Identification of Fungal Species Associated with Leaf Spot Disease on Poplar Trees (Populus spp.) in East Azarbaijan Province and Some Parts of west Azarbaijan and Ardabil provinces

Leaf spot diseases are among the important foliar diseases of poplar trees, causing economic crop loss on this host. Species in the genera Septoria and Marssonina are the main fungal groups causing leaf spot disease on poplar trees, worldwide. Even though leaf spot diseases cause considerable damage on poplar trees in East Azarbaijan province, very little attention has been paid on the identification of the causal agents of disease in this region. The present study was aimed to characterize the causal agents of leaf spot diseases on poplar trees in East Azarbaijan, part of West Azarbaijan and Ardabil provinces and to further evaluate their pathogenicity on poplar trees. A total number of 134 fungal isolates were recovered from 220 samples with leaf spot symptoms on poplar trees during 2013 growing season. Morphological and cultural characterization of isolates revealed Septoria populi, Bipolaris spicifera, B. sorokiniana, Exserohilum cf. protrudens, Stemphylium sp. Sporormiella minimoides, Nigrospora oryzae, Epicoccum nigrum, Marssonina castagnei and Arthrinium sacchari as fungal species associated with leaf spot disease of poplar. Septoria populi was the most dominant species with isolation frequency of 88%. The pathogenicity assay using detached leaf method revealed Se. populi, B. spicifera, B. sorokiniana, Stemphylium sp., N. oryzae, M. castagnei and A. sacchari being pathogenic on poplar leaves under laboratory conditions. This is the first report on the occurrence and pathogenicity of A. sacchari, Sp. minimoides and Ex. cf. protrudens on poplars trees.