During the years 2001 to 2004, samples of mulberry leaves were collected from different mulberry orchads in Guilan province to identify the causal agent(s) of mulberry leaf blight. Symptoms of diseased plants consisted of formation of irregular necrotic lesions on leaves surrounded by yellow chlorotic halo. Under favorable conditions, these lesions gradually expanded and leaves became blighted. In attempts to investigate the causal agent, two types of gram-negative bacteria with raised fluorescent colonies on King’s B medium were isolated. Based on morphological, physiological, biochemical, pathogenicity properties, and total cellular protein profiles (SDS-PAGE), while employing PCR method with specific primers, the predominant pathogenic type was identified as Pseudomonas syringae pv.mori. However, the other type on some mulberry orchads was identified as P.s.pv.syringae.
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