Species concepts in Cercospora: spotting the weeds among the roses

Abstract

The genus Cercospora contains numerous important plant pathogenic fungi from a diverse range of hosts. Most species of Cercospora are known only from their morphological characters in vivo. Although the genus contains more than 5 000 names, very few cultures and associated DNA sequence data are available. In this study, 360 Cercospora isolates, obtained from 161 host species, 49 host families and 39 countries, were used to compile a molecular phylogeny. Partial sequences were derived from the internal transcribed spacer regions and intervening 5.8S nrRNA, actin, calmodulin, histone H3 and translation elongation factor 1-alpha genes. The resulting phylogenetic clades were evaluated for application of existing species names and five novel species are introduced. Eleven species are epi-, lecto- or neotypified in this study. Although existing species names were available for several clades, it was not always possible to apply North American or European names to African or Asian strains and vice versa. Some species were found to be limited to a specific host genus, whereas others were isolated from a wide host range. No single locus was found to be the ideal DNA barcode gene for the genus, and species identification needs to be based on a combination of gene loci and morphological characters. Additional primers were developed to supplement those previously published for amplification of the loci used in this study.Taxonomic novelties:New species - Cercospora coniogrammes Crous & R.G. Shivas, Cercospora delaireae C. Nakash., Crous, U. Braun & H.D. Shin, Cercospora euphorbiae-sieboldianae C. Nakash., Crous, U. Braun & H.D. Shin, Cercospora pileicola C. Nakash., Crous, U. Braun & H.D. Shin, Cercospora vignigena C. Nakash., Crous, U. Braun & H.D. Shin. Typifications: epitypifications - Cercospora alchemillicola U. Braun & C.F. Hill, Cercospora althaeina Sacc., Cercospora armoraciae Sacc., Cercospora corchori Sawada, Cercospora mercurialis Pass., Cercospora olivascens Sacc., Cercospora violae Sacc.; neotypifications - Cercospora fagopyri N. Nakata & S. Takim., Cercospora sojina Hara.

The rise of Ramularia from the Mycosphaerella labyrinth

“…Groenewald et al, 2013and Bakhshi et al, 2015. Several studies in recent years have highlighted the need to use additional phylogenetic markers to achieve accurate species identification (e.g.…”

Novel species of Cercospora and Pseudocercospora (Capnodiales, Mycosphaerellaceae) from Australia

“…One interpretation of the apparent close relationship between Australian species of Pseudocercospora, on diverse and unrelated native plant species, is that these fungi diverged as opportunistic pathogens from a recent common ancestor. Groenewald et al (2013) discussed this possibility as an explanation for the rapid radiation of Cercospora, which was enabled by the production of cercosporin.…”

Three new records of plant parasitic phyllosphere fungi from Panama: Annellophora phoenicis, Cercospora corniculatae, and Sclerotium coffeicola

“…(Crous and Braun 2003). Even in multigene studies, several species complexes could not be resolved, but some species appeared to be quite host specific, whereas others have broad host ranges among different plant families (Groenewald et al 2013). The species identified here as C. corniculatae/C.…”

“…was studied by Braun (2000), who indicated the synonymy with C. corniculatae and suggested a close relationship or identity with C. apii. Species delimitation in the Cercospora apii species complex (Crous and Braun 2003) is still under progress (Groenewald et al 2013). Known distribution (Fig.…”