33 isolates of Fusarium oxysporum were obtained from wilted lentil plants collected from different lentil growing areas in Northern and Razavi Khorasan proviences. Pathogenecity tests were performed for all isolates on the susceptible lines. Results indicated that 27 isolates were pathogenic. Then formae special were carried out on different plants and pathogenic isolates were determined as Fusarium oxsporum f. sp. Lentis. The amount of genetic variation was evaluated by polymerase chain reaction (PCR) amplification with a set of 14 RAPD primer and IGS primer pairs. Genetic similarities between each of the isolates was calculated by using the Dice similarity coefficient and cluster analysis was used to generate a dendrogram showing relationship between them. Results obtained indicate that there is no apparent correlation with geographic origin and pathogenecity score of the isolates.

Keywords