Acrocalymma magnoliae
Acrocalymma magnoliae N.I. de Silva, S. Lumyong & K.D. Hyde, Mycosphere 13(1): 967 (2022)
Index Fungorum number: IF559515; Facesofungi number: FoF10713
Saprobic on dead twigs of Parashorea chinensis. Sexual morph: Ascomata 190–230 μm high, 140–200 μm diam., (x̅ = 210 × 170 μm, n = 5), immersed under host tissue, solitary or scattered, subglobose to elliptical, uni loculate, coriaceous, black. Ostioles central. Peridium 8–13 μm wide, 3–4-layered, composed of dark brown outer layers and hyaline inner layers, thick walled cells of textura angularis to textura prismatica. Hamathecium 2.5–4 μm wide, comprising numerous branching, septate, hyaline pseudoparaphyses. Asci 100–140 × 15–18 μm (x̅ = 117 × 16 μm, n = 20), 8 spored, bitunicate, fissitunicate, clavate to cylindric clavate, slightly curved, with a furcate to truncate pedicel, apically rounded. Ascospores 25–30 × 6–7 μm (x̅ = 27.1 × 6.3 μm, n = 30), overlapping 1–2 seriate, hyaline, fusiform with acute ends, slightly curved, 3 septate, slightly constricted at the septum, the second cell of the ascospore from the apex wider than other cells, smooth walled, large guttules in each cell, without mucilaginous sheath. Asexual morph: Coelomycetous. Conidiomata 135–160 × 200–230 μm (x̅ = 145 × 215 μm, n = 10), subglobose, dark brown or black, semi-immersed to erumpent, solitary, scattered without ostioles. Conidiomatal wall 20–35 μm wide, composed of several layers of small, flattened, brown to dark brown pseudoparenchymatous cells, cells in the inner layer lightly pigmented, arranged in a textura angularis, in the outer layer, darker, fusing cells and indistinguishable from the host tissues. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 7–12 × 3–7 μm (x̅ = 10 × 5μm, n = 10), phialidic, hyaline, smooth, ampulliform to doliiform, proliferating with visible periclinal thickening at apex. Conidia 22–30 × 5–7 μm (x̅ = 26 × 6 μm, n = 40), hyaline, cylindrical to fusoid, smooth, guttulate, thin-walled, straight, apex obtuse, unicellular, 2–3 pseudosepta present with flaring mucoid. Apical appendage visible in water mounts (de Silva et al. 2022).
Culture characteristics: Ascospores germinating on PDA within 24 h at room temperature (25 °C). Germ tubes produced from the basal and apical cells of the ascospore. Colonies on PDA, reaching 50 mm diameter after two weeks at 20–25 ℃, mycelia superficial, circular, fimbriate, marginal hyphae emission, dense, flat, gray with white spots; reverse, black.
Material examined: China, Yunnan Province, Xishuangbanna, on dead woody twigs of Parashorea chinensis (Dipterocarpaceae), 15 December 2019, G.C. Ren, XS23 (HKAS 122776), living culture KUMCC 21 0674.
Known distribution: On dead twigs attached to Magnolia sp. (Magnoliaceae) and Anomianthus dulcis (Annonaceae) in Thailand (de Silva et al. 2022), on dead woody twigs of Parashorea chinensis (Dipterocarpaceae) in China (This study).
GenBank numbers: LSU: OQ170830, ITS: OQ158910, SSU: OQ168190, tef1-α: OR613416.
Notes: Acrocalymma magnoliae was introduced by de Silva et al. (2022) based on its distinct morphology and analysis of a combined SSU, LSU, and ITS dataset. In the phylogenetic analysis, our isolate (KUMCC 21 0674) clustered with the ex-type strain of A. magnoliae (MFLUCC 18-0545) with 100% ML bootstrap support and 1.00 BYPP value. Sequence comparison for the ITS region between our isolate (KUMCC 21 0674) and A. magnoliae (MFLUCC 18-0545) showed no significant base pair differences. We did not obtain the asexual morph from our isolate (KUMCC 21 0674). Therefore, the morphological comparison between our isolate and Acrocalymma magnoliae is not possible. However, sexual morphs of Acrocalymma chuxiongense, A. hongheense, A. medicaginis, A. pterocarpi and A. walker have been described by Shoemaker et al. (1991), Jayasiri et al. (2019), Mapook et al. (2020), Mortimer et al. (2021), and Liu & Zeng (2022). The morphology of our isolate (KUMCC 21-0674) aligns with the sexual morph criteria given for Acrocalymma species but differs from known species. Based on the phylogenetic analyses, our saprobic isolate (KUMCC 21-0674) is introduced as the first record of Acrocalymma magnoliae on the woody litter of Parashorea chinensis (Dipterocarpaceae) in China. Moreover, our collection is the first sexual morph recording in A. magnolia.
Figure 1. Phylogram generated from ML analysis based on SSU, LSU, ITS and tef1-α sequence data, representing Acrocalymmaceae. Related sequences are obtained following Jayasiri et al. (2019), Mortimer et al. (2021) and Calabon et al. (2023b). Thirty-seven strains are included in the combined analyses, which comprise 3301 characters for SSU, LSU, ITS and tef1-α alignment. Boeremia exigua (CBS 431.74) and B. foveata (CBS 341.67) were used as the outgroup taxa. The best-scoring RAxML tree with a final likelihood value of -9402.946202 is presented. The matrix had 563 distinct alignment patterns with 39.03% of undetermined characters or gaps. Estimated base frequencies were as follows; A = 0.245541, C = 0.224280, G = 0.269962, T = 0.260217; substitution rates AC = 1.707655, AG = 3.127362, AT = 2.668674, CG = 1.135340, CT = 8.212547, GT = 1.0000. The tree topology of the ML analysis is similar to the Bayesian analysis. Bootstrap values for ML equal to or greater than 70% and BYPP values greater than 0.95 (the rounding of values to 2 decimal proportions) are labelled on the nodes. Strains of the newly described species are in blue, while type strains are in bold.
Figure 2. Acrocalymma magnoliae (HKAS 122776). a Material examined. b, c Appearance of ascomata on the host substrate. d Section of an ascoma. e Peridium. f Pseudoparaphyses. g–k Asci. l–p Ascospores. q, r Culture characters on PDA (q = from above, r = from below). Scale bars: d = 150 μm, e = 20 μm, f = 10 μm, g–k = 30 μm, l–o = 15 μm, q, r = 30 mm.
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