Pestalotiopsis smilacicola Y.R. Sun & Yong Wang bis, in Sun, Jayawardena, Sun & Wang, Microbiology Spectrum: e03987-22, 15 (2023)

MycoBank number: MB 571221; Index Fungorum number: IF 571221; Facesoffungi number: FoF 12921;

Etymology – Refers to the host plant from which the fungus was first isolated.

Holotype – MFLU 22-0165

Associated with leaf spots of Smilax china and Dioscorea sp.. Symptoms subcircular to irregular shape, brown, slightly sunken spots appear on the leaves of Smilax china, which later expand outwards. Small auburn spots appeared initially and then gradually enlarged. Sexual morph: Not observed. Asexual morph: Conidiomata solitary, subglobose, unilocular, black, semi-immersed on leaves. Conidiomatal wall 7.0–10.0 µm wide, thin walled, pale brown. Conidiophores indistinct. Conidiogenous cells subcylindrical to ampulliform, hyaline, smooth, 1.4–2.6 μm wide. Conidia 18 to 22 × 4 to 7 μm (x̄ = 20 × 5 μm, n = 40), L/W ratio of 3.8, fusiform, straight to slightly curved, 4 septate; basal cell obconic with a truncate base, hyaline or sometimes pale brown, smooth walled, 3 to 5 μm long; three median cells 9 to 15 μm long (x̄ = 12 μm, n = 40), pale brown to brown, concolorous, wall rugose, septa darker than the rest of the cell, somewhat constricted at the septa; second cell from base pale brown to brown, 3 to 5 μm long; third cell brown, 2 to 5 μm long; fourth cell brown, 3 to 5 μm long; apical cell 2 to 5 μm long, hyaline, conic to acute; with 2 to 3 tubular appendages on the apical cell, inserted at different loci in a crest at the apex of the apical cell, unbranched, 6 to 14 μm long; single basal appendage, unbranched, tubular, centric, 2 to 6 μm long.

Culture characteristics – Colonies on PDA reaching 10 cm diam after two weeks at 25 °C, colonies filamentous to circular, medium dense, aerial mycelium on surface flat or raised, with filiform margin, fluffy, white from above and reverse.

Material examined – Thailand, Chiang Mai Province, Mae Taeng District, Mushroom Research Center, leaf spots of Smilax sp. (Liliaceae), 16 July 2020, Y.R. Sun, M26 (MFLU 22-0165, holotype), ex-type culture, MFLUCC 22-0125. ibid., leaf spots of Smilax china (Liliaceae), 15 July 2020, Y.R. Sun, M13 living culture, MFLUCC 22-0124.

Notes – Two collections MFLU 22-0165 and MFLUCC 22-0124 share similar morphology. These two isolates clustered together and formed a sister clade to P. dracontomelon (MFLUCC 10-0149) in the phylogenetic tree. There are only 1 base pair difference in TEF and TUB genes and 3 base pair differences in the ITS gene between these two isolates. For the differences between P. smilacicola and its related species see the notes of P. chiangmaiensis (this study). Therefore, these two isolates are identified as conspecific, representing a new species.

Figure 16 Pestalotiopsis smilacicola (MFLU 22-0165, holotype). a Host. b, c Close up view of conidiomata. d Section through conidioma. e Section through pycnidial wall. f–h Immature conidia attached to conidiogenous cells. i–m Conidia. n Germinated conidium. Scale bars: b = 1000 µm, c = 200 µm, d = 50 µm, e = 20 µm, f–n = 10 µm.