REDROOT PIGWEED (Amaranthus retroflexus) with GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE ) Inhibition of Acetolactate Synthase
MUTATION: ASPARTATE 376 to GLUTAMATE
Redroot Pigweed (Amaranthus retroflexus) is a dicot plant in the amaranthaceae family. A single amino acid substitution from Aspartate 376 to Glutamate has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.		Redroot Pigweed

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

REFERENCES

Huang, Z., J. Chen, C. Zhang, H. Huang, S. Wei, X. Zhou, J. Chen, and X. Wang. 2016. Target-site basis for resistance to imazethapyr in redroot amaranth (Amaranthus retroflexus L.).. Pesticide Biochemistry and Physiology 128 : 10 - 15.

Experiments were conducted to confirm imazethapyr resistance in redroot amaranth (Amaranthus retroflexus L.) and study the target-site based mechanism for the resistance. Whole-plant response experiments revealed that the resistant (R) population exhibited 19.16 fold resistance to imazethapyr compared with the susceptible (S) population. In vitro ALS activity assay demonstrated that the imazethapyr I₅₀ value of the R population was 21.33 times greater than that of the S population. However, qRT-PCR analysis revealed that there is no difference in ALS gene expression between the R and S populations. Sequence analysis revealed an Asp-376-Glu substitution in ALS in the R population. In order to verify that the imazethapyr resistance was conferred by Asp-376-Glu mutation, the ALS-R and ALS-S genes were fused to the CaMV 35S promoter and introduced into Arabidopsis respectively. The expression of ALS-R in transgenic Arabidopsis plants exhibited 13.79 fold resistance to imazethapyr compared to ALS-S transgenic Arabidopsis..

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

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