Cercosporoid fungi (Mycosphaerellaceae, Mycosphaerellales, Ascomycota) are one of the largest and most diverse groups of hyphomycetes causing a wide range of diseases of economically important plants as well as of plants in the wild. Although more than 6000 species are known for this group, the documentation of this fungal group is far from complete. Especially in the tropics, the diversity of cercosporoid fungi is poorly known. The present study aims to identify and characterize cercosporoid fungi collected on host plants belonging to Fabaceae in Benin, West Africa. Information on their morphology, host species and DNA sequence data (18S rDNA, 28S rDNA, ITS and tef1) is provided. DNA sequence data were obtained by a simple and non-culture-based method for DNA isolation which has been applied for cercosporoid fungi for the first time in the context of the present study. Among the loci used for the phylogenetic analysis, tef1provided the best resolution together with the multigene dataset. Species delimitation in many cases, however, was only possible by combining molecular sequence data with morphological characteristics. Based on forty specimens recently collected in Benin, 18 species are presented with morphological descriptions, illustrations and sequence data. Among these, six species in the genus Cercospora and two species in Pseudocercospora are proposed as species new to science. The newly described species are Cercospora (C.) beninensis on Crotalaria macrocalyx, C. parakouensis on Desmodium tortuosum, C. rhynchophora on Vigna unguiculata, C. vignae-subterraneae on Vigna subterranea, C. tentaculifera onVigna unguiculata, C. zorniicola on Zornia glochidiata, Pseudocercospora sennicola on Senna occidentalis and Pseudocercospora tabei on Vigna unguiculata. Eight species of cercosporoid fungi are reported for Benin for the first time, three of them, namely C. cf. canscorina, C. cf. fagopyri and C. phaseoli-lunati are new for West Africa. The presence of two species of cercosporoid fungi on Fabaceae previously reported from Benin, namely Nothopassalora personata and Passalora arachidicola, is confirmed.

Samples of leaves infected by cercosporoid fungi were randomly collected in farmlands and fallows in Benin from July–August 2016, July–September 2017 and August–September 2019. Infected leaves were dried in a plant press and deposited in the herbaria Botanische Staatssammlung München (M) and University of Parakou (UNIPAR).

Dried specimens were observed by stereomicroscopy and by light microscopy, using a Zeiss Axioscope 40 microscope. For light microscopy, leaf sections were made with razor blades and mounted in distilled water or 5% KOH without staining. Semi-permanent preparations of sections of the infected leaves were made by a microtome (Leica CM 1510-1) and mounted in lactophenol with cotton blue. Measurements of 30 conidia, conidiophores and other structures have been made for each specimen at a magnification of ×1000. Measurements are presented as mean value ± standard deviation with extreme values in parentheses. Line drawings were made freehand on scaled paper. Images and drawings were edited with Photoshop CS5 (Adobe, San Jose, California). Critical taxa were determined with the help of type specimens and other specimens loaned from the US National Fungus Collections (BPI), the Herbarium of the University of Illinois (ILL) and the New York Botanical Garden (NY).

DNA was isolated from caespituli taken with a needle from dry specimens using the E.Z.N.A® Forensic DNA Extraction Kit following the manufacturer’s instructions. Small pieces of leaves containing several clean caespituli, with as little contaminations as possible, were selected under the stereomicroscope. Four partial nuclear gene regions [three ribosomal loci (SSU, LSU, ITS) and one protein-coding gene (tef1)] were amplified and sequenced.