Callainostiolum taiwanense Marasinghe, Hongsanan, C.H. Kuo & K.D Hyde sp. nov.
MycoBank number: MB 840870; Index Fungorum number: IF 840870; Facesoffungi number: FoF 10406; Figure 2
Etymology. The species epithet refers to the country (Taiwan) where the fungus was collected.
Holotype. MFLU 21–0136
Description. Colonies epiphyllous and hyphophyllous on Muntingia calabura leaves forming blackened areas surrounded by yellow patches, single to confluent. Superficial mycelium absent. Sexual morph: Ascomata 350–500 × 250–300 μm ( = 451 × 275 μm, n = 6), scattered, superficial, 2–3-locules, brown to black, soft, rounded and dome-like in section, Ostiole greenish blue opening in an irregular manner, become slimy mass when place in water. Peridium 19–25 μm thick, one-layered, composed of pale brown to greenish blue, parallel, pseudoparenchymatous cells of compact textura subglobulosa to angularis. Hamathecium comprises with hyaline, branched, aseptate filiform pseudoparaphyses. Asci 65–75 × 7–10 μm ( = 68 × 8 μm, n = 10), 8-spored, bitunicate, cylindrical to clavate, overlapping 1–2-seriate, short pedicellate. Ascospores 15–20 × 4–6 μm ( = 18 × 5 μm, n = 10), hyaline, fusiform to clavate, slightly curved, 3-septate, highly constricted at the septum at maturity, smooth walled. Asexual morph: Undetermined.
Material examined. TAIWAN. Chiayi, Fanlu Township area, Dahu Forest. on leaves of Muntingia calabura L. (Muntingiaceae), , D. Sandamali, (DTF10) (MFLU 21–0136, holotype)
Note. Callainostiolum taiwanense sp. nov. shares similar morphological features to Actinomyxa. in ascomata characters with rounded, dome-like sections and ostioles opening in an irregular stellate manner. However, Callainostiolum taiwanense differs from species in Actinomyxa in having ascomata with 2–3-locules, water dissolving apical greenish blue ostiole and short pedicellate asci, while Actinomyxa has ascomata with 1-locule, water dissolving colorless ostiole with long pedicellate asci. Phylogenetic comparison is unable due to the lack of molecular data for Actinomyxa taxa. Phylogenetic analysis a combined LSU, ITS and SSU sequences indicate that our new taxon is placed within Microthyriales clade and forms a sister lineage with Isthmolongispora lanceata with high support (95% MLBS, 1.00 BYPP) support (Figure. 1). Isthmolongispora lanceata is only known as an asexual morph and it is stated as uncertain taxonomic placement in Ascomycota incertae sedis (Yen et al. 2019). Morphologically Callainostiolum taiwanense does not resemble to the type genus Microthyrium. Therefore, we introduced Callainostiolum as a new genus in Microthyriales incertae sedis based on the available morpho-molecular data until further depth studies.
Figure 2. Callainostiolum taiwanense (MFLU 21–0136, holotype). a Fallen living leaf specimen. b Yellow patches surrounding ascomata. c Ascomata on the surface of leaves. d Section through ascomata. e Peridium. f Greenish blue ostiole. g Pseudoparaphyses. h, i Imature asci. j–l mature asci. m–n Ascospores. Scale bars: 200 μm (c), 100 μm (d), 50 μm (e,f), 20 μm (g), 10 μm (h–l), 5 μm (m–o).