Amphisphaeria planibasalis M. C. Samar. sp. nov.

Fig. 3

Etymology.

The specific epithet “ planibasalis ” refers to the flat base of the ascomata.

Holotype.

MFLU 26-0119.

Description.

Saprobic on an unidentified dicotyledonous dead branch. Sexual morph: Ascomata 345–450 × 120–235 μm (x ̄ = 416 × 183 μm, n = 7), immersed, visible as raised, black dots, solitary, rarely aggregated (two ascomata), scattered, in cross-section, conical with mostly flattened base. Ostioles centric, prominent, conical, ostiolar canal short and periphysate, 1.1–1.8 μm (x ̄ = 1.4 μm, n = 15). Peridium 6.5–10 μm (x ̄ = 8.5 μm, n = 10) wide, wider at the corners up to 18 μm, multi-layered, outer layer tightly attached to host tissue, comprising reddish brown, thick-walled cells of textura angularis, inner layer composed of hyaline, thin-walled cells of textura angularis. Paraphyses 2.7–5.3 μm (x ̄ = 3.6 μm, n = 20) wide, longer than asci, cellular, septate, branched, guttulate, embedded in a gelatinous matrix. Asci 110–145 × 8.5–14 μm (x ̄ = 127 × 11.2 μm, n = 20), eight-spored, unitunicate, cylindrical, with a 3–4 × 0.6–1.1 μm (x ̄ = 3.5 × 0.9 μm, n = 10), discoid, apical ring, J + in Melzer’s reagent, apically rounded. Ascospores 13.5–19.5 × 5–7.5 μm (x ̄ = 16.2 × 5.8 μm, n = 35), L / W 2.8, uniseriate, hyaline when young, light to dark brown when mature, ellipsoid, one-septate, constricted at septum, prominent bi-guttulate when immature, smooth-walled, thin mucilaginous sheath 0.7–2 μm (x ̄ = 1.4 μm, n = 20). Asexual morph: Undetermined.

Material examined.

Thailand • Lamphun Province, Mueang District, on an unidentified dead dicotyledonous branch attached to the host, 22 October 2022, MC. Samarakoon, MC 22-014 (Holotype MFLU 26-0119; Isotype CMUB 40143).

Additional sequence.

PX 513824 (tef 1 - α; MFLU 26-0119).

Notes.

In the combined ITS – LSU – rpb 2 – tub 2 phylogeny, collection MC 22-014 formed a distinct branch. The ITS sequence of MC 22-014 is similar to that of A. umbrina (PRA - JV 24328; 90 %, 17 / 596 gaps), A. flava (MFLU 18-0102; 90 %, 17 / 598 gaps), A. ailaoshanensis (KUNCC 23-15520; 90 %, 24 / 575 gaps), and A. fuckelii (CBS 140409; 89 %, 12 / 595 gaps), while the LSU is similar to that of A. hydei (CMUB 40016; 98 %, 1 / 896 gap), A. guttulata (MFLU 22-0078; 98 %, 2 / 892 gaps), A. mesuae (MFLU 25-0069; 97.9 %, 4 / 900 gaps), and A. thailandica (MFLU 18-0794; 97 %, 1 / 906 gap). The rpb 2 sequence shows similarity to A. fuckelii (CBS 140409; 86 %, 0 / 1055 gap), A. qujingensis (KUMCC 19-0187; 86 %, 0 / 1049 gap), and A. thailandica (MFLU 18-0794; 85 %, 5 / 781 gaps). Collection MC 22-014 is similar to other taxa by having immersed ascomata, ellipsoid ascospores, and a J + apical ring in Melzer’s reagent (the apical ring of A. hibiscicola is not described) (Sun et al. 2025). Amphisphaeria flava and A. umbrina differ from MC 22-014 by the presence of a yellow halo on the substrate around the neck area and a clypeus, respectively. Amphisphaeria conica (current name A. umbrina) was originally introduced as Sphaeropsis conica as the generic type, highlighting the conical shape of the ascomata and the flat base. The ascospores of A. flava possess a sheath similar to that of MC 22-014. However, the prominent conical ascomata of MC 22-014 differ from the globose to subglobose ascomata found in the other species. ‘ Lepteutypa hexagonalis, ’ which lacks molecular data, resembles MC 22-014 in having immersed, conical-pyramidal ascomata with a flattened base that are triangular, occurring singly or in pairs, and possessing a J +, discoid apical ring (Goh and Hyde 1997). However, it differs in having larger ascomata (700–800 × 600–700 µm) and fusiform, three-septate ascospores with 6–7 longitudinal ridges (Goh and Hyde 1997). Based on morphology and phylogeny, collection MC 22-014 is identified as a new species, A. planibasalis.