Hot desert regions are undoubtedly challenging to fungal survival on the Arabian Peninsula. Fungi are, however, recognized as the most stress-resistant organisms among all eukaryotes, which could be a result of the rapid evolution of distinct species. Our current understanding of these microorganisms is derived from studies examining only a fraction of the overall fungal diversity. Therefore, further studies are needed to understand the diversity of fungi in desert regions. This paper highlights the taxonomy of several unusual fungal genera collected in a range of aquatic and terrestrial environments in Oman. These taxa were identified based on phylogenetic analyses of nuclear ribosomal DNA (rDNA) (LSU, SSU and ITS) and protein-coding genes (TEF, RPB2 and TUB), plus morphological comparisons. Phylogenetic analyses, including the presently recognized genera in Patellariales resulted in splitting the order into four clades in Dothideomycetes. The new family Holmiellaceae and new order Holmiellales are introduced to include Holmiella. Species of Homortomycetaceae form a well-supported and distinct clade and raise it to Homortomycetales ordonovus. Omania (Halojulellaceae), Desertiserpentica (Lophiostomataceae) and Montanitestudina (Testudinaceae) are described as novel genera in Dothideomycetes. A synnematous hyphomycete with basidiomycetous affinity (Corticiales) was also identified and described as Basidiodesertica. Additionally, an asexual morph was observed for Holmiellajunipericola; Patellariaquercus is synonymized under P.atrata, and seven new species are described.
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