Skip to main content Accessibility help

Glyphosate-Resistant Italian Ryegrass (Lolium multiflorum) in California: Distribution, Response to Glyphosate, and Molecular Evidence for an Altered Target Enzyme

  • Marie Jasieniuk (a1), Riaz Ahmad (a1), Anna M. Sherwood (a1), Jeffrey L. Firestone (a1), Alejandro Perez-Jones (a2), W. Thomas Lanini (a1), Carol Mallory-Smith (a2) and Zachary Stednick (a1)...


Selection by herbicides has resulted in widespread evolution of herbicide resistance in agricultural weeds. In California, resistance to glyphosate was first confirmed in rigid ryegrass in 1998. Objectives of this study were to determine the current distribution and level of glyphosate resistance in Italian ryegrass, and to assess whether resistance could be due to an altered target site. Seeds were sampled from 118 populations and seedlings were treated with glyphosate at 866 g ae ha−1. Percentage of survivors ranged from 5 to 95% in 54 populations. All plants from 64 populations died. One susceptible (S) population, four putatively resistant (R) populations, and one S accession from Oregon were used for pot dose–response experiments, shikimic acid analyses, and DNA sequencing. Seedlings were treated with glyphosate at eight rates, ranging from 108 to 13,856 g ae ha−1. Shoot biomass was evaluated 3 wk after treatment and fit to a log-logistic regression equation. On the basis of GR50 (herbicide rate required to reduce growth by 50%) values, seedlings from putatively R populations were roughly two to 15 times more resistant to glyphosate than S plants. Shikimic acid accumulation was similar in all plants before glyphosate treatment, but at 4 and 7 DAT, S plants from California and Oregon accumulated approximately two and three times more shikimic acid, respectively, than R plants. Sequencing of a cDNA fragment of the EPSPS coding region revealed two different codons, both of which encode proline at amino acid position 106 in S individuals. In contrast, all R plants sequenced exhibited missense mutations at site 106. Plants from one population revealed a mutation resulting in a proline to serine substitution. Plants from three R populations exhibited a mutation corresponding to replacement of proline with alanine. Our results indicate that glyphosate resistance is widespread in Italian ryegrass populations of California, and that resistance is likely due to an altered target enzyme.


Corresponding author

Corresponding author's E-mail:


Hide All
Baerson, S. R., Rodriguez, D. J., Tran, M., Feng, Y., Biest, N. A., and Dill, G. M. 2002. Glyphosate-resistant goosegrass. Identification of a mutation in the target enzyme 5-enolpyruvylshikimate-3-phosphate synthase. Plant Physiol. 129:12651275.
Baylis, A. D. 2000. Why glyphosate is a global herbicide: strengths, weaknesses and prospects. Pest Manag. Sci. 56:299308.
Christoffers, M. J. 1999. Genetic aspects of herbicide-resistant weed management. Weed Technol. 13:647652.
Comai, L., Sen, L. C., and Stalker, D. M. 1983. An altered aroA gene product confers resistance to the herbicide glyphosate. Science. 221:370371.
Cromartie, T. H. and Polge, N. D. 2000. An improved assay for shikimic acid and its use as a monitor for the activity of sulfosate. Proc. Weed Sci. Soc. Am. 40:291.
Gressel, J. 2002. Evolution of resistance to herbicides. Pages 78121. in Gressel, J. Molecular Biology of Weed Control. New York Taylor & Francis.
Heap, I. 2007. International Survey of Herbicide Resistant Weeds. Accessed: November 6, 2007.
Herrmann, K. M. and Weaver, L. M. 1999. The shikimate pathway. Annu. Rev. Plant Physiol. Mol. Biol. 50:473503.
Jasieniuk, M., Brûlé-Babel, A. L., and Morrison, I. N. 1996. The evolution and genetics of herbicide resistance in weeds. Weed Sci. 44:176193.
Jaworski, E. G. 1982. Mode of action of N-phosphonomethylglycine: inhibition of aromatic amino acid biosynthesis. J. Agric. Food Chem. 20:11951198.
Lee, L. J. and Ngim, J. 2000. A first report of glyphosate-resistant goosegrass (Eleusine indica (L) Gaertn) in Malaysia. Pest Manag. Sci. 56:336339.
Lorraine-Colwill, D. F., Powles, S. B., Hawkes, T. R., Hollinshead, P. H., Warner, S. A. J., and Preston, C. 2002. Investigations into the mechanism of glyphosate resistance in Lolium rigidum . Pestic. Biochem. Physiol. 74:6272.
Maxwell, B. D., Roush, M. L., and Radosevich, S. R. 1990. Predicting the evolution and dynamics of herbicide resistance in weed populations. Weed Technol. 4:213.
Ng, C. H., Wickneswary, R., Salmijah, S., Teng, Y. T., and Ismail, B. S. 2003. Gene polymorphisms in glyphosate-resistant and -susceptible biotypes of Eleusine indica from Malaysia. Weed Res. 43:108115.
Ng, C. H., Wickneswary, R., Salmijah, S., Teng, Y. T., and Ismail, B. S. 2004. Glyphosate resistance in Eleusine indica (L.) Gaertn. from different origins and polymerase chain reaction amplification of specific alleles. Aust. J. Agric. Res. 55:407414.
Padgette, S. R., Re, D. B., Gasser, C. S., Eichholtz, D. A., Frazier, R. B., Hironaka, C. M., Levine, E. B., Shah, D. M., Fraley, R. T., and Kishore, G. M. 1991. Site-directed mutagenesis of a conserved region of the 5-enolpyruvylshikimate-3-phosphate synthase active site. J. Biol. Chem. 266:22,36422,369.
Pedersen, B. P., Neve, P., Andreasen, C., and Powles, S. B. 2007. Ecological fitness of a glyphosate-resistant Lolium rigidum population: growth and seed production along a competition gradient. Basic Appl. Ecol. 8:258268.
Perez, A. and Kogan, M. 2003. Glyphosate-resistant Lolium multiflorum in Chilean orchards. Weed Res. 43:1219.
Perez-Jones, A., Park, K-W., Colquhoun, J., Mallory-Smith, C., and Shaner, D. 2005. Identification of glyphosate-resistant Italian ryegrass (Lolium multiflorum) in Oregon. Weed Sci. 53:775779.
Perez-Jones, A., Park, K-W., Polge, N., Colquhoun, J., and Mallory-Smith, C. A. 2007. Investigating the mechanisms of glyphosate resistance in Lolium multiflorum . Planta. 226:395404.
Powles, S. B., Lorraine-Colwill, D. F., Dellow, J. J., and Preston, C. 1998. Evolved resistance to glyphosate in rigid ryegrass (Lolium rigidum) in Australia. Weed Sci. 46:604607.
Powles, S. B. and Preston, C. 2006. Evolved glyphosate resistance in plants: biochemical and genetic basis of resistance. Weed Technol. 20:282289.
Pratley, J., Urwin, N., Stanton, R., Baines, P., Broster, J., Cullis, K., Schafer, D., Bohn, J., and Krueger, R. 1999. Resistance to glyphosate in Lolium rigidum. I. Bioevaluation. Weed Sci. 47:405411.
Preston, C. and Wakelin, A. M. 2008. Resistance to glyphosate from altered herbicide translocation patterns. Pest Manag. Sci. Early View, DOI: 10.1002/ps.1489.
Seefeldt, S. S., Jensen, J. E., and Fuerst, E. P. 1995. Log-logistic analysis of herbicide dose–response relationships. Weed Technol. 9:218225.
Siehl, D. L. 1997. Inhibitors of EPSPS synthase, glutamine synthetase and histidine synthesis. Pages 3767. in Roe, R. M., Burton, J. D., and Kuhr, R. J. Herbicide Activity: Toxicology, Biochemistry and Molecular Biology. Amsterdam IOS.
Simarmata, M., Kaufmann, J. E., and Penner, D. 2003. Potential basis of glyphosate resistance in California rigid ryegrass (Lolium rigidum). Weed Sci. 51:678682.
Singh, B. K. and Shaner, D. L. 1998. Rapid determination of glyphosate injury to plants and identification of glyphosate-resistant plants. Weed Technol. 12:527530.
Steinrücken, H. C. and Amrhein, N. 1980. The herbicide glyphosate is a potent inhibitor of 5-enolpyruvyl-shikimic acid 3-phosphate synthase. Biochem. Biophys. Res. Commun. 94:12071212.
Streibig, J. C. 1988. Herbicide bioassay. Weed Res. 28:479484.
Streibig, J. C., Rudemo, M., and Jensen, J. E. 1993. Dose–response curves and statistical models. Pages 2956. in Streibig, J. C. and Kudsk, P. Herbicide Bioassays. Boca Raton, FL CRC.
Vila-Aiub, M. M., Balbi, M. C., Gundel, P. E., Ghersa, C. M., and Powles, S. B. 2007. Evolution of glyphosate-resistant Johnsongrass (Sorghum halepense) in glyphosate-resistant soybean. Weed Sci. 55:566571.
Wakelin, A. M., Lorraine-Colwill, D. F., and Preston, C. 2004. Glyphosate resistance in four different populations of Lolium rigidum is associated with reduced translocation of glyphosate to meristematic zones. Weed Res. 44:453459.
Wakelin, A. M. and Preston, C. 2006. A target-site mutation is present in a glyphosate-resistant Lolium rigidum population. Weed Res. 46:432440.
Woodburn, A. T. 2000. Glyphosate: production, pricing and use worldwide. Pest Manag. Sci. 56:309312.
Yu, Q., Cairns, A., and Powles, S. 2007. Glyphosate, paraquat and ACCase multiple herbicide resistance evolved in a Lolium rigidum biotype. Planta. 225:499513.


Glyphosate-Resistant Italian Ryegrass (Lolium multiflorum) in California: Distribution, Response to Glyphosate, and Molecular Evidence for an Altered Target Enzyme

  • Marie Jasieniuk (a1), Riaz Ahmad (a1), Anna M. Sherwood (a1), Jeffrey L. Firestone (a1), Alejandro Perez-Jones (a2), W. Thomas Lanini (a1), Carol Mallory-Smith (a2) and Zachary Stednick (a1)...


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