Determination of Phenotypic Properties and Genetic Diversity of Pseudomonas syringae pv. syringae Strains Causing Bacterial Canker in Stone Fruits in Razavi and Northern Khorasan Provinces.

Pseudomonas syringae pv. syringae (Pss) is the causative agent one of the bacterial common diseases in stone fruit trees fields. In this research, samples were collected from various areas in Razavi and Northern Khorasan provinces during 2011-2012. A total of 23 bacterial isolates were compared based on their phenotypic (physiological and biochemical) characteristics and pathogenicity tests. Pss strains showed slight differences in phenotypic properties. All 23 strains were highly pathogenic on almond and peach seedlings. All strains appeared to be similar in pathogenicity traits. Identification of the strains was further confirmed by PCR using D21/D22 primers specific to P. syringae. Genetic diversity of selected strains was investigated by repetitive element palindromic PCR (rep-PCR) fingerprinting using BOXA1R, ERIC1R, ERIC2 primers and Insertion Sequence PCR (IS-PCR) fingerprinting using IS50 primers. The cluster analyses of the fingerprint data showed that in BOX-PCR with BOXA1R primer, 7 groups were developed at a similarity level of 75%. The same number of groups were obtained in ERIC-PCR using ERIC1R primer at a similarity level of 65%. In case of ERIC2 primer, at a similarity level of 56%, strains were divided into 8 groups, whereas, in IS-PCR with IS50 primer at a similarity level of 52%, strains were divided into 11 groups and finally by combining all four primers at a similarity level of 54%, strains can be distinguished into 7 groups. The results demonstrated the existence of a considerable genetic diversity among Pss strains causing bacterial canker in stone fruit trees in the studied provinces.