Occurrence of Cercospora leaf spot disease on Cucumis melo in Guilan province and characterization of the casual agent(s) using molecular and morphological approaches

Melon (Cucumis melo) which belongs to the family Cucurbitaceae, is one of most important plants, cultivated in different regions of Iran. In a field survey in Guilan province, the widespread distribution of leaf spot symptoms on melon was observed. In order to identify the fungal agents associated with this disease, symptomatic leaves were collected from the field and taken to the laboratory. Single spore cultures derived directly from leaf spots. In total, 45 isolates were obtained of which 16 were identified based on sequences of five genomic loci (ITS, ACT, tef1, cmdA and his3), host plants, and morphological data. The results of five-gene phylogenetic analysis have revealed that, of the 16 isolates, four isolates were identified as Cercospora sp. G and the remaining 12 isolates nested within Cercospora cf. flagellaris. To our knowledge, this is the first report of the Cercospora sp. G and Cercospora cf. flagellaris on Cucumis melo in the world. Moreover, it is the first report of Cercospora leaf spot (CLS) on Cucumis melo in Iran.