Sphaerulina nanjingensis X. Yu. Zhang, Q. Y. Zhang & B. Fan, 2025

Sphaerulina nanjingensis X. Yu. Zhang, Q. Y. Zhang & B. Fan sp. nov.

Fig. 14 View Figure 14

Type.

CHINA • Jiangsu Province, Nanjing, Nanjing Forestry University, Baima Campus , fungal endophytes from Pinus densiflora , May 2023, Ben Fan and Xiuyu Zhang, NF 651 ( holotype HMAS 352955 View Materials , culture ex-type CGMCC 3.28952 ) .

Etymology.

Derived from “Nanjing,” indicating that this species was first discovered in Nanjing.

Description.

Mycelium composed of hyaline, smooth to slightly rough-walled, multi-septate, branched and slender hyphae, 1.3–2.2 μm in diameter. Asexual state: Conidiophores reduced to conidiogenous cells. Conidiophores are not clearly differentiated; Conidiogenous cells are integrated, terminal or intercalary, hyaline, smooth-walled, monoblastic to polyblastic, producing conidia in acropetal chains through blastic conidiogenesis; conidia are produced directly from the apical or lateral sides of hyphae. Conidia multiseptated, long, filiform, falcate, slender, hyaline, smooth, (10.0 –) 14.7–27.4 (– 38.3) × (1.4 –) 1.6–2.1 (– 2.2) μm (Fig. 14 D – H View Figure 14 ). Sexual state unknown.

Culture characteristics.

Colonies on SNA with a floccose to woolly surface, off-white to translucent in appearance, and with a regular, well-defined margin. On OA, aerial hyphae are concentrated in the middle area with very few around it. The optimal temperature is 20–25 ° C, reaching 9–13 mm in diameter in 10 days on OA. No growth at 5 ° C or 35 ° C.

Additional material examined.

CHINA • Jiangsu Province, Nanjing, Nanjing Forestry University, Baima Campus , fungal endophytes from Pinus densiflora , May 2023, Ben Fan and Xiuyu Zhang, NF 851 .

Notes.

Two isolates, NF 651 and NF 851, identified as S. nanjingensis , are phylogenetically related to S. chaenomelis . Nevertheless, they can be clearly distinguished based on both morphological characteristics and multi-locus phylogeny. Morphologically, conidia of NF 651 are significantly smaller, measuring (10.0 –) 14.7–27.4 (– 38.3) × (1.4 –) 1.6–2.1 (– 2.2) μm, whereas those of S. chaenomelis are considerably larger, (10 –) 30–38 (– 50) × (2 –) 2.5–3 (– 4) μm. Ecologically, NF 651 was isolated as an endophyte from Pinus densiflora , while S. chaenomelis is known as a pathogen of Chaenomeles sinensis ( Crous et al. 2013 a) . Although some endophytic species are known to display pathogenic behaviour under certain conditions, the distinct host associations and lifestyles of these two taxa suggest ecological divergence. At the molecular level, NF 651 differs from Sphaerulina chaenomelis MUCC 1510 (type) by 35 nucleotide substitutions across 2315 aligned base pairs from the combined ITS, nLSU, RPB 2, TEF 1 and TUB gene regions, corresponding to a divergence of 1.51 %. The ITS and nLSU regions are relatively conserved among Sphaerulina species, whereas most variations occur in the protein-coding genes — 3.78 % (13 / 344 bp) in RPB 2, 2.22 % (7 / 314 bp) in TEF 1, and 3.71 % (14 / 377 bp) in TUB — which exceed the typical intraspecific range ( Jeewon and Hyde 2016) and thus support its recognition as a distinct species.