Morphological and Molecular Characterization of a New Section and Two New Species of Alternaria from Iran

Alternaria is a large genus of fungi comprising approximately 400 species, currently classified into 29 sections. These fungi exhibit a cosmopolitan distribution, thriving in both natural and human-impacted environments with saprophytic, endophytic, and parasitic lifestyles. As part of our ongoing studies on fungi associated with wetland plants in the families Cyperaceae and Juncaceae across various regions of Iran, we isolated 21 fungal strains displaying morphological traits of Alternaria. Multigene phylogenetic analysis and morphological examination of eight selected strains confirmed their placement within Alternaria with strong support. These isolates formed a basal clade distinct from the 29 previously recognized sections and six monotypic lineages, leading to the establishment of a new section, Alternaria section Iraniana, to accommodate them. Furthermore, two monophyletic lineages within this section were identified, representing two new species, A. avrinica and A. iraniana, which are described and illustrated in this study. The new section is distinguished by long, semi-macronematous to macronematous conidiophores with multiple geniculate and sympodial proliferations, as well as solitary, non-beaked conidia that have only transverse eu-septa to pseudo-septa. The newly described species are differentiated based on conidiophore and conidial characteristics and nucleotide sequence comparisons of genomic regions. These results contribute to a better understanding of the distribution and host range of Alternaria species, while highlighting the importance of ongoing research into fungal taxonomy and biodiversity in Iran, a region rich in potential for the discovery of new fungal species.