Twenty one Fusarium spp. isolates, collected from potato tubers showing typical dry rot symptoms, taken from three regions in Egypt, were found to belonging to four species, i.e. F. sambucinum, F. solani, F. oxysporum and F. culmorum. The pathogenic ability of these isolates on healthy potato tubers (cv. Spunta) revealed that 17 ones were pathogenic and 4 were non-pathogenic. The most aggressive isolate of each Fusarium species was chosen for further studies. Host range studies revealed that carrot is not susceptible for infection; meanwhile taro, eggplant and sweet potato were susceptible for infection by Fusarium spp. Eight potato cultivars were evaluated for their reaction to dry rot disease infection. Obtained results showed significant differences among tested cultivars. Valor cultivar recorded the highest level of resistance; meanwhile cv. Galactica was the most susceptible one. The rest of tested cultivars showed different levels of susceptibility. The enzymatic activity in two potato cultivars, i.e. Galactica and Valor, as a response to dry rot infection, showed increments in peroxidase, polyphenol oxidase and phenylalanine ammonia lyase in the resistant cultivar (Valor) compared with the susceptible one (Galactica). These measurements could explain resistance and susceptibility in tested potato cultivars.