Abstract
Ophiostomatoid fungi are known for their associations with bark beetles, and some species are important sources of tree diseases. Ceratocystiopsis is a genus of the ophiostomatoid fungi in order Ophiostomatales. The shortage of DNA barcodes for many species in this genus has resulted in the presence of many unnamed cryptic species. In this study, Ceratocystiopsis subelongati sp. nov. associated with Ips subelongatus infesting Pinus sylvestris var. mongolica in Inner Mongolia, China, was identified and described based on phylogenetic inference of multi-gene DNA sequences and morphological characteristics. The species is characterized by a hyalorhinocladiella- to sporothrix-like asexual state and an optimal growth temperature of 30 °C. Artificial inoculation tests in the field showed that it is mildly pathogenic to five-year-old larch trees, the main host of I. subelongatus. It is also the first described Ceratocystiopsis species associated with I. subelongatus in China. This discovery should provide new avenues for studying the symbiosis between bark beetles and ophiostomatoid fungi.
Highlights
Accepted: 14 December 2021Ophiostomatoid fungi belong to the Ascomycota, which have similar basic morphological features, such as ascomata with long necks and sticky drops on the conidiogenous apparatus [1,2]
Our strains formed a separate branch with high node supports and were separated from a branch containing multiple species (C. minima, C. minuta, C. weihaiensis, and Ceratocystiopsis sp. 2) based on the phylogenetic trees of the combined datasets (Figure 1) and including the 5.8S region (ITS) datasets (Supplementary Materials Figure S1)
In the phylogenetic analyses based on the individual Tub2 datasets, our strains clustered within a separate lineage with good supports (Supplementary Materials Figure S2)
Summary
Ophiostomatoid fungi belong to the Ascomycota (orders Ophiostomatales and Microascales), which have similar basic morphological features, such as ascomata with long necks and sticky drops on the conidiogenous apparatus [1,2]. These morphological features are thought to represent convergent evolution to be better transmitted by vector insects [3]. C. synnemata, C. lunata, C. yantaiensis, and C. weihaiensis were identified and described based on internal transcribed spacer regions 1 and 2 of the nuclear ribosomal DNA operon, including the 5.8S region (ITS), the β-tubulin gene region (Tub2), and the transcription elongation factor1-α gene region
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