INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

SILKY WINDGRASS (Apera spica-venti) with GROUP B/2 resistance: (ALS INHIBITORS) Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)

MUTATION: ALANINE 122 to VALINE

Silky Windgrass (Apera spica-venti) is a monocot plant in the poaceae family. A single amino acid substitution from Alanine 122 to Valine has led to resistance to ALS inhibitors as indicated in the table below.		Silky Windgrass

Chemical Family	Example Herbicide	Resistance Level
Imidazolinones	Imazethapyr	Not Determined
Pyrimidinylthiobenzoates	Bispyribac-Na	Not Determined
Sulfonylureas	Chlorsulfuron	Resistant > 10 fold
Triazolopyrimidines	Chloransulam-methyl	Not Determined
Sulfonylaminocarbonyltriazolinone	Flucarbazone-Na	Susceptible

NOTE

It is not clear whether this mutation is solely responsible for resistance.

REFERENCES

Krysiak, M. ; Gawron´ski, S. W. ; Adamczewski, K. ; Kierzek, R.. 2011. ALS gene mutations in Apera spica-venti confer broad-range resistance to herbicides. Journal of Plant Protection Research 51 : 261 - 267.

Several biotypes of wind bentgrass in Poland have been identified as being resistant to acetolactate synthase (ALS) inhibitors. We screened these weeds with chlorsulfuron and performed a whole-plant bioassay with a range of doses based on these four herbicides: chlorsulfuron, sulfosulfuron, propoxycarbazone-sodium and mesosulfuron-methyl+iodosulfuron-methyl-sodium mixture. Ten biotypes, diverse in their levels of resistance, were submitted for molecular tests. PCR amplification and sequencing of als domains demonstrated numerous single nucleotide polymorphisms. Nine biotypes showed non-synonymous substitutions in codon Pro₁₉₇, changing it to Ser or Thr. Mutation in Pro₁₉₇ conferred a high level of resistance to the tested herbicides. Analysis of four biotypes also revealed a substitution in the Ala₁₂₂ codon, changing it to Val. In one biotype this substitution was not accompanied by Pro₁₉₇ mutation and this biotype was resistant to chlorsulfuron and mesosulfuron+iodosulfuron, but not to sulfosulfuron or propoxycarbazone-sodium. Correspondence between mutations and levels of resistan ce to ALS inhibitors may support management of resistant weeds with the existing palette of herbicides..

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

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