Trichobelonium albobarbatum Itagaki & Hosoya, 2023

Itagaki, Hiyori & Hosoya, Tsuyoshi, 2023, A new genus Neobelonopsis and two new species of Trichobelonium (Helotiales, Ascomycota) discovered mainly from poaceous grasses native to Asia in Japan, MycoKeys 99, pp. 45-85 : 45

Trichobelonium albobarbatum Itagaki & Hosoya sp. nov.

Figs 11 , 13 , 14H

Etymology.

Named after the anchoring hyphae between the cortical cells of receptacle and subiculum, which resembles a white beard (albo and barbata in Latin, respectively).

Diagnosis.

Resembles T. kneiffii , but distinguished by its larger ascospores.

Holotype.

TNS-F-86430, Sawara Pond, Asahi Town, Nirasaki City, Yamanashi Pref., 14 June 2021, on decaying poaceous grass culm lying on the wet ground close to the pond, ex-holotype culture NBRC 115568.

Description.

Apothecia developed scuta. Scuta superficial, scattered to gregarious, flat to protruded discoid, 125-375 µm diam., blackish brown (C80M100Y80-100K60), textura epidermoidea. Apothecia sessile, globose to pulvinate when immature, discoid to saucer-shape when mature, flat to concave when fresh, doliiform to pulvinate when dried, 0.1-0.3 mm high, with brown (C40-80M80Y100K30) receptacle; disc 0.5-1.5 mm diam., entire to undulate, without hairs at margin, waxy, yellow (Y30-60) when fresh, shrunk to 0.2-1 mm diam., pulverulent, yellowish orange (M10-40Y80-100) when dried, turned to brown (C30-60M80Y80-100) with senescence. Ectal excipulum 30-40 µm thick at base, 20-30 µm thick at the upper flank to margin, textura globulosa and angularis, composed of 2-4 layers of brown thick-walled cells; cortical cells hemispherical, 10-15(-17) × 6-10(-12) µm, ending up in cylindrical clavate cells, thick-walled, paler toward the margin; anchoring hyphae connecting the cortical cells of the flank and subiculum, radially extending from apothecium, 2.5-3 µm width, septate every 20-35 µm, thin-walled, hyaline, becoming conspicuous when apothecia dried. Medullary excipulum 100-150 µm thick, textura intricata to prismatica, hyaline, containing crystals below giving a rough texture, composed of loosely interwoven thin-walled hyphae which is frequently dichotomously branching. Asci (75-)85-100(-107) × 12-16(-20) µm, cylindrical-clavate to saccate, 8-spored, arising from croziers, containing yellowish oil globules in cytoplasm that disappear when mature, with a thick-walled conical apex; apex MLZ+ with or without 3% KOH pretreatment. Ascospores (25-)30-35(-38) × 4.5-6 µm, fusiform-clavate, with rounded or subacute extremes, straight to sigmoid curved, thin-walled, (0-)3-septate, sometimes constricted at the septum, hyaline, with numerous guttules. Paraphyses 85-100(-115) × 2.5-4.5 µm, occasionally branching at base, cylindrical, often becoming slightly wider toward the apex, 2-3-septate, thin-walled, hyaline, containing fragmented refractive vacuoles when mounted fresh in water. Subiculum covering the surface of substrates in patches, sparse to especially abundant around the apothecia and scuta, shiny dark brown, consisting of 1-3 layers of closely packed subicular hyphae; subicular hyphae 2-5 µm diam., thick-walled, brown. Colony of NBRC 115568 on PDA entire to partially filamentous at the margin, flat to slightly convex with aerial hyphae, cottony to woolly, agate (C10-30M60Y60) to amber (C10-40M100Y60K60) from the surface, appearing maroon (C10-40M100Y60K60) from reverse, with apricot (M20-40Y60) soluble pigment uniformly diffuse in agar; crystals aggregating plate-like or small clusters, acicular, moderately abundant on colony surface and surrounding agar, 0.1-0.3 mm across, pale yellow (Y10-20); aerial mycelium especially abundant in the center and edge, blush pink (M20-30Y20); mycelium containing guttules, pale to dark brown, thick-walled, sometimes covered with exudates. Conidiophores (semi-)macronematous, arising vertically or laterally from hyphae, pale to dark brown, smooth, containing oil globules in the hyphal cell, constricted at the septum, thick-walled, occasionally 2-3 series of branches, 2-3 µm width; phialides cylindrical to ampulliform, up to 10 µm long, 2.5-4 µm width, discrete to integrated, terminal, pale brown, thick-walled, with short cylindrical or wide funnel-shape collarettes of 2.5-4 × 3 µm at the upper edge, hyaline to pale brown, thin-walled; conidia aseptate, ellipsoid, abundantly aggregated near the collarettes, 2-3 × 1 µm, hyaline, thin-walled.

Notes.

The yellowish color of the hymenium is due to the oil globules in immature asci (Fig. 11D, K ). The oil globules gradually disappear as the ascospores mature (Fig.). Trichobelonium albobarbatum forms conidiophores immersed in agar, especially at the bottom of the Petri dish (Figs 11S-V , 14H ). Both T. albobarbatum and T. kneiffii have well-developed dark brown subiculum, white anchoring hyphae, yellow hymenium, abundant crystals in excipulum, long asci (approximately 80-100 µm length), and 1-3-septate ascospores ( Schröter 1908). However, T. albobarbatum has wider asci (vs. 5-6 µm width) and larger ascospores (vs. 16-18 × 2-2.5 µm) than T. kneiffii .

Figures

Figure 11. Trichobelonium albobarbatum (TNS-F- 86430, holotype) A fresh apothecia on the decaying culm of unidentified grass (Poaceae) B dried apothecium with hyaline connective hyphae C protruding immature apothecia from the stromata D vertical section of the apothecium (in LA) E crystals in medullary excipulum (in LA) F connecting hyphae between ectal excipulum and subiculum (in LA) G texture of the stroma (in LA) H ascospores (in CB / LA) I ascus with mature ascospores (in CB / LA) J ascus with immature ascospores (in CB / LA) K immature ascus containing yellowish oil globes in the cytoplasm (in CB / LA) L paraphysis (in CB / LA) M rehydrated paraphysis with fragmented refractive vacuoles (in water) N blue-stained apical pore of ascus (in Melzer's solution after 3 % KOH pretreatment) O croziers at the base of asci (in CB / LA) P three months old colony on PDA Q yellow crystals formed on hyphae R acicular crystals (in water) S-V conidiophores with conidia (in CB / LA); W hyphae with exudates (in CB / LA). Scale bars: 0.5 mm (A, Q); 0.25 mm (B, C); 50 μm (D-F); 20 μm (R); 10 μm (G, H-O, S-W).

Figure 13. Line-drawings of the Neobelonopsis and Trichobelonium species I vertical section of the apothecium showing the marginal structure of ectal excipulum, medullary excipulum, and hymenium II asci III paraphyses IV ascospores. Scale bars: 10 μm.

Figure 14. Asexual morph and hyphal structures of the Neobelonopsis and Trichobelonium species A conidiophores of N. acutata B monilioid hyphae of N. bicolor C conidiophores with conidia of N. cinnabarina D conidiophores with conidia of N. didymospora E conidiophores with conidia of N. microspora F conidiophores with conidia of N. multiguttata G conidiophores with conidia of N. obtusa H conidiophores with conidia of T. albobarbatum I hyphal mass with melanized appressorium-like structure of T. miscanthi. Scale bars: 10 μm.