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Histochemical Studies of Yellow Poplar Infected with Fusarium solani. J. D. Arnett, Assistant Professor of Plant Pathology, Clemson University Extension Service, Box 631, Florence, South Carolina 29501; W. Witcher, Professor of Plant Pathology, Department of Plant Pathology and Physiology, Clemson University, Clemson, South Carolina 29631. Phytopathology 64:414-418. Accepted for publication 17 October 1973. DOI: 10.1094/Phyto-64-414.

Canker development initiated by Fusarium solani was studied histochemically on 1-yr-old yellow poplar stems 2 to 84 days, 365 days, and 547 days after inoculation. The pathogen did not degrade lignin, but did degrade pectin and cellulose to a limited extent, and completely degraded stored starch in infected areas of the stems. Cessation of lateral growth of the fungus was associated with lignification of a surrounding barrier of cells in the cortex, phloem, and rays of the bark. In the presence or absence of the pathogen, a dark-brown pigment (presumably an oxidized, conjugated phenolic compound) was produced in cells adjacent to wounds. Cankers produced by the pathogen on stems inoculated in the fall or spring were healing 18 mo after inoculation; however, the pathogen could be isolated from the tissues beneath those healing cankers.