Delonicicola siamense R.H. Perera, Maharachch. & K.D. Hyde, sp. nov., Index fungorum number: IF553771

Etymology: Referring to the country where the fungus was first collected.

Saprobic on seed pods of Delonix regia. Sexual morph Pseudostromata aggregated, immersed, dark brown to black, visible as raised, dark spots on the host surface. Ascomata 112-267 μm high, 75-264 μm diam. (x̅ = 162 × 125 μm, n = 20), perithecial, aggregated, immersed in host tissues, globose, subglobose to conical or irregular, hyaline, ostiolate, papillate. Papilla short, immersed or protruding through the host tissue, conical, periphysate. Peridium 10-16 μm wide (x̅ = 12 μm, n = 20), composed of 5-8 layers of hyaline cells of textura angularis. Hamathecium comprising dense filamentous, aseptate, unbranched paraphyses, 0.8-1.1 μm wide (x̅ = 0.9 μm, n = 20). Asci 29-42 × 3.4-4.9 μm (x̅ = 35 × 4.2 μm, n = 25), 8-spored, unitunicate, clavate, with short pedicel, apex simple. Ascospores 3.8-6.9 × 1-1.4 μm (x̅ = 5.4 × 1.2 μm, n = 20), uniseriate to biseriate, 1-septate, not constricted at the septum, ellipsoid, equilateral or inequilateral, with narrowly rounded ends, straight, hyaline, smooth-walled, without a mucilaginous sheath. Asexual morph Undetermined

Culture characters: Colonies growing on MEA, reaching 7 cm within 18 days, at 25°C, circular, white, even margin with zonation, becoming pale yellow with time, flat, lacking aerial mycelium, underneath brown.

Material examined: THAILAND, Chiang Rai, Mae Fah Luang University premises, on dried seed pods of Delonix regia (Boj. ex Hook.) Raf. (Fabaceae), 2 June 2015, R.H. Perera, RHP 92 (MFLU 17-0739, holotype) ibid. (HKAS, isotype), ex-type living culture = MFLUCC 15-0670 = KUMCC.

Notes: Delonicicola siamense is phylogenetically related to Asteromella pistaciarum, Liberomyces and endophytes of angiosperms. Both Liberomyces and Asteromella are coelomycetous genera with pycnidial conidiomata and allantoid, bacilloid or filiform, hyaline conidia. Delonicicola siamense is the only sexual morph known in Delonicicolaceae. The morphology of the sequenced endophytes was not described in the original publications (Vega et al. 2010; Lin et al. 2010). However, phylogenetic analysis supports that D. siamense is distinct from those
sequenced endophyte sequences.

Fig. Delonicicola siamense (MFLU 17-0739, holotype) a-b. Appearance of ascomata on host substrate. c. Vertical section through pseudostroma with ascomata. d. Vertical section through ascoma. e. Ostiole. f. Close up of the peridium. g. Paraphyses h-j. Asci. k-o. Ascospores. p. Germinating ascospore. q, r. Colony on MEA. Scale bars: b = 1 mm, c, d = 100 μm, e = 50 μm, f, g = 20 μm, h-j = 10 μm, k-p = 5 μm.