Rubroshiraia D.Q. Dai & K.D. Hyde

Dai, Dong-Qin, Wijayawardene, Nalin N., Tang, Li-Zhou, Liu, Chao, Han, Li-Hong, Chu, Hong-Long, Wang, Hai-Bo, Liao, Chun-Fang, Yang, Er-Fu, Xu, Rui-Fang, Li, Yun-Min, Hyde, Kevin D., Bhat, D. Jayarama & Cannon, Paul F., 2019, Rubroshiraia gen. nov., a second hypocrellin-producing genus in Shiraiaceae (Pleosporales), MycoKeys 58, pp. 1-26 : 1

Rubroshiraia D.Q. Dai & K.D. Hyde gen. nov.

Etymology.

The epithet " Rubro " means red colour referring to reddish ascotromata similar to the genus Shiraia .

Description.

Parasitic on living branches of bamboo. Sexual morph: Ascostromata solitary, superficial, globose to subglobose, fleshy, reddish, with locules lining the periphery, with dark ostiolate tips appearing on surface. Ascostromatic tissue thick, pinkish, composed of wider woven hyphae of textura intricata. Locules globose to subglobose, immersed in the peripheral layer of ascostromata, with narrow ostiolate openings. Peridium composed of several layers of hyaline to dark brown, small cells of textura angularis to textura intricata. Hamathecium of interthecial, hyaline, septate, branched pseudoparaphyses above asci. Asci 8-spored, thick-walled, bitunicate, fissitunicate, cylindrical, short-pedicellate, with an ocular chamber. Ascospores spirally arranged in asci, filiform, hyaline, with transverse septa, smooth-walled. Asexual morph: Undetermined.

Type species.

R. bambusae D.Q. Dai & K.D. Hyde.

Notes.

The hypocrellin-producing fungus R. bambusae is a well-known taxon used in Chinese traditional medicine which is called “Zhuhongjun” or “Zhuxiaorouzhuojun” in Chinese. However, without molecular data, it was wrongly named as H. bambusae ( Liu 1978).

Hypocrella bambusae was combined by Saccardo (1878), based on its linear asci and filiform ascospores. Index Fungorum (2019) lists its basionym as Hypocrea bambusae Berk. & Broome, which was collected on the inflorescences of bamboo in Sir Lanka and had linear asci and filiform ascospores ( Berkeley and Broome 1875). Liu (1978) recorded a well-known Chinese medicinal ascomycete, producing 0.7-1.5 mm diam., hemispheric and reddish stromata with multi-locules, cylindrical asci and filiform ascospores which are spirally arranged and more than 250 μm long on bamboo culms. Liu (1978) identified this fungus as H. bambusae , probably based on its cylindrical asci and filiform ascospores. In addition, species of Hypocrella usually produce perithecial ascomata ( Saccardo 1878). To our knowledge, no fungal records or herbal medicine like that described in Liu (1978) occur in Sir Lanka. Moreover, based on the examination of type material of Hypocrea bambusae , it has smaller (0.1 cm vs. 0.7-1.5 mm in diam.) and black stromata, unitunicate asci and ascospores are in a single fascicle but not significantly helically coiled ( Fig. 7 ). Hence, we conclude that Liu (1978) made a wrong identification.

New collections of “Zhuhongjun” were collected and sequenced. The phylogenetic analyses showed it belongs to Shiraiaceae and is separate from Shiraia with high bootstrap support (100/1.00 MLBS/BSPP) ( Fig. 2 ). Grandigallia has not been included in the phylogenetic tree as it is lacking gene sequences in the GenBank (retrieved date: 13 May 2019). However, Grandigallia can be morphologically distinguished from the new taxon in having black ascostromata and muriform ascospores (Barr 1987; Ariyawansa et al. 2013). Thus, this fungus is introduced as R. bambusae gen. et sp. nov in this study.

Rubroshiraia bambusae is often confused with S. bambusicola by Chinese traditional folk residents, probably because of the similarity of their ascostromata, parasitism on bamboo host and similar efficacy of medical treatment. However, it differs from S. bambusicola by its smaller sized ascostromata (0.7-1.2 cm long × 0.7-1 cm wide vs. 1-6 cm long × 1-4 cm wide) and distinct ascospores (filiform ascospores vs. fusiform and muriform ones). Both of the above species can produce the metabolites hypocrellin A and B, whereas R. bambusae contains almost double the content compared to S. bambusicola ( Fig. 4 ).

Figures

Figure 2. Maximum likelihood phylogenetic tree generated from RAxML (GTR + G model), based on combined LSU, SSU, TEF 1 and RPB 2 sequences data. ML values (MLBP) (> 50 %), resulting from 1000 bootstrap replicates and Bayesian posterior probabilities (BYPP) greater than 0.90, are given at the nodes. The original isolate numbers' codes are noted after the species names. The tree is rooted to Dothidea insculpta (CBS 189.58). Ex-type or ex-epitype strains are in bold. Newly generated strains are in red and the new genus is in yellow background.

Figure 4. Hypocrellin A and hypocrellin B HPLC-UV profiles (265 nm) of standards and stromatal HPLC-UV profiles (265 nm) of specimens of Shiraia bambusicola (HKAS 102253) (II) and Rubroshiraia bambusae (HKAS 102255) (III) and DAD spectra of major metabolites.

Figure 7. Rubroshiraia bambusae (HKAS 102255, holotype) A fruiting bodies B, C surface of ascostromata showing the openings of ostiole D vertical section of ascostromata E, F vertical section of locule G peridium of locule H asci and pseudoparaphyses I asci and asci ocular chamber J ascospores K, L immature asci. Scale bars: 1 cm (A), 25 mm (B), 2 mm (C, D), 500 μm (E, F), 200 μm (G), 50 μm (H-L).