Dictyoarthrinium sacchari (J.A. Stev.) Damon, Bull. Torrey bot. Club 80: 164 (1953)

Samarakoon, Binu C., Wanasinghe, Dhanushka N., Samarakoon, Milan C., Phookamsak, Rungtiwa, McKenzie, Eric H. C., Chomnunti, Putarak, Hyde, Kevin D., Lumyong, Saisamorn & Karunarathna, Samantha C., 2020, Multi-gene phylogenetic evidence suggests Dictyoarthrinium belongs in Didymosphaeriaceae (Pleosporales, Dothideomycetes) and Dictyoarthrinium musae sp. nov. on Musa from Thailand, MycoKeys 71, pp. 101-118 : 107-110

Dictyoarthrinium sacchari (J.A. Stev.) Damon, Bull. Torrey bot. Club 80: 164 (1953) Figure 3

Description.

Saprobic on dead leaves of Musa sp. Sexual morph: Undetermined. Asexual morph: Colonies compact or effuse, black, often pulvinate. Mycelium superficial, a close network of branched and anastomosing hyphae. Stromata none. Setae and hyphopodia absent. Conidiophores 50-110 × 1-2 μm (x̄ = 72.0 × 1.6 μm, n = 15), basauxic, arising from cup-shaped, brown, distinct conidiophore mother cells, 3.4-4.4 × 2.9-4.7 μm (x̄ = 4 × 3.7 μm, n = 10), macronematous, mononematous, usually straight or flexuous, narrow, cylindrical, rough-walled, subhyaline to pale brown, with dark brown transverse septa as stripes with distances of 6.3-5.8 μm at apex and 2.3-3 μm at base of the conidiophore. Conidiogenous cells 4-4.5 × 4.3-4.7 μm (x̄ = 4.4 × 4.5 μm, n = 10), blastic, integrated, terminal and intercalary, cylindrical, smooth, hyaline. Conidia at maturity 8.5-11.5 × 8.5-10 μm (x̄ = 9.9 × 9.3 μm, n = 40), solitary, dry, acropleurogenous, simple, square, rounded at the corners, 4-celled, but difficult to distinguish the cells due to their blackish-brown nature, spherical or subspherical, often flattened in one plane, blackish-brown at maturity, with brown warts on surface of the cells, terminal conidium always 4-celled or 2-celled, light brown when compared with lateral conidia, most conidia arranged perpendicular to the conidiophore, some directed obliquely upwards.

Culture characteristics.

Conidia germinating on PDA within 18 hrs. Colonies on PDA reaching a diameter of 55 mm after 14 days at 25 °C, raised, moderately dense, entire margined, brownish-grey at maturity; reverse white to greyish-white.

Material examined.

Thailand, Chiang Mai. On mid-rib of a dead leaf of Musa sp. ( Musaceae ), S. Phongeun, 18 July 2018, BNS2287, (MFLU 20-0439), living culture MFLUCC 20-0107.

Notes.

Based on BLAST search results of SSU, LSU, ITS and tef 1-α sequence data, our strain (MFLUCC 20-0107) showed high similarity to the taxa in GenBank as follows (SSU = 99.26% to Paraconiothyrium brasiliense (isolate GF1), LSU = 96.14% to Alloconiothyrium aptrooti (CBS 981.95), ITS = 93.00% to Kalmusia italica (MFLUCC 13-0066). In the multigene phylogeny, MFLUCC 20-0107 groups with Dictyoarthrinium sacchari , sister to D. musae with strong statistical support (ML = 100%, BYPP = 1.00). Our strain shares similar morphological features with D. sacchari (Subramanium 1952; Ellis 1971) and did not differ significantly. There are slight differences in conidial dimensions and the length of conidiophores of our collection and other D. sacchari collections by previous studies. Conidial dimensions and the length of conidiophores may differ due to diverse environmental effects and host associations. LSU sequence data of D. sacchari (CBS 529.73) are identical with our strain (MFLUCC 20-0107). Unfortunately, ITS, SSU and tef 1-α sequence data of CBS 529.73 are not available in GenBank to compare with our strain. LSU data of Dictyoarthrinium musae have 2.24% of base pair difference with D. sacchari (CBS 529.73 and MFLUCC 20-0107). Dictyoarthrinium sacchari was reported on Musa sp. from Thailand in Lumyong et al. (2003) without morpho-molecular justifications. In this study, we document D. sacchari with detailed morphological illustrations, description, herbarium material and a living culture coupled with DNA sequence data (SSU, LSU, ITS) for a better taxonomic resolution.

Figures

Figure 3. Dictyoarthrinium sacchari (MFLU 20 - 0439) a conidia on the host b developmental stage of terminal conidium attached to the conidiophore c-f Conidiophores and conidia (e, with distinct mother cell) g, h mature conidiophores with four-celled terminal conidium i conidiophore with two celled terminal conidium j developmental stages of conidia on conidiophore k colony on PDA after 21 days l-q conidia. Scale bars: a = 1000 μm (a); 20 μm (b, j); 50 μm (c-i); 5 μm (l-q).