Nigrospora sphaerica (Sacc.) E. W. Mason, Trans. Br. Mycol. Soc. 12 (2-3): 158 (1927).

Fig. 17

Substrate and distribution.

Pathogens with a wide host range, primarily causing leaf spot or leaf blight.

Description.

Associated with leaf spots of Juglans regia. Lesions irregular in shape and dark brown in color. Sexual morph: Not observed. Asexual morph: On SNA, Hyphae 2.5–5 µm in diam., branched, septate, contracted at septum, hyaline to dark brown, smooth. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 6.0–10.5 × 5.0–8.1 µm (x ̄ = 7.8 × 6.6 μm, n = 30), subglobose, monoblastic, pale brown. Conidia 11.8–15.8 × 9.9–13.7 µm (x ̄ = 14.1 × 11.6 μm, n = 30), globose to subglobose, solitary, aseptate, black, smooth.

Culture characteristics.

Colonies after 7 days at 25 ° C: On PDA, colonies reach 90 mm diam., flat, spreading, with regular margins, surface white and reverse salmon. On MEA, colonies reach 27–30 mm diam., flat, aerial mycelia scant, regular margins filamentous, surface and reverse white. On CMA, colonies reach 56–60 mm diam., cottony, dense aerial mycelia, with regular margins, surface white and reverse pale salmon. On SNA, colonies reach 20–22 mm diam., flat, aerial mycelia scant, regular margins filamentous, surface and reverse white. On WA, colonies reach 20–22 mm diam., flat, aerial mycelia scant, regular margins filamentous, surface and reverse white. On OA, colonies reach 73–75 mm diam., flat, spreading, dense aerial mycelia, with regular margins, surface greyish lilac and reverse center black and margin pale salmon. Sporulation was abundant only on SNA after 14 days.

Material examined.

China • Yunnan Province, Lincang City, on the diseased leaves of Juglans regia with spots, 7 May 2024, M. T. Zou, HGUP 25-0063; GUCC 25-0134, GUCC 25-0135, GUCC 25-0136, GUCC 25-0137, GUCC 25-0138 and GUCC 25-0139.

Notes.

In the phylogenetic analyses (Fig. 3), the six strains obtained in this study (GUCC 25-0134, GUCC 25-0135, GUCC 25-0136, GUCC 25-0137, GUCC 25-0138, and GUCC 25-0139) clustered with the N. sphaerica species clade with strong statistical support (100 % ML / 1.0 BI). Morphologically, our isolates closely resemble N. sphaerica in their overall diagnostic characteristics. The conidia of our strains are comparable in shape but slightly smaller (14.1 × 11.6 µm) than those reported for N. sphaerica (18.22 × 18.22 µm), while the conidiogenous cells also show similar dimensions (7.8 × 6.6 µm vs. 7.97 × 7.97 µm; Wang et al. 2017; Hyde et al. 2024 a). This study represents the first record of N. sphaerica isolated from leaves of J. regia.