Annulohypoxylon albidiscum J.F. Zhang, J.K. Liu, K.D. Hyde & Z.Y. Liu, sp. nov.
Indexfungorum number: IF 551809, Facesoffungi number: FoF 01812, Fig. 1
Holotype – MFLU 15–3883
Etymology – From the Latin albus referring to white, and discus meaning disc, in reference to the morphology of stromata, which have a white, flattened truncatum-type disc, encircling the ostioles.

Saprobic on decorticated wood. Sexual morph Stromata 1.5 – 7.5 × 1 – 4.5 × 0.2 – 0.5 cm, (x̄ = 5.2 × 2.8 × 0.35 cm), glomerate, pulvinate to effused-pulvinate, with conspicuous perithecial mounds, surface shiny black, sphaerical to hemisphaerical, carbonaceous, blackish granules immediately beneath surface and between perithecia, with KOH extractable pigments greenish-olivaceous (90). Ostioles conical, papillate, encircled with a white, flattened truncatum-type disc. Perithecia 0.4 – 0.8 mm diam., sphaerical. Peridium laterally 43 – 51 μm thick, composed of carbonaceous, thick-walled, dark brown to black cells of texura angularis. Hamathecium comprising long, septate paraphyses, 4.5 – 5.3 μm wide at the base, 1.5 – 2.5 μm wide at the apex, with hyaline, guttulate cells. Asci (61–)77 – 87(–97) × 3.5 – 5 μm (x̄ = 83.5 × 4.3 μm, n = 20), 8-spored, unitunicate, cylindrical, long pedicellate, with a wedge-shaped, J+, subapical apparatus, 0.7 × 1.6μm. Ascospores 7.1 – 7.9(–8.4) × (3.4–)3.6 – 4.2(– 4.8) μm (x̄ =7.7 × 3.8 μm, n = 30), uniseriate, 1-celled, inequilaterally ellipsoidal, with narrowly rounded ends, light brown to brown, with or without guttules when young, germ slit straight, running along the entire spore-length on flattened side Asexual morph Undetermined.

Culture characteristics – Ascospores germinating on WA within 12 h and germ tubes produced from ends. Colonies growing fast on PDA, reaching 7 cm in 7 days at 25 – 28 °C, whitish colonies, azonate with diffuse margins, reverse at first whitish and turning light brown after 5 days.

Material examined – THAILAND, Chiang Rai, Muang District, Mae Chang Hot Spring, on limestone outcrops, on decorticated wood of unidentified host, 25 November 2014, JinFeng Zhang, ZJF–16 (MFLU 15–3883, holotype), ex-type living culture, MFLUCC 15–0645.

Notes – This is a typical Annulohypoxylon species with pulvinate to effused-pulvinate stromata, long cylindrical asci and pale brown, inequilaterally ellipsoidal ascospores. As well it is reminiscent to A. stygium (Lév.) Y.M. Ju et al. and A. nitens (Ces.) Y.M. Ju et al., regarding the stromatal characters. However, A. albidiscum differs from A. stygium in having larger perithecia (0.4 – 0.8 mm vs. 0.2 – 0.3 mm), a wider ascal apical apparatus (1.6 μm vs. 0.7 μm) and having white, flattened truncatum-type disc encircling the ostioles. In addition, the KOH-extractable pigments of this specimen is greenisholivaceous (90), whereas, the latter is greenish olivaceous (90) or dull green (70) (Ju and Rogers 1996). Annulohypoxylon albidiscum is distinct from A. nitens (Ces.) because the latter has a vinaceous reddish tone in the younger stages (Ju and Rogers 1996), as well as the asci of A. albidiscum are significantly shorter than the latter (77 – 87 μm long vs. 110–140μm long). The phylogenetic analysis showed that the A. albidiscum clustered with other Annulohypoxylon species and is phylogenetically closely related to A. bovei var. microspora (J.H. Mill.) Y.M. Ju et al., A. moriforme var. microdiscus (Y.M. Ju & J.D. Rogers) Y.M. Ju et al. and A. purpureonitens (Y.M. Ju & J.D. Rogers) Y.M. Ju et al., but they have different morphological characters.

Fig. 1 Annulohypoxylon albidiscum (holotype) a Stromata habit on wood b Stromata in side view c Cross section of the stromata showing perithecia d Section of peridium e Germinating ascospore f Long, hyaline paraphyses g – h Asci with ascospores in water i Ascus in Melzer’s reagent, showing the J+, subapical ring j – o Ascospores. Scale bars: a = 500 μm, b, c = 200 μm, d, f – i = 10 μm, j – o = 3 μm.