Polyphasic taxonomy of four passalora-like taxa occurring on fruit and forest trees

Abstract

Species of Passalora s. lat. are eminent phytopathogenic fungi that cause generally leaf spot diseases on a broad variety of plants throughout the world. During our investigations exploring cercosporoid fungi associated with leaf spot symptoms of fruit and forest trees in northern and north-western Iran, several passalora-like infections were isolated from symptomatic leaves of different trees belonging to the Fabaceae, Malvaceae, Rosaceae and Ulmaceae. A polyphasic taxonomic approach by applying molecular data, morphological features and host data, was employed to identify the isolates. In a multigene phylogenetic analysis (LSU, ITS and RPB2), these isolates clustered in four clades in the Mycosphaerellaceae. The revealed taxa encompass Paracercosporidium microsorum on Tilia platyphyllos, Prathigadoides gleditsiae-caspicae gen. et. sp. nov. on Gleditsia caspica, Pruniphilomyces circumscissus on Prunus avium and Prunus cerasus, and Sirosporium celtidis on Celtis australis. The new genus Prathigadoides and its type species Prathigadoides gleditsiae-caspicae are molecularly distinct from all phylogenetically related genera, and some characteristics of the conidiophores and conidia differs from those of the morphologically similar species Prathigada condensata on the North America Gleditsia triacanthos.