SHEPHERD'S-PURSE (Capsella bursa-pastoris) with GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE ) Inhibition of Acetolactate Synthase
MUTATION: PROLINE 197 to HISTIDINE
Shepherd's-purse (Capsella bursa-pastoris) is a dicot plant in the brassicaceae family. A single amino acid substitution from Proline 197 to Histidine has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.		Shepherd's-purse

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 ; Li XiangJu ; Wang GuiQi ; Wang JianPing ; Wei ShouHui ; Cao HongYu. 2012. Acetolactate synthase proline (197) mutations confer tribenuron-methyl resistance in Capsella bursa-pastoris populations from China. Pesticide Biochemistry and Physiology 102 : 229 - 232.

The increasing use of AHAS-inhibiting herbicides has resulted in evolved resistance in key dicot weeds infesting cereal cropping systems worldwide. Shepherd's purse (Capsellabursa-pastoris) is a common dicot weed species in wheat in China with populations that have evolved resistance to the AHAS herbicide tribenuron-methyl. The seeds of eight resistant populations were collected from wheat fields and one susceptible population from road side in Hebei province of China. All eight populations showed high level resistance to tribenuron-methyl with resistance indices of over 100 fold based on whole plant dose response assays in the greenhouse. Comparison of the AHAS gene sequences of the susceptible and resistant populations with Arabidopsis revealed that proline at position 197 of the AHAS gene was substituted by threonine in population CAPBU-HB-2, serine in populations CAPBU-HB-3, CAPBU-HB-4, CAPBU-HB-5, and CAPBU-HB-6, leucine in population CAPBU-HB-7 and CAPBU-HB-8, histidine in population CAPBU-HB-9. The study confirmed tribenuron-methyl resistance in shepherd's purse in Hebei province of China due to target site mutations at AHAS codon position 197..

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

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