Huntiella

Z.W. de Beer, et al., Stud. Mycol. 79: 211. 2014. Fig. 24.

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Fig. 24. Huntiella spp. A–D. Disease symptoms. A. Eucalyptus trees artificially wounded to trap Huntiella spp. B. Lesion associated with inoculation with Huntiella sumatrana on an Acacia mangium stem. C. Discolouration of wood associated with artificially induced wound on the stem of a Eucalyptus tree from which Huntiella spp. were isolated. D. Blue-stained Eucalyptus wood associated with Huntiella infection. E–H, L. Sexual morphs. E. Ascomata on 2 % MEA in various developmental stage from young (paler) to mature (darker). F. Mature ascomata with fresh ascospore droplets at the tip of necks and ostiolar neck with a disc-like base (arrow). G, H. Young ascoma showing developing of conical spines (G) and ascomatal hyphae (H). L. Ascospores. I–K. Asexual morphs. I. Tubular-form conidiogenous cell producing barrel-shaped conidia. J. Flask-shaped conidiogenous cells producing rectangular-shaped conidia. K. Rectangular-shaped conidia. E, F, H, K. Huntiella omanensis (CMW 11056). G, L. Huntiella moniliformis (CMW 36908). I, J. Huntiella abstrusa (CMW 21092). Scale bars: E = 500 μm; F = 250 μm; G, H = 50 μm; I–L = 10 μm.

Classification: Sordariomycetes, Hypocreomycetidae, Microascales, Ceratocystidaceae.

Type species: Huntiella moniliformis (Hedgc.) Z.W. de Beer, et al., basionym: Ceratostomella moniliformis Hedgc. Holotype: BPI 595959.

DNA barcodes (genus): LSU, 60S, mcm7.

DNA barcodes (species): ITS, mcm7, tef1, tub2. Table 8. Fig. 25.

Table 8. DNA barcodes of accepted Huntiella spp.

Species	Isolates1	GenBank accession numbers2				References
		ITS	tub2	mcm7	tef1
Huntiella abstrusa	CBS 142243T	KY913291	KY913290	KY913289	–	Present study
Hu. bhutanensis	CBS 114289T	AY528952 NR119506	AY528962	KM495412	AY528962a	Van Wyk et al., 2004, De Beer et al., 2014
Hu. ceramica	CBS 122299T	EU245022	EU244994	KM495485	EU244926b	Heath et al., 2009, De Beer et al., 2014
Hu. chinaeucensis	CBS 127185T	JQ862729	JQ862717	KM495416	JQ862741c	Chen et al., 2013, De Beer et al., 2014
Hu. cryptoformis	CBS 131279T	KC691464	KC691488	–	KC691512c	Mbenoun et al. (2014)
Hu. decipiens	CBS 129736T	HQ203216	HQ203233	KM495422	HQ236435c	Kamgan Nkuekam et al., 2013, De Beer et al., 2014
Hu. inquinans	CBS 124388T	EU588587	EU588666	KM495436	EU588674a	Tarigan et al., 2010, De Beer et al., 2014
Hu. microbasis	CBS 124013T	EU588593	EU588672	KM495442	EU588680a	Tarigan et al., 2010, De Beer et al., 2014
Hu. moniliformis	CBS 118127	FJ151422	FJ151456	KM495443	FJ151478a	Van Wyk et al., 2011, De Beer et al., 2014
Hu. moniliformopsis	CBS 109441T	AY528998	AY528987	KM495444	AY529008a	Yuan and Mohammed, 2002, Van Wyk et al., 2004, De Beer et al., 2014
Hu. oblonga	CBS 122291T	EU245019	EU244991	KM495447	EU244951b	Heath et al., 2009, De Beer et al., 2014
Hu. omanensis	CBS 115787	DQ074742	DQ074732	KM495449	DQ074737a	Al-Subhi et al. (2006)
Hu. salinaria	CBS 129733T	HQ203213	HQ203230	KM495461	HQ236432c	Kamgan Nkuekam et al., 2013, De Beer et al., 2014
Hu. savannae	CBS 121151T	EF408551	EF408565	KM495462	EF408572c	Kamgan et al., 2008, De Beer et al., 2014
Hu. sublaevis	CBS 122517	FJ151431	FJ151465	KM495464	FJ151486b	Van Wyk et al., 2011, De Beer et al., 2014
Hu. sumatrana	CBS 124011PT	EU588589	EU588668	KM495465	EU588678a	Tarigan et al., 2010, De Beer et al., 2014
Hu. tribiliformis	CBS 115866T	AY529003	AY529003	KM495468	AY529014a	Van Wyk et al., 2006, De Beer et al., 2014
Hu. tyalla	CBS 128703T	HM071900	HM071913	KM495470	HQ236452c	Kamgan Nkuekam et al., 2012, De Beer et al., 2014

1

CBS: Westerdijk Fungal Biodiversity Institute, Utrecht, the Netherlands. ^T and ^PT indicate ex-type and ex-paratype strains, respectively.

2

ITS: internal transcribed spaces and intervening 5.8S nrDNA, tub2: partial β-tubulin gene, mcm7: mini-chromosome maintenance complex component 7, tef1: partial translation elongation factor 1-alpha gene. ^{a, b} and ^c in tef1 column indicate the primers used in sequencing: a: Ef1-728f, ef1-986r, b: EF1f, EF1r, c:EF1f, EF2r.

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Fig. 25. A maximum likelihood (ML) phylogram constructed using the combined dataset of the 60S (370 bp), LSU (813 bp), ITS (393 bp), mcm7 (589 bp) and tub2 (433 bp) gene regions of Huntiella spp. ML analyses were performed using PhyML with Smart Model Selection Online, selecting the GTR substitution model. Bootstrap values of 70 % or more are indicated above the branches. The newly described species, Hu. abstrusa, is indicated in bold. TreeBASE: S20860.

Ascomata perithecial, ellipsoidal, subglobose, globose to obpyriform or ovoid; bases ornamented with dark brown to black conical spines or pale brown, unbranched hyphae; necks long, straight or slightly curved, tapering towards apex, dark brown to black at base, becoming paler towards apex, ostiolate, with a disciform base; hyphae on neck hyaline, not divergent, straight or convergent. Asci evanescent. Ascospores hyaline, aseptate, in face view subglobose, in side view ellipsoidal giving an impression of a hat, with hood-like gelatinous sheath. Conidiophores macronematous, rarely branched, septate, occasionally reduced to conidiogenous cells. Conidiogenous cells hyaline, enteroblastic, mostly of two types, lageniform, producing rectangular-shaped conidia and cylindrical, producing barrel-shaped conidia. Conidia aseptate, majority of species have two distinct shapes: bacilliform, hyaline, or barrel-shaped or oblong to ellipsoidal, hyaline or subhyaline. Chlamydospores absent.

Culture characteristics: On 2 % MEA aerial mycelium abundant, colonies white, yellow green to brown, smoke grey, dark olive to black. Some species produce aromas: Hu. bhutanensis produces an unpleasant rotten odour, Hu. decipiens, Hu. moniliformis and Hu. salinaria a pleasant banana-oil aroma, Hu. moniliformopsis little to no distinct odour, and Hu. omanensis fruity aroma that turns to a fermented odour with age.

Optimal media and cultivation conditions: On 2 % MEA in dark, optimum growth varies between species: Hu. sublaevis 20–30 °C; Hu. bhutanensis, Hu. oblonga, Hu. ceramica and Hu. tribiliformis 20–25 °C; Hu. decipiens, Hu. chinaeucensis, Hu. inquinans, Hu. microbasis, Hu. salinaria and Hu. sumatrana 25–30 °C; Hu. cryptoformis, Hu. omanensis, Hu. savannae and H. tyalla 30–35 °C.

Distribution: Australia, Bhutan, China, Ecuador, Indonesia, Malawi, Oman, South Africa and Tasmania.

Hosts: Acacia (Fabaceae), Combretum and Terminalia (Combretaceae), Eucalyptus (Myrtaceae), Mangifera (Anacardiaceae) associated with Cryphalus scabricollis (bark beetle, Scolytinae), Picea (Pinaceae) infested with Ips schmutzenhoferi (bark beetle, Scolytinae), Pinus (Pinaceae), Ziziphus (Rhamnaceae), and Staphilinid (rove beetle, Staphylinidae).

Disease symptoms: Huntiella species do not produce distinct disease symptoms on their hosts in nature. They usually infect freshly made wounds on trees and infections are often associated with nitidulid beetles (Coleoptera: Nitidulidae) and flies (Diptera). Pathogenicity tests using some of the species have given rise to lesions under controlled environments, but, based on the size of lesions and failure to re-isolate the fungus from these lesions, they are generally considered not to be primary pathogens (Tarigan et al., 2010, Van Wyk et al., 2011, De Beer et al., 2014).

Notes: Huntiella is one of nine genera in the recently erected family, Ceratocystidaceae (De Beer et al., 2014, Mayers et al., 2015, Nel et al., 2018). The genus was proposed to accommodate Ceratocystis moniliformis and related species that form a well-defined monophyletic lineage within the group previously treated as Ceratocystis sensu lato (Wingfield et al. 2013). Huntiella currently includes 17 species.

 Species of Huntiella have several features in common, namely conical spines on their ascomatal bases, disk-like structures at the bases of the ascomatal necks, which break off easily, hat-shaped ascospores and one to two types of conidia (De Beer et al. 2014). Although morphological and culture characteristics overlap between the species, some species can be differentiated. These include Hu. sublaevis that has a limited number of spines on the ascomata (Van Wyk et al. 2011), and Hu. chinaeucensis and Hu. microbasis that have only rectangular-shaped conidia (Tarigan et al., 2010, Chen et al., 2013). With the exception of Hu. ceramica that is known only from the asexual morph, all other species have both sexual and asexual morphs. Different Huntiella species exhibit a variety of sexual strategies, with Hu. omanensis undergoing heterothallic mating while MAT2 isolates of Hu. moniliformis are able to reproduce unisexually (Wilson et al. 2015).

References: Kamgan et al., 2008, Heath et al., 2009, Tarigan et al., 2010, Kamgan Nkuekam et al., 2012, Chen et al., 2013, Kamgan Nkuekam et al., 2013 (pathogenicity); De Beer et al. 2013a (higher classification); De Beer et al. 2013b (nomenclature); Wingfield et al., 2013, De Beer et al., 2014 (generic definitions and phylogenetic relationships); Wilson et al. 2015 (mating strategies).

Huntiella abstrusa

A.M. Wilson, Marinc., M.J. Wingf., sp. nov. MycoBank MB821072. Fig. 26.

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Fig. 26. Huntiella abstrusa (ex-type CBS 142243 = CMW 21092). A. Ascomata on host substrate. B. Ascospore droplets of cream to yellow-coloured at the tip of ascomatal neck and ascomata embedded in aerial hyphae producing asexual structures. C. Colony on 2 % MEA grown in the dark at 30 °C for 3 d. D. Mature ascoma with a disk-like base (arrow). E. Base of young ascoma (1 wk) with conical spines (arrow) (image taken in bright field). F. Ascospores. G. Two types of conidia: rectangular-shaped and barrel-shaped conidia. H. Flask-shaped conidiogenous cells and rectangular-shaped conidia. I. Tubular-shaped conidiogenous cell and barrel-shaped conidia. Scale bars: B = 500 μm; D = 100 μm; E = 50 μm; F–I = 10 μm.

Etymology: Name refers to the fact that this cryptic species was obscured by the name Ceratocystis moniliformis for more than a decade.

On MEA: Ascomata 145–315 × 130–275 μm, perithecial, embedded in media or superficial in mycelial mass, single or in groups, pale brown when young, becoming dark brown with age, ellipsoidal to subglobose; ascomatal wall of textura epidermoidea to textura globulosa, covered with short sterile hyphae, 30–105 μm long, hyaline becoming pale brown with age, mostly unbranched, flexuous, tapering towards apex, with conical spines; necks 595–1100 μm long, 21–71.5 μm wide near base, 11–18 μm wide near apex, dark brown, tapering towards apex, becoming easily detached from ascomatal base when pressed, with a disk-like structure near base; hyphae near apex 18.5–37 μm long, 1–2 μm wide near base, 0.5–1.5 μm wide, mostly straight, showing no distinct divergent nor convergent, aseptate, unbranched, hyaline, tapering towards apex. Asci not observed. Ascospores 4.5–5.5 × 3.5–6 μm (av. 5.2 × 4.6 μm) without sheath, 2–3.5 μm thick in side-view, hyaline, oblong to subglobose, clothed with gelatinous sheath, 0.5–1.5 μm thick, in side-view giving an impression of a hat. Conidiophores up to 80 μm long, septate, flexuous, sometimes branched, occasionally reduced to conidiogenous cells, often lightly sub-hyaline to pale brown near base. Conidiogenous cells hyaline, enteroblastic, in two shapes, originating from same or different hyphae; lageniform, 15.5–33 μm long, 2–4.5 μm wide at base, gradually tapering towards apex, 1–3 μm wide at apex, producing rectangular conidia; or cylindrical with wide-mouthed, 22–50 μm long, 3.5–6.5 μm wide at apex, 3–4 μm wide at base, producing barrel-shaped conidia. Conidia in chains, hyaline, aseptate, in two shapes, rectangular, 4–8.5 × 1.5–2.5 μm (av. 5.6 × 1.8 μm); or barrel-shaped, 5–14.5 × 4–7 μm (av. 8.1 × 5.9 μm). Chlamydospores absent.

Culture characteristics: On 2 % MEA optimum growth at 30 °C reaching 82.7 mm in dark in 3 d, followed by 25 °C reaching 77.3 mm, showing slow growth at 10, 15, 20, 35 °C. Cultures circular with smooth margins, aerial mycelium fluffy to velvety, moderately dense, above and below dark brown fading towards edge and with white margins.

Material examined: Indonesia, Riau province, Teso East, S 0°04’33.00”, E 101°37’23.00”, on the bark of Eucalyptus sp. (Myrtaceae), Oct. 2005, M. Tarigan (holotype PREM 61671, culture ex-type CBS 142243 = CMW 21092).

Notes: For more than a decade, Hu. abstrusa was thought to be Ceratocystis moniliformis (now Hu. moniliformis). Phylogenetic analyses of ITS, LSU, 60S, mcm7 and tub2 have shown that Hu. abstrusa is distinct from Hu. moniliformis and other Huntiella spp. It is most closely related to Hu. inquinans, Hu. microbasis and Hu. sumatrana from Indonesia, Hu. chinaeucensis from China and Hu. bhutanensis from Bhutan (De Beer et al., 2014, Van Wyk et al., 2004, Tarigan et al., 2010, Chen et al., 2013). Neither Hu. abstrusa nor any of the other Huntiella species are primary pathogens and typically infect freshly made wounds on trees. Despite only minor morphological differences between Huntiella species, Hu. abstrusa can be distinguished from the other species by its longer necks and the presence of barrel-shaped conidia. The Hu. abstrusa isolate examined is considered heterothallic.

Authors: A.M. Wilson, S. Marincowitz, M.J. Wingfield & B.D. Wingfield