A Multiplex PCR Assay for Detection of Pseudomonas syringae pv. actinidiae and Differentiation of Populations with Different Geographic Origin

Abstract Pseudomonas syringaepv. actinidiaeis responsible for severe outbreaks of bacterial cankerof kiwifruit currently occurring around the world. Although molecular detection methods have been reported, none provide complete selectivity for this pathovaror discriminate among pathogen haplotypes. Therefore, a new multiplex polymerase chain reaction(PCR) assay was developed and validated. The assay was tested on 32 P. syringae pv. actinidiaeisolates and 15 non-P. syringae pv. actinidiaestrains and correctly assigned P. syringae pv. actinidiaestrains to three different haplotypes: a Japanese/Korean group, a European group, and a Chinese group. Two P. syringae pv. actinidiaeisolates from New Zealand were found to belong to the Chinese group whereas two other isolates from New Zealand, which were isolated from kiwifruit plants but which do not cause bacterial canker, tested negative. The described PCR assays has a limit of detection of approximately 5 to 50 pg of purified DNA or of 5 × 102 bacteria...