Phyllosticta musaechinensis

Phyllosticta musaechinensis S.P. Wu, Zuo Y. Liu & K.D. Hyde, in Wu et al., Phytotaxa 188(3): 142 (2014)                                                                                 

Index Fungorum number: IF 806057; Facesoffungi number: FoF 12965

Saprobic on fallen leaves of Musa sp. Sexual morph: Not observed. Asexual morph: Coelomycetous. Conidiomata 50–160 × 50–160 μm (x̄=90 × 95 μm, n=20), solitary, uniloculate, globose to subglobose, scattered or gregarious, semi-immersed, conspicuous on host surface, black. Pycnidial wall 2.75–14.5 μm wide (x̄=7.7 μm, n=30), comprising 1–2 layers of thick-walled textura angularis cells, outer layer dark brown to black, inner layer pale brown. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 6–14 × 4.5–9 μm (x̄=9.8 × 6.4 µm, n=25), subglobose or ellipsoidal or ovoid, guttulate, aseptate, hyaline, smooth. Conidia 13–18 × 8.5–12.5 µm (x̄=15.5 × 10.0 μm, n=60), solitary, ellipsoidal to obovoid, guttulate, verruculose or with a single large central guttule, aseptate, hyaline, smooth-walled, tapering towards a truncate base and broader apex, surrounded by a mucilaginous sheath; sheath, thicker on both sides, 1.2–4.7 μm thick (x̄=2.6 μm, n=60), thinner at the apex and base, 0.2–2.0 μm thick (x̄=1.0 μm, n=25), with a hyaline, apical mucoid appendage. Appendages 4.7–11 × 0.8–1.2 μm (x̄=7.4 × 1.0 μm, n=10), flexuous, unbranched, straight to curved, tapering towards a rounded tip.

Material examined: THAILAND. Chiang Mai Province: forests around the Mushroom Research Center, on fallen dead leaves of Musa sp. (Musaceae), 1 April 2021, D. Gomdola, Y-FB-P2 (MFLU 22-0176).

Distribution: Thailand.

GenBank accession numbers: ITS = OP693476, LSU = OP693472, TEF-1α = OQ189918, ACT = OQ189922.

Notes: Our strain MFLU 22-0176 clusters with P. musaechinensis (GZAAS 6.1247 and GZAAS 6.1384) with strong support (100%ML, 100%MP, 1.00PP), and resides in the P. capitalensis species complex (Fig. 2). Characters of the conidia match the morphological species concept of Phyllosticta. Upon comparison of the morphology, the conidial length of MFLU 22-0176 ranges from 13–18 μm, which is similar to that of the type strain of P. musaechinensis (GZAAS 6.1247), ranging from 14–18 μm. Other differences and similarities between our strain (MFLU 22-0176) and the type of P. musaechinensis are given (Table 1).

MFLU 22-0176 and all other species in that clade (P. cavendishii, P. maculata, P. musaechinensis, P. musarum) were isolated from Musa spp. Excluding gaps, a pairwise nucleotide comparison of MFLU 22-0176 with the type of P. musaechinensis (GZAAS 6.1247) shows differences of 1.8% across ITS (532 nucleotides), 0.52% across ACT (195 nucleotides), and 0.32% across TEF-1α (340 nucleotides).

Based on the morphological and phylogenetic species recognition criteria detailed in Jayawardena et al. (2021), we establish our strain (MFLU 22-0176) as a new geographical record for P. musaechinensis in Thailand.

Fig 1. Phyllosticta musaechinensis (MFLU 22-0176). a–b. Appearance of conidiomata on leaves of Musa sp. c–d. Close up of conidiomata on substrate. e–f. Section through conidiomata showing pycnidial wall. g–i. Conidiogenous cells and developing conidia. j–n. Conidia surrounded by mucilaginous sheath, with an apical appendage. Scale bars: c = 2 mm, d = 500 μm, e = 100 μm, f = 50 μm, g–n = 10 μm.

Table 1. Morphological comparison of MFLU 22-0176 with the type of P. musaechinensis (GZAAS 6.1247).