A Semiselective Medium for the Isolation ofPseudomonas syringaepv.savastanoi

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Abstract
A new medium, designated as PVF-1 agar, was developed and tested for isolating Pseudomonas syringae pv. savastanoi from olive [Olea europaea L.] plants under field conditions. It was compared with other conventionally used media, including nutrient-sucrose agar medium (NSA), King''s B medium, and the NPC medium of Sands and Rovira. the new medium, a modification of Kado and Heskett''s D4, allowed growth of P. s. savastanoi, but retained its selectivity against saprophytic bacteria. PVF-1 agar contained (in grams per liter) 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 strains of P. s. savastanoi form different hosts and geographic areas that were tested, all grew up on PVF-1 agar with variable morphology that paralleled that of the other media. Identification of P. s. savastanoi was mainly accomplished by the production on PVF-1 agar of fluorescent pigments. The mean quantitative recovery for all 32 strains tested was approximately 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. savastanoi on leaves, stems, and fruits. Isolation from olive and oleander galls was also enhanced in comparison to usual media, including NSA and King''s B medium.