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Pathogenic Races of Fusarium oxysporum f. sp. carthami. J. M. Klisiewicz, Pathologist, Crops Research Division, ARS, USDA, University of California, Davis 95616; C. A. Thomas, Pathologist, Crops Research Division, ARS, USDA, Beltsville, Maryland 20705. Phytopathology 60:83-84. Accepted for publication 31 July 1969. DOI: 10.1094/Phyto-60-83.

Two pathogenic races of Fusarium oxysporum f. sp. carthami are distinguished among 13 isolates which are highly virulent on three susceptible safflower varieties. The races are established on the basis of reactions of variety Nebraska 6. Some safflower introductions and the breeding line Nebraska 4051 are highly resistant to the two races.