Skip to main content Accessibility help

Molecular Basis of Resistance to Herbicides Inhibiting Acetolactate Synthase in Two Rigid Ryegrass (Lolium rigidum) Populations from Australia

  • Shiv S. Kaundun (a1), Richard P. Dale (a1) and Géraldine C. Bailly (a1) (a2)


Acetolactate Synthase- (ALS) inhibiting herbicides are important components for the control of ryegrass species infesting cereal-cropping systems worldwide. Although resistance to ALS herbicides in ryegrasses has evolved more than 25 yr ago, few studies have been dedicated to elucidate the molecular mechanisms involved. To this end, we have investigated the molecular basis of chlorsulfuron, sulfometuron-methyl, and imazapyr resistance in AUS5 and AUS23, two ryegrass populations from Australia. Comparison between whole-plant herbicide assays and DNA sequencing results showed that resistance to the nonmetabolizable herbicide sulfometuron-methyl was associated with four different proline mutations at ALS codon position 197 (P197) in AUS23. In addition to three P197 amino acid changes impacting on the efficacies of the two sulfonylurea herbicides, the tryptophan to leucine target-site mutation at ALS codon position 574 (W574L) was present in AUS5, conferring resistance to both sulfometuron-methyl and imazapyr. The samples were also characterized by non target-site-based resistance impacting on the metabolizable herbicide chlorsulfuron only. Interestingly, compound mutant heterozygotes threonine/serine at ALS position 197, and plants with double mutations at positions 197 and 574 were detected, thus reflecting the ability of this outcrossing species to accumulate mutant alleles. Whole-plant dose-response assays conducted on predetermined wild-type and mutant genotypes originating from the same populations allowed for a more precise estimation of the dominant and very high levels of resistance associated with the proline to serine target-site mutation at ALS codon position 197 (P197S) and W574L mutations. The two highly efficient polymerase chain reaction- (PCR) based derived cleaved amplified polymorphic sequence (dCAPS) markers developed here will allow for quick confirmation of 197 and 574 ALS target-site resistance in ryegrass species field samples and also contribute to identify populations characterized by other likely resistance mechanisms in this important weed species.


Corresponding author

Corresponding author's E-mail:


Hide All
Christopher, J. T., Powles, S. B., and Holtum, J.A.M. 1992. Resistance to acetolactate synthase-inhibiting herbicides in annual ryegrass (Lolium rigidum) involves at least two mechanisms. Plant Physiol. 100:19091913.
Dayhoff, M. O., Schwartz, R. M., and Orcutt, B. C. 1978. A model of evolutionary change in proteins. Pages 345352 in Dayhoff, M. O., ed. Atlas of Protein Sequence and Structure. Washington, D.C. National Biomedical Research Foundation.
Delye, C., Boucansaud, K., Pernin, F., and Le Corre, V. 2009. Variation in the gene encoding acetolactate-synthase in Lolium species and proactive detection of mutant, herbicide-resistant alleles. Weed Res. 49:326336.
Delye, C., Pernin, F., and Michel, S. 2011. ‘Universal’ PCR assays detecting mutations in acetyl-coenzyme A carboxylase or acetolactate synthase that endow herbicide resistance in grass weeds. Weed Res. 51:353362.
Heap, I. M. 2011. International Survey of Herbicide-Resistant Weeds. Accessed: November 10, 2011.
Kaundun, S. S., Dale, R., and Lycett, A. 2006. Molecular basis of acetolactate synthase (ALS) inhibitor resistance in two rye grass (Lolium rigidum) populations. Page 102 in Proceedings of the Weed Science Society of America. Publisher: New York Proc. Weed Sci. Soc. am. [Abstract].
Kaundun, S. S. and Windass, J. D. 2006. Derived cleaved amplified polymorphic sequence, a simple method to detect a key point mutation conferring acetyl CoA carboxylase inhibitor herbicide resistance in grass weeds. Weed Res. 46:3439.
Laplante, J., Rajcan, I., and Tardif, F. J. 2009. Multiple allelic forms of acetohydroxyacid synthase are responsible for herbicide resistance in Setaria viridis . Theor. Appl. Genet. 119:577585.
Massa, D., Krenz, B., and Gerhards, R. 2011. Target-site resistance to ALS-inhibiting herbicides in Apera spica-venti populations is conferred by documented and previously unknown mutations. Weed Res. 51:294303.
Moss, S. R., Marshall, R., Hull, R., and Alarcon-Reverte, R. 2011. Current status of herbicide-resistant weeds in the United Kingdom. Pages 110 in Proceedings of the Aspects of Applied Biology. Crop Protection in Southern Britain. Warwick, UK Association of Applied Biologists.
Neff, M. M., Neff, J. D., Chory, J., and Pepper, A. E. 1998. dCAPS, a simple technique for the genetic analysis of single nucleotide polymorphisms: experimental applications in Arabidposis thaliana genetics. Plant J. 14:387392.
Neff, M. M., Turk, E., and Kalishman, M. 2002. Web-based primer design for single nucleotide polymorphism analysis. Trends Genet. 18:613615.
Owen, M. J., Walsh, M. J., Llewellyn, R. S., and Powles, S. B. 2007. Widespread occurrence of multiple herbicide resistance in Western Australian annual ryegrass (Lolium rigidum) populations. Aust. J. Agric. Res. 58:711718.
Park, K. W. and Mallory-Smith, C. A. 2004. Physiological and molecular basis for ALS inhibitor resistance in Bromus tectorum biotypes. Weed Res. 44:7177.
Powles, S. and Yu, Q. 2010. Evolution in action: plants reistant to herbicides. Annu. Rev. Plant Biol. 61:317–47.
R Development Core Team. 2009. R: A language and environment for statistical computing. Vienna, Austria R Foundation for Statistical Computing. Accessed: October 5, 2009.
Ray, T. B. 1984. Site of action of chlorsulfuron: inhibition of valine and isoleucine biosynthesis in plants. Plant Physiol. 75:827831.
Ritz, C. and Streibig, J. C. 2005. Bioassay analysis using R. J. Stat. Softw. 12: issue 5.
Sibony, M., Michel, A., Haas, H. U., Rubin, B., and Hurle, K. 2001. Sulfometuron-resistant Amaranthus retroflexus: cross-resistance and molecular basis for resistance to acetolactate synthase-inhibiting herbicides. Weed Res. 41:509522.
Tan, M. K., Preston, C., and Wang, G. X. 2007. Molecular basis of multiple resistance to ACCase-inhibiting and ALS-inhibiting herbicides in Lolium rigidum . Weed Res. 47:534541.
Tranel, P. J. and Wright, T. R. 2002. Resistance of weeds to ALS-inhibiting herbicides: what have we learned? Weed Sci. 50:700712.
Yu, Q., Han, H., and Powles, S. B. 2008. Mutations of the ALS gene endowing resistance to ALS-inhibiting herbicides in Lolium rigidum populations. Pest Manag. Sci. 64:12291236.
Yu, Q., Han, H., Vila-Aiub, M., and Powles, S. B. 2010. AHAS herbicide resistance endowing mutations: effect on AHAS functionality and plant growth. J. Exp. Bot. 61:39253934.



Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed