Acrocalymma walkeri (Shoemaker, C.E. Babc. & J.A.G. Irwin) Crous & Trakun., IMA Fungus 5(2): 407 (2014)
MycoBank number: MB 810840; Index Fungorum number: IF 810840, Facesoffungi number: FoF 12929, Fig. *
Saprobic on dead twigs attached to Magnolia sp. Sexual morph: Ascomata 180–220 μm high, 155–170 μm diam. ( = 200 × 165 µm, n = 10), scattered, immersed to erumpent, globose or subglobose, dark brown to black, elongated neck, with minute papilla, ostiolate. Peridium 10–15 μm wide ( = 12 μm, n = 10), composed of several layers of small, flattened, brown to dark brown pseudoparenchymatous cells, cells towards the inside hyaline to lightly pigmented, arranged in a textura angularis, at the outside, darker, fusing and indistinguishable from the host tissues. Hamathecium composed of 1–2 μm wide, numerous, filamentous, branched, septate, pseudoparaphyses. Asci 60–95 × 7–10 μm ( = 80 × 8.5 μm, n = 20), 8-spored, bitunicate, fissitunicate, cylindrical, with a short, narrowed, furcate pedicel, and with a small ocular chamber. Ascospores 16–20 × 3–5 μm ( = 18 × 4 μm, n = 30), obliquely biseriate, hyaline, fusiform with acute ends, 1-septate, constricted at the septum, upper cell slightly wider than lower cell, smooth-walled. Asexual morph: Not observed.
Culture characteristics – Colonies on PDA reaching 22 mm diameter after 1 week at 25°C, colonies from above: circular, margin entire, dense, slightly raised, cottony to fairy fluffy appearance, white at the margin, light grey in the centre; reverse: cream at the margin, grey in the centre.
Material examined – Thailand, Chiang Mai Province, dead twigs attached to Magnolia sp. (Magnoliaceae), 15 November 2017, N. I. de Silva, NI214 (MFLU 18-1311), living culture, MFLUCC 18-0547.
Known hosts and distribution – Medicago sativa (Fabaceae) in Australia (Shoemaker et al. 1991), dead twigs attached to Magnolia sp. in Thailand (this study).
GenBank numbers – LSU: OK655821, ITS: OL413441.
Notes – The morphological characteristics of our collection (MFLUCC 18-0547) resembles Acrocalymma walkeri in having immersed to erumpent, globose or subglobose, dark brown to black ascomata (180–220 × 155–170 μm vs 160–180 μm diam.), cylindrical asci (60–95 × 7–10 μm vs 50–80 × 8–11 μm) and hyaline, fusiform, 1-septate ascospores (16–20 × 3–5 μm vs 19–22 × 4.5–5.5 μm) (Shoemaker et al. 1991). Multi-gene phylogeny also indicates that our collection (MFLUCC 18-0547) nested with A. walkeri with 86% ML, 1.00 BYPP support (Fig. 4). Therefore, based on both morphology and phylogeny evidence, we report our collection as a new host record of A. walker from Magnolia species in Thailand.
Figure * – Acrocalymma walkeri (MFLU 18-1311). A The specimen. b, c Appearance of ascomata on substrate. d, e Vertical sections through ascoma. f Peridium. g Pseudoparaphyses. h–j Asci. k–n Ascospores. Scale bars: a = 500 μm, b = 200 μm, c = 100 μm, d, e = 50 μm, f = 5 μm, h–j = 20 μm, k–n = 5 μm.