Not (only) poison pies - Hebeloma (Agaricales, Hymenogastraceae) in Mexico

The species of Hebeloma have been little studied in Mexico, but have received attention as edibles and in trials to enhance production of edible fungi and tree growth through inoculation of seedlings with ectomycorrhizal fungi. Here we describe three new species of Hebeloma that are currently known only from Mexico. These species belong to separate sections of the genus: H.ambustiterranum is a member of H.sect.Hebeloma, H.cohaerens belongs to H.sect.Theobromina, while H.magnicystidiatum belongs to H.sect.Denudata. All three species were collected from subtropical pine-oak woodland; all records of H.cohaerens came from altitudes above 2500 m. Hebelomaambustiterranum is commonly sold in the local markets of Tlaxcala as a prized edible mushroom. An additional nine species are reported from Mexico, of which eight are new records for the country: H.aanenii, H.eburneum, H.excedens, H.ingratum, H.neurophyllum, H.sordidulum, H.subaustrale and H.velutipes. First modern descriptions of H.neurophyllum and H.subaustrale, originally described from the USA, are given here.

Genetic characterization, evaluation of growth and production of biomass of strains from wild edible mushrooms of Lyophyllum of Central Mexico

The present study conducted a genetic characterization and determined growth rate and biomass production in solid and liquid media, using strains obtained from wild edible sporomes of Lyophyllum that grow in high mountains. Vegetative isolation was used to obtain a total of four strains, which were divided into two clades within the section Difformia: Lyophyllum sp. and Lyophyllum aff. shimeji. Growth rate and biomass production were influenced by both the culture media and the strains. In a potato dextrose agar medium, the strains presented a higher growth rate, while in a malt extract-peptone and yeast agar medium, the growth rate was lower, but with a higher biomass production that was equal to that in the malt extract-peptone and yeast liquid medium.

Caryophyllales are the main hosts of a unique set of ectomycorrhizal fungi in a Neotropical dry forest

The ectomycorrhizal symbiosis was long thought to be restricted to temperate forests. However, as tropical forests have been explored, it has become clear that these habitats host unique ectomycorrhizal (ECM) fungi. We have been exploring tropical dry forests (TDF), which are endangered terrestrial ecosystems and hotspots of endemism. Since Fabaceae is the main plant family in this environment, we hypothesized that trees in this lineage would be the main ECM hosts. We sequenced the ITS rDNA region from fungi and both rbcL and trnL cpDNA from plants to identify both symbiotic partners from root tips. The systematic position of each symbiont was confirmed by Bayesian phylogenetic inference. We identified 20 plant species belonging to 10 families that hosted 19 unique ECM fungal species from 5 lineages. Most ECM fungi were associated with Caryophyllales, not with Fabaceae. Achatocarpus and Guapira, the main hosts, are scattered throughout the forest and are not in monodominant patches. The low ECM fungal diversity can be explained by the low density of host plants and their high specificity. Our results indicate that Caryophyllales is an important order of tropical ECM hosts with at least four independent evolutionary lineages that have evolved the ability to form ectomycorrhizae.

Word-wide meta-analysis of Quercus forests ectomycorrhizal fungal diversity reveals southwestern Mexico as a hotspot

Quercus is the most diverse genus of ectomycorrhizal (ECM) host plants; it is distributed in the Northern and Southern Hemispheres, from temperate to tropical regions. However, their ECM communities have been scarcely studied in comparison to those of conifers. The objectives of this study were to determine the richness of ECM fungi associated with oak forests in the Cuitzeo basin in southwestern Mexico; and to determine the level of richness, potential endemism and species similarity among ECM fungal communities associated with natural oak forests worldwide through a meta-analysis. The ITS DNA sequences of ECM root tips from 14 studies were included in the meta-analysis. In total, 1065 species of ECM fungi have been documented worldwide; however, 812 species have been only found at one site. Oak forests in Europe contain 416 species, Mexico 307, USA 285, and China 151. Species with wider distributions are Sebacinaceae sp. SH197130, Amanita subjunquillea, Cenococcum geophilum, Cortinarius decipiens, Russula hortensis, R. risigallina, R. subrubescens, Sebacinaceae sp. SH214607, Tomentella ferruginea, and T. lapida. The meta-analysis revealed (1) that Mexico is not only a hotspot for oak species but also for their ECM mycobionts. (2) There is a particularly high diversity of ECM Pezizales in oak seasonal forests from western USA to southwestern Mexico. (3) The oak forests in southwestern Mexico have the largest number of potential endemic species. (4) Globally, there is a high turnover of ECM fungal species associated with oaks, which indicates high levels of alpha and beta diversity in these communities.

Ectomycorrhizal and endophytic fungi associated with Alnus glutinosa growing in a saline area of central Poland

Alnus glutinosa (black alder) is a mycorrhizal pioneer tree species with tolerance to high concentrations of salt in the soil and can therefore be considered to be an important tree for the regeneration of forests areas devastated by excessive salt. However, there is still a lack of information about the ectomycorrhizal fungi (EMF) associated with mature individuals of A. glutinosa growing in natural saline conditions. The main objective of this study was to test the effect of soil salinity and other physicochemical parameters on root tips colonized by EMF, as well as on the species richness and diversity of an EMF community associated with A. glutinosa growing in natural conditions. We identified a significant effect of soil salinity (expressed as electrical conductivity: EC_e and EC_1:5) on fungal taxa but not on the total level of EM fungal colonization on roots. Increasing soil salinity promoted dark-coloured EMF belonging to the order Thelephorales (Tomentella sp. and Thelephora sp.). These fungi are also commonly found in soils polluted with heavy-metal. The ability of these fungi to grow in contaminated soil may be due to the presence of melanine, a natural dark pigment and common wall component of the Thelephoraceae that is known to act as a protective interface between fungal metabolism and biotic and abiotic environmental stressors. Moreover, increased colonization of fungi belonging to the class of Leotiomycetes and Sordiomycetes, known as endophytic fungal species, was observed at the test sites, that contained a larger content of total phosphorus. This observation confirms the ability of commonly known endophytic fungi to form ectomycorrhizal structures on the roots of A. glutinosa under saline stress conditions.

Clavulina-Membranomyces is the most important lineage within the highly diverse ectomycorrhizal fungal community of Abies religiosa

Abies religiosa is an endemic conifer of Mexico, where its monodominant forests are the winter refuge of the monarch butterfly. Due to climate change, it has been estimated that by 2090, A. religiosa populations will decline by 96.5 %. To achieve success, reforestation programs should consider its ectomycorrhizal (ECM) fungi. We used ITS nrDNA sequences to identify the ECM fungi associated with A. religiosa and, based on its abundance and frequency, determined the diversity and community structure in a pure A. religiosa forest near Mexico City. Using sequence metadata, we inferred the species geographic distribution and host preferences. We conducted phylogenetic analyses of the Clavulinaceae (the most important family). The ECM community held 83 species, among which the richest genera were Inocybe (21 species), Tomentella (10 species), and Russula (8 species). Besides its low species richness, the Clavulina-Membranomyces lineage was the most dominant family. Clavulina cf. cinerea and Membranomyces sp. exhibited the highest relative abundance and relative frequency values. Phylogenetic analyses placed the Clavulinaceae genotypes in three different clades: one within Membranomyces and two within Clavulina. A meta-analysis showed that the majority of the ECM fungi (45.78 %) associated with A. religiosa in Mexico have also been sequenced from North America and are shared by Pinaceae and Fagaceae. In contrast, because they have not been sequenced previously, 32.2 % of the species have a restricted distribution. Here, we highlight the emerging pattern that the Clavulina-Membranomyces lineage is dominant in several ECM communities in the Neotropics, including Aldinia and Dicymbe legume tropical forests in the Guyana Shield, the Alnus acuminata subtropical communities, and the A. religiosa temperate forests in Mexico.

Commercial Sphagnum peat moss is a vector for exotic ectomycorrhizal mushrooms

Sphagnum peat moss is one of the most commonly used substrates for forest plant and houseplant production. It is extracted from peat bogs in the circumboreal region and exported worldwide. Commercial peat moss is pasteurized, and is therefore believed to be free of viable ectomycorrhizal propagules. We used a bioassay with Pinus montezumae to demonstrate that commercial peat moss carries viable ectomycorrhizal spores, able to form mycorrhizae. Ectomycorrhizal fungi on seedling root-tips were sequenced for phylogenetic analyses using the ITS rDNA barcode region. We found three species: Suillus brevipes, Sphaerosporella brunnea, and Thelephora terrestris. S. brevipes and T. terrestris were found as viable inoculum transported in the peat moss, while S. brunnea was a greenhouse contaminant. S. brevipes and T. terrestris have biological characteristics (such as heat resistant and long living spores) that facilitate their survival to the extraction, transport, and storage processes of peat moss. This allows them to colonize nursery seedlings and to become potential invasive species in plantation areas. S. brevipes and T. terrestris are two of the most introduced fungi by anthropic activities; it has been argued that the vehicle for the introductions are their pine symbionts. This is the first time it has been demonstrated that peat moss is an important vehicle for the introduction of these fungi; a fact potentially related to the pattern of introduction of these ectomycorrhizal species from the northern hemisphere to elsewhere in the world.

The ectomycorrhizas of Lactarius cuspidoaurantiacus and Lactarius herrerae associated with Alnus acuminata in Central Mexico

Two pure Alnus acuminata stands established in a montane forest in central Mexico (Puebla State) were monitored between 2010 and 2013 to confirm and recognize the ectomycorrhizal (EcM) systems of A. acuminata with Lactarius cuspidoaurantiacus and Lactarius herrerae, two recently described species. Through comparison of internal transcribed spacer (ITS) of nuclear ribosomal DNA sequences from basidiomes and ectomycorrhizas sampled in the forest stands, we confirmed their ectomycorrhizal association. The phytobiont was corroborated by comparing ITS sequences obtained from EcM root tips and leaves collected in the study site and from other sequences of A. acuminata available in Genbank. Detailed morphological and anatomical descriptions of the ectomycorrhizal systems are presented and complemented with photographs.