Cytospora guizhouensis H. Zhang & Y.L. Jiang, sp. nov. (FIGURE. 2)

MycoBank: MB849513

Etymology: referring to Guizhou Province, China, where the ex-type strain was isolated.

Holotype: HGUP 19-0048.

Endophytic in roots of Rosa roxburghii. Sexual morph: not observed. Asexual morph: Conidiomata (Group AIII), pycnidial, subspherical to spherical, brown to dark brown, most solitary, semi-immersed to immersed, mostly with setae and ostiole, exuding dark brown conidial masses, 100–1200 μm diam. Locules numerous, irregular, subdivided frequently by invaginations with common walls. Conidiophores borne along the locules, hyaline, smooth, thin-walled, unbranched, 9.5–16 × 1–2 μm (x = 12 × 1.5 μm, n = 10). Conidiogenous cells enteroblastic, polyphialidic, hyaline, smooth, cylindrical to ampulliform, tapering towards the apex, 6.5–9.5 × 1–2 μm (x = 8 × 1.5μm, n = 10). Conidia hyaline, smooth, thin-walled, aseptate, allantoid, eguttulate, with bluntly rounded ends, straight to slightly curved, 1.5–3 × 0.5–1 μm (x = 2 × 0.8 μm, n = 30).

Culture characteristics: Colonies reaching 55 mm diam. on PDA after 21 d in the dark at 28°C; grayish-white, flocculent, aerial mycelium abundant, with irregular edges and reverse concolorous.

Material examined: CHINA, Guizhou Province, Liupanshui City, 25°52′52″ N, 104°33′59″ E, on healthy roots of Rosa roxburghii, 4 August 2020, H. Zhang (HGUP 19-0048, holotype), ex-type living culture: GUCC 19-0048.1; other living culture: GUCC 19-0052.1 and GUCC 19-0119.1.

Notes: Multigene phylogenetic analyses revealed that Cytospora guizhouensis was closely related to C. lumnitzericola, forming a sister branch with high statistical support (ML-BS = 99%, BYPP = 1) (Fig. 1). Sequence similarity between these two species (GUCC 19-0048.1 and MFLUCC 17-0508) in the act region was 94.49% (240/254) with 4 gaps, the ITS region was 95.87% (511/533) with 9 gaps, and the rpb 2 region was 97.43% (719/738) with no gaps. The ex-type MFLUCC 17-0508 was missing tef 1 and tub 2 gene sequences. Morphologically, C. guizhouensis can be distinguished from C. lumnitzericola in several key characteristics. The conidiogenous cells of C. guizhouensis are cylindrical to ampulliform (6.5–9.5 × 1–2 μm), whereas those of C. lumnitzericola are exclusively ampulliform (8.5– 14 × 0.6–1.4 μm). Additionally, the conidial dimensions differ significantly between the two species: C. guizhouensis produces smaller conidia (1.5–3 × 0.5–1 μm) in contrast to the larger conidia of C. lumnitzericola (4–4.5 × 1–1.3 μm). No morphological characteristics such as conidiomata, locules, pycnidial wall, and conidiophores were described for C. lumnitzericola (Norphanphoun et al. 2018). Therefore, C. guizhouensis was introduced as a new species.