VIEW ARTICLE

A Selective Medium for the Quantitative Determination of Rhizoctonia solani in Soil. Wen- hsiung Ko, Assistant Professor, Department of Plant Pathology, University of Hawaii, Hawaii Agricultural Experiment Station, Hilo, 96720; Frances K. Hora, Technician, Department of Plant Pathology, University of Hawaii, Hawaii Agricultural Experiment Station, Hilo, 96720. Phytopathology 61:707-710. Accepted for publication 25 January 1971. DOI: 10.1094/Phyto-61-707.

An agar medium containing minerals, Dexon, chloramphenicol, streptomycin, and gallic acid and sodium nitrite as selective carbon and nitrogen sources suppresses the development of undesired microorganisms and enhances the growth of Rhizoctonia solani from soil. Ninety to 100% recovery of R. solani from soil inoculated with sclerotia was obtained with this selective-medium method. The population of R. solani in naturally infested soils as determined by this method ranged from 1-9 propagules/10 g dried soil. Low population of R. solani in soil appears to be the main reason why the soil-dilution-plate method is inadequate for determining populations of this fungus. Sensitiveness, simplicity, and quickness are the important advantages of this method.