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

Fig. 2

Type.

China • Hainan Province: Ledong Li Autonomous County, on diseased leaves of Acronychia pedunculata Miq., 13 October 2023, X. G. Yan (HMAS 354067, holotype), ex-type living culture SAUCC 620701 = SAUCC 620702.

Etymology.

Refers to the genus Acronychia, from which the fungus was isolated.

Description.

Associated with diseased leaves of Acronychia pedunculata. Asexual morph on PDA: Mycelia superficial, membranous and immersed, hyaline, branched, septate, and smooth, 1.1–2.8 μm wide (x ̄ = 1.77 μm, n = 30). Conidiomata not observed. Conidiophores indistinct and always reduced to conidiogenous cells. Conidiogenous cells polyblastic, hyaline, straight or slightly curved, smooth-walled, arising from apices of branched hyphae, 1.4–3.7 × 1.2–2.0 μm (x ̄ = 2.4 × 1.6 μm, n = 15). Conidia solitary, smooth-walled, elliptical or fusiform, septate, 2–3 - septate, and straight or slightly curved, 5.4–11.6 × 1.5–2.7 μm (x ̄ = 7.1 × 2.1 μm, n = 65). Chlamydospores not observed. Sexual morph: Undetermined.

Culture characteristics.

Colonies were incubated on PDA medium at 25 ° C under dark conditions. After 14 days of cultivation, the colonies attained a diameter of 65–87 mm, with a daily growth rate ranging from 4.6 to 6.2 mm. Colonies exhibited an irregular outward growth pattern, covered with abundant white aerial mycelium. With prolonged incubation, the central region of the colony gradually changed from white to yellowish-brown, and the pigmentation subsequently extended toward the peripheral areas. The reverse surface was white at the initial stage and ultimately turned orange. Sparse sporulation was observed on PDA after 14 days of incubation.

Notes.

Based on phylogenetic analysis combined with four sequences (ITS, LSU, RPB 2, and TUB 2), Microdochium acronychicola (SAUCC 620701 and SAUCC 620702) constitutes an independent clade in the phylogenetic trees, closely related to M. hainanense (SAUCC 210781 and SAUCC 210782) and M. bambusinum (SAUCC 7638-2 and SAUCC 7531-3). Microdochium acronychicola (SAUCC 620701, ex-type) is distinguished from M. hainanense (SAUCC 210781, ex-type) by 18 / 558, 1 / 805, 62 / 976, and 35 / 753 characters in ITS, LSU, RPB 2, and TUB 2 sequences, respectively, with all gap sites excluded from the sequence comparisons. Microdochium acronychicola (SAUCC 620701, ex-type) is distinguished from M. bambusinum (SAUCC 7638-2, ex-type) by 18 / 548, 11 / 806, 89 / 897, and 93 / 767 characters in ITS, LSU, RPB 2, and TUB 2 sequences, respectively, with all gap sites excluded from the sequence comparisons. Morphologically, the conidia of M. acronychicola (HMAS 354067, holotype) are shorter than those of M. hainanense (HMAS 352156, holotype) S. B. Liu, X. Y. Liu, Z. Meng & X. G. Zhang and longer than those of M. bambusinum (HSAUP 7531-3, holotype) (5.4–11.6 × 1.5–2.7 μm vs. 11.5–19.34 × 2.8–5.4 µm vs. 4.8–7.2 × 2.1–3.4 µm). It was also found that the collection of M. acronychicola (SAUCC 620701 and SAUCC 620702) is closely related to two other species in this collection, namely M. chinense (SAUCC 1516001 and SAUCC 1516002) and M. brevisporum (SAUCC 785206 and SAUCC 785207). Microdochium acronychicola (SAUCC 620701, ex-type) is distinguished from M. chinense (SAUCC 1516001, ex-type) by 4 / 550, 3 / 810, 16 / 974, and 25 / 750 characters in ITS, LSU, RPB 2, and TUB 2 sequences, respectively, with all gap sites excluded from the sequence comparisons. Microdochium acronychicola (SAUCC 620701, ex-type) is distinguished from M. brevisporum (SAUCC 785206, ex-type) by 19 / 554, 16 / 788, and 50 / 733 characters in ITS, LSU, and TUB 2 sequences, respectively, with all gap sites excluded from the sequence comparisons. Morphologically, the conidiogenous cells of M. acronychicola (HMAS 354067, holotype) are shorter than those of M. chinense (HMAS 354069, holotype) and M. brevisporum (HMAS 354068, holotype) (1.4–3.7 × 1.2–2.0 μm vs. 4.2–22.9 × 1.7–2.3 μm vs. 1.4–9.6 × 0.9–3.0 μm). The conidia of M. acronychicola (HMAS 354067, holotype) are shorter than those of M. chinense (HMAS 354069, holotype) and longer than those of M. brevisporum (HMAS 354068, holotype) (5.4–11.6 × 1.5–2.7 μm vs. 5.1–13.8 × 1.5–2.9 μm vs. 4.6–9.1 × 1.7–4.3 μm). Therefore, based on morphology and phylogeny, this fungus is established as Microdochium acronychicola sp. nov.