The genus Cercospora includes many important plant pathogenic fungi associated with leaf spot diseases on a wide range of hosts. The mainland of Iran covers various climatic regions with a great biodiversity of vascular plants, and a correspondingly high diversity of cercosporoid fungi. However, most of the cercosporoid species found to date have been identified on the basis of morphological characteristics and there are no cultures that support these identifications. In this study the Consolidated Species Concept was applied to differentiate Cercospora species collected from Iran. A total of 161 Cercospora isolates recovered from 74 host species in northern Iran were studied by molecular phylogenetic analysis. Our results revealed a rich diversity of Cercospora species in northern Iran. Twenty species were identified based on sequence data of five genomic loci (ITS, TEF1-α, actin, calmodulin and histone H3), host, cultural and morphological data. Six novel species, viz. C. convolvulicola, C. conyzae-canadensis, C. cylindracea, C. iranica, C. pseudochenopodii and C. sorghicola, are introduced. The most common taxon was Cercospora cf. flagellaris, which remains an unresolved species complex with a wide host range. New hosts were recorded for previously known Cercospora species, including C. apii, C. armoraciae, C. beticola, C. cf. richardiicola, C. rumicis, Cercospora sp. G and C. zebrina.

The genus Cercospora includes many important plant pathogens that are commonly associated with leaf spot diseases on a wide range of cultivated and wild plant species. Due to the lack of useful morphological features and high levels of intraspecific variation, host plant association has long been a decisive criterion for species delimitation in Cercospora. Because several taxa have broader host ranges, reliance on host data in Cercospora taxonomy has proven problematic. Recent studies have revealed multi-gene DNA sequence data to be highly informative for species identification in Cercospora, especially when used in a concatenated alignment. In spite of this approach, however, several species complexes remained unresolved as no single gene proved informative enough to act as DNA barcoding locus for the genus. Therefore, the aims of the present study were firstly to improve species delimitation in the genus Cercospora by testing additional genes and primers on a broad set of species, and secondly to find the best DNA barcoding gene(s) for species delimitation. Novel primers were developed for tub2 and rpb2 to supplement previously published primers for these loci. To this end, 145 Cercospora isolates from the Iranian mycobiota together with 25 additional reference isolates preserved in the Westerdijk Fungal Biodiversity Institute were subjected to an eight-gene (ITS, tef1, actA, cmdA, his3, tub2, rpb2 and gapdh) analysis. Results from this study provided new insights into DNA barcoding in Cercospora, and revealed gapdh to be a promising gene for species delimitation when supplemented with cmdA, tef1 and tub2. The robust eight-gene phylogeny revealed several novel clades within the existing Cercospora species complexes, such as C. apii, C. armoraciae, C. beticola, C. cf. flagellaris and Cercospora sp. G. The C. apii s. lat. isolates are distributed over three clades, namely C. apii s. str., C. plantaginis and C. uwebrauniana sp. nov. The C. armoraciae s. lat. isolates are distributed over two clades, C. armoraciae s. str. and C. bizzozeriana. The C. beticola s. lat. isolates are distributed over two clades, namely C. beticola s. str. and C. gamsiana, which is newly described.

Species of Pseudocercospora have gained much attention in recent years owing to their phytopathogenic relevance, and worldwide occurrence on a wide range of economically important hosts. Although these fungi are common in Iran, they have generally been poorly studied and no cultures have been preserved for molecular analyses. The present paper represents the first study of Pseudocercospora species from Iran evaluated by employing the Consolidated Species Concept. Nineteen isolates were obtained from seven host plant families in the northern zone of Iran. A phylogenetic analysis based on a combination of LSU, ITS, TEF1-α and ACT loci clustered these isolates into eight clades, of which five are phylogenetically new, delineating two novel species, viz. P. mazandaranensis on Nerium oleander and P. sophoricola on Sophora alopecuroides. Furthermore, P. punicae is recorded on a wild-grown cultivar of Punica granatum, and two additional species reported, namely Pseudocercospora sp. A on Phaseolus vulgaris and Pseudocercospora sp. B on Diospyros lotus. Pseudocercospora norchiensis is recorded for the first time in Asia, where it occurs on a wide host range, contrary to most other species of Pseudocercospora, which appear to be highly host specific.

The genus Colletotrichum comprises a number of plant pathogens of major importance which cause anthracnose diseases on a wide range of woody and herbaceous plants worldwide. With the advent of molecular studies, it has been shown that most of the previously known species e.g. C. boninense, C. acutatum, and C. gloeosporioides have been split into several species. In the present study, the identity of Colletotrichum isolates from the northern and northwestern zone of Iran were determined based on multi-gene phylogenetic analyses. Phylogenetic analysis based on a combination of internal transcribed spacer (ITS), beta tubulin (TUB), histone H3 (HIS), calmodulin (CAL), and actin (ACT) loci, clustered our isolates into three clades, including C. salicis on Salix sp., Colletotrichum sp. (C. fuscum sensu lato) within the C. destructivum species complex on Viola sp., and C. fructicola on Citrus sinensis, Malus domestica, Gleditsia caspica, and Sambucus ebulus. These three species are new for mycobiota of Iran. According to these results, Viola sp. from West Azerbaijan (Khoy-Firouragh) is a new host for Colletotrichum sp. in the C. destructivum species complex. Furthermore, C. sinensis from Mazandaran (Behshahr), and G. caspica, and S. ebulus from Guilan (Talesh), are new host records for C. fructicola.

Cercospora (Mycosphaerellaceae) is a large genus of fungi comprising many important plant pathogens. In recent years DNA-based studies have revealed multiple genera of cercosporoid fungi being poly- and paraphyletic. Among these genera, the genus Cercospora has always been perceived as monophyletic. In the present study, phylogenetic inferences based on partial gene sequences of the LSU, ITS, ACT, TEF1-α and HIS loci, elucidated a cercospora-like taxon from Ammi majus to cluster in a clade apart from Cercospora s. str. In spite of numerous Cercospora spp. presently known from their DNA sequence data, this collection represents the first concrete evidence to the fact that the morphological characters previously attributed to Cercospora s. str. evolved more than once in the Mycosphaerellaceae. The genus Neocercospora is subsequently introduced to accommodate the Iranian taxon occurring on A. majus. Further collections on other hosts and from different continents are now required to establish the prevalence and relative importance of species of Neocercospora.