scholarly journals Impact of Azoxystrobin, Dimethomorph, Fluazinam, Fosetyl-Al, and Metalaxyl on Growth, Sporulation, and Zoospore Cyst Germination of Three Phytophthora spp.

Plant Disease ◽  
2000 ◽  
Vol 84 (4) ◽  
pp. 454-458 ◽  
Author(s):  
M. E. Matheron ◽  
M. Porchas
Keyword(s):  
Life Cycle ◽  
Disease Control ◽  
Mycelial Growth ◽  
Phytophthora Capsici ◽  
Effective Concentration ◽  
The Other ◽  
In Vitro Activity ◽  
Phytophthora Spp ◽  
Cyst Germination

In vitro activity of azoxystrobin, dimethomorph, and fluazinam on growth, sporulation, and zoospore cyst germination of Phytophthora capsici, P. citrophthora, and P. parasitica was compared to that of fosetyl-Al and metalaxyl. The 50% effective concentration (EC50) values for)inhibition of mycelial growth of the three pathogens usually were lowest for dimethomorph and (metalaxyl, ranging from <0.1 to 0.38 μg/ml. However, the 90% effective concentration (EC90) levels for dimethomorph always were lower than the other four tested compounds, with values ranging from 0.32 to 1.6 μg/ml. Mycelial growth of P. capsici, P. citrophthora, and P. parasitica was least affected by azoxystrobin and fluazinam, with estimated (EC90) values >3,000 μg/ml. Reduction of sporangium formation by P. capsici, P. citrophthora, and P. parasitica in the presence of dimethomorph at 1 μg/ml was significantly greater than that recorded for the same concentration of azoxystrobin, fluazinam, and fosetyl-Al. For the three species of Phytophthora, zoospore motility was most sensitive to fluazinam (EC50 and EC90 values of <0.001 μg/ml) and (least sensitive to fosetyl-Al, with (EC50 and EC90 values ranging from 299 to 334 and 518 to 680 μg/ml, respectively). Germination of encysted zoospores of P. capsici, P. citrophthora, and P. parasitica was most sensitive to dimethomorph (EC50 and EC90 values ranging from 3.3 to 7.2 and 5.6 to 21 μg/ml, respectively), intermediate in sensitivity to fluazinam (EC50 and EC90 from 18 to 108 and 67 to >1,000 μg/ml, respectively) and metalaxyl (EC50 and EC90 from 32 to 280 and 49 to 529 μg/ml, respectively), and lowest in sensitivity to azoxystrobin and fosetyl-Al (EC50 and EC90 from 256 to >1,000 μg/ml). The activity of azoxystrobin, dimethomorph, and fluazinam on one or more stages of the life cycle of P. capsici, P. citrophthora, and P. parasitica suggests that these compounds potentially could provide Phytophthora spp. disease control comparable to that of the established fungicides fosetyl-Al and metalaxyl.

scholarly journals Variations in the Sensitivity of Phytophthora infestans Isolates from Different Genetic Backgrounds to Dimethomorph

Plant Disease ◽  
2003 ◽  
Vol 87 (11) ◽  
pp. 1283-1289 ◽  
Author(s):  
J. M. Stein ◽  
W. W. Kirk
Keyword(s):  
Life Cycle ◽  
Phytophthora Infestans ◽  
Mycelial Growth ◽  
Hyphal Growth ◽  
Potato Leaf ◽  
Leaf Discs ◽  
Highly Sensitive ◽  
Significant Difference ◽  
Cyst Germination

The sensitivities of 11 isolates of Phytophthora infestans to dimethomorph were examined at all stages of the asexual life cycle and when inoculated onto potato leaf discs. In vitro zoospore encystment and cyst germination were highly sensitive to dimethomorph with 50% reduction of mycelial growth and cyst germination (EC50) values for most isolates <0.20 μg/ml, whereas direct sporangia germination and in vitro hyphal growth and sporulation were less sensitive (means of 0.45 and 0.22 μg/ml, respectively). Zoosporogenesis was not significantly inhibited at the maximum dimethomorph concentration examined, 10 μg/ml. Significant differences (Fisher's least significant difference, P = 0.05) in the EC50 values were present between isolates for all stages of the asexual life cycle, except direct sporangia germination and zoosporogenesis. Sensitivity ratios between the least- and most-sensitive isolates were 6.11, 12.14, 12.36, and 10.56 for hyphal growth, in vitro sporulation, zoospore encystment, and cyst germination, respectively. Application of dimethomorph at 1,000 μg/ml to potato leaf discs at 24 or 48 h before inoculation completely inhibited symptom incidence for most isolates, whereas application after inoculation generally was not significantly different from the untreated control, regardless of concentration. Sporulation from leaf discs treated with dimethomorph at 24 or 48 h after inoculation was completely inhibited for all isolates with dimethomorph at 1,000 μg/ml, even when symptom incidence was not significantly reduced.

scholarly journals In Vitro and In Vivo Antibacterial Activities of DW-224a, a New Fluoronaphthyridone

2006 ◽  
Vol 50 (6) ◽  
pp. 2261-2264 ◽  
Author(s):  
Hee-Soo Park ◽  
Hyun-Joo Kim ◽  
Min-Jung Seol ◽  
Dong-Rack Choi ◽  
Eung-Chil Choi ◽  
...  
Keyword(s):  
Antibacterial Activities ◽  
The Other ◽  
Vitro Activity ◽  
Gram Negative Bacteria ◽  
In Vitro Activity ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria

ABSTRACT DW-224a showed the most potent in vitro activity among the quinolone compounds tested against clinical isolates of gram-positive bacteria. Against gram-negative bacteria, DW-224a was slightly less active than the other fluoroquinolones. The in vivo activities of DW-224a against gram-positive bacteria were more potent than those of other quinolones.

scholarly journals In Vitro Activity of Newer and Conventional Antimicrobial Agents, Including Fosfomycin and Colistin, against Selected Gram-Negative Bacilli in Kuwait

Pathogens ◽  
2018 ◽  
Vol 7 (3) ◽  
pp. 75 ◽  
Author(s):  
Wadha Alfouzan ◽  
Rita Dhar ◽  
David Nicolau
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Antimicrobial Agents ◽  
The Other ◽  
In Vitro Activity ◽  
Limited Data ◽  
Gram Negative ◽  
E Coli ◽  
Microbroth Dilution

Limited data are available on susceptibilities of these organisms to some of the recently made accessible antimicrobial agents. The in vitro activities of newer antibiotics, such as, ceftolozane/tazobactam (C/T) and ceftazidime/avibactam (CZA) along with some “older” antibiotics, for example fosfomycin (FOS) and colistin (CL) were determined against selected strains (resistant to ≥ 3 antimicrobial agents) of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Minimum inhibitory concentrations (MIC) were determined by Clinical and Laboratory Standards Institute microbroth dilution. 133 isolates: 46 E. coli, 39 K. pneumoniae, and 48 P. aeruginosa were tested. Results showed that E. coli isolates with MIC50/90, 0.5/1 μ g / mL for CL; 4/32 μ g / mL for FOS; 0.25/32 μ g / mL for C/T; 0.25/8 μ g / mL for CZA, exhibited susceptibility rates of 95.7%, 97.8%, 76.1%, and 89.1%, respectively. On the other hand, K. pneumoniae strains with MIC50/90, 0.5/1 μ g / mL for CL; 256/512 μ g / mL for FOS; 2/128 μ g / mL for C/T; 0.5/128 μ g / mL for CZA showed susceptibility rates of 92.3%, 7.7%, 51.3%, and 64.1%, respectively. P. aeruginosa isolates with MIC50/90, 1/1 μ g / mL for CL; 128/128 μ g / mL for C/T; 32/64 μ g / mL for CZA presented susceptibility rates of 97.9%, 33.3%, and 39.6%, respectively. Higher MICs were demonstrated against most of the antibiotics. However, CL retained efficacy at low MICs against most of the isolates tested.

VARIABILITY IN SENSITIVITY TO THE FUNGICIDE PYROXYCHLOR WITHIN THE GENERA PHYTOPHTHORA AND PYTHIUM

1976 ◽  
Vol 56 (2) ◽  
pp. 365-369 ◽  
Author(s):  
LLOYD T. RICHARDSON
Keyword(s):  
Mycelial Growth ◽  
The Other ◽  
Individual Species ◽  
Systemic Fungicide ◽  
Damping Off ◽  
Response Curves ◽  
In Vitro Sensitivity ◽  
Pea Seedlings ◽  
Growth Room

A comparative study was made of the innate sensitivity of individual species within the genera Phytophthora and Pythium to the selective systemic fungicide pyroxychlor (2-chloro-6-methoxy-4-(Trichloromethyl)pyridine). In vitro sensitivity was evaluated on the basis of inhibition of mycelial growth on treated V8-juice agar. Little variation was found among the 10 Phytophtora spp. tested, the dosage response curves being linear and generally steep, with ED50 values ranging from 0.4 to 6.2 ppm. Similar steep, linear curves with low ED50 values were obtained with six Pythium spp., but five other species responded quite differently. P. sylvaticum was the most tolerant with no inhibition up to 25 ppm and only 20% at 100 ppm. The dosage response of the other species was irregular. Inhibition of P. irregulare and P. splendens reached a maximum of 50% near 1 ppm. The curve for P. ultimum also reached a maximum near 1 pp, but declined to a lower, constant level. The curve for P. polymastum was distinctly bimodal, ascending with dosage up to 0.5 ppm, descending sharply to 3.1 ppm, then ascending again. The effectiveness of pyroxychlor in controlling preemergence damping-off of pea seedlings caused by four of the Pythium spp. was compared in a growth-room test. P. aphanidermatum and P. ultimum were effectively controlled by postplant drench treatments, but P. irregulare and P. sylvaticum were not.

Comprehensive Analysis Of The In Vitro Potency Of Ponatinib, and All Other Approved BCR-ABL Tyrosine Kinase Inhibitors (TKIs), Against a Panel Of Single and Compound BCR-ABL Mutants

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3992-3992 ◽  
Author(s):  
Joseph M Gozgit ◽  
Alexa Schrock ◽  
Tzu-Hsiu Chen ◽  
Tim Clackson ◽  
Victor M. Rivera
Keyword(s):  
Steady State ◽  
Plasma Concentration ◽  
Effective Concentration ◽  
The Other ◽  
Single Mutation ◽  
Employment Equity ◽  
Clinical Resistance ◽  
Equity Ownership ◽  
Effective Plasma Concentration

Abstract Background Secondary mutations in BCR-ABL are the most common cause of resistance to TKIs in patients (pts) with chronic myeloid leukemia (CML). Ponatinib is a potent pan-BCR-ABL TKI that has been shown to suppress the emergence of any single mutation in vitro, including T315I, at clinically achievable concentrations (40 nM), though higher concentrations were required to suppress emergence of certain compound mutations (2 mutations in the same BCR-ABL allele). Ponatinib has demonstrated significant clinical activity in pts in the phase 2 PACE trial, 60% of whom received 3 or more prior TKIs. Responses were observed for each of the 15 mutations present in >1 chronic phase CML pt at baseline, and no single mutation conferring resistance to ponatinib has emerged to date, though in some cases development of compound mutations has been observed. To gain a more precise understanding of the effects of specific mutations on the clinical efficacy of ponatinib, IC50s for ponatinib, and all other approved TKIs, against 31 single or compound BCR-ABL mutants were determined. To explore the relationship between in vitro potency and clinical efficacy, IC50s were related to “effective” TKI levels achieved in patients. Methods TKI potency was assessed in engineered Ba/F3 cells by measuring cell viability at 72 hours. The effective plasma concentration for each TKI was calculated from published average steady-state concentration values for the recommended dose, and adjusted for the functional effects of protein binding. These effects were assessed by determining the degree to which TKI potency was reduced by the presence of physiological concentrations of human serum albumin (HSA) and alpha 1-acid glycoprotein (AAG). Results The activity of ponatinib, and 5 other TKIs, against 21 single BCR-ABL mutants is shown in Figure A. Ponatinib potently inhibited viability of native BCR-ABL and all mutants, including T315I (IC50s (nM): 3-16). The IC50s for the other TKIs, excluding T315I (>4000 for all) ranged from: 201-10,000 (imatinib), 12-784 (nilotinib), 2-104 (dasatinib), 40-1,280 (bosutinib) and 18-5,216 (radotinib). IC50 values were compared to the effective plasma concentration for each TKI (Figure A). Mutants that have previously been associated with clinical resistance to a particular TKI tended to have IC50s that approached or substantially exceeded the effective concentration for that TKI, including most mutants for imatinib, E255K/V, Y253H, L248R, T315I for nilotinib, and V299L, F317C/I/V, T315A/I for dasatinib. The most problematic mutants for bosutinib predicted by this analysis were F317V, L248R, V299L, and T315I. Notably, all mutant IC50s fell below the effective concentration for ponatinib. The activity of all TKIs against 10 clinically-observed BCR-ABL compound mutants was also assessed. Four compound mutants had IC50s near or above the effective concentration for ponatinib (T315I+M351T, E255V+F317I, T315I+E255K, T315I+E255V) (Figure B). All 4, plus others, are also predicted to be problematic for the other TKIs. Conclusions Relating in vitro TKI potency to “effective” steady-state plasma concentrations in patients identified mutations known to confer clinical resistance to imatinib, nilotinib and dasatinib. This method of analysis suggests that ponatinib may be able to inhibit all single BCR-ABL mutants, but not all compound mutants, a prediction that is thus far consistent with results observed in patients. Compound mutations that are predicted to confer resistance to ponatinib are also predicted to confer resistance to all other approved TKIs. Early introduction of ponatinib may prevent the emergence of single mutations, and thus the sequential development of compound mutations. Disclosures: Gozgit: ARIAD: Employment, Equity Ownership. Schrock:ARIAD: Employment, Equity Ownership. Chen:ARIAD: Employment, Equity Ownership. Clackson:ARIAD: employees of and own stock/stock options in ARIAD Pharmaceuticals, Inc Other, Employment. Rivera:ARIAD: Employment.

scholarly journals Baseline Sensitivity and Control Efficacy of Tetramycin Against Phytophthora capsici Isolates in China

Plant Disease ◽  
2018 ◽  
Vol 102 (5) ◽  
pp. 863-868 ◽  
Author(s):  
Dicheng Ma ◽  
Jiamei Zhu ◽  
Leiming He ◽  
Kaidi Cui ◽  
Wei Mu ◽  
...  
Keyword(s):  
Mycelial Growth ◽  
Southern China ◽  
Phytophthora Capsici ◽  
Environmental Safety ◽  
Phytophthora Blight ◽  
Baseline Sensitivity ◽  
Control Efficacy ◽  
Mean Values ◽  
Greenhouse Experiments

Tetramycin is a new biopesticide that combines high-level and broad-spectrum fungicidal activity, low toxicity, and environmental safety. In this study, 90 Phytophthora capsici isolates obtained from various regions in southern China were characterized for their baseline sensitivity to tetramycin. The protective and curative activities of tetramycin against P. capsici were determined on leaves of pepper, and the control efficacy of tetramycin in greenhouse experiments was also determined. Compared with mycelial growth, the formation of sporangia and the discharge of zoospores were inhibited by lower concentrations of tetramycin, approximately 5 µg ml−1 on V8 media. The frequency distribution curves for the tetramycin sensitivity were unimodal, with mean values for the fungicide concentration that reduced mycelial growth, sporangia formation, and zoospore discharge by 50% compared with the control of 1.18 ± 0.91, 0.64 ± 0.42, and 0.63 ± 0.30 µg ml−1, respectively. In addition, no correlation was observed between tetramycin and other fungicides tested, including mandipropamid, azoxystrobin, mefenoxam, fluazinam, fluopicolide, and famoxadone. Tetramycin exhibited both protective and curative effects against P. capsici in vitro, and its protective activity was better than its curative activity. In greenhouse experiments, tetramycin concentration of 60 and 90 µg ml−1 provided a protective control efficacy of 47.1 to 56.4% and curative efficacy of 43.3 to 52.7%. These results demonstrated that tetramycin could serve as an excellent alternative fungicide to control Phytophthora blight of pepper.

scholarly journals Inhibition of Pythium spp. and Suppression of Pythium Blight of Turfgrasses with Phosphonate Fungicides

Plant Disease ◽  
2009 ◽  
Vol 93 (8) ◽  
pp. 809-814 ◽  
Author(s):  
Phillip J. Cook ◽  
Peter J. Landschoot ◽  
Maxim J. Schlossberg
Keyword(s):  
Perennial Ryegrass ◽  
Active Ingredient ◽  
Mycelial Growth ◽  
Phosphorous Acid ◽  
Creeping Bentgrass ◽  
The United States ◽  
Effective Concentration ◽  
Significant Suppression ◽  
Inhibitory Effects

Pythium aphanidermatum and other Pythium spp. cause Pythium blight of turfgrasses in the United States. Phosphonate fungicides suppress Pythium blight when applied preventatively, but efficacy may vary with product, rate and timing of application, and host species. The objectives of this study were to assess the inhibitory effects of phosphorous acid on Pythium spp. in vitro, and determine if active ingredient and formulation of phosphonate fungicides provide similar levels of Pythium blight suppression on perennial ryegrass and creeping bentgrass when applied at equivalent rates of phosphorous acid. Phosphorous acid EC50 values (effective concentration that reduces mycelial growth by 50%) for P. aphanidermatum isolates ranged from 35.6 to 171.8 μg/ml. EC50 values for isolates of six other Pythium spp. were between 38.7 and 220.8 μg/ml. In 2004 and 2005, all phosphonate treatments provided significant suppression of Pythium blight symptoms on creeping bentgrass and perennial ryegrass relative to the untreated control. No differences in percentage of blighted turf occurred among phosphonate treatments when applied at equivalent rates of phosphorous acid in either year of the study, regardless of active ingredient, formulation, or turfgrass species.

scholarly journals In Vitro Activity of DC-159a, a New Broad-Spectrum Fluoroquinolone, Compared with That of Other Agents against Drug-Susceptible and -Resistant Pneumococci

2007 ◽  
Vol 52 (1) ◽  
pp. 77-84 ◽  
Author(s):  
Catherine Clark ◽  
Kathy Smith ◽  
Lois Ednie ◽  
Tatiana Bogdanovich ◽  
Bonifacio Dewasse ◽  
...  
Keyword(s):  
Broad Spectrum ◽  
The Other ◽  
Quinolone Resistance ◽  
Vitro Activity ◽  
In Vitro Activity ◽  
Resistance Selection ◽  
Resistant Strains

ABSTRACT DC-159a yielded MICs of ≤1 μg/ml against 316 strains of both quinolone-susceptible and -resistant pneumococci (resistance was defined as a levofloxacin MIC ≥4 μg/ml). Although the MICs for DC-159a against quinolone-susceptible pneumococci were a few dilutions higher than those of gemifloxacin, the MICs of these two compounds against 28 quinolone-resistant pneumococci were identical. The DC-159a MICs against quinolone-resistant strains did not appear to depend on the number or the type of mutations in the quinolone resistance-determining region. DC-159a, as well as the other quinolones tested, was bactericidal after 24 h at 2× MIC against 11 of 12 strains tested. Two of the strains were additionally tested at 1 and 2 h, and DC-159a at 4× MIC showed significant killing as early as 2 h. Multistep resistance selection studies showed that even after 50 consecutive subcultures of 10 strains in the presence of sub-MICs, DC-159a produced only two mutants with maximum MICs of 1 μg/ml.

scholarly journals Suppression of Fusarium moniliforme in Rice by Rice-Associated Antagonistic Bacteria

Plant Disease ◽  
1997 ◽  
Vol 81 (1) ◽  
pp. 49-52 ◽  
Author(s):  
A. M. Rosales ◽  
T. W. Mew
Keyword(s):  
Seed Germination ◽  
Fusarium Moniliforme ◽  
Mycelial Growth ◽  
Field Trials ◽  
The Philippines ◽  
The Other ◽  
Antagonistic Bacteria ◽  
Seedling Vigor ◽  
Bacterial Strains

The potential of antagonistic bacteria from paddy water, rhizosphere soils, sclerotia, and rice plants to control “bakanae” caused by Fusarium moniliforme was assessed. Experiments were conducted to determine the in vitro antibiosis and effect of bacteria on seed germination. Out of 441 isolates, 113 were inhibitory to mycelial growth of the pathogen. Bacterial strains were classified into three groups based on effect on seed germination: (i) those that promoted germination and enhanced seedling vigor; (ii) those that had no effect on germination; and (iii) those that were deleterious and inhibited germination. Bacterization of naturally infected seeds reduced bakanae incidence in seedbox and seedbed tests. In a seedbed experiment with IR 58 seeds soaked in suspensions of bacterial strains, bakanae incidence and disease control ranged from 0.9 to 6.8% and 71.7 to 96.3%, respectively. From the 3 years of field trials, 10 strains reduced bakanae. Five strains consistently reduced bakanae, but the other five exhibited variable effects among trials. Specificity of suppression by antagonistic bacteria against different pathogenic isolates of F. moniliforme from various locations in the Philippines was observed.

scholarly journals Baseline Sensitivities of New Fungicides and Their Toxicity to Selected Life Stages of Phytophthora Species from Citrus in California

Plant Disease ◽  
2018 ◽  
Vol 102 (4) ◽  
pp. 734-742 ◽  
Author(s):  
Morgan A. Gray ◽  
Wei Hao ◽  
Helga Förster ◽  
James E. Adaskaveg
Keyword(s):  
Phytophthora Species ◽  
Effective Concentration ◽  
Life Stages ◽  
Phytophthora Citrophthora ◽  
Mean Values ◽  
Chemical Treatments ◽  
Phytophthora Spp ◽  
Chlamydospore Formation ◽  
Oospore Formation

Phytophthora citrophthora, P. syringae, P. nicotianae, and P. hibernalis are important pathogens of citrus in California but few chemical treatments are currently available. In vitro toxicities of four new fungicides to isolates of Phytophthora spp. from California were determined. Mean effective concentration values to inhibit mycelial growth by 50% for ethaboxam, fluopicolide, mandipropamid, oxathiapiprolin, and mefenoxam were 0.068, 0.04, 0.004, 0.0003, and 0.039 µg/ml, respectively, for 62 isolates of P. citrophthora; 0.005, 0.045, 0.003, 0.0001, and 0.008 µg/ml, respectively, for 71 isolates of P. syringae; 0.016, 0.057, 0.005, 0.0005, and 0.183 µg/ml, respectively, for 31 isolates of P. nicotianae; and 0.030, 0.018, 0.005, <0.0003, and ≤0.001 µg/ml, respectively, for two isolates of P. hibernalis. Mean values for ≥90% inhibition of sporangia formation of four isolates of P. citrophthora were 0.1, 0.28, 0.026, 0.005, and 55 µg/ml for ethaboxam, fluopicolide, mandipropamid, oxathiapiprolin, and mefenoxam, respectively. Zoospore cyst germination of P. citrophthora was most inhibited by oxathiapiprolin and mandipropamid. Chlamydospore formation of P. nicotianae was most sensitive to oxathiapiprolin, with a mean ≥90% reduction (EC>90) of 0.002 µg/ml, moderately sensitive to mandipropamid (EC>90 = 0.2 µg/ml) and mefenoxam (EC>90 = 0.6 µg/ml), and least sensitive to ethaboxam and fluopicolide (EC>90 = 1 µg/ml). Oospore formation of P. nicotianae was inhibited by ≥90% using oxathiapiprolin at 0.0004 µg/ml, mandipropamid at 0.02 µg/ml, ethaboxam at 0.1 µg/ml, or fluopicolide at 0.4 µg/ml, whereas 62% inhibition was obtained by mefenoxam at 40 µg/ml.

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