Thyridium pluriloculosum (Perdomo, Dania Garcia, Gene, Cano & Guarro) R. Sugita & Kaz. Tanaka comb. nov.

Figs 4, 6B

Basionym.

Phialemoniopsis pluriloculosa Perdomo, Dania García, Gené, Cano & Guarro, Mycologia 105: 412 (2013).

Holotype.

USA, Nevada, human toe nail, D.A. Sutton, CBS H-20782, living culture CBS 131712 = UTHSC 04-7 = FMR 11070 (not seen).

Sexual morph.

Stromata scattered to grouped, pulvinate, circular to elliptical in outline, elevated beyond bark surface forming pustules, 0.6-0.7 mm high, 0.9-1.0 mm diam., dark brown to black. Ascomata perithecial, subglobose to ampulliform, 4-8 grouped, 700-780 µm high, 220-280 µm diam., immersed in stromata. Ascomatal wall 17-25 µm thick, composed of 7-10 layers of polygonal, 4-6.5 × 2-4 µm, dark brown cells. Ostiolar neck central, cylindrical, 400-430 µm long, 100-110 µm wide, periphysate. Paraphyses septate, unbranched, cylindrical, 92.5-110 µm long, 3.5-5.5 µm wide. Asci unitunicate, cylindrical, 110-175 × 9-12.5 µm (av. 145.6 × 10.3 µm, n = 15), broadly rounded at the apex, with a pronounced non-amyloid apical annulus, pedicellate (12.5-27.5 µm long), with 8 ascospores. Ascospores fusiform to ellipsoid, smooth, brown, with 3 transverse and 0-2 oblique or vertical septa, 13.5-18 × 6-8 µm (av. 15.5 × 7.3 µm, n = 50), l/w 1.7-2.6 (av. 2.1, n = 50).

Asexual morph (nature).

Conidiomata pycnidial, globose to subglobose, grouped, 220-300 µm high, 90-150 µm diam., immersed in stromata. Conidiomatal wall 8-18 µm thick, composed of 3-5 layers of polygonal, 3-4.5 × 2.5-4 µm, dark brown cells. Ostiolar neck central, cylindrical, 80-110 µm long, 90-110 µm wide, composed of polygonal cells, periphysate. Conidiophores hyaline, thin-walled, with branches bearing a group of 2-5 phialides terminally. Phialides tapering toward the tip, hyaline, 11-16 × 1-2 µm . Conidia ellipsoidal, with a slightly apiculate base, hyaline, smooth-walled, 3-4.5 × 1-2 µm (av. 3.7 × 1.5 µm, n = 50). Chlamydospores not observed.

Asexual morph (culture).

Coelomycetous asexual morph: Conidiomata pycnidial, scattered, single to grouped, superficial, globose to subglobose, 180-380 µm high, mostly 80-580 µm diam., up to 1170 µm diam. when grouped, often becoming cup-shaped when mature, surrounded by setose hyphae. Conidiomatal wall composed of polygonal to prismatic, 3-4.5 × 2.5-4 µm, dark brown cells. Setose hyphae erect, usually unbranched, septate, up to 360 µm long, 2-3 µm wide, pale brown. Conidiophores hyaline, thin-walled, simple or irregularly branched, with branches bearing a group of 2-5 phialides terminally. Phialides tapering toward the tip, hyaline, 10-25 × 1-2.5 µm . Conidia ellipsoidal, with a slightly apiculate base, hyaline, smooth-walled, in slimy masses, 3-4.5 × 1-2 µm (av. 3.8 × 1.4 µm, n = 50). Hyphomycetous synasexual morph: Conidiophores micronematous, mononematous, hyaline, simple or rarely branched. Phialides slightly tapering toward the tip, 4-11 × 1-2.5 µm, hyaline. Adelophialide absent. Conidia allantoid, hyaline, smooth-walled, in slimy heads, 3-9 × 1-2.5 µm (av. 6.2 × 1.7 µm, n = 50). Chlamydospores rarely present, solitary, 3.5-6.5 µm diam., hyaline to pale brown, thick- and rough-walled.

Culture characteristics.

Colonies on MEA at 25 °C attained 31-33 mm diam. after a week in the dark, whitish. On OA attained 32-36 mm diam., whitish to grey olivaceous (107). On PDA attained 32-33 mm diam., whitish to buff (45) (Fig. 6B).

Specimen examined.

Japan, Aomori, Hirakawa, Hirofune, Shigabo Forest Park, on dead twigs of Betula maximowicziana, 10 October 2017, K. Tanaka, KT 3803 (HHUF 30648), living culture MAFF 247508.

Notes.

The conidia from aerial hyphae of strain KT 3803 were larger (3-9 × 1-2.5 µm) in culture than those of the original description of Thyridium pluriloculosum (3-5 × 1-2.5 µm; Perdomo et al. 2013). However, we identified this new collection on Betula maximowicziana as T. pluriloculosum, based on the high sequence homology of three loci with ex-type culture of this species (CBS 131712; 99.6% in ITS, 99.2% in act, and 99.5% in tub2). The sexual-asexual relationship of T. pluriloculosum was verified in this study. Although this species has been reported from clinical sources as an asexual morph (Perdomo et al. 2013), the recently collected material represents a sexual morph on plant material.

In Thyridium, T. betulae has also been recorded on Betula sp. in France ( Roumeguère 1891). Although sequences of T. betulae are unavailable for molecular comparison, it is clearly different from T. pluriloculosum in having ascospores with 5-7 transverse and one longitudinal septum.