Roussoellaceae J. K. Liu, Phookamsak, D. Q. Dai & K. D. Hyde 2014, fam. nov.

MycoBank MB 804651

Type genus. Roussoella Sacc.

Saprobic on decaying bamboo culms or palm branches. Ascostromata semi-immersed or immersed, forming under darkened, slightly raised, somewhat linear or dome-shaped areas, with a flush intra-epidermal papilla, solitary or gregarious; in vertical section subglobose with a flattened base, with a clypeus. Peridium comprising several layers of elongate cells with interdispersed brown melanin particles, dark brown at the outside. Hamathecium comprising numerous, hypha-like, septate, straight pseudoparaphyses, narrowing towards the ends, anastoming above the asci and embedded in a gelatinous matrix. Asci 4 to 8-spored, bitunicate, cylindrical to clavate, with a short or long knob-like pedicel, often relatively thin-walled, apically rounded, with or without an ocular chamber. Ascospores overlapping uniseriate or biseriate, fusiform-ellipsoidal, straight, 2-celled, constricted at the septum, brown to dark brown, ornamented and surrounded by a wide mucilaginous sheath. Asexual state is linked to Cytoplea and Melanconiopsis or “Neomelanconium”-like. Conidiomata pycnothyrial, semi-immersed, subglobose, dark-brown to black, multilocular, locules separated by vertical columns of darkly pigmented pseudoparenchyma. Peridium comprising several layers of brown to dark brown cells of textura angularis. Conidiophores reduced to conidiogenous cells, annellidic to holoblastic, discrete, hyaline, cylindrical to ellipsoidal, smooth, formed from cells lining the innermost later of the pycnidium. Conidia globose, oblong or ellipsoidal, base truncate, narrower towards the apex, aseptate or septate, often biguttulate, hyaline, brown or black, thick-walled, smooth-walled, minutely warty, sometimes surrounded by an entire gelatinous material.

Notes: Roussoellaceae includes three genera, namely Neoroussoella, Roussoella and Roussoellopsis. This family is characterized as having semi-immersed to immersed, solitary or gregarious, clypeate ascostromata containing trabeculate pseudoparaphyses embedded in a gel matrix, long cylindrical to clavate bitunicate asci with or without obvious fissitunicate dehiscence and brown, 2-celled ornamented ascospores.All the strains of Roussoellaceae formed a well-supported (100% BS/1.00 PP) clade within the order Pleosporales. The phylogenetic relationship between three genera of Roussoellaceae is still not completely resolved and an extensive taxon sampling is required to address the diversity in this family.