scholarly journals Global Distributions of Clarireedia Species and their In Vitro Sensitivity Profiles to Fungicides

Agronomy ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2036
Author(s):  
Jian Hu ◽  
Huangwei Zhang ◽  
Yinglu Dong ◽  
Shan Jiang ◽  
Kurt Lamour ◽  
...  
Keyword(s):  
Cynodon Dactylon ◽  
C4 Plants ◽  
Differential Sensitivity ◽  
Dollar Spot ◽  
C3 And C4 Plants ◽  
Fungicide Sensitivity ◽  
In Vitro Sensitivity ◽  
Paspalum Vaginatum ◽  
First Time

Dollar spot is reported to be caused by multiple Clarireedia species and is a serious problem on many turfgrasses around the world. To our knowledge, the distribution of different Clarireedia species and their sensitivity profiles to fungicides remains unknown. In this study, a total of 275 isolates were characterized by ITS sequence. Amounts of 124, 59 and 75 isolates were identified as C. jacksonii, C. monteithiana and C. paspali, respectively, while each species of C. homoeocarpa and C. bennettii had only five isolates. Four and three isolates were identified as two potential new species, which remained to be further characterized. C. jacksonii and C. monteithiana were distributed worldwide, while C. paspali was restricted to China. Of the isolates with host information, 81% (93/115) and 19% (22/115) of C. jacksonii isolates were collected from C3 and C4 plants, respectively, 97% (56/58) of the C. monteithiana isolates were collected from C4 plants and all C. paspali isolates were collected from C4 plants. The coexistence of different Clarireedia species on the same C4 host type in the same locales was found in Shanghai (Paspalum vaginatum), Jiangsu (Paspalum vaginatum) and Florida (Cynodon dactylon). The study revealed that differential fungicide sensitivity patterns were observed in different species in Clarireedia for the first time. Similar differential sensitivity profiles were also found in the locales with coexistence of at least two species. The findings from this study suggest that the adjacent coexistence of different Clarireedia species and the differential fungicide sensitivity profiles of different species will complicate dollar spot disease control.

Field Assessment of Six Point-Mutations in SDH Subunit Genes Conferring Varying Resistance Levels to SDHIs in Clarireedia spp.

Plant Disease ◽  
2021 ◽  
pp. PDIS-06-20-1344
Author(s):  
Jaemin Lee ◽  
Michaela R. Elliott ◽  
Toshihiko Yamada ◽  
Geunhwa Jung
Keyword(s):  
Cultural Practices ◽  
Point Mutations ◽  
Pathogenic Fungi ◽  
Field Conditions ◽  
Differential Sensitivity ◽  
Golf Courses ◽  
Dollar Spot ◽  
The Usa ◽  
Nation Wide Survey

Dollar spot, caused by Clarireedia spp. (formerly Sclerotinia homoeocarpa F.T. Bennett), is the most economically important turfgrass disease causing considerable damage on golf courses. While cultural practices are available for reducing dollar spot infection, chemical fungicide use is often necessary for maintaining optimal turf quality. Since the release of boscalid in 2003, the succinate dehydrogenase inhibitor (SDHI) class has become an invaluable tool for managing dollar spot. However, resistance to this class has recently been reported in Clarireedia spp. and many other plant pathogenic fungi. After SDHI field failure on four golf courses and one university research plot, a total of six unique SDH mutations conferring differential in vitro sensitivities to SDHIs have been identified in Clarireedia spp. In 2018 and 2019, turf research plots were inoculated with sensitive, non-mutated isolates of Clarireedia spp., as well as resistant isolates harboring each unique identified mutation. Fungicide efficacy trials were conducted on inoculated plots to assess differential sensitivity to five SDHI active ingredients (boscalid, fluxapyroxad, isofetamid, fluopyram, and pydiflumetofen) across mutations under field conditions. Results indicate unique mutations are associated with distinct SDHI field efficacy profiles as shown in in-vitro sensitivity assays. Isolate populations with B subunit mutations (H267Y/R) were more sensitive to fluopyram, whereas isolate populations with C subunit mutations (C-G91R, C-G150R) showed resistance to all SDHIs tested. Mutation-associated differential sensitivity observed under field conditions indicates a need for a nation-wide survey and frequent monitoring of SDHI sensitivity of dollar spot populations on golf courses in the USA. Further, the information gained from this study will be useful in providing sustainable management recommendations for controlling site-specific resistant populations of Clarireedia spp.

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 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 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.

Stem Rot of Peanut: Relationship Between in Vitro Fungicide Sensitivity and Field Efficacy of Fungicides

1998 ◽  
Vol 25 (2) ◽  
pp. 76-80 ◽  
Author(s):  
M. D. Franke ◽  
T. B. Brenneman ◽  
K. L. Stevenson
Keyword(s):  
Full Range ◽  
Sclerotium Rolfsii ◽  
Stem Rot ◽  
Fungicide Sensitivity ◽  
Pod Yield ◽  
In Vitro Sensitivity ◽  
Arachis Hypogaea L ◽  
Field Efficacy ◽  
Enhanced Yield

Abstract Isolates of Sclerotium rolfsii exhibiting varying degrees of in vitro fungicide sensitivity were exposed to fungicides in field microplots in 1995 and 1996. Individual peanut (Arachis hypogaea L.) plants in 0.9-m microplots were inoculated with isolates of S. rolfsii collected from peanut fields throughout Georgia. The 60 isolates used in the study represented the full range of sensitivity to the fungicides tebuconazole, flutolanil, and PCNB. After inoculation, microplots were treated with recommended rates of tebuconazole (0.227 kg ai/ha), flutolanil (0.337 kg ai/ha), PCNB (5.6 kg ai/ha), or were left untreated. Disease ratings were made at harvest, and pod yield from each plant was recorded. In both years, disease severity was significantly lower in treated microplots for all three fungicides. Isolates with lower in vitro fungicide sensitivity responded as well to labeled rates of all three fungicides as those with high in vitro sensitivity. In vitro sensitivity and percent control in treated microplots were not correlated for all three fungicides. Fungicide sensitivity and the level of infection in nontreated microplots also were not correlated for flutolanil and tebuconazole indicating that virulence was not affected by fungicide sensitivity. However, there was a negative correlation between in vitro sensitivity to PCNB and the level of infection in nontreated microplots in 1995, indicating that isolates with lower in vitro sensitivity were more virulent. However, this trend was not observed when the same isolates were evaluated in 1996. In 1995, plants in PCNB-treated microplots had a significantly higher yield than those in the nontreated microplots. In 1996, all fungicide treatments significantly enhanced yield. Because in vitro sensitivity and field efficacy were not correlated for all three fungicides, labeled rates should control stem rot in the field.

scholarly journals Sensitivity of Sclerotinia homoeocarpa Isolates to Propiconazole and Impact on Control of Dollar Spot

Plant Disease ◽  
2002 ◽  
Vol 86 (11) ◽  
pp. 1240-1246 ◽  
Author(s):  
Gerald L. Miller ◽  
Katherine L. Stevenson ◽  
Leon L. Burpee
Keyword(s):  
Field Resistance ◽  
Cross Resistance ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
In Planta ◽  
In Vitro Sensitivity ◽  
Progress Curve ◽  
Exposed Population ◽  
Positive Correlations

In response to reports of reduced efficacy of propiconazole for control of dollar spot, isolates of Sclerotinia homoeocarpa were collected from several locations in Georgia and tested for sensitivity to propiconazole and other demethylation-inhibiting (DMI) fungicides. Two discriminatory concentrations of propiconazole (0.02 and 0.2 μg ml-1) were used to detect lower in vitro sensitivity in two populations that had been exposed repeatedly to propiconazole than in four nonexposed populations. Mean 50% effective concentration (EC50) values for a nonexposed population (baseline) and a DMI-exposed population were 0.0049 and 0.0283 μg ml-1, respectively. Positive correlations were significant among log10 EC50 values for propiconazole, fenarimol, and myclobutanil but not between triadimefon and any of the other three fungicides, indicating cross-resistance relationships in this pathogen may not be universal among the DMIs. In greenhouse experiments, propiconazole-treated bentgrass was inoculated with seven isolates of S. homoeocarpa differing in sensitivity to propiconazole. Incubation period decreased and relative area under the disease progress curve and disease severity 28 days after inoculation increased linearly with increasing log10 EC50 value of the isolate. Results of this study confirm a significant relationship between in vitro sensitivity of S. homoeocarpa and in planta control efficacy of propiconazole and provide evidence of field resistance to propiconazole in S. homoeocarpa in Georgia.

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.

Ultrastructural Changes in Three Different Mammalian Cells Following Ultraviolet Laser Irradiation

1972 ◽  
Vol 30 ◽  
pp. 350-351
Author(s):  
K. Shankar Narayan ◽  
Kailash C. Gupta ◽  
Tohru Okigaki
Keyword(s):  
Ultraviolet Light ◽  
Mammalian Cells ◽  
Biological Effects ◽  
Survival Rates ◽  
Chinese Hamster ◽  
Cell Types ◽  
Differential Sensitivity ◽  
Ultrastructural Changes ◽  
Ultraviolet Laser

The biological effects of short-wave ultraviolet light has generally been described in terms of changes in cell growth or survival rates and production of chromosomal aberrations. Ultrastructural changes following exposure of cells to ultraviolet light, particularly at 265 nm, have not been reported.We have developed a means of irradiating populations of cells grown in vitro to a monochromatic ultraviolet laser beam at a wavelength of 265 nm based on the method of Johnson. The cell types studies were: i) WI-38, a human diploid fibroblast; ii) CMP, a human adenocarcinoma cell line; and iii) Don C-II, a Chinese hamster fibroblast cell strain. The cells were exposed either in situ or in suspension to the ultraviolet laser (UVL) beam. Irradiated cell populations were studied either "immediately" or following growth for 1-8 days after irradiation.Differential sensitivity, as measured by survival rates were observed in the three cell types studied. Pattern of ultrastructural changes were also different in the three cell types.

Somatic Embryogenesis and In vitro Plant Regeneration in Vigna trilobata (L.) Verd. - A Potential Pasture Legume

1970 ◽  
Vol 19 (1) ◽  
pp. 89-99
Author(s):  
K. Choudhary ◽  
M. Singh ◽  
M. S. Rathore ◽  
N. S. Shekhawat
Keyword(s):  
Somatic Embryogenesis ◽  
Growth Regulators ◽  
Somatic Embryos ◽  
Basal Medium ◽  
Long Term Study ◽  
Continuous Application ◽  
First Time ◽  
Pasture Legume

This long term study demonstrates for the first time that it is possible to propagate embryogenic Vigna trilobata and to subsequently initiate the differentiation of embryos into complete plantlets. Initiation of callus was possible on 2,4-D. Somatic embryos differentiated on modified MS basal nutrient medium with 1.0 mg/l  of 2,4-D and 0.5 mg/l  of Kn. Sustained cell division resulted in globular and heart shape stages of somatic embryos. Transfer of embryos on to a fresh modified MS basal medium with 0.5 mg/l of Kn and 0.5 mg/l of GA3 helped them to attain maturation and germination. However, the propagation of cells, as well as the differentiation of embryos, were inhibited by a continuous application of these growth regulators. For this reason, a long period on medium lacking these growth regulators was necessary before the differentiation of embryos occurred again. The consequences for improving the propagation of embryogenic cultures in Vigna species are discussed. Key words: Pasture  legume, Vigna trilobata, Globular, Heart shape, somatic embryogenesis D.O.I. 10.3329/ptcb.v19i1.4990 Plant Tissue Cult. & Biotech. 19(1): 89-99, 2009 (June)

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