Torula aquilariae X.H. Li, Phookamsak & J.F. Li, sp. nov

Index Fungorum number: IF 857067, Facesoffungi number: FoF 17237;

Etymology – Refers to the host genus, Aquilaria, of which the holotype was collected.

Holotype – KUN-HKAS 145332

Saprobic on fallen fruit pod of Aquilaria sinensis (Thymelaeaceae). Teleomorph: Undetermined. Anamorph: Colonies sporadic on host, black, powdery. Mycelium immersed on the substrate, composed of septate, branched, smooth, light brown hyphae. Conidiophores 6–20 μm long × 3.5–5 μm wide (x̅ = 15.6 × 4.6 μm, n = 10), macronematous, mononematous, solitary, erect, subcylindrical, subhyaline to light brown, minutely verruculose, thick-walled, consisting of 1–4 cells, without apical branches, or reduced to conidiogenous cells, with 1–2-celled, ellipsoid to subglobose or protuberance cells, arising from hyphae. Conidiogenous cells 3.9–4.7 μm long × 4.2–5 μm wide (x̅ = 4.5 × 4.8 μm, n = 10), polyblastic, terminal, dark brown to black, smooth to minutely verruculose, thick-walled, globose to ellipsoid or sometimes coronate at apex. Conidia 12.5–15 μm long × 3.8–5 μm wide (x̅ = 14.5 × 4.4 μm, n = 20) catenated, acrogenous, phragmosporous, light brown to greyish-brown, smooth to minutely verruculose, 1–3-septate, rounded at both ends, or with a dark, terminal, coronate, cupulate cell at apex, composed of moniliform cells, slightly constricted at some septa, chiefly subcylindrical. Conidial secession schizolytic.

Cultural characteristics – Conidia germinating on PDA within 14 h and germ tubes produced from the apical cell. Colonies growing on PDA, reaching 5 cm in 10 days at 28 °C, mycelium partly immersed to superficial, slightly effuse, cottony, with regular edge, surface greyish-white to brown, reverse pale black, dense, circular, slightly raised, smooth, entire, wrinkled folded, producing brown pigmentation in agar; teleomorph not formed within 60 days.

Material examined: CHINA, Yunnan Province, Yuan Jiang, on a fallen fruit pod of Aquilaria sinensis. (Thymelaeaceae), 12 July 2023, J-F. Li, TA-01 (KUN-HKAS 145332, holotype), ex-type living culture KUNCC 24-18640.

Notes: Torula aquilariae resembles T. masonii in having brown, verruculose, conidia and with constricted at the septa and a dark terminal coronate cell at apex, but differs in having smaller (T. aquilariae, 14.5 × 4.4 μm versus 21.6 × 9.5 μm, in T. masonii) conidia, shorter (T. aquilariae, 15.6 × 4.6 μm versus 16.8 × 4.5 μm, in T. masonii) conidiophores with smaller conidiogenous cells (T. aquilariae, 4.5 × 4.8 μm versus 6.6 × 5.3 μm, in T. masonii) [2,5]. Phylogenetic analyses showed that T. aquilariae constitutes an independent branch and is sister to T. mackenziei. Morphologically, T. aquilariae differs from T. mackenziei in having conidia with a dark terminal coronate cell at apex, which is rounded and paler in T. mackenziei; and longer conidiophores (T. aquilariae, 15.6 × 4.6 μm versus 3.8 × 3.5 μm, in T. mackenziei) while other morphological characters are difficult to use to distinguish these two species [5]. Moreover, the comparison of nucleotide pairwise differences indicated that T. aquilariae differs from T. mackenziei (MFLUCC 13-0839, ex-type strain) in 10/488 bp (2%) difference across the ITS gene region, 52/857 bp (6%) difference across the tef1-α gene region and 53/895 bp (5.9% difference, across the rpb2 gene region. Based on morphological characteristics and phylogenetic support coupled with the difference of nucleotide polymorphism, T. aquilariae is introduced as a new species in this study.

Fig. 1 Torula aquilariae (KUN-HKAS 145332, holotype) a A fallen fruit pod of Aquilaria sinensis b Colonies on a fallen fruit pod of A. sinensis. c Conidial structure on the substrate. d–h Conidiophores with conidiogenous cell. i–m Conidial masses. n–s Conidia. Scale bars: (a) 0.5 cm, (b) 200 µm, (c–h, j–s) 5 µm, (i) 10 µm.