Phylogenetic and Taxonomic Study of Asteroconium saccardoi: A Fungal Species with Aster-shaped Spores Infecting Machilus thunbergii

Abstract

Small galls and white blisters with cup-like fungal structures were observed on the leaves of Machilus thunbergii (Lauraceae), a tree species native to East Asia. Based on its distinctive symptoms and aster-shaped spores, the causal agent was identified as Asteroconium saccardoi. Despite its unique characteristics, the genus Asteroconium remains taxonomically unresolved (incertae sedis) within the phylum Ascomycota due to the absence of both sequence data and available culture. The present study successfully obtained ITS and LSU rDNA sequences from its fresh spore masses formed on M. thunbergii. Phylogenetic analysis revealed that A. saccardoi belongs to the order Exobasidiales under Basidiomycota. Detailed morphological characteristics of basidia and basidiospores were documented, providing comprehensive insights into the taxonomy and phylogeny of Asteroconium within Exobasidiales.