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Characterization of Pathogenic Races of Fusarium oxysporum f. sp. melonis Causing Fusarium Wilt of Melon in New York

June 1997 , Volume 81 , Number  6
Pages  592 - 596

T. L. Zuniga , Graduate Research Assistant , and T. A. Zitter , Professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853 ; T. R. Gordon , Associate Professor , D. T. Schroeder , Graduate Research Assistant , and D. Okamoto , Staff Research Associate, Department of Environmental Science Policy and Management, University of California, Berkeley 94720



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Accepted for publication 14 February 1997.
ABSTRACT

Forty-six isolates of Fusarium oxysporum f. sp. melonis obtained from soil samples throughout melon-producing areas in New York State were identified on the basis of pathogenicity and colony morphology. Physiological races 1 and 2 were identified by their reaction on a set of differential melon cultivars. Race 1 was widely distributed, occurring in six of the seven New York counties surveyed. Twenty-seven of the 28 race 1 isolates were associated with vegetative compatibility group (VCG) 0134, whereas one was incompatible with all known VCGs of F. oxysporum f. sp. melonis. Twelve out of 18 race 2 isolates were associated with VCG 0131, and occurred in four counties in eastern and western New York. Five isolates of race 2, associated with VCG 0130, were recovered from a farm in Washington County, as was a single race 2 isolate which was incompatible with all known VCGs of F. oxysporum f. sp. melonis. Restriction fragment length polymorphisms in the nuclear DNA revealed variability among the isolates examined, but race 1/VCG 0134 isolates from New York and Maryland were identical or nearly so, as were race 2/VCG 0131 isolates from the two states. These findings suggest a close relationship between the populations of F. oxysporum f. sp. melonis in New York and Maryland. Race 2 isolates were more virulent than race 1 isolates, based on the number of days to first symptoms and death of melon seedlings.


Additional keywords: cantaloupe, Cucumis melo, muskmelon

© 1997 The American Phytopathological Society