We have purified from potato tubers, the lectin STA devoid of chitinase activity and two chitinases devoid of lectin activity. Both enzymes are 16 kDa glycoproteins, and probably belong to a new family of plant chitinases. The respective antifungal properties of lectin and chitinases were studied by following their effects against early developmental stages of Fusarium oxysporum, a fungal potato pathogen. Here we demonstrate that: (1) lectin does not inhibit mycelial growth but irreversibly inhibits conidia germination and alters the germ tubes; and (2) chitinases block mycelial growth as well as conidia germination and lyse germ tubes.