Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 9/10/2002
Publication Date: 2/10/2003
Citation: Zhang, W., Sulz, M., Mykitiek, T., Li, X., Yanke, J.L., Kong, H.N., Buyer, J.S., Lydon, J. 2003. Characterization of a bacterial strain from canada that causes white-color disease in canada thistle (cirsium arvense(l.) scop.). Weed Science Society of America Meeting Abstracts. 43:28. Interpretive Summary: .
Technical Abstract: Patches of white-colored Canada thistle (Cirsium arvense (L.) Scop.) plants were recently found on roadsides, pastures, and market gardens in Devon, Mulhurst, Stony Plain, and Edmonton, Alberta, Canada. The diseased plants showed apical chlorosis, sometimes with dark and necrotic leaf spots. These symptoms were also associated with stunted growth, fewer shoots, inhibition of flowering, and/or sterility. A total of 101 bacterial strains were isolated from the leaves, stems, and flowers of white-colored Canada thistle plants. A bacterial species (one strain designated CT99B016C) was consistently isolated from diseased plants and was found to produce similar symptoms on Canada thistle under both greenhouse and field conditions. The organism was reisolated from inoculated, diseased plants, thereby fulfilling Koch's postulates. The disease severity of Canada thistle caused by CT99B016C was not affected by the relative humidity in the air, but was increased by the supplement of dew. The optimal bacterial cell concentration to achieve maximum disease was within the range of 108 ¿ 109 cfu/ml, while the optimal surfactant concentration was 0.15-0.3% Silwet L-77. The CT99B016C strain also caused severe disease of annual and spiny sowthistle (Sonchus oleraceus L. and S. asper (L.) Hill) and dandelion (Taraxacum officinale). The disease severity on these two weed species was even greater than that on Canada thistle. Results of biochemical and nutritional tests and fatty acid analysis clearly placed the CT99B016C strain within the P. syringae group, however, these determinants were not significant enough to separate the P. syringae strains at the pathovar level. Comparison of the 16S-23S rDNA intergenic spacer (ITS) regions of CT99B016C with 16S-23S ITS sequences in the Genbank database indicates that CT99B016C is not a strain of Pseudomonas syringae pv. tagetis, having only 84% homology, but more closely related to Pseudomonas syringae pv. papulans, with 96.3% homology.