Montagnula chromolaenicola Mapook & K.D. Hyde, in Mapook, et al., Fungal Diversity 101: 35 (2020)

Index Fungorum number: IF 557298; MycoBank number: MB 557298; Facesoffungi number: FoF 07791; Fig. 1

Saprobic on dead stems of Citrus maxima Merr. Sexual morph: Ascomata 230–340 μm high×180–300 μm diam. (x=300 × 250 μm, n=10), semi-immersed, conspicuous protruding through host surface, solitary, scattered, elliptical or subglobose, most uniloculate, few multiloculate, brown to black, smooth-walled, papillate, with a central ostiole. Ostiole 60–240 μm diam. (x=100 μm, n=20), central, closed, filled with periphyses or empty, consisting of light brown to brown stromatal tissue cells. Peridium 20–50 μm wide, thin-walled, containing of 5–7-layers of transparent to dark brown cells of textura angularis from inner to outside, outermost layer fuses with host tissues. Hamathecium 1.5–3 μm wide (x=2.5 μm, n=50), dense, cylindrical, filamentous, branched, with indistinct septate, gelatinous matrix wraps the trabeculate pseudoparaphyses and clearly match between asci. Asci 30–50×3–5 μm (x=40×5 μm, n=15), 8-spored, bitunicate, thin-walled, clavate, blunt apically, with long slightly curved furcated pedicel. Ascospores 5–10×3–5 μm (x=6×4 μm, n=30), biseriate, ellipsoidal, 1-septate, significant contraction at the septa, tapering from the center to the ends, cells at the upper are slightly wider than lower cells, hyaline when immature, dark brown to brown at maturity, without appendages and mucilaginous sheath. Asexual morph: not observed.

Culture characteristics – Ascospore germinating on PDA within 24 h at room temperature. Colonies on PDA reaching 50 mm diam. after 1 week at 25 °C, circular, flat, smooth, dense and soft, surface view white to light gray from center to edge; reverse with olive-green to light brown center, white edge.

Material examined – China, Guangdong Province, Shaoguan City, Renhua County, Dongtang town, 25° 3′ 50″ N, 113° 39′ 17″ E, on the bark of Citrus maxima (Rutaceae), 25 August 2021, Y.H. Yang (MHZU 22-0065); living cultures ZHKUCC 22-0118, ZHKUCC 22-0119, ZHKUCC 22-0120.

Hosts and distribution – Thailand, on dead stems of Chromolaena odorata (Mapook et al. 2020); China, on the bark of Citrus maxima.

GenBank numbers – ITS: OQ976005, OQ976006, OQ976007; LSU: OQ976015, OQ976016, OQ976017; SSU: OQ976021, OQ976022; tef1-α: OQ980478.

Notes – In the phylogenetic analysis of combined ITS, LSU, SSU and tef1-α sequences of (Fig. 2) our isolates (ZHKUCC 22-0118, ZHKUCC 22-0119, ZHKUCC 22-0120) grouped with ex-type strain of Montagnula chromolaenicola (MFLUCC 17-1469) with ML/BI=78%/1.00 bootstrap support. Morphologically, our collection is similar to type collection of M. chromolaenicola by its central ostiole, asci with long, slightly curved, furcate pedicels, having ellipsoid, 1-septate ascospores, with significant contraction at the upper cell slightly wider and ends tapering to and septa without terminal appendages. We identify our collection as Montagnula chromolaenicola which is the first record on Citrus maxima in China.

Figure 1 – Montagnula chromolaenicola (MHZU 22-0065). a, b Ascomata on the host surface. c Vertical cross section of ascomata. d Cross section through the ostiole. e Peridium. f Pseudoparaphyses. g Asci. h–j Ascospores. k Germinating ascospore. l Surface view of colony on PDA. m Reverse view of colony on PDA. Scale bars: c, d=100 µm, e, f, h–j=20 µm, g, k=30 µm

Figure 2 – The best scoring RAxML tree for combined ITS, LSU, SSU and tef1-α sequence data of species in Didymosphaeriaceae. The tree is rooted with Pleospora herbarum (CBS 191.86) and P. trada (CBS 714.68). The matrix had 871 distinct alignment patterns with 31.98% undetermined characters and gaps. Estimated base frequencies were as follows; A=0.242601, C=0.248012, G=0.271675, T=0.237711; substitution rates AC=1.679480, AG=2.352353, AT=1.661334, CG=1.143072, CT=6.754494, GT=1.0; gamma distribution shape parameter α=0.187527 with a final likelihood value of − 13,247.100866. Ex-type strains are in bold and newly generated sequences are in blue bold. Bootstrap support for ML equal to or greater than 75% and BI equal to or greater than 0.95 are given above the nodes