Prevalent causal agents of apricot bacterial canker disease from Hamedan province

Hamedan province is one of the most important regions for cultivation of stone fruit trees, such as apricots (Prunus armeniaca) due to its suitable climatic conditions. Bacterial canker disease of stone fruit trees caused by Pseudomonas syringae pv. syringae, is one of the most serious diseases in this province, Iran and all over the world. The study was performed to identify the causative agent of the disease.

Samples of diseased apricots were collected in early spring and fall autumn of 2018. From the collected samples a total of 130 bacterial strains were isolated of which 65 representative’s strains were selected based on the color and type of colonies on the culture medium for further study. SDS-PAGE technique was used to group the representative’s strains. Pathogenicity of the representative’s strains were performed on apricot seedlings under greenhouse condition. The studied strains were identified based on their phenotypic features, using standard bacteriological method and followed by sequencing of the 16S rRNA encoding gene.

30 strains showed hypersensitivity reaction on geranium leaves.  According to the pattern of cellular soluble proteins on polyacrylamide gel (SDS-PAGE), the strains were divided into seven groups. BLAST of partial sequence of 16S rRNA encoding gene from this strain showed 98/7% similarity to P. syringae NCPPB 281. Another strain (FB46 strain) was identified as P. agglomerans due to 95.33% similarity with Pantoea agglomerans RSG19 by BLAST of 16S rRNA encoding gene sequence.

The results obtained are in agreement with of Vasebi et al. isolated P. syringae as a causative agent of apricot canker in East Azerbaijan province. P. agglomerans has also been reported as one of the factors associated with stone fruits, pome fruits and walnut trees in Alborz province. This is the first report for the presence of Pseudomonas syringae as a causative agent of apricot canker disease in Hamedan province. The bacterium Pantoea agglomerans is reported from the first time in the world as the causative agent which induce apricot canker symptoms.