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Ecology and Epidemiology

Inoculum Potential of Macrophomina phaseolina. G. E. Short, Former Postdoctoral Fellow, Department of Plant Pathology, University of Missouri-Columbia, Columbia, MO 65201; T. D. Wyllie, Professor, Department of Plant Pathology, University of Missouri-Columbia, Columbia, MO 65201. Phytopathology 68:742-746. Accepted for publication 14 October 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-742.

Sodium hypochlorite was used to dissolve the melanin-like cementing agent that engulfs sclerotial cells of Macrophomina phaseolina. Then sclerotia were 'squashed' to enable enumeration of cells of the propagules. The number of cells per sclerotium was directly related to size of sclerotia; and sclerotium size appeared to depend on the available nutrients of the substrate on which the propagules were produced. Large sclerotia produced considerably more germ tubes than did small sclerotia when germinated on culture media. Sclerotia of M. phaseolina were sensitive to soil fungistasis; but in the spermosphere of soybean, sclerotia germinated within 2-3 mm of the seed surface and produced one to seven germ tubes per germinated sclerotium.

Additional keywords: charcoal rot, decolorized sclerotia.