VIEW ARTICLE

Ecology and Epidemiology

Colonization of Muskmelon and Nonsusceptible Crops by Fusarium oxysporum f. sp. melonis and Other Species of Fusarium. T. R. Gordon, Assistant professor, Department of Plant Pathology, University of California, Berkeley 94720; D. Okamoto, and D. J. Jacobson. Staff research associate, and graduate research assistant, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 79:1095-1100. Accepted for publication 5 June 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-1095.

The ability of Fusarium oxysporum f. sp. melonis to colonize roots of a susceptible muskmelon cultivar and six crop species rotated with melons was quantified in the greenhouse and field. Root colonization by F. solani, F. equiseti, and nonpathogenic strains of F. oxysporum also was recorded. Roots of alfalfa, cotton, Honey Dew muskmelon, sugar beet, tomato, and wheat were colonized by F. o. melonis. Crops with comparatively low populations of F. o. melonis on their roots also tended to have low populations of other Fusarium spp. The relative abundance of the four fungi was similar on all seven crops; nonpathogenic strains of F. oxysporum were isolated most frequently, followed by F. o. melonis. F. equiseti was the least frequently isolated of the four fungi in greenhouse experiments, whereas F. solani was the least frequently isolated in the field. Differences in colonization frequencies among these fungi were not proportional to differences in their respective population densities in soil. Nonpathogenic strains of F. oxysporum had the highest colonization frequency per colony-forming unit per gram of soil.