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Ecology and Epidemiology

Wound-Related Modifications of Penetration, Development, and Root Rot by Fusarium roseum in Forage Legumes. J. C. Stutz, Graduate assistant, Department of Plant Pathology, The Pennsylvania State University, University Park 16802, Present address: Assistant professor, Division of Agriculture, Arizona State University, Tempe 85287; K. T. Leath(2), and W. A. Kendall(3). (2)(3)Adjunct professor, Department of Plant Pathology, and adjunct professor, Department of Agronomy, respectively, The Pennsylvania State University, University Park 16802, also research plant pathologist and research plant physiologist, respectively, USDA-ARS. Phytopathology 75:920-924. Accepted for publication 20 March 1985. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1985. DOI: 10.1094/Phyto-75-920.

The role of wounding in root rot of forage legumes was examined by using two closely related fungi that differ in virulence and three forage legumes that differ in susceptibility. Plants of alfalfa, red clover, and crown vetch were grown either in conventional or in gnotobiotic slant-board nutrient solution culture. Unwounded or scalpel-wounded roots were inoculated at restricted sites with isolates of Fusarium roseum 'Acuminatum' and F. roseum 'Avenaceum.' Wounding increased the incidence and severity of root rot caused by both fungi and accelerated penetration and colonization of the roots in the three species that were examined. All fungi penetrated epidermal cells in close proximity to the wound; only rarely were hyphae observed entering the wound directly. In addition, wounding altered the type of growth of F. roseum 'Acuminatum' in the root cortex by enhancing the formation of distributive hyphae and eliminating the formation of chlamydospores which occurred in unwounded roots. The primary role of wounding was not to provide a breach of the root surface, but to alter the host-pathogen interaction to favor fungal development in the root.