Thyridium flavostromatum R. Sugita & Kaz. Tanaka, 2022

Sugita, Ryosuke & Tanaka, Kazuaki, 2022, Thyridium revised: Synonymisation of Phialemoniopsis under Thyridium and establishment of a new order, Thyridiales, MycoKeys 86, pp. 147-176 : 147

Thyridium flavostromatum R. Sugita & Kaz. Tanaka sp. nov.

Figs 3 , 6A

Holotype.

Japan, Yamaguchi, Nagato, Misumikami, near Kusaritoge, on dead twigs of Phyllostachys pubescens , 26 March 2018, K. Tanaka, K. Arayama and R. Siguta, KT 3891 (HHUF 30647, holotype designated here), living culture MAFF 247509.

Etymology.

The name refers to yellowish stromata.

Sexual morph.

Stromata scattered to grouped, subepidermal, becoming erumpent to superficial, 0.7-1.4 mm long, 0.4-0.7 mm wide, yellowish to dark brown, red in 2% KOH. Ascomata perithecial, subglobose to ampulliform, mostly 2-6 grouped, 190-240 µm high, 200-220 µm diam., immersed in stromata to erumpent through host surface. Ascomatal wall 15-23 µm thick, composed of 5-8 layers of polygonal, 2.5-7 × 1.5-3.5 µm, dark brown cells. Ostiolar neck central, cylindrical, 80-140 µm long, 55-90 µm wide, periphysate. Paraphyses numerous, septate, unbranched, cylindrical, 50-105 µm long. Asci unitunicate, cylindrical, 62.5-90 × 6.5-10 µm (av. 78.7 × 7.8 µm, n = 30), broadly rounded at the apex, with a pronounced non-amyloid apical annulus, short-stalked (5-17.5 µm long), with 8 ascospores. Ascospores obovoid to ellipsoid, smooth, hyaline to pale brown, with 3 transverse and 0-2 vertical septa, 9.5-14 × 5-7.5 µm (av. 11.3 × 5.8 µm, n = 50), l/w 1.4-2.5 (av. 2.0, n = 50).

Asexual morph (nature).

Not observed.

Asexual morph (culture).

Hyphomycetous asexual morph formed. Conidiophores micronematous, mononematous, hyaline, thin-walled, simple or irregularly branched, with branches bearing a group of 2-3 phialides terminally. Phialides swollen at the base, tapering at the tip, hyaline, 3-6 × 1-1.5 µm. Adelophialides rarely present. Conidia ellipsoidal to allantoid, with a slightly apiculate base, hyaline, smooth-walled, 2-7 × 1-2.5 µm (av. 4.1 × 1.6 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 28-29 mm diam. after a week in the dark, whitish. On OA attained 35-37 mm diam., whitish. On PDA attained 28-31 mm diam., whitish to buff (45; Rayner 1970) (Fig. 6A ).

Notes.

Phylogenetic analyses based on ITS, act, and tub2 sequences suggested that T. flavostromatum was closely related to T. curvatum , T. hongokgense and T. limonesiae (Fig. 2 ), of which only T. hongokgense has unknown conidial state. Although T. curvatum forms sporodochial conidiomata ( Perdomo et al. 2013), those are not found in T. flavostromatum . Conidia of T. limonesiae (2.3-4.9 × 1.4-2 μm; Martinez et al. 2021) are smaller than those of T. flavostromatum (2-7 × 1-2.5 µm). Thyridium flavostromatum is similar to T. lasiacidis on Lasiacis ligulata ( Samuels and Rogerson 1989) in 1) having yellowish stromata becoming red in KOH, and 2) ellipsoidal ascospores with three transverse septa, with or without one longitudinal septum in 1-2 median cells. However, T. lasiacidis differs from T. flavostromatum by ascomata with a longer ostiolar neck (90-170 µm long) and dark brown ascospores with terminal pale brown cells ( Samuels and Rogerson 1989).

Figures

Figure 2. Maximum-likelihood tree of Thyridium species based on each ITS (A), act (B), tub 2 (C) and combined sequences (ITS- act - tub 2; D). ML bootstrap proportion (BP) greater than 70 % and Bayesian posterior probabilities (PP) above 0.95 are presented at the nodes as MLBP / Bayesian PP. A hyphen (' - ') indicates values lower than 70 % BP or 0.95 PP and a node not present in the Bayesian analysis is shown with ' x'. Ex-holotype and epitype strains are shown in bold and the newly obtained sequences are shown in red. Strains previously as Phialemoniopsis species are marked with a blue circle. The scale bars represent nucleotide substitutions per site.

Figure 3. Thyridium flavostromatum (A-S KT 3891 = HHUF 30647 T-AC culture KT 3891 = MAFF 247509) A-S sexual morph A-C appearance of stromata on substrate D, E ascomata in longitudinal section (D in 2 % KOH) F ostiolar neck of ascoma G paraphyses H ascomatal wall I-K asci L apex of the ascus M stipe of the ascus N-R ascospores S germinating ascospore T-AC hyphomycetous asexual morph T sporulation in culture U phialides V slimy conidial heads W conidiophores X phialide Y adelophialide Z-AB conidia AC chlamydospores and conidia. Scale bars: 1 mm (A); 500 µm (B, C); 100 µm (D, E); 50 µm (F); 10 µm (G-K, M, S, U, V); 5 µm (L, N-R, W-AC); 250 µm (T).

Figure 6. Colony characters of Thyridium species used in this study on MEA (bottom right), OA (bottom left) and PDA (upper) within 1 week at 25 ° C in the dark A T. flavostromatum (culture KT 3891 = MAFF 247509) B T. pluriloculosum (culture KT 3803 = MAFF 247508) C T. punctulatum (culture KT 3905 = MAFF 247510). Scale bars: 3 cm (A-C).