in R population SSX-3, and by serine in R populations TJ-2 and GS-2. In another study of two R flixweed populations from Hebei and Shaanxi, resistance was also related to mutation at position 197 of the ALS gene. Both studies confirmed tribenuron-methyl resistance in flixweed in China, with the resistance mechanism being conferred by specific ALS point mutations at amino acid position 197..

This case was entered by Patrick Tranel Email: tranel@illinois.edu

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