VIEW ARTICLE

Ecology and Epidemiology

Colonization of Field-Grown Cotton Roots by Pathogenic and Saprophytic Soilborne Fungi. O. C. Huisman, Associate professor, Department of Plant Pathology, University of California, Berkeley 94720; Phytopathology 78:716-722. Accepted for publication 8 December 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-716.

Colonization of roots of field-grown cotton plants by several fungi (Verticillium dahliae, V. tricorpus, Gliocladium sp., Trichoderma spp., Rhizoctonia spp., Pythium ultimum, P. aphanidermatum, and an unidentified Pythium sp.) was examined by plating washed roots on a growth restrictive medium. Most colonies were localized on the roots and apparently were associated with the rhizoplane or the outer cortex. With the exception of Pythium spp., which colonized roots only during periods of high soil moisture, colonies per centimeter of root were constant throughout the season. Colonization of roots of several other plants by Verticillium spp. was found to be similar to that observed with cotton. Colony densities on roots per unit of inoculum density in soil were fairly similar for most of the fungi. The one exception was Rhizoctonia, for which a comparatively much higher value was observed. Colony densities for the Pythium species and for Rhizoctonia were higher on roots with severe tissue damage than on roots exhibiting little or no damage. For the other fungi, colonies were equally abundant on roots with or without tissue damage.