A Palmer amaranth population (seeds collected in the year 2000; Washington Co., MS) suspected to be susceptible to glyphosate was examined as a population and as individual plants and found to exhibit varying tolerance or resistance to glyphosate. Whole plant spraying of glyphosate (0.84 kg ·ha ?1 ) to the population revealed that approximately 40% of this population w ere resistant to glyphosate and an LD 50 of 0.75 kg ·ha ?1 was determined. Spray application of glyphosate indicated that some plants displayed varying degrees of resistance 14 days after treatment. Initial tests using leaf disc bioassays on 10 individual plants selected randomly from the population, allowed characterization of glyphosate resistance using both visual ratings of injury and quantitative measurement via chlorophyll content analysis. After initial bioassays and spray application, five plants with a range of tolerance to glyphosate were selected for cloning so that further studies could be accomplished on these individuals. Q-PCR analysis of these clones showed that resistance was not due to elevated EPSPS gene copy number. Shikimate levels were lower in the resistant and higher in the susceptible clones which correlated with varying degrees of resistance demonstrated in bioassays and spray application of glyphosate of these clones. Results demonstrate that individuals in a population can vary widely with respect to herbicide resistance and suggest that uptake, translocation, sequestration, metabolism or altered target site may contribute to the resistance in some individuals of this population.
I. Heap, “International Survey of Herbicide-Resistant Weeds,” 2013. http://www.weedscience.org/in.asp
Anonymous, “New Report Reveals Dramatic Rise in Pesticide Use on Genetically Engineered (GE) Crops Due to the Spread of Resistant Weeds,” 2009. http://wwwprnewswire.com/news-release
S. Culpepper, T. L. Grey, W. K. Vencill, J. M. Kichler, T. M. Webster, S. M. Brown, A. C. York, J. W. Davis and W. W. Hanna, “Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) Confirmed in Georgia,” Weed Science, Vol. 54, No. 4, 2006, pp. 620-626. http://dx.doi.org/10.1614/WS-06-001R.1
R. C. Scott, L. E. Steckel, K. L. Smith, T. Mueller, L. R. Oliver and J. Norsworthy, “Glyphosate-Resistant Palmer Amaranth inTennessee and Arkansas,” Proceedings of the 60th Southern Weed Science Society, Nashville, 22-24 January 2007, p. 226.
C. York, J. R. Whitaker, A. S. Culpepper and C. L. Main, “Glyphosate-Resistant Palmer Amaranth in the Southeastern United States,” Proceedings of the Southern Weed Science Society, Vol. 60, 2007, p. 225.
T. M. Webster, “Weed Survey-Southern States: Broadleaf Crops Subsection,” Proceedings of the Southern Weed Science Society, Vol. 58, 2005, pp. 291-294.
M. J. Horak and T. M. Loughin, “Growth Analysis of Four Amaranthus Species,” Weed Science, Vol. 48, No. 3, 2000, pp. 347-355. http://dx.doi.org/10.1614/0043-1745(2000)048[0347:GAOFAS]2.0.CO;2
N. Bensch, M. J. Horak and D. Peterson, “Interference of Redroot Pigweed (Amaranthus retroflexus), Palmer Amaranth (A. palmeri), and Common Waterhemp (A. rudis) in Soybean,” Weed Science, Vol. 51, No. 1, 2003, pp. 37-43. http://dx.doi.org/10.1614/0043-1745(2003)051[0037:IORPAR]2.0.CO;2
A. Sellers, R. J. Smeda, W. G. Johnson, A. J. Kendig and M. R. Ellersieck, “Comparative Growth of Six Amaranthus Species in Missouri,” Weed Science, Vol. 51, No. 3, 2003, pp. 329-333. http://dx.doi.org/10.1614/0043-1745(2003)051[0329:CGOSAS]2.0.CO;2
S. Culpepper, A. W. MacRae, A. C. York and J. Kichler, “Managing Glyphosate-Resistant Palmer Amaranth in Conventional and Strip-Till Roundup Ready Cotton,” Proceedings of the Southern Weed Science Society, Vol. 61, 2008, p. 62.
S. Culpepper, A. C. York, J. M. Kichler and A. W. MacRae, “Glyphosate-Resistant Palmer Amaranth Response to Weed Management Programs in Roundup Ready and Liberty Link Cotton,” Proceedings of the Beltwide Cotton Conference, Nashville, 10 January 2008, pp. 1689-1690.
J. R. Whitaker, “Distribution, Biology, and Management of Glyphosate Resistant Palmer Amaranth in North Carolina,” Ph.D. Dissertation, North Carolina State University, Raleigh, 2009. http://repository.lib.ncsu.edu/ir/bitstream/1840.16/3130/1/etd.pdf
H. C. Steinrücken and N. Amrhein, “The Herbicide Glyphosate Is a Potent Inhibitor of 5-Enolpyruvyl-Shikimic Acid-3-Phosphate Synthase,” Biochemical and Biophysical Research Communications, Vol. 94, No. 4, 1980, pp. 1207-1212. http://dx.doi.org/10.1016/0006-291X(80)90547-1
J. E. Franz, M. K. Mao and J. A. Sikorski, “Glyphosate’s Molecular Mode of Action,” In: Glyphosate: A Unique Global Herbicide, American Chemical Society, Washington DC, 1997, pp. 521-615.
K. J. Gruys and J. A. Sikorski, “Inhibitors of Tryptophan, Phenylalanine and Tyrosine Biosynthesis as Herbicides,” In: B. K. Singh, Ed., Plant Amino Acids: Biochemistry and Biotechnology, CRC Press, Boca Raton, 1999, pp. 357-384.
N. Amrhein, B. Deus, P. Gehrke and H. C. Steinrüchen, “The Site of the Inhibition of the Shikimate Pathway by Glyphosate. II. Interference of Glyphosate with Chorismate Formation in Vivo and in Vitro,” Plant Physiology, Vol. 66, No. 5, 1980, pp. 830-834. http://dx.doi.org/10.1104/pp.66.5.830
K. M. Herrmann, “The Shikimate Pathway as an Entry to Aromatic Secondary Metabolism,” Plant Physiology, Vol. 107, No. 1, 1995, pp. 7-12. http://dx.doi.org/10.1104/pp.107.1.7
T. A. Gaines, W. Zhang, D. Wang, B. Bukun, S. T. Chis-holm, D. L. Shaner, S. J. Nissen, W. L. Patzoldt, P. J. Tranel, A. S. Culpepper, T. L. Grey, T. M. Webster, W. K. Vencill, R. D. Sammons, J. Jiang, C. Preston, J. E. Leach and P. Westra, “Gene Amplification Confers Glyphosate Resistance in Amaranthus palmeri,” Proceedings of the National Academy of Sciences, Vol. 107, No. 3, 2010, pp. 1029-1034. http://dx.doi.org/10.1073/pnas.0906649107
Sosnoskie, L. M., T. M. Webster, A. S. Culpepper and J. Kichler, “The Biology and Ecology of Palmer amaranth: Implications for Control,” 2011. http://www.caes.uga.edu/applications/publications/files/pdf/C%201000_1.PDF
D. L. Shaner, R. B. Lindenmeyer and M. H. Ostlie, “What Have the Mechanisms of Resistance to Glyphosate Taught Us?” Pest Management Science, Vol. 68, No. 1, 2011, pp. 3-9.
R. E. Hoagland, R. H. Jordan and N. D. Teaster, “Bioassay and Characterization of Several Palmer Amaranth (Amaranthus palmeri) Biotypes with Varying Tolerances to Glyphosate,” American Journal of Plant Sciences, Vol. 4, No. 5, 2013, pp. 1029-1037. http://dx.doi.org/10.4236/ajps.2013.45127
N. D. Teaster and R. E. Hoagland, “Characterization of Glyphosate Resistance in Cloned Amaranthus palmeri Plants,” Weed Biology and Management, 2013, in Press.
J. D. Barnes, L. Balaguer, E. Manriques, S. Elvira and A. W. Davison, “A Reappraisal of the Use of DMSO for the Extraction and Determination of Chlorophylls a and b in Lichens and Higher Plants,” Environmental and Experimental Botany, Vol. 32, No. 2, 1992, pp. 85-100. http://dx.doi.org/10.1016/0098-8472(92)90034-Y
J. D. Hiscox and G. F. Israelstam. “A Method for the Extraction of Chlorophyll from Leaf Tissue without Maceration,” Canadian Journal of Botany, Vol. 57, No. 12, 1979, pp. 1332-1334. http://dx.doi.org/10.1139/b79-163
T. Evans, J. Song and P. E. Jameson, “Micro-Scale Chlorophyll Analysis and Developmental Expression of a Cytokinin Oxidase/Dehydrogenase Gene during Leaf Development and Senescence,” Plant Growth Regulation, Vol. 66, No. 1, 2012, pp. 95-99. http://dx.doi.org/10.1007/s10725-011-9627-5
D. L. Shaner, T. Nadler-Hassar, W. B. Henry and C. H. Koger, “A Rapid in Vivo Shikimate Accumulation Assay with Excised Leaf Discs,” Weed Science, Vol. 53, No. 6, 2005, pp. 769-774.doi.org/10.1614/WS-05-009R.1
K. J. Livak and T. D. Schmittgen, “Analysis of Relative Gene Expression Data using Real-Time Quantitative PCR and the 2 -ΔΔCT Method,” Methods, Vol. 25, No. 4, 2001, pp. 402-408. http://dx.doi.org/10.1006/meth.2001.1262
F. Trucco, M. R. Jeschke, A. L. Rayburn and P. J. Tranel, “Promiscuity in Weedy Amaranths: High Frequency of Tall Waterhemp (Amaranthus tuberculatus) x Smooth Pigweed (A. hybridus) Hybridization under Field Conditions,” Weed Science, Vol. 53, No. 1, 2005, pp. 46-54. http://dx.doi.org/10.1614/WS-04-103R
J. K. Norsworthy, G. M. Griffith, R. C. Scott, K. L. Smith and L. R. Oliver, “Confirmation and Control of Glyphosate Palmer amaranth (Amaranthus palmeri) in Arkansas,” Weed Technology, Vol. 22, No. 1, 2008, pp. 108-113. http://dx.doi.org/10.1614/WT-07-128.1
P. C. C. Feng, M. Tran, T. Chiu, R. D. Sammons, G. R. Heck and C. A. CaJacob, “Investigations into Glyphosate-Resistant Horseweed (Conyza canadensis): Retention, Uptake, Translocation, and Metabolism,” Weed Science, Vol. 52, No. 4, 2004, 498-505. http://dx.doi.org/10.1614/WS-03-137R
V. K. Nandula, J. D. Ray, D. N. Ribeiro, Z. Pan and K. N. Reddy, “Glyphosate Resistance in Tall Waterhemp (Amaranthus tuberculatus) from Mississippi Is Due to Both Altered Target-Site and Nontarget-Site Mechanisms. Weed Science, Vol. 61, No. 3, 2013, pp. 374-383. http://dx.doi.org/10.1614/WS-D-12-00155.1
A. S. Franssen, D. Z. Skinner, K. Al-Khatib, M. J. Horak and P. A. Kulakow, “Interspecific Hybridization and Gene Flow of ALS Resistance in Amaranthus Species,” Weed Science, Vol. 49, No. 5, 2001, pp. 598-606. http://dx.doi.org/10.1614/0043-1745(2001)049[0598:IHAGFO]2.0.CO;2
D. K. Wetzel, M. J. Horak, D. Z. Skinner and P. A. Kulakow, “Transferal of Herbicide Resistance Traits from Amarathus palmerito Amaranthus rudis,” Weed Science, Vol. 47, No. 5, 1999, pp. 538-543.
S. B. Powles and C. Preston, “Evolved Glyphosate Resistance in Plants: Biochemical and Genetic Basis of Resistance,” Weed Technology,Vol. 20, No. 2, 2006, pp. 282-289. http://dx.doi.org/10.1614/WT-04-142R.1
X. Ge, D. A. d’Avignon, J. J. H. Ackerman and R. D. Sammons, “Rapid Vacuolar Sequestration: the Horseweed Glyphosate Resistance Mechanism,” Pest Management Science, Vol. 66, No. 4, 2010, pp. 345-348.
Q. Yu, A. Cairns and S. Powles, “Glyphosate, Paraquat and ACCase Multiple Herbicide Resistance Evolved in a Lolium rigidumBiotype,” Planta, Vol. 225, No. 2, 2007, pp. 499-513. http://dx.doi.org/10.1007/s00425-006-0364-3
V. K. Nandula, K. N. Reddy, D. H. Poston, A. M. Rimando and S. O. Duke, “Glyphosate Tolerance Mechanism in Italian Ryegrass (Lolium multiflorum) from Mississippi,” Weed Science, Vol. 56, No. 3, 2008, pp. 344-349. http://dx.doi.org/10.1614/WS-07-115.1
A. Perez-Jones, K. W. Park, N. Polge, J. Colquhoun and C. A. Mallory-Smith, “Investigating the Mechanisms of Glyphosate Resistance in Lolium multiflorum,” Planta, Vol. 226, No. 2, 2007, pp. 395-404. http://dx.doi.org/10.1007/s00425-007-0490-6
J. W. Dickson, R. C. Scott, N. R. Burgos, R. A. Salas and K. L. Smith, “Confirmation of Glyphosate-Resistant Italian Ryegrass (Lolium perenne ssp. multiflorum) in Arkansas,” Weed Technology, Vol. 25, No. 4, 2011, pp. 674-679. http://dx.doi.org/10.1614/WT-D-11-00040.1
R. A. Salas, F. E. Dayan, Z. Pan, S. B. Watson, J. W. Dickson, R. C. Scott and N. R. Burgos, “EPSPS Gene Amplification in Glyphosate-Resistant Italian Ryegrass (Lolium perennespp. multiflorum) from Arkansas,” Pest Management Science, Vol. 68, No. 9, 2012, pp. 1223-1230. http://dx.doi.org/10.1002/ps.3342
M. W. M. Burnet, J. T. Christopher, J. A. M. Holtum and S. B. Powles, “Identification of Two Mechanisms of Sulfonylurea Resistance within One Population of Rigid Ryegrass (Lolium rigidum) Using a Selective Germination Medium,” Weed Science, Vol. 42, No. 3, 1994, pp. 468-473. http://wssaabstracts.com/public/4/abstract-85,html
D. A. Giacomini, S. Ward, T. A. Gaines and P. Westra, “Inheritance of EPSPS Gene Amplification in Palmer Amaranth,” Proceedings of the Weed Science Society of America, Vol. 53, No. 85. 2011.
A. Chandi, S. R. Milla-Lewis, D. Giacomini, P. Westra, C. Preston, D. L. Jordan, A. C. York, J. D. Burton and J. R. Whitaker, “Inheritance of Evolved Glyphosate Resistance in a North Carolina Palmer Amaranth (Amaranthus palmeri) Biotype,” International Journal of Agronomy, Vol. 2012, No. 2012, 2012, pp. 1-7. http://dx.doi.org/10.1155/2012/176108
P. C. C. Feng, J. E. Pratley and J. A. Bohn, “Resistance to Glyphosate in Lolium rigidum. II. Uptake, Translocation and Metabolism,” Weed Science, Vol. 47, No. 4, 1999, pp. 412-415.
D. F. Lorraine-Colwill, S. B. Powles, T. R. Hawkes, P. H. Hollinshead, S. A. J. Warner and C. Preston, “Investigations into the Mechanism of Glyphosate Resistance in Lolium rigidum,” Pesticide Biochemistry and Physiology, Vol. 74, No. 2, 2003, pp. 62-72.
M. Tran, S. Baerson, R. Brinker, L. Casagrande, M. Faletti, Y. Feng, M. Nemeth, T. Reynolds, D. Rodriguez, D. Shaffer, D. Stalker, N. Taylor, Y. Teng and G. Dill, “Characterization of Glyphosate Resistant Eleusine indica Biotypes from Malaysia,” Proceedings of the 17th AsianPacific Weed Science Society Conference, Bangkok, 22-27 November 1999, pp. 527-536.