Mycorrhizal synthesis, morpho-anatomical characterization of mycorrhizae, and evaluation of mycorrhiza-forming ability of Hydnum albidum-like species using monokaryotic and dikaryotic cultures

Unveiling the Diversity of Hydnum in the Republic of Korea with One New Species, Hydnum paucispinum

Hydnum is a genus of ectomycorrhizal fungi belonging to the Hydnaceae family. It is widely distributed across different regions of the world, including North America, Europe, and Asia; however, some of them showed disjunct distributions. In recent years, with the integration of molecular techniques, the taxonomy and classification of Hydnum have undergone several revisions and advancements. However, these changes have not yet been applied in the Republic of Korea. In this study, we conducted an integrated analysis combining the morphological and molecular analyses of 30 specimens collected over a period of approximately 10 years in the Republic of Korea. For molecular analysis, the sequence data of the internal transcribed spacer (ITS) region, the large subunit of nuclear ribosomal RNA gene (nrLSU), and a portion of translation elongation factor 1-α (TEF1) were employed as molecular markers. Through this study, we identified eight species that had previously not been reported to occur in the Republic of Korea, including one new species, Hydnum paucispinum. A taxonomic key and detailed descriptions of the eight Hydnum species are provided in this study.

Shifts of Leaf Litter-Induced Plant-Soil Feedback from Negative to Positive Driven by Ectomycorrhizal Symbiosis between Quercus ilex and Pisolithus arrhizus

Ectomycorrhizas (ECM) are a common symbiotic association between fungi and various plant species in forest ecosystems, affecting community assemblages at the landscape level. ECMs benefit host plants by increasing the surface area for nutrient uptake, defending against pathogens, and decomposing organic matter in the soil. ECM-symbiotic seedlings are also known to perform better in conspecific soils than other species unable to carry the symbiosis, in a process referred to as plant-soil feedback (PSF). In this study, we tested the effects of different leaf litter amendments on ECM and non-ECM seedlings of Quercus ilex inoculated with Pisolithus arrhizus and how they altered the litter-induced PSF. Our experiment showed that the ECM symbiont induced a shift from negative PSF to positive PSF in Q. ilex seedlings by analysing plant and root growth parameters. However, non-ECM seedlings performed better than ECM seedlings in a no-litter condition, indicating an autotoxic effect when litter is present without ECM symbionts. Conversely, ECM seedlings with litter performed better at different decomposition stages, suggesting a possible role of the symbiosis of P. arrhizus and Q. ilex in recycling autotoxic compounds released from conspecific litter, transforming them into nutrients that are transferred to the plant host.

Two new species of <i>Sistotrema</i> s.l. (<i>Cantharellales</i>) from Japan with descriptions of their ectomycorrhizae

We describe two new species of resupinate Sistotrema sensu lato (Cantharellales) collected in Japan: S. flavorhizomorphae and S. chloroporum. Both species have urniform basidia with more than four sterigmata and monomitic hyphal system, oil-rich hyphae in subiculum, which is typical for this genus. Sistotrema chloroporum is characterized by poroid hymenophore partly yellowish-green, basidia 4-6-spored, medium-sized basidiospores (4.5-6.5 × 3.5-6 µm), and broadleaf forest habitat. Sistotrema flavorhizomorphae is characterized by hydnoid-irpicoid hymenophore, bright yellowish rhizomorphs, basidia 6-8-spored, small basidiospores (3-3.5 × 2.5-3 µm), and pine forest habitat. Phylogenetic trees inferred from the fungal nrDNA ITS and LSU and the rpb2 sequences supported that both species were distinct and grouped with other ectomycorrhizal Sistotrema and Hydnum species, but their generic boundary was unclear. Mycorrhizae underneath basidiomes of both species were identified and described via molecular techniques. Mycorrhizae of S. chloroporum have similar characteristics to those of other Sistotrema s.l. and Hydnum species, i.e., S. confluens and H. repandum, whereas S. flavorhizomorphae has a distinct morpho-anatomy, for example, a distinct pseudoparenchymatous mantle. Comprehensive characterizations of basidiomes and mycorrhizae improve the taxonomic analysis of mycorrhizal species of Sistotrema s.l.

Systematic revision of Hydnum species in Japan

Hydnum (Hydnaceae, Basidiomycota) exhibits endemic species diversity in East Asia; however, few comprehensive systematic studies have been conducted to date. Here, we performed morphological, ecological, phylogenetic, and biological evaluations of the taxonomy of Hydnum species in Japan. In total, 186 Japanese Hydnum specimens were used for morphological observations. Phylogenetic trees were constructed using sequence data of nuc rDNA internal transcribed spacer ITS1-5.8S-ITS2 (ITS) region and a portion of translation elongation factor 1-α (tef1). Intra- and interspecific mating tests using 78 monokaryotic strains of 13 species did not conflict with species delimitation inferred from their ITS and tef1 phylogenetic relationships. This study provides detailed morphological descriptions of 15 rigorously identified species from Japan, nine of which are described as new: H. alboluteum, H. albopallidum, H. pinicola, H. itachiharitake, H. minospororufescens, H. orientalbidum, H. subberkeleyanum, H. tomaense, and H. tottoriense. Three species documented in this work are new to Japan: H. boreorepandum, H. mulsicolor, and H. umbilicatum. The remaining three species (H. cremeoalbum, H. minus, and H. repando-orientale), previously reported from Japan, are redescribed using data from newly collected materials. We also transferred two old species (Hericium fimbrillatum and Sarcodon nauseofoetidus) from East Asian Hydnum into other genera.

Taxonomy of the major rhizomorphic species of the "Melanopus group" within Polyporaceae in Yasuní National Park, Ecuador

Yasuní National Park in Ecuador is one of the most biodiverse places on earth. The fungi in this tropical rainforest are also diverse but have received little research attention. This research paper focuses on an important group of fungi in the family Polyporaceae and examines the genera Polyporus, Atroporus, and Neodictyopus that form aerial melanized cord-like structures called rhizomorphs. Phylogenetic analyses, macro and micromorphological descriptions of basidiomata and rhizomorphs, as well as cultural characterization were completed to better understand these ecologically important fungi. Here we describe four new species: Atroporus yasuniensis, Atroporus tagaeri, Neodictyopus sylvaticus, and Polyporus taromenane, and a new variety Polyporus leprieurii var. yasuniensis. The information presented in this study adds important new knowledge about the unusual rhizomorph producing fungi found in Yasuní National Park, Ecuador and other tropical rainforests.