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A Selective Medium for the Enumeration and Isolation of Phoma betae from Soil and Seed. W. M. Bugbee, Research Plant Pathologist, Agricultural Research Service, United States Department of Agriculture, and Associate Professor, Department of Plant Pathology, North Dakota State University, Fargo 58102; Phytopathology 64:706-708. Accepted for publication 7 December 1973. DOI: 10.1094/Phyto-64-706.

A selective medium developed for the enumeration and isolation of Phoma betae from soil and seed consisted of: 4 g K2HPO4 ;1.5 g KH2PO4 ; 25 ml soil extract; 200 mg boric acid; 100 mg each of streptomycin sulfate, chlorotetracycline, and benomyl; 10 g sucrose; and 17 g agar in 1,000 ml distilled water, adjusted to pH 7.0 with HCl before autoclaving. Sucrose and the antibiotics were added to the molten agar (50 C) after autoclaving. Phoma betae was characterized by the production of small, dark hyphal masses resembling microsclerotia on the underside of the culture in contact with the petri dish. The medium was used to enumerate P. betae in field soils that had been cropped to sugar beets for five consecutive years, in soil from commercial root storage sites, and in assaying seed samples.

Additional keywords: sugar beet storage rot, soil microbiology.