Diversity and community structure of ectomycorrhizal fungi in Pinus thunbergii coastal forests in the eastern region of Korea

Plant-Microbiota Interactions in Abiotic Stress Environments

Abiotic stress adversely affects cellular homeostasis and ultimately impairs plant growth, posing a serious threat to agriculture. Climate change modeling predicts increasing occurrences of abiotic stresses such as drought and extreme temperature, resulting in decreasing the yields of major crops such as rice, wheat, and maize, which endangers food security for human populations. Plants are associated with diverse and taxonomically structured microbial communities that are called the plant microbiota. Plant microbiota often assist plant growth and abiotic stress tolerance by providing water and nutrients to plants and modulating plant metabolism and physiology and, thus, offer the potential to increase crop production under abiotic stress. In this review, we summarize recent progress on how abiotic stress affects plants, microbiota, plant-microbe interactions, and microbe-microbe interactions, and how microbes affect plant metabolism and physiology under abiotic stress conditions, with a focus on drought, salt, and temperature stress. We also discuss important steps to utilize plant microbiota in agriculture under abiotic stress.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Effect of ectomycorrhizal fungal species on population growth and food preference of a fungivorous nematode

Fungivorous nematodes can use ectomycorrhizal (ECM) fungi as food resources in forest soils, and they may establish close predator-prey relationships in forest ecosystems. However, the effect of ECM fungal species on the growth of fungivorous nematodes is poorly studied. To identify fungivorous nematode propagation and preference for ECM fungi, we investigated the in vitro population growth and food attraction of the fungivorous nematode Aphelenchoides sp. on media with four ECM fungal species: Cenococcum geophilum, Pisolithus tinctorius, Rhizopogon roseolus and Suillus granulatus. Individual nematodes were fed on hyphae of all four ECM fungal species grown on modified Melin-Norkrans agar media. Nematode numbers were significantly lower on P. tinctorius than on all other fungal species. The other three species produced similar population growth rates, with S. granulatus producing the greatest number of nematodes at 2, 3 and 4 weeks and C. geophilum and R. roseolus producing the largest number after 8 weeks. In the histogram for nematode length classes, a unimodal pattern was fitted for P. tinctorius and R. roseolus, but a bimodal pattern was fitted for C. geophilum and S. granulatus by the Silverman test. The attraction of nematodes to S. granulatus was significantly higher than that to other ECM fungi. Our findings suggest that the propagation and body size of nematodes are ECM fungal species dependent. Predator-prey relationships between fungivorous nematodes and ECM fungi may accelerate nutrient cycles in forest ecosystems.

Metagenomic Analysis of Bacterial and Fungal Communities Inhabiting Shiro Dominant Soils of Two Production Regions of Tricholoma Matsutake S. Ito & S. Imai in Korea

Tricholoma matsutake is an ectomycorrhizal fungus that has obligate symbiotic relationships with Pinus densiflora. Its fruiting body has a distinctive flavor and is traded at a high price. Thus, it has been a significant source of income for rural communities in Korea. We hypothesized that biotic factors considerably influence the formation of the T. matsutake mushroom, and the soils producing T. matsutake share similar microbial characteristics. Therefore, the present study aimed to detect the specific fungal and bacterial groups in T. matsutake production soils (shiro+) and nonproduction soils (shiro−) of the Bonghwa and Yanyang regions via next-generation sequencing. In a total of 15 phyla, 36 classes, 234 genera of bacteria, six phyla, 29 classes, and 164 genera of fungi were detected from four samples at both sites. The species diversity of shiro+ soils was lower than the shiro− samples in both the fungal and bacterial groups. In addition, we did not find high similarities in the microbial communities between the shiro+ soils of the two regions. However, in the resulting differences between the fungal communities categorized by their trophic assembly, we found a distinguishable compositional pattern in the fungal communities from the shiro+ soils and the shiro− soils of the two sites. Thus, the similarity among the microbial communities in the forest soils may be due to the fact that the microbial communities in the T. matsutake dominant soils are closely associated with biotic factors and abiotic factors such as soil properties.

Diversity and community structure of ectomycorrhizal fungi in Pinus thunbergii coastal forests bordering the Yellow Sea of China

Ectomycorrhizas play a fundamental role in the function of forest ecosystems, being essential for plant nutrition absorption and soil quality. Many afforestation and reforestation programmes have begun to recover and maintain coastal forests in China, using pine species including Pinus thunbergii. We investigated the ectomycorrhizal colonization status of P. thunbergii in coastal pine forests of the Yellow Sea of China. We identified a total of 53 ectomycorrhizal fungal species in 74 soil samples collected from three sites and found that Thelephoraceae (10 spp.) and Russulaceae (8 spp.) were the most species-rich ectomycorrhizal fungal lineages. Russula sp. 1 was the most abundant species, accounting for 15.3% of the total ectomycorrhizal tips identified. Most of the remaining species were rare. At this small scale, host identity had no significant effect on the ectomycorrhizal fungal community composition (A = 0.036, P = 0.258), but sampling sites did (A = 0.135, P = 0.041). In addition, Na⁺ and K⁺ content and soil pH had significant effects on the ectomycorrhizal fungal community. The ectomycorrhizal fungal community associated with different host plants will become an important new direction for research, as ectomycorrhiza may have the potential to improve host capacity to establish in salt-stressed environments. This will provide a theoretical basis and technical support for saline soil reforestation and rehabilitation using pine species with compatible, native ectomycorrhizal fungi in Yellow Sea coastal areas.

Taxonomic revision of Russula subsection Amoeninae from South Korea

RussulasubsectionAmoeninae is morphologically defined by a dry velvety pileus surface, a complete absence of cystidia with heteromorphous contents in all tissues, and spores without amyloid suprahilar spot. Thirty-four species within subsection Amoeninae have been published worldwide. Although most Russula species in South Korea have been assigned European or North American names, recent molecular studies have shown that Russula species from different continents are not conspecific. Therefore, the present study aims to: 1) define which species of RussulasubsectionAmoeninae occur on each continent using molecular phylogenetic analyses; 2) revise the taxonomy of Korean Amoeninae. The phylogenetic analyses using the internal transcribed spacer (ITS) and multilocus sequences showed that subsection Amoeninae is monophyletic within subgenus HeterophyllidiaesectionHeterophyllae. A total of 21 RussulasubsectionAmoeninae species were confirmed from Asia, Australia, Europe, North America, and Central America, and species from different continents formed separate clades. Three species were recognized from South Korea and were clearly separated from the European and North American species. These species are R.bella, also reported from Japan, a new species described herein, Russulaorientipurpurea, and a new species undescribed due to insufficient material.

Effect of Litter Quality on Needle Decomposition for Four Pine Species in Korea

Litter decomposition involves multiple complex processes, including interactions between the physicochemical characteristics of litter species and various environmental factors. We selected four representative pine species in South Korea (Pinus densiflora Siebold & Zucc., Pinus thunbergii Parl., Pinus koraiensis Siebold & Zucc., and Pinus rigida Miller) to investigate the decay rate and effects of the physicochemical properties on decomposition. Needle litters were incubated in microcosms at 23 °C for 280 days and retrieved four times in about 70-day intervals. The mass loss showed significant differences among the species and was higher in the order of P. densiflora (30.5%), P. koraiensis (27.8%), P. rigida (26.5%), and P. thunbergii (23.6%). The needle litter decomposition showed a negative relationship with the initial surface area, volume, density, cellulose content, and lignin/nitrogen of the litter, and a positive relationship with the initial specific leaf area (SLA), surface-area-to-volume ratio (SA/V), and water- and ethanol-soluble substances. The decomposition rate was highly affected by the physical properties of litter when compared with the initial chemical litter quality, and it was strongly influenced by SLA and SA/V. Accordingly, the physical properties of pine needle litter, especially SLA and SA/V, may be the key factors, and they could be used as predictive indices for the decomposition rate of pine tree litters.

May T, Patrik Cangren, Henrik Nilsson R, Larsson E. Solving the taxonomic identity of Pseudotomentellatristis s.l. (Thelephorales, Basidiomycota) - a multi-gene phylogeny and taxonomic review, integrating ecological and geographical data

P.tristis is an ectomycorrhizal, corticioid fungus whose name is frequently assigned to collections of basidiomata as well as root tip and soil samples from a wide range of habitats and hosts across the northern hemisphere. Despite this, its identity is unclear; eight heterotypic taxa have in major reviews of the species been considered synonymous with or morphologically similar to P.tristis, but no sequence data from type specimens have been available. With the aim to clarify the taxonomy, systematics, morphology, ecology and geographical distribution of P.tristis and its morphologically similar species, we studied their type specimens as well as 147 basidiomata collections of mostly North European material. We used gene trees generated in BEAST 2 and PhyML and species trees estimated in STACEY and ASTRAL to delimit species based on the ITS, LSU, Tef1α and mtSSU regions. We enriched our sampling with environmental ITS sequences from the UNITE database. We found the P.tristis group to contain 13 molecularly and morphologically distinct species. Three of these, P.tristis, P.umbrina and P.atrofusca, are already known to science, while ten species are here described as new: P.sciastra sp. nov., P.tristoides sp. nov., P.umbrinascens sp. nov., P.pinophila sp. nov., P.alnophila sp. nov., P.alobata sp. nov., P.pluriloba sp. nov., P.abundiloba sp. nov., P.rotundispora sp. nov. and P.media sp. nov. We discovered P.rhizopunctata and P.atrofusca to form a sister clade to all other species in P.tristis s.l. These two species, unlike all other species in the P.tristis complex, are dimitic. In this study, we designate epitypes for P.tristis, P.umbrina and Hypochnopsisfuscata and lectotypes for Auriculariaphylacteris and Thelephorabiennis. We show that the holotype of Hypochnussitnensis and the lectotype of Hypochnopsisfuscata are conspecific with P.tristis, but in the absence of molecular information we regard Pseudotomentellalongisterigmata and Hypochnusrhacodium as doubtful taxa due to their aberrant morphology. We confirm A.phylacteris, Tomentellabiennis and Septobasidiumarachnoideum as excluded taxa, since their morphology clearly show that they belong to other genera. A key to the species of the P.tristis group is provided. We found P.umbrina to be a common species with a wide, Holarctic distribution, forming ectomycorrhiza with a large number of host species in habitats ranging from tropical forests to the Arctic tundra. The other species in the P.tristis group were found to be less common and have narrower ecological niches.

The Control of Fusarium Root Rot and Development of Coastal Pine (Pinus thunbergii Parl.) Seedlings in a Container Nursery by Use of Bacillus licheniformis MH48

This study investigated the control of Fusarium root rot and development of coastal pine (Pinus thunbergii) seedlings in a container nursery by using Bacillus licheniformis MH48. High-quality seedlings without infectious diseases cause vigorous growth. Fusarium root rot caused by Fusarium oxysporum is responsible for serious damage to coastal pine seedlings in nurseries. B. licheniformis MH48 produced enzymes that degraded the fungal cell walls, such as chitinase and β-1,3-glucanase. These lytic enzymes exhibited destructive activity toward F. oxysporum hyphae, which were found to play key roles in the suppression of root rot. In addition, B. licheniformis MH48 increased the nitrogen and phosphorus in soils via fixed atmospheric nitrogen and solubilized inorganic phosphate. B. licheniformis MH48 produced the phytohormone auxin, which stimulated seedling root development, resulting in increased nutrient uptake in seedlings. Both the bacterial inoculation and the chemical fertilizer treatments significantly increased seedling growth and biomass, and the bacterial inoculation had a greater effect on seedling development. Based on the results from this study, B. licheniformis MH48 showed potential as a biological agent against Fusarium root rot and as a promoter of growth and development of Pinus thunbergii seedlings.

Isolation source matters: sclerotia and ectomycorrhizal roots provide different views of genetic diversity in Cenococcum geophilum

Cenococcum geophilum forms sclerotia and ectomycorrhizas with host plants in forest soils. We demonstrated the differences in genetic diversity of C. geophilum between cultured isolates from sclerotia and those from ectomycorrhizal roots in the same 73 soil samples based on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene sequences and newly developed microsatellite markers. Based on GAPDH sequences, 759 cultured isolates (553 from sclerotia and 206 from ectomycorrhizas) were classified into 107 "genotypes" with sequence variation of up to 8.6%. The total number of GAPDH genotypes per soil sample ranged from 1 to 9, but genotypes that were shared between sclerotia and ectomycorrhizas were uncommon (0-3 per soil sample). More than 50% of GAPDH genotypes were unique to one source in most soil samples. Unique GAPDH genotypes were detected from either scleotia or ectomycorrhizal roots in most of the soil samples. Multilocus analysis using nine microsatellite markers provided additional resolution to differentiate fungal individuals and supported the results of GAPDH genotyping. The results indicated that sampling both sclerotia and ectomycorrhizal roots maximizes the detection of diversity at the soil core scale. On the other hand, when all isolates were viewed together, 82 GAPDH genotypes were unique to sclerotia whereas only 6 GAPDH genotypes were unique to ectomycorrhizas. Rarefaction analysis indicated that GAPDH genotypic diversity is significantly higher in sclerotia than ectomycorrhizal roots and the diversity within sclerotia is nearly the same as that of both sclerotia and ectomycorrhizas together. These findings suggest that sampling sclerotia alone is likely to detect the majority of GAPDH genotypes in Cenococcum at the regional scale. When deciding whether to sample sclerotia, ectomycorrhizas, or both types of tissues from Cenococcum, it is critical to consider the spatial scale and also the main questions and hypotheses of the study.

Revisiting phylogenetic diversity and cryptic species of Cenococcum geophilum sensu lato

The fungus Cenococcum geophilum Fr. (Dothideomycetes, Ascomycota) is one of the most common ectomycorrhizal fungi in boreal to temperate regions. A series of molecular studies has demonstrated that C. geophilum is monophyletic but a heterogeneous species or a species complex. Here, we revisit the phylogenetic diversity of C. geophilum sensu lato from a regional to intercontinental scale by using new data from Florida (USA) along with existing data in GenBank from Japan, Europe, and North America. The combination of internal transcribed spacer (ITS) ribosomal DNA and the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene resolved six well-supported lineages (87-100 % bootstrap values) that are closely related to each other and a seventh lineage that is phylogenetically distinct. A multi-locus analysis (small subunit (SSU), large subunit (LSU), translational elongation factor (TEF), and the largest and second-largest subunits of RNA polymerase II (RPB1 and RPB2)) revealed that the divergent lineage is the sister group to all other known Cenococcum isolates. Isolates of the divergent lineage grow fast on nutrient media and do not form ectomycorrhizas on seedlings of several pine and oak species. Our results indicate that C. geophilum sensu lato includes more phylogenetically distinct cryptic species than have previously been reported. Furthermore, the divergent lineage appears to be a non-mycorrhizal sister group. We discuss the phylogenetic diversity of C. geophilum sensu lato and argue in favor of species recognition based on phylogenetic and ecological information in addition to morphological characteristics. A new genus and species (Pseudocenococcum floridanum gen. et sp. nov.) is proposed to accommodate a divergent and putatively non-mycorrhizal lineage.

Molecular and morphological analyses confirm Rhizopogon verii as a widely distributed ectomycorrhizal false truffle in Europe, and its presence in South America

The genus Rhizopogon includes species with hypogeous or subepigeus habit, forming ectomycorrhizae with naturally occurring or planted pines (Pinaceae). Species of the genus Rhizopogon can be distinguished easily from the other hypogeous basidiomycetes by their lacunose gleba without columella and their smooth elliptical spores; however, the limit between species is not always easy to establish. Rhizopogon luteolus, the type species of the genus, has been considered one of the species that are more abundant in Europe, as well as it has been cited in pine plantation of North and South America, different parts of Africa, Australia, and New Zealand. However, in this study, based on molecular analyses of the ITS nuclear ribosomal DNA (nrDNA) sequences (19 new sequences; 37 sequences from GenBank/UNITE, including those from type specimens), we prove that many GenBank sequences under R. luteolus were misidentified and correspond to Rhizopogon verii, a species described from Tunisia. Also, we confirm that basidiomes and ectomycorrhizae recently collected in Germany under Pinus sylvestris, as well as specimens from South of Brazil under Pinus taeda belong to R. verii. Thanks to the numerous ectomycorrhizal tips collected in Germany, a complete description of R. verii/P. sylvestris ectomycorrhiza is provided. Moreover, since in this paper the presence of R. verii in South America is here reported for the first time, a short description of basidiomes collected in Brazil, compared with collections located in different European herbaria, is included.

Solving the ecological puzzle of mycorrhizal associations using data from annotated collections and environmental samples - an example of saddle fungi

The relation between ecological and genetic divergence of Helvella species (saddle fungi) has been perplexing. While a few species have been clearly demonstrated to be ectomycorrhizal fungi, ecological roles of many other species have been controversial, alternately considered as either saprotrophic or mycorrhizal. We applied SATé to build an inclusive deoxyribonucleic acid sequence alignment for the internal transcribed spacers (ITS) of annotated Helvella species and related environmental sequences. Phylogenetic informativeness of ITS and its regions were assessed using PhyDesign. Mycorrhizal lineages present a diversity of ecology, host type and geographic distribution. In two Helvella clades, no Helvella ITS sequences were recovered from root tips. Inclusion of environmental sequences in the ITS phylogeny from these sequences has the potential to link these data and reveal Helvella ecology. This study can serve as a model for revealing the diversity of relationships between unculturable fungi and their potential plant hosts. How non-mycorrhizal life styles within Helvella evolved will require expanded metagenomic investigation of soil and other environmental samples along with study of Helvella genomes.