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Investigations into glyphosate-resistant horseweed (Conyza canadensis): retention, uptake, translocation, and metabolism

  • Paul C. C. Feng, Minhtien Tran (a1), Tommy Chiu (a1), R. Douglas Sammons (a1), Gregory R. Heck (a1) and Claire A. CaJacob (a1)...


The mechanism of glyphosate resistance in horseweed was investigated. Eleven biotypes of putative sensitive (S) and resistant (R) horseweed were obtained from regions across the United States and examined for foliar retention, absorption, translocation, and metabolism of glyphosate. Initial studies used spray application of 14C-glyphosate to simulate field application. When S and R biotypes were compared in the absence of toxicity at a sublethal dose, we observed comparable retention and absorption but reduced root translocation in the R biotypes. S and R biotypes from Delaware were further examined at field use rates and results confirmed similar retention and absorption but reduced root translocation in the R biotypes. Application of 14C-glyphosate to a single leaf demonstrated reduced export out of the treated leaf and lower glyphosate import into other leaves, the roots, and the crown in R relative to S biotypes. Examination of the treated leaf by autoradiography showed that glyphosate loading into the apoplast and phloem was delayed and reduced in the R biotype. Our results consistently showed a strong correlation between impaired glyphosate translocation and resistance. Tissues from both S and R biotypes showed elevated levels of shikimate suggesting that 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) remained sensitive to glyphosate. Analysis of tissue shikimate levels demonstrated reduced efficiency in EPSPS inhibition in the R biotypes. Our results suggest that resistance is likely due to altered cellular distribution that impaired phloem loading and plastidic import of glyphosate resulting in reduced overall translocation as well as inhibition of EPSPS.


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Corresponding author. Monsanto Co., 700 Chesterfield Village Parkway West, Chesterfield, MO 63017-1732;


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Baerson, S. R., Rodriguez, D. J., Tran, M., Feng, Y. M., Biest, N. A., and Dill, G. M. 2002. Glyphosate-resistant goosegrass. Identification of a mutation in the target enzyme 5-enolpyruvylshikimate-3-phophsate synthase. Plant Physiol 129:12651275.
Bourque, J. E., Chen, Y. C. S., Heck, G. R., Hubmeier, C. S., Reynolds, T. A., Tran, M., and Sammons, R. D. 2002. Investigations into glyphosate-resistant horseweed (Conyza Canadensis): resistance mechanism studies. Abstr. Weed Sci. Soc. Am 42:65.
Denis, M. H. and Delrot, S. 1993. Carrier-mediated uptake of glyphosate in broad bean (Vicia faba) via a phosphate transporter. Physiol. Plant 87:569575.
Duncan Yerkes, C. N. and Weller, S. C. 1996. Diluent volume influences susceptibility of field bindweed (Convolvulus arvensis) biotypes to glyphosate. Weed Technol 10:565569.
Etheridge, R. E., Womac, A. R., and Mueller, T. C. 1999. Characterization of the spray droplet spectra and patterns of four venturi-type drift reduction nozzles. Weed Technol 13:765770.
Feng, P. C. C., Chiu, T., and Sammons, R. D. 2003a. Glyphosate efficacy is contributed by its tissue concentration and sensitivity in velvetleaf (Abutilon theophrasti). Pestic. Biochem. Physiol 77:8391.
Feng, P. C. C., Chiu, T., Sammons, R. D., and Ryerse, J. S. 2003b. Droplet size affects glyphosate retention, absorption, and translocation in corn. Weed Sci 51:443448.
Feng, P. C. C., Pratley, J. E., and Bohn, J. A. 1999. Resistance to glyphosate in Lolium rigidum. II. Uptake, translocation and metabolism. Weed Sci 47:412415.
Feng, P. C. C., Sandbrink, J. J., and Cowell, J. E. 2000a. Retention, uptake and translocation of 14C-glyphosate from track-spray applications to weeds and correlation to rainfastness. Abstr. Weed Sci. Soc. Am 40:17.
Feng, P. C. C., Sandbrink, J. J., and Sammons, R. D. 2000b. Retention, uptake, and translocation of 14C-glyphosate from track-spray applications and correlation to rainfastness in velvetleaf (Abutilon theophrasti). Weed Technol 14:127132.
Geiger, D. R. and Bestman, H. D. 1990. Self-limitation of herbicide mobility by phytotoxic action. Weed Sci 38:324329.
Geiger, D. R., Shieh, W. J., and Fuchs, M. A. 1999. Causes of self-limited translocation of glyphosate in Beta vulgaris plants. Pestic. Biochem. Physiol 64:124133.
Gressel, J. 2002. Molecular biochemistry of resistance that have evolved in the field. Pages 122218 in Molecular Biology of Weed Control. London: Taylor and Francis.
Hetherington, P. R., Marshall, G., Kirkwood, R. C., and Warner, J. M. 1998. Absorption and efflux of glyphosate by cell suspensions. J. Exp. Botany 49:527533.
Hetherington, P. R., Reynolds, T. L., Marshall, G., and Kirkwood, R. C. 1999. The absorption, translocation and distribution of the herbicide glyphosate in maize expressing the CP-4 transgene. J. Exp. Botany 50:15671576.
Harbour, J. D., Messersmith, C. G., and Ramsdale, B. K. 2003. Surfactants affect herbicides on kochia (Kochia scoparia) and Russian thistle (Salsola iberica). Weed Sci 51:430434.
Jordan, T. N. 1981. Effects of diluents volumes and surfactants on the phytotoxicity of glyphosate to bermudagrass. Weed Sci 29:7983.
Lee, L. J. and Ngim, J. 2000. A first report of glyphosate-resistant goosegrass [Elusine indica (L.) Gaertn] in Malaysia. Pest Manag. Sci 56:336339.
Liu, S. H., Campbell, R. A., Studens, J. A., and Wagner, R. G. 1996. Absorption and translocation of glyphosate in Aspen (Populus tremuloides Michx.) as influenced by droplet size, droplet number, and herbicide concentration. Weed Sci 44:482488.
Lorraine-Colwill, D. F., Powles, S. B., Hawkes, T. R., Hollinshead, P. H., Warner, S. A. J., and Preston, C. 2003. Investigations into the mechanism of glyphosate resistance in Lolium rigidum . Pestic. Biochem. Physiol 74:6272.
Lorraine-Colwill, D. F., Powels, S. B., Howkes, T. R., and Preston, C. 2001. Inheritance of evolved glyphosate resistance in Lolium rigidum . Theor. Appl. Genet 102:545550.
Lydon, J. and Duke, S. O. 1988. Glyphosate induction of elevated levels of hydroxybenzoic acids in higher plants. J. Agric. Food Chem 36:813818.
Morin, F., Vera, V., Nurit, F., Tissut, M., and Marigo, G. 1997. Glyphosate uptake in Catharanthus roseus cells: role of a phosphate transporter. Pestic. Biochem. Physiol 58:1322.
Mueller, T. C., Massey, J. H., Hayes, R. M., Main, C. L., and Stewart, C. N. Jr. 2003. Shikimate accumulates in both glyphosate-sensitive and glyphosate-resistant horseweed (Conyza Canadensis L. Cronq). J. Agric. Food Chem 51:680684.
Ng, C. H., Wickneswari, R., Salmijah, S., Teng, Y. T., and Ismail, B. S. 2003. Gene polymorphisms in glyphosate-resistant and -susceptible biotypes of Elusine indica from Malaysia. Weed Res 43:108115.
Perez, A. and Kogan, M. 2003. Glyphosate-resistant Lolium multiflorum in Chilean orchards. Weed Res 43:1219.
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.
Pratley, J., Urwin, N., Stanton, R., Baines, P., Broster, J., Cullis, K., Schafer, D., Bohn, J., and Krueger, R. 1999. Resistance to glyphosate inLolium rigidum. I. Bioevaluation. Weed Sci 47:405411.
Ramsdale, B. R. and Messersmith, C. G. 2001. Drift-reducing nozzle effects on herbicide performance. Weed Technol 15:453460.
Tran, M., Baerson, S., and Brinker, R. et al. 1999. Characterization of glyphosate resistant Eleusine indica biotypes from Malaysia. Pages 527536 in Proceedings 1(B) of the 17th Asian-Pacific Weed Science Society Conference.
VanGessel, M. J. 2001. Glyphosate-resistant horseweed from Delaware. Weed Sci 49:703705.


Investigations into glyphosate-resistant horseweed (Conyza canadensis): retention, uptake, translocation, and metabolism

  • Paul C. C. Feng, Minhtien Tran (a1), Tommy Chiu (a1), R. Douglas Sammons (a1), Gregory R. Heck (a1) and Claire A. CaJacob (a1)...


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