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A Selective Medium for Isolating Verticillium albo-atrum from Soil. A. A. Christen, Research associate, Department of Plant Pathology, Washington State University, Irrigated Agriculture Research and Extension Center, Prosser 99350; Phytopathology 72:47-49. Accepted for publication 29 April 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-47.

A defined, selective medium was developed for direct enumeration of Verticillium albo-atrum (dark mycelia type) propagules from soil and other substrates. The medium was modified from Komada’s selective medium for Fusarium oxysporum and consisted of the following chemicals (per liter): l-sorbose, 2 g; l-asparagine, 2 g; K2HPO4, 1 g; KCl, 0.5 g; MgSO4·7H2O, 0.5 g; Fe-Na-EDTA, 0.01 g; pentachloronitrobenzene (75% a.i.), 1 g; oxgall, 0.5 g; NaB4O7·10H2O, 1 g; streptomycin sulfate, 0.3 g; and the pH was adjusted to 5.7. Colonies of V. albo-atrum were more discrete and morphologically distinctive on this medium compared to other selective media. The recovery of propagules of V. albo-atrum from infested soil was significantly greater (P = 0.05) on this medium (68 × 103 propagules per gram of soil) than on a soil-extract agar or ethanol-streptomycin-penicillin agar (58 × 103 and 51 × 103 propagules per gram of soil, respectively).