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Research Article
Two new species of Hirsutella (Ophiocordycipitaceae, Sordariomycetes) that are parasitic on lepidopteran insects from China
expand article infoJiaojiao Qu‡, Xiao Zou‡, Wei Cao‡, Zhongshun Xu‡, Zongqi Liang‡
‡ Guizhou University, Guiyang, China

Corresponding author: Xiao Zou ( xzou@gzu.edu.cn )

Academic editor: Kevin D. Hyde
© 2021 Jiaojiao Qu, Xiao Zou, Wei Cao, Zhongshun Xu, Zongqi Liang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Qu J, Zou X, Cao W, Xu Z, Liang Z (2021) Two new species of Hirsutella (Ophiocordycipitaceae, Sordariomycetes) that are parasitic on lepidopteran insects from China. MycoKeys 82: 81-96. https://doi.org/10.3897/mycokeys.82.66927
Open Access

Abstract

Hirsutella are globally distributed entomopathogenic fungi that offer important economic applications in biological control and biomedicine. Hirsutella was suppressed in favour of Ophiocordyceps affected by the ending of dual nomenclature for pleomorphic fungi in 2011. Currently, Hirsutella has been resurrected as a genus under Ophiocordycipitaceae. In this study, we introduce two new species of Hirsutella, based on morphological and phylogenetic analyses. Hirsutella flava and H. kuankuoshuiensis are pathogenic on different species of larval Lepidoptera in China. Hirsutella flava primarily differs from related species by its awl-shaped base; long and narrow neck, 24–40.8 × 2.2–2.5 μm; long and narrow cymbiform or fusoid conidia, 6.5–10 × 2.1–4.3 μm. Hirsutella kuankuoshuiensis has two types of phialides and distinctive 9.9–12.6 × 2.7–4.5 μm, clavate or botuliform conidia. The distinctions amongst the new species and phylogenetic relationships with other Hirsutella species are discussed.

Keywords

entomopathogenic fungi, Hirsutella, Ophiocordyceps, two new taxa

Introduction

The entomopathogenic fungal genus Hirsutella Pat. was erected by Patouillard (1892) based on the type species H. entomophila. The genus was introduced to the family Ophiocordycipitaceae and its sexual morph was linked to Ophiocordyceps (Sung et al. 2007a; Simmons et al. 2015). In Hirsutella sensu stricto, conidiation is synnematous and phialides typically have a swollen base that tapers abruptly into a long neck producing either a single conidium or 2–3 conidia coated with mucus. The colour of the synnemata ranges from ash-grey or brown to dark brown. The size and shape of the hyaline conidia vary from citriform to oblong, subcylindric, globose, rhombic, or reniform (Luangsa-ard et al. 2017; Quandt et al. 2014). These taxa are important pathogens of agricultural pests and are used as popular traditional medicine and a nutritious food in many Asian countries (Evans 1974; Quandt et al. 2014; Hyde et al. 2019). Several common species of Hirsutella, such as H. thompsonii and H. rhossiliensis, are potentially important biological control agents for nematodes and mites (Jaffee 1992; Van der Geest 2010; Hyde et al. 2019). Further uses involve the development and application of several effective bioactive secondary metabolites (Mazet and Vey 1995; Lang et al. 2005; Qu et al. 2017).

Research on Hirsutella originated in the 1920s. Through the 1950s, Speare (1920), Petch (1924) and subsequent researchers reported 25 new species of the genus. However, many of these species were not described in detail and lacked adequate drawings, as well as holotypes. In addition, many specimens were damaged or lost during wartime (Zou et al. 2016a). In the 1970s and 1980s, Miner, Samson and Evans re-examined the status of Hirsutella and established the modern scientific definition for the genus (Minter and Brady 1980; Evans and Samson 1982, 1984). Since the beginning of the 21st century, the taxonomy, molecular evolution and phylogeny of Hirsutella have been addressed by a small number of Chinese and international studies, with sporadic reports of new species (Seifert 2004; Xiang et al. 2006; Zou et al. 2010). However, it is likely that further new species remain to be discovered, and specific information on insect hosts, pathogenicity and habitats are lacking (Sung et al. 2007a; Hoyos-Carvajal et al. 2009).

Quandt et al. (2014) proposed that Hirsutella should be suppressed in favour of Ophiocordyceps affected by the ending of dual nomenclature for pleomorphic fungi in 2011 (McNeill et al. 2012). Ophiocordyceps is the type genus in the family Ophiocordycipitaceae (Hypocreales, Sordariomycetes) (Sung et al. 2007a). The main characteristics of the sexual morphs of Ophiocordyceps are fibrous, hard, pliant-to-wiry, dark stromata with superficial to immersed perithecia (Sung et al. 2007a; Xiao et al. 2019). Most of the sexual species of Ophiocordyceps were transferred from the genus Cordyceps (Cordycipitaceae) by Sung et al. (2007a). Since many species of Hirsutella are closely related to Cordyceps, the asexual morphs in most of the species in Ophiocordyceps have hirsutella-like features (Kepler et al. 2013; Quandt et al. 2014; Maharachchikumbura et al. 2015, 2016). Therefore, Hirsutella was treated as a separate genus from Ophiocordyceps before the taxonomic revision (Sung et al. 2007a; McNeill et al. 2012; Quandt et al. 2014). For example, some new species only known from a Hirsutella morph have been accepted into Ophiocordyceps (Simmons et al. 2015a; Qu et al. 2018b).

In recent years, the taxonomic transitions of Ophiocordycipitaceae changed rapidly under the new rules. Quandt et al. (2014) included Ophiocordyceps, Tolypocladium, Polycephalomyces, Purpureocillium, Drechmeria and Harposporium in Ophiocordycipitaceae based on morphological and phylogenetic analyses. In the paper “Outline of Ascomycota: 2017”, the genus Hymenostilbe was added into the Ophiocordycipitaceae families (Wijayawardene et al. 2018). According to the latest taxonomic report, the number of genera included in Ophiocordycipitaceae has increased to ten, and among them, Hirsutella, Paraisaria and Perennicordyceps are new additions (Hyde et al. 2020). The taxonomic revision of Ascomycota is continuing. Further research into the phylogeny of these organisms is needed. Examples include investigating the new resources to supplement the available taxonomic information and perform phylogenetic research.

During an investigation of the genetic resources of entomopathogenic fungi in southwest China, we collected two specimens of Lepidoptera insects that were infected by fungi. Two hirsutella-like species were isolated and their gene sequences and morphological traits were shown to be related to Hirsutella sensu stricto. In this study, two new species of Hirsutella are introduced.

Materials and methods

Specimens

The specimens HKAS112884 and HKAS112885 were deposited at the Kunming Institute of Botany, Chinese Academy of Sciences (KIB), Kunming, China. The isolated strains of their asexual stage were deposited at the Institute of Fungal Resources of Guizhou University (GZAC), Guiyang, China. More information about these specimens is shown in Suppl. material 1: Table S1.

Fungal isolation and culture

The fungi were isolated as described by Qu et al. (2018). The surface of specimens was rinsed with sterile water, followed by surface sterilisation with 75% ethanol for 3-5 s. Parts of the insect body were cut off and a piece of tissue was inoculated in haemocoel on a PDA plate for 20 days at 16 °C.

LM and SEM observation

For light microscopy (LM) observations and imaging, the morphological characteristics of mycelia were observed using an optical microscope (OM, BK5000, OPTEC, Chicago, IL, USA) after staining with a lactic acid/phenol cotton blue solution. The captured images of new species were edited and digitally contrasted using Paint Shop Pro v. 5.0.1 (Corel, Ottawa, Canada).

Electron microscopy was performed as described by Qu et al. (2018). Briefly, 1 cubic cm of hyphae with conidia were cut from the fungus on PDA cultures, fixed with 4% glutaraldehyde at 4 °C overnight, and then washed three times with phosphate buffer saline (PBS) (137 mM NaCl, 2.7 mM KCl, 8.1 mM Na2HPO4 and 1.5 mM KH2PO4, pH 7.4) for 10 min each time. Fixed hyphae and conidia were dehydrated using 50%, 70%, 90% and 100% ethanol, 10 min for each concentration, and were finally dehydrated with super-critical carbon dioxide. After being sprayed with gold, the conidia and mucilage were examined by scanning electron microscopy (SEM) (S-3400N, Hitachi, Tokyo, Japan) and photographed.

DNA extraction, PCR amplification and sequencing

Axenic and fresh mycelia (0.05–0.1 g) of the new species were transferred to 1.5 ml Eppendorf tubes for genomic DNA extraction using a Fungal DNA MiniKit (Omega Bio-Tek, Norcross, GA, USA). The universal known primers were used for PCR amplification: (1) NS1/NS4 for the partial small subunit ribosomal RNA gene region (SSU) (White et al. 1990), (2) LROR/LR5 for the partial large subunit rDNA gene region (LSU) (Vilgalys and Hester 1990; Rehner and Samuels 1994), (3) ITS4/ITS5 for the internal transcribed spacer gene region (ITS) (White et al. 1990), (4) 983F/2218R for the partial translation elongation factor 1-alpha gene region (TEF1α) (Sung et al. 2007b) and (5) CRPB1A/RPB1Cr for the partial RNA polymerase II largest subunit gene region (RPB1) (Castlebury et al. 2004).

Molecular phylogeny

To construct a phylogeny of major lineages, 71 representative species were chosen to represent the ecological diversity of Hirsutella and Ophiocordyceps based on previous phylogenetic studies (Simmons et al. 2015b; Xiao et al. 2017; Qu et al. 2018; Xiao et al. 2019). Tolypocladium inflatum and T. ophioglossoides were selected as the outgroup taxa and are classified within Ophiocordycipitaceae (Xiao et al. 2019). The sequences used in this study were combined with published data on hirsutella-like species and Ophiocordycipitaceae. All the other sequences were collected from GenBank and the accession numbers are shown in Table 1.

Table 1.
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GenBank accession numbers for sequences used in the phylogenetic analysis.

Species Insecta Voucher GenBank accession no.
ITS LSU SSU RPB1 TEF1α
Hirsutella cf. haptospora Diptera: Itonididae ARSEF 2228 KM652166 KM652118 KM652075 KM652041 KM652001
H. changbeisanensis Homoptera: leafhopper GZUIFR-hir160527 KY415578 KY415586 KY415592
H. citriformis Hemiptera: Delphacidae ARSEF 490 KM652151 KM652103 KM651987
H. citriformis (Cixiidae) Hemiptera: Cixiidae ARSEF 1035 KM652153 KM652105 KM652064 KM652030 KM651989
H. citriformis (Psyliidae) Hemiptera: Psyllidae ARSEF 2598 KM652155 KM652107 KM651991
H. cryptosclerotium Hemiptera: Pseudococcidae ARSEF 4517 KM652157 KM652109 KM652066 KM652032 KM651992
H. flava Lepidoptera: GZUIFR-hir100627-1 KY415598 KY415599 KY945366 KY415601
Lepidoptera: GZUIFR-hir100627-2 MF623036 MF623042 MF623046
Lepidoptera: GZUIFR-hir100627-3 MF623037 MF623043 MF623047
H. fusiformis Coleoptera: Curculionidae ARSEF 5474 KM652110 KM652067 KM652033 KM651993
H. guyana Hemiptera: Cicadellidae ARSEF 878 KM652158 KM652111 KM652068 KM652035 KM651994
H. haptospora Acari: Uropodina ARSEF 2226 KM652159 KM652036 KM651995
H. illustris Hemiptera: Aphididae ARSEF 5539 KM652160 KM652112 KM652069 KM652037 KM651996
H. kirchneri Acari: Eriophyidae ARSEF 5551 KM652161 KM652113 KM652070 KM651997
H. kuankuoshuiensis Lepidoptera: GZUIFR 2012KKS3-1 KY415575 KY415582 KY945360 KY415590
Lepidoptera: GZUIFR 2012KKS3-2 MF623038 MF623044 MF623048
Lepidoptera: GZUIFR 2012KKS3-3 MF623039 MF623045 MF623049
H. leizhouensis Lepidoptera: Pyralidae GZUIFR-hir140506 KY415573 KY415580 KY415587
H. lecaniicola Hemiptera: Coccidae ARSEF 8888 KM652162 KM652114 KM652071 KM652038 KM651998
H. liboensis Lepidoptera: Cossidae ARSEF 9603 KM652163 KM652115 KM652072
H. necatrix Acari ARSEF 5549 KM652164 KM652116 KM652073 KM652039 KM651999
H. nodulosa Lepidoptera: Pyralidae ARSEF 5473 KM652165 KM652117 KM652074 KM652040 KM652000
H. radiata Diptera ARSEF 1369 KM652119 KM652076 KM652042 KM652002
H. repens nom. inval. Hemiptera: Delphacidae ARSEF 2348 KM652167 KM652120 KM652077 KM652003
H. rhossiliensis (Heteroderide) Tylenchida: Heteroderidae ARSEF 2931 KM652168 KM652121 KM652078 KM652043 KM652004
H. rhossiliensis Tylenchida: Criconematidae ARSEF 3747 KM652170 KM652123 KM652080 KM652045 KM652006
H. satumaensis Lepidoptera: Pyralidae ARSEF 996 KM652172 KM652125 KM652082 KM652047 KM652008
H. sinensis Lepidoptera: Hepialidae ARSEF 6282 KM652173 KM652126 KM652083 KM652048 KM652009
H. strigosa (Cicadellidae) Hemiptera: Cicadellidae ARSEF 2197 KM652175 KM652129 KM652085 KM652050 KM652012
H. strigosa (Delphacidae) Hemiptera: Delphacidae ARSEF 2044 KM652174 KM652128 KM652011
H. subulata Lepidoptera: Microlepidoptea ARSEF 2227 KM652176 KM652130 KM652086 KM652051 KM652013
H. thompsonii (Eriophyidae) Acari: Eriophyidae ARSEF 253 KM652179 KM652133 KM652088 KM652016
H. thompsonii (Tetranychidae) Acari: Tenuipalpidae ARSEF 3323 KM652188 KM652143 KM652096 KM652059 KM652024
H. thompsonii var. synnematosa Acari: Tetranychidae ARSEF 5412 KM652193 KM652148 KM652100
H. thompsonii var. thompsonii Acari: Eriophyidae ARSEF 137 KM652177 KM652131 KM652087 KM652052 KM652014
H. versicolor Hemiptera: Membracidae ARSEF 1037 KM652150 KM652102 KM652063 KM652029
Ophiocordyceps acicularis Coleoptera OSC 110988 EF468804 EF468951 EF468853 EF468745
O. agriotidis Coleoptera ARSEF 5692 JN049819 DQ518754 DQ522540 DQ522368 DQ522322
O. aphodii Coleoptera ARSEF 5498 DQ518755 DQ522541 DQ522323
O. appendiculata Coleoptera NBRC 106960 JN943326 JN941413 JN941728 JN992462 AB968577
O. brunneipunctata Coleoptera (Elateridae) OSC 128576 DQ518756 DQ522542 DQ522369 DQ522324
O. clavata Coleoptera NBRC 106962 JN943328 JN941415 JN941726 JN992460 AB968587
O. cochlidiicola Insect HMAS199612 AB027377 KJ878884 KJ878917 KJ878998 KJ878965
O. communis Coleoptera NHJ 12581 EF468831 EF468973 EF468775
O. dipterigena Diptera (adult fly) OSC 151912 KJ878887 KJ878920 KJ879001 KJ878967
O. elongata Lepidoptera (larva) OSC 110989 EF468808 EF468856 EF468748
O. entomorrhiza Lepidoptera KEW 53484 JN049850 EF468809 EF468954 EF468857 EF468749
O. evansii Hymenoptera (Pachycondylaharpax) Ophsp 858 KC610770 KC610796 KP212916 KC610736
O. forquignonii Diptera (adult fly) OSC 151908 KJ878889 KJ878922 KJ879003
O. geometridicola Lepidoptera (Geometridae) TBRC 8095 MF614648 MF614663 MF614632
O. gracilis Lepidoptera (larva) EFCC 8572 JN049851 EF468811 EF468956 EF468859 EF468751
O. heteropoda Hemiptera (cicada nymph) OSC 106404 AY489722 AY489690 AY489651 AY489617
O. irangiensis Hymenoptera (adult ant) OSC 128579 EF469076 EF469123 EF469089 EF469060
O. konnoana Coleoptera (larva) EFCC 7315 EF468959 EF468861 EF468753
O. lanpingensis Hepialus (larva) YHOS0707 KC417461 KC417459 KC417465 KC417463
O. lloydii Hymenoptera (Camponotus) OSC 151913 KJ878891 KJ878924 KJ879004 KJ878970
O. macroacicularis lepidopterans (larvae) NBRC 105888 AB968401 AB968417 AB968389 AB968575
O. melolonthae Coleoptera (Scarabeidae larva) OSC 110993 DQ518762 DQ522548 DQ522376 DQ522331
O. multiperitheciata Lepidoptera (larva) BCC 69008 MF614657 MF614641
O. myrmicarum Formicidae (adult ant) ARSEF 11864 KJ680150 KJ680151 JX566973
O. nigrella Lepidoptera (larva) EFCC 9247 JN049853 EF468818 EF468963 EF468866 EF468758
O. pauciovoperitheciata Lepidoptera (larva) TBRC 8106 MF614652 MF614633
O. pseudoacicularis Lepidoptera (larva) TBRC 8102 MF614646 MF614661 MF614630
O. ramosissimum Lepidoptera (larva) GZUHHN8 KJ028007 KJ028012 KJ028017 KJ028014
O. robertsii Lepidoptera (Hepialidae larva) KEW 27083 EF468826 EF468766
O. sinensis Lepidopteran pupa EFCC7287 JN049854 EF468971 EF468874 EF468767
O. sporangifera Lepidoptera (Cossidae) MFLUCC 18-0492 MH725818 MH725832 MH725814 MH727392 MH727390
O. stylophora Coleoptera (Elateridae larva) OSC 111000 JN049828 DQ518766 DQ522552 DQ522382 DQ522337
O. xuefengensis Lepidoptera (Hepialidae larva) GZUH2012HN11 KC631803 KC631788 KC631799 KC631794
Tolypocladium inflatum Coleoptera (larva) OSC 71235 JN049844 EF469077 EF469124 EF469090 EF469061
T. ophioglossoides Fungi (Elaphomyces sp.) NBRC 106332 JN943322 JN941409 JN941732 JN992466

All the sequences were edited for multi-alignment using the BioEdit Sequence Alignment Editor v.7.0.5.3 (Hall 1999) with the Clustal X v.1.83 software package (Thompson et al. 1999). Gaps were excluded from the phylogenetic analysis based on previous research (Qu et al. 2018). The ITS, SSU, LSU, TEF1α and RPB1 regions were aligned in combined datasets using MAFFT v.7 (Katoh and Standley 2013, http://mafft.cbrc.jp/alignment/server/). The Akaike Information Criterion (AIC) in jModeltest 0.1.1 (Guindon and Gascuel 2003; Posada 2008) was used to select the nucleotide substitution model for each region. The combined data included a 4778 bp character set of the five regions and were analysed. Maximum likelihood phylogenetic analyses were conducted in RAxML (Stamatakis et al. 2008) with the recommended partition parameters to determine the best tree topology. The bootstrap support values were achieved after 500 search replicates and summarised in TreeGraph. Bayesian Posterior Probabilities (BPP) were estimated in MrBayes 3.1.2 (Ronquist and Huelsenbeck 2003) with the same partition parameters. In this analysis, two runs of four chains each were executed simultaneously for 5,000,000 generations, with sampling every 500 generations. TreeGraph was used to compute the BPP from a summary of 7,501 trees retained after a burn-in of the first 2,500 trees collected.

Results

Phylogenetic analyses

The tree was constructed with maximum likelihood and Bayesian posterior probabilities with Tolypocladium inflatum and T. ophioglossoides as the outgroup taxa based on RPB1, tef1, ITS, 18S rDNA and 28S rDNA gene datasets (SSU: 1391 bp, LSU: 903 bp, ITS: 721 bp, TEF1α: 946 bp and RPB2: 817 bp) (Fig. 1). In this phylogenetic tree, Hirsutella flava and H. kuankuoshuiensis formed a separate clade from the other species with credible bootstrap values (85% ML and 0.90 PP), suggesting that these two species are truly related. Within a separate branch, H. flava and H. kuankuoshuiensis were allied with the H. sinensis and H. strigosa clade, distant from the other hirsutella-like species, particularly the H. thompsonii clade. A molecular phylogenetic analysis further confirmed the differences among the two new species and other related species. Based on the morphological characteristics and molecular phylogenetic analysis, these two new species are introduced as new members of Hirsutella species in the Ophiocordycipitaceae family.

Figure 1. 

Phylogenetic tree of Hirsutella species combined with RPB1, tef1, ITS, 18S rDNA and 28S rDNA datasets, using the maximum likelihood method. Numbers below the branches are bootstrap percentage values, based on 10,000 replicates, ML/BPP.

Taxonomy

Hirsutella flava X. Zou, J.J. Qu, Z.A. Chen & Z.Q. Liang, sp. nov.

MycoBank No: 819552
Fig. 2

Diagnosis

Characterised by phialides slender awl-shaped and tapered; a width of base 24–40.8 × 2.2–2.5 μm; tapering to narrow neck, 7.2–9 μm long × 0.5 μm wide. Conidia narrow cymbiform, long fusoid or limoniform, 6.5–10 × 2.1–4.3 μm.

Type

China, Zhejiang Province, Tianmu Mountain National Nature Reserve (30°18'N, 119°28'E, approximately 600–1200 m a.s.l.), 27 June 2010, presented by Prof. Zhuan Chen. The holotype has been deposited at KIB (HKAS112884). Sequences from isolated strains (GZUIFR-hir100627-1, GZUIFR-hir100627-2 and GZUIFR-hir100627-3) have been deposited in GenBank.

Description

Synnemata extending from the head of insect, 3–10 cm × 0.5–1 mm, simple or irregularly branched, dark brown and changing to faint yellow toward the apex; no conidiation was observed (Fig. 2A). The fungus grows slowly at 22 ± 1 °C on Czapek-Dox agar medium to a diam. of 8–12 mm; the colony surface was flat and flocculent with white aerial hyphae. On PDA agar, fungal colonies grew quickly to a diam. of 15–23 mm after 20 d at 22 ± 1 °C, when the colonies were blanket-like with rough mycelia, radiating beam-like from the centre; centre lunate concave, pale yellow; colony surface with yellowish liquid exudation (Fig. 2B, C). Mycelium hyaline, smooth, septate, 3.6–4.5 μm wide. Conidiogenous cells form directly from the mycelial end, monophialidic or polyphialidic, and borne perpendicular or at acute angles (80°–85°) to the subtending hyphae. Phialides slender awl-shaped and tapered, width of the base 24–40.8 × 2.2–2.5 μm, tapering to a narrow neck, 7.2–9 μm long × 0.5 μm wide. Conidia narrow cymbiform, long fusoid or limoniform, 6.5–10 × 2.1–4.3 μm; single- or double-enveloped in a hyaline mucus, thickness 2.0–3.0 μm (Fig. 2D–K).

Figure 2. 

Morphological characteristics of Hirsutella flava A the infected insect specimens with a long and single synnemata (HKAS112884) B, C colonial morphology on PDA agar media for 20 d B shows the front of the colony and C shows the back of the colony D–G LM images of the general morphology of conidiogenous cells and conidia H–K SEM images showing conidiogenous cells and conidial structure; Scale bars: 1 cm (A); 5 cm (B, C), 10 μm (D–G); the rest of the bars are shown in the figure. LM, light microscopy; PDA, potato dextrose agar; SEM, scanning electron microscopy.

Host

Larva of a species of Lepidoptera.

Habitat and distribution

On decaying leaves in broadleaved forests, Zhejiang Province, China.

Etymology

Refers to the yellow colour (Lat. ‘flava’) of the holotype and colony.

Teleomorph

Unknown.

Remarks

This species is allied with the H. sinensis and H. strigosa clade. The phialides of H. flava are subulate, and the necks are slenderer. In particular, the colony morphology of this fungus is unique among the Hirsutella species. The colony surface appears very rough, and the hyphae are gathered into outwardly radiating filamentous bundles of varying sizes.

Hirsutella kuankuoshuiensis X. Zou, J.J. Qu & Z.Q. Liang, sp. nov.

MycoBank No: 819591
Fig. 3

Diagnosis

Hirsutella kuankuoshuiensis differs from other species in this genus primarily by its clavate, narrow fusiform or botuliform conidia and subulate or slender columnar phialide.

Type

China, Guizhou Province, Suiyang County, Kuankuoshui Nature Reserve (28°08'N, 107°02'E, approximately 1400 m a.s.l.), July 2012, collected by X. Zou. The holotype has been deposited at KIB (HKAS112885). Sequences from isolated strains (GZUIFR-2012KKS3-1, GZUIFR-2012KKS3-2 and GZUIFR-2012KKS3-3) have been deposited in GenBank.

Description

Synnemata are single, extending from the head of insect; 8.6 cm long, dark brown and changing to brown towards the apex; no conidiation was observed (Fig. 3A). The fungus spreads slowly on PDA agar at 20–22 °C and grows to a diam. of 22–30 mm after 14 d; the colony is round, centre of surface with brown dense bulges and grey-white sparse flocculent aerial hyphae. Colony margin is flat with radial groove; a large amount of brown pigment secreted into the medium causes the back of colony to appear dark brown; thickness 10–12 mm (Fig. 3B, C). Mycelium hyaline, smooth, septate, 1.5–3.0 μm wide. Conidiogenous cells monophialidic, hyaline, borne perpendicular or at an acute angle to the subtending hyphae. Phialides subulate or slender columnar, tapering gradually to a long and narrow neck, 30–45 × 1–3 μm long. Conidia clavate, narrow fusiform or botuliform without a diaphragm, 9.9–12.6 × 2.7–4.5 μm, single- or double-enveloped in a hyaline mucus, thickness 2.0–3.0 μm (Fig. 3D–J).

Figure 3. 

Morphological characteristics of Hirsutella kuankuoshuiensis A the insect specimens with single and thin synnemata (HKAS112885) B, C colonial morphology on PDA agar media for 20 d B shows the front of the colony and C shows the back of the colony D–G LM images showing conidiogenous cells and conidia D, E the structure of conidiogenous cells on mycelia F the images of conidiogenous cells on synnemata (optical microscope) H–J conidial morphology (LM) G conidia with mucilage (SEM). Scale bars: 10 mm (A–C); bar of G was shown in the figure; the rest of the bars were 10 μm. LM, light microscopy; PDA, potato dextrose agar; SEM, scanning electron microscopy.

Etymology

Referring to the locality of the specimen, kuankuoshui (Lat. ‘kuankuoshuiensis’).

Host

Lepidoptera larva.

Habitat and distribution

On the decaying leaves of broadleaved forests, Guizhou Province, China.

Teleomorph

Unknown.

Remarks

This species possesses two types of conidiogenous cells and long fusiform or clavate without diaphragm conidia (9.9–12.6 × 2.7–4.5 μm), which is extremely rare in Hirsutella species. In addition, H. kuankuoshuiensis could produce long thin synnemata on the culture media that contain few or no conidia.

Discussion

Previous taxonomic studies have shown that the Hirsutella species are reconstructed in five main groups, and clustering taxa shared the same phialide structures (Simmons et al. 2015b; Qu et al. 2017; Qu et al. 2018). In general, the H. nodulosa lineage possesses phialides with apical helical twists. The H. citriformis clade is primarily represented by a squat ovoid base and a single slender neck. The H. thompsonii clade, the most widely studied hirsutella-like species and a potential biocontrol agent for mite pests, has a small cylindrical or round phialide, usually less than 25 μm, while the H. sinensis clade includes isolates that originate from a variety of taxa, including nematodes, mites and both hemi (Hemiptera) and holometabolous (Coleoptera, Lepidoptera) insect hosts (Simmons et al. 2015b). The majority of these species share a cylindrical base and an average phialide length greater than 40 μm. In our phylogenetic tree, these five typical branches of Hirsutella were more dispersed owing to the addition of more Ophiocordyceps species. Hirsutella flava and H. kuankuoshuiensis formed a separate clade that is represented by the subulate phialides and narrow fusiform conidia and have a close relationship with the H. sinensis and H. strigosa clades. In addition, this separate clade is distant from the H. thompsonii and H. citriformis clades. Species in these clades primarily share similarly large phialides and long fusiform conidia (Qu et al. 2018).

The phylogenetic tree confirmed the distinction between two new species and extant species. Among the species with an awl-shaped base and a long narrow neck, H. flava differs in its subulate phialides (e.g. H. danubiensis Balazy et al., 2008; H. tunicate Ciancio et al., 2013), cylindrical phialides (e.g. H. changbeisanensis Liang, 1991; H. strigosa Petch, 1939) and two types of conidiogenous cells (e.g. H. stilbelliformis Evans & Samson, 1982; H. shennongjiaensis Zou et al., 2016b) (Suppl. material 1: Table S2). In addition, H. flava is unique in the colony morphology of isolated strains. The fungus spreads more quickly than other hirsutella-like species on PDA media, and the colony surface appears very rough, owing to the hyphae being gathered into outwardly radiating filamentous bundles of varying sizes. H. flava could be distinguished from similar species by the shape and size of the conidiogenous cells. Morphological comparisons of relevant taxa are shown in Suppl. material 1: Table S2.

Hirsutella kuankuoshuiensis possesses two types of conidiogenous cells and long fusiform or clavate conidia, which are unique to Hirsutella. Furthermore, this species can readily produce long thin synnemata on culture media, but it produces few or no conidia. There are five other species similar to this species: H. shennongjiaensis (Zou et al. 2016), H. stilbelliformis var. stilbelliformis (Evans and Samson 1982), H. sporodochialis (Evans and Samson 1984), H. subramanianii (Samson and Evans 1985), and H. zhangjiajiensis (Liang et al. 2005). Among them, the conidia of H. shennongjiaensis are primarily rod-like and slender; H. stilbelliformis var. stilbelliformis has a larger base with thorny phialides, greater than 50 μm long; H. sporodochialis has longer conidia; H. subramanianii has hymenopteran hosts and thinner stick-shaped conidia, 10–13.5 × 1.8–2.5 μm; and H. zhangjiajiensis conidia are lanceolate or resemble an orange segment (Suppl. material 1: Table S3). Within the framework of the available data for the genus, the phylogenetic tree and the morphological analysis confirmed the status of Hirsutella flava and H. kuankuoshuiensis as new species.

Acknowledgements

We would like to thank Professor Zhuan Chen for presenting us with the specimen HKAS112884. This work was supported by the National Natural Science Foundation of China (No. 32060038, 31860037), the Science and Technology Project of Guizhou Province ([2021]080, [2020] 1Z009), and the Talent Fund of Guizhou University (2019)10.

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Supplementary material

Supplementary material 1 

Tables S1–S3. A total of 71 taxa were selected to represent the morphological and ecological diversity of Hirsutella asexual morphs and Ophiocordyceps

Jiaojiao Qu, Xiao Zou, Wei Cao, Zhongshun Xu, Zongqi Liang

Data type: phylogenetic data

Explanation note: The GenBank accession numbers of all species are shown in Table 1.

This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited.
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