Phenotypic and genotypic characteristics and host range of Pseudomonas savastanoi strains, the causal agents of olive and oleander

Olive (Olea europaea) as an oily plant and oleander (Nerium oleander) as an ornamental and evergreen shrub are gorwn in Iran. Olive and oleander knot diseases are caused by Pseudomonas savastanoi pv. savastanoi (Psv) and P. savastanoi pv. nerii, respectively. Oleander gall samples were collected from Mazandaran province and olives knots were received from Guilan and Qazvin provinces. Symptoms including swollen lumps with a spongy, irregular appearance were observed on various host tissues, including petioles, branches, twigs, trunks, and leaflets. Fluorescent pigment colonies were appeared on King'S B medium after 48 hours incubation at 28°C. Pathogenicity of 14 and 18 strains among 150 and 180 isolated strains were confirmed on two years old olive and oleander trees, respectively. Moreover, four strains isolated from oleander were able to induce gall on olive trees. All strains were Gram-negative and catalase-positive. Strains were negative for levan production, oxidase, potato rot, and arginine dihydrolase activities and positive in production of hypersensivity reaction on tobacco. The 388 and 349 bp products were amplified in PCR using PsvF/R and PsnF/R primer pairs in Psv and Psn strains, respectively. Phylogenetic analyses based on the sequence of three house-keeping genes including rpoB, rpoD, and gyrB indicated that representative strains grouped with P. savastanoi pathovars.