Elsevier

Mycoscience

Volume 61, Issue 6, November 2020, Pages 282-292
Mycoscience

Full paper
Grosmannia tibetensis, a new ophiostomatoid fungus associated with Orthotomicus sp. (Coleoptera) in Tibetan subalpine forests

https://doi.org/10.1016/j.myc.2020.05.004Get rights and content

Highlights

  • Grosmannia tibetensis, the first record of ophiostomatoid fungi from Tibet.

  • This species is characterized by both Leptographium and Pesotum asexual states.

  • The first report of tubulin paralogue in ophiostomatoid fungi.

Abstract

Few ophiostomatoid fungi have been reported from the margin of the Tibetan Plateau and none have been found in the central portion of the region. In a survey of ophiostomatoid fungi associated with spruce bark beetles in Tibetan subalpine forests, numerous strains of Leptographium s. l. (Ophiostomataceae) were isolated from Orthotomicus sp. (Coleoptera: Scolytinae) and its galleries infesting Picea likiangensis var. balfouriana. Morphological characters and phylogenetic analysis based on multiple DNA sequence data (ITS2-partial LSU rDNA region, beta-tubulin and transcription elongation factor-1α genes) revealed a new species in the “Grosmannia penicillata complex”, which is proposed as G. tibetensis. The species is characterized by both Leptographium and Pesotum asexual states, which is unique in the “G. penicillata complex”. Additionally, sequences of the tubC paralogue gene were found combining with tub2 sequences in many species of the “G. penicillata complex”, resulting in incongruent trees. This is the first report of tubulin paralogue genes in ophiostomatoid fungi. Gene duplication and losses make beta-tubulin a potentially challenging locus for use as a molecular marker for tracing speciation.

Introduction

Ophiostomatoid fungi have symbiotic relationships with bark beetles. The fungi provide a direct benefit to their beetle partners through producing bark beetle aggregation pheromones and semiochemicals (Zhao et al., 2019a). In many cases, the fungi are virulent to host plants (Brasier, 1979; Harrington, Fraedrich, & Aghayeva, 2008; Wingfield, Seifert, & Webber, 1993), and this may indirectly help the beetles overcome the defensive system of their host plants (Zhao et al., 2019b). This fungal group is polyphyletic and includes numerous genera in two orders, Ophiostomatales (Sordariomycetidae) and Microascales (Hypocreomycetidae) (de Beer & Wingfield, 2013). Ophiostoma and Leptographium sensu lato are the two genera with the greatest species diversity.

Many species of Leptographium s. l. were previously classified in different genera such as Ceratocystis, Grosmannia, or Ophiostoma. Phylogenetic analysis has been based on DNA sequence data such as the nuclear ribosomal large subunit region (LSU), internal transcribed spacer regions 1 and 2 of the nuclear ribosomal DNA operon, including the 5.8S region (ITS), the beta-tubulin gene region (BT), and the transcription elongation factor-1α gene region (EF). These analyses can reveal the relationships and provide accurate classification of the fungi. However, since a single name is now used for the fungi in this group, two generic names, including the older and broader name Leptographium and a teleomorphic name, Grosmannia, are used by taxonomists and require reevaluation (de Beer & Wingfield, 2013; Jacobs & Wingfield, 2013).

In mainland China, the taxonomy of Leptographium is now reasonably well known. Numerous studies using both morphological and DNA-based phylogenetic approaches have identified at least 37 Leptographium species, of which 23 were new (Zhou et al., 2000; Lu, Decock, Zhang, & Maraite, 2008; Lu, Decock, et al., 2009; Lu, Zhou, et al., 2009; Paciura et al., 2010; Yin, Duong, Wingfield, Zhou, & de Beer, 2014; Chang et al., 2019, 2017; Liu et al., 2017; Wang et al., 2019; Wang et al., 2020; Yin, Wingfield, Zhou, & de Beer, 2020). However, only 8 of the 34 Chinese provinces have been surveyed and large areas harboring diverse forest ecosystems remain unexplored. Thus, there is great potential for discovering new species in China. The Tibetan Plateau is an area that is unexplored for ophiostomatoid fungi.

The Tibetan Plateau is the highest and largest plateau in the world. The unique geographical conditions there have produced diverse ecosystems and created favorable environments for species maintenance and formation of new species (Gansser, 1964). As such, the Tibetan Plateau has rich biological diversity (Liu, Wang, Wang, Hideaki, & Abbott, 2006). Many native coniferous trees occur on the Tibetan Plateau (China flora editorial committee of Chinese academy of sciences, 1978). Spruces (Picea spp.) are the dominant trees in the forests. More than half of the 34 world species of Picea occur on the plateau and adjacent regions (Sun et al., 2014). Tibetan spruce forests are often infested by bark beetles (Yin, Huang, & Li, 1984). Nine ophiostomatoid fungus species have been reported in association with four bark beetle species that infest spruces on the plateau margin in Qinghai province (Yin, Wingfield, Zhou, & de Beer, 2016, 2020).

In a survey of the ophiostomatoid fungi on bark beetles infesting Picea likiangensis var. balfouriana (Rehder & E.H. Wilson) Hillier. in forests of the Tibetan Plateau, an undescribed species of Leptographium s. l., was isolated from Orthotomicus sp. adults. Their galleries were characterized by morphological observations and multilocus DNA sequence data. This species is described as Grosmannia tibetensis sp. nov. This is the first report of the presence of tubulin paralogue genes in ophiostomatoid fungi.

Section snippets

Collection of samples and fungus isolations

Fungi were isolated from adults and breeding galleries of Orthotomicus sp., infesting the bark of P. likiangensis var. balfouriana in Zuogong county (29°14′2″N; 98°2′52″E, altitude 3780 m), Tibet autonomous region. Adult beetles and their galleries were individually placed in sterile Eppendorf tubes and envelope bags, respectively. They were stored at 4 °C until fungal isolations were made. Each adult beetle was dismembered into about 15 pieces on the surface of 2% water agar without previous

Collection of samples, isolation of fungi, and sequence comparisons

Twenty adults and 50 breeding galleries of Orthotomicus sp. were collected from P. likiangensis var. balfouriana in Zuogong county, Tibet autonomous region. A total of 225 strains were obtained, of which 52 were identified as ophiostomatoid fungi based on morphological characteristics. Among them, 29 strains were derived from the adult beetles and 23 strains were derived from the galleries. The 52 strains were characterized by olivaceous colored colonies, typical Leptographium and Pesotum

Discussion

Fifty-two strains of ophiostomatoid fungi were isolated from adults and galleries of Orthotomicus sp. infesting P. likiangensis var. balfouriana in forest of the Tibetan Plateau. Using a combination of morphology and phylogeny, G. tibetensis sp. nov. was described and illustrated based on these strains. The species belongs to the “G. penicillata complex” and is the first record of ophiostomatoid fungi from Tibet.

Grosmannia penicillata is the type species of the genus. It forms a well-supported

Declaration of competing interest

The authors declare no conflicts of interest. All the experiments undertaken in this study comply with the current laws of the country where they were performed.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Project No.: 31770682, 31070571). Dr. Cony Decock gratefully acknowledges the financial support received from the Belgian State (Belgian Federal Science Policy through the BCCM™ research program). We thank LetPub (www.letpub.com) for its linguistic assistance during the preparation of this manuscript.

References (55)

  • F.R. Barrie et al.

    International code of nomenclature for algae, fungi and plants (Melbourne code)

    (2012)
  • Z.W. de Beer et al.

    Emerging lineages in the Ophiostomatales

  • C.M. Brasier

    Dual origin of recent Dutch elm disease outbreaks in Europe

    Nature

    (1979)
  • R. Chang et al.

    Ophiostomatoid fungi associated with conifer-infesting beetles and their phoretic mites in Yunnan, China

    Mycokeys

    (2017)
  • R. Chang et al.

    Ophiostomatoid fungi associated with the spruce bark beetle Ips typographus, including 11 new species from China

    Persoonia

    (2019)
  • China flora editorial committee of Chinese academy of sciences

    Flora Reipublicae Popularis Sinicae, Tomus 7 Gymnospermae

    (1978)
  • D. Darriba et al.

    jModelTest 2: more models, new heuristics and parallel computing

    Nature Methods

    (2012)
  • N. Feau et al.

    Finding single copy genes out of sequenced genomes for multilocus phylogenetics in non-model fungi

    PloS One

    (2011)
  • A. Gansser

    Geology of the Himalayas

    (1964)
  • N.L. Glass et al.

    Development of primer sets designed for use with the PCR to amplify conserved genes from filamentous Ascomycetes

    Applied and Environmental Microbiology

    (1995)
  • T.C. Harrington et al.

    Raffaelea lauricola, a new ambrosia beetle symbiont and pathogen on the Lauraceae

    Mycotaxon

    (2008)
  • D.L. Hawksworth

    A new dawn for the naming of fungi: Impacts of decisions made in Melbourne in July 2011 on the future publication and regulation of fungal names

    IMA Fungus

    (2011)
  • V. Hubka et al.

    β-Tubulin paralogue tubC is frequently misidentified as the benA gene in Aspergillus section Nigri taxonomy: Primer specificity testing and taxonomic consequences

    Persoonia

    (2012)
  • K. Jacobs et al.

    Two new species of Leptographium from Dryocetes authographus and Hylastes cunicularius in Norway

    Mycological Progress

    (2010)
  • K. Jacobs et al.

    Leptographium species: Tree pathogens, insect associates, and agents of blue-stain

    (2001)
  • K. Jacobs et al.

    An overview of Leptographium and Grosmannia

  • K. Jacobs et al.

    Phylogenetic relationships in Leptographium based on morphological and molecular characters

    Canadian Journal of Botany

    (2001)
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    These authors contributed equally.

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