HENBIT DEADNETTLE (Lamium amplexicaule) with GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE ) Inhibition of Acetolactate Synthase
MUTATION: PROLINE 197 to ARGININE
Henbit Deadnettle (Lamium amplexicaule) is a dicot plant in the lamiaceae family. A single amino acid substitution from Proline 197 to Arginine has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.		Henbit Deadnettle

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

REFERENCES

Varanasi, V. K., A. S. Godar, D. E. Peterson, D. Shoup, and M. Jugulam. 2016. A target-site point mutation in henbit (Lamium amplexicaule) confers high-level resistance to ALS-inhibitors.. Weed Science 64 : 231 - 239.

Henbit is a facultative broadleaf winter annual in the Lamiaceae family. Acetolactate synthase (ALS) inhibitors are primarily used to control a broad spectrum of weeds, including henbit. During 2012 to 2013, field applications of ALS-inhibiting herbicides were ineffective in controlling a henbit population from Marion County, KS (MCK). To confirm field-evolved resistance to ALS inhibitors, response of MCK henbit and a known susceptible henbit population from Kansas (DPS) to varying doses of three different ALS inhibitors were examined: chlorsulfuron, imazamox, and propoxycarbazone. Results of the dose–response experiments suggest that the MCK population is highly resistant to chlorsulfuron (resistance index [R/S] > 1,000) and propoxycarbazone (R/S = 331) but is susceptible to imazamox. A full-length ALS gene sequence obtained using the 5′- and 3′- rapid amplification of complementary DNA ends approach revealed a Pro₁₉₇ to Arg point mutation (a common mutation that confers resistance to sulfonylurea herbicides, e.g., chlorsulfuron) in the MCK henbit. No other known resistance-conferring mutations were found in the study. Evolved resistance to major classes of ALS inhibitors in the MCK henbit will reduce herbicide options for its control. To our knowledge, this is the first case of evolution of herbicide resistance in henbit..

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

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