Lijiangomyces Meng & Jayaward. gen. nov.

Etymology.

The genus name “ Lijiangomyces ” refers to “Lijiang”, the city in Yunnan Province of China from where the holotype was collected.

Description.

Sexual morph: Ascomata hysterothecia, superficial, solitary, dispersed, sessile, obovoid to broadly shell-shaped or irregularly rounded, with a broadly open or slit-like disc. Margin black, vertically erect, fragile, with the disc surface appearing yellowish-brown. Peridium carbonaceous, black in the lateral and upper regions. Hymenium hyaline to slightly yellowish, with a densely packed hamathecium. Paraphyses filiform, hyaline, non-anastomosed, and non-septate. Hypothecium slightly yellowish. Asci bitunicate, 8 - spored, elongated to clavate, with a rounded apex lacking ascal wall thickening, I-, K-. Ascospores uniseriate, arranged obliquely and parallelly, hyaline, thin-walled, smooth, fusiform to ellipsoidal, K-, I + dark blue, aseptate at immature, becoming muriform at maturity with 4–7 transverse septa and 1–2 longitudinal septa. Asexual morph: Not observed.

Type species.

Lijiangomyces laojunensis Meng & Jayaward.

Notes.

The genus is distinguished by black, broadly shell-shaped to irregularly rounded hysterothecial ascomata, with a broadly open or occasionally closed disc, typically light brown to flesh-yellow. Asci are elongated to clavate, containing eight uniseriate, hyaline, and muriform ascospores. Phylogenetic analysis places this genus within the family Mytilinidiaceae (Mytilinidiales, Dothideomycetes) closely related to Mytilinidion. In the single-gene phylogenies, the new species is positioned outside the Mytilinidia sensu stricto clade in the ITS and LSU trees but clusters within it in the tef 1 - α tree. However, in the concatenated analysis combining all three genes, it is again placed outside the Mytilinidia sensu stricto clade. These results support its recognition as a distinct lineage within Mytilinidiaceae. Morphologically, this genus differs significantly from Mytilinidion in having obovoid to broadly shell-shaped or irregularly rounded, with broadly open ascomata (vs. globoid to obovoid, conchate, or dolabrate ascomata with narrow slit-like openings) and hyaline and muriform ascospores (vs. hyaline to brown and transverse septa). In addition, this genus shares similar morphology with Ostreola in having muriform ascospores but differs in the broadly shell-shaped or irregularly rounded ascomata (vs. conchiform to hatchet-shaped), a broad disc opening (vs. narrowly slit-like), and hyaline ascospores (vs. brown).