Spegazzinia musae Samarakoon, Phookamsak, Wanas., Chomnunti & K.D. Hyde, 2020

Samarakoon, Binu C., Phookamsak, Rungtiwa, Wanasinghe, Dhanushka N., Chomnunti, Putarak, Hyde, Kevin D., McKenzie, Eric H. C., Promputtha, Itthayakorn, Xu, Jian-Chu & Li, Yun-Ju, 2020, Taxonomy and phylogenetic appraisal of Spegazzinia musae sp. nov. and S. deightonii (Didymosphaeriaceae, Pleosporales) on Musaceae from Thailand, MycoKeys 70, pp. 19-37 : 19

Spegazzinia musae Samarakoon, Phookamsak, Wanas., Chomnunti & K.D. Hyde sp. nov. Figure 3

Etymology.

The name reflects the host genus, Musa ( Musaceae ).

Holotype.

MFLU 19-2907

Description.

Saprobic on a dead leaf of Musa sp. Sexual morph Undetermined. Asexual morph Hyphomycetous. Sporodochia dark, dense, dry, powdery, velvety, 1-2 mm diameter. Conidiophore mother cells 3.4-5.8 × 3.7-4.7 μm (x̄ = 4.6 × 4.1 μm, n = 10) subhyaline or light brown, doliiform or subspherical. Conidiophores usually short to long bearing two types of conidia referred to here as α and β. Conidiophores of α conidia up to 40-85 × 0.8-2.5 μm (x̄ = 64 × 21.7 μm, n = 15), pale brown or dark golden brown, rough-walled, hyaline at bottom near the conidiophore mother cell, pale brown at middle, dark golden brown at top near conidial cells, erect or flexuous, narrow and long, generally unbranched, rarely branched. Conidiophores of β conidia 0.7-3.5 × 1.5-3 μm (x̄ = 1.9 × 2.3 μm, n = 15) short, erect, unbranched, hyaline when immature, subhyaline or hyaline at maturity. Conidiogenous cell development basauxic, forming a single, terminal holoblastic conidium at the apex of conidiophore. Conidial development holoblastic. Conidia solitary, dry, two types: α conidia stellate, 15-22.7 × 14.5-20.5 μm (x̄ = 18.8 × 17.8 μm, n = 15), 4-6 celled, each cell globose to subglobose, deeply constricted at the septa, conspicuously spinulate, 4-6 spines, each 2-8 μm long arise from surface of each cell. β conidia disc-shaped, initially hyaline, 4-celled, each cell slightly turbinate in shape, rough-walled, crossed septate, becoming brown to dark brown at maturity, each cell turbinate, crossed-septate, smooth-walled, light brown at the center near the septa, dark brown at periphery in constricted areas, 9.3-14.2 × 8.4-12.5 μm (x̄ = 12.7 × 10.8 μm, n = 40), somewhat obovoid, deeply constricted at the septa, flat from side view, frequently with attached conidiogenous cells when splitting from the conidiophores.

Culture characteristics.

Conidia germinating on PDA within 12-15 h, germ tubes produced from one or several cells. Colonies growing on PDA, reaching a diameter of 46 mm after 14 d at 25 °C, greyish white, unevenly raised, surface rough, moderately dense, radially striated at center, margin crenulate; reverse white to greyish white.

Material examined.

Thailand, Nan Province, on a dead leaf of Musa sp. ( Musaceae ), 12 September 2018, B.C. Samarakoon, BNS 069 (MFLU 19-2907, holotype), ex-type living culture MFLUCC 20-0001.

Notes.

Based on BLASTn search results of SSU, LSU, ITS and TEF1-α sequence data, Spegazzinia musae showed a high similarity (SSU = 98.24%, LSU = 98.92%, ITS = 96.91%, TEF1-α = 98.11%) to S. neosundara (MFLUCC 15-0456). In the multigene phylogeny, S. musae groups as a sister taxon to S. deightonii with strong statistical support (77% ML, 0.99 BYPP) (Figure 1 ). Also, ITS sequence comparison revealed 3.75% base pair differences between S. musae and S. deightonii , which is in agreement with the species concept outlined by Jeewon and Hyde (2016). Besides, S. musae has contrasting morphological features to S. deightonii in both kinds of conidia. The disk-shaped conidia of S. musae are 4-celled and do not bear spines at the periphery of cells, while the disc-shaped conidia of S. deightonii are 8-celled and spiny. Based on contrasting morphological differences and significant statistical support from our molecular phylogeny, Spegazzinia musae is introduced as a new species.

Figures

Figure 1. Maximum likelihood tree revealed by RAxML from an analysis of SSU, LSU and ITS and TEF 1 - α sequence data of selected genera of family Didymosphaeriaceae, showing the phylogenetic position of Spegazzinia musae (MFLUCC 20 - 0001) and S. deightonii (MFLUCC 20 - 0002). ML bootstrap supports (≥ 60 %) and Bayesian posterior probabilities (≥ 0.95 BYPP) are given above in the branches, respectively. The tree was rooted with Pleospora herbarum and Stemphylium botryosum (Pleosporaceae). Strains generated in this study are indicated in red-bold. Ex-type species are indicated in bold. The scale bar represents the expected number of nucleotide substitutions per site. A best scoring RAxML tree is shown with a final ML optimization likelihood value of - 13516.66. The matrix had 795 distinct alignment patterns, with 33.60 % of undetermined characters or gaps. Estimated base frequencies were: A = 0.239862, C = 0.245185, G = 0.277025, T = 0.237927; substitution rates AC = 1.626982, AG = 2.468452, AT = 1.211822, CG = 1.092437, CT = 6.295657, GT = 1.000000; proportion of invariable sites I = 0.484119; gamma distribution shape parameter α = 0.445929.

Figure 3. Spegazzinia musae (MFLU 19 - 2907, holotype) a-c fungal colonies on host surface d mature conidia e conidiophore of α conidia with the mother cell f, g α conidia h-q β conidia r colony on PDA after 28 days. Scale bars: 200 μm (a-c), 20 μm (d-g, j), 10 μm (h, i, k-q).