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Etiology

A Reappraisal of the Race Classification of Fusarium oxysporum f. sp. pisi. J. M. Kraft, Research Plant Pathologist, Vegetable Crops Production, Agricultural Research Service, U. S. Department of Agriculture, Prosser, WA 99350; W. A. Haglund, Plant Pathologist, Department of Plant Pathology, Washington State University, Northwestern Washington Research and Extension Unit, Mount Vernon, WA 98273. Phytopathology 68:273-275. Accepted for publication 23 September 1977. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-273.

Based on data collected independently at Mt. Vernon and Prosser, Washington, there appeared to be no valid reason for accepting the recently published race classification scheme for Fusarium oxysporum f. sp. pisi wherein 11 races of the fungus were defined. Our results strongly suggest that the 11-race classification is based more on virulence differences than on true genetic differences in the host, and these same 11 races should be grouped into either race-1 or race-2 types. To minimize the possibility of cultural variants being classified as new races of F. oxysporum f. sp. pisi, the following criteria are suggested: (i) the isolate must be associated with a prevalent wilt disease under field conditions, (ii) the isolate can be distinguished from other known races of F. oxysporum f. sp. pisi by a known gene difference in the host.