Pseudomonas syringae pv coriandricola, incitant of bacterial umbel blight and seed decay of coriander (Coriandrum sativum L) in Germany

Since 1987 a devastating disease has occurred in coriander in Germany, characterized by dark-brown discoloration of blossoms and umbels, water-soaked and brown spots on leaves and stems, seed decay and wilting. Infected tissue always contained large quantities of Gramnegative, rod-shaped, motile bacteria with few polar flagella. Tests for LOPAT reactions showed the bacteria to be positive for levan-production and tobacco hypersensitivity reaction bur negative for oxidase reaction, rot of potato slices and arginine dihydrolase. The bacteria failed to produce fluorescent pigment on King's medium B but revealed a blue fluorescence after growing in a liquid medium without Fe2+. According to further standard nutritional, biochemical and physiological tests the coriander pathogen belongs to Pseudomonas group Ta, i.e. Pseudomonas syringae. Also, the fatty acid composition revealed a very close similarity to Pseuodomonas syringae. On Biolog plates the coriander strains showed a uniform metabolic pattern and could clearly be distinguished from other Pseudomonas syringae pathovars. Typical hosts of Pseudomonas syringae pv. syringae were not infected by the coriander pathogen. Also, most tested umbelliferae species reacted resistant towards the pathogen. Typical disease symptoms, such as persistent water-soaked lesions, were incited only a Coriandrum sativum, Ammi majus and Levisticum officinale. The studies revealed that the pathogen described is a separate pathovar of Pseudomonas syringae not included in the approved list of P. syringae pathovars. The name Pseudomonas syringae pv. coriandricola is proposed. Strain GSPB 1965 has been deposited in the NCPPB as pathotype strain (no. 3781).