|Koike, Steve - UCCE, UC, DAVIS|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 2, 2005
Publication Date: February 20, 2006
Citation: Koike, S.T., Bull, C.T. First report of bacterial leaf spot of Italian dandelion (Cichorium intybus) caused by a Pseuduomonas syringae pathovar in California. Plant Disease 90:245, 2006; published on-line as DOI: 10.1094/PD-90-0245A. Interpretive Summary: Italian dandelion (Cichorium intybus) is a leafy, non-head forming chicory plant and is grown in the Salinas Valley (Monterey County) in California. This plant is used in specialty salads and is part of the 300 thousand dollar specialty salad production in the region. In 2002, a previously unreported disease was found in commercial Italian dandelion fields causing symptoms. Large spots on the leaves (10 and 30 mm in length) could be seen on both sides of the leaves and thus they could not be sold. Because fields were irrigated with overhead sprinklers, the disease was severe and large portions of the plantings were not harvested. The pathogen causing the disease was identified and isolated for further study. This is the first step in understanding how the disease is influenced by cropping practices and in developing programs to manage the disease to prevent losses for growers and provide a continual supply of fresh dandelion for consumers.
Technical Abstract: A bacterial pathogen was isolated from leaf spots on Italian dandelion (Cichorium intybus) from Monterey County beginning in 2002. Koch's postulates were completed on Italian Dandelion demonstrating that the isolated organisms is the pathogen causing the disease. The pathogen was characterized and shown to belong to LOPAT group 1 indicating that it is a member of Pseudomonas syringae. Additionally, amplification of repetitive bacterial sequences (rep-PCR) demonstrated that wll Italian dandelion strains had the same rep-PCR fingerprint, which differed from fingerprints of P. syringae pv. tagetis and P. syringae pv. tabaci which have previously been reported to cause disease on this host. This is the first report of bacterial leaf spot of commercially grown Italian dandelion in California caused by a P. syringae pathovar.