scholarly journals Multiple-Herbicide Resistance in a 2,4-D–Resistant Waterhemp (Amaranthus tuberculatus) Population from Nebraska

Weed Science ◽  
2017 ◽  
Vol 65 (6) ◽  
pp. 743-754 ◽  
Author(s):  
Roberto J. Crespo ◽  
Ana B. Wingeyer ◽  
Greg R. Kruger ◽  
Chance W. Riggins ◽  
Patrick J. Tranel ◽  
...  
Keyword(s):  
D1 Protein ◽  
Acetolactate Synthase ◽  
Mechanisms Of Action ◽  
Target Site ◽  
Site Mutation ◽  
Auxin Receptor ◽  
Application Rates ◽  
Chlorimuron Ethyl ◽  
Als Inhibitors ◽  
Susceptible Populations

A 2,4-D-resistant tall waterhemp population (FS) from Nebraska was evaluated for resistance to other TIR1 auxin receptor herbicides and to herbicides having alternative mechanisms of action using greenhouse bioassays and genetic markers. Atrazine, imazethapyr, lactofen, mesotrione, glufosinate, and glyphosate were applied in a single-dose bioassay, and tissue was collected from marked plants for genetic analysis. The FS population was not injured by atrazine or by imazethapyr. Approximately 50% of the plants survived lactofen and were actively growing 28 d after treatment. The population was susceptible to mesotrione, glufosinate, and glyphosate. Ametryn, chlorimuron-ethyl, 2,4-D, aminocyclopyraclor, aminopyralid, and picloram were applied in dose–response studies. The FS population was sensitive to ametryn, and the Ser-264-Gly substitution in the D1 protein was not detected, suggesting the lack of response to atrazine is not due to a target-site mutation. The FS population exhibited less than 50% injury to chlorimuron-ethyl at application rates 20 times the labeled use rate. The Ser-653-Asn acetolactate synthase (ALS) substitution, which confers resistance to imidazolinone herbicides, was present in the FS population. However, this does not explain the lack of response to the sulfonylurea herbicide, chlorimuron-ethyl. Sequencing of a portion of thePPX2Lgene did not show the ΔG210 mutation that confers resistance to protoporphyrinogen oxidase–inhibiting herbicides, suggesting that other factors were responsible for waterhemp survival after lactofen application. The FS population was confirmed to be at least 30-fold resistant to 2,4-D relative to the susceptible populations. In addition, it was at least 3-fold less sensitive to aminopyralid and picloram, two other TIR1 auxin receptor herbicides, than the 2,4-D-susceptible populations were. These data indicated that the FS population contains both target and non–target site mechanisms conferring resistance to herbicides spanning at least three mechanisms of action: TIR1 auxin receptors, ALS inhibitors, and photosystem II inhibitors.

Investigating the resistance levels and mechanisms to penoxsulam and cyhalofop-butyl in barnyardgrass (Echinochloa crus-galli) from Ningxia province, China

Weed Science ◽  
2021 ◽  
pp. 1-25
Author(s):  
Qian Yang ◽  
Xia Yang ◽  
Zichang Zhang ◽  
Jieping Wang ◽  
Weiguo Fu ◽  
...  
Keyword(s):  
Herbicide Resistance ◽  
Molecular Mechanisms ◽  
Acetolactate Synthase ◽  
Rice Fields ◽  
Target Site ◽  
Herbicide Resistant ◽  
Susceptible Populations ◽  
High Level ◽  
Als Inhibitor ◽  
Encoding Genes

Abstract Barnyardgrass (Echinochloa crus-galli) is a noxious grass weed which infests rice fields and causes huge crop yield losses. In this study, we collected twelve E. crus-galli populations from rice fields of Ningxia province in China and investigated the resistance levels to acetolactate synthase (ALS) inhibitor penoxsulam and acetyl-CoA carboxylase (ACCase) inhibitor cyhalofop-butyl. The results showed that eight populations exhibited resistance to penoxsulam and four populations evolved resistance to cyhalofop-butyl. Moreover, all of the four cyhalofop-butyl-resistant populations (NX3, NX4, NX6 and NX7) displayed multiple-herbicide-resistance (MHR) to both penoxsulam and cyhalofop-butyl. The alternative herbicides bispyribac-sodium, metamifop and fenoxaprop-P-ethyl cannot effectively control the MHR plants. To characterize the molecular mechanisms of resistance, we amplified and sequenced the target-site encoding genes in resistant and susceptible populations. Partial sequences of three ALS genes and six ACCase genes were examined. A Trp-574-Leu mutation was detected in EcALS1 and EcALS3 in two high-level (65.84- and 59.30-fold) penoxsulam-resistant populations NX2 and NX10, respectively. In addition, one copy (EcACC4) of ACCase genes encodes a truncated aberrant protein due to a frameshift mutation in E. crus-galli populations. None of amino acid substitutions that are known to confer herbicide resistance were detected in ALS and ACCase genes of MHR populations. Our study reveals the widespread of multiple-herbicide resistant E. crus-galli populations at Ningxia province of China that exhibit resistance to several ALS and ACCase inhibitors. Non-target-site based mechanisms are likely to be involved in E. crus-galli resistance to the herbicides, at least in four MHR populations.

Controlling Herbicide-Resistant Annual Bluegrass (Poa annua) Phenotypes with Methiozolin

2017 ◽  
Vol 31 (3) ◽  
pp. 470-476 ◽  
Author(s):  
James T. Brosnan ◽  
Jose J. Vargas ◽  
Gregory K. Breeden ◽  
Sarah L. Boggess ◽  
Margaret A. Staton ◽  
...  
Keyword(s):  
Acetolactate Synthase ◽  
Target Site ◽  
Multiple Resistance ◽  
Herbicide Resistant ◽  
Annual Bluegrass ◽  
Microtubule Inhibitors ◽  
Effective Option ◽  
Target Site Resistance ◽  
Susceptible Control ◽  
Als Inhibitors

Methiozolin is an isoxazoline herbicide being investigated for selective POST annual bluegrass control in managed turfgrass. Research was conducted to evaluate methiozolin efficacy for controlling two annual bluegrass phenotypes with target-site resistance to photosystem II (PSII) or enolpyruvylshikimate-3-phosphate synthase (EPSPS)-inhibiting herbicides (i.e., glyphosate), as well as phenotypes with multiple resistance to microtubule and EPSPS or PSII and acetolactate synthase (ALS)-inhibiting herbicides. All resistant phenotypes were established in glasshouse culture along with a known herbicide-susceptible control and treated with methiozolin at 0, 125, 250, 500, 1000, 2000, 4000, or 8000 g ai ha−1. Methiozolin effectively controlled annual bluegrass with target-site resistance to inhibitors of EPSPS, PSII, as well as multiple resistance to EPSPS and microtubule inhibitors. Methiozolin rates required to reduce aboveground biomass of these resistant phenotypes 50% (GR50 values) were not significantly different from the susceptible control, ranging from 159 to 421 g ha−1. A phenotype with target-site resistance to PSII and ALS inhibitors was less sensitive to methiozolin (GR50=862 g ha−1) than a susceptible phenotype (GR50=423 g ha−1). Our findings indicate that methiozolin is an effective option for controlling select annual bluegrass phenotypes with target-site resistance to several herbicides.

Target site–based penoxsulam resistance in barnyardgrass (Echinochloa crus-galli) from China

Weed Science ◽  
2019 ◽  
Vol 67 (3) ◽  
pp. 281-287 ◽  
Author(s):  
Jiapeng Fang ◽  
Tingting Liu ◽  
Yuhua Zhang ◽  
Jun Li ◽  
Liyao Dong
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Acetolactate Synthase ◽  
Target Site ◽  
Cross Resistance ◽  
Predicted Amino Acid Sequence ◽  
Sequence Analyses ◽  
Als Inhibitors ◽  
Higher Sensitivity

AbstractBarnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] is acknowledged to be the most troublesome weed in rice fields in Anhui and Jiangsu provinces of China. It cannot be effectively controlled using certain acetolactate synthase (ALS)-inhibiting herbicides, including penoxsulam. Echinochloa crus-galli samples with suspected resistance to penoxsulam were collected to identify the target site–based mechanism underlying this resistance. Populations AXXZ-2 and JNRG-2 showed 33- and 7.3-fold resistance to penoxsulam, respectively, compared with the susceptible JLGY-3 population. Cross-resistance to other ALS inhibitors was reported in AXXZ-2 but not in JNRG-2, and occasionally showed higher sensitivity than JLGY-3. In vitro ALS activity assays revealed that penoxsulam concentrations required to inhibit 50% of ALS activity were 11 and 5.2 times greater in AXXZ-2 and JNRG-2, respectively, than in JLGY-3. DNA and predicted amino acid sequence analyses of ALS revealed Ala-205-Val and Ala-122-Gly substitutions in AXXZ-2 and JNRG-2, respectively. Our results indicate that these substitutions in ALS are at least partially responsible for resistance to penoxsulam.

Response of Horseweed Biotypes to Foliar Applications of Cloransulam-methyl and Glyphosate

2005 ◽  
Vol 19 (2) ◽  
pp. 231-236 ◽  
Author(s):  
Geoffrey D. Trainer ◽  
Mark M. Loux ◽  
S. Kent Harrison ◽  
Emilie Regnier
Keyword(s):  
Dose Response ◽  
Response Curve ◽  
Plant Biomass ◽  
Acetolactate Synthase ◽  
Resistance Ratio ◽  
Dose Response Curve ◽  
Fresh Weight ◽  
Chlorimuron Ethyl ◽  
Als Inhibitors ◽  
Dose Response Study

Studies were conducted from 2001 through 2003 to determine the extent of resistance to acetolactate synthase (ALS) inhibitors and glyphosate in Ohio horseweed biotypes. The response of 66 horseweed biotypes to cloransulam-methyl and glyphosate was determined in the greenhouse. Application of 0.07 kg ai cloransulam/ha reduced plant biomass by less than 60% for 38 of the 66 biotypes. Application of 3.4 kg ae glyphosate/ha reduced biomass by at least 80% for the 51 biotypes collected in 2001, but biomass was similar to that of nontreated plants for 11 of the 15 populations collected in 2002. A dose–response study was conducted with selected biotypes, and a nonlinear, logistic dose–response curve was fit to the data to calculate the herbicide dose required to reduce fresh weight 50% (GR50). On the basis of GR50values, the resistance ratio (R/S) for two ALS-resistant biotypes was 34 and 943 for chlorimuron-ethyl and 32 and 168 for cloransulam, respectively. The R/S ratio for two glyphosate-resistant biotypes was 33 and 39. Results of these studies indicate that, in 2002, ALS-resistant horseweed was widespread throughout Ohio, whereas resistance to glyphosate occurred primarily in several counties in southwestern Ohio.

Multiple herbicide resistance in California Italian ryegrass (Lolium perenne ssp. multiflorum): characterization of ALS-inhibiting herbicide resistance

Weed Science ◽  
2019 ◽  
Vol 67 (3) ◽  
pp. 273-280 ◽  
Author(s):  
Parsa Tehranchian ◽  
Vijay K. Nandula ◽  
Maor Matzrafi ◽  
Marie Jasieniuk
Keyword(s):  
Lolium Perenne ◽  
Herbicide Resistance ◽  
Resistance Mechanism ◽  
Acetolactate Synthase ◽  
Target Site ◽  
Italian Ryegrass ◽  
Resistance Level ◽  
Als Inhibitors ◽  
Inhibitor Resistance ◽  
Als Inhibitor

AbstractMultiple resistance to glyphosate, sethoxydim, and paraquat was previously confirmed in two Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot] populations, MR1 and MR2, in northern California. Preliminary greenhouse studies revealed that both populations were also resistant to imazamox and mesosulfuron, both of which are acetolactate synthase (ALS)-inhibiting herbicides. In this study, three subpopulations, MR1-A (from seed of MR1 plants that survived a 16X rate of sethoxydim), MR1-P (from seed of MR1 plants that survived a 2X rate of paraquat), and MR2 (from seed of MR2 plants that survived a 16X rate of sethoxydim), were investigated to determine the resistance level to imazamox and mesosulfuron, evaluate other herbicide options for the control of these multiple resistant L. perenne ssp. multiflorum, and characterize the underlying ALS-inhibitor resistance mechanism(s). Based on LD50 values, the MR1-A, MR1-P, and MR2 subpopulations were 38-, 29-, 8-fold and 36-, 64-, and 3-fold less sensitive to imazamox and mesosulfuron, respectively, relative to the susceptible (Sus) population. Only MR1-P and MR2 plants were cross-resistant to rimsulfuron, whereas both MR1 subpopulations were cross-resistant to imazethapyr. Pinoxaden (ACCase inhibitor [phenylpyrazoline 'DEN']) only controlled MR2 and Sus plants at the labeled field rate. However, all plants were effectively controlled (>99%) with the labeled field rate of glufosinate. Based on I50 values, MR1-A, MR-P, and MR2 plants were 712-, 1,104-, and 3-fold and 10-, 18-, and 5-fold less responsive to mesosulfuron and imazamox, respectively, than the Sus plants. Sequence alignment of the ALS gene of resistant plants revealed a missense single-nucleotide polymorphism resulting in a Trp-574-Leu substitution in MR1-A and MR1-P plants, heterozygous in both, but not in the MR2 plants. An additional homozygous substitution, Asp-376-Glu, was identified in the MR1-A plants. Addition of malathion or piperonyl butoxide did not alter the efficacy of mesosulfuron on MR2 plants. In addition, the presence of 2,4-D had no effect on the response of mesosulfuron on the MR2 and Sus. These results suggest an altered target site is the mechanism of resistance to ALS inhibitors in MR1-A and MR1-P plants, whereas a non–target site based resistance apparatus is present in the MR2 plants.

Basis for Herbicide Resistance in Canadian Populations of Wild Oat (Avena fatua)

Weed Science ◽  
2012 ◽  
Vol 60 (1) ◽  
pp. 10-18 ◽  
Author(s):  
Hugh J. Beckie ◽  
Suzanne I. Warwick ◽  
Connie A. Sauder
Keyword(s):  
Herbicide Resistance ◽  
Economic Effects ◽  
Target Site ◽  
Northern Great Plains ◽  
Western Canada ◽  
Wild Oat ◽  
Site Mutation ◽  
P450 Monooxygenase ◽  
Als Inhibitors ◽  
Als Inhibitor

Wild oat is the second-most abundant, but most economically important, weed across the Canadian Prairies of western Canada. Despite the serious economic effects of resistance to acetyl-CoA carboxylase (ACC) or acetolactate synthase (ALS) inhibitors or both in this weed throughout the Northern Great Plains of North America, little research has examined the basis for herbicide resistance. We investigated target-site and nontarget-site mechanisms conferring ACC- and ALS-inhibitor resistance in 16 wild oat populations from across western Canada (four ACC-inhibitor resistant, four ALS-inhibitor resistant, and eight ACC- and ALS-inhibitor resistant). TheACC1mutations were found in 8 of the 12 ACC inhibitor-resistant populations. The Ile1781Leu mutation was detected in three populations, the Trp2027Cys and Asp2078Gly mutations were in two populations each, and the Trp1999Cys, Ile2041Asn, Cys2088Arg, and Gly2096Ser substitutions were in one population each. Three populations had twoACC1mutations. Only 2 of the 12 ALS inhibitor-resistant populations had anALStarget-site mutation—Ser653Thr and Ser653Asn substitutions. This is the first global report ofALStarget-site mutations inAvenaspp. and four previously undocumentedACC1mutations in wild oat. Based on these molecular analyses, seedlings of five ACC + ALS inhibitor-resistant populations (one with anACC1mutation; four with noACCorALSmutations) were treated with malathion, a known cytochrome P450 monooxygenase inhibitor, followed by application of one of four ACC- or ALS-inhibiting herbicides. Malathion treatment often resulted in control or suppression of these populations, suggesting involvement of this enzyme system in contributing to resistance to both ACC and ALS inhibitors.

scholarly journals Diversified Resistance Mechanisms in Multi-Resistant Lolium spp. in Three European Countries

2020 ◽  
Vol 11 ◽  
Author(s):  
Laura Scarabel ◽  
Silvia Panozzo ◽  
Donato Loddo ◽  
Solvejg K. Mathiassen ◽  
Michael Kristensen ◽  
...  
Keyword(s):  
Management Strategies ◽  
Acetolactate Synthase ◽  
Resistance Mechanisms ◽  
Target Site ◽  
European Countries ◽  
Cereal Crops ◽  
Resistance Pattern ◽  
Italian Population ◽  
Als Inhibitors ◽  
Moderate Resistance

Annual ryegrass species (Lolium spp.) infest cereal crops worldwide. Ryegrass populations with multiple resistance to the acetyl coenzyme A carboxylase (ACCase) and acetolactate synthase (ALS) inhibitors are an increasing problem in several European countries. We investigated the resistance pattern and level of resistance in ryegrass populations collected in Denmark, Greece and Italy and studied the diversity of mechanisms endowing resistance, both target-site and metabolism based. All populations showed high resistance indexes (RI) to the ALS inhibitors, iodosufuron-methyl-sodium + mesosulfuron-methyl (RI from 8 to 70), whereas the responses to the two ACCase inhibitors, clodinafop-propargyl and pinoxaden, differed. The Greek and Italian populations were moderately to highly resistant to clodinafop (RI > 8) and showed low to moderate resistance to pinoxaden (RI ranged from 3 to 13) except for one Italian population. In contrast, the Danish Lolium populations showed low to moderate resistance to clodinafop (RI ranged from 2 to 7) and only one population was resistant to pinoxaden. Different mutant ACCase alleles (Leu1781, Cys2027, Asn2041, Val2041, Gly2078, Arg2088, Ala2096) and ALS alleles (Gly122, Ala197, Gln197, Leu197, Ser197, Thr197, Val205, Asn376, Glu376, Leu574) endowing resistance were detected in the Greek and Italian populations. In several plants, no mutated ALS and ACCase alleles were found showing a great heterogeneity within and among the Greek and Italian populations. Conversely, no mutant ACCase alleles were identified in the four Danish populations and only one mutant ALS allele (Leu574) was detected in two Danish populations. The expression level of nitronate monooxygenase (NMO), glutathione S-transferase (GST) and cytochrome P450s (CYP72A1 and CYP72A2) varied broadly among populations and individual plants within the populations. Constitutive up-regulation of GST, CYP72A1 and CYP72A2 was detected in resistant plants respect to susceptible plants in one Danish and one Italian population. It appears that the mechanisms underlying resistance are rather complex and diversified among Lolium spp. populations from the three countries, coevolution of both target-site resistance and metabolic based herbicide resistance appears to be a common feature in Denmark and Italy. This must be considered and carefully evaluated in adopting resistance management strategies to control Lolium spp. in cereal crops.

Acetolactate synthase inhibitor-resistant stinkweed (Thlaspi arvense L.) in Alberta

2007 ◽  
Vol 87 (4) ◽  
pp. 965-972 ◽  
Author(s):  
H. J. Beckie ◽  
L. M. Hall ◽  
F. J. Tardif ◽  
G. Séguin-Swartz
Keyword(s):  
Herbicide Resistance ◽  
Dominant Gene ◽  
Acetolactate Synthase ◽  
Target Site ◽  
Cross Resistance ◽  
Resistance Pattern ◽  
Site Mutation ◽  
Thlaspi Arvense ◽  
Synthase Inhibitor ◽  
Als Inhibitor

Two stinkweed populations from southern and central Alberta were not controlled by acetolactate synthase (ALS)-inhibiting herbicides in 2000. This study reports on their cross-resistance to ALS-inhibiting herbicides, molecular basis of resistance, and inheritance of resistance. Both putative herbicide-resistant biotypes responded similarly to increasing doses of the herbicides. The biotypes were highly resistant to ethametsulfuron and exhibited a low level of resistance to metsulfuron and imazethapyr. However, both biotypes were not resistant to florasulam, a triazolopyrimidine ALS inhibitor, or sulfometuron, a non-selective sulfonylurea ALS inhibitor. The cross-resistance pattern was consistent with the confirmed target-site mutation. Sequence analysis of the ALS gene detected a Pro197Leu mutation in both biotypes. Similar to many other ALS inhibitor-resistant weed biotypes, resistance was conferred by a single dominant gene. This study confirms the first global occurrence of herbicide resistance in this species. Key words: ALS-inhibitor resistance, ALS sequence, herbicide resistance, target-site mutation

scholarly journals Distribution of Herbicide Resistances and Molecular Mechanisms Conferring Resistance in Missouri Waterhemp (Amaranthus rudisSauer) Populations

Weed Science ◽  
2015 ◽  
Vol 63 (1) ◽  
pp. 336-345 ◽  
Author(s):  
John L. Schultz ◽  
Laura A. Chatham ◽  
Chance W. Riggins ◽  
Patrick J. Tranel ◽  
Kevin W. Bradley
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitution ◽  
Molecular Mechanisms ◽  
Dna Analysis ◽  
D1 Protein ◽  
Acetolactate Synthase ◽  
Glyphosate Resistance ◽  
Mechanisms Of Action ◽  
Resistance To Herbicides ◽  
Inhibitor Resistance

A survey of soybean fields containing waterhemp was conducted just prior to harvest in 2012 to determine the scope and extent of herbicide resistance and multiple herbicide resistances among a sample of Missouri waterhemp populations. Resistance was confirmed to glyphosate and to acetolactate synthase (ALS), protoporphyrinogen oxidase (PPO), photosystem II (PSII), and 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors, but not to 2,4-D. Of the 187 populations tested, 186 exhibited resistance to chlorimuron. The proportions of populations with atrazine or glyphosate resistance were similar, with 30 and 29% of the populations surviving the 3× rates. Lactofen resistance was observed in 5% of the populations, whereas mesotrione resistance was only found in 1.6% of the populations. All populations tested were susceptible to 2,4-D at the 3× rate. At least 52% of the waterhemp populations tested exhibited resistance to herbicides from two mechanism of action. Resistance to atrazine plus chlorimuron as well as glyphosate plus chlorimuron was present in 29% of the populations. Three-way resistance, primarily comprised of resistance to atrazine plus chlorimuron plus glyphosate, was present in 11% of the populations. Resistance to herbicides from four mechanisms of action was found in 2% of the populations, and one population exhibited resistance to herbicides from five mechanisms of action. DNA analysis of a subsample of plants revealed that previously documented mechanisms of resistance in waterhemp, including the ΔG210 deletion conferring PPO-inhibitor resistance, the Trp574Leu amino acid substitution conferring ALS-inhibitor resistance, and elevated 5-enolypyruvyl-shikimate-3-phosphate synthase copy number and the Pro106Ser amino acid substitution resulting in glyphosate resistance, explained survival in many, but not all, instances. Atrazine resistance was not explained by the Ser264Gly D1 protein substitution. Overall, results from these experiments indicate that Missouri soybean fields contain waterhemp populations with resistance to glyphosate, ALS-, PPO-, PSII-, and HPPD-inhibiting herbicides, which are some of the most common mechanisms of action currently utilized for the control of this species in corn and soybean production systems. Additionally, these results indicate that slightly more than half of the populations tested exhibit resistance to more than one herbicide mechanisms of action. Managing the current resistance levels in existing populations is of utmost importance. The use of multiple, effective herbicide modes of action, both preemergence and postemergence, and the integration of optimum cultural and mechanical control practices will be vital in the management of Missouri waterhemp populations in the future.

Prevalence and Mechanism of Atrazine Resistance in Waterhemp (Amaranthus tuberculatus) from Nebraska

Weed Science ◽  
2018 ◽  
Vol 66 (5) ◽  
pp. 595-602 ◽  
Author(s):  
Amaranatha Reddy Vennapusa ◽  
Felipe Faleco ◽  
Bruno Vieira ◽  
Spencer Samuelson ◽  
Greg R. Kruger ◽  
...  
Keyword(s):  
Integrated Management ◽  
Management Strategies ◽  
Point Mutations ◽  
D1 Protein ◽  
Target Site ◽  
Site Mutation ◽  
Protoporphyrinogen Oxidase ◽  
Atrazine Resistance ◽  
Gene Coding ◽  
Amaranthus Tuberculatus

AbstractResistance to atrazine (a photosystem II [PSII] inhibitor) is prevalent in waterhemp [Amaranthus tuberculatus(Moq.) J. D. Sauer] across the U.S. Midwest. Previous research suggests that target-site mutation or rapid metabolism of atrazine mediated by glutathioneS-transferase (GST) conjugation confers resistance inA. tuberculatusfrom Illinois. The distribution and mechanism of resistance to atrazine inA. tuberculatuspopulations from Nebraska (NE) are unknown. In this research we (1) evaluated the response and frequency of resistance in NEA. tuberculatusto soil-applied PSII (metribuzin and atrazine) and protoporphyrinogen oxidase (sulfentrazone) inhibitors, as well as POST-applied atrazine; and (2) determined the mechanism of atrazine resistance in NEA. tuberculatus. The chloroplasticpsbAgene, coding for a D1 protein (the target site of atrazine) was sequenced in 85 plants representing 27 populations ofA. tuberculatus. Furthermore, 24 plants selected randomly from four atrazine-resistant (AR) populations were used to determine the metabolism of atrazine via GST conjugation. Results from the soil-applied herbicide evaluation suggest that metribuzin (0.56 kg ai ha−1) and sulfentrazone (0.28 kg ai ha−1) were effective onA. tuberculatusmanagement. PRE and POST screenings against atrazine in the greenhouse indicate that atrazine (1.345 kg ai ha−1) was not effective on 39% and 73% of theA. tuberculatuspopulations evaluated (total of 109 and 85 populations, respectively), suggesting the prevalence of atrazine resistance inA. tuberculatusin NE. Sequence analysis of thepsbAgene found no known point mutations conferring atrazine resistance. However, the AR plants conjugated atrazine via GST activity faster than the known atrazine-susceptibleA. tuberculatus. Overall, the outcome of this study demonstrates the predominance of metabolism-based resistance to atrazine inA. tuberculatusfrom NE, which may predispose this species to evolve resistance to other herbicides. The use of integrated management strategies forA. tuberculatusis crucial for the control of this troublesome species.

Sign in / Sign up

Export Citation Format

Share Document