Molecular Basis of Resistance to Tribenuron in Water Starwort (Myosoton aquaticum) Populations from China

Weed Science ◽  
2013 ◽  
Vol 61 (3) ◽  
pp. 390-395 ◽  
Author(s):  
Weitang Liu ◽  
Yaling Bi ◽  
Lingxu Li ◽  
Guohui Yuan ◽  
Jinxin Wang
Keyword(s):  
Molecular Basis ◽  
Inhibitory Concentration ◽  
Acetolactate Synthase ◽  
Susceptible Population ◽  
Documented Case ◽  
Whole Plant ◽  
Winter Annual ◽  
High Level ◽  
Plant Bioassays

Populations of water starwort, a winter annual or biennial weed in the pink family (Caryophyllaceae), can no longer be controlled by tribenuron following successive use of this herbicide over several years. Whole-plant bioassays have established that the resistant water starwort populations JS17, JS08, JS16, and JS07 showed high-level (from 203-fold to 565-fold) resistance to tribenuron. In vitro acetolactate synthase (ALS) assays revealed that resistance was due to reduced sensitivity of the ALS enzyme to tribenuron. The half-maximal inhibitory concentration (I50) values for JS17, JS08, JS16, and JS07 were 72, 71, 70, and 76 times greater, respectively, than were those of the susceptible population JS24. This altered ALS sensitivity in the resistant populations was due to a mutation in the ALS gene resulting in a Pro197to Ser substitution (JS17, JS08, and JS16) and a Pro197to Leu substitution (JS07). This study established the first documented case, to our knowledge, of evolved tribenuron resistance in water starwort and concluded that the molecular basis of resistance is due, at least in part, to a target-site modification at Pro197in the ALS gene.

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

Weed Science ◽  
1996 ◽  
Vol 44 (3) ◽  
pp. 757-762 ◽  
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.

First report of molecular basis of resistance to imazethapyr in common lambsquarters (Chenopodium album)

Weed Science ◽  
2019 ◽  
pp. 1-6
Author(s):  
Zhaofeng Huang ◽  
Xinxin Zhou ◽  
Chaoxian Zhang ◽  
Cuilan Jiang ◽  
Hongjuan Huang ◽  
...  
Keyword(s):  
Herbicide Resistance ◽  
Chenopodium Album ◽  
Acetolactate Synthase ◽  
Amino Acid Position ◽  
Cross Resistance ◽  
Resistance Pattern ◽  
Susceptible Population ◽  
First Report ◽  
Common Lambsquarters

Abstract Common lambsquarters (Chenopodium album L.) is one of the most troublesome weeds in soybean [Glycine max (L.) Merr.] and corn (Zea mays L.) fields in northeast China. In 2017, a C. album population that survived imazethapyr at the recommended field rate was collected from a soybean field in Heilongjiang Province in China. Experiments were conducted to determine the basis of resistance to imazethapyr and investigate the herbicide-resistance pattern in C. album. Dose–response tests showed that the resistant population (R) displayed high resistance to imazethapyr (20-fold) compared with the susceptible population (S). An in vitro acetolactate synthase (ALS) activity assay indicated that the ALS of the R population was resistant to imazethapyr compared with the ALS of the S population. Sequence analysis of the ALS gene revealed that the GCA was replaced by ACA at amino acid position 122, which resulted in an alanine to threonine substitution (Ala-122-Thr) in the R population. The R population displayed cross-resistance to thifensulfuron-methyl and flumetsulam but susceptibility to bispyribac-sodium, flucarbazone, glyphosate, mesotrione, and fomesafen. These results confirmed that the basis of imazethapyr resistance in C. album was conferred by the Ala-122-Thr substitution in the ALS enzyme. This is the first report of the target-site basis of ALS-inhibiting herbicide resistance in C. album.

Thermal dependence of pyrithiobac efficacy inAmaranthus palmeri

Weed Science ◽  
1999 ◽  
Vol 47 (6) ◽  
pp. 644-650 ◽  
Author(s):  
Ginger G. Light ◽  
Peter A. Dotray ◽  
James R. Mahan
Keyword(s):  
Weed Control ◽  
Acetolactate Synthase ◽  
Field Studies ◽  
Thermal Dependence ◽  
Growing Seasons ◽  
Air Temperatures ◽  
Whole Plant ◽  
Crude Leaf Extract ◽  
Highly Correlated

Variability in weed control following pyrithiobac applications has been observed under field conditions. The influence of temperature on this variability was investigated. Results from field studies performed over two growing seasons identified plant and air temperatures at the time of herbicide treatment that correlated with whole-plant efficacy differences. Based on the field data, weed control with pyrithiobac was acceptable at application temperatures of 20 to 34 C. To investigate a potential source of thermal limitations on pyrithiobac efficacy, the thermal dependence of in vitro inhibition of acetolactate synthase (ALS), the site of action for pyrithiobac, was examined. A crude leaf extract of ALS was obtained fromAmaranthus palmeri. Relative inhibitor potency (I50) values were obtained at saturating substrate conditions for temperatures from 10 to 50 C. Regression analysis of field activity against I50values showed the two data sets to be highly correlated (R2= 0.88). The thermal dependence of enzyme/herbicide interactions may provide another means of understanding environmental factors limiting herbicidal efficacy and predicting herbicide inhibition at the whole-plant level.

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

Weed Science ◽  
2011 ◽  
Vol 59 (3) ◽  
pp. 431-437 ◽  
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.

Acetolactate Synthase Gene Proline (197) Mutations Confer Tribenuron-Methyl Resistance in Flixweed (Descurainia sophia) Populations from China

Weed Science ◽  
2011 ◽  
Vol 59 (3) ◽  
pp. 376-379 ◽  
Author(s):  
Hai Lan Cui ◽  
Chao Xian Zhang ◽  
Shou Hui Wei ◽  
Hong Jun Zhang ◽  
Xiang Ju Li ◽  
...  
Keyword(s):  
Amino Acid ◽  
Molecular Basis ◽  
Resistance Mechanism ◽  
Point Mutations ◽  
Acetolactate Synthase ◽  
Amino Acid Position ◽  
Resistance Level ◽  
Coding Sequence ◽  
Whole Plant ◽  
Tribenuron Methyl

The molecular basis of resistance to tribenuron-methyl, an acetolactate synthase (ALS)–inhibiting herbicide was investigated in four resistant (R) and three susceptible (S) flixweed populations. The resistance level in the R populations was assessed in whole-plant pot experiments in a greenhouse, and resistance indices ranged from 723 to 1422. The ALS genes of the three S populations and four R populations were cloned and sequenced, and the full coding sequence of the ALS gene of flixweed was 2,004 bp. The sequences of the ALS genes of the three S populations collected from Shaanxi, Gansu, and Tianjin were identical. Comparison of the ALS gene sequences of the S and R populations withArabidopsisrevealed that proline at position 197 of the ALS gene was substituted by leucine in R population SSX-2, by alanine in R population SSX-3, and by serine in R populations TJ-2 and GS-2. In another study of two R flixweed populations from Hebei and Shaanxi, resistance was also related to mutation at position 197 of the ALS gene. Both studies confirmed tribenuron-methyl resistance in flixweed in China, with the resistance mechanism being conferred by specific ALS point mutations at amino acid position 197.

ID: 49: STUDY OF MINIMUM INHIBITORY CONCENTRATION OF CEFAZOLIN FOR METHICILLIN SENSITIVE STAPHYLOCOCCUS AUREUS AND CORRELATION WITH OXACILLIN SUSCEPTIBILITY

2016 ◽  
Vol 64 (4) ◽  
pp. 954.2-954
Author(s):  
C Quarshie ◽  
J Koirala ◽  
V Sundareshan
Keyword(s):  
Staphylococcus Aureus ◽  
Standard Deviation ◽  
Minimum Inhibitory Concentration ◽  
Inhibitory Concentration ◽  
Medical Center ◽  
Generation Cephalosporin ◽  
In Vitro Susceptibility ◽  
Suitable Alternative ◽  
High Level

BackgroundCefazolin, a first generation cephalosporin, has been used for the treatment of Methicillin Sensitive Staphylococcus aureus (MSSA) infections since the 1970s. There have now been reported cases of failed therapy with cefazolin. High-level β-lactamase producing strains of S. aureus can inactivate the susceptible β-lactam (cefazolin) at a rate high enough to overcome its antibacterial effect. These strains typically have a high Minimum Inhibitory Concentration (MIC) for cefazolin when a large inoculum is used. About 20% of MSSA isolates have been shown to have a substantial inoculum effect suggesting that cefazolin treatment might be associated with clinical failure in serious MSSA infections. The minimum inhibition concentration (MIC) for cefazolin is not provided on all standard sensitivity panels and susceptibility is extrapolated from the report on oxacillin. The goal of this study was to analyze the MIC of cefazolin for MSSA isolates to determine the correlation of cefazolin susceptibility and in vitro susceptibility of oxacillin. We also evaluated the MIC of alternative antibiotics as part of this study for use in patients that might be allergic to penicillin.MethodThirty two isolates of MSSA were randomly selected from repositories of isolates at Memorial Medical Center hospital's microbiology department from 2015. The isolates were from patients with a wide variety of diagnoses, including bacteremia, osteomyelitis and wound infections. S. aureus ATCC 29213 was used as controls. MICs were determined by a Kirby Bauer method for cefazolin and Epsilometer test for other antibiotics that were studied. Inocula were standardized using optical density measurements, with determinations of CFU/ml to determine the inoculum concentrations. IN addition to cefazolin, we obtained the MIC for daptomycin, oxacillin, ceftaroline and telavancin as well.ResultsOf the thirty two MSSA isolates tested, 100% were susceptible to cefazolin. The mean zone of inhibition (ZOI) was 29.18 with standard deviation of 3.67 for cefazolin (29–35 mm ZOI with ATCC strains of MSSA) . All the isolates were susceptible to Oxacillin with mean MIC of 0.7735 with standard deviation of 0.30. Daptomycin, ceftaroline and telavancin were 100% susceptible with mean MIC of 0.27, 0.25, and 0.07, respectively. All isolates were studied for the alternate antibiotics and no resistance was noted.ConclusionThe MIC of cefazolin for MSSA determined by in vitro susceptibility to oxacillin was entirely in the susceptible range with 100% correlation. Daptomycin, ceftaroline and telavancin are suitable alternative antibiotics for treatment of patients with infections due to MSSA in whom anti-staphylococcal penicillins cannot be used due to penicillin allergic, intolerance, and/or non-availability since there is not much resistance to these antibiotics in MSSA.

A Target-Site Point Mutation in Henbit (Lamium amplexicaule) Confers High-Level Resistance to ALS-Inhibitors

Weed Science ◽  
2016 ◽  
Vol 64 (2) ◽  
pp. 231-239 ◽  
Author(s):  
Vijay K. Varanasi ◽  
Amar S. Godar ◽  
Dallas E. Peterson ◽  
Doug Shoup ◽  
Mithila Jugulam
Keyword(s):  
Point Mutation ◽  
Resistance Index ◽  
Acetolactate Synthase ◽  
Common Mutation ◽  
First Case ◽  
Winter Annual ◽  
Rapid Amplification ◽  
Als Inhibitors ◽  
High Level ◽  
Dna Ends

Henbit is a facultative broadleaf winter annual in the Lamiaceae family. Acetolactate synthase (ALS) inhibitors are primarily used to control a broad spectrum of weeds, including henbit. During 2012 to 2013, field applications of ALS-inhibiting herbicides were ineffective in controlling a henbit population from Marion County, KS (MCK). To confirm field-evolved resistance to ALS inhibitors, response of MCK henbit and a known susceptible henbit population from Kansas (DPS) to varying doses of three different ALS inhibitors were examined: chlorsulfuron, imazamox, and propoxycarbazone. Results of the dose–response experiments suggest that the MCK population is highly resistant to chlorsulfuron (resistance index [R/S] > 1,000) and propoxycarbazone (R/S = 331) but is susceptible to imazamox. A full-lengthALSgene sequence obtained using the 5′- and 3′- rapid amplification of complementary DNA ends approach revealed a Pro197to Arg point mutation (a common mutation that confers resistance to sulfonylurea herbicides, e.g., chlorsulfuron) in the MCK henbit. No other known resistance-conferring mutations were found in the study. Evolved resistance to major classes of ALS inhibitors in the MCK henbit will reduce herbicide options for its control. To our knowledge, this is the first case of evolution of herbicide resistance in henbit.

Target-Site Resistance to Fenoxaprop-P-ethyl in Keng Stiffgrass (Sclerochloa kengiana) from China

Weed Science ◽  
2017 ◽  
Vol 65 (4) ◽  
pp. 452-460 ◽  
Author(s):  
Haitao Gao ◽  
Jiaxing Yu ◽  
Lang Pan ◽  
Xibao Wu ◽  
Liyao Dong
Keyword(s):  
Eastern China ◽  
Point Mutations ◽  
Amino Acid Position ◽  
Cross Resistance ◽  
Susceptible Population ◽  
Resistant Population ◽  
Sequence Method ◽  
Moderate Resistance ◽  
High Level

Keng stiffgrass is a serious farmland grass weed distributed globally in winter wheat fields and rice–wheat double-cropping areas. The intensive use of acetyl-CoA carboxylase (ACCase)-inhibiting herbicides has led to the evolution of resistance in a growing number of grass weeds. In this study, whole-plant pot bioassay experiments were conducted to establish that a Keng stiffgrass population from eastern China, JYJD-2, has evolved high-level resistance to fenoxaprop-P-ethyl and moderate resistance to quizalofop-P-ethyl and pinoxaden. Using the derived cleaved amplified polymorphic sequence method, a tryptophan-to-cysteine mutation at codon position 1999 (W1999C) was detected in the ACCase gene of the resistant population JYJD-2. Of the 100 JYJD-2 plants tested, we found 47 heterozygous resistant and 53 homozygous sensitive individuals. In vitro ACCase assays revealed that the IC50value of the ACCase activity of the resistant population JYJD-2 was 6.48-fold higher than that of the susceptible population JYJD-1. To the best of our knowledge, this is the first report of the occurrence of W1999C mutation in the ACCase gene of fenoxaprop-P-ethyl–resistant Keng stiffgrass. This study confirmed the resistance of Keng stiffgrass to the ACCase inhibitor fenoxaprop-P-ethyl, cross-resistance to other ACCase inhibitors, and the resistance being conferred by specific ACCase point mutations at amino acid position 1999.

A Putative Prodiamine-Resistant Annual Bluegrass (Poa annua) Population is Controlled by Indaziflam

Weed Science ◽  
2014 ◽  
Vol 62 (1) ◽  
pp. 138-144 ◽  
Author(s):  
James T. Brosnan ◽  
Eric H. Reasor ◽  
Jose J. Vargas ◽  
Gregory K. Breeden ◽  
Dean A. Kopsell ◽  
...  
Keyword(s):  
Root Growth ◽  
Acetolactate Synthase ◽  
Field Trials ◽  
Golf Course ◽  
Future Research ◽  
Cellulose Biosynthesis ◽  
Susceptible Population ◽  
Annual Bluegrass ◽  
The Past ◽  
Whole Plant

Prodiamine is a mitotic inhibiting herbicide regularly used to control annual bluegrass PRE. A population of annual bluegrass not controlled by prodiamine at 1,120 g a.i. ha−1was identified on a golf course in Alcoa, TN, in 2012. A whole-plant hydroponics bioassay was used to screen this biotype for prodiamine resistance (PR) compared with a known susceptible population (SS). Multitiller (i.e., > 4 tillers) PR and SS annual bluegrass plants were established in hydroponic culture and exposed to 0, 0.001, 0.01, 0.10, 1.0, and 10.0 mM prodiamine. Exposure to prodiamine at 0.001 mM reduced root growth of the SS biotype to 26% of the nontreated check (i.e., 0 mM prodiamine) but had no effect on the PR biotype. When exposed to 10 mM prodiamine, root growth of the PR biotype was reduced to 24% of the nontreated check compared with 9% for the SS biotype.I50values for the PR and SS biotypes were 0.04 and 2.8 × 10−6mM prodiamine, respectively. The PR biotype measured lower in plant height and leaf width than the SS population. In field trials, prodiamine at 560, 840, 1,120, and 1,400 g ha−1only controlled the PR biotype 0 to 22%. PRE applications of the cellulose biosynthesis inhibitor indaziflam at 35, 52.5, and 70 g a.i. ha−1controlled this PR biotype 70 to 97%. This marks the second instance of annual bluegrass developing resistance to prodiamine in Tennessee during the past 5 yr. Future research should evaluate indaziflam efficacy for control of other prodiamine-resistant biotypes of annual bluegrass as well as annual bluegrass biotypes resistant to herbicidal inhibitors of 5-enolpyruvylshikimic acid-3-phosphate synthase, acetolactate synthase, and photosystem II.

Development of high level daptomycin resistance (HLDR) in Abiotrophia and Granulicatella spp isolates from patients with infective endocarditis (IE).

2021 ◽  
Author(s):  
María A. Cañas ◽  
Adrian Téllez ◽  
Cristina García de la Mària ◽  
Anders Dahl ◽  
Javier García-González ◽  
...  
Keyword(s):  
Infective Endocarditis ◽  
Combination Therapy ◽  
Minimal Inhibitory Concentration ◽  
Inhibitory Concentration ◽  
Therapeutic Option ◽  
Combination Therapies ◽  
Viridans Streptococci ◽  
High Level ◽  
Time Kill

Abiotrophia and Granulicatella species are fastidious organisms, representing around 1%–3% of infective endocarditis (IE). Little is known about the optimal antibiotic treatment of these species, and daptomycin has been suggested as a therapeutic option. We describe the antimicrobial profile in Abiotrophia and Granulicatella IE isolates, investigate high-level daptomycin resistance (HLDR) development and evaluate daptomycin activity in combination therapy. In vitro studies with 16 IE strains (6 A. defectiva , 9 G. adiacens and 1 G. elegans ) were performed using microdilution to determine minimal inhibitory concentration (MIC) and time-kill methodology to evaluate combination therapy. Daptomycin non-susceptibility (DNS; MIC≥ 2 mg/L) and HLDR (MIC≥256 mg/L) were based on existing Clinical and Laboratory Standards (CLSI) breakpoints for viridans streptococci. All isolates were susceptible to vancomycin: G. adiacens was more susceptible to penicillin and ampicillin than A. defectiva (22% vs. 0%, and 67% vs. 33%) but less susceptible to ceftriaxone and daptomycin (56% vs. 83%, and 11% vs. 50%). HLDR developed in both A. defectiva (33%) and G. adiacens (78%) after 24h exposure to daptomycin. Combination therapy did not prevent the development of daptomycin resistance with ampicillin (2/3 strains), gentamicin (2/3 strains), ceftriaxone (2/3 strains) or ceftaroline (2/3 strains). Once developed, HLDR was stable for a prolonged time (>3 weeks) in G. adiacens , whereas in A. defectiva the HLDR it reversed to baseline MIC at day 10. This study is first to demonstrate rapid HLDR development in Abiotrophia and Granulicatella species in vitro . Resistance was stable, and most combination therapies did not prevent it.

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