Morphological and multilocus phylogenetic analysis of Sirococcus (Diaporthales, Gnomoniaceae) on woody hosts from Fujian, Shandong, and Yunnan, China: Two new species and two new records

Sirococcus ( Diaporthales , Gnomoniaceae ) has recently been recircumscribed based on multilocus phylogenetic and morphological evidence, with all species formerly placed in Gnomoniopsis transferred to Sirococcus under the principle of nomenclatural priority. In this study, we investigated the species diversity of Sirococcus associated with native woody hosts from Fujian, Shandong, and Yunnan provinces, China. A total of six isolates were recovered from leaf samples of plants belonging to Fagaceae , Lauraceae , and Theaceae . Phylogenetic analysis based on concatenated ITS, tef1 , and tub2 sequence datasets resolved these isolates into four Sirococcus species: two new species ( S. euryicola sp. nov . and S. linderae sp. nov .), one new host record for S. fujianensis , and one new geographical record for S. mengyinensis . We provide detailed morphological descriptions, photographic illustrations, and multilocus sequence data for all four species, along with compiled host and distribution notes, and discuss their phylogenetic affinities and taxonomic implications within the genus. Our findings substantially expand the known species diversity, host range, and geographical distribution of Sirococcus in China, and highlight the underexplored diversity of this genus on non- Fagaceae woody hosts.