Morphological and molecular identification and pathogenicity of Septoria species involved in leaf spot disease on Populus species in East Azerbaijan, West Azerbaijan and Ardabil provinces*

Species belonging to the genus Populus are widely used for log production, landscape design, and windbreak plantations. Septoria spp. are the most prevalent fungi causing leaf spot on poplars, which is one of the most damaging foliar diseases of these trees. However, identification of species belonging to this genus through morphological analysis is often problematic. The present work aimed to identify Septoria spp. causing leaf spot disease on poplars in East Azarbaijan, West Azerbaijan and Ardabil Provinces by using species specific primers as well as morphological features. Primers have been designed based on nr ITS rDNA sequences of S. populi and S. populicola. For this purpose, during summer 2013 symptomatic leaves were sampled from poplars in these regions, and pure cultures of isolates belonging to the genus Septoria were established. Genomic DNA of the isolates was extracted using CTAB method, and efficacy of the primers in identification of causative agent(s) of the disease was evaluated. With species-specific primer set of S. populicola we failed to obtain specific amplification products (329 bp). Species-specific primer set of S. populi, however, amplified a 439 bp fragment of all Septoria isolates. Hence, the results revealed S. populi as the only causal agent of Septoria leaf spot disease of poplars in these regions. Finally, on the basis of pathogenicity test all chosen strain caused disease on popular leaves.