scholarly journals Resistance of Kansas Sclerotinia homoeocarpa Isolates to Thiophanate-Methyl and Determination of Associated β-Tubulin Mutation

2014 ◽  
Vol 15 (2) ◽  
pp. 80-84 ◽  
Author(s):  
Jesse C. Ostrander ◽  
Richard B. Todd ◽  
Megan M. Kennelly
Keyword(s):  
Golf Course ◽  
Sclerotinia Homoeocarpa ◽  
Fungicide Sensitivity ◽  
Putting Greens ◽  
Thiophanate Methyl ◽  
In Vitro Sensitivity ◽  
Starting Point ◽  
Β Tubulin

Eighty-two isolates of Sclerotinia homoeocarpa from 12 sites in Kansas were evaluated for in vitro sensitivity to the methyl benzimidazole carbamate (MBC) fungicide thiophanate-methyl at the discriminatory dose of 10 μg/ml. Seventeen isolates were sensitive to thiophanate-methyl and the remaining isolates were resistant. Of the 65 isolates from golf course putting greens, two isolates were sensitive and the remaining 63 isolates were resistant. Six resistant and five sensitive isolates were also evaluated in greenhouse assays on fungicide-treated plants. The isolates that were sensitive to thiophanate-methyl in vitro did not cause any disease on thiophanate-methyl-treated plants, and those that were resistant in vitro caused blighting on treated plants equivalent to the nontreated controls. The entire β-tubulin gene was sequenced for four resistant and four sensitive isolates. The resistant isolates all harbored a substitution of alanine for glutamic acid at codon 198 (E198A). These results provide a starting point for further surveys and monitoring of fungicide sensitivity. Accepted 7 April 2014. Published 6 June 2014.

scholarly journals Thiophanate-Methyl and Propiconazole Sensitivity in Sclerotinia homoeocarpa Populations from Golf Courses in Wisconsin and Massachusetts

Plant Disease ◽  
2009 ◽  
Vol 93 (1) ◽  
pp. 100-105 ◽  
Author(s):  
Paul L. Koch ◽  
Craig R. Grau ◽  
Young-Ki Jo ◽  
Geunhwa Jung
Keyword(s):  
Golf Course ◽  
Golf Courses ◽  
Sclerotinia Homoeocarpa ◽  
Putting Greens ◽  
Thiophanate Methyl ◽  
Development Of Resistance ◽  
History Of ◽  
Intensively Managed ◽  
Pathogen Populations

Management of dollar spot, caused by the fungus Sclerotinia homoeocarpa, is dependent upon repeated fungicide applications in intensively managed turfgrass such as golf course putting greens and fairways. Repeated fungicide applications could potentially select for fungicide-resistant isolates and result in a reduction of disease control. The objectives of this study were to determine the degree of S. homoeocarpa in vitro sensitivity to the fungicides thiophanate-methyl and propiconazole using isolates collected from golf course putting greens, fairways, and roughs; and to determine the relationships of golf course age and fungicide history to the frequency of fungicide-insensitive isolates within the population. More than 1,400 S. homoeocarpa isolates were collected from putting greens, fairways, and roughs at six Wisconsin golf courses and one Massachusetts golf course and subjected to in vitro fungicide sensitivity assays with single discriminatory concentrations of thiophanate-methyl and propiconazole. Five of seven pathogen populations from rough areas were not significantly different from one another in propiconazole sensitivity. These populations were collectively the most sensitive to both fungicides and therefore, served as baseline populations for comparison with fungicide-exposed populations from putting greens and fairways. Greater propiconazole insensitivity was observed in populations collected from fairways and putting greens that received more frequent applications of the fungicide than those isolated from the roughs. In nearly all the golf courses, the frequency of thiophanate-methyl insensitivity was higher among isolates of S. homoeocarpa collected from fairways than from roughs regardless of the age of the golf course or history of benzimidazole use. Thus, while the development of resistance to propiconazole can be predicted in part by the relative frequency of demethylation inhibitor fungicide applications, the occurrence of populations resistant to thiophanate-methyl appears to be unrelated to recent use of the benzimidazole class of fungicides.

scholarly journals Geographic Distribution of Fungicide-Insensitive Sclerotinia homoeocarpa Isolates from Golf Courses in the Northeastern United States

Plant Disease ◽  
2010 ◽  
Vol 94 (2) ◽  
pp. 186-195 ◽  
Author(s):  
Alexander I. Putman ◽  
Geunhwa Jung ◽  
John E. Kaminski
Keyword(s):  
United States ◽  
Resistance Mechanisms ◽  
Golf Courses ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Northeastern United States ◽  
Fungicide Sensitivity ◽  
Putting Greens ◽  
Thiophanate Methyl

Chemical management of dollar spot in turf may lead to the development of Sclerotinia homoeocarpa populations with reduced fungicide sensitivity. The objective of this study was to determine the scope of S. homoeocarpa insensitivity to fungicides commonly used to control dollar spot on golf courses in the northeastern United States. A total of 965 and 387 isolates of S. homoeocarpa from intensively or individually sampled sites, respectively, were evaluated for in vitro sensitivity to iprodione, propiconazole, and thiophanate-methyl. Mean baseline sensitivities to iprodione and propiconazole were 0.2763 and 0.0016 μg a.i. ml–1, respectively, and all baseline isolates were sensitive to thiophanate-methyl at 1,000 μg a.i. ml–1. When compared with the baseline population, 14 and 18 of 20 total populations were less sensitive to iprodione and propiconazole, respectively. Individually sampled isolates obtained from fairways, putting greens, or tees were less sensitive to iprodione and propiconazole when compared with the baseline. For thiophanate-methyl, five populations were sensitive, six were resistant, and the remaining nine populations contained various proportions (2 to 92%) of resistant isolates. Individually sampled isolates obtained from fairways and putting greens were evaluated for associations in sensitivity among the three fungicides. A weak but positive correlation in sensitivity to iprodione and propiconazole was observed for isolates resistant to thiophanate-methyl but correlations for sensitive isolates were not significant. Furthermore, isolates with highly reduced sensitivity to iprodione clustered in a narrow range of propiconazole sensitivity. These data suggest the possible existence of resistance mechanisms common to diverse fungicide classes. Overall, results indicate that insensitivity of S. homoeocarpa to iprodione, propiconazole, and thiophanate-methyl exists in varying degrees on golf courses in the northeastern United States.

scholarly journals Fungicide Sensitivity of Sclerotinia homoeocarpa from Golf Courses in Ohio

Plant Disease ◽  
2006 ◽  
Vol 90 (6) ◽  
pp. 807-813 ◽  
Author(s):  
Young-Ki Jo ◽  
Amy L. Niver ◽  
Joseph W. Rimelspach ◽  
Michael J. Boehm
Keyword(s):  
Field Trials ◽  
In Vitro Assays ◽  
Golf Courses ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Fungicide Sensitivity ◽  
Thiophanate Methyl ◽  
Field Efficacy ◽  
Fungicide Insensitivity

Managing dollar spot, the most common and chronic disease on intensively cultivated turfgrass, relies on the judicious use of fungicides. The heavy use of fungicides has led to the development of isolates of Sclerotinia homoeocarpa insensitive to several classes of fungicides, including benzimidazoles, demethylation-inhibitors, and dicarboximides. In vitro fungicide sensitivity assays using single discriminatory concentrations of thiophanate-methyl, propiconazole, and iprodione were developed in this study for evaluating field efficacy of these fungicides and the prevalence of fungicide insensitivity within S. homoeocarpa isolated from golf courses throughout Ohio. Discriminatory concentrations for these fungicides were determined to be: thiophanate-methyl = 1,000 μg a.i. ml-1, propiconazole = 0.1 μg a.i. ml-1, and iprodione = 1.0 μg a.i. ml-1. Effective concentration that produces 50% inhibition (EC50) was estimated based on relative mycelial growth of S. homoeocarpa on potato dextrose agar (PDA) versus PDA amended with the discriminatory concentration of each fungicide. Field trials conducted at 3 locations in 2002 and 10 locations in 2003 revealed that the in vitro assays accurately predicted field efficacy for thiophanate-methyl. When used to screen 192 S. homoeocarpa isolates collected previously from 55 golf courses throughout Ohio, the in vitro assays revealed that 34 of the golf courses sampled had S. homoeocarpa resistant to thiophanate-methyl. S. homoeocarpa with reduced in vitro sensitivities was isolated from 18 and 1 golf courses for propiconazole and iprodione, respectively.

scholarly journals In Vitro Fungicide-Insensitive Profiles of Sclerotinia homoeocarpa Populations from Pennsylvania and the Surrounding Region

Plant Disease ◽  
2019 ◽  
Vol 103 (2) ◽  
pp. 214-222 ◽  
Author(s):  
Cameron M. Stephens ◽  
John Kaminski
Keyword(s):  
Active Ingredient ◽  
Golf Course ◽  
Golf Courses ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Thiophanate Methyl ◽  
Surrounding Areas ◽  
Fungicide Insensitivity ◽  
Research Facilities

Repeated fungicide applications are typically required to provide adequate control of dollar spot on golf courses and may shift Sclerotinia homoeocarpa populations from sensitive to insensitive or resistant to an active ingredient. The objective of this study was to characterize the geographic distribution of fungicide-insensitive, fungicide-resistant, and multiple fungicide insensitive (MFI) S. homoeocarpa populations on golf courses in Pennsylvania and the surrounding region. S. homoeocarpa isolates (n = 681) were collected from 45 different golf courses or research facilities. Each isolate was evaluated in vitro against propiconazole, iprodione, boscalid, and thiophanate-methyl using discriminatory concentrations of 0.1, 1.0, 1,000, and 1,000 µg of active ingredient per milliliter of PDA, respectively. Relative mycelial growth (RMG) values were used to determine sensitivity or insensitivity based on comparison with a baseline population. Of the 681 isolates evaluated, 81, 80, and 85% exhibited reduced sensitivity to boscalid, iprodione, and propiconazole, respectively. A total of 41% of the isolates were resistant to thiophanate-methyl. Based on mean RMG of all isolates from each golf course, 16, 35, and 37 of the 45 golf courses exhibited reduced sensitivity to boscalid, iprodione, and propiconazole, respectively. A total of 585 isolates (86%) exhibited an MFI profile in which they were insensitive or resistant to at least two fungicides evaluated. Isolates with reduced sensitivity to boscalid, iprodione, and propiconazole, but sensitive to thiophanate-methyl, were the most common phenotype within the three-MFI profile. Fungicide insensitivity and resistance to commonly used fungicides, as well as MFI profiles, were prevalent in Pennsylvania and the surrounding areas and may cause management challenges.

scholarly journals Control of Dollar Spot of Creeping Bentgrass Caused by an Isolate of Sclerotinia homoeocarpa Resistant to Benzimidazole and Demethylation-Inhibitor Fungicides

Plant Disease ◽  
1997 ◽  
Vol 81 (11) ◽  
pp. 1259-1263 ◽  
Author(s):  
L. L. Burpee
Keyword(s):  
Incubation Period ◽  
Field Tests ◽  
Creeping Bentgrass ◽  
Disease Suppression ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Fungicide Sensitivity ◽  
Thiophanate Methyl ◽  
Demethylation Inhibitor

The effects of fungicides were studied on two isolates of Sclerotinia homoeocarpa that differed in fungicide sensitivity. Concentrations of benzimidazole (benomyl and thiophanate-methyl), demethylation inhibitor (fenarimol, propiconazole, and triadimefon), and nitrile (chlorothalonil) fungicides required to inhibit mycelial growth in vitro by 50 and 90% (effective concentration; EC50,90) were significantly greater for isolate S088 than for isolate S084. No differences were observed in the EC50,90 values of a pyridylaniline (fluazinam) or dicarboximide (iprodione) fungicide. In field tests conducted on creeping bentgrass, S088 had a significantly shorter incubation period than S084 in plots treated with propiconazole applied at 0.2 or 0.8 kg a.i. ha-1 in 1994 or 0.4 kg a.i. ha-1 in 1995, thiophanate-methyl applied at 1.5 or 3.0 kg a.i. ha-1 in 1994 and 1995, or a tank-mix of propiconazole and iprodione applied at 1.6 + 0.8 kg a.i. ha-1 in 1994. No differences in incubation periods occurred in plots treated with chlorothalonil or iprodione in either year, or with fluazinam in 1995 and 1996. Fewer days were required to reach 5% disease severity in turf inoculated with isolate S088, compared to isolate S084, in plots treated with propiconazole, thiophanate-methyl, or certain tank-mixes containing propiconazole, in 1994 and 1995. Several treatments, including propiconazole, thiophanate-methyl, and fluazinam, resulted in suppression of disease caused by isolate S084 to less than 5% severity for more than 21 days, while only fluazinam applied at 1.6 or 3.2 kg a.i. ha-1 provided more than 21 days of disease suppression in turf inoculated with either of the isolates tested. Slope coefficients from linear regressions between incubation period or days to 5% disease and concentrations of fungicide applied in 1996 were significantly different for isolate S084 compared to isolate S088 in plots treated with propiconazole, but not in plots treated with fluazinam.

scholarly journals Reduction in the in vitro sensitivity oF Drechslera tritici-repentis, isolated from wheat, to strobilurin and triazole fungicides

2017 ◽  
Vol 43 (1) ◽  
pp. 20-25
Author(s):  
Rosane Baldiga Tonin ◽  
Erlei Melo Reis ◽  
Aveline Avozani
Keyword(s):  
Inhibitory Concentration ◽  
In Vitro Sensitivity ◽  
Randomized Design ◽  
Inhibition Data ◽  
Ic50 Values ◽  
Control Failure ◽  
Quinone Outside Inhibitors ◽  
Completely Randomized Design

ABSTRACT Reports of failure in the chemical control of wheat yellow leaf spot led to determination of the sensitivity of Drechslera tritici-repentis (Dtr) to the fungicides quinone outside inhibitors (QoIs) and demethylation inhibitors (DMIs). The IC50 was obtained for strobilurins (azoxystrobin, kresoxim-methyl, picoxystrobin and pyraclostrobin) and for triazoles (cyproconazole, epoxiconazole, propiconazole, prothioconazole and tebuconazole), using five Dtr isolates. Seven concentrations of the fungicides were tested in the bioassay: 0.00; 0.01; 0.10; 1.00; 10:00 and 20.00 and 40.00 mg/L active ingredient (a.i.). Assays consisted of completely randomized design and four replicates. Each experiment was performed twice, using the average of the two tests for statistical analysis. The percentage inhibition data for conidial germination (QoIs) and for mycelial growth (DMIs) were subjected to logarithmic regression analysis, calculating the 50% inhibitory concentration (IC50) based on the generated equation. There was a reduction in the sensitivity of Dtr isolates to strobilurins. IC50 values ranged from 0.58 to > 40.00 mg/L. The lowest sensitivity of isolates was detected for azoxystrobin, kresoxim-methyl, picoxystrobin and trifloxystrobin. Pyraclostrobin was most efficient, showing IC50 between 0.58 and 1.03 mg/L. The IC50 ranged from 0.35 to 1.37 mg/L for epoxiconazole, from 0.49 to 1.28 mg/L for propiconazole and from 1.41 to 2.34 mg/L for tebuconazole. Prothioconazole was most potent, showing IC50 between 0.09 and 0.21 mg/L. The hypothesis that the control failure can be attributed to the reduced Dtr sensitivity to the fungicides QoIs and DMIs was confirmed.

scholarly journals Gatorbulin-1, a distinct cyclodepsipeptide chemotype, targets a seventh tubulin pharmacological site

2021 ◽  
Vol 118 (9) ◽  
pp. e2021847118
Author(s):  
Susan Matthew ◽  
Qi-Yin Chen ◽  
Ranjala Ratnayake ◽  
Charles S. Fermaintt ◽  
Daniel Lucena-Agell ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Wide Spectrum ◽  
Targeted Chemotherapy ◽  
Structural Determination ◽  
Marine Cyanobacterium ◽  
Microtubule Stabilization ◽  
Biochemical Studies ◽  
Β Tubulin

Tubulin-targeted chemotherapy has proven to be a successful and wide spectrum strategy against solid and liquid malignancies. Therefore, new ways to modulate this essential protein could lead to new antitumoral pharmacological approaches. Currently known tubulin agents bind to six distinct sites at α/β-tubulin either promoting microtubule stabilization or depolymerization. We have discovered a seventh binding site at the tubulin intradimer interface where a novel microtubule-destabilizing cyclodepsipeptide, termed gatorbulin-1 (GB1), binds. GB1 has a unique chemotype produced by a marine cyanobacterium. We have elucidated this dual, chemical and mechanistic, novelty through multidimensional characterization, starting with bioactivity-guided natural product isolation and multinuclei NMR-based structure determination, revealing the modified pentapeptide with a functionally critical hydroxamate group; and validation by total synthesis. We have investigated the pharmacology using isogenic cancer cell screening, cellular profiling, and complementary phenotypic assays, and unveiled the underlying molecular mechanism by in vitro biochemical studies and high-resolution structural determination of the α/β-tubulin−GB1 complex.

scholarly journals Relationship Between Fungicide Sensitivity and Control of Gummy Stem Blight of Watermelon Under Field Conditions

Plant Disease ◽  
2012 ◽  
Vol 96 (12) ◽  
pp. 1780-1784 ◽  
Author(s):  
A. Thomas ◽  
D. B. Langston ◽  
H. F. Sanders ◽  
K. L. Stevenson
Keyword(s):  
Fungicide Resistance ◽  
Field Experiments ◽  
In Vitro Assays ◽  
Didymella Bryoniae ◽  
Fungicide Sensitivity ◽  
Thiophanate Methyl ◽  
Stem Blight ◽  
Gummy Stem Blight ◽  
And Control

Gummy stem blight (GSB), caused by the fungus Didymella bryoniae, is the most destructive disease of watermelon and is managed primarily with fungicides. D. bryoniae has developed resistance to many fungicides that were once very effective, including azoxystrobin, boscalid, and thiophanate-methyl. Field experiments were conducted in Tifton (TN) and Reidsville (RV), GA in 2009 and 2010 to establish a relationship between frequency of resistance to a fungicide based on in vitro assays and its efficacy in the management of GSB. Frequency of resistance to boscalid, thiophanate-methyl, and azoxystrobin was >0.80 in isolates collected from nontreated plots in both locations and years. All isolates collected after six applications of boscalid, thiophanate-methyl, or azoxystrobin were resistant to the respective fungicide. All isolates collected from treated and nontreated plots were sensitive to tebuconazole and difenoconazole. GSB severity was assessed on a weekly basis from 63 days after planting. GSB severity in plots treated with boscalid, thiophanate-methyl, or azoxystrobin was not significantly different from that in the nontreated plots (39%, TN-2009; 45%, TN-2010; and 16%, RV-2010). GSB severity in tebuconazole-treated plots (27%, TN-2009; 14%, TN-2010; and 4%, RV-2010) was significantly lower than all other treatments and the nontreated control. There was a consistent negative association between frequency of fungicide resistance and disease control in the field. Thus, knowledge of the frequency of fungicide resistance in the pathogen population will be helpful in selecting the most effective fungicides for the management of GSB in watermelon fields.

scholarly journals Occurrence and Distribution of QoI-Resistant Isolates of Colletotrichum cereale from Annual Bluegrass in California

Plant Disease ◽  
2007 ◽  
Vol 91 (12) ◽  
pp. 1536-1546 ◽  
Author(s):  
Francis P. Wong ◽  
Sharon L. Midland ◽  
Karla A. de la Cerda
Keyword(s):  
Golf Course ◽  
Golf Courses ◽  
Colletotrichum Graminicola ◽  
Putting Greens ◽  
Qoi Fungicides ◽  
Mitochondrial Cytochrome B ◽  
Colletotrichum Cereale ◽  
Important Disease ◽  
Qoi Resistance

Turfgrass anthracnose, caused by Colletotrichum cereale (ex. Colletotrichum graminicola), is an important disease of turf used on golf course putting greens. Recent management of the disease has become increasingly difficult, partly due to the possible development of practical resistance to the QoI fungicides. In all, 558 single-conidia isolates of C. cereale were collected from 10 California golf courses, 8 of which had been exposed to QoI fungicides and 2 where no fungicides had been used. Isolates were tested using a mycelial expansion assay on azoxystrobinamended media. For the two nonexposed populations, in vitro 50% effective dose (ED50) values ranged from 0.0060 to 0.089 μg/ml. All isolates from the exposed populations could not be fully inhibited by doses of azoxystrobin as high as 8.0 μg/ml. A subset of these isolates were tested in vitro with the QoI fungicides pyraclostrobin and trifloxystrobin and found to be similar in response, indicating that these isolates were fully cross-resistant to all three fungicides. In greenhouse pot experiments, three isolates nonresponsive to QoI fungicides in vitro were not controlled by label rates of the fungicides. Spore germination assays also were examined; for 10 isolates identified as sensitive by mycelial expansion assays, ED50 values for axoystrobin ranged from 0.0040 to 0.0047 μg/ml; for 25 isolates identified as QoI-resistant, 93 to 100% of the conidia germinated at azoxystrobin concentrations as high as 8.0 μg/ml relative to the nonamended check treatments. Mitochondrial cytochrome b genes from a subset of 15 isolates (12 resistant and 3 sensitive) were partially cloned and sequenced; all resistant isolates had an alanine substitution that corresponded to position 143 of the gene product. These results indicate that QoI resistance is present in California populations of C. cereale and is contributing to the difficulty in controlling this disease.

scholarly journals pfmdr1Amplification Is Related to Increased Plasmodium falciparum In Vitro Sensitivity to the Bisquinoline Piperaquine

2012 ◽  
Vol 56 (7) ◽  
pp. 3615-3619 ◽  
Author(s):  
M. I. Veiga ◽  
P. E. Ferreira ◽  
M. Malmberg ◽  
L. Jörnhagen ◽  
A. Björkman ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Copy Number ◽  
Statistical Significance ◽  
Resistance Locus ◽  
Content Type ◽  
Enhanced Sensitivity ◽  
In Vitro Sensitivity ◽  
Artemisinin Combination Therapies

ABSTRACTThe 4-aminoquinoline bisquinoline piperaquine is an important partner drug in one of the presently recommended artemisinin combination therapies. Recent clinical trials have confirmed its high efficacy in combination with dihydroartemisinin. Resistance to piperaquine alone has, however, been documented. Amplification in copy number of thePlasmodium falciparummultidrug resistance locus on chromosome 5, containing thepfmdr1gene, has been shown to confer resistance to structurally unrelated antimalarials. Through the determination of the 50% inhibitory concentrations (IC50s) and IC90s for piperaquine and chloroquine in a set of 46 adaptedP. falciparumcultures originating from the Thai-Burmese border, we have characterized the regions around thepfmdr1gene and identified a significant association between the presence ofpfmdr1duplications and enhanced sensitivity to piperaquine (P= 0.005 for IC50andP= 0.002 for IC90) and chloroquine, reaching statistical significance at IC90s (P= 0.026). These results substantiate the potential importance ofpfmdr1copy number amplifications in the efficacy of the combination therapy piperaquine-dihydroartemisinin. It supports the rational use of 4-aminoquinolines and artemisinin-based compounds, as they independently select for mutually incompatible combinations of mutations.

Sign in / Sign up

Export Citation Format

Share Document