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 willing. 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 but 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 Fe, According to further standard nutritional, biochemical and physiological tests the coriander pathogen belongs to Pseudomonas group la. 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 saticum Animi majus and Levisticum offieinale. 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).
A survey in 1987 and 1988 revealed that basal glume rot, caused by Pseudomonas syringae pv. atrofaciens, occurred nearly everywhere in FRG. The symptoms of the disease usually consisted of water‐soaked dark green to brown lesions on unripe wheat heads, mainly at the basal end of the glumes, which later became dark brown. Forty‐six isolates of P.s. atrofaciens were obtained from glumes, seeds and leaves of wheat and barley. For a fast identification of the isolated bacteria, a bio‐assay was developed. Four to five‐day‐old wheat seedlings, grown on wet filter paper in Petri dishes, were pricked at two‐three sites with a dissecting needle contaminated with bacteria. After 2–3 days, pathogenic isolates induced brown to black spots. The bacterial isolates from wheat inhibited the growth of several fungi grown on potato dextrose agar. In contrast, an authentic isolate of P.s. syringae obtained from wheat showed no inhibitory effect. During screening for resistance, several cultivars of spring and winter wheat were tested in the greenhouse and/or field tests. The results revealed marked differences in the susceptibility of different cultivars.
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