Identification of Pseudomonas Species from a Variety of Hosts in the Salinas Valley of California

Abstract

Bacterial diseases have occurred on crucifers in the Salinas Valley since 1999, particularly on arugula (Eruca vesicaria ssp. sativa), kale (Brassica oleracea var. acephala) and Brussels sprouts (Brassica oleracea var. gemmifera). Also, bacterial diseases have occurred on members of the Chenopodiaceae namely Swiss chard and table beet (both Beta vulgaris ssp. vulgaris). Isolates from arugula, Brussels sprouts, kale, table beet, and Swiss chard were Gram negative, and positive for levan production and the hypersensitive response on tobacco. Furthermore, they were negative for oxidase production, potato rot, and arginine dehydrolyase activity. The arugula, Brussels sprouts, and kale isolates were fluorescent on KMB, but the table beet, and Swiss chard isolates were not fluorescent. The pathotype strain of Pseudomonas syringae pv. aptata was not fluorescent in our laboratory. Isolates from all hosts were consistently identified as strains of P. syringae by fatty acid analysis. Strains of P. syringae from all hosts have been evaluated by BOX-PCR and banding patterns were compared to several pathotypes of P. syringae. BOX-PCR analysis indicated that the pathogen from Swiss chard and table beet were identical to P. s. pv. aptata. The isolates from arugula were similar to P. s.pv. alisalensis and the strains from Brussels sprouts and kale were very similar to P. s. pv. maculicola. Complete phenotypic and host range testing needs to be conducted to conclusively identify these strains.