Characterisation of Pseudomonas syringae pathogenicity on various species of fruit trees

Abstract: Pseudomonas syringae is an important pathogen on a wide range of hosts, including pome fruits. Bacterial canker of fruit trees is caused by two P. syringae pathovars with a different host range. P. syringae pv. syringae has a wide host range, including pome fruits, while cherries and plums are predominantly infected by P. syringae pv. morsprunorum. Twenty-four isolates of P. syringae originating from various diseased hosts, including apple and pear, were selected to characterise their pathogenicity on different fruit tree species and related hosts. These isolates were identified as P. syringae using biochemical and phenotypic characterisation by LOPAT and GATTa tests for determination of species and pathovars, respectively. Also, 16S sequencing was performed to confirm their identity. The pathogenicity of the isolates was tested by inoculation of bacteria on immature fruitlets of 14 hosts and potted plants of four hosts, including apples and pears. The tested isolates varied strongly in their pathogenicity depending on the inoculated host species. Several isolates showed strong aggressiveness to more than one host species.