Dictyoarthrinium musae Samarakoon, Chomnunti & K.D. Hyde, 2020

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 : 106-107

Dictyoarthrinium musae Samarakoon, Chomnunti & K.D. Hyde sp. nov. Figure 2

Etymology.

Name reflects the host genus, Musa ( Musaceae ).

Holotype.

MFLU 20-0437

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 30-140 × 1-2 μm (x¯ 81.5 × 1.6 μm, n = 25), basauxic, arising usually singly from subspherical, subhyaline to light brown conidiophore mother cells, 4.5-4.8 × 4.3-4.5 μm (x̄ = 4.6 × 4.4 μm, n = 10), macronematous, mononematous, straight or flexuous, narrow, cylindrical, rough, subhyaline to pale brown, with thick brown or dark brown transverse septa that appear as stripes with distances of 6.3-5.8 μm at apex and 2.3-3 μm at base of the conidiophore. Conidiogenous cells 4.1-4.5 × 4.3-4.7 μm (x̄ = 4.4 × 4.5 μm, n = 10), blastic, integrated, terminal and intercalary, cylindrical, smooth, denticles absent, hyaline. Conidia 7-11.5 × 6.5-9 μm (x̄ = 8.7 × 7.9 μm, n = 40), solitary, dry, acropleurogenous, simple, square, rounded at the corners, 4-celled, spherical or subspherical, often flattened in one plane, pale to dark brown at maturity, verrucose, with light brown to dark brown warts, immature conidia often 1-celled and subhyaline. Terminal conidium with four cells, sometimes absent or fallen before lateral conidia, mature conidia split along one line of the septa, most conidia arranged obliquely downwards on the conidiophore, conidial formation observed as a bunch starting after conidiophore 1-3 septate.

Culture characteristics.

Conidia germinating on PDA within 18 hrs. Colonies on PDA reaching a diameter of 50 mm after 14 days at 25 °C, slightly raised, hairy, filamentous, moderately dense, middle light grey, periphery white; reverse white to greyish-white.

Material examined.

THAILAND. Chiang Rai. On dead leaves of Musa sp. ( Musaceae ), 7 December 2018, M. C. Samarakoon, BNS265 (MFLU 20-0437, holotype), ex-type living culture (MFLUCC 20-0105); ibid. 20 February 2019, B. C. Samarakoon BNS2239 (MFLU 20-0438, paratype), ex-paratype living culture (MFLUCC 20-0106).

Notes.

Based on BLAST search results of SSU, LSU, ITS and tef 1-α sequence data, Dictyoarthrinium musae (MFLUCC 20-0105 and MFLUCC 20-0106) showed high similarity as follows: SSU = 99.15% to Paraconiothyrium hawaiiense (CBS 120025), LSU = 95.57% to Cylindroaseptospora siamensis (MFLUCC 17-2527), ITS = 98.24% to Kalmusia italica (isolate 5), tef 1-α = 97.75% to Spegazzinia neosundara (MFLUCC 13-0211) with 100%, 100%, 87% and 99% query covers, respectively. In the multigene phylogeny, the Dictyoarthrinium clade was sister to Spegazzinia (ML = 75%, BYPP = 0.98). Within the Dictyoarthrinium clade, D. musae (MFLUCC 20-0105 and MFLUCC 20-0106) separated from the sister taxon, D. sacchari with strong statistical support (ML = 100%, BYPP = 1.00). ITS sequence comparison revealed 7.84% base pair differences between D. musae and D. sacchari (MFLUCC 20-0107), which is in agreement with the new species concept outlined by Jeewon and Hyde (2016). Dictyoarthrinium musae differs from D. sacchari by its unique conidial development in the apex. The terminal conidia of D. musae are always 4-celled and similar in colour to mature lateral conidia. In addition, the terminal conidia of D. musae are sometimes absent or fallen before the lateral conidia. In contrast, the terminal conidia of D. sacchari can be 2-celled or 4-celled, pale brown with respect to lateral mature conidia and always persist on the conidiophore. In addition, the mature conidia of D. musae split along one line of the septa and this specific feature is absent in D. sacchari . Dictyoarthrinium musae has a subhyaline, spherical conidiophore mother cell while D. sacchari has a distinct cup-shaped, brown conidiophore mother cell. Therefore, based on contrasting morphological differences to D. sacchari and strong statistical support from our molecular phylogeny, D. musae is herein introduced as a new species.

Figures

Figure 2. Dictyoarthrinium musae (MFLU 20 - 0437, holotype) a conidia on the host b conidiophore and conidia with conidiophore mother cell c-f conidia with conidiophores on stalk g developmental stage of an immature lateral conidium h four-celled terminal conidium i conidiophore j conidiophores and conidia with terminal conidium k, l conidiophores without terminal conidium m attachment of a mature lateral conidium n-q warted four-celled mature conidia r, s mature conidia that split at septa t colony on PDA after 21 days. Scale bars: 500 μm (a); 50 μm (b, c); 20 μm (d-g, i); 10 μm (h); 5 μm (j-s).