scholarly journals Patterns of resistance to AHAS inhibitors in Limnocharis flava from Malaysia

2017 ◽  
Vol 54 (No. 1) ◽  
pp. 48-59
Author(s):  
Zakaria Norazua ◽  
Ahmad-Hamdani Muhammad Saiful ◽  
Juraimi Abdul Shukor
Keyword(s):  
Dose Response ◽  
Resistance Mechanisms ◽  
Rice Fields ◽  
Cross Resistance ◽  
Multiple Resistance ◽  
Low Level ◽  
Metsulfuron Methyl ◽  
Synthetic Auxin ◽  
Target Site Resistance ◽  
High Level

Limnocharis flava (L.) Buchenau is among the most problematic rice weeds in Malaysia and is also reported to have developed multiple resistance to AHAS inhibitor bensulfuron-methyl and synthetic auxin 2,4-D. In this study, resistance across different AHAS inhibitors was characterised in a L. flava population infesting rice fields in Pulau Pinang, Malaysia. Dose-response experiments were conducted to determine the level of resistance to sulfonylureas, imidazolinone, triazolopyrimidine, and pyrimidinyl-thiobenzoate. Cross-resistance across different AHAS inhibitors was observed in the resistant L. flava population, exhibiting a high level of resistance to bensulfuron-methyl, while exhibiting a moderate level of resistance to metsulfuron-methyl and a low level of resistance to pyrazosulfuron-ethyl and pyribenzoxim. However, all resistant L. flava individuals were still sensitive to imazethapyr, penoxsulam, and bispyribac-sodium. Based on the results, it is likely that resistance to AHAS inhibitors in L. flava is conferred by target-site resistance mechanisms.

Confirmation and characterization of cyhalofop-butyl–resistant Chinese sprangletop (Leptochloa chinensis) populations from China

Weed Science ◽  
2020 ◽  
Vol 68 (3) ◽  
pp. 253-259
Author(s):  
Yajun Peng ◽  
Lang Pan ◽  
Ducai Liu ◽  
Xiaomei Cheng ◽  
Guolan Ma ◽  
...  
Keyword(s):  
Resistance Index ◽  
Resistance Mechanisms ◽  
The Other ◽  
Susceptible Population ◽  
Acetyl Coenzyme A ◽  
Target Site Resistance ◽  
High Level ◽  
Acetyl Coenzyme A Carboxylase ◽  
Grass Weed

AbstractChinese sprangletop [Leptochloa chinensis (L.) Nees] is one grass weed severely affecting rice (Oryza sativa L.) growth in paddies in China. Cyhalofop-butyl is the main herbicide used to control grass weeds in Chinese paddy fields, especially for controlling L. chinensis; however, L. chinensis has evolved resistance to cyhalofop-butyl due to continuous and extensive application. To investigate cyhalofop-butyl resistance levels and mechanisms in L. chinensis in some of the Chinese rice areas, 66 field populations were collected and treated with cyhalofop-butyl. Of these tested populations, 10 showed a high level of resistance to cyhalofop-butyl; the 50% effective dose ranged within 108.4 to 1,443.5 g ai ha−1 with resistance index values of 9.1 to 121.8 when compared with the susceptible population. Acetyl-coenzyme A carboxylase genes (ACCase) of susceptible and all 10 resistant populations were amplified and sequenced. Among them, Ile-1781-Leu, Trp-2027-Cys, Trp-2027-Ser, and Ile-2041-Asn mutations were found in five resistant populations. No known resistance-related mutations were found in the other five resistant populations, indicating that resistance to cyhalofop-butyl in these populations was likely to be endowed by non–target site resistance mechanisms. Notably, the Ile-1781-Leu and Trp-2027-Cys substitutions have previously been reported, but this is the first report of Trp-2027-Ser and Ile-2041-Asn mutations in L. chinensis. Furthermore, three derived cleaved amplified polymorphic sequence methods were developed to rapidly detect these mutations in L. chinensis.

scholarly journals Mutations that increase expression of the EmrAB-TolC efflux pump confer increased resistance to nitroxoline in Escherichia coli

2019 ◽  
Author(s):  
Fabiola Puértolas-Balint ◽  
Omar Warsi ◽  
Marius Linkevicius ◽  
Po-Cheng Tang ◽  
Dan I Andersson
Keyword(s):  
Escherichia Coli ◽  
Target Genes ◽  
Efflux Pump ◽  
Resistance Mechanisms ◽  
Cross Resistance ◽  
Resistance Mutations ◽  
Double Knockout ◽  
Low Level ◽  
Resistant Mutants ◽  
Level Resistance

Abstract Objectives To determine the mechanism of resistance to the antibiotic nitroxoline in Escherichia coli. Methods Spontaneous nitroxoline-resistant mutants were selected at different concentrations of nitroxoline. WGS and strain reconstruction were used to define the genetic basis for the resistance. The mechanistic basis of resistance was determined by quantitative PCR (qPCR) and by overexpression of target genes. Fitness costs of the resistance mutations and cross-resistance to other antibiotics were also determined. Results Mutations in the transcriptional repressor emrR conferred low-level resistance to nitroxoline [nitroxoline MIC (MICNOX) = 16 mg/L] by increasing the expression of the emrA and emrB genes of the EmrAB-TolC efflux pump. These resistant mutants showed no fitness reduction and displayed cross-resistance to nalidixic acid. Second-step mutants with higher-level resistance (MICNOX = 32–64 mg/L) had mutations in the emrR gene, together with either a 50 kb amplification, a mutation in the gene marA, or an IS upstream of the lon gene. The latter mutations resulted in higher-level nitroxoline resistance due to increased expression of the tolC gene, which was confirmed by overexpressing tolC from an inducible plasmid in a low-level resistance mutant. Furthermore, the emrR mutations conferred a small increase in resistance to nitrofurantoin only when combined with an nfsAB double-knockout mutation. However, nitrofurantoin-resistant nfsAB mutants showed no cross-resistance to nitroxoline. Conclusions Mutations in different genes causing increased expression of the EmrAB-TolC pump lead to an increased resistance to nitroxoline. The structurally similar antibiotics nitroxoline and nitrofurantoin appear to have different modes of action and resistance mechanisms.

scholarly journals Point Mutations as Main Resistance Mechanism Together With P450-Based Metabolism Confer Broad Resistance to Different ALS-Inhibiting Herbicides in Glebionis coronaria From Tunisia

2021 ◽  
Vol 12 ◽  
Author(s):  
Zeineb Hada ◽  
Yosra Menchari ◽  
Antonia M. Rojano-Delgado ◽  
Joel Torra ◽  
Julio Menéndez ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Dose Response ◽  
Resistance Mechanism ◽  
Point Mutations ◽  
Acetolactate Synthase ◽  
Target Site ◽  
Cross Resistance ◽  
P450 Monooxygenase ◽  
Target Site Resistance ◽  
Sites Of Action

Resistance to acetolactate synthase (ALS) inhibiting herbicides has recently been reported in Glebionis coronaria from wheat fields in northern Tunisia, where the weed is widespread. However, potential resistance mechanisms conferring resistance in these populations are unknown. The aim of this research was to study target-site resistance (TSR) and non-target-site resistance (NTSR) mechanisms present in two putative resistant (R) populations. Dose–response experiments, ALS enzyme activity assays, ALS gene sequencing, absorption and translocation experiments with radiolabeled herbicides, and metabolism experiments were carried out for this purpose. Whole plant trials confirmed high resistance levels to tribenuron and cross-resistance to florasulam and imazamox. ALS enzyme activity further confirmed cross-resistance to these three herbicides and also to bispyribac, but not to flucarbazone. Sequence analysis revealed the presence of amino acid substitutions in positions 197, 376, and 574 of the target enzyme. Among the NTSR mechanisms investigated, absorption or translocation did not contribute to resistance, while evidences of the presence of enhanced metabolism were provided. A pretreatment with the cytochrome P450 monooxygenase (P450) inhibitor malathion partially synergized with imazamox in post-emergence but not with tribenuron in dose–response experiments. Additionally, an imazamox hydroxyl metabolite was detected in both R populations in metabolism experiments, which disappeared with the pretreatment with malathion. This study confirms the evolution of cross-resistance to ALS inhibiting herbicides in G. coronaria from Tunisia through TSR and NTSR mechanisms. The presence of enhanced metabolism involving P450 is threatening the chemical management of this weed in Tunisian wheat fields, since it might confer cross-resistance to other sites of action.

scholarly journals Prevalence and molecular characterization of methicillin-resistant Staphylococcus aureus with mupirocin, fusidic acid and/or retapamulin resistance

2020 ◽  
Author(s):  
Wenjing Chen ◽  
Chunyan He ◽  
Han Yang ◽  
Wen Shu ◽  
Zelin Cui ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Fusidic Acid ◽  
Resistance Mechanisms ◽  
Antibiotics Resistance ◽  
Genetic Characteristics ◽  
Methicillin Resistant ◽  
Low Level ◽  
High Level ◽  
Level Resistance

Abstract Data on the prevalence of resistance to mupirocin (MUP), fusidic acid (FA) and retapamulin (RET) in methicillin-resistant Staphylococcus aureus (MRSA) from China are still limited. In this study we examined these three antibiotics resistance pheno and geno-typically in 1206 MRSA clinical isolates. Phenotypic MUP, FA and RET resistance was determined by MICs, and genotypically by PCR and DNA sequencing examining genes mupA / B , fusB - D , cfr and vgaA / Av , and mutations in ileS , fusA / E , rplC , and 23S RNA V domain. The genetic characteristics of resistance isolates were conducted by PFGE and MLST. Overall MRSA MUP, FA and RET resistance was low (5.1%, 1.0% and 0.3%, respectively). The mupA was the mechanism of high-level MUP resistance. All low-level MUP resistance isolates possessed an equivocal mutation N213D in IleS, and 2 of them additionally had the reported V588F mutation impacting the Rossman fold. FusA mutations, such as L461K, H457Q, H457Y and V90I, were the primary FA resistance mechanisms among high-level resistance isolates, most of which contained fusC ; however, all low-level resistance strains carried fusB . No resistance mechanisms detected were found among RET resistance isolates. Genetic analysis demonstrated clone spread for MUP resistance isolates. In conclusion, MUP, FA and RET exhibited highly activity against MRSA isolates. Acquired genes and chromosome-borne genes mutations were responsible for MUP and FA resistance, and further investigation is needed to uncover the RET resistance mechanisms. Moreover, the surveillance to MUP in MRSA should be strengthened to prevent resistance increase due to the expansion of clones.

Herbicide diagnostics reveal multiple patterns of synthetic auxin resistance in kochia (Bassia scoparia)

2021 ◽  
pp. 1-28
Author(s):  
Charles M. Geddes ◽  
Mallory L. Owen ◽  
Teandra E. Ostendorf ◽  
Julia Y. Leeson ◽  
Shaun M. Sharpe ◽  
...  
Keyword(s):  
Great Plains ◽  
Dose Response ◽  
Weed Management ◽  
Acetolactate Synthase ◽  
The United States ◽  
Cross Resistance ◽  
Visible Injury ◽  
Synthetic Auxin ◽  
Auxin Resistance ◽  
Sites Of Action

Abstract Herbicide-resistant (HR) kochia is a growing problem in the Great Plains region of Canada and the United States (U.S.). Resistance to up to four herbicide sites of action, including photosystem II inhibitors, acetolactate synthase inhibitors, synthetic auxins, and the 5-enolpyruvylshikimate-3-phosphate synthase inhibitor glyphosate have been reported in many areas of this region. Despite being present in the U.S. since 1993/1994, auxinic-HR kochia is a recent and growing phenomenon in Canada. This study was designed to characterize (a) the level of resistance and (b) patterns of cross-resistance to dicamba and fluroxypyr in 12 putative auxinic-HR kochia populations from western Canada. The incidence of dicamba-resistant individuals ranged among populations from 0% to 85%, while fluroxypyr-resistant individuals ranged from 0% to 45%. In whole-plant dose-response bioassays, the populations exhibited up to 6.5-fold resistance to dicamba and up to 51.5-fold resistance to fluroxypyr based on visible injury 28 days after application. Based on plant survival estimates, the populations exhibited up to 3.7-fold resistance to dicamba and up to 72.5-fold resistance to fluroxypyr. Multiple patterns of synthetic auxin resistance were observed, where one population from Cypress County, Alberta was resistant to dicamba but not fluroxypyr, while another from Rocky View County, Alberta was resistant to fluroxypyr but not dicamba based on single-dose population screening and dose-response bioassays. These results suggest that multiple mechanisms may confer resistance to dicamba and/or fluroxypyr in Canadian kochia populations. Further research is warranted to determine these mechanisms. Farmers are urged to adopt proactive non-chemical weed management tools in an effort to preserve efficacy of the remaining herbicide options available for control of HR kochia.

2,4-D–Resistant Buckhorn Plantain (Plantago lanceolata) in Managed Turf

2018 ◽  
Vol 32 (2) ◽  
pp. 182-189 ◽  
Author(s):  
Aaron J. Patton ◽  
Daniel V. Weisenberger ◽  
Geoff P. Schortgen
Keyword(s):  
Dose Response ◽  
Plantago Lanceolata ◽  
Resistance Mechanism ◽  
Cross Resistance ◽  
Pyridinecarboxylic Acid ◽  
First Report ◽  
Synthetic Auxin ◽  
Group 4 ◽  
Auxin Herbicides ◽  
Acid Herbicides

AbstractA population of buckhorn plantain with suspected resistance to 2,4-D was identified in central Indiana following 30 yr of 2,4-D–containing herbicide applications. Our objectives were to (1) confirm and quantify the level of herbicide resistance in the buckhorn plantain population using dose–response experiments and (2) find alternative herbicides that could be used to control this population. Greenhouse experiments were conducted to quantify the dose–response of resistant (R) and susceptible (S) biotypes of buckhorn plantain to both 2,4-D and triclopyr, two synthetic auxin herbicides from different chemical families. The R biotype was ≥6.2 times less sensitive to 2,4-D than the S biotype. The efficacy of triclopyr was similar on both the R and S biotypes of buckhorn plantain, suggesting the absence of cross-resistance to this herbicide. This is the first report of 2,4-D resistance in buckhorn plantain and the first report of 2,4-D resistance in turf. The resistance mechanism was limited to within a chemical family (phenoxycarboxylic acid) and did not occur across all WSSA Group 4 synthetic auxin herbicides, as the pyridinecarboxylic acid herbicides clopyralid and triclopyr and the arylpicolinate herbicide halauxifen-methyl provided control in our experiments.

scholarly journals Ser-653-Asn substitution in the acetohydroxyacid synthase gene confers resistance in weedy rice to imidazolinone herbicides imazapic and imazapyr in Malaysia

2019 ◽  
Author(s):  
Rabiatuladawiyah Ruzmi ◽  
M. S. Ahmad-Hamdani ◽  
Norida Mazlan
Keyword(s):  
Dose Response ◽  
Resistance Index ◽  
Rice Cultivar ◽  
Rice Fields ◽  
Target Site ◽  
Acetohydroxyacid Synthase ◽  
Cross Resistance ◽  
Weedy Rice ◽  
Gene Sequences ◽  
Imidazolinone Herbicides

AbstractThe IMI-herbicides rice package has been recognized by all means among the most efficient chemical approaches for weedy rice control nowadays. Inevitably, the continuous and sole dependence, as well as ignorance on the appropriate use of imidazolinone herbicides in the IMI-herbicides rice package by rice growers has caused the development of herbicide resistance in weedy rice populations across many IMI-herbicides rice package adopted countries, inclusive of Malaysia. Hence, a comprehensive study was conducted to elucidate the occurrence, level, and mechanisms endowing resistance to IMI-herbicides on field-reported resistant (R) weedy rice populations collected from IMI-rice fields in Kampung Simpang Sanglang, Perlis (A), Kampung Behor Mentalon, Perlis (B), and Kampung Sungai Kering, Kedah (C). The collected weedy rice populations were compared with a susceptible weedy rice population (S), an imidazolinone-resistant rice cultivar (IMI-rice), and a susceptible local rice cultivar (MR219). Dose-response experiments were carried out using commercial IMI-herbicides (premix of imazapic and imazapyr) available in the IMI-herbicides rice package, in the seed bioassay and whole-plant dose-response. Based on the Resistance Index (RI) quantification in both experiments, the cross-resistance pattern of weedy rice populations and rice varieties to imazapic and imazapyr was determined. Molecular investigation was carried out by comparing acetohydroxyacid synthase (AHAS) gene sequences between resistant (R) weedy rice populations (A, B, and C), S population, IMI-rice, and MR219. Evidently, the AHAS gene sequences of R weedy rice were identical to the IMI-rice, revealing that amino acid substitution of Ser-653-Asn occurs in both R populations and IMI-rice, but neither in MR219 nor S plants. In vitro assays were conducted using analytical grade imidazolinone herbicides of imazapic (99.3%) and imazapyr (99.6%) with seven concentrations. The results demonstrated that the AHAS enzyme extracted from R populations and IMI-rice were less sensitive to IMI-herbicides in comparison to S and MR219, further supporting the IMI-herbicides resistance was conferred by target site mutation. In conclusion, the basis of imidazolinone resistance in selected populations of Malaysia weedy rice was due to a Ser-653-Asn mutation that reduced sensitivity of the target site to IMI-herbicides. The current study presents the first report of resistance mechanism in weedy rice in Malaysian rice fields.

scholarly journals Point Mutations and Cytochrome P450 Can Contribute to Resistance to ACCase-Inhibiting Herbicides in Three Phalaris Species

Plants ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1703
Author(s):  
José G. Vázquez-García ◽  
Joel Torra ◽  
Candelario Palma-Bautista ◽  
Ricardo Alcántara-de la Cruz ◽  
Rafael De Prado
Keyword(s):  
Point Mutations ◽  
Resistance Mechanisms ◽  
Target Site ◽  
In Vitro Assays ◽  
Cross Resistance ◽  
Northern Iran ◽  
Target Site Resistance ◽  
Acetyl Coenzyme A Carboxylase ◽  
Selection Of

Species of Phalaris have historically been controlled by acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides; however, overreliance on herbicides with this mechanism of action has resulted in the selection of resistant biotypes. The resistance to ACCase-inhibiting herbicides was characterized in Phalaris brachystachys, Phalaris minor, and Phalaris paradoxa samples collected from winter wheat fields in northern Iran. Three resistant (R) biotypes, one of each Phalaris species, presented high cross-resistance levels to diclofop-methyl, cycloxydim, and pinoxaden, which belong to the chemical families of aryloxyphenoxypropionates (FOPs), cyclohexanediones (DIMs), and phenylpyrazolines (DENs), respectively. The metabolism of 14C-diclofop-methyl contributed to the resistance of the P. brachystachys R biotype, while no evidence of herbicide metabolism was found in P. minor or P. paradoxa. ACCase in vitro assays showed that the target sites were very sensitive to FOP, DIM, and DEN herbicides in the S biotypes of the three species, while the R Phalaris spp. biotypes presented different levels of resistance to these herbicides. ACCase gene sequencing confirmed that cross-resistance in Phalaris species was conferred by specific point mutations. Resistance in the P. brachystachys R biotype was due to target site and non-target-site resistance mechanisms, while in P. minor and P. paradoxa, only an altered target site was found.

scholarly journals Multiple-and Cross-Resistance of Amaranthus retroflexus to Acetolactate Synthase (ALS) and Photosystem II (PSII) Inhibiting Herbicides in Preemergence

2019 ◽  
Vol 37 ◽  
Author(s):  
A. FRANCISCHINI ◽  
J. CONSTANTIN ◽  
R.S. OLIVEIRA JR ◽  
H.K. TAKANO ◽  
R.R. MENDES
Keyword(s):  
Photosystem Ii ◽  
Herbicide Resistance ◽  
Dose Response ◽  
Acetolactate Synthase ◽  
Amaranthus Retroflexus ◽  
Cross Resistance ◽  
Multiple Resistance ◽  
Mato Grosso ◽  
Application Rates ◽  
Als Inhibitors

ABSTRACT: Herbicide resistance in Amaranthus genus occurs frequently around the word and has become a big problem in cotton producing areas. The objective of this work was to evaluate cross-and multiple-resistance of redroot pigweed (A. retroflexus) to herbicides used in preemergence in cotton fields in Brazil. Seven dose-response experiments were conducted with herbicides atrazine, prometryn, diuron, S-metolachlor, trifluralin, trifloxysulfuron-sodium and pyrithiobac-sodium, and the treatments consisted of application rates of 0, ¼, ½, 1, 2 and 4 times the recommended label rate. Eight A. retroflexus byotipes with suspect of resistance were sampled for experiments in three brazilian states of cotton producing. Resistance to prometryn was confirmed for one biotype in Goiás (GO), and one biotype from Mato Grosso (MT) showed cross-resistance to atrazine and prometryn. One byotipe from GO was identified with cross-resistance to trifloxysulfuron-sodium and pyrithiobac-sodium. One of the GO samples was identified with multiple resistance to prometryn and ALS inhibitors, another one to atrazine and ALS inhibitors, while MT byotipe was confirmed with multiple resistance to triazines and pyrithiobac. The herbicides S-metolachlor, diuron, and trifluralin were efficient for control of this species, therefore, they can be used as managment alternative in those regions.

Mechanisms and phenotypic consequences of acquisition of tigecycline resistance by Stenotrophomonas maltophilia

2019 ◽  
Vol 74 (11) ◽  
pp. 3221-3230 ◽  
Author(s):  
Paula Blanco ◽  
Fernando Corona ◽  
José Luis Martinez
Keyword(s):  
Stenotrophomonas Maltophilia ◽  
Efflux Pump ◽  
Maximum Growth ◽  
Opportunistic Pathogen ◽  
Resistance Mechanisms ◽  
Fitness Cost ◽  
Negative Regulator ◽  
Cross Resistance ◽  
Bacterial Fitness ◽  
High Level

Abstract Objectives To elucidate the potential mutation-driven mechanisms involved in the acquisition of tigecycline resistance by the opportunistic pathogen Stenotrophomonas maltophilia. The mutational trajectories and their effects on bacterial fitness, as well as cross-resistance and/or collateral susceptibility to other antibiotics, were also addressed. Methods S. maltophilia populations were submitted to experimental evolution in the presence of increasing concentrations of tigecycline for 30 days. The genetic mechanisms involved in the acquisition of tigecycline resistance were determined by WGS. Resistance was evaluated by performing MIC assays. Fitness of the evolved populations and individual clones was assessed by measurement of the maximum growth rates. Results All the tigecycline-evolved populations attained high-level resistance to tigecycline following different mutational trajectories, yet with some common elements. Among the mechanisms involved in low susceptibility to tigecycline, mutations in the SmeDEF efflux pump negative regulator smeT, changes in proteins involved in the biogenesis of the ribosome and modifications in the LPS biosynthesis pathway seem to play a major role. Besides tigecycline resistance, the evolved populations presented cross-resistance to other antibiotics, such as aztreonam and quinolones, and they were hypersusceptible to fosfomycin, suggesting a possible combination treatment. Further, we found that the selected resistance mechanisms impose a relevant fitness cost when bacteria grow in the absence of antibiotic. Conclusions Mutational resistance to tigecycline was easily selected during exposure to this antibiotic. However, the fitness cost may compromise the maintenance of S. maltophilia tigecycline-resistant populations in the absence of antibiotic.

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