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A Semiselective Medium for the Isolation of Pseudomonas syringae pv. savastanoi. G. Surico, Istituto di Patologia e Zoologia forestale e agraria, Universite degli Studi, Facolte di Agraria, 50144 Firenze, Italy; P. Lavermicocca, Istituto tossine e micotossine da parassiti vegetali del CNR, Bari, Italy. Phytopathology 79:185-190. Accepted for publication 2 May 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-185.

A new medium, designated as PVF-1 agar, was developed and tested for isolating Pseudomonas syringae 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 NPC medium of Sands and Rovira. The new medium, a modification of Kado and Heskettes 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 from 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.

Additional keywords: olive knot disease.