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Xylariomycetidae comprises extremely diverse taxa that are widespread on decaying wood worldwide. An investigation of the diversity of microfungi on oil tree plantations in Sichuan Province was conducted during 2020–2021. Twelve saprobic taxa representing five species were identified as members of Amphisphaeriales and Xylariales through morphological comparisons. Phylogenetic analyses of combined ITS, LSU, rpb2, tub2 and tef1 sequence data indicated a distinct clade formed by three strains within Xylariomycetidae, unrelated to any currently recognized families. Thus, a novel anthostomella-like genus, Bicellulospora, is proposed and treated as Xylariales genera incertae sedis. Bicellulospora is characterized by dark brown to black, immersed, subglobose ascomata with a clypeus, cylindrical asci, and hyaline to yellowish brown, inequilaterally ellipsoidal ascospores with a large upper cell and a dwarf lower cell. Two new species of Amphisphaeria, namely A. oleae and A. verniciae, are introduced based on multi-gene phylogenetic analyses (ITS, LSU, rpb2 and tub2) coupled with morphological characteristics. Amphisphaeria micheliae and Endocalyx ptychospermatis are reported as new host records.

Pestalotiod fungi are associated with a wide variety of plants worldwide and occur as endophytes, pathogens, and saprobes. The present study provides an updated phylogeny for genera Neopestalotiopsis, Pestalotiopsis, and Seiridium using fresh collections from woody oil plants (Camellia oleifera, Olea europaea, Paeonia suffruticosa, Sapium sebiferum, and Vernicia fordii) in Sichuan Province, China. We coupled morphology and combined sequence data analyses of ITS, tub2, and tef1-α for Neopestalotiopsis and Pestalotiopsis, with ITS, LSU, tub2, tef1-α, and rpb2 for Seiridium. Three novel species of Neopestalotiopsis (N. mianyangensis, N. paeonia-suffruticosa, N. terricola) and three of Seiridium (S. guangyuanum, S. vernicola, S. oleae), were found. Three other species, Pestalotiopsis kenyana, Seiridium ceratosporum, and S. rosarum were identified and reported as new records. All isolated species are fully described and illustrated. Additionally, the sexual morph of Pestalotiopsis kenyana is described for the first time. Pathogenicity tests revealed that Neopestalotiopsis mianyangensis, N. paeonia-suffruticosa, N. terricola, Pestalotiopsis kenyana, Seiridium guangyuanum, S. vernicola, and S. oleae are pathogenic on detached olive leaves.

Pleurotremataceae species are saprobes on decaying wood in terrestrial, mangrove, and freshwater habitats. The generic boundary of the family has traditionally been based on morphology. All genera of Pleurotremataceae have a high degree of morphological overlap, of which the generic circumscription of Melomastia and Dyfrolomyces has not been well resolved. Thus, the delimitation of genera has always been challenging. Melomastia traditionally differs from Dyfrolomyces in having 2-septate, oblong, with obtuse-ends ascospores. These main characteristics have been used to distinguish Melomastia from Dyfrolomyces for a long time. However, the above characteristics sometimes overlap among Dyfrolomyces and Melomastia species. Based on the morphology and multigene phylogeny with newly obtained data, we synonymized Dyfrolomyces under Melomastia following up-to-date results. Four novel species (i.e., Melomastia fusispora, M. oleae, M. sichuanensis and M. winteri) collected from the dead branches of Olea europaea L. in Chengdu Olive Base, Sichuan Province in China are introduced based on detailed morphological characterization and phylogenetic analyses of sequences based on nuclear ribosomal (LSU and SSU) and protein-coding gene (tef1-α). The 11 new combinations proposed are Melomastia aquatica (=Dyfrolomyces aquaticus), M. chromolaenae (=D. chromolaenae), M. distoseptata (=D. distoseptatus), M. mangrovei (=D. mangrovei), M. marinospora (=D. marinosporus), M. neothailandica (=D. neothailandicus), M. phetchaburiensis (=D. phetchaburiensis), M. sinensis (=D. sinensis), M. thailandica (=D. thailandica), M. thamplaensis (=D. thamplaensis) and M. tiomanensis (=D. tiomanensis).

Distoseptispora is one of the sporidesmium-like taxa with great variation in asexual morphology and delineation of species. Phylogenetic analyses of four gene regions LSU, ITS, TEF1α, and RPB2 revealed the placement of several sporidesmium-like species in Distoseptispora (Distoseptisporaceae, Distoseptisporales, Sordariomycetes), collected on submerged decaying twigs from streams in China and Thailand. Based on morphological examination and molecular DNA data, six new species, Distoseptispora amniculi, D. atroviridis, D. effusa, D. fusiformis, D. hyalina, and D. verrucosa, are proposed. Among them, D. hyalina is the first sexual morph confirmed in the genus. A new geographical record is reported for D. lignicola in China. Conidial length proved to be of less taxonomic significance for some Distoseptispora species, whereas the type of conidial septa is informative at species level.