INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

SHORTAWN FOXTAIL (Alopecurus aequalis) with GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE ) Inhibition of Acetolactate Synthase

MUTATION: PROLINE 197 to THREONINE

Shortawn Foxtail (Alopecurus aequalis) is a monocot plant in the poaceae family. A single amino acid substitution from Proline 197 to Threonine has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.		Shortawn Foxtail

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

NOTE

Resistance was relatively low (<10x) to all herbicides evaluated, but resistance to SUs and TPs > IMIs.

REFERENCES

Xia, W., L. Pan, J. Li, Q. Wang, Y. Feng, and L. Dong. . 2015. Molecular basis of ALS- and/or ACCase-inhibitor resistance in shortawn foxtail (Alopecurus aequalis) Sobol.). Pesticide Biochemistry and Physiology 122 : 76 - 80.

Alopecurus aequalis, a predominant weed species in wheat and oilseed rape fields, can no longer be controlled by mesosulfuron-methyl application after continuous use over several years. Based on dose–response studies, the putative resistant populations, JTJY-1 and JHHZ-1, were found to be resistant to mesosulfuron-methyl, with resistance index values of 5.5 and 14, respectively. Sensitivity assays of the mesosulfuron-methyl-resistant populations to other herbicides revealed that the JTJY-1 population had moderate or high cross resistance to sulfonylureas (SUs) and triazolopyrimidines (TPs), but displayed a low level resistance to imidazolinones (IMIs). JTJY-1 also had high multi-resistance to ACCase inhibitors, but remained susceptible to photosystem II inhibitors. The JHHZ-1 population was resistant to all ALS inhibitors tested, but was sensitive to ACCase inhibitors and photosystem II inhibitors. To clarify the molecular basis of resistance in JTJY-1 and JHHZ-1 population, the ALS and ACCase gene were sequenced. Two ALS mutations (Pro-197-Thr or Trp-574-Leu) were detected in the mesosulfuron-methyl-resistant plants. The ACCase gene analysis revealed that the resistant JTJY-1 population had an Ile-1781-Leu mutation. Furthermore, the presence of two different target site resistance (TSR) mechanisms (ALS and ACCase mutations) existing simultaneously in individual A. aequalis was firstly documented in the presented study..

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

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