Three Ophiostomatalean Fungi Associated with Bark Beetles from Pinus thunbergii Infested by Bursaphelenchus xylophilus in Laoshan Mountain (Shandong, China)

Pine wilt disease (PWD) is a devastating disease that occurs worldwide and affects conifers infested by the pine wood nematode (PWN, Bursaphelenchus xylophilus). PWD has caused serious economic and ecological losses in China. The mechanism of disease outbreak is complex, with the associated fungi, specifically ophiostomatoid fungi, thought to play an essential role. However, few ophiostomatoid fungal associates of PWD have been accurately identified. In the present study, we isolated fungi from bark beetles collected from Pinus thunbergii infested by the pine wood nematode on Laoshan Mountain, Shandong province. Three ophiostomatalean fungi were identified and assigned to Graphilbum and Ophiostoma based on phylogenetic analyses and comparison of morphological and cultural features, namely Gra. laoshanense sp. nov., Gra. translucens, and O. ips. This study increases the understanding of the diversity of ophiostomatoid fungi associated with PWD and provides resources for parsing this complex disease.