Abstract: Abstract: The pathogenicity and AFLP genetic differentiation of 46 Fusarium oxysporum f.sp niveum isolates from Shijiazhuang,Baoding,Tangshan etc. watermelon growing areas and 4 identified races from other regions were analyzed. The result showed that based on the different responses of three common identified hosts, the 50 isolates were classified into 3 physiologic races, 0 (18%)、1 (64%) and 2 (18％) , respectively. Of the total bands, 1157 AFLP bands were amplified by using 21 pairs of primers, among them, 389 ( 33.6%) were polymorphic; when all of polymorphic bands were analyzed by cluster analysis, 50 isolates were classified into3 groups: AGI, which included 5 physiologic race 2 ; AGII, including 4 physiologic race 0; AGIII, 42 isolates, which included 32 physiologic race 1 (76.2％) .It was concluded there existed obvious differentiation of the pathogenicity of Fusarium oxysporum f.sp. niveum in Hebei, and AFLP groups were generally associated with the different races.

Key words: Fusarium oxysporum f.sp. niveum, differentiation of pathogenicity, AFLP analysis