WATER STARWORT (Myosoton aquaticum) with GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE ) Inhibition of Acetolactate Synthase
MUTATION: PROLINE 197 to SERINE
Water Starwort (Myosoton aquaticum) is a dicot plant in the caryophyllaceae family. A single amino acid substitution from Proline 197 to Serine has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.		Water Starwort

Chemical Family	Example Herbicide	Resistance Level
Imidazolinones	Imazethapyr	Susceptible
Pyrimidinyl benzoates	Bispyribac-Na	Resistant > 10 fold
Sulfonylureas	Chlorsulfuron	Resistant > 10 fold
Triazolopyrimidine - Type 1	Chloransulam-methyl	Intermediate Resistance < 10 fold
Triazolinones	Flucarbazone-Na	Resistant > 10 fold

REFERENCES

Liu WeiTang ; Bi YaLing ; Li LingXu ; Yuan GuoHui ; Du Long ; Wang JinXin. 2013. Target-site basis for resistance to acetolactate synthase inhibitor in Water chickweed (Myosoton aquaticum L.). Pesticide Biochemistry and Physiology 107 : 50 - 54.

Water chickweed is a widespread and competitive winter annual or biennial weed of wheat in China. One Water chickweed population (HN02) resistant to several acetolactate synthase (ALS) inhibitors was found in Henan province of China. Whole-plant bioassays showed that HN02 was high resistance to tribenuron (292.05-flod). In vitro ALS assays revealed that resistance was due to reduced sensitivity of the ALS enzyme to tribenuron. The I₅₀ value for HN02 was 85.53 times greater respectively than that of susceptible population (SD05). This altered ALS sensitivity in the resistant population was due to a mutation in the ALS gene resulting in a Pro197 to Ser substitution. Cross-resistance experiments indicated that HN02 exhibited various resistance patterns to pyrithiobac-sodium, florasulam and pyroxsulam, without resistance to imazethapyr. This is the first report of tribenuron-resistant Water chickweed in Henan province of China, target-site based resistance was established as being due to an insensitive form of ALS, resulting from a Pro to Ser substitution at amino acid position 197 in the ALS gene..

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

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