Submitted to: Journal of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2011
Publication Date: 7/1/2011
Citation: Bull, C.T., Clarke, C.R., Cai, R., Vinatzer, B.A., Jardini, T.M., Koike, S.T. 2011. Multilocus sequence typing of Pseudomonas syringae sensu lato confirms previously described genomospecies and permits rapid identification. Journal of Phytopathology. DOI: 10.1094/PHYTO-11-10-0318. Interpretive Summary: Bacterial diseases of food crops results in significant crop losses and result in higher prices or lack of product for consumers. The identification of bacterial pathogens from new and emerging plant diseases is the first step to develop methods to prevent and control the diseases. In this manuscript we provide the resources for rapid identification of an important group of bacterial plant pathogens (Pseudomonas syringae) causing economically important diseases on a wide range of crops. This will speed identification of all pathogens in this group and speed the development of detection and strategies for preventing the spread of new diseases.
Technical Abstract: Since 2002, severe leaf spotting on parsley (Petroselinum crispum L.) has occurred in Monterey County, California. One of two different pathovars of Pseudomonas syringae sensu lato were isolated from diseased leaves from seven distinct outbreaks and twice from the same outbreak (2002 and 2009). Fragment analysis of DNA amplified between repetitive sequences (rep-PCR), 16S rDNA sequence analysis, biochemical and physiological tests identified the pathogens as Pseudomonas syringae pv. apii and P. syringae pv. corriandricola. Koch’s postulates and host range tests demonstrated that Pseudomonas syringae pv. apii and P. syringae pv. corriandricola cause leaf spot diseases on parsley, celery and coriander. A phylogenetic tree was built based on the concatenated sequences of the four housekeeping gene fragments gap1, gltA, rpoD, and gyrB for one hundred and eighty-nine strains of Pseudomonas syringae including over 40 pathotype strains and sequences were uploaded to the Plant-Associated Microbes Database (PAMDB). The topology of the phylogenetic tree generated by MLSA directly corresponded to P. syringae genomospecies and P. syringae pv. apii was allocated appropriately to genomospecies 3. This is the first demonstration that MLSA can accurately allocate members new pathogens directly to Pseudomonas syringae sensu lato genomospecies. According to the MLSA P. syringae pv. coriandricola is a member of genomospecies 9, P. cannabina. In a blind test both P. syringae pv. coriandricola and P. syringae pv. apii isolates from parsley were correctly identified to the pathovar. In both cases MLSA described diversity within each pathovar that was previously unknown.