Identification and Discrimination of Pseudomonas syringaeIsolates from Wild Cherry in England

A survey of wild cherry (Prunus avium) woodland plantations and nurseries was carried out in 2000/01. Trees with symptoms of bacterial canker were found in 20 of the 24 plantations visited and in three of seven nurseries. Fifty-four Pseudomonas syringaeisolates from wild cherry together with 22 representative isolates from sweet cherry and 13 isolates from other Prunusspp., pear and lilac were characterised by physiological, biochemical, serological and pathogenicity tests. Isolates from wild cherry were predominantly P. syringaepv. syringae(Pss), but P. syringaepv. morsprunorum(Psm) races 1 and 2 were also found. Physiological and biochemical tests discriminated Psmraces 1 and 2 from other P. syringaeisolates. Agglutination and indirect-enzyme-linked immunosorbent assay tests with three different antisera showed that Psmrace 1 and race 2 were very uniform and indicated high variability amongst other P. syringaeisolates. However, pathogenic Pssisolates could not be distinguished from non-pathogenic isolates of P. syringaeon the basis of physiological, biochemical or serological tests. Pathogenicity tests on rooted lilac plants and on micropropagated plantlets of lilac and two wild cherry clones differentiated Pssand Psmisolates and demonstrated a range of aggressiveness amongst Pssisolates. Serological tests could be used as an alternative to the classical physiological and biochemical tests to increase the speed of detection and discrimination of isolates, but pathogenicity tests are still necessary to discriminate the pathogenic Pssisolates.