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A Statewide Survey of PPO-Inhibitor Resistance and the Prevalent Target-Site Mechanisms in Palmer amaranth (Amaranthus palmeri) Accessions from Arkansas

  • Vijay K. Varanasi (a1), Chad Brabham (a1), Jason K. Norsworthy (a1), Haozhen Nie (a2), Bryan G. Young (a2), Michael Houston (a1), Tom Barber (a3) and Robert C. Scott (a3)...


Palmer amaranth is one of the most problematic weeds in the midsouthern United States, and the evolution of resistance to protoporphyrinogen oxidase (PPO) inhibitors in biotypes already resistant to glyphosate and acetolactate synthase (ALS) inhibitors is a major cause of concern to soybean and cotton growers in these states. A late-season weed-escape survey was conducted in the major row crop–producing counties (29 counties) to determine the severity of PPO-inhibitor resistance in Arkansas. A total of 227 Palmer amaranth accessions were sprayed with fomesafen at 395 g ha−1 to identify putative resistant plants. A TaqMan qPCR assay was used to confirm the presence of the ΔG210 codon deletion or the R128G/M (homologous to R98 mutation in common ragweed) target-site resistance mechanisms in the PPX2 gene. Out of the 227 accessions screened, 44 were completely controlled with fomesafen, and 16 had only one or two severely injured plants (≥98% mortality) when compared with the 1986 susceptible check (100% mortality). The remaining 167 accessions were genotypically screened, and 82 (49%) accessions were found to harbor the ΔG210 deletion in the PPX2 gene. The R128G was observed in 47 (28%) out of the 167 accessions screened. The mutation R128M, on the other hand was rare, found in only three accessions. About 13% of the accessions were segregating for both the ΔG210 and R128G mutations. Sixteen percent of the tested accessions had mortality ratings <90% and did not test positive for the ΔG210 or the R128G/M resistance mechanisms, indicating that a novel target or non–target site resistance mechanism is likely. Overall, PPO inhibitor–resistant Palmer amaranth is widespread in Arkansas, and the ΔG210 resistance mechanism is especially dominant in the northeast corridor, while the R128G mutation is more prevalent in counties near Memphis, TN.


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Associate Editor for this paper: Patrick J. Tranel, University of Illinois.

These authors made equal contributions.



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Bond, JA, Oliver, LR, Stephenson, DO IV (2006) Response of Palmer amaranth (Amaranthus palmeri) accessions to glyphosate, fomesafen, and pyrithiobac. Weed Technol 20:885892
Dayan, FE, Daga, PR, Duke, SO, Lee, RM, Tranel, PJ, Doerksen, RJ (2010) Biochemical and structural consequences of a glycine deletion in the α-8 helix of protoporphyringen oxidase. Biochim Biophys Acta 1804:15481556
Doyle, JJ, Doyle, JL (1987) A rapid DNA isolation procedure for small quantities of fresh leaf tissue. Phytochem Bull 19:1115
Giacomini, DA, Umphres-Lopez, AM, Nie, H, Mueller, TC, Steckel, LE, Young, BG, Tranel, PJ (2017) Two new PPX2 mutations associated with resistance to PPO-inhibitor herbicides in Amaranthus palmeri . Pest Manag Sci 73:15591563
Heap, I (2017) The International Survey of Herbicide Resistant Weeds. Accessed: May 15, 2017
Jacobs, JM, Jacobs, NJ (1993) Porphyrin accumulation and export by isolated barley (Hordeum vulgare) plastids. Plant Physiol 101:11811187
Jasieniuk, M, Brule-Babel, AL, Morrison, IN (1996) The evolution and genetics of herbicide resistance in weeds. Weed Sci 44:176193
Lee, RM, Hager, AG, Tranel, PJ (2008) Prevalence of a novel resistance mechanism to PPO-inhibiting herbicides in waterhemp (Amaranthus tuberculatus). Weed Sci 56:371375
Matringe, MJM, Camadro, PL, Scalla, R (1989) Protoporphyrinogen oxidase as a molecular target for diphenyl ether herbicides. Biochem J 260:231235
Norsworthy, JK (2003) Use of soybean production surveys to determine weed management needs of South Carolina farmers. Weed Technol 17:195201
Owen, MDK, Zelaya, IA (2005) Herbicide-resistant crops and weed resistance to herbicides. Pest Manag Sci 61:301311
Patzoldt, WL, Hager, AG, McCormick, JS, Tranel, PJ (2006) A codon deletion confers resistance to herbicides inhibiting protoporphyrinogen oxidase. Proc Natl Acad Sci USA 103:1232912334
Prostko, EP (2011) Developing a herbicide resistant weed management plan. Page 1538 in Proceedings of the 2011 Beltwide Cotton Conference. Cordova, TN: National Cotton Council of America
R Core Team (2017) R: A Language and Environment for Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing. Accessed June 12, 2017
Riar, DS, Norsworthy, JK, Steckel, LE, Stephenson, DO IV, Eubank, TW, Scott, RC (2013) Assessment of weed management practices and problem weeds in the Midsouth United States—soybean: a consultant’s perspective. Weed Technol 27:612622
Rousonelos, SL, Lee, RM, Moreira, MS, VanGessel, MJ, Tranel, PJ (2012) Characterization of a common ragweed (Ambrosia artemisiifolia) population resistant to ALS- and PPO-inhibiting herbicides. Weed Sci 60:335344
Salas, RA, Burgos, NR, Rangani, G, Singh, S, Refatti, JP, Piveta, L, Tranel, PJ, Mauromoustakos, A, Scott, RC (2017) Frequency of Gly-210 deletion mutation among protoporphyrinogen oxidase inhibitor-resistant Palmer amaranth (Amaranthus palmeri) populations. Weed Sci 65:718731
Salas, RA, Burgos, NR, Tranel, PJ, Singh, S, Glasgow, L, Scott, RC, Nichols, RL (2016) Resistance to PPO-inhibiting herbicide in Palmer amaranth from Arkansas. Pest Manag Sci 72:864869
Schwartz-Lazaro, LM, Norsworthy, JK, Scott, RC, Barber, LT (2017) Resistance of two Arkansas Palmer amaranth populations to multiple herbicide sites of action. Crop Prot 96:158163
Thinglum, KA, Riggins, CW, Davis, AS, Bradley, KW, Al-Khatib, K, Tranel, PJ (2011) Wide distribution of the waterhemp (Amaranthus tuberculatus) ΔG210 PPX2 mutation, which confers resistance to PPO-inhibiting herbicides. Weed Sci 59:2227
Wychen, VL (2016) 2016 Survey of the most common and troublesome weeds in broadleaf crops, fruits & vegetables in he United States and Canada. Weed Science Society of America National Weed Survey Dataset. Accessed June 10, 2017



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