scholarly journals Resistance Mechanisms to 2,4-D in Six Different Dicotyledonous Weeds Around the World

Agronomy ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 566 ◽  
Author(s):  
Candelario Palma-Bautista ◽  
Antonia M. Rojano-Delgado ◽  
Ignacio Dellaferrera ◽  
Jesús M. Rosario ◽  
Mario R. Vigna ◽  
...  
Keyword(s):  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Conyza Canadensis ◽  
Weed Species ◽  
Amaranthus Hybridus ◽  
Resistance Factors ◽  
Herbicide Degradation ◽  
The World ◽  
Differential Contribution

2,4-D resistance is increasing around the world due to both transgenic crops and resistance to other herbicides. The objective of the this study was to characterize the currently unknown mechanisms of 2,4-D resistance in five weed species from around the globe: Amaranthus hybridus (Argentina), Conyza canadensis (Hungary), Conyza sumatrensis (France), Hirschfeldia incana (Argentina) and Parthenium hysterophorus (Dominican Republic), using Papaver rhoeas (Spain) as a standard resistant (R) species. Dose-response trials using malathion and absorption, translocation and metabolism experiments were performed to unravel the resistance mechanisms. R plants produced at least 3-folds less ethylene than susceptible plants, confirming the resistance to 2,4-D, together with resistance factors >4. A. hybridus, P. hysterophorus and P. rhoeas showed both reduced translocation and enhanced metabolism. In the two Conyza sps., the only resistance mechanism found was enhanced metabolism. Malathion synergized with 2,4-D in all these species, indicating the role of cytochrome P450 in the herbicide degradation. In H. incana, reduced translocation was the only contributing mechanism to resistance. Among the six dicotyledonous weed species investigated, there was a differential contribution to 2,4-D resistance of enhanced metabolism and reduced translocation. Thus, extrapolating 2,4-D resistance mechanisms from one weed species to another is very risky, if even related.

Target and Non–target site Mechanisms Confer Resistance to Glyphosate in Canadian Accessions ofConyza canadensis

Weed Science ◽  
2017 ◽  
Vol 66 (2) ◽  
pp. 234-245 ◽  
Author(s):  
Eric R. Page ◽  
Christopher M. Grainger ◽  
Martin Laforest ◽  
Robert E. Nurse ◽  
Istvan Rajcan ◽  
...  
Keyword(s):  
Ssr Markers ◽  
Resistance Mechanisms ◽  
Target Site ◽  
Conyza Canadensis ◽  
Weed Species ◽  
Target Site Resistance ◽  
Selection For ◽  
Simple Sequence ◽  
Growing Region ◽  
Selection Of

Glyphosate-resistant populations ofConyza canadensishave been spreading at a rapid rate in Ontario, Canada, since first being documented in 2010. Determining the genetic relationship among existing Ontario populations is necessary to understand the spread and selection of the resistant biotypes. The objectives of this study were to: (1) characterize the genetic variation ofC. canadensisaccessions from the province of Ontario using simple sequence repeat (SSR) markers and (2) investigate the molecular mechanism (s) conferring resistance in these accessions. Ninety-eightC. canadensisaccessions were genotyped using 8 SSR markers. Germinable accessions were challenged with glyphosate to determine their dose response, and the sequences of 5-enolpyruvylshikimate-3-phosphate synthase genes 1 and 2 were obtained. Results indicate that a majority of glyphosate-resistant accessions from Ontario possessed a proline to serine substitution at position 106, which has previously been reported to confer glyphosate resistance in other crop and weed species. Accessions possessing this substitution demonstrated notably higher levels of resistance than non–target site resistant (NTSR) accessions from within or outside the growing region and were observed to form a subpopulation genetically distinct from geographically proximate glyphosate-susceptible and NTSR accessions. Although it is unclear whether other non–target site resistance mechanisms are contributing to the levels of resistance observed in target-site resistant accessions, these results indicate that, at a minimum, selection for Pro-106-Ser has occurred in addition to selection for non–target site resistance and has significantly enhanced the levels of resistance to glyphosate inC. canadensisaccessions from Ontario.

Evolved Glyphosate Resistance in Plants: Biochemical and Genetic Basis of Resistance

2006 ◽  
Vol 20 (2) ◽  
pp. 282-289 ◽  
Author(s):  
Stephen B. Powles ◽  
Christopher Preston
Keyword(s):  
Amino Acid ◽  
Resistance Mechanism ◽  
Nuclear Gene ◽  
Glyphosate Resistance ◽  
The United States ◽  
Resistance Mechanisms ◽  
Italian Ryegrass ◽  
Weed Species ◽  
Epsps Gene ◽  
Rigid Ryegrass

Resistance to the herbicide glyphosate is currently known in at least eight weed species from many countries. Some populations of goosegrass from Malaysia, rigid ryegrass from Australia, and Italian ryegrass from Chile exhibit target site–based resistance to glyphosate through changes at amino acid 106 of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene. Mutations change amino acid 106 from proline to either serine or threonine, conferring an EPSPS weakly resistant to glyphosate. The moderate level of resistance is sufficient for commercial failure of the herbicide to control these plants in the field. Conversely, a nontarget site resistance mechanism has been documented in glyphosate-resistant populations of horseweed and rigid ryegrass from the United States and Australia, respectively. In these resistant plants, there is reduced translocation of glyphosate to meristematic tissues. Both of these mechanisms are inherited as a single, nuclear gene trait. Although at present only two glyphosate-resistance mechanisms are known, it is likely that other mechanisms will become evident. The already very large and still increasing reliance on glyphosate in many parts of the world will inevitably result in more glyphosate-resistant weeds, placing the sustainability of this precious herbicide resource at risk.

scholarly journals Exogenous Oxalic Acid and Citric Acid Improve Lead (Pb) Tolerance of Larix olgensis A. Henry Seedlings

Forests ◽  
2018 ◽  
Vol 9 (9) ◽  
pp. 510 ◽  
Author(s):  
JinFeng Song ◽  
Daniel Markewitz ◽  
Shaoping Wu ◽  
Ying Sang ◽  
Chengwei Duan ◽  
...  
Keyword(s):  
Citric Acid ◽  
Plant Growth ◽  
Oxalic Acid ◽  
Organic Acids ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Internal Resistance ◽  
Larix Olgensis ◽  
Detoxification Mechanism

We investigated the beneficial role of different concentrations of exogenous oxalic acid (OA) or citric acid (CA) for improving Pb tolerance and mitigating Pb-induced physiological toxicity in Changbai larch (Larix olgensis A. Henry) seedlings in northeast China. The seedlings were exposed to 100 mg·kg−1 Pb in soil alone or in combination with OA or CA irrigation for 10, 20, or 30 days. Pb-induced damage in L. olgensis was evident from elevated lipid peroxidation that significantly inhibited plant growth. Malondialdehyde (MDA) contents also increased in the presence of elevated Pb; however, superoxide dismutase (SOD) and peroxidase (POD) activities, as well as proline and pigment contents, all decreased. The damage increased in controls over the application periods. Pb contents in fine roots and leaves generally decreased with low-concentration organic acids (<1.0 mmol·L−1), but often increased at 5.0 and 10.0 mmol·L−1. Alternatively, when Pb-stressed plants were exposed to an organic acid (especially 5.0 or 10.0 mmol·L−1 for 10 days), the damage, as indicated by the physiological parameters, was reversed, and plant growth was promoted; CA was more effective in inducing these changes than OA. Therefore, exogenous organic acids have the potential to alleviate Pb-induced oxidative injuries, and can improve the tolerance of L. olgensis seedlings to Pb stress. Under lower OA and CA concentrations, the detoxification mechanism appears to be an external resistance mechanism; however, under higher concentrations (5.0–10.0 mmol·L−1) internal resistance mechanisms appear dominant. It is also possible that the two mechanisms work in tandem.

scholarly journals Multiple mutations in the EPSPS and ALS genes of Amaranthus hybridus underlie resistance to glyphosate and ALS inhibitors

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Maria J. García ◽  
Candelario Palma-Bautista ◽  
José G. Vazquez-Garcia ◽  
Antonia M. Rojano-Delgado ◽  
María D. Osuna ◽  
...  
Keyword(s):  
Amino Acid ◽  
Target Genes ◽  
Acetolactate Synthase ◽  
Resistance Mechanisms ◽  
Activity Level ◽  
Cross Resistance ◽  
Weed Species ◽  
Amaranthus Hybridus ◽  
Als Inhibitors ◽  
Moderate Resistance

Abstract Amaranthus hybridus is one of the main weed species in Córdoba, Argentina. Until recently, this weed was effectively controlled with recurrent use of glyphosate. However, a population exhibiting multiple resistance (MR2) to glyphosate and imazamox appeared in a glyphosate resistant (GR) soybean field, with levels of resistance up to 93 and 38-fold higher to glyphosate and imazamox, respectively compared to the susceptible (S) population. In addition to imidazolinones, MR2 plants showed high resistance levels to sulfonylamino-carbonyl (thio) benzoates and moderate resistance to sulfonylureas and triazolopyrimidines. Multiple amino acid substitutions were found in both target genes, acetolactate synthase (ALS) and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), responsible for conferring high herbicides resistance levels in this A. hybridus population. In the case of EPSPS, the triple amino acid substitution TAP-IVS was found. In addition, MR2 plants also showed increased EPSPS gene expression compared to susceptible plants. A Ser653Asn substitution was found in the ALS sequence of MR2, explaining the pattern of cross-resistance to the ALS-inhibitor herbicide families found at the ALS enzyme activity level. No other mutations were found in other conserved domains of the ALS gene. This is the first report worldwide of the target site resistance mechanisms to glyphosate and ALS inhibitors in multiple herbicide resistance Amaranthus hybridus.

scholarly journals Fluoroquinolone Metalloantibiotics to Bypass Antimicrobial Resistance Mechanisms: Decreased Permeation through Porins

Membranes ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 3
Author(s):  
Mariana Ferreira ◽  
Carla F. Sousa ◽  
Paula Gameiro
Keyword(s):  
Antimicrobial Resistance ◽  
Membrane Permeability ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Gram Positive Bacteria ◽  
Specific Association ◽  
Location Association

Fluoroquinolones (FQs) are broad-spectrum antibiotics largely used in the clinical practice against Gram-negative and some Gram-positive bacteria. Nevertheless, bacteria have developed several antimicrobial resistance mechanisms against such class of antibiotics. Ternary complexes of FQs, copper(II) and phenanthroline, known as metalloantibiotics, arise in an attempt to counteract an antibiotic resistance mechanism related to low membrane permeability. These metalloantibiotics seem to use an alternative influx route, independent of porins. The translocation pathways of five FQs and its metalloantibiotics were studied through biophysical experiments, allowing us to infer about the role of OmpF porin in the influx. The FQ-OmpF interaction was assessed in mimetic membrane systems differing on the lipidic composition, disclosing no interference of the lipidic composition. The drug-porin interaction revealed similar values for the association constants of FQs and metalloantibiotics with native OmpF. Therefore, OmpF mutants and specific quenchers were used to study the location-association relationship, comparing a free FQ and its metalloantibiotic. The free FQ revealed a specific association, with preference for residues on the centre of OmpF, while the metalloantibiotic showed a random interaction. Thereby, metalloantibiotics may be an alternative to pure FQs, being able to overcome some antimicrobial resistance mechanism of Gram-negative bacteria related to decreased membrane permeability.

Resistance mechanisms to mitochondrial electron transport inhibitors in a field-collected strain of Tetranychus urticae Koch (Acari: Tetranychidae)

2008 ◽  
Vol 99 (1) ◽  
pp. 23-31 ◽  
Author(s):  
S. Van Pottelberge ◽  
T. Van Leeuwen ◽  
R. Nauen ◽  
L. Tirry
Keyword(s):  
Electron Transport ◽  
Tetranychus Urticae ◽  
Resistance Mechanism ◽  
Fold Increase ◽  
Resistance Mechanisms ◽  
Metabolic Inhibitors ◽  
Metabolic Resistance ◽  
Monooxygenase Activity ◽  
Resistance Factors ◽  
Pre Treatment

AbstractA Belgian field strain (MR-VP) of Tetranychus urticae (Koch) (Acari: Tetranychidae) exhibits different levels of resistance to four frequently used METI (mitochondrial electron transport inhibitor)-acaricides, i.e. tebufenpyrad, fenpyroximate, pyridaben and fenazaquin. Resistance factors for these compounds were 184, 1547, 5971 and 35, respectively. A 23.5-fold increase in 7-ethoxy-4-trifluoromethylcoumarin O-deethylation activity suggested that metabolic resistance through elevated levels of cytochrome P450 dependent monooxygenase-activity is a possible resistance mechanism.However, synergism studies with different metabolic inhibitors revealed some contrasting resistance mechanisms between the METI-acaricides. Tebufenpyrad resistance could only be synergized after pre-treatment with the monooxygenase inhibitor piperonyl butoxide (PBO), whereas pyridaben resistance was strongly synergized both by PBO and the esterase inhibitor S,S,S-tributylphosphorotrithioate (DEF). Resistance levels to fenpyroximate could neither be suppressed by PBO nor by DEF. Although METI-acaricides are structurally related, these findings probably reflect a different role of esterases and mono-oxygenases in metabolic detoxification between these compounds. The overall lack of synergism by diethylmaleate (DEM) suggests that glutathione-S-transferases are not an important factor in resistance to METIs.Reciprocal crosses between susceptible females and resistant males showed no maternal effect, and resistance to METI-acaricides was inherited generally as a dominant trait. Backcrosses with F1 females revealed striking differences in the mode of inheritance. Although resistance to fenpyroximate and pyridaben was under monogenic control, resistance to tebufenpyrad was under control of more than one gene.

Resistance Status to Deltamethrin, Permethrin, and Temephos Along With Preliminary Resistance Mechanism in Aedes aegypti (Diptera: Culicidae) From Punjab, Pakistan

2019 ◽  
Vol 56 (5) ◽  
pp. 1304-1311 ◽  
Author(s):  
Hafiz Azhar Ali Khan ◽  
Waseem Akram
Keyword(s):  
Aedes Aegypti ◽  
Insecticide Resistance ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Target Site Resistance ◽  
Control Failure ◽  
Moderate Resistance ◽  
High Level ◽  
Nonsignificant Effect

Abstract The use of insecticides such as deltamethrin, permethrin, and temephos has been a primary tool to manage Aedes aegypti (Linnaeus) in Punjab province, Pakistan; however, recent reports of control failure necessitate monitoring insecticide resistance. For this reason, we evaluated 12 field strains of Ae. aegypti from Punjab for resistance against deltamethrin, permethrin, and temephos along with underlying resistance mechanisms. For deltamethrin, high level of resistance was observed in Rawalpindi, Faisalabad, Sheikhupura, Lahore, Pattoki, and Kasur strains (RRLC50 > 10-fold); moderate level of resistance in Sargodha, Gujranwala, and Sialkot strains (RRLC50 = 5- to 10-fold), and low level of resistance in Okara, Multan, and Sahiwal strains (RRLC50 < 5-fold). In the case of permethrin, high level of resistance was found in all the field strains, except the Okara strain that exhibited moderate resistance. For temephos, five field strains, viz. Faisalabad, Rawalpindi, Kasur, Lahore, and Gujranwala, showed high level of resistance; five strains, viz. Sheikhupura, Sialkot, Pattoki, Sahiwal, and Okara, showed moderate resistance, and two strains from Multan and Sargodha showed low resistance to temephos. Synergism bioassays implementing piperonyl butoxide and S,S,S-tributylphosphorotrithioate exhibited a nonsignificant effect on synergizing toxicity of deltamethrin and permethrin in all field strains except the Lahore strain, suggesting the possible role of target-site resistance mechanism. However, both synergists had a significant effect on synergizing toxicity of temephos in all field strains, suggesting the possibility of metabolic-based mechanism of insecticide resistance. In conclusion, the study confirmed the presence of resistance to deltamethrin, permethrin, and temephos in the studied field strains of Ae. aegypti from Punjab, Pakistan.

Penicillin-binding proteins of Bacteroides fragilis and their role in the resistance to imipenem of clinical isolates

2005 ◽  
Vol 54 (11) ◽  
pp. 1055-1064 ◽  
Author(s):  
Juan Ayala ◽  
Alberto Quesada ◽  
Santiago Vadillo ◽  
Jerónimo Criado ◽  
Segundo Píriz
Keyword(s):  
Binding Proteins ◽  
Antimicrobial Agents ◽  
Resistance Mechanism ◽  
Bacteroides Fragilis ◽  
Resistance Mechanisms ◽  
Gene Encoding ◽  
Penicillin Binding Proteins ◽  
Mechanism Of Resistance

In this study penicillin-binding proteins (PBPs) of Bacteroides fragilis and the resistance mechanisms of this micro-organism to 11 β-lactam antibiotics were analysed. The study focused on the role of PBP2Bfr and metallo-β-lactamase in the mechanism of resistance to imipenem. The mechanism of β-lactam resistance in B. fragilis was strain dependent. The gene encoding the orthologue of Escherichia coli PBP3 gene (pbpBBfr, which encodes the protein PBP2Bfr) was sequenced in five of the eight strains studied, along with the ccrA (cfiA) gene in strain 119, and their implications for resistance were examined. Differences were found in the amino-acid sequence of PBP2Bfr in strains AK-2 and 119, and the production of β-lactamases indicated that these differences may be involved in the mechanism of resistance to imipenem. In vitro binding competition assays with membrane extracts using imipenem indicated that the PBP that bound imipenem with the highest affinity was PBP2Bfr, and that increased affinity in strain 7160 may be responsible for the moderate susceptibility of this strain to imipenem. In the same way, the importance of the chromosomal class A β-lactamase CepA in the resistance mechanism of the B. fragilis strains NCTC 9344, 7160, 2013E, AK-4, 0423 and R-212 was studied. In these strains this is the principal resistance mechanism to antimicrobial agents studied other than imipenem.

scholarly journals Herbicide Metabolism: Crop Selectivity, Bioactivation, Weed Resistance, and Regulation

Weed Science ◽  
2019 ◽  
Vol 67 (2) ◽  
pp. 149-175 ◽  
Author(s):  
Vijay K. Nandula ◽  
Dean E. Riechers ◽  
Yurdagul Ferhatoglu ◽  
Michael Barrett ◽  
Stephen O. Duke ◽  
...  
Keyword(s):  
Resistance Mechanisms ◽  
Cytochrome P450 Monooxygenases ◽  
Weed Species ◽  
Metabolic Resistance ◽  
Crop Tolerance ◽  
P450 Monooxygenases ◽  
Current State ◽  
The World ◽  
Herbicide Metabolism ◽  
State Of Research

AbstractSeveral grass and broadleaf weed species around the world have evolved multiple-herbicide resistance at alarmingly increasing rates. Research on the biochemical and molecular resistance mechanisms of multiple-resistant weed populations indicate a prevalence of herbicide metabolism catalyzed by enzyme systems such as cytochrome P450 monooxygenases and glutathioneS-transferases and, to a lesser extent, by glucosyl transferases. A symposium was conducted to gain an understanding of the current state of research on metabolic resistance mechanisms in weed species that pose major management problems around the world. These topics, as well as future directions of investigations that were identified in the symposium, are summarized herein. In addition, the latest information on selected topics such as the role of safeners in inducing crop tolerance to herbicides, selectivity to clomazone, glyphosate metabolism in crops and weeds, and bioactivation of natural molecules is reviewed.

A review of control methods and resistance mechanisms in stored-product insects

2011 ◽  
Vol 102 (2) ◽  
pp. 213-229 ◽  
Author(s):  
S. Boyer ◽  
H. Zhang ◽  
G. Lempérière
Keyword(s):  
Genetic Resistance ◽  
Resistance Mechanisms ◽  
Economic Importance ◽  
Multiple Resistance ◽  
Control Methods ◽  
Detoxifying Enzymes ◽  
The World ◽  
Behavioral Resistance ◽  
Mutation Mechanisms

AbstractThis review describes the major stored-product insect species and their resistance to insecticides. The economic importance of the control of those pests is highlighted with a loss of more than one billion US dollars per year worldwide. A detailed common description of species resistance throughout the world has been developed, and we observed 28 recurrent studied species involved in resistance cases disseminated on the five continents. The different mechanisms, including behavioral resistance, were studied particularly on Oryzaephilus surinamensis. The role of detoxifying enzymes and studies on the genetic resistance, involving the kdr mutation mechanisms and the transmission of the genes of resistance, are also described. A chapter clarifying definitions on cross and multiple resistance is enclosed.

Sign in / Sign up

Export Citation Format

Share Document