A Trp574Leu Target-Site Mutation Confers Imazamox Resistance in Multiple Herbicide-Resistant Wild Poinsettia Populations from Brazil

Wild poinsettia (Euphorbia heterophylla L.) is an important weed species in southern Brazil, especially due to the evolution of multiple herbicide resistance (e.g., acetolactate synthase (ALS)- inhibitors, protoporphyrinogen oxidase inhibitors, and glyphosate). The mechanism of resistance to imazamox was investigated in two wild poinsettia populations (R1 and R2) from southern Brazil and compared to a known susceptible (S) population. Imazamox dose-response experiments revealed high levels of resistance: 45-fold and 224.5-fold based on dry biomass reduction, for R1 and R2, respectively. Extremely high concentrations of imazamox (20,000 µM) were not sufficient to provide 50% inhibition of ALS enzyme activity (I50) for R1 or R2. Hence, resistance levels were estimated to be greater than 123-fold for both populations based on in vitro ALS assays. The ALS gene from all R1 and R2 plants had a Trp574Leu mutation. A genotyping assay was developed to discriminate resistant and susceptible alleles based on the Trp574Leu mutation.

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Target site as the main mechanism of resistance to imazamox in a Euphorbia heterophylla biotype

Scientific Reports ◽

10.1038/s41598-019-51682-z ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 9

Author(s):

Antonia M. Rojano-Delgado ◽

João M. Portugal ◽

Candelario Palma-Bautista ◽

Ricardo Alcántara-de la Cruz ◽

Joel Torra ◽

...

Keyword(s):

Enzyme Activity ◽

Root Exudation ◽

Acetolactate Synthase ◽

Target Site ◽

Southern Brazil ◽

Fresh Weight ◽

Weed Species ◽

Site Mutation ◽

Principal Mechanism ◽

Continuous Use

Abstract Euphorbia heterophylla is a weed species that invades extensive crop areas in subtropical regions of Brazil. This species was previously controlled by imazamox, but the continuous use of this herbicide has selected for resistant biotypes. Two biotypes of E. heterophylla from southern Brazil, one resistant (R) and one susceptible (S) to imazamox, were compared. The resistance of the R biotype was confirmed by dose-response assays since it required 1250.2 g ai ha−1 to reduce the fresh weight by 50% versus 7.4 g ai ha−1 for the S biotype. The acetolactate synthase (ALS) enzyme activity was studied using ALS-inhibiting herbicides from five different chemical families. The R biotype required the highest concentrations to reduce this enzyme activity by 50%. A Ser653Asn mutation was found in the ALS gene of the R biotype. The experiments carried out showed that imazamox absorption and metabolism were not involved in resistance. However, greater 14C-imazamox root exudation was found in the R biotype (~70% of the total absorbed imazamox). Target site mutation in the ALS gene is the principal mechanism that explains the imazamox resistance of the R biotype, but root exudation seems to also contribute to the resistance of this biotype.

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Molecular Basis of Resistance to ALS-Inhibitor Herbicides in Greater Beggarticks

Weed Science ◽

10.1614/ws-09-056.1 ◽

2009 ◽

Vol 57 (5) ◽

pp. 474-481 ◽

Cited By ~ 30

Author(s):

Fabiane P. Lamego ◽

Dirk Charlson ◽

Carla A. Delatorre ◽

Nilda R. Burgos ◽

Ribas A. Vidal

Keyword(s):

Amino Acid ◽

Molecular Basis ◽

Single Point ◽

Acetolactate Synthase ◽

Amino Acid Sequences ◽

Single Point Mutation ◽

Weed Species ◽

Herbicide Resistant ◽

Als Inhibitors ◽

Als Inhibitor

Soybean is a major crop cultivated in Brazil, and acetolactate synthase (ALS)-inhibiting herbicides are widely used to control weeds in this crop. The continuous use of these ALS-inhibiting herbicides has led to the evolution of herbicide-resistant weeds worldwide. Greater beggarticks is a polyploid species and one of the most troublesome weeds in soybean production since the discovery of ALS-resistant biotypes in 1996. To confirm and characterize the resistance of greater beggarticks to ALS inhibitors, whole-plant bioassays and enzyme experiments were conducted. To investigate the molecular basis of resistance in greater beggarticks theALSgene was sequenced and compared between susceptible and resistant biotypes. Our results confirmed that greater beggarticks is resistant to ALS inhibitors and also indicated it possesses at least three isoforms of theALSgene. Analysis of the nucleotide and deduced amino acid sequences among the isoforms and between the biotypes indicated that a single point mutation, G–T, in oneALSisoform from the resistant biotype resulted in an amino acid substitution, Trp574Leu. Two additional substitutions were observed, Phe116Leu and Phe149Ser, in a second isoform of the resistant biotype, which were not yet reported in any other herbicide-resistantALSgene; thus, their role in conferring herbicide resistance is not yet ascertained. This is the first report ofALSmutations in an important, herbicide-resistant weed species from Brazil.

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

Weed Technology ◽

10.1017/wet.2017.13 ◽

2017 ◽

Vol 31 (3) ◽

pp. 470-476 ◽

Cited By ~ 3

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.

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Evaluation of Florpyrauxifen-benzyl on Herbicide-Resistant and Herbicide-Susceptible Barnyardgrass Accessions

Weed Technology ◽

10.1017/wet.2017.100 ◽

2017 ◽

Vol 32 (2) ◽

pp. 126-134 ◽

Cited By ~ 3

Author(s):

M. Ryan Miller ◽

Jason K. Norsworthy ◽

Robert C. Scott

Keyword(s):

Plant Height ◽

Mechanism Of Action ◽

Control Plant ◽

Resistance Management ◽

Acetolactate Synthase ◽

Management Tool ◽

Alternative Mechanism ◽

Alternative Mode ◽

Herbicide Resistant ◽

Biomass Reduction

AbstractFlorpyrauxifen-benzyl is a new herbicide under development in rice that will provide an alternative mode of action to control barnyardgrass. Multiple greenhouse experiments evaluated florpyrauxifen-benzyl efficacy on barnyardgrass accessions collected in rice fields across Arkansas, and to evaluate its efficacy on herbicide-resistant biotypes. In one experiment, florpyrauxifen-benzyl was applied at the labeled rate of 30 g ai ha−1to 152 barnyardgrass accessions collected from 21 Arkansas counties. Florpyrauxifen-benzyl at 30 g ai ha−1effectively controlled barnyardgrass and subsequently reduced plant height and aboveground biomass. In a dose-response experiment, susceptible-, acetolactate synthase (ALS)-, propanil-, and quinclorac-resistant barnyardgrass biotypes were subjected to nine rates of florpyrauxifen-benzyl ranging from 0 to 120 g ai ha−1. The effective dose required to provide 90% control, plant height reduction, and biomass reduction of the susceptible and resistant biotypes fell below the anticipated labeled rate of 30 g ai ha−1. Based on these results, quinclorac-resistant barnyardgrass as well as other resistant biotypes can be controlled with florpyrauxifen-benzyl at 30 g ai ha−1. Overall, results from these studies indicate that florpyrauxifen-benzyl can be an effective tool for controlling susceptible and currently existing herbicide-resistant barnyardgrass biotypes in rice. Additionally, the unique auxin chemistry of florpyrauxifen-benzyl will introduce an alternative mechanism of action in rice weed control thus acting as an herbicide-resistance management tool.

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In vitro and whole-plant magnitude and cross-resistance characterization of two imidazolinone-resistant sugarbeet (Beta vulgaris) somatic cell selections

Weed Science ◽

10.1017/s0043174500090123 ◽

1998 ◽

Vol 46 (1) ◽

pp. 24-29 ◽

Cited By ~ 8

Author(s):

Terry R. Wright ◽

Donald Penner

Keyword(s):

Somatic Cell ◽

Shoot Culture ◽

Acetolactate Synthase ◽

Cross Resistance ◽

Shoot Cultures ◽

Als Inhibitors ◽

Whole Plants ◽

Inhibitor Resistance ◽

Als Inhibitor

Acetolactate synthase (ALS)-inhibiting herbicide carryover in soil can severely affect sugarbeets grown in the year(s) following application. Two newly developed imidazolinone-resistant (IMI-R) sugarbeet somatic cell selections (Sir-13 and 93R30B) were examined for magnitude of resistance and extent of cross-resistance to other classes of ALS inhibitors and compared to a previously developed sulfonylurea-resistant (SU-R) selection, Sur. In vitro shoot culture tests indicated Sir-13 resistance was specific to imidazolinone (IMI) herbicides at approximately a 100-fold resistance compared to the sensitive control sugarbeet. Sur was 10,000-fold resistant to the sulfonylurea (SU) herbicide, chlorsulfuron, and 40-fold resistant to the triazolopyrimidine sulfonanilide (TP) herbicide, flumetsulam, but not cross-resistant to the IMI herbicides. 93R30B was selected for IMI-R from a plant homozygous for the SU-R allele,Sur, and displayed similar in vitro SU-R and TP-R as Sur, but also displayed a very high resistance to various IMI herbicides (400- to 3,600-fold). Compared to the sensitive control, Sir-13 was 300- and > 250-fold more resistant to imazethapyr and imazamox residues in soil, respectively. Response by whole plants to postemergence herbicide applications was similar to that observed in shoot cultures. Sir-13 exhibited > 100-fold resistance to imazethapyr as well as imazamox, and 93R30B showed > 250-fold resistance to both herbicides. 93R30B showed great enough resistance to imazamox to merit consideration of imazamox for use as a herbicide in these sugarbeets. Sir-13 showed a two- to threefold higher level of resistance in the homozygous vs. heterozygous state, indicating that like most ALS-inhibitor resistance traits, it was semidominantly inherited.

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Herbicide resistance in China: a quantitative review

Weed Science ◽

10.1017/wsc.2019.46 ◽

2019 ◽

Vol 67 (6) ◽

pp. 605-612 ◽

Cited By ~ 2

Author(s):

Xiangying Liu ◽

Shihai Xiang ◽

Tao Zong ◽

Guolan Ma ◽

Lamei Wu ◽

...

Keyword(s):

Herbicide Resistance ◽

Crop Production ◽

Rapid Evolution ◽

Acetolactate Synthase ◽

Cross Resistance ◽

Weed Species ◽

Herbicide Resistant ◽

Auxin Herbicides ◽

Economic Boom ◽

Meta Analyses

AbstractThe widespread, rapid evolution of herbicide-resistant weeds is a serious and escalating agronomic problem worldwide. During China’s economic boom, the country became one of the most important herbicide producers and consumers in the world, and herbicide resistance has dramatically increased in the past decade and has become a serious threat to agriculture. Here, following an evidence-based PRISMA (preferred reporting items for systematic reviews and meta-analyses) approach, we carried out a systematic review to quantitatively assess herbicide resistance in China. Multiple weed species, including 26, 18, 11, 9, 5, 5, 4, and 3 species in rice (Oryza sativa L.), wheat (Triticum aestivum L.), soybean [Glycine max (L.) Merr.], corn (Zea mays L.), canola (Brassica napus L.), cotton (Gossypium hirsutum L.)., orchards, and peanut (Arachis hypogaea L.) fields, respectively, have developed herbicide resistance. Acetolactate synthase inhibitors, acetyl-CoA carboxylase inhibitors, and synthetic auxin herbicides are the most resistance-prone herbicides and are the most frequently used mechanisms of action, followed by 5-enolpyruvylshikimate-3-phosphate synthase inhibitors and protoporphyrinogen oxidase inhibitors. The lack of alternative herbicides to manage weeds that exhibit cross-resistance or multiple resistance (or both) is an emerging issue and poses one of the greatest threats challenging the crop production and food safety both in China and globally.

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Translation of In Vitro Activity to In Vivo Activity: Lessons from the Triazolopyrimidine Sulfonanilides

Weed Science ◽

10.1017/s0043174500094649 ◽

1996 ◽

Vol 44 (3) ◽

pp. 757-762 ◽

Cited By ~ 1

Author(s):

B. Clifford Gerwick ◽

Csaba T. Cseke ◽

Gerry Deboer ◽

William A. Kleschick ◽

Paul R. Schmitzer

Keyword(s):

Acetolactate Synthase ◽

Metabolic Stability ◽

Plant Structure ◽

Weed Species ◽

Whole Plant ◽

Stability Data ◽

Activity Models ◽

Two Parameter

Eight triazolopyrimidine sulfonanilides were tested for metabolic stability in a number of crop and weed species. These data, along with in vitro determinations of activity (I50) against acetolactate synthase, successfully described the in vivo activity of these compounds in a two-parameter model. Whole plant activity increased with increasing compound stability and decreasing I50 (r2 =.78, N = 36). The difficulty in obtaining metabolic stability data during a structure optimization program prompted a study with substituent parameters in models of in vivo activity. Models describing whole plant activity in jimsonweed were developed using a series of 5-methyl triazolopyrimidine sulfonanilides that differed only in ortho and meta substituents on the aniline ring. The I50 term and clogP were most important to jimsonweed activity. Hence, in vitro activity (I50) may be a useful component of whole plant structure activity models to aid in identification of barriers to in vivo performance.

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

Weed Science ◽

10.1017/wsc.2019.5 ◽

2019 ◽

Vol 67 (3) ◽

pp. 281-287 ◽

Cited By ~ 1

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.

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Resistance to Bensulfuron-Methyl in Water Plantain (Alisma plantago-aquatica) Populations from Chilean Paddy Fields

Weed Technology ◽

10.1614/wt-08-078.1 ◽

2008 ◽

Vol 22 (4) ◽

pp. 602-608 ◽

Cited By ~ 2

Author(s):

Rodrigo Figueroa ◽

Marlene Gebauer ◽

Albert Fischer ◽

Marcelo Kogan

Keyword(s):

Weed Management ◽

Wide Spectrum ◽

Acetolactate Synthase ◽

Rice Fields ◽

Integrated Weed Management ◽

Cross Resistance ◽

Content Type ◽

Als Inhibitors

Bensulfuron-methyl (BSM) has been one of the most widely used herbicides in Chilean rice fields because it controls a wide spectrum of weeds and does not require field drainage for application. However, failures of BSM to control water plantain in rice fields have been noted since 2002. We assessed BSM effects on suspected resistant (CU1 and CU2) and susceptible (AN1) water plantain accessions collected in Chilean rice fields during 2004 and 2005. BSM rates resulting in 50% growth reduction (GR50) of CU2 and CU1 plants were 12- and 33-fold higher than for AN1 plants, respectively. Acetolactate synthase (ALS) activity assays in vitro suggested resistance in CU1 and CU2 was due to an ALS enzyme with reduced BSM sensitivity compared to the AN1 biotype. Resistance indices (RI), or ratios of the resistant to susceptibleI50values (BSM rate to inhibit ALS-enzyme activity by 50%), were 266 (CU2/AN1) and > 38,462 (CU1/AN1). This agreed with in vivo ALS activity assays whereRIwere 224 (CU2/AN1) and > 8,533 (CU1/AN1). Resistance levels detected in whole-plant or in vivo ALS activity assays were orders of magnitude lower than those detected in in vitro ALS activity studies suggesting nontarget site mechanisms may have mitigated BSM toxicity. However, a consistent ranking of BSM sensitivity levels (AN1 > CU2 > CU1) throughout all three types of assays suggests resistance is primarily endowed by low target site sensitivity. We conclude that susceptible and resistant water plantain biotypes coexist in Chilean paddies, and the use of integrated weed management involving herbicides with a different mode of action would be imperative to prevent further evolution of resistance to BSM and possibly cross-resistance to other ALS inhibitors. In vitro ALS-enzyme assays provided the best discrimination of resistance levels between biotypes.

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Multiple Pro197ALS Substitutions Endow Resistance to ALS Inhibitors within and among Mayweed Chamomile Populations

Weed Science ◽

10.1614/ws-d-10-00146.1 ◽

2011 ◽

Vol 59 (3) ◽

pp. 431-437 ◽

Cited By ~ 18

Author(s):

Suphannika Intanon ◽

Alejandro Perez-Jones ◽

Andrew G. Hulting ◽

Carol A. Mallory-Smith

Keyword(s):

Pacific Northwest ◽

Genotypic Variation ◽

Point Mutations ◽

Acetolactate Synthase ◽

Cross Resistance ◽

Collection Site ◽

Whole Plant ◽

The Pacific ◽

Als Inhibitors

Mayweed chamomile seeds were collected from six different fields across the Pacific Northwest. All populations (each collection site was considered a population) were suspected to have some level of acetolactate synthase (ALS) resistance. Greenhouse and laboratory studies were conducted to determine if these populations were resistant to three different classes of ALS inhibitors: sulfonylureas (SU), imidazolinones (IMI), and triazolopyrimidines (TP). A whole-plant dose–response andin vitroALS activity studies confirmed cross-resistance to thifensulfuron + tribenuron/chlorsulfuron (SU), imazethapyr (IMI), and cloransulam (TP); however, resistance varied by herbicide class and population. TwoALSisoforms of theALSgene (ALS1andALS2) were identified in mayweed chamomile; however, only mutations inALS1were responsible for resistance. No mutations were found inALS2. Sequence analysis of the partialALSgene identified four point mutations at position 197 (Pro197to Leu, Gln, Thr, or Ser) in the resistant populations. This study demonstrates genotypic variation associated with cross-resistance to ALS inhibitors within and between populations.

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