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

Index Fungorum number: IF 254776; Facesoffungi number: FoF 06599.

Basionym: Trichosporum sphaericum Sacc., Michelia 2 (no. 8): 579 (1882).

Pathogenic or saprobic on leaves of Fraxinus sp. Asexual morph: Hyphae smooth, branched, septate, hyaline, or pale brown. Conidiophores mostly reduced to conidiogenous cells. Conidiogenous cells 9.5–16.5 × 7.4–9.8 μm diam. (x̄ = 12.7 × 8.4 μm, n = 30), discrete, monoblastic, determinate, unbranched, and ampulliform to subglobose hyaline to pale brown. Conidia 11.5–15.7 × 13.3–19.6 μm diam. (x̄ = 14 × 16.7 μm, n = 50), sparse, discrete, globose or subglobose, black, shiny, smooth, and aseptate. Sexual morph: Undetermined.

Culture characteristics – Colonies on PDA reach 9 cm diam. in 5 d at 25 C, circular, entire margined, floccose or suede-like texture, surface initially white, becoming dark gray with age and reverse initially white, and turning smoke gray when mature.

Material examined – China, Shandong Peninsula, on living leaves of Fraxinus sp., October 7 2017, Yuanyuan Hao (JZBH 3230015), living culture JZB 3230015, and KUMCC 19-0232.

Leaf spot symptoms – Leaf spots are irregularly scattered and free-form shaped, composed of dark brick outer border with a light brown inner core, and margined by healthy leaf tissues.

Other materials examined – China, Shandong Peninsula, on living leaves of Cirsium setosum, October 7 2017, Yuanyuan Hao (JZBH 3230013), living culture JZB 3230013, KUMCC 19-0230; China, Shandong Peninsula, on living leaves of Phragmites australis, October 7 2017, Yuanyuan Hao (JZBH 3230014), living culture JZB 3230014, and KUMCC 19-0231.

NotesNigrospora sphaerica is identified as a widely distributed plant pathogen on a diverse range of host species worldwide. Since the DNA sequence data of N. sphaerica type specimen was not available, Wang et al. determined a collection of Nigrospora isolates from their study as N. sphaerica by comparing morphological characters of vesicular structures and conidial dimensions to the original description. In combined phylogenetic analysis, our isolates of N. sphaerica (JZB 3230013, JZB 3230014, and JZB 3230015) clustered with strong bootstrap support and posterior probability values (90% ML, 99% MP, and 1.00 BYPP). Less than 1% base pair difference was observed in the base pair comparison of ITS, TEF, and TUB2 gene regions between our strain (JZB 3230015) and reference N. sphaerica (LC 6996) strain. Also, similar morphologies were observed between the two strains confirming these two strains as conspecific. This is the first time N. sphaerica has been isolated from Fraxinus sp., Cirsium setosum and Phragmites australi.

Figure 1. Multilocus phylogenetic tree based on the combined ITS, TEF, and TUB2 sequences alignment generated from a maximum likelihood phylogenetic analysis. Bootstrap support values for ML, MP (> 70%), and posterior probabilities (> 0.9) are given at the nodes (ML/MP/PP). The tree is rooted with Arthrinium malaysianum (CBS 102053) and Arthrinium obovatum (LC 4940). (* indicates the ex-type isolates)

Figure 6. Nigrospora sphaerica (JZB 3230015). (a and b) Appearance of leaf spots on host substrate; (c) Enhanced view of leaf spot on the host substrate; (d and e) Upper view (c) and reverse view (d) of culture on PDA; (f) Surface view of the colony on PDA; (g) Colony on PDA; (h) Mature conidia. (i and j) Mature conidia attached to conidiogenous cells. Scale bars: g = 50 μm, h = 10 μm, i = 20 μm, and j = 10 μm.