Variation within Pseudomonas syringae pv. philadelphi, the cause of a leaf spot of Philadelphus spp.

R oberts , S.J. 1985. Variation within Pseudomonas syringae pv. philadelphi , the cause of a leaf spot of Philadelphius spp. Journal of Applied Bacteriology 59 , 283–290
In pathogenicity tests on Philadelphus and other plant species, belonging to ten genera in seven families, isolates of Pseudomonas syringae from leaf spots on Philadelphus spp. in England did not produce symptoms on any plants other than Philadelphus . It is therefore proposed that these isolates should be designated a distinct pathovar of Ps. syringae with the name Pseudomonas syringae pv. philadelphi . Isolates of this new pathovar varied in their reactions to 6 of 57 biochemical tests. In phage typing tests isolates also varied in their sensitivity to five of seven bacteriophage strains. Four of the six biochemical tests (aesculin hydrolysis, utilization of DL-homoserine L-leucine and sorbitol) and all five of the phages (P11, Pls, P2, A15, and A26) were used to separate the isolates into seven groups. These groups had some relation to their geographical origin, species of Philadelphus from which they were originally isolated, and relative virulence on P. coronarius and P. x purpureo-maculatus . They may represent ecotypes of this new pathovar.