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Over the past two decades, numerous novel species have been identified within Dictyosporiaceae, primarily in Dictyocheirospora and Dictyosporium. A recent monograph has revealed that these two genera exhibit a distinct preference for freshwater habitats, particularly in southern China. However, further investigation into the distribution and diversity of the two genera in Guangdong and Guizhou Provinces remains insufficient. In this study, we conducted an analysis of four intriguing cheiroid hyphomycetes collected from flowing rivers in these two regions. Through morphological and phylogenetic analyses incorporating combined LSU, SSU, ITS, and tef1-α sequence data, we have identified them as a novel species in Dictyocheirospora (Dictyoc. submersa sp. nov.), two novel species in Dictyosporium (Dictyos. guangdongense sp. nov. and Dictyos. variabilisporum sp. nov.), and one previously documented species (Dictyos. digitatum). Specifically, the identification of Dictyos. guangdongense is primarily based on its distinct morphology, characterized by complanate, cheiroid, and brown to dark brown conidia, with a hyaline, short, and atrophied appendage arising from the apical cell of the outer row. In addition, the morphological distinctions between Dictyocheirospora and Dictyosporium are further clarified based on our new data. This study also highlights a few phylogenetic matters regarding Dictyosporiaceae.

Pogostemon cablin is one of the well-known Southern Chinese medicinal plants with detoxification, anti-bacterial, anti-inflammatory, and other pharmacological functions. Identification and characterization of phytopathogens on P. cablin are of great significance for the prevention and control of diseases. From spring to summer of 2019 and 2020, a leaf spot disease on Pogostemon cablin was observed in Guangdong Province, South China. The pathogen was isolated and identified based on both morphological and DNA molecular approaches. The molecular identification was conducted using multi-gene sequence analysis of large subunit (LSU), the nuclear ribosomal internal transcribed spacer (ITS), beta-tubulin (β-tubulin), and RNA polymerase II (rpb2) genes. The causal organism was identified as Stagonosporopsis pogostemonis, a novel fungal species. Pathogenicity of Stagonosporopsis pogostemonis on P. cablin was fulfilled via confining the Koch’s postulates, causing leaf spots and stem blight disease. This is the first report of leaf spot diseases on P. cablin caused by Stagonosporopsis species worldwide.