ARS | Publication request: Novel Pseudomonas syringae strains associated with leaf spot diseases on watermelon (Citrullus lanatus) and squash (Cucurbita pepo) in California

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: May 7, 2012
Publication Date: July 1, 2012
Citation: Rubio, I., Bourzar, H., Jardini, T.M., Koike, S.T., Bull, C.T. 2012. Novel Pseudomonas syringae strains associated with leaf spot diseases on watermelon (Citrullus lanatus) and squash (Cucurbita pepo) in California. Phytopathology. 102:S4.103.

Technical Abstract: In 2006 and 2011, bacteria, fluorescent on KMB, were isolated from leaf spots of greenhouse-grown watermelon (Citrullus lanatus) and field-grown squash (Cucurbita pepo) in coastal California. Biochemical characterization of the isolates indicated that they belonged to Pseudomonas syringae. Multilocus sequence typing (MLST) of four housekeeping genes revealed that these isolates were members of genomospecies 1 and were distinct from fluorescent pseudomonads previously identified as cucurbit pathogens. The BLAST tool in the Plant-Associated Microbes Database was used to compare the isolates to those in the public database. The watermelon and squash isolates had similar gene sequences which differed from the gene sequences of P. syringae pv. aceris, P. syringae pv. solidagae and P. syringae pv. papulans. Additionally, DNA fragment banding patterns generated by rep-PCR using the BOXA1R primer for the isolates were distinct from members of genomospecies 1 and the pathotypes of fluorescent pseudomonads pathogenic on cucurbits. These data indicate that novel P. syringae isolates in genomospecies 1 were associated with the foliar diseases on watermelon and squash. Further taxonomic data are needed, including host range evaluations, to determine if these isolates are variants of previously named pathovars or represent new pathovars.