Tomato Bacterial Speck and Leaf Blight in Iran Caused by Two Members of the Pseudomonas syringae Complex

ABSTRACT Seed‐borne bacterial diseases caused by taxonomically diverse pathogens are economically important constraints threatening the tomato ( Solanum lycopersicum ) industry in both open‐field and greenhouse productions globally. While Xanthomonas euvesicatoria and Clavibacter michiganensis causing bacterial spot and bacterial canker diseases, respectively, are prevalent bacterial diseases of tomato, pathogenic members of the Pseudomonas syringae species complex occasionally play an important role in tomato health and productivity. Within the past few years, nationwide comprehensive field surveys and samplings were conducted in tomato‐producing areas in Iran to monitor the status of bacterial diseases of the crop in the country. Besides plenty of Xanthomonas and Clavibacter spp., nine gram‐negative, cream‐coloured bacterial strains were isolated from symptomatic tomato plants showing leaf speck and pith necrosis. The latter strains were identified as members of the P. syringae species complex based on phenotypic features, for example, colony morphology, pigmentation and LOPAT scheme. Precise phylogenetic position and taxonomic status of the strains were determined using the phylogeny of gyrB and rpoD gene sequences. Accordingly, three strains were identified as Pseudomonas viridiflava , while six strains were clustered in a monophyletic clade next to the pathotype strains of P. syringae pv. maculicola and P. syringae pv. apii within the phylogroup 01a of P. syringae sensu lato. All strains induced symptoms on tomato plants under greenhouse conditions resembling those observed in the field. Results of the present study highlight the probability of establishing P. syringae infection on tomato crops in Iran despite being less prevalent under natural conditions.