Selective Medium for Isolation of Pectolytic Erwinia sp.. Luellen Pierce, Staff Research Associate, Department of Plant Pathology, 147 Hilgard Hall, University of California, Berkeley 94720. A. H. McCain, Extension Plant Pathologist, Department of Plant Pathology, 147 Hilgard Hall, University of California, Berkeley 94720. Plant Dis. 76:382-384. Accepted for publication 14 November 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0382.

Miller-Schroth medium modified by replacement of most of the agar with sodium polypectate appeared superior to the crystal violet polypectate medium for the selective isolation of pectolytic Erwinia sp. NaOH and MOPS (3-[N-morpholino]propanesulfonic acid) were added to raise the pH and buffer the medium, respectively. Pectolytic erwinias appeared as pink to orange colonies located in deep pits. Nonpectolytic erwinias formed pink-orange colonies with no pits. Pseudomonas spp. either did not grow on the medium or formed green colonies with no pits or pits that were very shallow. Recovery of pectolytic erwinias was significantly greater (P = 0.05) in 19 of 22 pectolytic strains tested with the modified medium than with the crystal violet pectate medium.