Discosia pini
Discosia pini Heald, Mycologia 1(5): 216 (1909)
Index Fungorum number: IF193448 Facesoffungi number: FoF07469
Sexual morph: Undetermined. Asexual morph: Coelomycetous. Conidiomata 140–258 × 45–59 (x̄ = 195 × 54, n = 5) μm, sparse, acervular, superficial, bilocular, which is separated by interlocular wall and there are 2–3 hyaline, vertical supporting partitions inside the bigger loculus. Peridium 14–18 μm thick, brown, comprising thick-walled cells of textura angularis. Conidiogenous cells 4–6 × 1–2 (x̄ = 4.5 × 1.5, n= 15) μm, subcylindrical, developing from the inner stromatic tissue, monophialidic, integrated, hyaline, smooth. Conidia 14–20 × 1.9–3 (x̄ = 17 × 2.7, n = 50) μm, hyaline, fusiform with rounded ends, straight or slightly curved, 3-celled and the second cell from base is longer, with 2-appendages. Appendages 4–10 (x̄ = 8, n= 50) μm long, hyaline, straight, filiform, with rounded ends, with a round base, producing from the attachment between the middle cell and the terminal cell of conidia.
Culture characteristic: Cultures were made from germinating conidia which germinated after 1d on PDA. The colonies are rapid-growing, attaining a diameter of 5 cm in 12 days at 22 °C. Colonies white with one grey annulation at the centre, becoming fully grey at the aging stage, velvety, circular, olive-green to grey from reverse. In vitro, the conidia form from the mycelial strand.
Material examined: China, Yunnan Province, Honghe State, Yunti County, on a decay fern leaf, 20 September 2017, De-Ping Wei, YT07 (HKAS 101478); living culture KUMCC 18-0033.
GenBank Accession No: ITS: MT012348, LSU: MT012355, RPB2: MT025047
Notes: The multiple gene tree indicates that our collection (HKAS 101478) has a close affinity to Discosia pini (MAFF 410149) and D. artocreas (NBRC 8975) with strong statistical support (87% ML/ 0.99 PP). The nucleotide comparison shows that our isolate is identical to the above two reference species within 545 bp ITS and 782 bp LSU sequences. Unfortunately, except for BT gene sequence data, other gene sequences of D. pini (MAFF 410149) and D. artocreas (NBRC 8975) are not available and we could not successfully obtain BT gene sequences for our isolate in this study. Even though the full morphology of D. pini (MAFF 410149) and D. artocreas (NBRC 8975) are not linked to any literature (Tanaka et al. 2011), our isolate is phylogenetically separated from the ex-type strain of D. artocreas (CBS 124848). Our collection is similar to D. artocreas (CBS 124848) in having hyaline conidia with a longer second cell from base, but differs in the position where the appendages are produced. The apical appendage of D. artocreas is polar and the basal appendage is located far above the conidium base (Matsushima 1975, Liu et al. 2019). However, the appendage of our collection is borne from the junction of the terminal cell and the middle cell. The type specimen of D. pini (No. 758) was originally reported on Pini ponderosae by Heald (1909), and he provided a description and hand-drawing. Our collection resembles D. pini in having black, glabrous, bilocular conidiomata with vertical columns inside the larger loculus and similar size of conidia (14–20 × 1.9–3 μm in our collection vs 12–20 × 2.6 μm in NEB 758). Our collection differs slightly from D. pini (NEB 758) however, by having round ends to the conidia and shorter appendages (4–10 μm long), while D. pini (NEB 758) has relatively pointed ends to the conidia and longer appendages (10–12 μm long). Considering our collection is most similar to the type specimen of D. pini (NEB 758) rather than D. artocreas, we report our collection as a new host record of D. pini from fern leaf bases based on morphological and phylogenetic evidence. However, we suggest treating the strains D. artocreas (NBRC 8975) as an undetermined species as its morphology is not known and phylogenetically it separates from its type strain. Fresh collections with further sequence data may prove this conclusion to be incorrect.
Figure X. Discosia pini (HKAS 101478, new host record). a, b Conidiomata on fern leaf. c Column . d Vertical section through conidioma showing two loculi and three columns. e, f Conidiogenous cell bearing conidia. g–i Conidia. j Germinating conidium. k, l Conidiogeneous cells formed from a mycelial strand on culture. m, n Upper and reverse review of culture after 8 days incubation on PDA. Scale bars: d = 50 μm, e, j, k = 20 μm. c, f–i, l = 10 μm. (The columns are indicated with black arrows, a–i observed from herbarium specimen, j–n described from culture collection).
Reference: Hyde KD, de Silva NI, Jeewon R, Bhat DJ, Liu NG, Chaiwan N, Bulgakov TS (2020) AJOM new records and collections of fungi: 1–100. Asian Journal of Mycology, 3, 22-294.
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