The composition and diversity of fungal communities associated with three endangered orchid species, Hadrolaelia jongheana, Hoffmannseggella caulescens, and Hoffmannseggella cinnabarina, found in different vegetation formations of the Atlantic Forest were determined by constructing clone libraries and by applying diversity and richness indices. Our results demonstrated the presence of Basidiomycetes. Sebacinales (81.61%) and Cantharellales (12.10%) were the dominant orders and are potential candidates for orchid mycorrhizal fungi. The Ascomycetes identified included the Helotiales (29.31%), Capnodiales (18.10%), and Sordariales (10.34%), among others. These orders may represent potentially endophytic fungi. A Shannon-Wiener diversity index (H') analysis showed a relatively high fungal community diversity associated with these tropical orchids. This diversity may offer greater flexibility in terms of the adaptation of the plants to changing environmental conditions and the potential facilitation of reintroduction programs. The Simpson diversity index values showed that all of the libraries included dominant species, and a LIBSHUFF analysis showed that the fungal communities were structurally different from each other, suggesting an influence of local factors on this diversity. This study offers important information for the development of conservation strategies for threatened and endemic species of Brazilian flora in an important and threatened hotspot.

Approximately 10% of vascular plants are epiphytes and, even though this has long been ignored in past research, can interact with a variety of fungi, including mycorrhizal ones. However, the structure of fungal communities on bark, as well as their relationship with epiphytic plants, is largely unknown.• To fill this gap, we conducted environmental metabarcoding of ITS-2 region to understand the spatial structure of fungal communities of the bark of tropical trees, with a focus on epiphytic orchid mycorrhizal fungi, and tested the influence of root proximity.• For all guilds, including orchid mycorrhizal fungi, fungal communities were more similar when spatially closed on bark, i.e., displayed positive spatial autocorrelation.They also showed distance decay of similarity from epiphytic roots, meaning that their composition on bark increasingly differed, compared to roots, with distance from roots.• We first showed that all the investigated fungal guilds presented a spatial structure at very small scales. This spatial structure was influenced by the roots of epiphytic plants, suggesting the existence of an epiphytic rhizosphere. Finally, we showed that orchid mycorrhizal fungi were aggregated around them, possibly resulting from a reciprocal influence between the mycorrhizal partners.

the genus Tulasnella often forms mycorrhizas with orchids and has worldwide distribution. Species of this genus are associated with a wide range of orchids, including endangered hosts. initially, species identification relied mostly on morphological features and few cultures were preserved for later phylogenetic comparisons. In this study, a total of 50 Tulasnella isolates were collected from their natural sites in Minas Gerais, Brazil, cultured, and subjected to a phylogenetic analysis based on alignments of sequences of the internal transcribed spacer (itS) of the nuclear ribosomal DnA. our results, based on phylogeny, integrated with nucleotide divergence and morphology, revealed the diversity of isolated Tulasnella species, which included four new species, namely, Tulasnella brigadeiroensis, Tulasnella hadrolaeliae, Tulasnella orchidis and Tulasnella zygopetali. the conservation of these species is important due to their association with endangered orchid hosts and endemic features in the Brazilian Atlantic forest.

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