Submitted to: Plant Disease
Publication Type: Research Notes
Publication Acceptance Date: 7/20/2001
Publication Date: 11/20/2001
Citation: Cintas, N.A., Bull, C.T., Koike, S.K., Bouzar, H. A new bacterial leaf spot disease of broccolini, caused by Pseudomonas syringae pathovar maculicola, in California. 2001. Plant Disease 85:1207. Interpretive Summary: N/A
Technical Abstract: In 1998 a new disease was detected on commercial broccolini (Brassica oleracea L. subsp. Botrytis X B. alboglabra) transplants grown in the Salinas Valley, Monterey County, CA. Initial symptoms were small (2-4 mm diameter), circular to angular, watersoaked spots. As disease progressed, spots remained relatively small, but turned tan to brown in color. When diseased tissues were macerated and streaked onto King's medium B, a blue green fluorescent pseudomonad was consistently isolated. Strains were levan positive, oxidase negative, and arginine dihydrolase negative. Strains did not rot potato slices but induced a hypersensitive reaction on tobacco (Nicotiana tabacum L. cv., Turk). Fatty acid methyl ester analysis (MIS-TSBA version 4.10, MIDI Inc., Newark, DE) indicated that strains had a high similarity index (0.82 or higher) to P. syringae, and Biolog GN (Version 3.50, Biolog Inc., Hayward, CA) profiles also identified strains as P. syringae. The bacterium associated with the disease was therefore identified as P. syringae van Hall. Pathogenicity was demonstrated by growing inoculum in nutrient broth shake cultures for 48 hr and misting the broth cultures (10 e 6 cfu/ml) onto broccolini (cv. Aspabrock). Control plants were misted with sterile nutrient broth. After 4 to 5 days in a greenhouse, leaf spot symptoms developed on all inoculated broccolini plants, and reisolated strains were characterized and found to be P. syringae. These tests suggest that the broccolini pathogen is the bacterial leaf spot pathogen, P. syringae pv. maculicola, that occurs on broccoli and cauliflower (B. oleracea L. subsp. botrytis) transplants. This is the first report of this pathogen causing a disease on commercially grown broccolini.