Uwebraunomyces, a novel genus of the family Mycosphaerellaceae

Abstract

A hyaline to pale olivaceous brown hyphomycetous fungus was collected on living leaves of Tinospora cordifolia in India. Molecular phylogenetic analyses of several loci (LSU-RPB2-ITS) indicated a relationship with cercosporoid fungi (Mycosphaerellaceae). As no other known lineage shares similar morphology or DNA sequences, a new genus, Uwebraunomyces, is proposed, with U. tinosporae comb. nov. based on Ramularia tinosporae as the type species. Conidiophores are pale olivaceous to very pale brown in colour, typically unbranched, and subcylindrical to geniculate-sinuous at the tip. Conidia are solitary, obclavate to obpyriform, straight to curved, and few-septate. Additionally, the conidiogenous loci are characterized by a centrally located small papilla and a minute, distinct frill that is typically evident in older scars. These characteristics distinguish Uwebraunomyces from other closely related members of the ramularioid complex. Additionally, Cercosporella bundelkhandae is recognized as a new synonym as it shares nearly identical morphological features with U. tinosporae. At the ultrastructural level, Uwebraunomyces is further characterized by conidiogenous loci that bulge outward, forming convex or truncated cone shapes, with wall thickening extending beyond the area originally occupied by the base of the conidium. Older scars display a minute papilla or small, somewhat conical protuberant like structure in the centre of their apical depression, often accompanied by a minute, distinct frill. The conidial base is obconically truncate, featuring a basal depression with a centrally located, slightly protuberant structure. These distinct ultrastructural features set Uwebraunomyces apart from other members of the ramularioid complex, underscoring its taxonomic significance within the Mycosphaerellaceae. © 2025 Westerdijk Fungal Biodiversity Institute.