Occurrence of Alfalfa Bacterial Stem Blight Disease in Kurdistan Province, Iran

During spring and summer of 2004 and 2005, a new disease of alfalfa was observed for the first time in some areas of the Kurdistan province in Iran. Symptoms were initially yellowed area on leaves, within which water‐soaked, irregular spots developed. These spots eventually coalesced to produce large necrotic areas. Symptoms on petiole and stem include water‐soaked lesions, which later turned brown. Gram negative and rod‐shaped bacteria were isolated from infected tissues. From the results of LOPAT tests (levan production, oxidase reaction, potato soft rot, arginine dihydrolase and tobacco hypersensitivity) and other phenotypic, biochemical and physiological properties investigated, the causal bacterium have been identified as Pseudomonas syringae pv. syringae. Pathogenicity of selected strains was confirmed by injecting a bacterial suspension into leaf tissue from the underside of leaves.