Global Distributions of Clarireedia Species and Their In Vitro Sensitivity Profiles to Fungicides

Abstract

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.

A one‐step multiplex PCR assay for the detection and differentiation of four species of Clarireedia causing dollar spot on turfgrass

“…In a previous study, we found that multiple species of Clarireedia co-existed in a few golf courses, 7,10 which was further confirmed in the present study by the multiplex PCR method. For example, C. paspali, C. monteithiana and C. hainanense were detected in ML and SGL, and C. paspali and C. hainanense were detected in SZBD in both studies (Fig.…”

“…5,7 Studies have revealed that multiple species in the genus Clarireedia co-exist on the same hosts or at same locales, which might complicate the management of DS disease. 5,7,9,10 Because morphological differences were observed among different species of Clarireedia, including pigment accumulation, oxalic acid production, pathogenicity and fungicide sensitivity, 7,10 it is indicated that different management strategies should be used to control DS disease caused by different species. Therefore, it is necessary to monitor the distributions and prevalence of different species in Clarireedia, especially at those locales where more than two species co-exist.…”

“…A quantitative polymerase chain reaction (qPCR method) also was developed for general diagnosis of the fungal species causing DS, 13 yet this method cannot distinguish between the different species of Clarireedia. Because fungicide sensitivity or other phenotypes can vary by different species of Clarireedia, 7,10 it is urgent to identify the DS pathogens to the species level, as well as differentiate between the multiple species causing DS, which is not possible with the current CAPS method or the qPCR approach developed.…”

“…To date, four species of Clarireedia (C. jacksonii, C. monteithiana, C. paspali and C. hainanense) have been identified as the causal agents of DS in China. 5,7,10 To develop a PCR-based method to detect and differentiate between the four species, we sequenced the genomes of isolates representing the four species and incorporated the published genomes of seven isolates to perform the comparative genomics analyses. Species-specific genes were identified and species-specific primers (based on these unique genes) were designed and tested.…”

“…4,9 Clarireedia jacksonii and C. monteithiana are globally distributed, and also widely distributed in large areas of China. 9,10 Clarireedia paspali and C. hainanense, described in 2019 and 2022, respectively, are widely distributed in eastern and southern regions of China. 5,7 Studies have revealed that multiple species in the genus Clarireedia co-exist on the same hosts or at same locales, which might complicate the management of DS disease.…”