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Novel Pseudomonas syringae strains associated with leaf spot diseases on watermelon (Citrullus lanatus) and squash (Cucurbita pepo) in California.
I. RUBIO (1), H. Bouzar (2), T. M. Jardini (3), S. T. Koike (4), C. T. Bull (3). (1) California State University-Monterey Bay, Salinas, CA, U.S.A.; (2) Sakata Seed America, Inc., Salinas, CA, U.S.A.; (3) USDA–ARS, Salinas, CA, U.S.A.; (4) University of California Cooperative Extension, Salinas, CA, U.S.A.

In 2006 and 2011, bacteria, fluorescent on KMB, were isolated from leaf spots on greenhouse-grown watermelon (<i>Citrullus lanatus</i>) and field-grown squash (<i>Cucurbita pepo</i>), in coastal California. Biochemical characterization of the isolates indicated that they belonged to <i>Pseudomonas syringae</i>. 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 gene sequences of the isolates to those in the public database. Gene sequences from the watermelon and squash isolates were similar but different from the gene sequences of <i>P. syringae</i> pv. <i>aceris</i> or <i>P. syringae</i> pv. <i>solidagae</i> and <i>P. syringae</i> pv. <i>papulans</i>, respectively. Additionally, DNA fragment banding patterns for the isolates generated by rep-PCR using the BOXA1R primer were distinct from members of genomospecies 1 and the pathotypes of fluorescent pseudomonads pathogenic on cucurbits. These data indicated that novel <i>P. syringae</i> 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.<p><p>Keywords: Bacteria-Phytoplasma-Spiroplasma-Fastidious Prokaryote, Fruits-Nuts

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