Microdochium brevisporum X. G. Yan, Y. J. Wang, C. C. Ai & X. G. Zhang sp. nov.

Fig. 3

Type.

China • Hainan Province: Wuzhishan National Natural Reserve, on diseased leaves of Bambusoideae sp., 28 March 2024, X. G. Yan (HMAS 354068, holotype), ex-type living culture SAUCC 785206 = SAUCC 785207.

Etymology.

brevis – (Latin) meaning short + sporum (Latin) meaning spored, refers to the relatively short conidia of this fungus.

Description.

Associated with diseased leaves of Bambusoideae sp. Asexual morph on PDA: Mycelium immersed and superficial, hyaline, branched, septate, smooth, 1.1–2.5 μm wide (x ̄ = 1.59 μm, n = 30). Conidiophores cylindrical, branched, arising from hyphae, often reduced to conidiogenous cells. Conidiogenous cells polyblastic, hyaline, straight or occasionally curved, smooth-walled, 1.4–9.6 × 0.9–3.0 μm (x ̄ = 4.6 × 1.5 μm, n = 20). Conidia solitary or branched, hyaline, elliptical to subcylindrical, smooth-walled, straight or slightly curved, 0–2 - septate, 4.6–9.1 × 1.7–4.3 μm (x ̄ = 6.0 × 2.4 μm, n = 75). Chlamydospores not observed. Sexual morph: Undetermined.

Culture characteristics.

Colonies incubated on PDA at 25 ° C under dark conditions attained 63–71 mm in diameter after 14 days, with a daily growth rate ranging from 4.5 to 5.1 mm. Colonies were overall white and exhibited concentric zonate growth radiating from the center. At 14 days of incubation, the aerial surface remained persistently white; the reverse surface gradually turned brown in the central region, and sporogenous structures were progressively produced in the central colony area. Sporulation commenced on PDA after 21 days of incubation, with conidia formed directly on vegetative hyphae.

Notes.

Phylogenetic analyses combined with four gene sequences (ITS, LSU, RPB 2, and TUB 2) showed that Microdochium brevisporum (SAUCC 785206 and SAUCC 785207) constitutes an independent clade, closely related to M. hainanense (SAUCC 210782 and SAUCC 210781) and M. chinense (SAUCC 1516001 and SAUCC 1516002). Microdochium brevisporum (SAUCC 785206, ex-type) is distinguished from M. hainanense (SAUCC 210781, ex-type) by 22 / 557, 6 / 788, and 40 / 733 characters in ITS, LSU, and TUB 2 sequences, respectively, excluding gap sites. Microdochium brevisporum (SAUCC 785206, ex-type) is distinguished from M. chinense (SAUCC 1516001, ex-type) by 15 / 552, 6 / 788, and 53 / 733 characters in ITS, LSU, and TUB 2 sequences, respectively, excluding gap sites. Morphologically, the conidia of M. brevisporum (HMAS 354068, holotype) are shorter than those of M. hainanense (HMAS 352156, holotype) and M. chinense (HMAS 354069, holotype) (4.6–9.1 × 1.7–4.3 μm vs. 11.5–19.34 × 2.8–5.4 µm vs. 5.1–13.8 × 1.5–2.9 μm). The conidiogenous cells of M. brevisporum (HMAS 354068, holotype) are shorter than those of M. hainanense (HMAS 352156, holotype) and M. chinense (HMAS 354069, holotype) (1.4–9.6 × 0.9–3.0 μm vs. 16.3–22.4 × 4.1–5.7 µm vs. 4.2–22.9 × 1.7–2.3 μm). In addition, the colonies of M. brevisporum (HMAS 354068, holotype) appear white overall and grow from the center in a concentric ring-like pattern, while the colonies of M. chinense (HMAS 354069, holotype) are predominantly white, with some areas appearing pale yellowish (Liu et al. 2022). Therefore, based on morphology and phylogeny, this fungus is established as Microdochium brevisporum sp. nov.