Review of Pseudomonas species causing bacterial canker of Prunus species with emphasis on sweet cherry ( Prunus avium ) in New Zealand

Bacterial canker of cherry is a major constraint to stone fruit production worldwide, including New Zealand. Six pathovars of the bacterium Pseudomonas syringae are known to cause bacterial canker on Prunus species. From those six pathovars, P . s . pv. syringae (Pss), P . s . pv. morsprunorum race 1 (Psm1) and P . s . pv. persicae have been reported as pathogens of Prunus species in New Zealand, and Pss and Psm1 on sweet cherry ( Pr. avium ). On sweet cherry, extensive development of cankers and gummosis is usually observed, particularly during late winter and spring, with the progressive decline of trees resulting from the death of branches or death of the plant. In young orchards in New Zealand, losses of 20–50%, and sometimes the removal of entire cherry blocks have been observed. This review reports on the current knowledge of P. syringae pathovars causing bacterial canker of Prunus species, with specific focus on sweet cherry in New Zealand, and covers their identification, the infection process, virulence associated factors, epidemiology, symptoms, and management strategies.