Ophiostomatalean fungi associated with bark beetles infesting Pinus armandii Franch., with characterizations of seven new species from Shaanxi, China

A field and taxonomic study in Ankang, Shaanxi Province, China, identified 20 ophiostomatalean fungal species from bark-beetle galleries associated with Pinus armandii Franch., including the formal characterization of seven previously undescribed species. The researchers isolated 230 strains from 46 gallery samples collected in August 2022 at Huoditang Forest Farm and Chengguan Town. Fifty representative strains were examined in greater detail through culture characteristics, microscopy, DNA sequencing and multilocus phylogenetic analyses.

The fungi were recovered from galleries and pupal chambers in beetle-infested P. armandii. Material was transferred to 2% malt extract agar and incubated in darkness at 25 °C for one to two weeks before representative isolates were purified. The study used the β-tubulin, internal transcribed spacer, ribosomal large subunit and translation elongation factor 1-alpha DNA regions. Relationships were assessed with maximum-likelihood, maximum-parsimony and Bayesian analyses, while colony growth and reproductive structures were examined to support taxonomic assignments.

Among the 50 representative strains, phylogenetic analysis placed them in 20 terminal clades. Six corresponded to previously described species: Ceratocystiopsis weihaiensis, Graphilbum fragrans, Graphilbum parakesiyea, Ophiostoma ips, Ophiostoma minus and Sporothrix pseudoabietina. Two lineages were left as Ceratocystiopsis sp. 1 and Leptographium sp. 1 because they clustered with unpublished GenBank strains, preventing the authors from making what they considered secure new-species designations.

The seven newly characterized species were Ceratocystiopsis rugosa, Graphilbum prolificum, Graphilbum ramosus, Masuyamyces huoditangensis, Ophiostoma flavescens, Ophiostoma lenta and Ophiostoma mediotumida. Their recognition was supported by phylogenetic placement together with differences in morphology and culture. C. rugosa was closely related to C. debeeria but had smaller micronematous conidiophores and conidia and a distinctly wrinkled colony surface. G. prolificum was separated from related Graphilbum species by molecular, morphological and cultural evidence, including relatively small conidia and growth of 11.3 mm per day on 2% malt extract agar at 25 °C.

Other new taxa were distinguished by characteristic combinations of growth, reproductive structures and phylogenetic position. G. ramosus differed from its close relative G. gorcense in conidial size, growth rate and colony behavior, including the absence of the later greenish-grey color change observed in G. gorcense. M. huoditangensis formed an independent lineage related to M. pallidulum but had smaller conidiophores and conidia, white rather than hyaline colonies, and slower growth. O. flavescens was related to O. japonicum but had smaller conidia and developed light-yellow central mycelium that later turned black.

O. lenta was closely related to O. sejunctum in the ITS analysis but differed in lacking the sexual structures and secondary and tertiary conidiophores reported for O. sejunctum. O. mediotumida represented a distinct lineage related to O. angusticollis and O. denticulatum. It was characterized by perithecia, elongate ascospores and opaque milky-white colonies. The new species also had specific recorded beetle-vector and host associations: C. rugosa and G. prolificum were obtained from galleries of Polygraphus sp. infesting P. armandii; G. ramosus, M. huoditangensis and O. flavescens were associated with Dendroctonus armandi; and O. lenta and O. mediotumida were obtained from galleries of Dryocoetes hectographus.

Ophiostoma shennongense was the most frequently isolated taxon, with 63 isolates representing 27.39% of the total. O. ips accounted for 26 isolates, or 11.30%. Ceratocystiopsis sp. 1, G. parakesiyea and S. pseudoabietina each yielded 21 isolates, or 9.13%. The collection comprised 76 isolates from Chengguan Town and 154 from Huoditang Forest Farm. All species detected at Chengguan Town had previously been described, whereas all seven new species were recovered at Huoditang Forest Farm, indicating additional taxonomic diversity within the limited area sampled.

The findings document fungal diversity and taxonomic relationships in the sampled galleries, but they do not establish the pathogenicity of the seven new fungi or demonstrate effects on beetle survival, reproduction or tree resistance. The study covered two sites during one collection period, and the isolates represent fungi recoverable from the sampled galleries rather than a complete inventory of fungi throughout the trees or region. The authors stated that the symbiotic mechanisms between these ophiostomatalean fungi and bark beetles, as well as the pathogenicity of the new species, require further study.

The study expanded the documented diversity of ophiostomatalean fungi associated with bark beetles on P. armandii. It also provided formal species descriptions, sequence data, culture information and type specimens for the seven new taxa. The findings show that the fungi recoverable from bark-beetle galleries in the surveyed part of Shaanxi included substantial taxonomic diversity, with the new species concentrated at Huoditang Forest Farm in this sample.

Subject of Research: Taxonomic diversity of ophiostomatalean fungi associated with bark beetles infesting Pinus armandii in Shaanxi, China

Article Title: Ophiostomatalean fungi associated with bark beetles infesting Pinus armandii Franch., with characterizations of seven new species from Shaanxi, China

Article References: Chen, M., Ran, Y., Liu, C., & Yin, M. (2026). Ophiostomatalean fungi associated with bark beetles infesting Pinus armandii Franch., with characterizations of seven new species from Shaanxi, China. MycoKeys, 140, 173-216. https://doi.org/10.3897/mycokeys.140.199146

Image Credits: AI Generated

DOI: 10.3897/mycokeys.140.199146

Keywords: ophiostomatalean fungi, bark beetles, Pinus armandii, Shaanxi China, fungal taxonomy, multilocus phylogeny, Ceratocystiopsis, Graphilbum, Masuyamyces, Ophiostoma, Ophiostomatalean, fungi