Genotypic and Phenotypic Diversity of the Casual agent of Bacterial Blight of Walnut in Fars and Lorestan Provinces

During 2010 and 2011, 24 Xanthomonas strains were isolated from infected walnut trees from different regions of Fars and Lorestan provinces. For investigation of phenotypic and genotypic features, physiological, biochemical tests and rep-PCR with BOX, ERIC and REP primers. Isolates were rod-shaped, motile with polar flagella, gram negative, obligate parasite, oxidative negative, catalase positive and hydrolyzed esculin. All isolates produced H2S from cystein and acid from glucose, sucrose, D-mannose and D-sorbitol. Isolates showed differences in some characteristics such as tween 80 hydrolysis, starch hydrolysis, tolerance to 3% Nacl and utilization of L-alanin. Also pathogenicity tests and antibiogram were carried out. Based on phenotypic features, pathogenicity tests and amplification of 413 bp fragment with rev_seq R and rev_seq f primers in PCR assay, the isolates were identified as Xanthomonas arboricola pv. juglandis. Based on numerical analysis of phenotypic features most of the isolates were homogeneous and had about 87% similarity. The isolates divided into two groups on the basis of rep-PCR with BOX, ERIC and REP primers. Rep-PCR with above mentioned primers did not confirm clustering of theses isolates based on geographic origin. This is the first report of bacterial blight disease of walnut in Fars province of Iran.