Identification of Cercospora spp. associated with emerging Cercospora leaf spot disease of Phaseolus vulgaris L. in Guilan province based on Multigene phylogeny

The Common Bean (Phaseolus vulgaris L.) is one of most important plants, which cultivated in different regions of Iran. In a survey of Common Bean fields in the Astara, Talesh, Fuman, Sowme'eh Sara, Lahijan and Kiashahr regions of Guilan province, the widespread distribution of leaf spot symptoms on this crop were observed. In order to identify the fungal agents associated with this disease, symptomatic leaves were collected in the field and taken to the laboratory. Single spore isolates derived directly from leaf spots and genomic DNA of the isolates was extracted. Isolates were identified based on sequence data of six genomic loci (ITS, actA, tef1, cmdA, his3 and, gapdh), host, and morphological data. Of the 21 isolates obtained in this study, eight isolates were identified as Cercospora sp. G and the remaining 13 isolates nested within Cercospora cf. flagellaris species complex. In addition, the fungal species also detected simultaneously on a plant and even a leaf spot. This is the first report of the Cercospora sp. G and Cercospora cf. flagellaris on Phaseolus vulgaris in the world. Considering that this research is the first report of the widespread distribution of Cercospora leaf spot (CLS) disease of Common Bean in north of the country and the Cercospora species associated with this disease were different from the common Cercospora spp. associated with Cercospora leaf spot of P. vulgaris in other parts of the world, the disease can be considered as an new emerging disease.

Key words: Cercosporoid fungi, phylogeny, species complex.