Abstract
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.
Highlights
Orchidaceae is the largest family of flowering plants, with approximately 27,000 species described[1]
Species identification is mostly based on phylogenetic concordance of multiple unrelated genes/regions, but for this complex genus, the internal transcribed spacer (ITS) of the nuclear ribosomal DNA was shown to be highly suitable for species delimitation in Tulasnella[31,38]
Tulasnella isolates from Brazilian Atlantic Forest
Summary
Orchidaceae (or orchids) is the largest family of flowering plants, with approximately 27,000 species described[1]. Many orchid species are endangered, mainly due to anthropogenic pressure and dependency between orchids and other organisms, i.e. pollinators or mycorrhizal fungi[4,5]. Cattleya cinnabarina and Cattleya caulescens are rupicolous (i.e. grow on bare rocks) and endemic to the Southeastern Brazil[8] These species belong to Brazilian Atlantic Forest, a highly diverse but endangered hotspot of biodiversity[9]. Like all orchids, they need mycorrhizal fungi for germination due to the limited reserves in seeds[10]. Identification of mycorrhizal fungi in South American orchids, mostly conducted in Brazil, has often revealed Tulasnella symbionts: Tulasnella species were isolated from Epidendrum secundum[26,27], Epidendrum dendrobioides and Sophronits milleri[28], Oeceoclades maculata, Epidendrum rigidum and Polystachya concreta[29], E. rigidum and P. concreta[30]. Species identification is mostly based on phylogenetic concordance of multiple unrelated genes/regions, but for this complex genus, the internal transcribed spacer (ITS) of the nuclear ribosomal DNA was shown to be highly suitable for species delimitation in Tulasnella[31,38]
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