Torsisporaceae fam. nov. (Pleosporales) and Four Novel Species of DSEs from Heavy Metal-Contaminated Regions in Northern China

Dark septate endophytes (DSEs) are a phylogenetically diverse group of root-associated fungi, many of which remain sterile in culture, complicating their identification using conventional morphological criteria. In this study, we examined five DSE isolates obtained from Phragmites australis and Setaria viridis growing in heavy metal-contaminated habitats in northern China. Multilocus phylogenetic analyses, together with cultural and morphological observations, supported the recognition of four novel species. Torsispora arcuata and T. sterilis represent a new genus, Torsispora, and a new family, Torsisporaceae, within Pleosporales (Dothideomycetes), whereas Zopfiella setaria and Cercophora phragmita are assigned to Sordariales (Sordariomycetes). We also documented intraradical fungal structures formed by these isolates in wheat and maize roots, providing additional phenotypic information for future comparative studies. Our findings contribute to the taxonomy of sterile root-associated fungi and reveal previously undocumented DSE diversity in stressful environments.