In 2012, a leaf spot disease on walnut seed-lings was observed in Hamedan province of Iran. The spots were necrotic with yellow halos. Symptomatic samples were collected and suspected bacterial agent was isolated on nutrient agar medium. Phenotypic char-acteristics such as production of fluorescent pigment on KB medium, LOPAT test and utilization of various car-bon sources, revealed that the strains werePseudomonas syringaepv.syringae. All tested strains were pathogenic on peach, plum and walnut seedling. To investigate the genetic diversity among the strains, rep-PCR using BOX and ERIC primers was performed. Results showed high similarity among the strains from the same region, while variation was found among those from different areas and they were divided into two groups based on geo-graphic regions. The phylogenetic analysis based on 16S rRNA,rpoDandgyrBsequences showed that represen-tative isolates were closely related to P. syringaepv. syringae. To the best of our knowledge, this is the first report of the presence of P. syringaepv.syringaeas a causal agent of walnut seedlings leaf spot in Iran and worldwide.
