Hypoxylon larissae Hai X. Ma

Song, Zikun, Pan, Xiaoyan, Li, Changtian, Ma, Hai-Xia & Li, Yu, 2022, Two new species of Hypoxylon (Hypoxylaceae) from China based on morphological and DNA sequence data analyses, Phytotaxa 538 (3), pp. 213-224 : 219-220

Hypoxylon larissae Hai X. Ma & Z. K. Song, sp.nov. ( Fig. 2 )

MycoBank: MB839549, Facesoffungi number: FoF 09871.

Etymology: —In reference to honour Russian mycologist Prof. Dr. Larissa N. Vasilyeva, who contributed to studies of pyrenomycetes.

Holotype: — CHINA. Yunnan Province, Mopanshan National Forest Park, saprobic on dead wood, 10 November 2019, Haixia Ma (FCATAS 844).

Sexual state: — Stromata effused-pulvinate with rounded margins, 1.2–5.9 cm long × 0.3–1.3 cm broad × 0.1–0.14 cm thick; with conspicuous perithecial mounds; surface Rust (39), Sienna (8), Fulvous (43), or Bay (6), distributed with tiny cracks; with orange-brown granules immediately beneath the surface and between perithecia; yielding Orange (7) and Luteous (12) pigments in 10% KOH; tissue below the perithecial layer inconspicuous, brown to black, homogeneous, 0.2–0.6 mm thick. Perithecia spherical to obovoid, black, 0.2–0.5 mm broad × 0.3–0.7 mm high. Ostioles umbilicate, with colored coating worn off exposing encircled black areas 70–182 µm diam on stromatal surface, opening lower than stromatal surface. Asci cylindrical, with eight uniseriate ascospores, 110–207 µm total length × 8.7–13.2 µm broad, the spore-bearing portion 86–130 µm long, and stipes 27–96 µm long, with amyloid and discoid apical apparatus bluing in Melzer’s reagent, 1.4–2.3 µm high × 2.9–4.9 µm broad. Ascospores smooth, light brown to dark brown, unicellular, inequilateral ellipsoid, with narrowly to slightly broad rounded ends, 15.5–22.9 (–23.6) × 7.3–10.6 µm (n=42, M=17.9 × 9 µm), with conspicuously straight germ slit spore-length on the convex side; perispore dehiscent in 10% KOH, with inconspicuous to conspicuous coil-like ornamentation in SEM; epispore smooth. Asexual state:— Undetermined.

Additional specimens examined: — CHINA. Yunnan Province, Mopanshan National Forest Park, on dead wood, 10 November 2019, Hai X. Ma (FCATAS 846) .

Note: — Hypoxylon larissae is characterized by its effused-pulvinate stromata, conspicuous perithecial mounds, Orange (7) and Luteous (12) pigments extracted in 10% KOH, amyloid apical apparatus, light brown to dark brown ascospores with straight germ slit and perispore dehiscent. In both morphological and phylogenetic aspects, the new species seems to be very similar and close to H. fenderi (bootstrap value = 96%/87%/1; Fig. 1 ), which has both similar perithecia [obovoid, 0.2–0.4 (–0.5) mm broad × 0.3–0.6 mm high] and KOH-extractable pigment Orange (7) ( Ju & Rogers 1996). Hypoxylon fenderi was originally described from Venezuela, and commonly found throughout the tropics. It differs from H. larissae by having smaller apical apparatus (0.5–1.2 µm high × 1.8–2.5 µm broad), smaller ascospores (9–12 × 4–5.5 µm) and sigmoid germ slit spore-length ( Ju & Rogers 1996). Unfortunately, no molecular phylogenetic data have so far been generated for the holotype of H. fenderi . The work accomplished by Hsieh et al. (2005), Sir et al. (2019) and Cedeno et al. (2020) provided additional ITS, LSU, RPB 2 and TUB2 sequence data of the species from Mexico, USA and Panama respectively, was used in our phylogeny.

Microscopically, H. larissae is also similar to H. diatrypeoides Rehm , both of which have the same size of ascospores with straight germ slit spore-length, perispore dehiscent in 10% KOH. However, the holotype of H. diatrypeoides from Brazil has restrictedly pulvinate stromata and bluing apical apparatus or not in Melzer’s reagent ( Ju & Rogers 1996), while H. larissae has effused-pulvinate stromata and amyloid and discoid apical apparatus bluing in Melzer’s reagent. The phylogenetic analysis showed that H. larissae from China is distantly related to the clade of H. diatrypeoides from Mexico in the phylogram ( Figure 1 ). The other specimen of H. diatrypeoides collected from New Zealand might be a different taxon, so our comparison was based on the type species of H. diatrypeoides .

Figures

FIGURE 1. Phylogenetic tree of Hypoxylon based on the multigene alignment of ITS-LSU-RPB2-TUB2 in the Maximum Likelihood analyses (RaxML). Support values of Maximum Likelihood (ML), Maximum Parsimony (MP) and Bayesian (B) analyses (bootstrap support above 50%, posterior probability value above 0.95) are displayed above or below the respective branches (ML/MP/BA).

FIGURE 2. Hypoxylon larissae (Holotype FACATAS 844). A. Stromata on wood. B, C. Stromatal surface and ostioles. D, E. Stroma in vertical section showing the perithecia and tissue below the perithecial layer. F. KOH-extractable pigments. G. Stromatal granules in water. H. Mature and immature asci in Melzer’s reagent. I. Asci in Melzer’s reagent. J. Immature asci in water. K. Mature asci in water. L. Ascospores in water. M. Ascospores in 10% KOH. N. Ascospores in water showing germ slit. O. Apical apparatus in Melzer’s reagent. P. Ascospore under SEM. Bars: A = 5 mm;B, C, E = 0.4 mm; D = 1 mm; H–K = 20 µm; L–O = 10 µm; P = 5 µm.