Addition of two new genera—Marcstadlera gen. nov. and Neoclypeosphaerella gen. nov. (Mycosphaerellaceae)—based on polyphasic evidence

During a survey of foliicolous fungi in India, two interesting anamorphic hyphomycetous fungal specimens were collected from infected leaves of <i>Calotropis</i> spp. and <i>Mallotus philippensis</i>. <i>Calotropis</i> spp. produce fascicles of conidiophores from stromata, accompanied by secondary superficial hyphae bearing solitary conidiophores. The specimen on <i>Mallotus philippensis</i> resembled <i>Mycovellosiella</i>, characterized by secondary superficial hyphae bearing micronematous to semi-macronematous, mononematous, unbranched, and aseptate conidiophores. A polyphasic approach-including morphological, cultural, and multilocus phylogenetic analyses (LSU-<i>Rpb2</i>-ITS), coupled with genealogical concordance phylogenetic species recognition-identified its relationship with cercosporoid fungi within the family <i>Mycosphaerellaceae</i>. The analysis confirmed that these fungal specimens represent distinct lineages without known morphological or DNA sequence counterparts. Consequently, two new genera are proposed: <i>Marcstadlera</i> and <i>Neoclypeosphaerella</i>, with <i>M. malloti</i> comb. nov. and <i>N. calotropidis</i> comb. nov. as their respective type species. Additionally, <i>Clypeosphaerella calotropidis</i>, <i>Clypeosphaerella quasiparkii</i>, and <i>Pseudocercospora malloti</i> are recognized as new synonyms. Several genera in the <i>Mycosphaerellaceae</i>, including <i>Marcstadlera</i> and <i>Neoclypeosphaerella</i>, are monophyletic. The ultrastructure of the conidiogenous loci and hila differs between these two genera. In <i>Marcstadlera</i>, the loci are cylindrical or peg-like, truncate at the apex, while the conidial base is narrowly obconically truncate. In <i>Neoclypeosphaerella</i>, the loci are slightly protuberant and surrounded by a circular rim-like structure, forming a truncated apex with a centrally positioned small apical depression. The conidial base is obconically truncated and also surrounded by a circular rim-like structure.