Abstract: During the interactions between plant pathogen and host plant，the pathogen secretes effector protein to suppress host defenses. Fusarium wilt is a fungal disease caused by Fusarium oxysporum，the fungus secretes several effector proteins into the plant xylem to promote virulence. These effectors are small molecular cysteine\|rich proteins and called SIX（secreted in xylem）proteins， and the SIX6 was one of them. Fusrium wilt of watermelon was a pathogenic fungus caused by Fusarium oxysporum f. sp.niveurn（Fon）.To understand the function of FonSIX6 during infection，the flanking region of FonSIX6 was cloned and the deletion mutant vector of FonSIX6 with hygromycin was constructed as a selectable marker. The constructed gene deletion vector was transferred into Agrobacterium stain AGL\|1 and then FonSIX6 deletion mutant was obtained by Agrobacterium\|mediated transformation system.

Key words: Fusrium wilt of watermelon, effector protein, FonSIX6, deletion mutant, Fusarium oxysporum f.sp. niveurn