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Dollar spot caused by Clarireedia spp. (formerly Sclerotinia homoeocarpa) is an economically destructive fungal disease of turfgrass that can significantly compromise turf quality, playability, and aesthetic value. Fungicides are frequently used to manage the disease but are costly and potentially unfavorable to the environment. Repeated use of some active ingredients has resulted in reduced efficacy on C. jacksonii causing dollar spot in cool-season turfgrasses in the US. Experiments were conducted to study fungicide sensitivity of Clarireedia spp. as well as to develop alternatives to fungicides against dollar spot on warm-season turfgrass in Georgia. First, 79 isolates of Clarireedia spp. collected across the state were tested on fungicide-amended agar plates for their sensitivity to thiophanate-methyl (benzimidazole) and propiconazole (dimethyl inhibitor). Seventy-seven isolates (97.5%) were sensitive (0.001 to 0.654 mg/mL) and two isolates (2.5%) were found resistant (>1000 mg/mL) to thiophanate-methyl. However, in the case of propiconazole, 27 isolates (34.2%) were sensitive (0.005 to 0.098 mg/mL) while 52 isolates (65.8%) were resistant (0.101 to 3.820 mg/mL). Next, the efficacy of three bio- and six synthetic fungicides and ten different combinations were tested in vitro against C. monteithiana. Seven bio- and synthetic fungicide spray programs comprising Bacillus subtilis QST713 and propiconazole were further tested, either alone or in a tank mix in a reduced rate, on dollar spot infected bermudagrass 'TifTuf' in growth chamber and field environments. These fungicides were selected as they were found to significantly reduce pathogen growth up to 100% on in vitro assays. The most effective spray program in growth chamber assays was 100% B. subtilis QST713 in rotation with 75% B. subtilis QST713 + 25% propiconazole tank mix applied every 14 days. However, the stand-alone application of the biofungicide B. subtilis QST713 every seven days was an effective alternative and equally efficacious as propiconazole, suppressing dollar spot severity and AUDPC up to 75%, while resulting in acceptable turf quality (>7.0) in field experiments. Our study suggests that increased resistance of Clarireedia spp. to benzimidazoles and dimethyl inhibitors warrants continuous surveillance and that biofungicides hold promise to complement synthetic fungicides in an efficacious and environmentally friendly disease management program. [ABSTRACT FROM AUTHOR]

The new genus Bryorutstroemia is established for the red-brown, stipitate, bryoparasitic discomycete Helotium fulvum Boud. Combined phylogenetic analysis of ITS and LSU rDNA and EF1α revealed that Bryorutstroemia fulva belongs to the sclerotiniaceous clade, which comprises the paraphyletic families Rutstroemiaceae and Sclerotiniaceae. Bryorutstroemia formed with Clarireedia a supported clade (Rutstroemiaceae s.l.), though with high distance. Bryorutstroemia closely resembles other Rutstroemiaceae in having uninucleate ascospores with high lipid content and an ectal excipulum of textura porrecta, but is unique because of its bryophilous lifestyle and is extraordinary with its thick-walled inamyloid ascus apex. Although B. fulva was described in 1897, very few records came to our notice. The present study summarizes the known distribution of the species, including 25 personal collections from the years 2001–2022. Bryorutstroemia fulva was most often encountered on Dicranella heteromalla, and rarely on other members of Dicranales or Grimmiales, while inducing necrobiosis of the leaves. A detailed description based on mainly fresh apothecia is provided together with a rich photographic documentation. Six new combinations are proposed based on our phylogenetic results and unpublished personal morphological studies: Clarireedia asphodeli, C. calopus, C. gladioli, C. henningsiana, C. maritima, and C. narcissi. [ABSTRACT FROM AUTHOR]

BACKGROUND: Dollar spot (DS) is one of the most destructive and economically important diseases of cool‐ and warm‐season turfgrasses worldwide. A total of six species causing DS disease in the genus Clarireedia have been described, and four of them have been reported to be distributed countrywide in China. Identification of different species of Clarireedia is a prerequisite for the effective management of DS disease. RESULTS: Here we report a novel polymerase chain reaction (PCR)‐based method for the detection and differentiation of the four species of Clarireedia associated with DS on turfgrass in China: C. jacksonii, C. paspali, C. monteithiana and C. hainanense. Species‐specific genes were identified for each species by comparative genomics analysis. Four primer pairs were designed and mixed to amplify species‐specific PCR fragments with differential sizes for the four species of Clarireedia in a single multiplex PCR assay. No PCR products were generated from the DNA templates of other common fungal pathogens associated with multiple turfgrass diseases. The multiplex PCR method developed can be used for the rapid and accurate detection and differentiation of the four species of Clarireedia from pure cultures as well as from infected turfgrass blades with DS symptoms. CONCLUSION: The study developed a one‐step multiplex PCR assay for the detection and differentiation of four species of Clarireedia causing DS on turfgrass in China, which will have important implications for DS management in China and worldwide. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Dollar spot caused by Clarireedia spp. (formerly Sclerotinia homoeocarpa) is an economically destructive fungal disease of turfgrass that can significantly compromise turf quality, playability, and aesthetic value. Fungicides are frequently used to manage the disease but are costly and potentially unfavorable to the environment. Repeated use of some active ingredients has resulted in reduced efficacy on C. jacksonii causing dollar spot in cool-season turfgrasses in the US. Experiments were conducted to study fungicide sensitivity of Clarireedia spp. as well as to develop alternatives to fungicides against dollar spot on warm-season turfgrass in Georgia. First, 79 isolates of Clarireedia spp. collected across the state were tested on fungicide-amended agar plates for their sensitivity to thiophanate-methyl (benzimidazole) and propiconazole (dimethyl inhibitor). Seventy-seven isolates (97.5%) were sensitive (0.001 to 0.654 μg/mL) and two isolates (2.5%) were found resistant (>1000 μg/mL) to thiophanate-methyl. However, in the case of propiconazole, 27 isolates (34.2%) were sensitive (0.005 to 0.098 μg/mL) while 52 isolates (65.8%) were resistant (0.101 to 3.820 μg/mL). Next, the efficacy of three bio- and six synthetic fungicides and ten different combinations were tested in vitro against C. monteithiana. Seven bio- and synthetic fungicide spray programs comprising Bacillus subtilis QST713 and propiconazole were further tested, either alone or in a tank mix in a reduced rate, on dollar spot infected bermudagrass ‘TifTuf’ in growth chamber and field environments. These fungicides were selected as they were found to significantly reduce pathogen growth up to 100% on in vitro assays. The most effective spray program in growth chamber assays was 100% B. subtilis QST713 in rotation with 75% B. subtilis QST713 + 25% propiconazole tank mix applied every 14 days. However, the stand-alone application of the biofungicide B. subtilis QST713 every seven days was an effective alternative and equally efficacious as propiconazole, suppressing dollar spot severity and AUDPC up to 75%, while resulting in acceptable turf quality (>7.0) in field experiments. Our study suggests that increased resistance of Clarireedia spp. to benzimidazoles and dimethyl inhibitors warrants continuous surveillance and that biofungicides hold promise to complement synthetic fungicides in an efficacious and environmentally friendly disease management program.

Dollar spot is an important disease of both cool- and warm-season turfgrasses caused by six fungal species in the genus Clarireedia , yet the ecology and epidemiology of these pathogens remains poorly understood. The goal of this study was to determine the distribution of Clarireedia in asymptomatic and symptomatic creeping bentgrass ( Agrostis stolonifera ) in the field using a previously developed quantitative PCR assay. To determine the horizontal distribution of the pathogen, the abundance of Clarireedia spp. was measured in leaf and crown tissue from 90, 1-cm-diameter cores spaced 10 cm apart in May 2019 and 2020 (asymptomatic tissue) and August 2019 and July 2020 (symptomatic tissue). Thirty-seven to 69% of cores sampled from asymptomatic turfgrass and 77 to 95% of cores taken from symptomatic turfgrass yielded positive detections for Clarireedia . Spatial analysis indicated that Clarireedia was randomly distributed in the field in both asymptomatic and symptomatic turfgrass. To assess the vertical distribution of the pathogen, the abundance of Clarireedia was measured in the foliar, crown, and thatch layers of 39, 1-cm-diameter × 2.5-cm-deep cores of creeping bentgrass maintained at fairway height (9.5 mm) during 2019 and 2020. Clarireedia was most abundant in foliar tissue, followed by crown tissue and thatch (lowest abundance) throughout the 2-year study. Both studies provide evidence that Clarireedia is widely distributed in turfgrass swards prior to symptom development and can persist within turfgrass as an endophyte. These findings will improve our understanding of Clarireedia epidemiology and may lead to more sustainable dollar spot management., Competing Interests: The author(s) declare no conflict of interest.

Dollar spot is a major fungal disease affecting turfgrass worldwide and can quickly destroy turfgrass swards. An assimilating probe-based loop-mediated isothermal amplification (LAMP) assay was developed to detect Clarireedia monteithiana and C. jacksonii , the causal agents of dollar spot within the continental United States. Five LAMP primers were designed to target the calmodulin gene with the addition of a 6-carboxyl-fluorescein florescent assimilating probe, and the temperature amplification was optimized for C. jacksonii and C. monteithiana identification. The minimum amount of purified DNA needed for detection was 0.05 ng μl -1 . Specificity assays against host DNA and other turfgrass pathogens were negative. Successful LAMP amplification was also observed for dollar spot-infected turfgrass field samples. Further, a DNA extraction technique via rapid heat-chill cycles and visualization of LAMP results via a florescent flashlight was developed and adapted for fast, simple, and reliable detection in 1.25 h. This assimilating probe-based LAMP assay has proved successful as a rapid, sensitive, and specific method for the detection of C. monteithiana and C. jacksonii in pure cultures and from symptomatic turfgrass leaves blades. The assay represents a promising technology to be used in the field for on-site, point-of-care pathogen detection., Competing Interests: The author(s) declare no conflict of interest.

The new genus Bryorutstroemia is established for the red-brown, stipitate, bryoparasitic discomycete Helotium fulvum Boud. Combined phylogenetic analysis of ITS and LSU rDNA and EF1α revealed that Bryorutstroemia fulva belongs to the sclerotiniaceous clade, which comprises the paraphyletic families Rutstroemiaceae and Sclerotiniaceae. Bryorutstroemia formed with Clarireedia a supported clade (Rutstroemiaceae s.l.), though with high distance. Bryorutstroemia closely resembles other Rutstroemiaceae in having uninucleate ascospores with high lipid content and an ectal excipulum of textura porrecta, but is unique because of its bryophilous lifestyle and is extraordinary with its thick-walled inamyloid ascus apex. Although B. fulva was described in 1897, very few records came to our notice. The present study summarizes the known distribution of the species, including 25 personal collections from the years 2001–2022. Bryorutstroemia fulva was most often encountered on Dicranella heteromalla, and rarely on other members of Dicranales or Grimmiales, while inducing necrobiosis of the leaves. A detailed description based on mainly fresh apothecia is provided together with a rich photographic documentation. Six new combinations are proposed based on our phylogenetic results and unpublished personal morphological studies: Clarireedia asphodeli, C. calopus, C. gladioli, C. henningsiana, C. maritima, and C. narcissi.

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.

Dollar spot (DS) is a destructive fungal disease impacting almost all warm- and cool-season turfgrasses worldwide. Multiple fungal species in the genus Clarireedia are causal agents of DS. Here, we present whole-genome assemblies of nine fungal isolates in the genus Clarireedia , including four species ( C. paspali , C. hainanense , C. jacksonii , and C. monteithiana ) causing DS on seashore paspalum ( Paspalum vaginatum Sw.), creeping bentgrass ( Agrostis stolonifera L.), and Kentucky bluegrass ( Poa pratensis L.) in China. This work provides valuable baseline genomic data to support further research and management of DS pathogens on turfgrasses.

The genus Clarireedia contains multiple species causing dollar spot (DS) on turfgrass worldwide. In November 2020, 119 Clarireedia isolates were obtained from symptomatic seashore paspalum at golf courses in Hainan province and identified to species level based on partial sequence of the internal transcribed spacer (ITS) region. A total of 45 and 22 isolates were identified as C. paspali and C. monteithiana , respectively; the remaining 52 isolates defined a new clade. Isolates from this clade were further selected for phylogenetic, morphological, and biological analyses. Maximum likelihood and Bayesian methods were implemented to obtain phylogenetic trees for partial sequences of the ITS, EF-1α , and McM7 genes. The selected isolates consistently fell into a distinct, well-supported clade within Clarireedia . Morphological and biological characteristics were observed among the different species in Clarireedia . Altogether, this study described a new species, Clarireedia hainanense , which has widespread distribution in Hainan, China. These findings may have important implications for the management of DS disease.

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. [ABSTRACT FROM AUTHOR]

Dollar spot, caused by the ascomycete fungus Clarireedia (formerly Sclerotinia ), is one of the most resource-demanding diseases on amenity turfgrasses in North America. Differential resistance to the succinate dehydrogenase inhibitor (SDHI) fungicide class, conferred by singular point mutations on the Sdh B, Sdh C, and SdhD subunits of the succinate dehydrogenase enzyme (SDH), has been reported in dollar spot as well as many other plant-pathogenic fungal diseases. Four unique mutations were previously reported from Clarireedia field isolates collected from two different cool-season golf courses in Japan and Rhode Island: an amino acid substitution H267Y and a silent mutation (CTT to CTC) at codon 181 on the Sdh B subunit gene, and amino acid substitutions G91R and G150R on the Sdh C subunit gene. To properly diagnose and monitor SDHI resistance in the field, a rapid detection system for known mutations is crucial. As part of this study, additional SDHI-resistant Clarireedia isolates were collected from Rutgers University research plots and in vitro sensitivity to four SDHI active ingredients was assessed. Sdh B, Sdh C, and SdhD subunits of these isolates were sequenced to reveal an additional mutation on the Sdh B subunit gene, H267R, not previously observed in Clarireedia. Cleaved amplified polymorphic sequence (CAPS) and derived CAPS molecular markers were developed to detect five mutations conferring SDHI resistance in Clarireedia isolates and validated using samples from two additional golf courses in Connecticut and Wisconsin experiencing SDHI field failure. This PCR-based molecular detection system will be useful for continued monitoring, assessment, and delay of SDHI resistance in the field.