Clarification of the concept of Ganoderma orbiforme with high morphological plasticity.

Dong-Mei Wang,Sheng-Hua Wu,Yi-Jian Yao

doi:10.1371/journal.pone.0098733

Dong-Mei Wang, Sheng-Hua Wu + Show 1 more

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https://doi.org/10.1371/journal.pone.0098733

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Abstract

Ganoderma has been considered a very difficult genus among the polypores to classify and is currently in a state of taxonomic chaos. In a study of Ganoderma collections including numerous type specimens, we found that six species namely G. cupreum, G. densizonatum, G. limushanense, G. mastoporum, G. orbiforme, G. subtornatum, and records of G. fornicatum from Mainland China and Taiwan are very similar to one another in basidiocarp texture, pilear cuticle structure, context color, pore color and basidiospore characteristics. Further, we sequenced the nrDNA ITS region (ITS1 and ITS2) and partial mtDNA SSU region of the studied materials, and performed phylogenetic analyses based on these sequence data. The nrDNA ITS sequence analysis results show that the eight nrDNA ITS sequences derived from this study have single-nucleotide polymorphisms in ITS1 and/or ITS2 at inter- and intra-individual levels. In the nrDNA ITS phylogenetic trees, all the sequences from this study are grouped together with those of G. cupreum and G. mastoporum retrieved from GenBank to form a distinct clade. The mtDNA SSU sequence analysis results reveal that the five mtDNA SSU sequences derived from this study are clustered together with those of G. cupreum retrieved from GenBank and also form a distinct clade in the mtDNA SSU phylogenetic trees. Based on morphological and molecular data, we conclude that the studied taxa are conspecific. Among the names assigned to this species, G. fornicatum given to Asian collections has nomenclatural priority over the others. However, the type of G. fornicatum from Brazil is probably lost and a modern description based on the type lacks. The identification of the Asian collections to G. fornicatum therefore cannot be confirmed. To the best of our knowledge, G. orbiforme is the earliest valid name for use.

Highlights

All the eight nrDNA ITS sequences derived from this study (JX840345–JX840352, Table 1) differ from one another in one to 11 single-nucleotide substitution(s) in the combined ITS1 and ITS2 region
All or most nucleotide variations (71%–83%) are located in the nrDNA ITS2 region of the materials sequenced in this study with reference to the sequence of TNM-F0010592 (JX840347, Figure 1)
We noticed that six of the eight materials subjected to nrDNA ITS sequencing in this study have intra-individual single-nucleotide polymorphisms ranging from one to nine sites (Figure 1)

Summary

Introduction

(Ganodermataceae, Basidiomycetes) is a widespread genus of wood decaying polypore fungi, with high species diversity in the tropics [1]. This genus is well-known for its high medicinal properties especially in East Asia [2,3,4], and for its pathogenicity in South and Southeast Asia [5,6] and East Asia [7]. The identification and circumscription of species within Ganoderma are unclear for various reasons. Ganoderma is in a state of taxonomic chaos as indicated by the fact that ca. Ganoderma is in a state of taxonomic chaos as indicated by the fact that ca. one-third of 219 species proposed within the genus are synonyms and some of the remaining species still require further clarification [8,9]

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