Nigrospora rubi Mei Wang, F. Liu, P.W. Crous & L. Cai. Persoonia 39:135 (2017)

Index Fungorum number: IF 820801; Facesoffungi number: FoF 06598.

Pathogenic or saprobic on leaves of Fraxinus sp. (Oleaceae). Asexual morph: Hyphae smooth, branched, septate, and hyaline. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 5.2–7.4 × 6.6–7.3 μm diam. (x̄ = 6.7 × 6.9 μm, n = 30), clustered on hyphae, unbranched, ampulliform, short, and squat pale brown. Conidia 7.9–10.7 × 10–12.1 μm diam. (x̄ = 9.58 × 11.17 μm, n = 50), solitary, spherical or subglobose, black, shiny, smooth, and aseptate. Sexual morph: Undetermined.

Culture characteristics – Colonies on PDA reach 9 cm diam. after 6 d at 25 C, circular, entire margined, velvety to lanose, surface initially white, becoming dark olive-green to gray with age and reverse initially white, and turning leek green when mature.

Material examined – China, Shandong Peninsula, on living leaves of Fraxinus sp., October 7 2017, Yuanyuan Hao (JZBH 3230012), living culture JZB 3230012, and KUMCC 19-0242.

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

Notes – Based on multi-locus molecular phylogeny, our isolate of N. rubi (JZB 3230012) forms a strongly supported lineage (100% ML, 100% MP, and 1.00 BYPP) with N. rubi as the type species (CGMCC 3.18326) (Figure 1) and the base pair comparison between these two strains exhibit 100% similarity in ITS and 98.8% similarity in TEF gene region. The TUB2 gene sequence could not be obtained for our strain (JZB 3230012). The conidial measurements were slightly larger (11.5  16.5 μm) in the type specimen (CGMCC 3.18326) compared to our strain (JZB 3230012, 9.58  11.17 μm). The culture characteristics slightly deviate in colour; the ex-type culture (CGMCC 3.18326) was initially white, becoming black with age and reverse smoke grey in patches, whereas our strain shows initially white surface becoming dark olive-green to grey with age and initially white reverse turning leek green when mature (JZB 3230012). Nigrospora rubi has been previously isolated from the Rubus species. This is the first time N. rubi has been isolated from Fraxinus sp.

Figure 1. Multilocus phylogenetic tree based on the combined ITS, TEF1, 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 5. Nigrospora rubi (JZB 3230012). (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, j, and k) Mature conidia attached to conidiogenous cells; (i) Mature conidia. Scale bars: g = 100 μm, h = 10 μm, i = 20 μm, j, k = 10 μm.