In this research, eleven isolates of Fusarium oxysporum were collected from tomato plants displaying will symptoms in fields in Kurdistan province. Race 1 of pathogen was obtained from Moscow Timiryauv Agricultural Academy in Russia. PathogenicitY of the collected isolates and mce l of the pathogen were evaluated in glasshouse conditions. Pathogenicity tests and race determination were conducted using root-dip inoculation with different tomato cultivars, Betiy naliv-241 (not resistant), Blugovest (resistant to ruce l) and Benito (resistant to both ruces of 1 and 2). The experimental design was a completely randomized type with six replications (pots) containing two seedlings per pot. Disease severity was measured five weeks following inoculation by using a scale of 0 to 4. The criteria used to assess the re."'ponse of different culti.vars were; leaf disease index.. plant height and vascular discoloration index. Results showed that Beliy naliv-24llacldng any resistance gene wilted four wooks after inoculation, but cultivars Blagovest and Benito did not develop symptoms to any of the isolates tested. The reaction of race I and the Irunian isolates were similar in pathogenicity suggesting that all oftbe isolates belong to Fusarium f. sp.lycopersicl race l. Also, Reaction 23 tomato cultivars against to F. o. f. sp. lycopersici indicated that 6 of the them were resislant. 5 were intennediately resistant. 6 were tolerant, 3 were susceptible and the rest 3 were found to he very ~usceptible.
