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Biology of Macrophomina phaseoli in Soil Studied with Selective Media. W. A. Meyer, Graduate Research Assistant, Department of Plant Pathology, University of Illinois, Urbana 61801; J. B. Sinclair(2), and M. N. Khare(3). (2)Professor, Department of Plant Pathology, University of Illinois, Urbana 61801; (3)Associate Professor, Department of Plant Pathology, J. Nehru Agricultural University, Jabalpur, M. P., India. Phytopathology 63:613-620. Accepted for publication 30 November 1972. DOI: 10.1094/Phyto-63-613.

Two selective media using rice agar as the basal medium, were developed for the isolation and enumeration of Macrophomina phaseoli from soil and soybean plant debris. The first, designated as CC, was developed in India and contained chloroneb, methoxyethylmercury chloride (Ceresan Wet), streptomycin sulfate, and potassium penicillin. The second, designated as CMR, was developed at the University of Illinois and contained the same ingredients, except that mercuric chloride was substituted for methoxyethylmercury chloride and rose bengal was added. Recovery of M. phaseoli from artificially infested soil was close to 100% with either medium. Assays with CC showed M. phaseoli persists in soil under diverse environmental conditions and that populations of the fungus in soil, increased with increased years of continuous soybean cropping. Populations of M. phaseoli in soil from Illinois soybean and corn fields, determined with CMR, were higher than those determined using the sclerotial-flotation method. In the absence of a suitable host, M. phaseoli populations increased and mycelial inoculum persisted in soil up to 7 days. The test fungus was capable of invading dead stem tissues in soil containing antagonistic microorganisms. The evidence does not support the strict classification of M. phaseoli as a root-inhabiting fungus.