Synonym:— Rhytidhysteron erioi Ekanayaka & K.D. Hyde, in Hyde et al., Fungal Diversity 100: 21 (2020)

Saprobic on dead twig of Murraya paniculate (L.) Jack. Sexual morph: Ascomata 520–1180 µm long, 310–690 µm wide, 225–600 µm high (x = 869 × 497 × 401 µm, n = 10), hysterothecial when young, slightly opened becoming irregularly apothecioid when mature, superficial or slightly erumpent from the substrate, coriaceous, scattered, elongate, elliptic, opening by a longitudinal slit, closed at first and opening at maturity, with perpendicularly striate along the axis, dark brown to black with dark orange at the center. Exciple 60–125(–170) µm wide, composed of cells of textura globulosa to textura angularis, an outer layer pale brown to brown, thick-walled, an inner layer hyaline, thin-walled, continuous to the base (hypothecium). Hamathecium comprising 2–3 µm wide, numerous, cylindrical to filiform, septate, branched, cellular pseudoparaphyses, fused and slightly swollen at the apex, enclosed in a gelatinous matrix, forming pale red to reddish brown epithecium above the asci when mounted in water, becoming margenta epithecium when mounted in KOH. Asci 135–166 × 9–13 µm (x = 152 × 11 µm, n = 16), 6–8-spored, bitunicate, cylindrical, straight or slightly curved, with a short pedicel, rounded at the apex, with an ocular chamber. Ascospores 20–25 × 7–9.5 µm (x = 22.5 × 8.5 µm, n = 30), uniseriate, slightly overlapping, hyaline to yellowish brown when immature, becoming brown to dark brown when mature, broadly fusiform, rounded to slightly pointed at both ends, 1-septate when immature, becoming 3-euseptate when mature, slightly constricted at the central septum, straight or slightly curved, smooth-walled, with small guttules. Asexual morph: Undetermined.

Culture characteristics:— Ascospores germinating on PDA within 24 hours at room temperature and produced germ tubes from the one or end of ascospores. Colonies on PDA circular, medium dense, slightly raised, smooth surface, edge entire, velvety to woolly, whitish grey at the surface; producing reddish-brown pigment on agar.

Material examined:— THAILAND, Chiang Mai Province, Muang District, on dead twig of Murraya paniculata (Rutaceae), 4 January 2023, S. Hongsanan, KW01 (CMUB 4004), living culture SDBR-CMU473.

Host and distribution:— Alnus nepalensis (Betulaceae, China; Du et al. 2023), Bruguiera sp. (Rhizophoraceae, Thailand; Dayarathne et al. 2020, Chromolaena odorata (Asteraceae, Thailand; Mapook et al. 2020), Murraya paniculata (Rutaceae, Thailand; this study).

Notes:— In a BLASTn search, the LSU and TEF1 sequences showed 99.89%, and 99.36% similarities to Rhytidhysteron bruguierae strain MFLUCC 18-0398 (MN017833 and MN077056) and the ITS sequences showed 100% similarity to R. bruguierae strain MFLUCC 17-1502 (MN632458), MFLUCC 17-1509 (MN632460), MFLUCC 17-1515 (MN632457) and KUMCC 21-0484 (OP494090). Phylogenetic analyses of a combined LSU, ITS, SSU and TEF1 revealed that our strain (SDBR-CMU473) grouped with R. bruguierae with 100% ML and 1.00 PP statistical support (FIGURE 1), closely related with MFLUCC 17-1509 and MFLUCC 17-1511 strains. The comparison of the LSU region showed that R. bruguierae (MFLUCC 18-0398; type strain) is not significantly different from our strain (SDBR-CMU473) and the comparison of the TEF1 region of these two strains revealed less than 1.5% nucleotide differences [6/921 bp (0.65%)]. In addition, the comparison of LSU and ITS regions showed that our strain is not significantly different from strains MFLUCC 17-1509 and MFLUCC 17-1511. Unfortunately, ITS sequences of strain MFLUCC 18-0398 and TEF1 sequences of strains MFLUCC 17-1509 and MFLUCC 17-1511 were not available for comparison. Rhytidhysteron bruguierae was introduced by Dayarathne et al. (2020) as saprobic on decaying wood of Bruguiera sp. (Rhizophoraceae) in Thailand. The morphology of our strain is similar to R. bruguierae described by Dayarathne et al. (2020). Although our strain has longer asci than those described in the original description (135–166 × 9–13 µm vs. 128–148 × 10–14 µm), this variation can occur among species (Senanayake et al. 2020). Therefore, we identify our collection as R. bruguierae and this is the first report of this species on Murraya paniculata.

In our phylogenetic analysis (FIGURE 1), Rhytidhysteron erioi (MFLU 16-0584) clusters with R. bruguierae with 100% ML and 1.00 PP statistical support, which is consistent with the results of previous studies (Ren et al. 2022, Xu et al. 2022, Du et al. 2023). Rhytidhysteron erioi (Hyde et al. 2020) has comparatively larger asci (140–200 × 9–16 µm vs. 128–148 × 10–14 µm) and larger ascospores (22–28 × 9–11 µm vs. 18–22 × 7–9 µm) compared to the type strain of R. bruguierae (Dayarathne et al. 2020). The differences in asci and ascospore sizes may be due to variations among the species as well as variations in environment, host and, distribution (Lücking 2019, Senanayake et al. 2020). The comparison of the ITS region showed that R. erioi differs from the other strains of R. bruguierae by 1/513 bp (0.1%), while the comparison of the TEF1 regions showed that R. erioi (MFLU 16-0584) differs from R. bruguierae (MFLUCC 18-0398) by 3/733 bp (0.4%). Considering the morpho-molecular data analysis, we treat R. erioi as a synonym of R. bruguierae.