SILKY WINDGRASS (Apera spica-venti) with GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE ) Inhibition of Acetolactate Synthase
MUTATION: TRYPTOPHAN 574 to METHIONINE
Silky Windgrass (Apera spica-venti) is a monocot plant in the poaceae family. A single amino acid substitution from Tryptophan 574 to Methionine has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.		Silky Windgrass

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

Katerina Hamouzová, Pavlíina Košnarová, Jaroslav Salava, Josef Soukup and Pavel Hamouza. 2013. Mechanisms of resistance to acetolactate synthase-inhibiting herbicides in populations ofApera spica-ventifrom the Czech Republic. Pest Management Science : .

BACKGROUND: This study investigates the mechanisms of resistance to acetolactate synthase-inhibiting herbicides in populations of Apera spica-venti (L.) P.B. from the Czech Republic.

RESULTS: The proportion of resistance due to mutant acetolactate synthase (ALS) alleles was estimated by genotyping individuals from each of three populations for the eight ALS mutations known to confer resistance. Four resistance-conferring ALS mutations were identified: Pro-197-Ala, Pro-197-Thr, Trp-574-Leu and previously unreported Trp-574-Met substitution. Two populations (R1, R3) have amino acid substitution at positions Pro-197 and Trp-574. Individuals from the R3 population had two different resistance alleles. In the R2 population, only the resistant Trp-574-Met substitution was detected. Ten other single point mutations were identified, but these were not related to resistance.

The cytochrome malathion decreased chlorsulfuron resistance in the resistant populations that were examined. Although malathion increased mortality, the GR50 values were too high to conclude that non-target-based mechanism was the main one for the resistance in Apera spica-venti populations tested in this study.
CONCLUSIONS: Individuals of Apera spica-venti populations tested in this study possess the target-site ALS resistance mutation and an additional so far unknown resistance mechanism(s)..

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

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