The polyphasic approach reveals two new species and two new records of Nigrospora (Apiosporaceae, Amphisphaeriales) associated with Aquilaria sinensis from China

This study isolated endophytic fungi of the genus Nigrospora from Aquilaria sinensis (Chinese agarwood) in Guangxi, China. Through rigorous morphological comparisons and molecular phylogenetic analyses, we have identified two new species (N. guangxiensis and N. pubeiensis) and two new host-recorded species (N. oryzae and N. camelliae-sinensis). The morphological analysis revealed that the new species align with the genus-level definition of Nigrospora in colony morphology, conidiophores, and conidial characteristics. However, they were distinguished from known species by finer features such as conidial dimensions and conidiogenous structures. For instance, conidiophores in Nigrospora are typically differentiated from hyphae, characterized by dark pigmentation, which is consistent with broader taxonomic descriptions. Molecular phylogeny, based on concatenated datasets of the ITS, TEF1-α, and TUB2 loci, showed that N. pubeiensis is most closely related to N. chinensis, while N. guangxiensis forms a distinct basal clade relative to these two groups. Additionally, N. oryzae and N. camelliae-sinensis were first recorded on A. sinensis, expanding their known host ranges. The study enriches the taxonomic framework of Nigrospora by providing novel data from China, emphasizing the importance of integrating morphological and molecular approaches in fungal systematics. It also underscores the ecological diversity of fungal-host interactions in agarwood-producing trees, a topic explored in related research on endophytic fungi. These findings have significant implications for our understanding of fungal diversity and their ecological roles in agarwood-producing trees, and they pave the way for further research in this area.