Seiridium oleae W.L. Li & Jian K. Liu, in Li, Dissanayake, Zhang, Maharachchikumbura & Liu, Journal of Fungi 8(11, no. 1175): 21 (2022)

Index Fungorum number:IF 845410; MycoBank number: MB 845410; Facesoffungi number: FoF 12750

Etymology – Name reflects the host plant genus it was isolated from, Olea.

Holotype – HKAS 123220

Pathogenic on diseased branches of Olea europaea L. Sexual morph: Not observed. Asexual morph: Conidiomata sporodochial, mostly solitary, immersed to semi-erumpent, unilocular, conic or subglobose with flattened base, dark brown to black. Conidiomata wall 24–27 μm thick at sides, not well defined, comprising brown, thin-walled cells of textura angularis, with lighter cells at the base fusing into the host tissue. Conidiophores up to 12 μm, septate, cylindrical, irregularly branched, hyaline or paler brown, thin-walled. Conidiogenous cells 6–8.5 × 2.5–3 μm (x̄ = 7 × 2.5 μm, n = 30), discrete, hyaline, cylindrical, smooth- and thin-walled, proliferating percurrently. Conidia 20–26 × 7.5–9 μm (x̄ = 23 × 8 μm, n = 30), lunate to falcate, curved, 5-septate, rarely 4- or 6-septate, not striate, bearing hyaline appendage at both ends, euseptate, basal cell obconic with a truncate base, hyaline to paler brown, walls smooth, 2.5–3.5 μm; four median cells, 19–22 μm long, smooth, cylindrical to doliiform, brown to dark brown, septa darker than the rest of the cells, second cell from base 4–5.5 μm long, third cell 3.5–4.5 μm long, fourth cell 4–4.5 μm long, fifth cell 4–5 μm long, apical cell conical, hyaline to paler brown, smooth, 1.5–3 μm long, apical appendage single, cylindrical, mostly excentric, 3–5 μm long; basal appendage single, cylindrical, excentric, unbranched, 2.5–3.5 μm long, mean conidium length/width ratio = 2.8:1.

Culture characteristics – Colonies on PDA reaching 20 mm diam. after 2 weeks at 25 ℃. Colony dense, circular, flattened to slightly raised, surface rough, radially furrowed at the centre, smooth at the margin, with edge indented, velvety; from above, whitish at the margin, pale yellowish at the centre; from below, honey yellowish; producing yellowish pigmentation on agar medium.

Materials examined – CHINA, Sichuan Province, Guangyuan city, on a diseased branch of Olea europaea, 20 April 2021, T. Zhang, GL A94 (HKAS 123220, holotype), ex-type living culture, CGMCC3.23558; ibid., GL A94b (HUEST 22.0052, isotype), ex-isotype living culture, UESTCC 22.0051.

Notes – In the phylogenetic analysis, Seiridium oleae groups with S. rosarum (CBS 442.67) with high bootstrap support (ML/BI 98%/0.99). These two species share similar morphological characters in conidia shape and dimension. However, S. rosarum (YMD 328) differs from S. oleae in having longer apical appendage (up to 12 μm vs. 3–5 μm). Additionally, Seiridium oleae is separated from S. rosarum (328) by 10 bp differences in ITS (526 bp), 4 bp differences in LSU (818 bp), 18 bp differences in rpb2 (900 bp), 46 bp differences in tef1-α and 28 bp differences in tub2.

Figure 6 – Seiridium oleae (HKAS 123220, holotype). a Appearance of conidiomata on host substrate. b–f Conidiogenous cells and conidia. g–k Conidia. l Germinating conidium. m, n Upper and reverse view of the colony (on PDA). Scale bars: b–l=10 μm