A Bacterial leaf blight disease of Christ,s thorn plants (Paliurus spina-christi) in Iran, Kurdistan province, is described for the first time. Water-soaked, irregular spots ranging 5-8 mm in diameter which eventually turn brown with yellow halo on leaves were the main symptoms of the disease. Due to it is relatively recent detection in Iran, very little is known about the pathogen. Yellow, non-mucoid bacterial were consistently isolated from lesions. 15 Fifteen isolates studied were gram negative, catalase positive and oxidase negative. Other phenotypic tests revealed properties indicated that the15 isolates showed more than 90% similarity. Comparative 16s 16S rDNA gene sequence analysis positioned the strains in the genus sphingomonas with the highest sequence similarity to S. melonis (97%). Chemotaxonomically, fatty acid methyl ester analysis revealed that strains contained C16:0 (9%), C18:1 ώ9 (51%) as predominant fatty acids and C14:0 2OH (25%) as a major 2-hydroxy fatty acid, confirming of strains belonging to the genus Sphingomonas, with highest similarity to S. melonis (99%).
