Paramicrothyrium bambusae Tennakoon, S. Hongsanan & S. Lumyong, 2023

Tennakoon, Danushka S., Hongsanan, Sinang, De Silva, Nimali I., Suwannarach, Nakarin & Lumyong, Saisamorn, 2023, Molecular phylogeny and morphological characterization of Paramicrothyrium bambusae sp. nov. and Tumidispora thailandica sp. nov. from leaf litter, Phytotaxa 578 (1), pp. 112-124 : 117

Paramicrothyrium bambusae Tennakoon, S. Hongsanan & S. Lumyong sp. nov. ( FIGURE 2 )

Index Fungorum Number: IF559725; Facesoffungi number: FoF11795

Etymology:—Name reflects the host genus Bambusa .

Holotype:— MFLU 19-2729

Epiphytic on the upper surface of dead leaves of Bambusa vulgaris Schrad. (Poaceae) , visible as small black dots. Sexual morph: Undetermined. Asexual morph: Thyriothecia 90–120 × 100–130 μm (x = 110 × 112 µm, n = 10), solitary, scattered, superficial, flattened, circular, dark brown to black, easily be removed from the substrate, poorly developed basal layer, with irregular, central ostiole, dark brown, irregularly rounded at the margin. Upper wall comprises brown cells of textura angularis, radiating in irregular, parallel lines from center to the outer rim. Conidiogenous cells evanescent. Conidia 3–4 × 1–2 µm (x = 3.7 × 1.2 μm, n = 30), hyaline, cylindrical with obtuse ends, unicellular, minute guttulate, straight or slightly curved, smooth-walled.

Culture characteristics:— Colonies on PDA, 10–12 mm diam. after 4 weeks at 25 °C, colonies from above: medium dense, circular, raised, cottony, surface smooth, entire margin, white to cream at margin, white at center; reverse: white to yellowish at margin, light brown at center. Mycelium white to cream with tufting.

Material examined:— Thailand, Chiang Mai, dead leaves of Bambusa vulgaris (Poaceae) , 28 September 2018, D.S. Tennakoon, ADS046A (MFLU 19-2729, holotype); ex-type living culture, SDBR-CMU436. ibid. 29 September 2019, ADS046B (NCYU 19-0085, paratype); ex-paratype living culture, SDBR-CMU437.

GenBank numbers:—MFLU 19-2729: ITS: ON751741 ; NCYU 19-0085: ITS: ON751742 .

Notes:—The phylogeny indicates that Paramicrothyrium bambusae (MFLU 19-2729 and NCYU 19-0085) forms a distinct lineage sister to P. chinensis isolates (IFRDCC2258 and IA20) with robust statistical support (100% ML, 99% MP, 1.00 BYPP, FIGURE 1 ). The morphology of P. bambusae fits well with the type species in having circular, dark brown to black thyriothecia with an irregular ostiole, without a darkened ring ( Wu et al. 2011). However, we were unable to compare P. chinensis to the asexual morph of P. bambusae , since only the sexual morph was available for that species ( Wu et al. 2011). Therefore, we compared the base pair differences between P. bambusae and P. chinensis and there were 25 base pair differences (4.14%) across 603 nucleotides across the ITS (+ 5.8S) gene region. In addition, P. bambusae has smaller thyriothecia (90–120 × 100–130 μm), whereas P. chinensis has significantly larger thyriothecia (420–590 μm diam.) ( Wu et al. 2011). However, further collections are needed to clarify the sexual and asexual connection of Paramicrothyrium species.

Figures

FIGURE 1. Phylogram generated from maximum likelihood analysis is based on combined LSU and ITS sequence data.The tree is rooted with Kirschsteiniothelia lignicola (MFLUCC 10-0036). The ex-type strains are indicated in bold and the new isolates are indicated in red. Bootstrap support values ≥70% from the maximum likelihood (ML), maximum parsimony (MP) and Bayesian posterior probabilities (BYPP) values ≥0.95 are given above the nodes, respectively.

FIGURE 2. Paramicrothyrium bambusae (MFLU 19-2729, holotype). a, b Thyriothecia on the surface of the leaf (yellow arrows). c Close-up of Thyriothecium. d, e Thyriothecia when, viewed in squash mount. f The upper wall of thyriothecium, when viewed in squash mount. g–i Conidia. j The upper view of colony. k The lower view of colony. Scale bars: d, e = 50 μm, f = 20 μm, g–i = 3 μm.