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Ecology and Epidemiology

Comparative Pathogenicity and Host Ranges of Fusarium oxysporum Isolates Causing Crown and Root Rot of Greenhouse and Field-Grown Tomatoes in North America and Japan. Randall C. Rowe, Associate professor, Department of Plant Pathology, Ohio Agricultural Research and Development Center, Wooster, 44691 and The Ohio State University, Columbus, 43210; Phytopathology 70:1143-1148. Accepted for publication 15 May 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-1143.

Forty-two isolates of Fusarium oxysporum isolated from crown and root rot-affected tomato plants in 20 locations in North America and Japan were inoculated to four differential tomato lines. The symptoms and pattern of infection on these lines were similar for all isolates tested, and differed from that of F. oxysporum f. sp. lycopersici (Fol) races 1 and 2. Results from inoculation of 15 hosts representing five botanical families indicated that many legumes were moderately susceptible to the crown and root rot isolates tested, while cucurbits, crucifers, and cereals were unaffected. Fol isolates were host specific to tomato. These tests show that isolates of F. oxysporum from crown and root rot-affected tomato plants derived from many areas produce similar symptoms and that the pathogen involved is not a race of Fol, but a new forma specialis of F. oxysporum.