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Study of Field-Grown Cotton Roots Infected with Verticillium dahliae Using an Immunoenzymatic Staining Technique. J. S. Gerik, Department of Plant Pathology, University of California, Berkeley 94720, Present address: Sugarbeet Production Unit, Agricultural Research Service, Pacific West Area, U.S. Department of Agriculture, 1636 E. Alisal St., Salinas, CA 93905; O. C. Huisman, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 78:1174-1178. Accepted for publication 7 March 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1174.

Colonization of field-grown cotton roots by Verticillium dahliae was studied by using a specific immunoenzymatic staining technique. Colony density of V. dahliae increased with distance from the root tip, with the maximal density occurring more than 1 cm from the root apex. Colony densities at distances more than 1 cm from the tip were relatively constant. The mean colony length of V. dahliae was 7.3 mm, and increased colony length was correlated with distance from root apices. Hyphae of V. dahliae were present through the entire depth of the cortex, and were greatest in the interior of the root cortex at the surface of the vascular cylinder. The colony appearance was consistent with growth of hyphae from the root surface toward the stele. Hyphae of V. dahliae also were found within numerous cortical cells. Colonies of Fusarium oxysporum, similarly stained, were found to be mostly confined to the root surface and the outer cortex.