scholarly journals Brachypodium: A Potential Model Host for Fungal Pathogens of Turfgrasses

2017 ◽  
Vol 107 (6) ◽  
pp. 749-757 ◽  
Author(s):  
Renee A. Rioux ◽  
Benjamin J. Van Ryzin ◽  
James P. Kerns
Keyword(s):  
Fungal Pathogens ◽  
Molecular Mechanisms ◽  
Brachypodium Distachyon ◽  
Creeping Bentgrass ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Cool Season ◽  
Host System ◽  
Brown Patch ◽  
Compatible Interactions

Brachypodium distachyon is a C3 grass that is an attractive model host system for studying pathogenicity of major turfgrass pathogens due to its genetic similarity to many cool-season turfgrasses. Infection assays with two or more isolates of the casual agents of dollar spot, brown patch, and Microdochium patch resulted in compatible interactions with B. distachyon inbred line Bd21-3. The symptoms produced by these pathogens on Bd21-3 closely resembled those observed on the natural turfgrass host (creeping bentgrass), demonstrating that B. distachyon is susceptible to the fungal pathogens that cause dollar spot, brown patch, and Microdochium patch on turfgrasses. The interaction between Sclerotinia homoeocarpa isolates and Brachypodium ecotypes was also investigated. Interestingly, differential responses of these ecotypes to S. homoeocarpa isolates was found, particularly when comparing B. distachyon to B. hybridum ecotypes. Taken together, these findings demonstrate that B. distachyon can be used as a model host system for these turfgrass diseases and leveraged for studies of molecular mechanisms contributing to host resistance.

Dollar Spot in Four Bentgrass Cultivars as Affected by Acibenzolar-S-Methyl and Organic Fertilizers

2003 ◽  
Vol 4 (1) ◽  
pp. 5 ◽  
Author(s):  
Joon Lee ◽  
Jack Fry ◽  
Ned Tisserat
Keyword(s):  
Organic Fertilizer ◽  
Creeping Bentgrass ◽  
Organic Fertilizers ◽  
Sclerotinia Homoeocarpa ◽  
Agrostis Palustris ◽  
Dollar Spot ◽  
Putting Greens ◽  
Brown Patch ◽  
Growing Seasons ◽  
Progress Curve

Golf course superintendents are interested in identifying ways to reduce fungicide inputs on creeping bentgrass (Agrostis palustris Huds.) putting greens. Our objectives were to evaluate the influence of the plant defense activator acibenzolar-S-methyl (ASM, Actigard, Syngenta Corp., Basel, Switzerland) and organic fertilizers on dollar spot (Sclerotinia homoeocarpa F.T. Bennett) and brown patch (Rhizoctonia solani Kuhn) in four bentgrass cultivars. Crenshaw had over 10 times the area under the disease progress curve (AUDPC) value for dollar spot compared to the cultivar L-93 in 2000. Acibenzolar-S-methyl applied at 35 g a.i. per ha every 14 days between mid-May and mid-September for two consecutive growing seasons reduced the number of S. homoeocarpa infection centers by 15% in Crenshaw, 24% in Penncross, and 29% in Providence, but had no effect on the number of infection centers in L-93. Only Sustane (Crenshaw in 2000) and Milorganite (Crenshaw and Providence in 2001) suppressed dollar spot compared to urea. The following fertilizers resulted in an increase in S. homoeocarpa infection centers: Nature Safe 8-1.3-4.2 in Crenshaw in both years, and in Providence in 2000; Nature Safe 10-0.9-6.6 in Crenshaw in both years; and Sustane with Iron in Crenshaw in 2001. All other organic fertilizer × cultivar combinations resulted in dollar spot levels equivalent to those observed in ureatreated turf. Brown patch levels were not affected by cultivar, ASM, or organic fertilizers. The defense activator ASM deserves further evaluation as a tool to reduce dollar spot-targeted fungicide inputs in creeping bentgrass. Accepted for publication 5 June 2003. Published 26 June 2003.

scholarly journals Dollar Spot and Brown Patch Incidence in Creeping Bentgrass as Affected by Acibenzolar-S-Methyl and Biostimulants

HortScience ◽  
2003 ◽  
Vol 38 (6) ◽  
pp. 1223-1226 ◽  
Author(s):  
Joon Lee ◽  
Jack Fry ◽  
Ned Tisserat
Keyword(s):  
Experimental Design ◽  
Plant Defense ◽  
Cultural Practices ◽  
Creeping Bentgrass ◽  
Sclerotinia Homoeocarpa ◽  
Agrostis Palustris ◽  
Dollar Spot ◽  
Putting Greens ◽  
Brown Patch ◽  
Turf Quality

There is interest in identifying cultural practices that may reduce fungicide requirements of creeping bentgrass (Agrostis palustris Huds.) putting greens. Our objective was to evaluate the plant defense activator ASM in combination with 12 biostimulants for the potential to reduce dollar spot (Sclerotinia homoeocarpa F.T. Bennett) and brown patch (Rhizoctonia solani Kuhn) in a blend of `Cato: `Crenshaw creeping bentgrass during 2000 and 2001. The experimental design was a split-plot with ASM as the whole plot, and biostimulants as the subplots. ASM was applied biweekly as a.i. at 35 g·ha-1 and biostimulants were applied according to manufacturers recommendations. Sclerotinia homoeocarpa infection centers were reduced by 38% with ASM, but levels were >1500/m2 in Aug. 2000, and turf quality was unacceptable through most of the study period. No suppression of brown patch occurred with ASM. None of the biostimulants reduced dollar spot or brown patch in creeping bentgrass when compared to biweekly applications of soluble N at 4.9 kg·ha-1. Dollar spot suppression achieved with ASM warrants additional studies to determine how it might be used to reduce fungicide inputs on creeping bentgrass putting greens. Chemical name used: acibenzolar-S-methyl (ASM).

scholarly journals A Dimorphic and Virulence-Enhancing Endosymbiont Bacterium Discovered in Rhizoctonia solani

2017 ◽  
Vol 1 (1) ◽  
pp. 14-23 ◽  
Author(s):  
Ken Obasa ◽  
Frank F. White ◽  
John Fellers ◽  
Megan Kennelly ◽  
Sanzhen Liu ◽  
...  
Keyword(s):  
Rhizoctonia Solani ◽  
Dna Analysis ◽  
Higher Plants ◽  
Intracellular Localization ◽  
Creeping Bentgrass ◽  
Single Species ◽  
Cool Season ◽  
Plant Host ◽  
Brown Patch ◽  
Bacterial Endosymbionts

The ubiquitous soilborne and plant-pathogenic basidiomycete Rhizoctonia solani, although classified as a single species, is a complex of anastomosis groups (AGs) that cause disease in a broad range of higher plants. Here, we investigated the persistent co-isolation of bacteria with R. solani from brown patch-infected, cool-season turfgrasses, and report the presence of endo-hyphal bacteria, related to members in the genus Enterobacter, in an isolate of R. solani AG 2-2IIIB. The intracellular localization of the bacteria was corroborated by fluorescence, confocal and electron microscopy, and DNA analysis. Furthermore, the Enterobacter sp., which is rod-shaped in the free-living form, exists as an L-form (spheroid) within the fungus, a phenomenon not previously reported in endosymbionts. Our findings also indicate that the bacterium is required for full virulence of R. solani on creeping bentgrass and production of wild type levels of the toxin phenylacetic acid in fungal cultures. The possible presence of bacterial endosymbionts in R. solani AG 2-2IIIB may portend the presence of bacteria in additional AGs as well as other Rhizoctonia species, and may help resolve some of the complexities of R. solani pathogenicity. A closely associated bacterium could influence aspects of plant host pathology.

scholarly journals Residual Efficacy of Fungicides for Control of Dollar Spot on Creeping Bentgrass

Plant Disease ◽  
2006 ◽  
Vol 90 (5) ◽  
pp. 571-575 ◽  
Author(s):  
Richard Latin
Keyword(s):  
Creeping Bentgrass ◽  
Effective Concentration ◽  
Disease Suppression ◽  
Golf Course ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Residual Efficacy ◽  
Bioassay Technique ◽  
Precipitous Decline ◽  
Field Plots

The duration of effective concentrations of fungicides for control of dollar spot on creeping bentgrass fairways was investigated using a bioassay technique. In each of three runs of the experiment, fungicide treatments were applied once to turf in replicated field plots; then, the plots were sampled periodically over 3 weeks by removing turf plugs from the field. The sampled plugs were placed in incubation containers and inoculated with sections from a 4-day-old colony of Sclerotinia homoeocarpa growing on potato dextrose agar. After a 96-h incubation period, the extent of pathogen growth on the turf plugs was measured. Results described a precipitous decline in effective concentration for all fungicide treatments beginning 7 to 10 days after application. The fungicides were only marginally effective at 14 days after application, and none provided any disease suppression at 21 days after application. The efficacy half-life (EHL) associated with four of the fungicides (chlorothalonil, iprodione, propiconazole, and thiophanate methyl) was estimated with two models. EHL estimates ranged from 6.1 to 15.2 days depending on the fungicide and the model. This research contributes to our knowledge of the duration of effective fungicide concentrations on creeping bentgrass and can provide insight for scheduling fungicide sprays for golf course fairways.

scholarly journals Genetic Diversity of Sclerotinia homoeocarpa Isolates from Turfgrasses from Various Regions in North America

Plant Disease ◽  
2004 ◽  
Vol 88 (11) ◽  
pp. 1269-1276 ◽  
Author(s):  
G. Viji ◽  
W. Uddin ◽  
N. R. O'Neill ◽  
S. Mischke ◽  
J. A. Saunders
Keyword(s):  
United States ◽  
Genetic Diversity ◽  
Creeping Bentgrass ◽  
The United States ◽  
Vegetative Compatibility ◽  
Major Group ◽  
Golf Courses ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Geographical Regions

Sixty-seven isolates of Sclerotinia homoeocarpa, causing dollar spot disease in creeping bentgrass, annual bluegrass, Bermudagrass, and perennial ryegrass turf, collected from 23 golf courses in various geographical regions of the United States and Canada between 1972 and 2001, were characterized by vegetative compatibility, genetic diversity, and pathogenicity. Eleven vegetative compatibility groups (VCGs A to K) were identified among the isolates tested in this study, and five of them (VCGs G to K) were new. VCG B was the most predominant group, typifying 33 isolates (51%) tested. S. homoeocarpa isolates collected from golf courses in Pennsylvania belonged to seven VCGs (A, B, E, F, G, I, and K), whereas three groups were observed in those collected from New York (B, E, and G) and New Jersey (E, H, and I). Two isolates, one each from Pennsylvania and Canada, were incompatible when paired with the tester isolates in all possible combinations, and did not fall into any known VCG. An isolate collected from Canada was compatible with tester isolates from two VCGs (C and D). Genetic analyses using amplified fragment length polymorphism (AFLP) showed the presence of two genetically distinct groups, designated as major group and the minor group. The major group included 36 isolates collected from various golf courses in the United States and Canada. Two isolates collected from bermudagrass in Florida formed a separate cluster, the minor group. Isolates that belonged to the major group were further divided into two subgroups (1 and 2). Subgroup 1 consisted of all the isolates that belonged to VCGs A, E, G, H, and I. Three of the four isolates that belonged to VCG K also were clustered with isolates of subgroup 1. Subgroup 2 consisted of all the isolates from VCG B, and one each from VCGs F and K. Pathogenicity assays on Penncross creeping bentgrass showed significant differences (P = 0.05) in virulence among the isolates. Overall, a relationship between virulence and VCGs was observed, in which certain virulence groups corresponded to specific VCGs; however, such a relationship was not observed between virulence and AFLPs. Close similarity among isolates of S. homoeocarpa collected from different locations in the United States and Canada suggests that isolates of the same genotype could be involved in outbreaks of dollar spot epidemics at multiple locations.

scholarly journals Mowing Frequency and Plant Growth Regulator Effects on Dollar Spot Severity and on Duration of Dollar Spot Control by Fungicides

Plant Disease ◽  
2011 ◽  
Vol 95 (11) ◽  
pp. 1433-1442 ◽  
Author(s):  
Alexander I. Putman ◽  
John E. Kaminski
Keyword(s):  
Plant Growth ◽  
Creeping Bentgrass ◽  
Agrostis Stolonifera ◽  
Golf Course ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Confounding Effect ◽  
Residual Efficacy ◽  
The University ◽  
University Of Connecticut

Management of dollar spot (incited by Sclerotinia homoeocarpa) on golf course fairways is increasingly challenging. The objectives of this study were to determine the influence of mowing frequency and plant growth regulators (PGRs) on dollar spot severity and on the residual efficacy of fungicides for control of dollar spot. Two 4-month-long studies were conducted on ‘Putter’ creeping bentgrass (Agrostis stolonifera) maintained as a fairway at the University of Connecticut. Treatments were arranged in a three-by-three-by-five factorial that assessed the influence of mowing frequency (2, 4, or 6 days week–1) and PGRs (paclobutrazol, trinexapac-ethyl, or none) on dollar spot control by five fungicide treatments (boscalid, chlorothalonil, iprodione, propiconazole, or none). Turf was mowed in the afternoon hours to minimize the confounding effect of mowing frequency on leaf wetness duration. Treatments were initiated in the late spring of 2007 and 2008, and each fungicide treatment was reapplied only when dollar spot exceeded a threshold of five infection centers plot–1. In the absence of fungicides, dollar spot severity was reduced by 63 to 90% in plots treated with paclobutrazol and by 13 to 55% in plots treated with trinexapac-ethyl. Dollar spot severity was 23 to 50% lower in plots mown 2 days week–1 compared with those mown 6 days week–1. In cases where a significant interaction was observed between mowing frequency and PGRs, dollar spot was reduced on most rating dates in plots treated with trinexapacethyl that were mown 2 days week–1 compared with those mown 6 days week–1. Survival analysis of days until threshold was met revealed that duration of control of fungicides in plots receiving paclobutrazol were 28 to 84% longer compared with plots not receiving PGR. Duration of control by fungicides was generally similar between plots treated with trinexapac-ethyl and no PGR. In general, mowing frequency did not influence duration of control. Results from this study indicate that paclobutrazol could be used to increase the treatment interval of fungicides and that mowing frequency in the absence of dew is likely to have little influence on fungicide residual efficacy. When used without fungicides, PGRs and less frequent mowing may reduce dollar spot in situations where fungicide use is limited.

RELATIONSHIP BETWEEN WEATHER FACTORS AND DOLLAR SPOT OF CREEPING BENTGRASS

1984 ◽  
Vol 64 (1) ◽  
pp. 167-174 ◽  
Author(s):  
ROBERT HALL
Keyword(s):  
Disease Control ◽  
Creeping Bentgrass ◽  
Weather Conditions ◽  
Acceptable Level ◽  
Sclerotinia Homoeocarpa ◽  
Agrostis Palustris ◽  
Dollar Spot ◽  
Weather Factors ◽  
Average Temperature

In 1981 and 1982 epidemics of dollar spot of creeping bentgrass, caused by Sclerotinia homoeocarpa, proceeded in a series of steps. Each step began at a point where a decline in the epidemic rate was followed by an increase in the epidemic rate and continued until a new step began. A step in the epidemic occurred after two consecutive wet days if the average temperature for the period was at or above 22 °C or after three or more consecutive wet days if the average temperature for the period was 15 °C or greater. These weather conditions were referred to as "infection periods." In 1982, an application of Tersan 1991 (benomyl) 1 and 2 days after two infection periods provided an acceptable level of disease control as effective as that obtained from a regular preventive schedule of seven sprays.Key words: Agrostis palustris, disease control, Sclerotinia homoeocarpa, weather-timed spray

scholarly journals Factors affecting pathogenicity of the turfgrass dollar spot pathogen in natural and model hosts

2019 ◽  
Author(s):  
R.A. Rioux ◽  
C.M. Stephens ◽  
J.P. Kerns
Keyword(s):  
Oxalic Acid ◽  
Time Course ◽  
Creeping Bentgrass ◽  
Initial Contact ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Factors Affecting ◽  
Whole Plant ◽  
Host Infection

AbstractClarireediasp. (formerly calledSclerotinia homoeocarpa), the fungal pathogen that causes dollar spot of turfgrasses, produces oxalic acid but the role of this toxin inClarireediasp. pathogenesis is unknown. In the current study, whole plant inoculation assays were used to evaluate pathogenesis ofClarireediasp. in various model hosts and investigate the role of oxalic acid in dollar spot disease. These assays revealed that both host endogenous oxalate content and pathogen-produced oxalic acid influence the timing and magnitude of symptom development. In time-course expression analysis, oxalate oxidase and related defense-associated germin-like protein genes in creeping bentgrass showed strong up-regulation starting at 48-72 hpi, indicating that germin-like protein genes are most likely involved in defense following initial contact with the pathogen and demonstrating the importance of oxalic acid inClarireediasp. pathogenesis. Overall, the results of these studies suggest that oxalic acid and host endogenous oxalate content are important for pathogenesis byClarireediasp. and may be associated with the transition from biotrophy to necrotrophy during host infection.

scholarly journals Seasonal Development of Dollar Spot Epidemics in Six Creeping Bentgrass Cultivars in Maryland

HortScience ◽  
2012 ◽  
Vol 47 (3) ◽  
pp. 422-426 ◽  
Author(s):  
Christopher P. Ryan ◽  
Peter H. Dernoeden ◽  
Arvydas P. Grybauskas
Keyword(s):  
Creeping Bentgrass ◽  
Seasonal Development ◽  
Golf Courses ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Severe Damage ◽  
Start Date ◽  
Degree Day ◽  
Progress Curve ◽  
The Many

This 3-year field study evaluated the incidence and severity of dollar spot (Sclerotinia homoeocarpa F.T. Bennett) in six creeping bentgrass (Agrostis stolonifera L.) cultivars maintained as a golf course fairway. Comparison of area under the disease progress curve (AUDPC) data clearly indicted two resistance groups among the six cultivars. ‘Crenshaw’ and ‘Backspin’ were classified as highly susceptible (HS) and the other four cultivars (i.e., ‘Penncross’, ‘Providence’, ‘L-93’, and ‘007’) were classified as moderately susceptible (MS) to dollar spot. In all three study years, there were three epidemics that began in May. Data could not be collected in HS cultivars after the first epidemic in each year as a result of severe damage. In MS cultivars, the first epidemic ended and a second began between early July and late August. The second epidemic ended approximately mid-October and a third epidemic appeared in MS cultivars between late October and early December. The second epidemic was longest and most severe, and the third fall epidemic was least severe and of shortest duration. The first epidemic in HS cultivars developed up to two weeks earlier and progressed more rapidly and severely than in MS cultivars. A growing degree-day (GDD) model, using a base air temperature of 15 °C and a start date of 1 Apr., was accurate in predicting the onset of the first epidemic in HS (60 to 70 GDD) and MS (105 to 115 GDD) cultivars during each of the three study years. Growing degree-day models are greatly influenced by the many microclimates found on golf courses and need to be evaluated for accuracy in diverse environments.

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