|Koike, Steven -|
|Bolda, Mark -|
Submitted to: Plant Disease
Publication Type: Research Notes
Publication Acceptance Date: April 7, 2014
Publication Date: August 1, 2014
Citation: Koike, S.T., Bolda, M.P., Bull, C.T. 2014. Pseudomonas blight caused by Pseudomonas syringae on raspberry in California. Plant Disease. DOI: 10.1094/PDIS-01-14-0041-PDN. Interpretive Summary: Raspberry is ranked as the third most popular berry in the United States for fresh consumption. Santa Cruz County in central coastal California produces a 132 million dollar crop. Plant pathogens can limit the supply of this highly sought after berry. The first step in reducing the impact of emerging plant diseases on crops is to identify the pathogen causing the disease. In this study, a disease not previously described on raspberry in central coastal California was described and the bacterial pathogen causing the disease was isolated and studied. It appears that the pathogen causing bacterial blight on raspberry is different than previously described pathogens. This information will help producers make crop production choices to help reduce spread of the pathogen from one susceptible crop to another can use this information.
Technical Abstract: Plantings of red raspberry (Rubus idaeus var. strigosus) exhibited symptoms of a previously undocumented disease. Lesions were observable from both adaxial and abaxial leaf surfaces. As disease progressed, lesions enlarged and coalesced, resulting in significant dark brown to black blighting of the foliage. The foliage of severely affected plants was stunted and wilted. Four isolates were Gram negative according to lysis by KOH and were fluorescent. The isolates were positive for levan formation and negative for oxidase and arginine dihydrolase. The isolates did not cause soft rot on potato slices but did induce a hypersensitive reaction in tobacco (Nicotiana tabacum L. cv. Samsun) and thus, belonged to Lelliot’s LOPAT group 1, P. syringae. Based on colony morphology and molecular information, the isolates were identified as Pseudomonas syringae. All four isolates had identical DNA fragment-banding patterns generated by repetitive extragenic palindromic sequence polymerase chain reaction (rep-PCR) using the BOXA1R primer. The pattern generated was different than all P. syringae pathovars in genomospecies 1 including P. syringae pv. syringae. According to multilocus sequence analysis the strains are most closely related to P. syringae pv. aceris and P. syringae pv. solidagae in genomospecies 1. Pathogenicity experiments demonstrated that these isolates caused symptoms similar to those observed in the field. To our knowledge, this is the first report of Pseudomonas blight of raspberry, caused by P. syringae, in California.