2026 年 20 巻 p. 9-20
The phylogenetic and functional diversity of ericoid mycorrhizal (ErM) fungi remains poorly understood, particularly in lower latitudes. To contribute to the understanding of the phylogenetic diversity and ecological roles of fungal partners of ErM plants, we isolated fungi from hair roots of Vaccinium wrightii on Amami-Oshima Island, which is in a subtropical region of Japan. We also conducted an in vitro fungal inoculation experiment using nine isolated strains, including Oidiodendron sp., Cyanotrama gypsea, Pezicula ericae, P. radicicola, three unidentified Pezicula spp., Glutinomyces sp., and Dothideomycetes sp.1. Most of the isolated fungi, such as Oidiodendron and Pezicula species, were genetically closely related to or conspecific with taxa commonly found in higher latitudes of the Northern Hemisphere. However, no DNA sequences identical to those of the Glutinomyces sp. were found in public genetic databases. Despite the frequent isolation of Pezicula spp., five tested strains seemed to be pathogenic, causing seedling mortality. The remaining four strains, belonging to other taxa, did not significantly affect host growth. These strains formed intracellular hyphal coils or net-like structures within rhizodermal cells. Notably, Glutinomyces sp. exhibited root colonization comparable to Oidiodendron sp., forming dense, frequent rhizodermal hyphal coils characteristic of ErM fungi. Additionally, C. gypsea and Dothideomycetes sp.1 formed relatively sparse intracellular coil-like structures in the rhizodermis. Our culture-based study provides new insights into the diversity of fungal partners of ErM plants in a Japanese subtropical area.
