INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

COMMON SUNFLOWER (Helianthus annuus) with GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE ) Inhibition of Acetolactate Synthase

MUTATION: PROLINE 197 to LEUCINE

Common Sunflower (Helianthus annuus) is a dicot plant in the asteraceae family. A single amino acid substitution from Proline 197 to Leucine has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.		Common Sunflower

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

Kolkman, J. M. ; Slabaugh, M. B. ; Bruniard, J. M. ; Berry, S. ; Bushman, B. S. ; Olungu, C. ; Maes, N. ; Abratti, G. ; Zambelli, A. ; Miller, J. F. ; Leon, A. ; Knapp, S. J.. 2004. Acetohydroxyacid synthase mutations conferring resistance to imidazolinone or sulfonylurea herbicides in sunflower. Theoretical and Applied Genetics 109 : 1147 - 1159.

Wild biotypes of cultivated sunflower (Helianthus annuus L.) are weeds in corn (Zea mays L.), soybean (Glycine max L.), and other crops in North America, and are commonly controlled by applying acetohydroxyacid synthase (AHAS)-inhibiting herbicides. Biotypes resistant to two classes of AHAS-inhibiting herbicides - imidazolinones (IMIs) or sulfonylureas (SUs) - have been discovered in wild sunflower populations (ANN-PUR and ANN-KAN) treated with imazethapyr or chlorsulfuron, respectively. The goals of the present study were to isolate AHAS genes from sunflower, identify mutations in AHAS genes conferring herbicide resistance in ANN-PUR and ANN-KAN, and develop tools for marker-assisted selection (MAS) of herbicide resistance genes in sunflower. Three AHAS genes (AHAS1, AHAS2, and AHAS3) were identified, cloned, and sequenced from herbicide-resistant (mutant) and -susceptible (wild type) genotypes. We identified 48 single-nucleotide polymorphisms (SNPs) in AHAS1, a single six-base pair insertion-deletion in AHAS2, and a single SNP in AHAS3. No DNA polymorphisms were found in AHAS2 among elite inbred lines. AHAS1 from imazethapyr-resistant inbreds harbored a C-to-T mutation in codon 205 (Arabidopsis thaliana codon nomenclature), conferring resistance to IMI herbicides, whereas AHAS1 from chlorsulfuron-resistant inbreds harbored a C-to-T mutation in codon 197, conferring resistance to SU herbicides. SNP and single-strand conformational polymorphism markers for AHAS1, AHAS2, and AHAS3 were developed and genetically mapped. AHAS1, AHAS2, and AHAS3 mapped to linkage groups 2 (AHAS3), 6 (AHAS2), and 9 (AHAS1). The C/T SNP in codon 205 of AHAS1 cosegregated with a partially dominant gene for resistance to IMI herbicides in two mutant × wild-type populations. The molecular breeding tools described herein create the basis for rapidly identifying new mutations in AHAS and performing MAS for herbicide resistance genes in sunflower..

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

Heap, I. The International Herbicide-Resistant Weed Database. Online. Monday, September 28, 2026. Available at www.weedscience.org

Copyright © 1993- 2026 WeedScience.org. All rights reserved.

Normal scientific reference, citation, and limited use of individual records are permitted. Automated or systematic data extraction, bulk copying, database replication or synchronization, AI or machine-learning use, predictive-model development, redistribution, and commercial reuse are not permitted without prior written permission from WeedScience.org.

See our Data Use and AI Policy.