A semiselective medium for the isolation of Pseudomonas syringae pv. savastanoi.
A new medium, designated PVF-1 agar, was developed and tested for isolating P.s. pv. savastanoi from olive plants under field conditions. It was compared with other conventionally used media, including nutrient-sucrose agar medium (NSA), King's B medium and the Sands and Rovira's NPC medium. The new medium, a modification of Kado and Heskett's D4, allowed growth of P.s. pv. savastanoi, but retained selectivity against saprophytic bacteria. PVF-1 agar contained (in g/litre) sucrose (30), glycerol (10 ml), Difco casamino acids (2.5), dipotassium phosphate trihydrate (1.96), magnesium sulfate heptahydrate (0.4) and sodium dodecyl sulfate (0.4). Of the 32 strs of P. s. pv. savastanoi from different hosts and geographic areas tested, all grew up on PVF-1 agar with variable morphology that paralleled that of the other media. Identification of P.s. pv. savastanoi was mainly accomplished by the production on PVF-1 agar of fluorescent pigments. The mean quantitative recovery for all 32 strs. tested was c. 73%. PVF-1 agar, which inhibited a high percentage (90% or more) of the saprophytic bacteria washed from olive tissues, was successfully used to detect epiphytic populations of P. s. pv. savastanoi on leaves, stems and fruits. Isolation from olive and oleander galls was also enhanced in comparison with other media, including NSA and King's B medium.