Pseudomonas syringae pv. syringae causes bacterial canker on Japanese quince (Chaenomeles japonica)

Japanese quince trees are grown as ornamental plants in Iran, in parks and in orchards close to stone fruit and pome fruit trees. Shoots of Japanese quince (Chaenomeles japonica) showing sunken brown canker symptoms were observed and collected near Sari, the center of Mazandaran province in the North of Iran, during the 2016 growing season. Gram negative bacteria isolated from symptomatic tissues were similar to Pseudomonas syringae pv. syringae (Pss) were pathogenic on Japanese quince and on quince (Cydonia oblonga) seedlings after artificial inoculation, and were re-isolated from diseased hosts. Phylogenetic tree construction using partial sequences of ITS and rpoD genes showed that the Japanese quince isolates were in the same clade as Pss strains. The isolates had ice nucleation activity, and the InaK gene was amplified successfully. According to the results of phenotypic and genotypic characteristics, genomic DNA fingerprinting using REP-PCR, BOX-PCR and IS50-PCR and isolation of total cell proteins, we conclude that Pss is the causal agent of canker of the Japanese quince trees. Therefore, Japanese quince is a new host for Pss causing bacterial canker on many different host plants.