Published papers

Exobasidium sakataniense Hirata (1981:62) was described as a new species, but no viable culture has been available. In this study, a culture was isolated from new specimens collected from dry, scab-like spots on old lesions on the leaves and from blight on the lammas shoots of Symplocos theophrastifolia Siebold & Zuccarini (1846:134) on October 20 and 21, 2023 in Kaeda and Inohae valleys, Miyazaki Prefecture, Japan, which are new locations for the records of E. sakataniense, and its phylogenetic position was determined. The analysis confirmed that E. sakataniense belongs to a group of Exobasidium species pathogenic to Symplocos and is closely related to E. siroboe.

Thirty-three species of rust fungi (Pucciniales) were collected in the Imperial Palace Garden during the survey conducted from 2021 to 2023. Of these, 12 species are newly recorded compared with the previous surveys conducted in 1997–1999 and 2012–2013, which recorded 35 and 29 species, respectively. Seventeen species were confirmed to colonize and survive in the garden, whereas nine species are presumed to have disappeared. The species composition has also changed compared with the earlier surveys. This floristic change in rust fungi is suspected to be a result of continuous changes in environmental conditions and plant growth in the garden.

A total of 42 species of mushrooms (Ascomycota and Basidiomycota) were collected in the Fukiage Gardens of the Imperial Palace, Tokyo, and identified to species level during 2021–2022. Approximately 40% of these species have not previously been reported from the Gardens. The occurrence of certain species, such as Trichoderma cornu-damae and Favolaschia gelatina, may be attributable to their recent range expansions.

The genus Tricholomopsis comprises saprotrophic fungi that grow on dead wood. Although six species of Tricholomopsis have been reported in Japan, no phylogenetic analyses based on genomic DNA sequences have been conducted to date. We performed morphological observations and molecular phylogenetic analyses using the internal transcribed spacer (ITS) region of rDNA, the large subunit(LSU), and the transcription elongation factor 1-α (tef1) gene. A total of eighteen Tricholomopsis basidiocarps were collected from Niigata, Ishikawa, Nagano, Ibaraki, and Hokkaido prefectures. Six of Tricholomopsis species were detected, including T. rutilans s. str. and T. decora, along with one previously undescribed species. Three known species were also identified as T. sulphreoides, T. mitirubicunda, and T. depressa. We newly reported three of Tricholomopsis as new to Japan. Our results suggest that the distribution of T. rutilans s. str. in Japan is likely restricted to subalpine to alpine zones, while T. mitirubicunda is widely distributed in lowland areas. We clarified the relationship between T. mitirubicunda and T. rutilans s. str. and also emended the Japanese names of both species and description of Japanese T. rutilans s. str.

Three willow rust fungi, Melampsora babylonicae, M. coleosporioides, and M. ferrinii, are morphologically similar and share comparable host associations. Morphological and phylogenetic analyses revealed that M. coleosporioides and M. ferrinii are taxonomically indistinguishable, whereas M. babylonicae is phylogenetically distinct and is therefore provisionally treated as a separate species. As a result, M. ferrinii is synonymized with M. coleosporioides and the description of M. coleosporioides is accordingly emended. The life cycle, host plant range, and geographic distribution of this rust fungus are described and discussed based on existing literature.

The present study reports the identification of two newly recorded species of the genus Rickenella, R. indica and R. mellea, in Japan. Small (1-3 mm wide), parabolic to convex, and never becoming applanate or infundibuliform pileus are characteristic features of R. indica. Rickenella mellea is a subalpine species and it is characterized by its honey-colored, yellowish-beige to reddish yellow-pileus and stipe. Molecular phylogenetic analysis using the ITS region and the LSU of the nuclear rDNA supported their identification based on morphological observations. A key to the known Japanese species of Rickenella and morphologically similar taxa is provided.

The discovery of novel natural products through the exploration of distinctmicroorganisms is crucial for advancing drug discovery research. In this study, we focus on a unique environmental resource, microbial masses known as “Tengu-no-Mugimeshi.” From the culture broth of Lecanicillium aphanocladii FKI-9593, isolated from Tengu-no-Mugimeshi collected at Mount Kurohime, Nagano Prefecture, Japan, we report the isolation of two novel tetrapeptides, tengupeptins A (1) and B (2), as well as the known compound oosporein. Structural analysis revealed that tengupeptins are composed of four amino acids: L-glutamic acid for 1 (or L-pyroglutamic acid for 2), (Z)-α,β-didehydro tryptophan (ΔZTrp), (Z)-α,β-didehydro-phenylalanine (ΔZPhe), and L-aspartic acid. Notably, dehydroamino acids containing an aromatic moiety conjugated with a double bond connected via two or more consecutive linkages are rare in natural products, and the ΔZTrp-ΔZPhe fragment represents the first example. The isolation of secondary metabolites from filamentous fungi inhabiting unique environments, such as Tengu-no-Mugimeshi, is anticipated to offer significant potential for future research.

Caeoma mori (≡ Aecidium mori), known as the mulberry rust which is an anamorphic rust fungus forming only aecidioid uredinia, were found on Morus alba in Ibaraki and Saitama Prefectures, Japan. Molecular phylogenetic analyses using the combined dataset of sequences from 28S and 18S of the nuclear ribosomal RNA gene and Cytochrome-c-oxidase subunit 3 of the mitochondrial DNA revealed that this anamorphic rust fungus was a member of the clade composed of the genus Gymnosporangium. Therefore, a new combination, Gymnosporangium mori is proposed for this species. Additionally, a new combination, G. brucense for Roestelia brucensis is proposed by phylogenetic evidence.